Table of Content

15 January 2021, Volume 32 Issue 1

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Opinion of the Editor-in-Chief

Discussion on the scientific concept of ecology and its evolution and the contemporary ecologi-cal discipline system

YU Gui-rui, WANG Qiu-feng, YANG Meng, CHEN Zhi

2021, 32(1):  1-15.  doi:10.13287/j.1001-9332.202101.040

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Ecology is not only a branch of biology, but also an important part of environmental science and earth system science. The results of ecological studies can be directly applied in biodiversity conservation of plant, animal and microbe, biological resource utilization and biological industry management, and other fields. The concept of ecosystem extends classic ecology or basic ecology research to a new stage of ecosystem ecology or ecosystem science, which has laid a theoretical foundation for the scientific research of ecological environment at the global and continental scales, and has promoted the integration of biology, geography, and environmental science, and cross disciplinary of the natural sciences, humanities, and social economic sciences. During the integration processes, together with constantly absorbing nutrition from different disciplines, researches of eco-logy put forward a lot of scientific concepts or theories, and have been applied and developed in the relevant scientific research, formed contemporary ecology and ecosystem science system centered on the cognition of ecosystem, resource environment, and the mutual feedback relation with human society. We comprehensively discussed the scientific concept, basic theory, and discipline system of contemporary ecology from the origin and development of ecological thought, the scientific connotation, and extension of ecological concept, etc., and tried to sort out, investigate, and analyze the scientific connotation, discipline category and discipline system of contemporary ecology, put forward the branch discipline system classification scheme of basic ecology and applied ecology, with the aim to provide references for perfecting and reconstructing the discipline system of contemporary ecology.

Original Articles

Characteristics of phosphorus fractions and their driving factors in forest soils with different parent materials in the mid-subtropics, China

XIAO Hua-cui, LI Jing-wen, XIA Yun, YANG Liu-ming, LIN Yan-yu, FAN Yue-xin

2021, 32(1):  16-22.  doi:10.13287/j.1001-9332.202101.001

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With the aim to understand the influence degree and mechanism of parent material and forest type on soil phosphorus component, we analyzed soil P fractions, iron and aluminum oxides, microbial biomass, and phosphatase activity in Castanopsis carlesii and Cunninghamia lanceolata forest soils developed from two types of parent materials, sandstone and granite, in Sanming, Fujian Province. The results showed that both parent material and forest type significantly affected the contents of different P fractions. The contents of total P, labile inorganic/organic P, moderately labile inorganic/organic P, and non-labile P from sandstone-developed soils were significantly higher than those from granite-developed soils. Moreover, soil labile organic P, moderately labile inorganic/organic P and non-labile P fraction in sandstone-developed soils of C. carlesii forest were significantly higher than those of C. lanceolata forest, while the corresponding soil P fractions in granite-deve-loped soils had no significant difference between the two types of forests. The activity of acid phosphatase (ACP) in granite-developed soils was significantly higher than that in sandstone-developed soils under two types of forest, while soil microbial biomass carbon (MBC) and P (MBP) in sandstone-developed soils were significantly higher under C. carlesii forest than under C. lanceolata fo-rest. The content of soil P fractions was significantly positively correlated with the content of different forms of iron and aluminum oxides, MBP, and MBC, but negatively correlated with soil pH and acid phosphatase activity (ACP). Our results indicated that parent material and forest types might affect soil P fractions and characteristics mainly through altering soil iron and aluminum oxides, ACP, MBP in mid-subtropical forest soils.

Response of nutrient release and ecological stoichiometry of litter to simulated nitrogen deposition in evergreen broad-leaved forest in central Yunnan, China

ZHENG Xing-rui, SONG Ya-li, WANG Ke-qin, ZHANG Yu-jian, PAN Yu

2021, 32(1):  23-30.  doi:10.13287/j.1001-9332.202101.006

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We examined nutrient release and ecological stoichiometric characteristics of litters under N deposition in an evergreen broadleaved forest in Mopan Mountain in central Yunnan. Nylon net bag method was used for in situ decomposition of leaf litter and twig litter. There were four treatments, including control (CK, 0 g N·m^-2·a^-1), low nitrogen (LN, 5 g N·m^-2·a^-1), medium nitrogen (MN, 15 g N·m^-2·a^-1), and high nitrogen (HN, 30 g N·m^-2·a^-1). The results showed that after one year of N addition, the contents of C and N in leaf litter, twig litter and soil increased gradually with the increases of N addition rates, with increases of 0.3%-8.2% and 4.9%-69.0%, respectively. C/N gradually decreased with increasing N addition rates, with a decrease of 0.8%-37.8%. There was no significant difference in P content, C/P and N/P of twig litter under different treatments. Treatment duration and N application rate significantly affected the N and P contents and stoichiometric ratios of leaf litter, twig litter and soil. During the 1-year decomposition process, the residual rates of C, N and P in litters were successively in the modes of release, leaching-enriched-released and leaching-enriched. Exogenous N addition significantly inhibited the release process of C, N and P in litter. The contents of C and P in soil were significantly positively correlated with the contents of N and P in litter, while the contents of N in soil were significantly positively correlated with the contents of C and N in litter. There was a significant correlation of stoichiometric characteristics between litter and soils of evergreen broadleaved forest under N deposition. Our results were helpful to understand the response mechanism of litter decomposition process of forest ecosystem to N deposition.

Effects of root growth on leaf litter decomposition and enzyme activity in litter layer

XU Zi-jun, WAN Xiao-hua, LIANG Yi-fan, SHI Xiu-zhen

2021, 32(1):  31-38.  doi:10.13287/j.1001-9332.202101.003

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The growth of roots towards aboveground litter layer is a common phenomenon in forest ecosystems. It is of great significance to examine the effects of root presence on litter decomposition for understanding nutrient cycling in forest ecosystems. We explored the effects of root growth on leaf litter decomposition, nutrient release and enzyme activities by establishing treatments with and without root with a one year field decomposition experiment in Phoebe zhennan and Castanopsis kawada-mii forests at Sanming, Fujian. The results showed that after 360 days decomposition, leaf litter mass remaining ratio in the treatment with root was 8.4% and 19.7% lower than control, respectively. The presence of root exhibited significant effect on litter decomposition during the 90-180 days. Compared with the control, the remaining ratio of leaf litter carbon, nitrogen and phosphorus were 6.0%, 19.1% and 20.6% lower in the treatment with root in the P. zhennan forest, and were 21.3%, 23.2% and 20.5% lower in the C. kawadamii forest, respectively. During the whole decomposition process, root presence did not affect the hydrolytic enzyme activity. After 180 days decomposition, the peroxidase activities in the treatment with root were 111.4% and 92.4% higher than control in the P. zhennan and C. kawadamii forests, respectively. The remaining ratio of leaf litter carbon, nitrogen and phosphorus were negatively correlated with the activities of cellobiohydrolase, β-glucosidase, acid phosphatase, and peroxidase. Root presence in litter layer could accelerate litter decomposition and nutrient release through nutrient uptake and stimulation of oxidase activity.

Effects of water and nitrogen stress on water utilization of dominant species in broadleaved Korean pine forest in Changbai Mountain, China

ZHAO Song-shi, LIN Mao-sen, WANG An-zhi, YANG Guo-fan, YUAN Feng-hui, GUAN De-xin

2021, 32(1):  39-45.  doi:10.13287/j.1001-9332.202101.030

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The aggravation of global nitrogen deposition may change plant water utilization and affect plant growth. Understanding the changes of vegetation water consumption under nitrogen deposition is of great significance for simulating and predicting the evolution of each component of forest hydrological cycle. We used the hydrogen and oxygen isotope tracer method to analyze water consumption source, quantity and law of Quercus mongolica (Qm), Fraxinus manshurica (Fm) and Tilia amurensis (Ta), the dominant species in broadleaved Korean pine forest of Changbai Mountain, under different add amounts of nitrogen [low nitrogen addition group (11.8 kg·hm^-2·a^-1), L_N; high nitrogen addition group (23.6 kg·hm^-2· a^-1), H_N] and different amounts of simulated precipitation (water addition amount were 0, 400, 800 and 1600 mL, equivalent to single rainfall amount were 0, 16, 32 and 64 mm, respectively). The results showed that under the condition of relative drought, soil water utilization ratio of Qm, Fm and Ta in the L_N group were 26%, 12% and 20%, higher than that in H_N group. When the amount of simulated precipitation was 16 mm, soil water utilization ratio of Qm, Fm and Ta in L_N group reached the highest, being 73%, 70% and 43%, respectively. This ratio also reached a high value in H_N group, but being less than the values in L_N group. When the amount of simulated precipitation was 32 mm, soil water content approximated the average value in broadleaved Korean pine forest in the growing season in Changbai Mountain. The average soil water utilization ratio of test tree species in H_N group was 39%, higher than that in L_N group (16%). When the amount of simulated precipitation reached 64 mm, the soil water was saturation. Soil water utilization ratio of Qm, Fm and Ta in L_N group was 14%, 5% and 1%, which was lower than that in H_N group, the corresponding ratio were 64%, 13% and 10%, respectively. In conclusion, under the condition of less precipitation and relatively dry soil, the soil water utilization ratio of those three tree species were lower, and the increases of nitrogen availability further reduced the ratio. When the amount of precipitation was high and soil moisture was higher than the average value of the growing season, soil water utilization ratio of those tree species was higher. With the increases of soil nitrogen availability, this ratio was further increased.

