Table of Content

15 August 2021, Volume 32 Issue 8

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Opinion of the Editor-in-Chief

A process-based model and simulation system of dynamic change and spatial variation in large-scale terrestrial ecosystems

YU Gui-rui, ZHAGN Li, HE Hong-lin, YANG Meng

2021, 32(8):  2653-2665.  doi:10.13287/j.1001-9332.202108.040

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More attention has been paid to the monitoring, assessment, prediction, early warning and sustainable management of regional ecological environment and the changes of ecosystem state in recent years. It is an important scientific and technological task to develop quantitative methods and numerical simulation techniques for ecosystem modelling, and to construct the continental scale numerical simulator with the characteristics of multi-process coupling, multi-technology integration, and multi-objective application for stimulating research on ecosystem and global change and its resources, environment and disaster effects, based on the in-depth understanding of the components, processes, functions, patterns, and their interaction mechanism of terrestrial ecosystem. Here, we reviewed the current status and future direction of terrestrial ecosystem models, and discussed the conceptual framework of developing the simulation system of dynamic change and spatial variation in large-scale terrestrial ecosystems and its resource and environment effect, as well as basic issues on the function orientation and structure design of the simulation system, which would provide reference for constructing Chinese terrestrial ecosystem numerical simulator.

Special Features of Conservation Tillage

Research advances on cover crop plantation and its effects on subsequent crop and soil environment

SUI Xin, HUO Hai-nan, BAO Xue-lian, HE Hong-bo, ZHANG Xu-dong, LIANG Chao, XIE Hong-tu

2021, 32(8):  2666-2674.  doi:10.13287/j.1001-9332.202108.027

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Cover crops are grown in temporal and spatial gaps of agricultural production to reduce or avoid soil exposure. As it can protect farmland soil from wind erosion, water erosion and human disturbance, planting cover crops is considered as a new type of conservation tillage practice. Here, we briefly introduced the planting management of cover crops, including crop species, planting modes, and the returning to farmland after their termination, which could provide a reference for efficiently planting cover crops at large scale during the fallow period. Based on domestic and foreign studies, we summarized the benefits of cover crops on agroecosystem, including cash crops, soil quality, weed control, greenhouse gas emission, and soil microbes. Our review illustrated their importance in improving soil quality and achieving sustainable agricultural development, despite the limitation of cover crops, including unobvious benefits in the short-term and the reduction of crop yield caused by improper management.

Effects of conservation tillage on soil microbial community and the function of soil carbon cycling

YANG Ya-li, MA Xue-song, XIE Hong-tu, BAO Xue-lian, LIANG Chao, ZHU Xue-feng, HE Hong-bo, ZHANG Xu-dong

2021, 32(8):  2675-2684.  doi:10.13287/j.1001-9332.202108.028

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Agricultural tillage practices significantly affect the structure and function of soil micro-bial community, as well as its control over soil carbon cycling. Conservation tillage practice based on no-tillage and crop straw returning is an important measure to improve soil carbon sequestration and fertility, in which soil microorganisms play a key role. Although many previous studies focus on the structure and function of microbial communities under conservation tillage, our overall understanding of soil microbial responses at community level upon conservation tillage is still lacking, due to the complexity of the soil, environmental factors and the different selections of microbial research methods. Furthermore, previous studies paid more attention to the role of soil microorganisms as decomposers and the contribution of plant-derived carbon to the formation of soil carbon pool, but ignored the contribution of microbial-derived carbon to the formation and stability of soil carbon pool. We summarized the paradigm shift in soil organic matter formation and stability theories, reviewed the research methods of soil microbial community, focused on the effects of conservation tillage on soil microbial biomass, community diversity and composition, carbon metabolism, as well as microbial-derived carbon storage, and proposed suggestions for future study, aiming to provide support for future studies regarding microbial responses and its control over soil carbon dynamics in agroecosystem.

Effects of corn stover mulch quantity on mid-infrared spectroscopy of soil organic carbon in a no-tillage agricultural ecosystem

ZHU Xue-feng, ZHANG Chun-yu, HAO Yan-jie, BAO Xue-lian, HUO Hai-nan, HE Hong-bo, LIANG Chao, XIE Hong-tu

2021, 32(8):  2685-2692.  doi:10.13287/j.1001-9332.202108.022

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We examined carbon chemical composition and stability along soil depth (topsoil 0-5 cm, mid-soil 20-40 cm, and deep soil 60-100 cm) in a no-tillage (NT) agricultural system with various amount of corn stover as mulch for 8 years, including 0 (NT₀), 33% (NT₃₃), 67% (NT₆₇) and 100% (NT₁₀₀), in Northeast China, using mid-infrared spectroscopy. The results showed that, relative to NT₀, the treatments of NT₃₃ and NT₁₀₀ increased polysaccharide content of the top layer and mid-layer soils, the former decreased topsoil carbon component diversity, while the latter maintained soil carbon stability of three soil layers. NT₆₇ increased carbon stability at the deep layer soil. Our results demonstrated that if corn stover resources were sufficient, NT with 100% corn stover mulch could both be beneficial to carbon availability at 0-40 cm soil layer and stability of the whole soil profile. The nonlinear relationship between the amount of corn stover mulch and the mid-infrared spectral characteristics of the soil called for further research on the microbial-control mechanism over soil carbon cycling under different amounts of corn stover mulch.

Effects of biochar application patterns on soil nutrients and nitrogen- and phosphorus-related enzyme activities in Phaeozem and Luvisol

LIU Xing, WU Guo-hui, ZHANG Yu-lan, XIE Hong-tu, CHEN Zhen-hua, CHEN Li-jun

2021, 32(8):  2693-2702.  doi:10.13287/j.1001-9332.202108.041

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We investigated the effects of different biochar application patterns on soil nutrient contents and element transformation, with soil samples being collected from two five-year field experiments in Phaeozem and Luvisol amended with biochar at annual low-rate (AL, 22.5 t·hm^-2·a^-1) and intervalic high-rate (IH, 112.5 t·hm^-2·5 a^-1). Changes of soil total carbon (C), nitrogen (N) and phosphorus (P) contents as well as the related enzyme activities were measured under different biochar application patterns to provide fundamental information for the straw utilization and soil fertility improvement in agroecosystem. Results showed that total C and organic N contents in AL treatment were significantly higher than those in IH treatment in Phaeozem soil. Compared with the control, the decreases of dehydrogenase activity in AL treatment was more pronounced than that in IH treatment in Phaeozem soil, and the increases of protease activity in IH treatment was pronounced than that in AL treatment in Luvisol. Compared with Luvisol soil, the application of biochar had stronger effect on total soil C and organic N contents in Phaeozem soil. Application of biochar significantly increased the activities of soil dehydrogenase and protease in Luvisol soil, but decreased the activity of soil dehydrogenase. Soil types and biochar application patterns interacted to affect soil C and N contents, microbial metabolic activity, N- and P-related enzyme activities. In summary, soil types and biochar addition affected soil properties and microbial characteristics, which would provide important information for straw application and soil management.

Soil organic and inorganic carbon pools as affected by straw return modes under a wheat-maize rotation system in the Guanzhong Plain, Northwest China

LI Yu-nuo, FAN Yuan-yuan, CAO Bin-bin, TIAN Xiao-hong, SHI Jiang-lan

2021, 32(8):  2703-2712.  doi:10.13287/j.1001-9332.202108.030

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To understand the effects of straw return modes on soil carbon pools, we investigated total soil organic carbon (SOC), labile organic carbon fractions, and inorganic carbon (SIC) in different straw return modes at a depth of 0-40 cm under a maize-wheat cropping system in the Guanzhong Plain, Shaanxi, based on an 11-year field experiment. There were five straw return modes, i.e., no return of straw of both wheat and maize (CK), the retention of high wheat stubble plus the return of chopped maize straw (WH-MC), the return of both chopped wheat and maize straw (WC-MC), the retention of high wheat stubble and no return of maize straw (WH-MN), and the return of chopped wheat straw and no return of maize straw (WC-MN). The proportions of SOC storage were significantly higher under the WH-MC and WC-MC treatments than that under the CK by 28.1% and 22.2%, respectively. The proportions of SIC storage were increased by 20.4% and 17.3%, respectively. Compared with the initial value, the increases of sequestered SOC and SIC ranged from -0.84 t·hm^-2 to 6.55 t·hm^-2, respectively, and from -0.26 t·hm^-2 to 8.61 t·hm^-2, respectively. The efficiency of sequestration of SOC was 7.5%. To maintain the basic SOC level, the minimum carbon input from straw was 4.65 t·hm^-2·a^-1. The contents of labile carbon fractions at the 0-20 cm layer increased significantly under the WH-MC and WC-MC treatments compared with those of the control. Results of principal component analysis showed that the changes in soil carbon pools were primarily affected by the amount of straw return. Additionally, the increases in SIC storage could be ascribed to the Ca²⁺ and Mg²⁺ ions derived from irrigation water and plant residues that could coprecipitate with the CO₂ from SOC mineralization to form CaCO₃. In conclusion, our results indicated that the straw return mode that utilized the retention of high wheat stubble and chopped maize straw was sufficient to maintain soil carbon storage and would be the optimal straw-returning strategy for the region.

