Table of Content

15 January 2020, Volume 31 Issue 1

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Difference in intra- and inter-specific competition of two endangered plant species (Toona ciliate var. pubescens and Taxus chinensis var. mairei)in the middle subtropical zone of China

XU Jia-wen, SHI Fu-xi, ZHANG Chao-hui, WAN Song-ze, WU Pan-pan, LIU Shan-shan, MAO Rong

2020, 31(1):  1-8.  doi:10.13287/j.1001-9332.202001.006

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Endangered plant species are an important part of global biodiversity. To understand the competition patterns and mechanisms of endangered tree species from plant growth forms in the middle subtropical forest ecosystems, we examined the differences in intra- and inter-specific competitions between Toona ciliate var. pubescens (an intolerant of shade, deciduous species) and Taxus chinensis var. mairei (a tolerant of shade, evergreen species) in the Jiulingshan National Nature Reserve, Jiangxi Province. The results showed that intra-specific competition was dominant in the T. ciliate var. pubescens population, accounting for 66.4% of the total competition intensity. In contrary, the competitive intensity of T. chinensis var. mairei was dominated by the inter-specific competition, which accounted for 68.7% of the total competition intensity. The intra- and inter-specific competition intensity of both species decreased gradually with increasing tree diameter, indicating that competitive pressure was prevalent in small trees. T. ciliate var. pubescens was mainly affected by self-thinning due to intra-specific competition, whereas T. chinensis var. mairei was dominated by alien-thinning due to inter-specific competition. The small individuals of both species could develop into mature stage only after experiencing intense competitive selection during stand regeneration. Considering the substantial difference in the sources of competition pressures, different biodiversity conservation measures should be taken for the two endangered species with contrasting growth forms in the middle subtropical regions.

Effects of increased precipitation on growth of two ephemeral plants in the Gurbantunggut Desert, China

ZHANG Lan, ZHANG Ling-wei, LIU Hui-liang, CHEN Yan-feng

2020, 31(1):  9-16.  doi:10.13287/j.1001-9332.202001.004

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Ephemeral plants are a major component of biodiversity in the deserts of Northwest China, with important ecological functions. Information on plant morphological characteristics and biomass accumulation and allocation during different growth stages could enhance our understanding of the functional features and survival strategy of ephemeral plants. We examined the effects of increased precipitation on ephemeral species Eremopyrum distans and Nepeta micrantha in the Gurbantunggut Desert. Changes in morphological characteristics and biomass accumulation and allocation were analyzed under increasing precipitation 30% and 50% treatments. The results showed that increased precipitation 30% and 50% treatments promoted the growth of E. distans, with leaf area and reproductive organ biomass being increased by 14.2%-188.5% and 55.9%, respectively. The effects of increased precipitation on the growth of N. micrantha varied across different growth stages. At leaf expansion stage, increased precipitation promoted growth of N. micrantha, while at fruit ripening stage, increased precipitation 50% treatment reduced leaf area, plant height, and reproduction biomass by 54.9%, 20.5%, 43.2%, respectively. Thus, the responses of the two species to increased precipitation was species-specific. Increased precipitation would change the survival strategies of the two species, with consequence on the species composition and structure of desert community.

Soil stoichiometry of Pinus massoniana forest in red soil erosion area under different management patterns