Response of radial growth of Pinus sylvestriformis and Picea jezoensis to climate warming in the ecotone of Changbai Mountain, Northeast China

YU Jian, CHEN Jia-jia, MENG Sheng-wang, ZHOU Hua, ZHOU Guang, GAO Lu-shuang, WANG Yong-ping, LIU Qi-jing

2021, 32(1):  46-56.  doi:10.13287/j.1001-9332.202101.004

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Changbai Mountain is a typical distribution area of temperate coniferous and broad-leaved mixed forests, with significant influence of global climate change. In order to understand the responses of forest ecosystem to climate change, we examined the responses of dominant arbor species in the community ecotone of broad-leaved Korean pine forest and spruce-fir forest (also known as dark coniferous forest), Pinus sylvestriformis and Picea jezoensis. The standard chronologies were established by obtaining tree ring width data in order to identity the key climatic factors that confine the radial growth of both species. The responses of P. sylvestriformis and P. jezoensis to climate factors were different.P. sylvestriformis was more sensitive than P. jezoensis, indicating that P. sylvestriformis was more suitable for dendroclimatological analysis. The radial growth of P. sylvestriformis was consistent with the increases of mean temperature, while the radial growth of P. jezoensis showed a “divergence problem” which decreased with the increases of mean temperature. The radial growth of P. sylvestriformis was mainly limited by temperature, especially the mean temperature in last July and August and current September. However, there was a negative correlation between standard chronologies of P. jezoensis and mean temperature in most months, which was limited by both temperature and precipitation. The correlation between radial growth of both species and climate factors after sudden temperature rise, was weaker than that before sudden temperature rise. The correlation between radial growth and climate factors changed from positive to negative in some months. Current temperature rise might not exceed the critical threshold of the radial growth of P. sylvestriformis, which could promote the radial growth. In addition, the wavelet analysis showed that the radial growth of trees in this area might be affected by large-scale coupling effects of atmospheric-ocean-land changes. In conclusion, climate warming was beneficial to the radial growth of P. sylvestriformis, while drought stress caused by warming was the main factor limiting the radial growth of P. jezoensis. If the global temperature continues to increase in the future, it will have an adverse impact on P. jezoensis. The results would help improve our understanding of the responses of radial growth of P. sylvestriformis and P. jezoensis to future climate change, and provide some basic data for climate reconstruction using both species.

Effects of leaf extracts of Amorpha fruticosa on seed germination and seedling growth of Amygdalus pedunculata

WANG Xiu-qing, WANG Jin-xin, MA Xu, ZHANG Yu-yu, WANG Huai-biao, WANG Yu-bao, DI Long

2021, 32(1):  57-65.  doi:10.13287/j.1001-9332.202101.008

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Amorpha fruticosa and Amygdalus pedunculata are common plant species used for greening construction in arid and semi-arid region of Northwest China. In order to explore the feasibility of greening construction and ecological restoration by A. fruticose with A. pedunculata, we exami-ned the allelopathic effects of five concentrations of aqueous leaf extracts of A. fruticosa (0.025, 0.05, 0.10, 0.15 and 0.20 g·mL^-1) on eight A. pedunculata varieties (YY₁, YY₃, YY₄, YY₅, YY₆, SM₆, SM₇ and SM₈), using the methods of paper-petri dish and soilless culture. The results showed that when the concentration of A. fruticosa leaf extracts were 0.025 and 0.05 g·mL^-1, the seed germination and seedling growth of YY₁ and SM₆ were significantly better than other varieties. With increasing concentration of A. fruticosa leaf extracts, the catalase activity of A. pedunculata seedlings first increased and then decreased. The activities of peroxidase and superoxide dismutase, and the contents of soluble protein and chlorophyll showed a downward trend, while the contents of malondialdehyde and soluble sugar and the permeability of cell membrane gradually increased. Results of the principal component and cluster analysis showed that the growth potential of A. pedunculata decreased with the order of YY₁, SM₆, SM₈, SM₇, YY₆, YY₃, YY₅ and YY₄ under the allelopathic effect of A. fruticose. In conclusion, the artificial collocation and mixed planting of low-density of A. fruticosa with YY₁ and SM₆ were beneficial to seed germination and seedling growth of A. pedunculata.

Effects of neighbors with different sexuality and soil sterilization on biomass of Populus cathayana seedlings

JIANG Hao-tian, HE Heng-guo, XU Xiao, DONG Ting-fa

2021, 32(1):  66-72.  doi:10.13287/j.1001-9332.202101.010

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Although plant-plant interactions have been intensively studied, few studies examined sex-related neighbor interactions in dioecious plant species. Here, we investigated the sexual diffe-rences in biomass accumulation, and analyzed the sexual neighbor effects and yields of sexual combination in Populus cathayana seedlings under the treatments of inter- and intra-sex neighbors and soil sterilization. The results showed that biomass accumulation of P. cathayana decreased in both of sexes when grown with an intra-sex neighbor. Females increased biomass accumulation under non-sterilization condition when grown with an inter-sex neighbor. Soil sterilization decreased biomass accumulation in both sexes of these plants, especially for females. Soil sterilization treatments did not significantly affect intra-sex interactions, but neutralized the positive effects in females and led the effects in males to turn from neutral to negative in inter-sex neighbors. The highest biomass in female-male combination under non-sterilization condition and the lowest biomass in male-male combination under sterilization condition were observed among combinations. These results indicated that the growth of female and male P. cathayana differed in their responses to their sexual neighbors, and that such neighbor effects were affected by soil microorganism. Our results could contribute to improve the productivity of poplar plantations in silviculture.

Effects of drought stress on the stoichiometric characteristics in different organs of three shrub species

CHEN Jia-rui, WANG Guo-liang, MENG Min, WANG Run-chao

2021, 32(1):  73-81.  doi:10.13287/j.1001-9332.202101.002

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In order to explore how water stress affects the stoichiometric characteristics in leaves, stems, very fine roots (0-1 mm), fine roots (1-2 mm) and thick roots (>2 mm) of three shrub species, we studied the effects of three water treatments [(75±5)%, (55±5)% and (35±5)% of field water capacity (FC)] on the stoichiometric characteristics of different organs of Syringa oblata, Rosa xanthina and Forsythia suspensa in a pot experiment. The results showed that there were significant differences in nitrogen (N) and phosphorus (P) contents, C:N, C:P and N:P of the same organ among the three species. With the intensification of drought stress, there was no significant change of C content in all organs of the three species. The N content increased in leaves, but decreased gradually in stems. The N content in very fine roots and fine roots increased first and then decreased. The P content decreased in leaves and stems, while increased first and then decreased in very fine roots and fine roots. Under drought stress, leaf C:N decreased, C:P and N:P of leaf and stem increased. There was the strongest effect of drought stress on the C:N of very fine roots and C:P and N:P of leaves. There was the least effect of drought stress on C:N, N:P of thick roots and C:P of very fine roots. There was no significant correlation between the contents of C, N in soil and the contents of C, N and P in shrub organs, but soil P content was significantly correlated with the contents of C, N and P in leaves and roots. It was concluded that the relative P limitation in soil was the most important factor affecting the stoichiometric characteristics of shrub organs. Drought had different effects on the stoichiometry of different organs in different shrub species. The stoichio-metry of leaves and very fine roots was more sensitive to drought stress than that of other organs. Drought might affect the stoichiometric characteristics especially related to P in different organs of shrubs, mainly by affecting plant absorption of soil P and its distribution in different organs.

Effects of planting broadleaf trees and Moso bamboo on soil carbon mineralization and microbial community structure

FANG Tao, LI Yong-chun, YAO Ze-xiu, LI Yong-fu, WANG Xing-meng, WANG Yue, YU Ye-fei

2021, 32(1):  82-92.  doi:10.13287/j.1001-9332.202101.033

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We conducted a pot experiment to investigate the effects of planting broadleaf tree species (i.e., Cinnamomum camphora, Schima superba, and Quercus glauca) and Moso bamboo (Phyllostachys edulis) on soil carbon mineralization and microbial community structure. The rates of soil carbon mineralization were measured via alkali trapping method. The structural and functional diversity of soil bacterial and fungal communities were analyzed by terminal restriction fragment length polymorphism (T-RFLP) and real-time quantitative PCR techniques. The soil planted with Moso bamboo exhibited a significantly higher carbon mineralization rate and labile carbon content than those in the soils planted with broadleaf tree species. The underground biomass of Moso bamboo was higher than that of broadleaf tree species. The soil bacterial communities were more sensitive than fungal communities to the planting of different plant species . Moreover, soil fungal diversity of Moso bamboo was distinctly different from that of broadleaf tree species. Compared to the diversity of soil bacterial communities, the diversity of soil fungal communities was more closely related with soil pH, organic carbon content, and carbon mineralization. In comparison to the broadleaf tree species, the Moso bamboo planting could substantially increase soil organic carbon minera-lization, which was affected mainly by the soil fungal community structure.