Effects of tillage managements on soil microbial community structure in soil aggregates of fluvo-aquic soil

SHEN Xiao-lin, WANG Li-li, ZHAO Jian-ning, LI Gang, XIU Wei-ming, YANG Qi-chen, ZHANG Gui-long

2021, 32(8):  2713-2721.  doi:10.13287/j.1001-9332.202108.023

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In order to explore the impacts of different tillage managements on the structure and diversity of microbial community in fluvo-aquic soil, the phospholipid fatty acid (PLFA) method was used to determine microbial community composition in soil aggregates. Four tillage treatments were set up in Qihe County, Shandong Province, including rotary tillage with straw return (RT), deep ploughing with straw return (DP), subsoiling with straw return (SS) and no-tillage with straw return (NT). Our results showed that DP treatment significantly increased the amount of fungal PLFAs and fungi/bacteria ratio in >5 mm soil aggregates compared with RT. DP could provide favorable conditions for fungi reproduction, facilitate soil organic matter storage and soil buffering capacity. DP increased the amount of PLFAs in 5-2 mm soil aggregates, reduced the gram-positive (G+) /gram-negative (G-) bacteria ratio in the soil, and improved soil nutritional status. In addition, DP improved the microbial abundance index in <0.25 mm soil aggregates. In general, DP could not only increase the abundance of bacteria and fungi in soil aggregates, but also improve the microbial community structure of soil aggregate, which help increase soil carbon sequestration capacity and keep soil microbial diversity to a certain extent. Results of the redundancy analysis showed that the total PLFAs, PLFAs of bacteria, G- bacteria and actinomycetes in soil aggregates are closely correlated with soil organic carbon, while PLFAs of G+ bacteria had a strong correlation with soil total nitrogen concentration. In each treatment, microbial communities in larger sizes of soil aggregates were mainly affected by the ratio of organic carbon to total nitrogen, soil moisture, pH, and mass fractions of soil aggregates, while the microbial communities in smaller sizes of soil aggregates were affected by the concentrations of organic carbon and total nitrogen.

Original Articles

Effects of tree species interaction, stand density, and tree size on the productivity of Larix principis-rupprechtii

DONG Xue-ting, ZHANG Jing, ZHANG Zhi-dong, HUANG Xuan-rui

2021, 32(8):  2722-2728.  doi:10.13287/j.1001-9332.202108.006

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Pure and mixed larch (Larix pricipis-rupprechtii) and birch (Betula platyphylla) plantations in Saihanba area were selected as test objects, with two stand density (200-340 and 880-1100 trees·hm^-2) of each stand type. Based on tree size-stratified sampling approach, a total of 668 tree core samples were collected. A linear mixed model was used to analyze the effects of tree species interaction, stand density, and tree size on larch productivity. Results showed that basal area increment of larch was affected by competition, diameter at breast height, tree age, and neighborhood density to different degrees. Overyielding of larch was mainly due to the positive effect of birch on larch growth in the mixed plantation with higher stand density. For mixed plantation with lower stand density, the productivity of those two species was lower than that pure plantation because of a lack of species interaction. Intraspecific competition was the main factor influencing larch productivity. Larch productivity was positively affected by tree size, with the magnitude of tree size effect varying with stand density and species composition. Suitable enhancement of stand density and selection of birch as the mixing tree species could improve productivity of larch.

Prediction of crown leaf mass per area for young Larix olgensis plantation

ZHANG Ze-wen, WU Li-qin, SUN He, WEN Shuo, LI Feng-ri, LIU Qiang

2021, 32(8):  2729-2736.  doi:10.13287/j.1001-9332.202108.002

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Leaf mass per area (LMA) is an important parameter in the construction of the ecosystem process models. Accurate prediction of the dynamic validation of canopy LMA is of significance to improve the accuracy of ecosystem process models. We conducted vertical whorl-by-whorl sampling and analyzed LMA in different seasons for Larix olgensis plantation in Maoershan in Shangzhi, Heilongjiang Province, China. We analyzed the vertical and developmental variations of LMA and their main effective factors, established the dynamic prediction model of LMA for young L. olgensis plantation. The results showed that the LMA decreased with the increases of relative depth into crown (RDINC) in the vertical direction of the crown. The range of LMA in the vertical direction after leaf expanded was significantly larger than that during leaf expanding. During the different development periods of leaves, LMAs increased first and then remained stable, and this trend gra-dually weakened with the increases of crown depth. The R_a² values were lower than 0.6 when RDINC or DOY were used as the single variable to model LMA, but were increased by 0.19 when both of them being used, and the model performed well in validation (ME=0.54 g·m^-2, MAE=5.74 g·m^-2). LMA varied across different crown whorls and different leaf development periods. The LMA model constructed with RDINC and DOY could well describe the vertical and temporal variations of LMA. The simulation of crown LMA provided a basis for clarifying crown development and a foundation for the establishment of ecological process model.

Species composition and community structure of warm temperate deciduous broadleaved forests in Huangguan of Qinling Mountains, China

HE Chun-mei, LIU Run-qing, YANG Zhi-chun, YIN Qiu-long, JIA Shi-hong, LUO Ying, HAO Zhan-qing

2021, 32(8):  2737-2744.  doi:10.13287/j.1001-9332.202108.001

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The Qinling Mountain is a natural boundary between warm temperate zone and subtropical zone. While the China Forest Biodiversity Monitoring Network (CForBio) have basically covered most of the climate regions in China, few plots were located in the climate transition zone. Following the field protocol of CForBio and the Center for Tropical Forest Science (CTFS), a 25 hm²(500 m×500 m) forest plot was established in Huangguan Nature Reserve in Shaanxi Province, China, in 2019. In this study, we analyzed species composition, flora characteristics, diameter class structure, and spatial distribution patterns of dominant tree species based on the data of all woody species with a diameter at breast height (DBH) ≥1 cm. The results showed that there were 75137 woody individuals with DBH ≥1 cm in the plot (95679 when including branching individuals), belonging to 121 species, 83 genera and 44 families. The flora type at the genera level was mainly temperate, accounting for 71.1% of the total genera, and mixed with some tropical components. The dominant species in the community were obvious, with the number of individuals in the top 5 species exceeding 40% of the total number of individuals, the number of individuals in the top 50 species accounting for 95% of the total number of individuals, and the number of individuals in the remaining 61 species being less than 5% of the total. The diameter distribution of all woody indivi-duals in the plot was inverted ‘J’ type. Spatial distribution patterns varied across the four most abundant species with importance value >5. The degree of aggregation within species decreased with the increases of scales, while the spatial distribution of different species was affected by environmental heterogeneity. Warm-temperate deciduous broadleaved forest in Qinling Mountains had abundant species, stable community structure and good regeneration, reflecting the typical characteristics of the transition from warm temperate zone to subtropical zone. Environmental heterogeneity might be an important factor affecting the spatial distribution of tree species in the plot.

Spatial distribution and associations of dead woods in natural spruce-fir secondary forests

CHEN Ke-yi, ZHANG Hui-ru, ZHANG Bo, HE You-jun

2021, 32(8):  2745-2754.  doi:10.13287/j.1001-9332.202108.003

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To reveal the community succession rule of natural secondary forest, we investigated basic characteristics and coordinates of each tree (DBH≥1 cm) within a plot (100 m×100 m) using the adjacent grid method and examined the distribution pattern and spatial associations of dead woods in a natural spruce-fir secondary forest in Jingouling Forest Farm, Wangqing Forestry Bureau, Jilin Province, China. The results showed that the diameter class distribution of dead woods showed the pattern of left single-peak curve, while the logs showed the pattern of multi-peak curve. The relationship between the abundance of dead woods and the standing individuals of a particular species was inconsistent. There was a significant negative exponential relationship between the number of dead woods and mixing degree of trees. The distribution of dead woods was concentrated at the 0-8 m scale. With the increases of scale, it gradually changed to random or uniform, with the random distribution being dominant. The aggregation distribution of dead woods with middle (10 cm≤DBH＜20 cm) and small (1 cm≤DBH＜10 cm) DBH was the main reason for the aggregation distribution of dead woods at small scale below 8 m. The spatial associations between dead woods and stan-ding trees at different diameter classes were significantly different. The relationship between dead woods and saplings (1 cm≤DBH＜5 cm) was closely correlated. The dead woods with large DBH and saplings showed a significant positive association at 2-25 m scale. There was no spatial association between dead woods and small trees (5 cm≤DBH＜15 cm). At the 0-3 m scale, there was a positive association between the middle trees (15 cm≤DBH＜25 cm) and dead woods of small and middle DBH. At the 9, 11-14 and 15, 42-45 m scales, dead woods of small and middle DBH were significantly negatively associated with large trees (DBH≥25 cm). In conclusion, biological traits, diameter class distribution, and spatial distribution affected the abundance and diameter class distribution of dead woods. The species with low mixing degree tended to have more dead woods. The diameter and scale would affect the spatial distribution of dead woods. The spatial correlation between dead woods and standing trees varied across diameter classes and scales.