WANG Yu-ting, ZHA Xuan, CHEN Shi-fa, BAI Yong-hui, MAO Lan-hua, CHANG Song-tao

2020, 31(1):  17-24.  doi:10.13287/j.1001-9332.202001.007

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We investigated the concentrations of carbon (C), nitrogen (N), and phosphorus (P) and C:N:P stoichiometry in soil and litter of Pinus massoniana forest under four different management patterns: inefficient forest transformation, mixture of arbor with shrub and herb, shallow ditch grass planting, and being banned in serious erosion and degradation of red soil in southern China. Our findings could provide scientific basis for soil erosion control and vegetation restoration in this area. The results showed that there were significant differences in soil organic carbon (SOC), TN, TP and litter nutrient content among different management patterns. The nutrient contents in soil and litter under all the four management patterns were significantly higher than that of control, with mixture of arbor with shrub and herb having the highest concentrations. The concentrations of SOC, TN and TP decreased with the increases of soil layer. However, the shallow ditch grass planting mana-gement pattern presented as follows: the concentrations of SOC, TN and TP decreased first and then increased with the increases of soil layer, with the lowest value in 5-20 cm soil layer. There were significant differences in soil C:N, C:P, N:P and litter C:P among different management patterns, and the soil spatial variation was C:N>C:P>N:P. Excepted for mixture of arbor with shrub and herb, C:N was still at a lower level in the other management patterns, and soil C:P and N:P showed higher values overall. Litter C:N, C:P and N:P had opposite change pattern, with inefficient forest transformation and mixture of arbor with shrub and herb being much smaller than the control. Soil C:N and C:P were mainly controlled by SOC content and litter C content, and soil N:P was mainly controlled by soil TP content and litter P content. Soil stoichiometry was affected by soil water content, soil bulk density, pH, and other factors. The relationship between litter and soil nutrients was closely related and showed similar changes.

Effects of management measures on organic carbon, nitrogen and chemical structure of different soil fractions in Phyllostachys edulis plantations.

YANG Chuan-bao, NI Hui-jing, SU Wen-hui, ZHONG Zhe-ke, ZHANG Xiao-ping, BIAN Fang-yuan, LI Wen

2020, 31(1):  25-34.  doi:10.13287/j.1001-9332.202001.002

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To examine the effects of management measures on carbon and nitrogen contents, as well as their distribution and structural characteristics of different soil fractions in Moso bamboo plantations, we compared three types of the bamboo forests (undisturbed, extensively managed, and intensively managed) and the control secondary broadleaved evergreen forest using the methods of physical fractionation, chemical and biological analysis and Fourier-transform infrared spectroscopy (FTIR). The results showed that soil total organic carbon (TOC) and total nitrogen (TN) content, as well as free particulate organic carbon and nitrogen, soluble organic carbon and nitrogen (DOC, DON), and mineral-associated organic carbon and nitrogen in the undisturbed and extensively managed Moso bamboo plantations were significantly increased compared with that in the control. The distribution ratio of free particulate organic carbon and nitrogen in the undisturbed Moso bamboo plantation significantly increased, with mineral-associated organic carbon being the largest reservoir of soil organic carbon (67.6%). Intensive management resulted in the decrease of soil organic carbon, total nitrogen storage, and the contents of each component, but significantly increased DOC/TOC, the ratio of microbial biomass nitrogen to TN as well as the ratio of microbial biomass carbon to TOC (microbial quotient). Management measures significantly affected the chemical structure of SOC. Compared with the control, the relative intensities of phenolic and alcoholic-OH, aliphatic methyl and methylene, aromatic C=C, and carbonyl C=O absorption were higher in the SOC of undisturbed and extensively managed Moso bamboo plantations, and soil hydrophobicity was significantly increased. Results from correlation analysis showed that soil hydrophobicity and the content of aliphatic and aromatic groups were negatively correlated with microbial quotient and positively correlated with TOC and TN content. In conclusion, the increased inputs of organic matter residues (such as litter and roots) could contribute to the relative accumulation of chemical resistance compounds with reduced human disturbance, which significantly enhanced chemical stability of soil organic carbon. Soil clay minerals played a key role in protecting soil organic carbon through the formation of mineral-organic compounds, which facilitate the stability of soil carbon storage and the long-term preservation of soil carbon.

Validation of vegetation coverage and NDVI based on UAV remote sensing method and its response to hydrothermal gradient