Variation of subtropical forest soil microbial biomass and soil microbial community functional characteristics along an urban-rural gradient

HE Yue, LI Chun-tao, YU Yuan-chun, HE Huang-pan, TAO Xiao

2021, 32(1):  93-102.  doi:10.13287/j.1001-9332.202101.034

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Soil microorganisms, which are sensitive to environmental changes, affect soil nutrient cycling and play an important role in the biogeochemical cycling. To understand the changes of soil microorganisms in subtropical forest across the urban-rural environmental gradient, we analyzed the differences in soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial community functional diversitiy in Dashu Mountain National Forest Park (urban forest), Zipeng Mountain National Forest Park (suburban forest) in Hefei and Wanfo Mountain(rural forest) in Luan City. Results showed that soil MBC followed an order of rural natural forest (115.07 mg·kg^-1) > suburban forest (101.68 mg·kg^-1) > urban forest (82.73 mg·kg^-1), soil MBN followed an order of rural natural forest (57.73 mg·kg^-1) > urban forest (31.57 mg·kg^-1) > suburban forest (29.01 mg·kg^-1), soil microbial metabolic activities (AWCD), McIntosh index (U) were shown as rural natural forest > suburban forest > urban forest. The main carbon sources used by soil microbial communities in those forests were carboxylic acids, amino acids and carbohydrates, with weak utilization capacity for polyamines and polyphenols. The utilization capacity of soil microorganisms to amino acids, carboxylic acids, polymers and polyphenols followed the order of rural natural forest > suburban forest > urban forest. There were significant spatial variations in the functional characteristics of soil microbial communities under urban-rural environmental gradient, with Tween 80 and β-methyl-D-Glucoside being the characteristic carbon sources as the influencing factors. Soil pH was significantly positively correlated with the microbial McIntosh index and AWCD value, while soil ammonium nitrogen (NH₄⁺-N) showed a significant positive correlation with microbial Shannon diversity index and AWCD value. There was a negative correlation between the microbial Simpson index and soil nitrate nitrogen (NO₃^--N). Soil pH, NH₄⁺-N and NO₃^--N were the main factors affecting diversity index of microbial communities. The results suggested that there were significant differences in microbial community characteristics of forest soil in urban-rural environmental gradient forests, and that the metabolic potential and functional diversity of soil microbial community in urban forests were weaker than that of natural forests.

Population status and protection evaluation of Syzygium album, a species with extremely small population.

ZHENG Shi-qun, YANG Wan-qiao, FANG Zhen-fu, ZHENG Ning, LIU Jin-fu, LIN Kai-qin, XIAO Li-fang, LI Lin

2021, 32(1):  103-112.  doi:10.13287/j.1001-9332.202101.007

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Syzygium album is a plant species with extremely small population and endemic to Yun-xiao County, Fujian Province. We examined its population status and conservation evaluation. The results showed that there were 25 individuals of S. album, with only one mother tree. Except for the mother tree and one small tree, the others were all young seedlings, which was rare in abundance and lack of age stage of middle and strong trees. The spatial distribution of young seedlings was not uniform, with most of individuals within the range of 10-25 m from the mother tree. The age class structure of the population was not continuous and the population development was unsustainable. The competition mainly came from other species. Cryptocarya chinensis accounted for 66.6% of the total competition index, which was much higher than other species. We established a comprehensive evaluation index system for the protection of rare and endangered plants with extremely small populations and evaluated the protection of S. album from three aspects, i.e., endangered degree, protection value, and protection priority. The endangered degree of S. album was level Ⅰ (the endangered degree index was 4.510), belonging to extremely endangered species, the protection value was level Ⅰ (the protection value index was 4.052), which was of great value, and the protection priority was level Ⅰ (the protection priority index was 4.016), which should be listed as the highest priority protection level.

Spatial-temporal trend of grassland net primary production and their driving factors in the Loess Plateau, China

LIU Zheng, YANG Jin-gui, MA Li-hui, KE Zeng-ming, HU Yu-mei, YAN Xiao-ying

2021, 32(1):  113-122.  doi:10.13287/j.1001-9332.202101.017

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Net primary productivity (NPP) of grassland is a key link and important part of the ecosystem’s carbon cycle. We estimated the changes of NPP in grasslands of the Loess Plateau with unchanged land use types during 2000-2015 and analyzed its responses to the variation of main climate factors (annual precipitation, annual heavy rainfall, annual effective rainfall days, annual average temperature, annual maximum temperature, annual minimum temperature) using piecewise linear regression and Pearson correlation analysis. The driving factors of grassland NPP were further analyzed by pixel-by-pixel with boosted regression tree analysis. The results showed that annual mean grassland NPP in the Loess Plateau showed an increasing trend during the study period, with 51.3% of the total grassland area showing a significant increasing trend. The average increase rate of annual mean NPP declined from 15.23 g C·m^-2·a^-1 in 2000-2004 to 3.58 g C·m^-2·a^-1 in 2004-2015. There was a significant positive correlation between grassland NPP and precipitation, but negative correlation with temperature factors. Annual precipitation was the dominant climatic factor affecting NPP of the whole study area with the highest relative importance. Annual maximum temperature was the dominant driving force of grassland NPP of central Loess Plateau, while annual minimum temperature mainly affected the growth of grassland in high-altitude area of the western Loess Plateau.

Groundwater depth and its relation with typical vegetation distribution in the Poyang Lake wetland, China

SONG Yan-yan, ZHANG Qi, JIANG San-yuan, GUO Yu-yin

2021, 32(1):  123-133.  doi:10.13287/j.1001-9332.202101.018

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Groundwater level directly affects soil water content, which in turn impacts the growth, distribution, and succession of wetland vegetation. Based on the groundwater monitoring data during 2014 to 2018, we analyzed the inter- and intra-annual variations in groundwater level of the wetland in Poyang Lake. We set up a groundwater numerical model to investigate the spatial patterns of groundwater flow field and distribution of groundwater depth. The relationship between groundwater depth and distribution of typical vegetation was explored with Gaussian regression analysis. Results showed that groundwater level of the wetland showed inter-annual variation, with the trend highly consistent to the changes in lake water level. There was a lag of one month between the inter-annual change in groundwater depth and the seasonal distribution of precipitation. The annual groundwater level showed a decreasing trend from upstream to downstream. The range of groundwater depth in upstream area of the wetland was narrower (0.1-1.1 m) than that of the downstream area (0.1-5.6 m). The groundwater flow field was directed from the hilly upstream area to the relatively flat downstream lake area, with the flow direction consistent with the change in elevation. The ground-water depth decreased with decreasing distance to the lake water body, with an average value of 2.07 m in the study are. The optimal groundwater depths for the growth of Carex, Phragmites aus-tralis, and Artemisia capillaris communities were 1.1, 3.7 and 5.7 m, respectively. The typical vegetation distribution showed different responses to groundwater depth. The ecological width of A. capillaris communities was larger than the Carex and P. australis communities. The three types of community were overlapped in ecological niche when the groundwater depth ranged 1.1-5.7 m. The vegetation distribution index of Carex decreased rapidly, that of P. australis increased firstly and then decreased, while that of A. capillaris increased continually to the maximum and began to decrease when the groundwater depth reached 5.7 m.

Comparison of global sensitivity analysis techniques based on a process-based model CROBAS.

XUE Hai-lian, TIAN Xiang-lin, WANG Bin, SUN Shuai-chao, CAO Tian-jian

2021, 32(1):  134-144.  doi:10.13287/j.1001-9332.202101.005

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Constructions of process or mechanistic models are limited by physiological parameters, due to difficulty in direct and precise measurement. Global sensitivity analysis could evaluate the response of model outputs to changes in physiological parameters, and provide information for improving model structure, data collection, and parameter calibration. Based on a process model CROBAS, 10 parameters related to tree structure of Pinus armandii were selected to compare three widely used global sensitivity analysis methods (the Morris screening method, the variance-based Sobol indices, and the Extended Fourier Amplitude Sensitivity Test (EFAST)), with the objective function formulated by the Nash-Sutcliffe Efficiency (NSE) of tree height and biomass. The results showed that the sensitivity order of parameters slightly varied across different methods, which considerably changed with different objective functions. Both the Morris method and the EFAST method outperformed the Sobol method in terms of time consuming and convergence efficiency. All outputs were sensitive to the maximum rate of canopy photosynthesis per unit area, the specific leaf area, and the extinction coefficient. The light interception of tree canopy played a key role in the simulation of tree growth with CROBAS, suggesting that the module of photosynthetic carbon fixation took priority over any other modules for data collection and model validation during module calibration and tree growth simulation for CROBAS. The calculation and validation of foliage biomass module were crucial when applying carbon balance theory to biomass simulations. In conclusion, for the sensitivity analysis of a complex process-based model, the Morris method was suitable for qualitative studies, while the EFAST method was recommended for quantitative studies.