Species-habitat association of a deciduous broadleaved forest in the subtropical and tempe-rate transition zone

ZHU Wen-ting, XIE Feng-lin, LI Tao, HE Nian-jun, ZHANG Ke-rong, ZHANG Quan-fa, DANG Hai-shan

2021, 32(8):  2755-2762.  doi:10.13287/j.1001-9332.202108.009

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The species-habitat association analysis facilitates a better understanding of species coexis-tence and community assembly. Here, all trees in a 25-hm² broadleaved deciduous forest plot in the Qinling Mountains of North-central China were classified into three life stages (i.e., seedling, sapling, and adult). The Torus-translation test was used to examine the species-habitat association. The results showed that the association of species with habitats varied across different species. Most species were significantly associated with high slopes, 95.7% of which showed negative association. 89.5% and 90.9% of tree species were negatively associated with low slopes and ridges, respectively. Most species had positive association with high valley, with only one negative association (0.03%). There were 80, 44 and 23 significant associations with habitats at seedling, sapling and adult stages, respectively, indicating that a greater dependence of seedlings on habitat. 38 species at seedling stage and 25 species at the sapling stage were associated with at least one habitat type, while only 17 species at the adult stage were significantly associated. The effects of habitat on species varied across life stages, showing a weaker species-habitat association at the later stage. Due to the specific environmental demands, most species showed different habitat preferences across life stages.

Clarifying the factors affecting Larix gmelinii forest regeneration based on structural equation model

DONG Ling-bo, TIAN Dong-yuan, CHEN Ying, LIU Zhao-gang

2021, 32(8):  2763-2772.  doi:10.13287/j.1001-9332.202108.010

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Based on data from 49 plots of natural Larix gmelinii forests in Cuigang Forest Farm of Xinlin Forestry Bureau, Daxing’anling Mountains, China, we used 37 measurable variables that mainly focused on stand non-spatial structure, stand spatial structure, species diversity, soil condition, and site condition to construct the structural equation model of natural regeneration densities and size diversities (i.e., height and ground-diameter). The direct, indirect, and total influence coefficients of each path were quantified to extract the critical and controllable factors that influence regeneration density and diversity of natural L. gmelinii forests, which would help implement sustainable forest management. The results showed that the effects of various latent variables on rege-neration density were following an order as: stand non-spatial structure (-0.410) > species diversity (0.380) > soil condition (0.250) > site condition (0.249) > stand spatial structure (0.197), while the order were changed as: soil condition (0.778) > site condition (0.748) > stand spatial structure (0.684) > stand non-spatial structure (0.287) > forest diversity (0.105), when evaluated on the regeneration diversity. Generally, the critical and controllable factors affecting rege-neration quantity and diversity were soil pH, total potassium concentration, species diversity, tree height diversity, uniform angle index and stand volume per hectare. In the management, suitable thinning treatments or replanting broadleaved trees were recommended for optimizing and adjusting species composition, species diversity, soil pH and nutrition, which would promote natural regene-ration.

Establishment of an indicator system for comprehensive assessment on terrestrial biodiversity in China

WANG Qi, SHI Na-na, HAN Yu, XIAO Neng-wen

2021, 32(8):  2773-2782.  doi:10.13287/j.1001-9332.202108.004

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The comprehensive evaluation of terrestrial biodiversity is a key basic work for biodiversity protection. Clarifying the status, trend, and driving factors of biodiversity is premise and necessary for formulating policies and measures of biodiversity protection. At present, there is no unified indicator system for the comprehensive assessment of terrestrial biodiversity in China. We constructed a comprehensive assessment indicator system of terrestrial biodiversity in China, by combining the Aichi biodiversity targets of the Convention on Biological Diversity and the sustainable development goals of the United Nations, learning from the development trend of biodiversity assessment in the world, and following the Pressure-State-Response framework. A total of 22 indicators were obtained, including eight status indicators, seven pressure indicators, and seven response indicators. The correlation and accessibility of the indicators were analyzed. These indicators could be applied to not only an independent assessment for biodiversity status, threatened and protection effectiveness, but also for the comprehensive assessment of terrestrial biodiversity to optimize and adjust priority protection areas and protection measures. Our results would provide a technical support for calculating green GDP and formulating regional ecological compensation policies.

Effects of long-term nitrogen addition on the nitrogen pools in a meadow steppe ecosystem

GENG Qian-qian, WANG Yin-liu, NIU Guo-xiang, WANG Nan-nan, HASI Muqier, LI Ang, HUANG Jian-hui

2021, 32(8):  2783-2790.  doi:10.13287/j.1001-9332.202108.005

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Increasing atmospheric nitrogen (N) deposition greatly affects species diversity, productivity, and stability of ecosystems. It is thus of the great importance to understand how grassland N pools respond to the increased atmospheric N deposition. This study was conducted in a meadow steppe in Erguna, Inner Mongolia, China. There were six levels of N addition (i.e., 0, 2, 5, 10, 20 and 50 g·m^-2·a^-1) and two levels of mowing (i.e., mowing and unmown). Samples of aboveground tissues of dominant plant, root, aboveground litter, and soil to the depth of 100 cm were collected in the seventh year after treatments. The N content was measured and the N pool was calculated. The results showed that N addition significantly increased the N content of aboveground plant tissues and litter, as well as N pools of Leymus chinensis, plant community, litter and ecosystem. Mowing significantly increased the N content of L. chinensis leaf and litter, but reduced N pools of L. chinensis, plant community and litter, and did not affect their responses to N addition. There was a significant interactive effect between mowing and N addition on plant community N pool. High levels of N addition in the unmown treatment led to more N stored in the litter pool, with the saturation threshold for the plant community N pool occurred at 10 g·m^-2·a^-1. Under mowing treatment, the plant community N pool increased with the increasing N addition, and more N stored in plant community N pool after mowing. Mowing could alleviate the negative impacts of increasing N deposition on biodiversity and ecosystem stability, and extended postponing the occurrence of ecosystem N saturation induced by increasing N deposition.

Geographical variation of growth traits among different Quercus acutissima provenances

YUAN Hai-jing, CHENG Xiang-rong, YU Mu-kui, WANG Yang-dong, TAI Jian-wu, ZHANG Chun-xiang

2021, 32(8):  2791-2799.  doi:10.13287/j.1001-9332.202108.007

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The variations in plant growth of 32 Quercus acutissima provenances in three sites (Yongfeng, Jiangxi; Kaihua, Zhejiang and Chuzhou, Anhui) were studied. The AMMI model was used to analyze the stability of growth traits and to select the best provenances. The results showed that tree height, diameter at breast (ground) height, and aboveground biomass (AGB) per individual of the provenances were significantly different in the three sites. The AGB per individual was significantly affected by site, provenance, and the interaction of provenance × site. Site had the greatest impact on the variation of tree growth, followed by provenance and provenance × site. The growth performance of these superior provenances in different sites varied greatly in the seedling stage (1-3 years old) and young forest stage (4-11 years old). Based on the AGB per individual in the 11st year, the best provenances were selected in each site. Seven superior provenances of Yongfeng, Jiangxi were selected, with the average AGB per individual increased by 15.6%-57.8% compared with the ave-rage value. Seven superior provenances of Kaihua, Zhejiang were selected, with the average AGB per individual increased by 19.2%-45.2%. Eight superior provenances of Chuzhou, Anhui were selected,with the average AGB per individual increased by 24.9%-63.3%. According to the growth performance and stability, four superior provenances were selected to develop short-rotation charcoal forest cultivation across three sites, with an average AGB per individual of 36.55 kg and an average stability parameter of 0.97.