TANG Liang, HE Ming-zhu, XU Hua, JIA Pu-chao

2020, 31(1):  35-44.  doi:10.13287/j.1001-9332.202001.014

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To verify the accuracy of MODIS-NDVI data products in deserts and provide guidance for scientific management of desert grasslands in the context of climate change, we examined the responses of fractional vegetation cover (FVC) and normalized difference vegetation index (NDVI) to hydrothermal gradient in arid desert areas using unmanned aerial vehicle (UAV) remote sensing. In Alxa desert region of Inner Mongolia, GreenSeeker handheld spectrometer was used to obtain NDVI (NDVI_R) of 100 sampling points. NDVI was extracted by MODIS-NDVI data products (NDVI_M), and the accuracy of NDVI_M was verified by NDVI_R. FVC of each sampling point was obtained through unmanned aerial vehicle remote sensing (FVC_U), which was used to examine the FVC that was retrieved by the pixel binary model (FVC_M). In addition, combining meteorological data, we examined the responses of FVC and NDVI to hydrothermal gradient based on UAV remote sensing method. The results showed that MODIS-NDVI data products reflected the real NDVI in Alxa area with an accuracy of 84.2%, but NDVI_M were 15.7% higher than the actual values. FVC_M reflected the vegetation coverage of Alxa region with an accuracy of 83.1%, which were 14.8% lower than the real value. Effects of meteorological factors on NDVI was different, depending on the different acquisition methods. NDVI was affected not only by temperature and precipitation, but also by ground temperature, evaporation and the interaction between evaporation and ground temperature. Because of the different degree of atmospheric influence, NDVI_M was more affected by ground temperature, evaporation and precipitation than NDVI_R, while NDVI_R was more affected by temperature than NDVI_M. To examine the changes of vegetation coverage across hydrothermal gradient in desert area, we should consider not only precipitation and temperature, but also the interaction between evaporation, ground temperature and meteorological factors. The interaction between temperature and rainfall, evaporation and ground temperature, and between temperature and evaporation had greater impacts on FVC_U.

Color quantification and evaluation of landscape aesthetic quality for autumn landscape forest based on visual characteristics in subalpine region of western Sichuan, China

ZHANG Xiao-jing, CHEN Juan, LI Qiao-yu, LIU Jin-chun, TAO Jian-ping

2020, 31(1):  45-54.  doi:10.13287/j.1001-9332.202001.016

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Evaluation of landscape aesthetic quality is a key step in the management system of forest resource. Color is an important component of autumn landscape forest, and quantitative analysis of color and scientific evaluation of landscape aesthetic quality are important for the management of autumn landscape forest. We assessed the aesthetic quality of autumn landscape forest using scenic beauty estimation and analyzed the effects of color characteristics on ornamental value of autumn landscape forest based on color composition and color spatial pattern according to human’s visual characteristics. The results showed that the overall landscape quality of subalpine region of western Sichuan could be divided into five grades according to beauty value (I to V). About 71.5% of autumn landscape forests could be classified into grade I, II, and III, indicating that autumn landscape forests of subalpine region in western Sichuan had higher ornamental value. According to the scenic beauty estimation value, the landscape aesthetic quality of broadleaved mixed forests was higher than that of coniferous and broadleaved mixed forests and pure forests. In terms of the comprehensive index evaluation system of color elements, the index weight coefficient order was landscape patch heterogeneity factors>autumn main color factors>color saturation and brightness factors>color diversity and evenness factors. With cluster analysis, autumn landscape forests of western Sichuan could be divided into three types. The forests with higher ornamental value showed following characteristics: larger degree of patch fragmentation and heterogeneity, higher percentage of orange and yellow and lower percentage of green in autumn, higher percentage of color saturation and brightness, and higher color diversity and uniformity index. The communities with higher richness, species diversity and evenness index would have higher beauty values. We concluded that species diversity and fragmentation of colors should be considered in the construction of autumn landscape forests, and that aesthetic quality of autumn landscape forest could be improved by planting and cultivating tree species with various and bright autumn leaf colors.