Comprehensive effects of combined application of organic and inorganic fertilizer on yield, greenhouse gas emissions, and soil nutrient in double-cropping rice systems

BU Rong-yan, LI Min, HAN Shang, CHENG Wen-long, WANG Hui, SUN Zhi-xiang, TANG Shan, WU Ji

2021, 32(1):  145-153.  doi:10.13287/j.1001-9332.202101.023

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We carried out a 3-year field experiment with three treatments: 1) no fertilizer application (CK), 2) chemical fertilizer application (F), and 3) combined organic and chemical fertilizer (FM) in which the total nitrogen inputs were equal with F (organic fertilizer applied in the early rice season). We evaluated the variations of crop yield, CH₄ and N₂O emission, and soil nutrient. The results showed that fertilizer application could increase rice yield in both early and late rice seasons. Compared with F treatment, FM treatment increased rice yield by 5.6% and 7.2% for early and late rice, respectively. The enhancement of yield was positively correlated with years. Compared with F treatment, CH₄ emission in early rice season, late rice season and whole year in the field in FM treatment was increased by 8.2%, 4.8% and 6.7%, respectively, while the N₂O emission was deceased by 31.4%, 5.0% and 18.8%, respectively. Organic fertilizer application reduced the greenhouse gas intensity (GHGI) by 6.8% and 8.5%, but there was no significant differences in global warming potential (GWP) across treatments in 2018 and 2019. Compared with F treatment, the content of organic matter, total nitrogen, available phosphorus and available potassium were increased by 9.7%, 4.1%, 30.9% and 2.5%, respectively. Overall, our results suggested FM application in early rice season is an effective measure to increase crop yield, improve soil nutrient, and reduce GHGI.

Effects of organic manure partial substitution for chemical fertilizer on the photosynthetic rate, nitrogen use efficiency and yield of rice

SHI Xin-rui, REN Bin-bin, JIANG Lin-lin, FAN Shu-xiu, CAO Ying-li, MA Dian-rong

2021, 32(1):  154-162.  doi:10.13287/j.1001-9332.202101.021

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Rational application of organic fertilizers is an effective approach to improve soil fertility, crop yield, and zero growth of chemical fertilizer in agricultural production. The rice variety ‘Shennong9816’ was planted in Shenyang, Liaoning Province, under seven different treatments: zero nitrogen fertilizer (CK), low nitrogen, 150 kg·hm^-2(LN), medium nitrogen, 240 kg·hm^-2 (MN), high nitrogen, 330 kg·hm^-2(HN), medium nitrogen with replacement of chemical N by 10% organic manure (OMN₁₀), medium nitrogen with replacement of chemical N by 20% organic manure (OMN₂₀), and medium nitrogen with replacement of chemical N by 30% organic manure (OMN₃₀). The effects of different treatments on photosynthetic rate, nitrogen absorption, nitrogen use efficiency, and yield were examined and the optimal fertilization scheme was determined. The results showed that the photosynthetic rate, biomass and yield were increased with the increases of nitrogen application rate, while the nitrogen use efficiency was decreased significantly. Compared with the MN treatment, the photosynthetic rate of OMN₁₀ and OMN₂₀ in filling stage was increased by 22.9% and 9.9%, respectively. The yield of OMN₂₀ was increased by 3.8% compared to that of MN. The nitrogen agronomic efficiency and physiological efficiency of OMN₂₀ were significantly improved by 8.1% and 13.3%, respectively. Moreover, the nitrogen agronomic efficiency and physiological efficiency of OMN₂₀ were improved by 27.2% and 37.2% compared with the HN treatment. Thus, we concluded that the organic fertilizer replacement treatment could conserve soil fertility, achieve high yield and high nitrogen use efficiency, while reduce chemical nitrogen fertilizer application. The OMN₂₀ treatment was recommended as a fertilizer application model due to its superior performance among the seven treatments.

Interactive effects of irrigation regime and planting density on grain yield and water use efficiency in winter wheat

ZHANG Xiu, ZHU Wen-mei, DONG Shu-xin, CHU Jin-peng, FEI Li-wei, ZHENG Fei-na, DAI Xing-long, HE Ming-rong

2021, 32(1):  163-174.  doi:10.13287/j.1001-9332.202101.025

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To get an optimal irrigation regime and planting density for simultaneous improvement of grain yield (GY) and water use efficiency (WUE) in winter wheat, we examined the responses of ‘Tainong 18’ (with bigger ears) and ‘Shannong 22’ (with medium-sized ears) under four irrigation regimes, including 0, 45, 60, and 75 mm. Those two cultivars were planted at four densities: Tainong 18 at 135×10⁴, 270×10⁴, 405×10⁴, and 540×10⁴ plants·hm^-2 and Shannong 22 at 90×10⁴, 180×10⁴, 270×10⁴, and 360×10⁴ plants·hm^-2. The interactive effects of irrigation regimes and plant densities on GY, water consumption characteristics, and WUE were investigated. The results showed that GY, evapotranspiration, soil water consumption, and WUE were significantly affected by irrigation regime, plant density, and their interaction. The optimal irrigation regime was 45 mm for both cultivars, while the optimal plant density was 405×10⁴ plants·hm^-2 for Tainong 18 and 270×10⁴ plants·hm^-2 for Shannong 22, as indicated by the highest GY, the lowest ratio of soil evaporation to evapotranspiration after jointing, and higher WUE and the ratio of soil water consumption below 1 m to total soil water consumption. The rational combination of plant density and irrigation could reduce unnecessary water consumption and improve WUE.

Method for estimating relative chlorophyll content in wheat leaves based on chlorophyll fluorescence parameters

YANG Cheng, DU Si-meng, ZHANG De-qi, LI Xiang-dong, SHI Yan-hua, SHAO Yun-hui, WANG Han-fang, FANG Bao-ting

2021, 32(1):  175-181.  doi:10.13287/j.1001-9332.202101.009

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Chlorophyll content is a physiological index widely used in the research of botany and agriculture. It is closely associated with leaf photosynthetic function. The current methods cannot simultaneously determine chlorophyll content and photosynthetic function and analyze their correlation. To solve this problem, we measured the SPAD value and chlorophyll fluorescence induction kinetic curve with 35 wheat varieties. We established a linear regression model using the fluorescence values of the fast chlorophyll fluorescence kinetic curve at different times, 33 common fluorescence parameters, and the correlation between the parameters and the SPAD values. We further verified the model using laboratory and field data. Our results showed that the linear model based on chlorophyll fluorescence parameter RC/CS_m could reliably predict the SPAD value of the leaves, which could be used to estimate the relative content of chlorophyll in wheat leaves under non-severe stress. The linear model enriched the method of nondestructive measurement of chlorophyll relative content in wheat, simplified the experimental flow, and achieved the simultaneous determination and analysis of wheat photosynthesis function and chlorophyll content.

Elevated CO₂ concentration mitigate the effects of drought stress on soybean

ZHANG Xiao-qin, ZHANG Yuan-ling, LI Bing-yan, FENG Ya-nan, LI Ping, ZHANG Dong-sheng, WANG Li-wei, HAO Xing-yu

2021, 32(1):  182-190.  doi:10.13287/j.1001-9332.202101.022

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The climate change caused by elevated CO₂ concentration and drought are bound to affect the growth of soybean. Few studies have addressed the effects of elevated CO₂ concentration on the physiology and biochemistry of soybean under drought stress. Here, we examined the changes of photosynthetic ability, photosynthetic pigment accumulation, antioxidant level, osmotic adjustment substances, hormone levels, signal transduction enzymes and gene expression level of soybean at flowering stage under different CO₂ concentration (400 and 600 μmol·mol^-1) and drought stress (normal water: leaf relative water content was 83%-90%; drought stress: leaf relative water content was 64%-70%). The results showed that the transpiration rate, water use efficiency and net photosynthetic rate of soybean leaves were significantly increased by elevated CO₂ concentration, but the content of chlorophyll b was decreased under drought stress. Elevated CO₂ concentration significantly increased peroxidase activity and abscisic acid content of leaves under drought stress, decreased the content of proline, and did not affect the content of soluble saccharides. The increased CO₂ concentration under drought stress significantly promoted the content of calcium-dependent protein kinase and glutathione-S-transferase, and up-regulated the expression of related genes, while significantly decreased the content of mitogen-activated protein kinase and the heat shock protein, and down-regulated the expression of their genes. The results would be helpful to understand the impacts of climate change on the growth, physiology and biochemistry of soybean, and to deal with the production problems of soybean under future climate change.