Effects of chemical fertilizer reduction combined with organic fertilizer on the yield, quality, and pharmacological activity of Chrysanthemum morifolium

XU Yang, LIU Yin, PENG Zheng, GUO Lan-ping, LIU Da-hui

2021, 32(8):  2800-2808.  doi:10.13287/j.1001-9332.202108.024

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In this study, five different organic and chemical fertilizer treatments (100% chemical fertilizers and 14%, 28%, 56%, and 84% organic fertilizers instead of chemical fertilizers) were set up to examine their effects on agronomic characteristics, yield, mineral nutrient absorption and effective component content of Chrysanthemum morifolium. We used the microplate reader and MTT kit to detect the antioxidant activity of C. morifolium water extract under different treatments and its protective effect on LO2 hepatocytes which were damaged by H₂O₂. The results showed that chemical fertilizer combined with organic fertilizer could ensure the yield of C. morifolium. Moreover, the yield of C. morifolium increased by 8.3% treated with low proportion of chemical fertilizer reduction combined with organic fertilizer (14% organic fertilizer instead of chemical fertilizer). The contents of N and Mg elements in C. morifolium flowers showed an upward trend with increased replacement ratio of organic fertilizer, while the contents of Ca and P reached the maximum value when C. morifolium were treated with 56% and 28% organic fertilizer substitution, respectively. In addition, the contents of chlorogenic acid, luteolin and 3,5-O-dicaffeoylquinic acid in flowers was raised by 3.3%-12.8%, 15.7%-30.1% and 9.5%-29.7%, respectively, when C. morifolium were treated with gradually increasing ratio of organic fertilizer to chemical fertilizer. Furthermore, the antioxidant activity of C. morifolium water extract first increased and then decreased with elevated replacement ratio of organic fertilizer. The C. morifolium water extract could significantly improve the survival rate of H₂O₂-damaged LO2 hepatocytes. The survival rate of H₂O₂-damaged LO2 hepatocytes reached as high as 91.2% treated with C. morifolium water extract under the treatment of 28% organic fertilizer instead of chemical fertilizer cultivated C. morifolium, showing a significant increase compared to the model group. Based on the comprehensive indices of yield, nutrient absorption, active ingredient content, antioxidant activity in vitro, the protective effect on H₂O₂-damaged LO2 hepatocytes and the ecological friendly characteristics of organic fertilizer, we suggested that the quality of cultivated C. morifolium was the best under the application of 28% organic fertilizer instead of chemical fertilizer.

Construction and quality evaluation of strawberry seedling index model

GONG Bin-bin, WU Xiao-lei, ZHANG Bin, CHEN Yi-zhuo, BIAN Xin-yu, JI Ri-zhai, GAO Hong-bo

2021, 32(8):  2809-2817.  doi:10.13287/j.1001-9332.202108.025

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With the development of strawberry cultivated area in China, the demands for high-quality strawberry seedlings are increasing year by year. The research on the evaluation index of strawberry seedlings is needed to ensure the quality of the seedlings. This study aimed to establish an optimal index model of strawberry seedlings to improve the accuracy of seedlings evaluation. In this study, 320 seedlings of ‘Benihoppe’ strawberry seedlings growing for 40 days were taken as the materials. Based on the determination of 16 individual indicators including the growth of aboveground and underground parts, fresh weight, and dry weight, we firstly conducted the membership function corresponding to single indicator. Then the comprehensive evaluation index of strawberry seedlings was calculated using weighted fuzzy evaluation method. Furthermore, the key indicators out of the 16 indicators which were filtered out by means of the principal component analysis method were combined into different index models of strawberry seedlings. The correlation analysis between the comprehensive evaluation index and seedling index models was done and finally the optimal seedling index model was selected and verified. The results showed that there were significant differences in 16 indices of 320 randomly selected strawberry seedlings. The comprehensive evaluation index of strawberry seedlings was in the range of 0.165-0.817, indicating that the comprehensive evaluation index could totally reflect the quality of seedlings and could be used as the evaluation basis. The 16 individual indices of strawberry seedlings were classified into three principal components, including aboveground related indicators, underground related indicators, and the pigment indicators. The cumulative contribution rate of three principal components was 79.7%. Twenty-seven seedlings index models were combined by randomly selecting three indices with a large contribution value from each principal component. Five strawberry seedlings index mo-dels were selected from 27 models due to the highest correlation with the comprehensive evaluation index. Among them, the model “aboveground dry weight×root surface area×chlorophyll a” was identified as the optimal one to evaluate the quality of strawberry seedlings, due to the highest correlation with the comprehensive evaluation index. The correlation coefficient of between strong seedling index and comprehensive evaluation index in three strawberry variety ‘Benihoppe’, ‘Kantoseika’ and ‘Sweet Charlie’ were 0.879, 0.924, and 0.975, respectively. According to the comprehensive evaluation index, the quality of strawberry seedlings were classified into three grades: grade Ⅰ (comprehensive evaluation index ≥0.5, seedling index ≥4.0) with high-quality seedlings; grade Ⅱ (comprehensive evaluation index 0.3-0.5, seedling index 0.5-4.0) with qualified seedlings; grade Ⅲ (comprehensive evaluation index ≤0.3, seedling index ≤0.5) with weak seedlings. The results provided a theoretical basis and scientific method for the evaluation of the health status of strawberry seedlings or other fruits and vegetable seedlings.

Status of soil fertility, nutrient balance, and environmental risk assessment in yam production of North China Plain

WANG Dong, NIU Shao-bin, XU Hua-sen, ZHAO Wei-peng, YANG Xue-zhen, LI Wen-chao, MA Wen-qi, SUN Zhi-mei

2021, 32(8):  2818-2828.  doi:10.13287/j.1001-9332.202108.026

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Taking the main production area of yam in North China Plain as the research area, we analyzed the status of soil fertility and fertilizer application in yam production through field investigation and tracking monitoring, examined soil nutrient balance using the input-output model of nutrients in agricultural system, and assessed the environmental risks in the yam planting system. The results showed that: 1) the contents of soil organic matter and total N were extremely low, and the contents of available P and available Zn were both low; both nitrate and available Cu contents were at the middle level, the contents of soil slowly available K, available S, and exchangeable Ca and Mg were all extremely high, the contents of available K, available Fe, and available Mn were all at high level; 2) The nitrogen (N), phosphorus (P₂O₅), and potassium (K₂O) inputs were 575-943 kg·hm^-2, 341-981 kg·hm^-2, and 655-1219 kg·hm^-2 during the whole growth period of yam, with chemical fertilizer accounting for 83.0%, 88.6%, and 91.3%, respectively; The input imbalance between organic and inorganic fertilizer, as well as the excessive nutrients input were prominent; 3) The surplus rate of soil nitrogen, phosphorus and potassium reached 271.14 kg·hm^-2, 466.34 kg·hm^-2, and 739.97 kg·hm^-2, with corresponding surplus ratio of 48.7%, 258.1%, and 324.5%, respectively, which all exceeded the environmental safety threshold and were classified as moderate risk, severe risk, and severe risk, respectively. The overall environmental risk caused by chemical fertilizer application in yam production had reached severe risk level.

Spatial variations and its influencing factors of soil carbon and nitrogen on the southern foot of Taihang Mountains, China

ZHANG Zhi-hua, ZHANG Jin-hao, SANG Yu-qiang, YANG Xi-tian, WANG De-cai, GUO Jia-wei, BI Hui-tao

2021, 32(8):  2829-2838.  doi:10.13287/j.1001-9332.202108.029

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As an important ecological barrier for the North China Plain, research on the spatial variations of soil nutrients in the southern foot of the Taihang Mountains is of great significance for the forestry ecological construction in this rocky mountainous area. With the typical slopes (the artificial forestland and the natural wild slope) of the southern foot of the Taihang Mountains as the research objects, we used the grid method to arrange sampling points, and combined classical statistics, geostatistics and constrained sorting methods to analyze the spatial variations of soil nutrients. The results showed that: 1) soil total carbon (TC) contents were 6.80-57.05 g·kg^-1, and the total nitrogen (TN) contents were 0.74-3.93 g·kg^-1. The coefficients of variation of both soil TC and TN were 25.0%-52.8%, belonging to the moderate degree of variation, which were caused by the combination of random and structural factors. The spatial aggregation of soil nutrients decreased with increasing lag distances. 2) The contents of soil nutrients had increasing trends from the top to the bottom of the slopes, with high nutrient values appearing at the bottom of the slopes. 3) The soil bulk density, gravel content, vegetation coverage, and soil water content were the main factors affecting the spatial variability of soil TC and TN on the southern foot of the Taihang Mountains. 4) Soil water content was the main factor affecting soil nutrients at the natural wild slope, but not at the artificial forestland.