Spatio-temporal characteristics of forest fires in China between 2001 and 2017

QIAO Ze-yu, FANG Lei, ZHANG Yue-nan, YANG Jian, JIANG Tao, YUAN Hao

2020, 31(1):  55-64.  doi:10.13287/j.1001-9332.202001.015

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The remotely sensed burned area (BA) products can provide continuous and spatiotemporally explicit characteristics of fire patches, which are critical data sources for understanding regional fire regimes. However, their accuracy remains to be improved. In this study, a global BA product (i.e., CCI_Fire) at 250 m resolution was integrated with global forest change (GFC) product at 30 m to generate a refined BA product, named CCI_GFC product, whose accuracy was evaluated through comparing the BA with pre-existing fire patches data. To reveal the characteristics of forest fire in China between 2001 and 2017, we conducted a grid analysis at 0.05°×0.05° spatial resolution based on the refined BA product and the spatial pattern of eco-regions at the macro scale. The results showed that the accuracy metrics including the recognition rate (RR), variance explained (R²), root mean squared error (RMSE), mean absolute percentage error (MAPE) of the CCI_GFC product (i.e., 83%, 0.91, 0.28, and 8.5% respectively) were all superior to the CCI_Fire product (i.e., 74%, 0.86, 0.36, and 11.8% respectively) and the MCD64A1 product (i.e., 35%, 0.78, 0.48, and 17.3% respectively). The total burned area of forest was approximately 12.11 million hm² for the whole country from 2001 to 2017, while the annual burned area temporally decreased. Forest fires in China were dominated by the low-frequency [0<burned forests rate (BFR)≤40%] burns which occupied 79% of the total burned area. The medium-frequency (40%<BFR≤80%) and high-frequency (80%<BFR≤120%) burns accounted for 11% and 10% of the total burned area, respectively. The seasonality of forest fires differed substantially among eco-regions. The primary fire season of the temperate eco-region was spring (May) and autumn (October). Fire season in the tropical-subtropical eco-region started from the winter to the next spring which included the months from November to next March.

Fire resistance of bark of 11 tree species

WANG Ming-xia, SHAN Yan-long, YIN Sai-nan, JI Xin, WANG Ya-jun, YUAN Bo-han

2020, 31(1):  65-71.  doi:10.13287/j.1001-9332.202001.020

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China is one of the countries with serious forest fires. Besides the methods of strengthening management of fire source and increasing forest fire monitoring and rescue efforts, improving the ability of forest itself to resist fire is also the key to prevent forest fires. In this study, we examined the characteristics of the bark across 11 main tree species in Korean pine broad-leaved forest at Jiaohe Forestry Experimental Area in Jilin Province. Fire resistance of bark acorss the tree species was evaluated comprehensively with four indices of water content, ash content, calorific value and oxygen index, using the methods of entropy weight, variance analysis and cluster analysis. Results showed that water content of bark was the highest in Phellodendron amurense. Calorific value of bark was the lowest and ash content was the highest in Ulmus davidiana. Oxygen index of bark was the highest in Fraxinus mandshurica. Bark fire resistance of 11 tree species followed the order of U. davidiana > Acer mono > Acer triflorum > Acer mandshuricum > F. mandshurica > Quercus mongolica > P. amurense > Tilia amurensis > Juglans mandshurica > Pinus koraiensis > Betula costata. The tree species in Korean pine broad-leaved forest could be classified to five categories according to bark fire resistance: U. davidiana belonged to the category of strongest fire-resistance; A. mono and A. triflorum belonged to the category of strong fire-resistance; A. mandshuricum, F. mandshurica, Q. mongolica, P. amurense, T. amurensis belonged to the category of common fire-resistance; J. mandshurica and P. koraiensis belonged to the category of weak fire-resistance; and B. costata belonged to the category of poor fire-resistance.

Diurnal variation and light response of net ecosystem carbon exchange in a temperate broadleaved deciduous forest at Maoershan, Northeast China