Effects of fertilization and planting patterns on soil aggregate and carbon distribution in farmland of the Loess Plateau, Northwest China

LI Chun-yue, CHANG Shun, ZHONG Fan-xin, XUE Ying-long, MIAO Yu, WANG Yi, DANG Ting-hui

2021, 32(1):  191-200.  doi:10.13287/j.1001-9332.202101.027

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Based on a long-term experiment in the Changwu Agro-ecological Experimental Station in Xianyang, Shaanxi, China, we examined the effects of fertilization and planting patterns on soil aggregate quantity, aggregate stability and total carbon and organic carbon distribution in different aggregate fractions through dry and wet sieving methods, as well as the TOC combustion method. There were ten treatments, including uncultivated (R), wheat continuous cropping (CK/W), wheat-corn rotation (L), and nitrogen fertilizer (N), phosphorus fertilizer (P), nitrogen and phosphorus fertilizer (NP), organic fertilizer (M), nitrogen and organic fertilizer (NM), phosphorus and organic fertilizer (PM), nitrogen and phosphorus and organic fertilizer (NPM) for CK/W. The results showed that fertilizer application and planting patterns affected soil aggregate distribution and stability, the contents and contribution rates of total C and organic C. Force-stable aggregate was mainly constituted by >0.25 mm aggregate (>67%), which was reduced by fertilization. Continuous cropping decreased micro-aggregate while rotation facilitated it and the effect was larger than fertilization. Water-stable aggregate was mainly comprised of micro-aggregate (<0.25 mm), the contribution of which was larger than 61%. Both fertilizer application and planting pattern reduced water-stable micro-aggregate. Fertilizer application and planting pattern decreased the percentage of aggregate destruction rate (PAD) and increased macro-aggregate (>0.25 mm, R_0.25) content. Organic fertilizer significantly improved total C and organic C concentrations in all the fractions of force-stable aggregates. Continuous cropping and rotation cropping increased total C concentration in all the aggregate fractions while rotation cropping significantly decreased organic C concentration. Single N and P fertilization decreased soil total C concentration, while mixed application of N and P fertilizers, and organic fertilizer significantly increased soil total C concentration. The effect of planting patterns on soil total C was lower than that of fertilization. Both continuous cropping and rotation cropping increased soil total C. Mixed application of N and P fertilizers, and organic fertilizer signifi-cantly increased soil organic C concentration while single N and P fertilization decreased it. The effect of planting patterns on soil organic C was lower than that of fertilization, while rotation cropping did not facilitate soil organic C. Micro-aggregate was the most notable size fraction to total carbon and organic C, with the contribution being 21.2%-33.6%. Fertilization and planting pattern increased the contribution rate of micro-aggregate in soil total C. NP and NPM significantly increased the contribution rate of micro-aggregate in soil total C and soil organic C. The effect of rotation cropping was most obvious in driving the contribution rate of micro-aggregate in soil total C and soil organic C.

Simulation on soil moisture and water productivity of apple orchard on the Loess Plateau, Northwest China

WANG Xian-zhi, ZHAO Xi-ning, GAO Xiao-dong, WEI Wei, WANG Shao-fei, YU Liu-yang, WANG Jia-xin, SHAO Zhu-en

2021, 32(1):  201-210.  doi:10.13287/j.1001-9332.202101.012

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The WinEPIC model was used to simulate the dynamics of soil moisture and water productivity in the deep layer of the dry farm apple orchard of Changwu in the Loess Plateau from 1980 to 2018, aiming to provide a scientific basis for the sustainable development of apple production in the area. The results showed that the average annual yield of apple orchards in Changwu area was 27.37 t·hm^-2, the average annual evapotranspiration was 673.66 mm, and the average annual water productivity was 4.07 kg·m^-3. The number of water stress days in adult apple trees was mainly affected by rainfall. The average number of stress days in the late stage of apple tree growth was 46.46 d. The soil water content in deep layer began to approach withering humidity as early as 9-year-old apple trees. Water supply in the whole growing season of Changwu area was the dominant factor impacting the yield of orchards. The reduction of effective soil water content in deep soil was the main factor restricting yield enhancement in the middle and late growth stages of apple trees. When there was no sufficient precipitation, apple trees would use soil water from deeper soil layer. Excessive precipitation could not be used by apple trees but could be converted into shallow soil moisture and evaporation if the deep layer had less available water. For the mature apple trees, less than 500 mm or higher than 700 mm of annual water supply would cause a decline in production. For apple orchard at different growth periods, water management strategy should be adjusted according to rainfall conditions in different years. Supplementary irrigation, rainwater retention, covering, and pruning of branches could be used to reduce the unproductive and luxury water consumption of apple trees, delay the appearance of deep dry layer of soil, and avoid the waste of water resources while ensuring the growth of apple trees.

Effects of soil matrix potential regulation at various growth states on cotton growth and soil water and salt distribution

CHENG Hou-liang, ZHANG Fu-cang, LI Meng, ZHENG Wen-hui, XIAO Chao, LI Yue-peng

2021, 32(1):  211-221.  doi:10.13287/j.1001-9332.202101.029

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Water shortage and soil salinization are two main limiting factors for cotton production in southern Xinjiang. We examined the effects of soil matrix potential (SMP) regulation at various growth stages on cotton growth, soil water and salt distribution, to provide theoretical basis for water saving, salts control, and efficient production in cotton fields. The mulched drip irrigation experiments were conducted to monitor cotton growth, aboveground biomass, cotton yield, soil water and salt distribution and other indicators. Three SMP thresholds, i.e.,W₁(-20 kPa), W₂(-30 kPa) and W₃(-40 kPa) were set at the seedling stage (A), seedling stage + budding stage (B), and seedling stage + budding stage + flowering stage (C), with SMP of -50 kPa at 20 cm soil depth below the emitter as the CK. The results showed that plant height, leaf area index (LAI) and aboveground biomass followed the order of WC>WB>WA>CK, when SMP were changed at various growth stages. Plant height, LAI and aboveground biomass increased with increasing SMP thresholds, with the values under W₁C and W₂C being significantly higher than the other treatments. The effective bolls per plant, single boll weight and lint percentage all increased with the increases of SMP thresholds. The yields of W₁C and W₂C were similar, which were significantly higher than those of other treatments. However, the water use efficiency of W₂C was significantly higher than that of W₁C. Controlling the SMP threshold at -20 or -30 kPa at different growth stages could improve soil moisture status of the primary cotton root zone. All treatments presented shallow salt accumulation (0-40 cm) at the harvest stage, with the bare land having greater salt accumulation than the inner film. The higher the SMP threshold was, the less salt was accumulated in the primary root zone (0-40 cm) under film. The salt accumulation (0-40 cm) under W₁C and W₂C were reduced by 24% compared with other treatments. Considering the efficient production of cotton, water saving and salt control, it was recommended to maintain the SMP threshold of -30 kPa during irrigation at various growth stages in cotton fields without leaching salts during the local off-crop period.

Effects of foliar spraying with low concentration NaCl on the growth and physiological responses of cucumber seedlings under temperature regulation in solar greenhouse

MENG Chuang, XUE Zhan-jun, YANG Ji-long, LI Shou-mian, GAO Zhi-kui

2021, 32(1):  222-230.  doi:10.13287/j.1001-9332.202101.024

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In order to clarify the effects of foliar spraying the solution with low concentration NaCl on the growth and matter accumulation of vegetables under the temperature-regulated solar greenhouse, we carried out an experiment on cucumber seedlings with two cotyledons, under two tempera-ture regimes and four concentrations of NaCl. Low-medium temperature zone (L) and medium-high temperature zone (H) were set by low tunnel with plastic film in the greenhouse. The solutions with different concentrations of NaCl, 0 mmol·L^-1 (L₀ and H₀), 5 mmol·L^-1 (L₅ and H₅), 10 mmol·L^-1 (L₁₀ and H₁₀) and 15 mmol·L^-1 (L₁₅ and H₁₅), were sprayed every day to the cucumber seedlings. The seedling growth, plant biomass, nutrient accumulation and photosynthetic gas exchange parameters of cucumber seedlings were measured at the 21th day of spraying treatment. Compared with the control groups (L₀ and H₀), NaCl spraying significantly increased dry matter and plant water content by 38.6% (L₅)-50.2% (L₁₀) and 20.8% (L₅)-52.2% (L₁₀) in L zone, 8.9% (H₅)-23.3% (H₁₀) and 8.7% (H₅)-10.1% (H₁₀) in H zone, respectively. The treatment of 10 mmol·L^-1 NaCl (L₁₀ and H₁₀) under both temperature regimes increased dry matter accumulation and plant water content than other treatments. Nevertheless, the highest normalized strong seedling index (SI) with the highest stomatal conductance (g_s) and photosynthetic rate (P_n) was only found in L₅ treatment. L₁₀ treatment promoted foliar expansion much more than H₁₀ treatment. In addition, foliar spraying NaCl with concentrations from 5 mmol·L^-1 to 10 mmol·L^-1 under both temperature regimes significantly increased the accumulation of soluble sugar, free amino acids and soluble protein, which were preferentially allocated to the stem or root of cucumber seedlings. Results of two-way ANOVA showed significant effects of both temperature and NaCl concentration on dry biomass, leaf area, P_n, plant water content, SI, g_s and free amino acid content. On the contrary, there were significant interactions between temperature and NaCl concentration in affecting plant water content, SI, g_s and free amino acid content (except leaf). In conclusion, foliar spraying with 5-10 mmol L^-1 NaCl could promote growth and physiological indices of cucumber seedlings, with the effect being higher under low temperature regime. More importantly, foliar spraying of proper concentration (L₅ and H₁₀) of NaCl could stimulate biomass accumulation more than water retention in cucumber seedlings, which would provide a relevant breeding target for high water-use efficiency in cucumber.