Estimating average tree height in Xixiaoshan Forest Farm, Northeast China based on Sentinel-1 with Sentinel-2A data

CHEN Yuan-yuan, ZHANG Xiao-li, GAO Xian-lian, GAO Jin-ping

2021, 32(8):  2839-2846.  doi:10.13287/j.1001-9332.202108.013

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Forest resource survey is important for the sustainable development of forest ecosystem in China. The average tree height is a main structural parameter of forest resource survey, and also one of the key parameters with greatest difficulty to obtain. The purpose of this study was to explore the potential of joint active and passive remote sensing technology in estimating forest average height. Taking Xixiaoshan Forest Farm in Linjiang City of Jilin Province as the research area, we used Sentinel-1 SAR and Sentinel-2A data, extracted two backscatter coefficients and eight texture information of Sentinel-1, ten spectral bands and texture information of Sentinel-2A and eleven vegetation index variables, constructed five groups of average tree height estimation models based on above variables and fusion of four variables by multiple linear regression method. We further evaluated the influence of each variable on the inversion accuracy. The results showed that the texture information extracted from the Sentinel-2A spectral band of a single data source variable had a better modeling effect and could be used as effective data to estimate the average tree height. The height estimation model of the integrated four variables was optimal, with a R² vaule of 0.56, a root mean square error of leave-one-out cross-validation of 2.92 m, and a relative root mean square error of leave-one-out cross-validation of 21.5%. The forest average height model based on Sentinel-1 and Sentinel-2a characteristic variables could improve the estimation accuracy of forest height, which could be used for regional forest average height estimation and mapping.

Characteristics of water requirement of table grape in the growing season

CHENG Xue, SUN Shuang, ZHANG Zhen-tao, LIU Zhi-juan, YANG Xiao-guang

2021, 32(8):  2847-2856.  doi:10.13287/j.1001-9332.202108.014

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To quantitatively assess the satisfaction degree of precipitation on water requirement of table grape in the main producing areas in China, we analyzed the temporal and spatial variations of precipitation, water requirement and water deficit in different growth stages of table grape based on the 1981-2016 daily meteorological data from 429 meteorological stations in the study region (Jinlin and Liaoning of Northeast China; Shanxi and Hebei of North China; Xinjiang, Gansu, Ningxia and Shaanxi of Northwest China; Sichuan, Guizhou and Yunnan of Southwest China; Jiangsu, Shandong, Zhejiang, Anhui, Fujian, Henan, Hubei, Hunan and Guangxi of Southeast China). Results showed that precipitation in each growth stage showed an increasing trend from north to south and from west to east in the study period. The precipitation in germination-flowering stage was the lowest and showed a decreasing trend. The precipitation in maturation-defoliation stage showed a decreasing trend, while that in flowering-veraison and veraison-maturation stage exhibited an increasing trend. Water requirement of grape exhibited an increasing trend in each growth stage in the study region. Water requirement of grape in Xinjiang and the northern of Gansu Province was the highest. The precipitation could not meet water requirement of grape in Xinjiang, northern Gansu, Ningxia, northern Shaanxi, northern Shanxi, northern Hebei, western Liaoning and western Jilin in each growth stage, as well as northern Yunnan and southern Sichuan during germination-flowering stage. In constrast, water surplus was obvious in the other areas, especially in the southeast and southwest of China. The water deficit of grape showed an increasing trend during the germination-flowering and maturation-defoliation stage, while that during flowering-veraison and veraison-maturation stage showed a decreasing trend.

Growth response to climatic factors and drought events in Quercus variabilis trees of different diameter classes at south aspect of Taihang Mountains, China

JIA Han-sen, GAO Jun, ZHANG Jin-song, MENG Ping, SUN Shou-jia

2021, 32(8):  2857-2865.  doi:10.13287/j.1001-9332.202108.012

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To explore the effects of diameter class on the climate-growth relationship of trees, the width chronologies of ringwood, earlywood, and latewood of Quercus variabilis were established in the low altitude area of the south aspect of the Taihang Mountains. We estimated the sensitivity of radial growth of two diameter classes of Q. variabilis plantation to climate. The effects of drought events on Q. variabilis plantation was quantified by superimposed time analysis. Under climate change, we aimed to provide reference data for sustainable management of Q. variabilis. Our results showed that the mean sensitivity of ringwood and latewood of large diameter classes were higher than small diameter classes. The mean sensitivities of earlywood of small diameter classes were higher than large diameter classes. The latewood was the most sensitive component of tree-ring. The responses of the standard chronological indices of two diameter classes to climate factors were similar. The growth of ringwood and latewood of small diameter classes were more sensitive to the climatic factors from June to August. The earlywood was more sensitive to the climatic factors before the growing season (from January to February). Furthermore, the earlywood of large diameter classes was more sensitive to the climatic factors of the last year, with a stronger hysteresis effect. It suggested that Q. variabilis was sensitive to drought. The radial growth of Q. variabilis of ringwood and latewood in drought year was significantly lower than that of last year. The reduction of Q. variabilis with large diameters was higher than that of small diameters, but with higher growth recovery degree after drought.

Spatial-temporal differentiation of mountain-water-forest-farmland-lake-grass system in Qinghai area of the Qilian Mountain National Park, China

FU Jian-xin, CAO Guang-chao, GUO Wen-jiong

2021, 32(8):  2866-2874.  doi:10.13287/j.1001-9332.202108.015

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Higher and more precise requirements are critically needed for the protection, regulation, and restoration of ecological environment in the Qilian Mountain National Park after it is classified as a national park system pilot in China. Based on remote sensing data in 1980-2018, the spatial pattern map of mountain-water-forest-farmland-lake-grass system was constructed to analyze its spatial-temporal variations in the general control area and core conservation area in Qinghai area of the Qilian Mountain National Park. The results showed that grasslands, with an area of 8174.93 km², were the main landscape in the park, and that grassland area in the core conservation area was 1.2 times as that of the general control area. The bare exposed rocks, a major type of unused land, accounted for 86.7% and 79.4% of the unused land in the core conservation area and the general control area, respectively. Forest area in the general control area was larger than that in the core conservation area. Water area in the core conservation area was 4.9 times as large as that in the general control area, with 90.4% of which being dominated by permanent glaciers and snowfields. The drylands were mainly concentrated in the general control area. From 1980 to 2018, the water area was decreasing and had been reduced by 186.75 km². The area of permanent glaciers and snowfields decreased the most, with a drop of 12.05 and 175.88 km² in the general control area and the core conservation area, respectively. The area of forests and grasslands were enlarged constantly. The changes of high-, medium-, and low-coverage grasslands in the core conservation area were greater than that in the general control area, which were the most significant during 1990-2000. Moreover, the degradation of high- and medium-coverage grasslands in the general control area as well as high- and low-coverage grasslands in the core conservation area was observed from 1980 to 2018. The area of bare exposed rocks was on the rise, while the permanent glaciers and snowfields displayed a decreasing trend. The permanent glaciers and snowfields and the bare exposed rocks exhibited the most obvious changes in the park. The glaciers in the core conservation area retreated remarkably faster than those in the general control area, which were transformed into the bare exposed rocks mainly in 1980-1990 and 2000-2010.

Developmental characteristics of biological soil crusts and their effects on soil water infiltration on karst slope

ZHANG Si-qi, ZHANG Ke-li, CAO Zi-hao, ZHU Tong, WEI Meng-yao

2021, 32(8):  2875-2885.  doi:10.13287/j.1001-9332.202108.011

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Biological soil crusts (BSCs), as a pioneer for vegetation restoration and crucial component of surface landscape, greatly affect land surface process. To explore the development of BSCs and its effects on soil water infiltration in karst region, we investigated the development of BSCs and analyzed the infiltration processes with different BSCs coverages (0, 28%, 40%, 70%, 97%) and rainfall intensities (42 and 132 mm·h^-1) in simulating rainfall experiments on a typical karst slope. The results showed that there were significant differences in the development of BSCs for different land use types, whereas the spatial variation of BSCs development on the slope was not obvious under the same land use type. Compared to the bare plot, the presence of BSCs significantly increased surface roughness, the initial runoff generation time, and soil water infiltration. In the cases of light (42 mm·h^-1) and intensive (132 mm·h^-1) rainfall, the initial infiltration rate of BSCs covered plots were 1.7-1.9 times and 1.2-1.9 times as that of bare plot, while the average infiltration rate in BSCs covered plots were 2.5-3.0 times and 1.4-3.3 times as that of bare plot, respectively. The BSCs coverage was significantly positively correlated with the initial runoff production time. The critical values of facilitating infiltration of BSCs coverage were between 65% and 70% under the test rainfall intensities. For heavy rainfall events, the inhibiting effects of BSCs on surface runoff were weakened. Horton model was the most reliable one for describing the infiltration process on karst slope with BSCs, followed by Kostiakov model and Philip model. In conclusion, the spatial variability of BSCs development on the karst slope was higher. The presence of BSCs had a significant effect on soil permeability in karst region.