ZHU Yuan, LIU Fan, WANG Chuan-kuan, WANG Xing-chang

2020, 31(1):  72-82.  doi:10.13287/j.1001-9332.202001.040

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Photosynthetically active radiation (PAR) is a key environmental factor affecting the change of net ecosystem exchange (NEE) during the daytime. However, the coordinate system of PAR measured by horizontal radiometers over sloping terrain does not match that of NEE after tilt-corrected of the ultrasonic anemometer. Using the temperate deciduous broad-leaved forest at the Maoershan site with an average slope of 9° and a azimuth of 296° as a case, we investigated the diurnal variations in NEE and its driving factors in the growing season (May to September) of 2016. We assessed the differences in estimating light response parameters and the explanations of NEE by other environmental factors between the PAR measured by horizontal and slope-parallel radiometers. The results showed that the diurnal change of NEE in each month of the growing season presented a morning-afternoon asymmetrically unimodal curve: the value was negative (net carbon absorption) about 2.5 h after sunrise, reached the peak around 12:00, then approached zero again at two hours before sunset. The daily net uptake maximized in July and minimized in May. During the whole growing season, the time-lag and difference in the PAR measured by the horizontal versus slope-parallel radiometers led to that the PAR values measured by the horizontal radiometer increased photosynthetic quantum yield (α) and daytime respiration rate (R_d) by 13.3% and 11.5%, respectively, and decreased the maximum photosynthetic efficiency (A_max) by 7.7%. The light response curves of NEE were asymmetrical in the morning and afternoon, with R_d and A_max in the afternoon being greater than that in the morning. Weather conditions affected light response parameters: on cloudy days, A_max was higher than that in sunny days, the α and R_d were lower versus those in sunny days for most conditions. However, the monthly A_max and R_d were generally higher for horizontally measured PAR than for slope-parallelly measured PAR, especially for A_max in the cloudy afternoon. The radiometer-orientation affected the explanation of daytime NEE by air temperature (T_a) and vapor pressure deficit (VPD). The correlation of NEE residual based on the slope-parallel radiometer with T_a and VPD (r ranged: 0.013 to 0.197, 0.098 to 0.224) was tighter than that based on the horizontal radiometer (r ranged: 0.082 to 0.219, 0.162 to 0.282) when the negative correlations with T_a for September was excluded. Our results indicated that the measurements of PAR on the inclined terrains could cause errors in the environmental interpretations of NEE. Such findings had implications for the radiometric measurement of mountain vegetation and the reasonable interpretation of carbon exchange in terrestrial ecosystems.

Vegetative reproduction characteristics of Leymus chinensis in heterogeneous habitats in Songnen Plain, China

CHU Li-shuang, LI Hai-yan, YANG Yun-fei

2020, 31(1):  83-88.  doi:10.13287/j.1001-9332.202001.001

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The perennial clonal grasses rely mainly on vegetative reproduction to achieve continuous regeneration. Buds and juvenile tillers formed by buds are potential populations for vegetative reproduction. We compared the composition and size of potential population of Leymus chinensis in the enclosure meadow, long-term mowing meadow, enclosing sand-covered meadow, and forest-grassland, with excavation sampling by unit area and using vegetative reproduction generations to classify the age of tillers, rhizomes and various types of buds and juvenile tillers. The results showed that at the end of the growing season, potential population of L. chinensis was composed of rhizome buds and buds of tiller growing upwards at different ages, as well as juvenile tillers on the tillers and rhizomes. Across the four habitats, the potential population of tillers of L. chinensis was composed of 3-4 age classes, and the rhizomes’ potential population consisted of four age classes, of which the potential population formed by rhizomes accounted for 68.3% of the total potential population. The potential population produced by 1st age class tillers and rhizomes accounted for 60.2% of the total, which was the main part of the potential population composition and the main source of population renewal. The potential population of tillers was the most abundant in long-term mowing meadow. The potential population of rhizomes was the most abundant in enclosing sand-covered meadow. The vegetative fertility of tillers and rhizomes was the highest in young age. The vegetative fertility of rhizomes was 10.0 times as that of tillers, which dominated the vegetative reproduction of L. chinensis. The potential population composition of L. chinensis varied greatly across different habitats, reflecting the divergent adaptation to habitat variation.

Responses of potential suitable area of Paris verticillata to climate change and its dominant climate factors