Effects of high temperature on photosynthetic physiological characteristics of strawberry seedlings in greenhouse and construction of stress level.

XU Chao, WANG Ming-tian, YANG Zai-qiang, HAN Wei, ZHENG Sheng-hua

2021, 32(1):  231-240.  doi:10.13287/j.1001-9332.202101.028

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Strawberry variety ‘Benihoppe’ was used as the experimental material. The temperature treatments were set at 32 ℃/22 ℃, 35 ℃/25 ℃, 38 ℃/28 ℃ and 41 ℃/31 ℃ (daily maximum temperature/daily minimum temperature), and the stress days lasted for 2, 5, 8 and 11 d, with 28 ℃/18 ℃ as the control. We measured the photosynthetic characteristics, chlorophyll fluorescence characteristics, reactive oxygen species, protective enzyme activity and membrane lipid peroxidation of strawberry under different high temperature treatments. The key indices were extracted by principal component analysis. The high temperature stress index (Z) was defined to divide the high temperature stress grade. The results showed that 1) with the aggravation of high temperature stress and the extension of stress time, chlorophyll a (Chl a), chlorophyll b (Chl b), carotenoid (Car), light saturation point (LSP), maximum net photosynthetic rate (P_max), apparent quantum efficiency (AQE) and maximum photochemical efficiency (F_v/F_m) decreased, while light compensation point (LCP) and dark respiration rate (R_d) increased. 2) High temperature hindered the energy transfer of thylakoid in PSⅡ center (ΔW_OK＞0), and accelerated the reduction rate of PSⅠ terminal electron receptor pool. On the 11th day of the stress, except that under 32 ℃, all other oxygen evolution complexes (OEC) were inactivated. 3) The content of reactive oxygen species (H₂O₂ Content and O₂^-· production rate) and malondialdehyde (MDA) increased with the stress days under different high temperature treatments. 4) The protective enzyme activities and soluble protein content increased first and then decreased with stress duration. 5) Based on principal component analysis (PCA) and combined with the difficulty of index acquisition, Chl a, P_max, F_v/F_m and MDA were extracted as the key indices, and Z value was calculated. Five high temperature stress grades were divided which were normal (0<Z≤1), mild (1<Z≤2), moderate (2<Z≤3), severe (3<Z≤4) and extra severe (4<Z). The results would be helpful for the prevention of strawberry high temperature disaster and the optimization of microclimate environment.

Identification and characteristics of multiple agrometeorological disaster of maize in Liaoning Province, China

YU Wen-ying, JI Rui-peng, LI Zhuo-qun, LIU Dong-ming, FENG Rui, WU Jin-wen, ZHANG Yu-shu

2021, 32(1):  241-251.  doi:10.13287/j.1001-9332.202101.011

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Multiple agrometeorological disaster (MAD) occurs simultaneously in maize production. In order to ascertain the occurrence regularity and characteristics of MAD of maize in Liaoning Pro-vince, we defined and classified MAD, identified MAD of 50 meteorological stations in the maize growing season of Liaoning Province from 1961 to 2017, and examined the effects of MAD on maize yield in typical years. The results showed that the occurrence range of MAD was higher in most years from 1961 to 2017 than that of single agrometeorological disaster (SAD), and that the occurrence frequency of MAD was higher in most areas than that of SAD. The major MAD in Liaoning Province was drought in multiple periods (M1-D), followed by the combination of drought and delayed cold damage (M2-DC). The occurrence range of M1-D showed an upward trend from 1961 to 2017, whereas other MAD types showed a downward trend. After analyzing the occurrence of MAD in the typical years of maize yield reduction, we found that the occurrence frequency of M1-D and M2-DC was higher.

Remote sensing inversion of cultivated land fertility at county scale based on SWCI-NDVI feature space

LI Yin-shuai, ZHAO Geng-xing, WANG Zhuo-ran, CUI Kun, XI Xue, DOU Jia-cong

2021, 32(1):  252-260.  doi:10.13287/j.1001-9332.202101.016

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It is objective needs during utilization and management of regional cultivated land resource to use remote sensing to accurately and efficiently retrieve the status of cultivated land fertility at county level and realize the gradation of cultivated land rapidly. In this study, with Dongping County as a case, using Landsat TM satellite imagery and cultivated land fertility evaluation data, the moisture vegetation fertility index (MVFI) was constructed based on surface water capacity index (SWCI) and normalized difference vegetation index (NDVI), and then the optimal inversion model was optimized to obtain the best inversion model, which was further applied and verified at the county scale. The results showed that the correlation coefficient between MVFI and integrated fertility index (IFI) was -0.753, which could comprehensively reflect the growth of winter wheat, soil moisture and land fertility, and had clear biophysical significance. The best inversion model was the quadratic model, with high inversion accuracy. This model was suitable for the inversion of cultivated land fertility in the county. The spatial distribution and uniformity of the inversion results were similar to the results of soil fertility evaluation. The area differences between the high, medium and low grades were all less than 2.9%. This study provided a remote sensing inversion method of cultivated land fertility based on the feature space theory, which could effectively improve the evaluation efficiency and prediction accuracy of cultivated land fertility at the county scale.

Effects of urban expansion on habitat quality in densely populated areas on the Loess Pla-teau: A case study of Lanzhou, Xi’an-Xianyang and Taiyuan, China

ZHOU Liang, TANG Jian-jun, LIU Xing-ke, DANG Xue-wei, MU Hao-wei

2021, 32(1):  261-270.  doi:10.13287/j.1001-9332.202101.019

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The rapid urbanization has greatly changed the spatial pattern and function of regional habitats, profoundly affected the material flow and energy flow between habitats, and also posed a serious threat to habitats and biodiversity. Here, we used InVEST model, landscape index and multiple linear regression to systematically analyze the spatial and temporal variation and influencing factors for the impacts of urbanization on habitat quality in the Loess Plateau and the densely populated areas from 1990 to 2018. The results showed that the urban expansion of Loess Plateau significantly affected habitat quality. Between 1990 and 2018, the area of construction land increased by 49.6%, resulting in a 5.2% reduction in the total area of habitat patch. After 2010, the urban patch area increased, but the patch density and fragmentation decreased, resulting in a spatial pattern of “high outside and low inside” for urban habitat quality. The rate of urban expansion in densely populated areas was significantly negatively correlated with the habitat quality. The average value of habitat quality in the region dropped by 2.7%, whereas the level of habitat degradation increased by 33.4%. The level of habitat quality was unstable, and patches with high-level habitats were easily converted to lower level. The conversion rates of Lanzhou, Xi’an-Xianyang and Taiyuan were 12.9%, 2.9% and 1.7%, respectively. There were eight influencing factors that could effectively explain the spatial variation of habitat quality (R²=68.7%). Among those factors, population density and distance to roads were the main factors for the fragmentation of habitats, while slope, GDP and precipitation had positive effects on the optimization of habitat spatial patterns.

Effects of slope length on soil erosion of Karst slope under different rainfall conditions

HUANG Kai, LIU Rui-lu, QIN Li, SONG Tao, LIU Zhong-xian, LI Rui

2021, 32(1):  271-280.  doi:10.13287/j.1001-9332.202101.020

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Based on the runoff and sediment yield data from 59 erosive rainfall plots with different slope lengths (5, 10, 15, 20, 25 m) in Shiqiao small watershed of Guizhou Province from 2012 to 2014, we analyzed the relationship between runoff and sediment yield and slope length under diffe-rent rainfall conditions. The results showed that, with the increases of slope length, the runoff yield of slope showed a ‘V-shape’ pattern, the sediment yield of slope increased first and then decreased. According to rainfall amount, rainfall duration, and average rainfall intensity, the 59 erosive rainfall in the study area could be divided into three types, including type A with short duration, heavy rain intensity and small rainfall, type B with medium duration, light rain intensity and medium rainfall, and type C with long duration, medium rain intensity and large rainfall. The relationships between runoff and sediment yield and slope length were different under different rainfall patterns. There was about 20 m critical slope length of sediment yield under type A and B. The sediment yield gradually increased with the increases of slope length under type C. There was a good cubic function relationship between slope length and runoff and sediment yield under different rainfall patterns. The variable amplitude of runoff and sediment yield was different among different slope lengths. Except the slope length of 15-20 m, the variable amplitude of runoff and sediment yield under type C was relatively large. The variation amplitude of sediment yield was significantly higher than that under other rainfall patterns. The total runoff yield under different rainfall patterns was type A>B>C. The sediment yield under type B was the smallest, that of type A at the slope length of 20 m was the largest and that of type C at other slope lengths was the largest. The correlation between compound rainfall factors and runoff and sediment yield was better than that of single rainfall factor under type A (common rainfall type in the study area). Rainfall amount (P), the pro-duct of rainfall duration and maximum 30 min rainfall intensity (TI₃₀), product of rainfall duration and average rainfall intensity (TI), product of rainfall amount and rainfall duration (PT) were significantly correlated with the runoff and sediment yield. Among those factors, P and TI had the strongest correlation with runoff. Further, the relationship between them and runoff under different slope lengths could be expressed by linear equation and S-curve. There was a good cubic function relationship between the sediment yield and its corresponding rainfall factors under different slope lengths.