Erosion process of loess slope and influencing factors in the loess hilly-gully region, China

LIU Ran, YU Xin-xiao, CAI Qiang-guo, SUN Li-ying, FANG Hai-yan, JIA Guo-dong, HE Ji-jun

2021, 32(8):  2886-2894.  doi:10.13287/j.1001-9332.202108.016

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Rainfall intensity, slope length, and slope gradient are the important factors affecting runoff and sediment yield. In order to quantitatively analyze the effects of rainfall intensity, slope length, and slope gradient on the erosion process of Ansai loess slope in loess hilly and gully region, we analyzed the variation of runoff and sediment yield on Ansai loess with two slope lengths (5, 10 m), three slopes (5°, 10°, 15°) and two rainfall intensities (60, 90 mm·h^-1) in an indoor simulated rainfall experiment. The results showed that the initial runoff generation time decreased with the increases of slope length, though the overall change was not significant. The initial runoff generation time decreased with the increases of rainfall intensity. Compared with the intensity of 60 mm·h^-1, the initial runoff generation time decreased by 5.7-18 min under the intensity of 90 mm·h^-1. Among them, the runoff initiation time on the slope of 10° was the fastest. With the duration of rainfall, runoff yield rate increased rapidly at first, and then gradually fluctuated around a certain value. The sediment yield rate increased rapidly in a short period of time at the initial stage of runoff generation, and then decreased after reaching the maximum, and being gradua-lly stable. The rates of runoff and sediment yield increased with the increases of slope length and rainfall intensity, but the law of change with slope was not obvious. With the increases of rainfall intensity, slope length and gradient, the total sediment yield increased accordingly. Under the rainfall intensity of 90 mm·h^-1, the slope surface with the length of 10 m and slope of 15° generated rill, leading to the highest total erosion amount (11885.66 g). Under the rainfall intensity of 60 mm·h^-1, the erosion amount per unit area decreased with the increases of slope length, and there was a critical erosion slope length in 5-10 m slope section. Slope length, slope and rainfall intensity all played a promoting role in runoff process. Rainfall intensity, slope length, and their interaction contributed more to runoff yield rate and total erosion amount. Rainfall intensity contributed the most to runoff yield rate, with a contribution rate of 49.8%. The contribution rate of slope length to the total erosion was the largest, which reached 37.8%.

Variation in fractional vegetation cover and its attribution analysis of different regions of Beijing-Tianjin Sand Source Region, China

MENG Qi, WU Zhi-tao, DU Zi-qiang, ZHANG Hong

2021, 32(8):  2895-2905.  doi:10.13287/j.1001-9332.202108.018

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Based on the MODIS NDVI data from 2000 to 2018, we estimated the fractional vegetation cover (FVC) using the dimidiate pixel model and analyzed the spatiotemporal characteristics of FVC in the Beijing-Tianjin sand source region (BTSSR). The geographical detector model was used to estimate the impacts of natural and human factors on FVC spatial distribution at the regional scale. The results showed that the FVC of the BBTSR showed an increasing trend from 2000 to 2018, with an annual growth rate of 0.013·(10 a)^-1 and a vegetation increase rate of 8.2%. The area with high FVC was concentrated in the Yanshan Mountain water source protection area, followed by the pastoral transitional zone desertified land control area and the Otindag sandy land area. The area with poor FVC was concentrated in the northern arid grassland area. The explanatory power of driving factors to FVC varied across different regions. Among the natural factors, annual precipitation was the main driving factor for the spatial distribution of FVC in the northern arid grassland area, the Otindag sandy land area and the Yanshan Mountain water source protection area. Slope was the main driving factor for the spatial distribution of FVC in the pastoral transitional zone desertified land control area. Among different human activities, the number of large livestock at the year-end was the main driving factor controlling the spatial distribution of FVC in the northern arid grassland area and the pastoral transitional zone desertified land control area, while population density was the main driving factor controlling the spatial distribution of FVC in the Otindag sandy land area and the Yanshan Mountain water source protection area. There were regional differences in the influen-ce of other factors on FVC spatial distribution. The results of the interaction detector showed that the two-factor interactions were mainly the double-synergy and nonlinear synergy. The interaction of human activities with annual precipitation and slope could more fully explain the spatial variations of FVC. The range of suitable vegetation growth identified by the risk detector was the area with annual precipitation of 316.4-486.0 mm, average relative humidity of 48.4%-57.6%, and average annual temperature of 2.5-7.9 ℃, while other driving factors were different in different zones.

Diagnosis of eco-environmental quality in the Keluke Lake basin, China

WEN Guang-chao, SUN Shi-kui, LI Xing, XIE Hong-bo

2021, 32(8):  2906-2914.  doi:10.13287/j.1001-9332.202108.019

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In order to clarify the eco-environmental quality and its evolution characteristics of Keluke Lake basin, we selected 15 factors of physical geography, meteorology, land use/cover and social economy using comprehensive investigation, remote sensing interpretation and inversion, statistical analysis and other technical means, based on the relevant theories of environmental ecology. We used factor analysis and entropy method to calculate the index weight, constructed watershed soil quality model and ecological environment quality diagnosis model, and analyzed the changes of soil and eco-environmental quality in the Keluke Lake basin in 2000, 2005, 2010 and 2015. The results showed that the average eco-environmental quality in four periods was 21, 47, 54, and 72, showing a stable upward trend. The eco-environmental quality level changed from poor to good, while soil quality was at the middle level. Spatially, the eco-environmental quality of the northern mountainous area, the downstream wetland and the surrounding area of the river improved significantly. The change of eco-environmental quality was a result of human activities and natural factors. Soil quality and lake area were key factors indicating the eco-environment of the Keluke Lake basin. The minimum ecological water demand of the Keluke Lake was the basic guarantee to maintain the benign development of the eco-environment of the lake basin.

Spatial distribution of human activity intensity in Yunnan-Guizhou Plateau Wetland scenic area: A case study of Lashihai watershed in Yunnan Province, China

LI Hai-ping, WANG Na-ping, DAI Yu-ting

2021, 32(8):  2915-2922.  doi:10.13287/j.1001-9332.202108.017

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Human activity intensity is mostly used to quantify the degree of human influence on natural systems, with obvious spatial variability. With Lashihai watershed in Yunnan Province as an example, we used SPOT remote sensing images to update land use data, and obtained a comprehensive index of land use intensity after gridding by assigning weights to different land types, which was considered as the basic human activity intensity. The local tourism activities (horseback riding and boating) were also included. The horseback riding and boating were spatially quantified according to the location of horse farms and the abundance of horses and boats which were superimposed with the basic human activity intensity on the spatial scale of 100 m×100 m to obtain a more accurate comprehensive human activity intensity and to analyze the spatial variations. The results showed that the gridding and the kernel density analysis improved the accuracy of spatial analysis and reflected the spatial superposition and diffusion effects. In the comprehensive human activity intensity map of Lashihai watershed, the highest intensity value of water area was at the mouth of the sea, the lowest intensity value was at the center of the sea, and the overall trend of intensity gradually decreased from the surrounding to the middle. The land settlement had the highest intensity, the intensity value of the agricultural land gathering area was at the middle level, and the intensity of human activities in the forestry area of higher altitude was lower. The comprehensive human activity intensity in the water area of the Lashihai watershed varied most obviously, and differed greatly from the basic human activity intensity. Although there were many local characteristic tourism activities in Yunnan-Guizhou Plateau Wetland scenic area, but their land use types did not change. We need to take them into account when quantifying the intensity of human activities.

Aerosol salt damage is the main problem of landscaping in the coastal areas of southern China

CAO Jian-ting, FAN Zhi-yang, HUANG Jian-ming, CHEN Yang-fang, CHEN Zi-liang, WANG Wen-qing

2021, 32(8):  2923-2930.  doi:10.13287/j.1001-9332.202108.035

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Both the growth and survival of landscape plants are difficult due to the harsh natural conditions in coastal areas of southern China. Many plants suffer from symptoms of salt damage. Different from the damages by salt in the soil, the symptoms of windblown salt are damage to young shoots and leaves. Plants at the windward side are damaged more than the leeward side. These cha-racteristics imply that the damage is due to salt in aerosols instead of salt in the soil. To test this hypothesis, we measured plant growth, soil and climate factors in 24 frontline coastal counties and cities of China. The results showed that the first-line coastal plants showed strong symptoms of salt damage, especially in the Taiwan Strait area (85.4% belonged to desalinized soil), and that the damage level was highly correlated with wind speed. Our results confirmed that aerosol salt is the major cause of plant damage in the coastal areas of southern China. We constructed the first distribution map of salt damage along frontline coastal regions of southern China and proposed methods for diagnosing aerosol salt damage. Selecting and configuring aerosol salt-tolerant plants, greening engineering measures, and follow-up maintenance were suggested for improving the overall effect and level of landscaping in the coastal areas of southern China.

Effects of growth-promoting strain Mycena sp M23 on photosynthesis of Aronia melanocarpa

SHAN Ting-ting, ZHOU Li-si, LI Bing, CHEN Xiao-mei, GUO Shun-xing, LI Fei, LU Wei

2021, 32(8):  2931-2938.  doi:10.13287/j.1001-9332.202108.032

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The agronomic traits, chlorophyll content, physiological indices of Aronia melanocarpa were compared in five treatments, namely negative control (CK), positive control (PCK), low dose of microbial inoculant (T₁, 50 g per seedling), moderate dose of microbial inoculant (T₂, 100 g per seedling), high dose of microbial inoculant (T₃, 200 g per seedling) in field. The diurnal variation of net photosynthetic rate was measured by Li-6400 portable photosynthesis system. The diurnal variation of net photosynthetic rate (P_n) of A. melanocarpa showed a pattern of bi-modal curve with photosynthetic “noon break” phenomenon, which occurred at 1:00 pm. At that time, stomatal conductance (g_s) and transpiration rate (T_r) of A. melanocarpa showed a dramatic decline, while intercellular CO₂ concentration (C_i) significantly rose. It was a photosynthetic “noon break” phenomenon caused by non-stomatal limitation. Application of inoculant to A. melanocarpa successfully avoided the photosynthetic “noon break” phenomenon. Compared with average value of CK and PCK, P_n, g_s, T_r, water use efficiency (WUE) and light utilization efficiency (LUE) of inoculation groups increased by 113%, 91%, 50%, 48% and 117% at 1:00 pm. Daily mean of P_n, g_s, T_r and LUE of inoculation group was 1.5, 1.9, 1.4 and 1.5 times as that of average value of CK and PCK. The inductive effect of high dose of microbial inoculant treatment was the best among inoculation treatments, with the seedling height 1.2 times as that of the moderate and low inoculant groups. All growth indices, photosynthetic parameters and resistant physiological indices of high dose group were superior to other groups. Our results suggested that fungi M23 could improve the adaptability of A. melanocarpa to environmental stresses and promote its growth by increasing photosynthesis, with the inductive effect of high dose being the best.

Effects of exogenous microorganisms on seedling growth and soil microbial community of Casuarina equisetifolia

BAI Ying, ZHOU Liu-ting, ZHANG Chen, LUO Yang, ZHAO Yan-lin, LIN Wen-xiong, WU Ze-yan

2021, 32(8):  2939-2948.  doi:10.13287/j.1001-9332.202108.037

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With a pot experiment, the Biolog microplate and phospholipid fatty acid (PLFA) technology were used to explore whether the application of bacteria, Bacillus amyloliquefaciens (YB706) and Burkholderia (BK8), could improve the soil nutrient, microbial community and growth of Casuarina equisetifolia. The results showed that the concentrations of soil alkali-hydrolyzed nitrogen and available phosphorus of C. equisetifolia treated with YB706 and BK8 increased significantly compared with the control (CK), but the concentrations of total nitrogen, total phosphorus, total potassium and available potassium changed little, plant height increased by 59.1% and 63.9%, respectively, and the chlorophyll content of plant treated with BK8 increased by 81.9%. The average well color development values showed a pattern of YB706>CK>BK8. The utilization rate of different carbon sources showed the same trend except the amino acids. Both YB706 and BK8 treatments significantly increased the richness and quantity of soil microorganisms. The PLFA of all kinds of microorganisms was BK8>YB706>CK except actinomycetes. The ratio of soil fungi to bacteria was increased compared with CK. The Simpson, Shannon, Brillouin and McIntosh indices of rhizosphere soil microbial community in YB706 and BK8 treatments were significantly increased. Our results suggested that application of YB706 and BK8 could improve the growth rate of C. equisetifolia seedlings, effectively increase the contents of soil available nutrients, increase soil microbial diversity, and improve soil microbial environment.

Effects of biochar and biochar compound fertilizer on the communities of nitrifier and denitrifier in a reclaimed soil from coal-mining area

GAO Ke, GUO Zong-hao, XUE Chen, GAO Wen-hui, LIU Yuan, JIANG Li

2021, 32(8):  2949-2957.  doi:10.13287/j.1001-9332.202108.033

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As a new soil amendment strategy, the effects of biochar application on soil microbial community have been reported in literature, but little information is available on the response of nitrogen-related microbial communities to biochar application in the reclaimed soil from coal-mining area. Through an outdoor pot experiment with reclaimed soil from coal-mining area of Huaibei, the effects of biochar and biochar compound fertilizer on nitrifier and denitrifier communities were investigated by real time PCR (qPCR) and terminal-restricted fragment length polymorphism (T-RFLP). There were five treatments: control (CK), NPK fertilizer (CF), biochar compound fertili-zer (BF), 2% biochar and NPK fertilizer (LB), 4% biochar and NPK fertilizer (HB). Results showed that compared with the CK, the treatments CF, BF, LB and HB significantly increased the abundance of ammonia oxidizing archaea (AOA), ammonia oxidizing bacteria (AOB), nirK and nirS genes of denitrifier. Compared with the CF treatment, BF, LB and HB significantly increased the abundance of AOB and nirK genes by 42.9%-82.1% and 33.5%-62.7%, respectively. Results of redundancy analysis showed that soil organic carbon, pH, NH₄⁺-N and available potassium significantly affected AOB community structure, while soil organic carbon concentration, pH and NO₃^--N concentration significantly altered nirK-denitrifier community structure. Therefore, the application of biochar and biochar compound fertilizer could improve soil quality of the reclaimed soil from coal-mining area, and increase the abundances of nitrifier and denitrifier and alter community structure of AOB and nirK-denitrifier.

Changes of soil microbial biomass carbon, nitrogen, and enzyme activities in East Dongting Lake wetlands at different water levels

XIAO Ye, HUANG Zhi-gang, XIAO Han-xi, LI You-feng, PENG Wan-xia

2021, 32(8):  2958-2966.  doi:10.13287/j.1001-9332.202108.036

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We analyzed soil quality based on soil microbial characteristics of three different vegetation types in the wetlands of East Dongting Lake, including Carex tristachya wetland (CTW), Phragmites australis wetland (PAW), and Salix babylonica wetland (SBW). The soil microbial biomass carbon (MBC), nitrogen (MBN) and enzyme activities were measured and the key influen-cing factors were analyzed during the normal, flood, and dry periods. The results showed that: 1) The amounts of MBC, MBN, and the activities of invertase and cellulase (except cellulase of dry season) in 0-10 cm were higher than those in 10-20 cm for all wetlands, while the catalase activity showed an opposite pattern. 2) The amounts of MBC and MBN and the values of MBC/TOC and MBN/TN for the 0-20 cm soil layer of each vegetation type wetland were the lowest in flood period. 3) Soil invertase activity for each vegetation type wetland in the 0-20 cm soil layer peaked in the dry period, while soil cellulase activity peaked in the normal period. The seasonal fluctuation of soil catalase activities in all wetlands were small, with activities being slightly higher in flood period than the other two periods. 4) Among different vegetation types, soil invertase activity of PAW was significantly higher than that of other vegetation types, and cellulase activity of which was the lowest in both normal and flood periods. There was no difference in these two enzymes activities among wetlands during the dry period. The highest soil catalase activity was found in CTW during normal period and in SBW during dry period, respectively, while its lowest value was in PAW during flood period. 5) Soil MBC, MBN and invertase activity were correlated positively with soil TOC, TN and TP, and negatively correlated with soil pH. The activities of soil cellulase and catalase were significantly negatively correlated with TOC, TN, TP and positively correlated with pH. It suggested that the seasonal fluctuation of water level affected soil C, N, P contents and pH values, with consequences on soil MBC, MBN and enzyme activities.

Effects of reductive soil disinfestation during low-temperature stubble free period on the control of watermelon Fusarium wilt

LIU Liang-liang, ZHOU Kai-sheng, HUANG Xin-qi, XIE Yi, ZHANG Yi, LIU Xiao-lin

2021, 32(8):  2967-2974.  doi:10.13287/j.1001-9332.202108.034

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In order to clarify the controlling effect of reductive soil disinfestation (RSD) during low-temperature stubble idle period on watermelon Fusarium wilt, we conducted a pot experiment, containing control (CK), flooded control (FCK), and RSD treatments incorporated with 2% (w/w) alfalfa meal (AL), 0.25% acetic acid (AC), and AL+AC. Real time PCR and Illumian Miseq sequencing were used to determine the abundances of fungi and Fusarium oxysporum as well as fungal community composition. The disease incidence and yield of watermelon were measured. Results showed that the abundance of Fusarium oxysporum and the ratio of Fusarium oxysporum to fungi significantly decreased in the FCK and three RSD treatments, and the disinfestation effects of these treatments ranged from 86.1% to 94.6%. The yield and disease incidence of watermelon significantly increased and decreased in all of the RSD treatments, respectively. There was no significant diffe-rence between FCK and CK treatments. The control efficiencies of Fusarium wilt in AL, AC, and AL+AC were 63.2%, 73.7%, and 94.7%, respectively. The compositions of fungal community in the AL and AC treatments were significantly changed, whereas FCK did not affect fungal community. The relative abundances of dominant fungal genera, such as Zopfiella, Pseudeurotium, Geotrichum, Ascobolus, Westerdykella, and Guehomyces, increased in the RSD treatments. Most of those genera were significantly and negatively correlated with the abundance of Fusarium oxysporum, the ratio of Fusarium oxysporum to fungi, and the disease incidence. In conclusion, RSD treated in the low-temperature stubble free period could effectively control watermelon Fusarium wilt by reshaping fungal community composition.