Spatial heterogeneity of soil water physical properties in coal gangue pile in arid desert area

DANG Qian-nan, WANG Jin-xin, YAO Li-xia, LYU Guo-li, ZHANG Rui-qi

2021, 32(1):  281-288.  doi:10.13287/j.1001-9332.202101.014

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Based on grid sample method (20 m×20 m), spatial heterogeneity and distribution of soil water physical properties from 0 to 5 cm of the coal gangue pile in arid desert area were explored by using classical statistics and geostatistics methods. The results showed that the variation of soil bulk density, capillary porosity, capillary maximum moisture capacity, total porosity and saturated moisture contents were weak, while water content showed a moderate variation. The best fitting model of soil bulk density was Gaussian model, and exponential model was the best fitting model for other indices. The C₀/(C₀+C) values of soil bulk density and water content were low and had strong spatial autocorrelation. The capillary porosity, capillary maximum moisture capacity, total porosity and soil saturated moisture showed moderate spatial autocorrelation. Soil bulk density was negatively correlated with capillary porosity, capillary maximum moisture capacity, total porosity and water content, whereas there was no significant correlation between soil moisture content and other indices. Soil capillary porosity, capillary maximum moisture capacity, total porosity, and saturated water content showed a significant synergistic effect between each other. On Kriging contour maps, capillary porosity, capillary maximum moisture capacity, total porosity and saturated moisture had a similar spatial pattern, with high values on the middle and the left side of the lower slope, whereas soil bulk density showed an opposite pattern. Soil water content was mainly affected by the slope position and increased from the upper slope to the lower slope. Our results suggested that land preparation measures should be taken to loosen the soil in root area over the coal gangue pile in arid desert area during vegetation restoration. Moreover, irrigation amount should be properly increased on the upper slope during the initial stage of vegetation restoration, which could improve soil moisture status in the overlying soil area of coal gangue and create uniform and suitable soil water physical conditions for vegetation restoration.

Evapotranspiration estimation using three-temperature model and influencing factors of Nanning City, China

WEI Jun-pei, YANG Yun-chuan, XIE Xin-chang, LIAO Li-ping, TIAN Yi, ZHOU Jin-yu

2021, 32(1):  289-298.  doi:10.13287/j.1001-9332.202101.013

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Evapotranspiration is the key element of hydrological energy cycle and climate system. It is of great significance to estimate the spatiotemporal variation of evapotranspiration and its response to climate and land use changes for understanding the effects of water cycle and ecological processes in urban basins. Based on the three-temperature model and MODIS Image, we estimated and analyzed the spatiotemporal variation of evapotranspiration in Nanning City from 2001 to 2018, and examined the influence and driving mode of main climate factors and land use types on evapotranspiration. The results showed that the annual average evapotranspiration of Nanning City ranged from 495.7 to 781.1 mm during 2001-2018, with the inter annual relative variability ranging from -22.5% to 23.1%, showing an overall upward trend. The regional evapotranspiration showed a distribution pattern of high north-south and low middle, with the urban evapotranspiration being significantly lower than suburban area. The evapotranspiration had a significant multiple correlation with climate factors. The influence of temperature on the evapotranspiration was stronger than precipita-tion. Evapotranspiration was temperature driven in suburbs, but was driven by multiple factors in urban area. The average evapotranspiration of different land use types in Nanning was forests (823.4 mm) > grasslands (675.6 mm) > croplands (582.9 mm) > urban area (346.6 mm). The change of land use type was the main underlying surface factor leading to the significant change of regional evapotranspiration.

Biocontrol effect and mechanism of Bacillus laterosporus Bl13 against early blight disease of tomato

SUN Yi-fan, LIU Zhe, LI Hai-yang, ZHENG Ze-hao, JI Cheng-long, GUO Qiao, LAI Hang-xian

2021, 32(1):  299-308.  doi:10.13287/j.1001-9332.202101.036

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Bacillus laterosporus Bl13 has good antagonistic effect on the pathogen of tomato early blight (TEB) disease. A pot experiment was conducted to investigate the effect and mechanism of B. laterosporus Bl13 against TEB disease by measuring biological traits such as plant height, stem diameter, disease index of TEB, activity of plant defense enzyme in leaves, and microbial diversity and community composition in root area. The results showed that B. laterosporus Bl13 could significantly reduce the disease index of TEB disease incidence, increase the activity of defensive enzymes including polyphenol oxidase (PPO) and peroxidase (POD) in leaves, and reduce the effects of the disease on the aboveground and root growth of tomato. Meanwhile, B. laterosporus Bl13 improved soil microbial community structure in the root zone, by significantly increasing the relative abundance of plant growth-promoting bacteria (Bacillus and Pseudomonas) and decreasing that of Olpidium and Haematonectria. The results showed that B. laterosporus Bl13 could enhance plant resistance against TEB disease through improving the activity of defensive enzymes in tomato leaves and increasing the number of beneficial microbes in the root zone.

Reconstruction of temporal and spatial trends of atmospheric pollution based on polychlorinated biphenyls concentration changes in ombrotrophic bogs

JIN Yu-bin, ZHOU Xu-dong, XIE Yu-chu, YU Zhi-guo

2021, 32(1):  309-316.  doi:10.13287/j.1001-9332.202101.035

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To reconstruct the deposition rate of polychlorinated biphenyls (PCBs) in different historical periods and to examine the temporal and spatial trend of PCBs pollution, we analyzed the changes of PCBs concentration and deposition rate in peat cores and lake sediments, and evaluated the suitability of peat cores and lake sediments for studying PCBs deposition trend. Through the dating analysis of all samples, we found that peat bog could well record the historical sedimentation of PCBs. PCBs did not degrade in peat, and it was thus feasible to use peatland to examine the settlement of PCBs. In this study, the reconstruction time of ∑₁₁PCBs in peat was from the beginning of 19th century to the beginning of 21st century. The mean inventory of ∑₁₁PCBs in three peat cores of each bog changed between (37.0±5.4) and (47.2 ±27.8) μg·m^-2, with the standard deviation between 14.9% and 58.9%. The highest concentration of ∑₁₁PCBs was 6.8 ng·g^-1DW, while the maximum deposition rate of reconstructed PCBs was up to 989.7 ng·m^-2·a^-1. The trend of deposition rate was first increasing and then decreasing. After the year 1980, the deposition rate was substantially decreasing, which was consistent with the prohibition of PCBs production in the United States in 1979. Meanwhile, the analysis of sediment samples in the lake near bog showed that concentration and maximum deposition rate of the lake sediment were comparable to those of the nearby bog. The concentrations of Di- to Hepta-PCB congeners were evenly distributed along the sediment profile. Therefore, lake sediments could not be used to analyze the historical sedimentary model of low order PCBs. This study reconstructed temporal and spatial variation of PCBs in atmospheric environment in different historical periods, which could provide basic data for the evaluation of regional environmental quality.

Effects of polystyrene microplastics (PS-MPs) on the growth, physiology, and biochemical characteristics of Hydrilla verticillata

ZHANG Chen, JIAN Min-fei, CHEN Yu-meng, CHEN Qing-qing, HE Xu-fen, CONG Ming-yang, YANG Wen-jing

2021, 32(1):  317-325.  doi:10.13287/j.1001-9332.202101.037

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In order to evaluate the effects of polystyrene microplastics (PS-MPs) on the growth, physiology, and biochemical characteristics of submerged plants, we exposed a typical submerged plant, Hydrilla verticillata, to a series of concentrations (i.e. 0, 5, 10, 30, 50, 100 mg·L^-1) of 3 μm polystyrene microplastics (PS-MPs) and measured parameters including height, biomass, chlorophyll content, antioxidant enzyme activity, photosynthetic fluorescence. The results showed that the height of H. Verticillata significantly decreased at the high PS-MP concentrations (50 to 100 mg·L^-1), while the fresh weight significantly increased at the low PS-MP concentration (5 mg·L^-1). The fresh weight of H. verticillata gradually decreased with the increasing PS-MP concentration but the dry weight did not change. The total amount of chlorophyll, chlorophyll a, and chlorophyll a/b significantly decreased with the increases of the PS-MP concentrations, while the chlorophyll b did not change. PS-MPs affected the antioxidant enzyme activities of H. verticillata. The activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were first increased and then decreased with the increasing PS-MP concentration. The chlorophyll fluorescence parameters (F_o, F_m, F_v/F_m) decreased with the increasing concentration of PS-MP and the 1-Q_p-Lss value (reflective of the closing of PSⅡ reaction center) was increased under the stable state, probably due to the inhibited PSⅡ reaction center. The overall intensity of fluorescence imaging of H. verticillata decreased with the increasing concentration of PS-MPs. When the PS-MP concentration was lower than 10 mg·L^-1, the photosynthetic activity of the leaves was normal. In contrast, when the PS-MP concentration was higher than 30 mg·L^-1, it caused significant adverse effects on leaves, including weaker photosynthetic intensity and the presence of yellow or withered leaves. Our results suggested that H. verticillata could tolerate PS-MP pollution but its growth and photosynthesis would be inhibited at high concentrations (>30 mg·L^-1). Our results provided basic information to better understand the eco-physiological effects of PS-MPs in the freshwater environment.