Effects of above- and below-ground herbivore interactions on interspecific relationship between the invasive plant Alternanthera philoxeroides and its native congener Alternanthera sessilis

SHEN Si, GUO Wen-feng, WANG Wei, LI Xiao-qiong

2021, 32(8):  2975-2981.  doi:10.13287/j.1001-9332.202108.038

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Biological invasion is a major threat to global biodiversity. The relative interspecific competition abilities of invasive species compared to those native species determine their invasion success. In this study, we examined the effects of the specialist leaf beetle Agasicles hygrophila and the nematode Meloidogyne incognita on the growth and interspecific relationship between the invasive plant Alternanthera philoxeroides and its native congener A. sessilis. Compared without herbivory, nematode herbivory alone significantly reduced shoot height of A. sessilis by 28.1%, but conversely significantly increased the shoot height of A. philoxeroides by 52.8% and aboveground biomass of A. sessilis by 63.7%. Beetle herbivory alone significantly reduced shoot height of A. sessilis by 40.7%, but did not affect that of A. philoxeroides. The combination of beetle and nematode herbivory significantly reduced shoot height of A. sessilis by 35.3% as well as the belowground biomass of A. philoxeroides by 62.2%, but significantly increased the aboveground biomass of A. sessilis by 69.1%. Herbivore stress did not affect stem diameter, branch number, and root length of both species. The relative neighbor effect index (RNE) of the two species without herbivory were positive, and the RNE value of A. philoxeroides was 21.3% higher than that of A. sessilis. However, the RNE values of A. philoxeroides were negative under all above- and below-ground herbivory treatments. The RNE values of A. sessilis were positive under the beetle or the nematode herbivory alone and negative under the beetle + nematode herbivory combination. These results indicated that above- and below-ground herbivore interactions could change the interspecific relationship between the two species, and in turn might accelerate the invasion of A. philoxeroides.

Combined remediation of polycyclic aromatic hydrocarbons (PAHs) by plant and immobilized bacteria in contaminated soil

LI Na, LIU Rui, TAI Pei-dong, ZHOU Xing-xing, XIAO Yao, LI Ling-mei, HOU Li-qun, ZHENG Ting-yu

2021, 32(8):  2982-2988.  doi:10.13287/j.1001-9332.202108.031

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In this study, three dominant bacteria Cellulomonas flavigena (Ⅰ), Cellulomonas flavigena (Ⅱ), Sphingomonas paucimobilis (Ⅲ) from Fire Phoenix rhizosphere soil were used to develop a multi-microbial agent system. For oil-contaminated soil in the Dagang oilfield, the immobilized test bacteria were inoculated into the Fire Phoenix rhizosphere soil to examine the effects of bacterial agents on polycyclic aromatic hydrocarbons (PAHs)-contaminated soil. The results showed that PAHs degradation was promoted under the ⅠⅢ (with an effective number of viable bacteria of 10⁹ cfu·mL^-1) and ⅠⅡⅢ (with an effective number of viable bacteria of 10⁷ cfu·mL^-1) treatments. The PAHs degradation rates were 32.2% and 41.4%, respectively, being significantly higher than that in the control treatments. The ⅠⅡⅢ treatment significantly promoted the belowground biomass of Fire Phoenix, which was 31.2% higher than that of the control treatment. Our results suggested that the multi-microbial agent constructed by the three dominant bacteria ⅠⅡⅢ could be used as a strengthening method for the remediation of PAHs-contaminated soil by Fire Phoenix, which provided a novel method for microbial enhanced phytoremediation technology.

Reviews

Comparison and application of calculation methods for water consumption of tree transpiration

YAO Yuan, LIU Rui-xuan, ZHANG Sheng, HAN Qing-quan

2021, 32(8):  2989-2998.  doi:10.13287/j.1001-9332.202108.008

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In this study, the concept, research value, and research advances of tree transpiration were concisely narrated. From the perspective of measurement and estimation, we summarized the main calculation methods for water consumption of tree transpiration. By comparing the advantages, disadvantages, applicability, limitations, application status, and applicable scale of different methods, we showed that the measurement methods could be applied to the measurement of water consumption at multiple spatial scales, and that the estimation methods were often applied to the measurement of evapotranspiration at large spatial scales. As the measurement method was the basis of the estimation method, it is necessary to carry out reasonable quality control and evaluation of the measured results of measurement methods, in order to provide data basis for the estimation results of the correction estimation method. Whether it was at a particular large spatial scale or at different spatial scales, the combination of measurement methods and estimation methods could improve the accuracy of evapotranspiration measurement. Improving the accuracy of calculating the dispersion of trees at a large spatial scale in complex underlying surface and harsh climate environments would become a research hotspot but may also be a difficulty in the future. With the continuous progress of science and technology, both measurement devices and methods would be improved, and new methods for accurately measuring the water consumption of forest transpiration would be available.

Current status and research advances of late spring coldness in wheat

CHEN Xiang, YU Min, CAI Hong-mei, WU Yu, ZHANG Le-le, KE Yuan-yuan, XU Hui, LI Jin-cai

2021, 32(8):  2999-3009.  doi:10.13287/j.1001-9332.202108.021

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Low temperature disasters in wheat occur frequently in recent years, due to global warming. Late spring coldness in wheat during jointing-booting stage is one of the important factors limiting the yield and quality of wheat. Here, we summarized the occurrence characteristics (identification, classification, and space-time characteristics) of late spring coldness in wheat, and the effects of late spring coldness on physiological characteristics (leaf, stem, spike, and root), yield and quality of wheat. Furthermore, we reviewed the research progresses on the breeding of late spring coldness tolerant wheat, molecular biology mechanism, the monitoring, early warning and risk assessment of late spring coldness. Finally, future research work on genetic basis of wheat resistance to late spring coldness, evaluation system for wheat damaged by late spring coldness, prevention and control technology system were prospected to provide a theoretical basis for genetic improvement and new cultivation regulation measures of the resistance of wheat varieties to late spring coldness.

Construction methods of urban ecological corridor for birds: A review

TIAN Bei-chen, LI Pei-quan, HUANG Qian-du

2021, 32(8):  3010-3022.  doi:10.13287/j.1001-9332.202108.020

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The ecological corridors considering bird movement characteristics and habitat requirements would mitigate species extinction caused by habitat loss or habitat fragmentation and facilitate species gene dispersal and exchange. These functions may in turn benefit urban residents’ physical and mental health as well as appreciation of real estates. Nonetheless, main ecological corridor construction methods developed by foreign scholars have not internally considered the movement and habitat characteristics of birds, while corridor research for birds by domestic scholars have focused on explorations of foreign technical methods yet lacked enough knowledge on studied birds’ characteristics. Therefore, there is still much room for improvement in the study of urban ecological corridor construction from the perspective of birds. Based on the analyses of domestic and foreign related research from 1975 to 2020, we identified seven corridor construction methods and three corridor optimization methods within which bird ecology can be integrated. The advantages, drawbacks, and applicable scenarios of all the methods were explored accordingly. Finally, we argued that the develop-ment of computational models, which could not only combine bird species’ observation data and spatial movement data with landscape structures but could also possess efficient computation power as well as simulate corridor’s ecological benefits, would be a trend for constructing ecological corridor for birds.

Research status of bioweathering control of stone buildings

LIN Jia-yu, LI Bang-jiang, CHENG Cai, ZHANG Yuan-dong, GAO Min, LONG Ming-zhong

2021, 32(8):  3023-3030.  doi:10.13287/j.1001-9332.202108.039

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Stone buildings exposed to natural environment inevitably subject to various factors. Among which, biodeterioration caused by bacteria, fungi, algae, lichen, and moss is widespread. The long-term cumulative effect of biodeterioration will lead to irreversible changes in the aesthetic characteristics, physical and chemical properties of stone buildings. Therefore, it is necessary to control the biodeterioration of stone buildings. Here, we summarized four traditional methods including heat shock treatments, laser and ultraviolet radiation, application of biocides, and presented typical examples. We analyzed several emerging techniques, such as synergistic effect of physical and chemical methods, plant extracts and nanomaterials biocides, and reviewed their advantages, disadvantages as well as applicability. Aiming to provide a reference for the research of biodeterioration prevention and conservation of stone buildings, we discussed the preventive methods for biodeterioration of stone building and the assessment methods to test the effects of such methods, and prospected the future research direction.