Comparative evaluation of efficient bird repeller distance between gas gun and sound bird repeller

JIN Lin-yu, LI Shu-meng, ZHAO Xiao-ying, LIU Tai-shan, FAN Chen, LI Dong-lai

2021, 32(1):  326-332.  doi:10.13287/j.1001-9332.202101.038

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Bird strike accidents mainly occur in the airport area. Reducing bird activities through bird repeller equipment is one of the main measures to prevent bird strike. In this study, two bird species with high-risk, pigeon (Columba livia domestica) and kestrel (Falco tinnunculus), were selected as the subjects and the gas gun and directional acoustic bird repeller were selected as the evaluation objects in Shenyang Taoxian International Airport. This study aimed to examine the behavioral responses of birds at different distances during the normal operation of these equipment to explore their effective distance and effects. The results showed that the vigilant and escape behaviors of pigeons and kestrels at 10 m and 30 m away from the gas gun bird repeller which were significantly higher than those of the control, while the number of these behaviors at 50 m away was not significantly different from that of the control. Pigeons and kestrels at 50 m and 100 m away from the directional acoustic bird repeller could significantly increase their vigilant and escape behaviors, whereas the repeller could significantly cause kestrels to increase their vigilant behavior at 300 m away. We concluded that the effective bird expel distance of the gas gun was 30 m, and the directional acoustic bird repeller could effectively expel to 300 m, and that the effect of the directional acoustic bird repeller on birds was stronger than the gas gun. Our results could provide a reference for the introduction and rational use of bird expel equipment in the airports.

Heterogeneity of growth and maturity of Larimichthys polyactis in the offshore waters of southern Zhejiang, China

PEI Ru-de, GAO Chun-xia, TIAN Si-quan, MA Qiu-yun, FAN Qing-song

2021, 32(1):  333-341.  doi:10.13287/j.1001-9332.202101.031

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The variations of life history traits have been observed for many fish species, which gains much concerns in the study of aquatic biology and ecology. In this study, the biological characteristics were explored for yellow croaker (Larimichthys polyactis) in the offshore waters of southern Zhejiang, based on 4920 individuals collected from 13 fishery-independent seasonal surveys from autumn 2015 to autumn 2018. Linear mixed effects models were used to estimate the growth, maturity characteristics, and their heterogeneity. The body length of yellow croaker samples ranged from 13 to 215 mm with the dominant body of 110 to 154 mm. The body weight ranged from 0.5 to 182.2 g, with the dominant body weight from 20 to 55 g. The results showed that the linear mixed effects models with random effects from season, gender, and year performed best for length-weight relationship, with the lowest AIC and RMSE values. The effects of season were much larger than those of genders and years. When the length exceeded 160 mm, the weight gain rate of yellow croaker was faster in spring and summer, lower in autumn and winter, while the male individuals gained more weight than the females with the same body length. Among 4841 individuals of specimens with gonadal data, the individuals at maturity Ⅱ stage occupied 50.4%, and the individuals at maturity stage contributed to 19.6%. The results from the best linear mixed effects model showed that season had the most significant influence on the maturity of yellow croaker. The 50% maturity length (L_50%) was much lower in winter (124.6 mm) with no much difference between other seasons, indicating that yellow croaker matures earlier in winter. Our results indicated that linear mixed effect model could reflect the biological heterogeneity of yellow croaker conveniently and that the growth and maturity of yellow croaker had significantly sexual and temporal variations, which should be considered in the stock assessment and fishery management for yellow croaker.

Spatial niches of dominant zooplankton species in Yueqing Bay, Zhejiang Province

ZHANG Ya-zhou, ZHANG Lin-lin, YIN Rui, LUAN Hui-ni, LIU Zhi-jian, CHEN Jian, JIANG Ri-jin

2021, 32(1):  342-348.  doi:10.13287/j.1001-9332.202101.039

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The index of dominance (S), average crowding (X^*), niche breadth (B_i), and niche overlap (Q_ik ) of dominant zooplankton species were calculated using data collected from four zooplankton surveys from May 2016 to February 2017 in Yueqing Bay, Zhejiang Province. The results showed that there were 17 dominant zooplankton species (with S＞0.02). The niche breadth values of those dominant species differed greatly and were positively correlated with S. The niche overlaps of zooplanktons were extremely low. The total amount of species pairs with niche overlap higher than 0.6 (Q_ik＞0.6) were 25 in Yueqing Bay, which represented 18.4% of the total pairs. Results from the redundancy analysis showed that the distribution of dominant zooplankton species was mainly affected by temperature and salinity, which caused ecological differentiation of zooplankton species.

Reviews

Research progress on the effects of urban road green space on dispersion of local air pollutant

HU Yang, MA Ke-ming

2021, 32(1):  349-357.  doi:10.13287/j.1001-9332.202101.015

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In recent years, the research on the effects of urban road green space on local pollutant dispersion has been quite active, with mounting empirical results. Due to the lack of summary and arrangement, however, it is difficult to effectively guide the practice of urban green space construction. In this review, the road and green belt research objects were classified. Based on two common methods of field measurement and numerical simulation, the pollutant concentration index, vegetation characters and other influencing factors involved in relevant research were systematically reviewed. The effects of road green space on dispersion of local pollution were summarized. Future research should be strengthened in the aspects of expanding research objects, comprehensively considering multiple ecological processes, integrating two basic methods, and improving the accuracy and richness of data.

Research advances in direct interspecies electron transfer within microbes

LAN Jian-ying, JIANG Hai-ming, LI Xia

2021, 32(1):  358-368.  doi:10.13287/j.1001-9332.202101.032

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Hydrogen and formic acid have been considered as the intermediate electron transporters among microbes for a long time. In recent years, however, it has been found that direct interspecies electron transfer (DIET) might be an alternative beyond hydrogen/formic acid to transfer electron among microbes. As a new way of electron transfer among microbes, the electron transfer efficiency of DIET is higher than that of traditional hydrogen/formate transfer. The discovery of DIET has changed the traditional understanding that the growth and metabolism of microbial syntrophism must rely on electron carriers such as hydrogen or formic acid, and also has opened a new perspective for the study of microbial interaction. Although great progress has been made in the study of DIET, in-depth studies are still lacking on the microbes that can form co-culture via DIET, the mechanism of DIET, and the factors affecting DIET. In this review, we summarized the microbes that can form DIET, the mechanism underlying the extracellular electron transfer of microbe acted as electron donor in DIET, as well as the mechanism underlying the extracellular electron transfer of microbe acted as electron acceptor in DIET. The effects of conductive materials on DIET were elaborated, and several research directions for DIET were proposed, with the aim to mitigate performance degradation and facilitate research and development in this area.

Research progress on soil aggregates and associated organic carbon in salinized soils

WEI Shou-cai, XIE Wen-jun, XIA Jiang-bao, LIANG Ai-zhen

2021, 32(1):  369-376.  doi:10.13287/j.1001-9332.202101.026

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Soil aggregate, as a basic component of soils, plays an important role in improving soil structure and enhancing soil organic carbon (SOC) sequestration. The special soil properties induced by salinization, such as high ion concentrations (mainly Na⁺), shortage of organic material and bad condition of microbe, inhibit the formation and stability of soil aggregate. Therefore, it is important and meaningful to explore the dynamics of aggregate in salinized soils. Coastal wetland and inland salinized marsh wetland are important salinized ecosystems. We systematically summarized the progress and achievements on soil aggregate in salinized agriculture and wetland ecosystems. Agricultural practices, such as organic and/or inorganic soil amendment application, tillage practice, vegetation type, straw return and saline water irrigation, advance the formation and stability of aggregate and aggregate-associated organic carbon in salinized soils. We discussed the problems and deficiency in the present studies of aggregate and aggregate-associated carbon in salinized soils as well as the research aspects and hot topics in the future. This review would be helpful for comprehensively understanding the advances and development directions on aggregate in salinized soils.