JI Liu-ting, ZHENG Tian-yi, CHEN Qian, ZHONG Jiao-jiao, KANG Bing

2020, 31(1):  89-96.  doi:10.13287/j.1001-9332.202001.012

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Prediction of the potential distribution of species based on the data of its current distribution in combination with climatic variables is important for understanding species evolution and reasonable conservation. Based on 220 distribution sites in China and 12 low-correlation climatic variables, we analyzed the potential distribution of Paris verticillata at present and future (2050s and 2070s) using the MaxEnt model and ArcGIS program. Further, we analyzed the dominant driving factors for its geographic distribution. The results showed that the area under the curve indices (AUC) was 0.940, with high prediction accuracy. The potential suitable regions of P. verticillata were mainly distributed in the Greater Xing’an Mountains, the Xiao Xing’an Mountains, the Changbai Mountains, the Qinling-Daba Mountains, Hebei, Shanxi and north Shandong under current climate scenario. Those regions accounted for 18.1% of the total suitable area in the country, of which the highly suitable areas accounted for 7.0% and the lowly suitable area 11.1%. The total suitable areas of P. verticillata in the 2050s and 2070s would decline under the climate change scenarios of RCP 2.6, RCP 4.5, RCP 6.0 and RCP 8.5. The highly suitable area would decline, but the lowly suitable area would increase. With the global climate change, both the range and the geometric center of its distribution would gradually spread to higher altitude in the northeast. The cumulative contributions of four dominant factors reached as high as 89.2%, namely, precipitation of wettest month, mean annual temperature, isothermality, and precipitation of January. Their appropriate ranges were 100-275 mm, -0.1-16 ℃, 21-35 and 3-14 mm, respectively.

Climatic suitability for the distribution of Vitis heyneana and V. davidii in China

WANG Jing, ZHOU Guang-sheng

2020, 31(1):  97-103.  doi:10.13287/j.1001-9332.202001.019

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Vitis heyneana and V. davidii are two wild wine grape varieties that originate from China. In this study, we used the principle of maximum entropy in terms of sufficiency and necessity to identify the dominant climatic factors (among the many climatic factors that were brought up by previous relevant studies) affecting the planting distribution of both varieties in China. Based on the probability of planting distribution determined by the comprehensive effect of these dominant climatic factors, we further analyzed the climatic suitability in China for both wild varieties. The results showed that the four dominant climatic factors affecting the spatial distribution of both varieties were annual sunshine duration, precipitation during the flowering stage in May, annual extreme minimum temperature, and average temperature during the coldest month of January. The optimal wine grape-growing subregions for both varieties were mainly located in the western and southern parts of Hunan, the north-central part of Guangxi, the southeastern part of Guizhou, and the central part of Chongqing. The areas of optimal, suitable, and sub-suitable subregions for planting V. heyneana and V. davidii accounted for 2%, 14%, and 16% of the total area of the research region, respectively. In the optimal/suitable subregions for planting both varieties, annual sunshine duration was between 1200-1800 h, annual extreme minimum temperature was above -8 ℃, average temperature during the coldest month of January was between 2-13 ℃, and monthly precipitation in May was between 110-320 mm.

Variations of soil respiration and its temperature sensitivity in the reversion process of desertification in the eastern Hobq Desert, China

WANG Bo, DUAN Yu-xi, WANG Wei-feng, LIU Zong-qi, LI Xiao-jing, LIU Yuan

2020, 31(1):  104-112.  doi:10.13287/j.1001-9332.202001.005

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To clarify the effects of desertification reversal on soil respiration rate (R_s) and its temperature sensitivity (Q₁₀), five different reversal stages were selected: mobile dune, semi-fixed sandland, algae crust fixed sandland, lichen crust fixed sandland, and moss crust fixed sandland in the eastern Hobq Desert. R_s at different stages were measured by static chamber-gas chromatography and the Q₁₀ was calculated. We analyzed the effects of environmental factors on R_s. The results showed that R_s gradually increased with sand fixation and vegetation succession: moss crust fixed sandland (0.78 μmol·m^-2·s^-1)> lichen crust fixed sandland (0.67 μmol·m^-2·s^-1)> algae crust fixed sandland (0.46 μmol·m^-2·s^-1)> semi-fixed sandland (0.42 μmol·m^-2·s^-1)> mobile dune (0.29 μmol·m^-2·s^-1). The R_s of growing season was higher than that of non-growing season. Q₁₀ of R_s at different reversal stages followed the order: mobile dune (3.28)> semi-fixed sandland (2.93)> algae crust fixed sandland (2.54)> lichen crust fixed sandland (1.91)> moss crust fixed sandland (1.84). The Q₁₀ of non-growing season was higher than that of growing season. There was positive correlation between R_s and soil temperature. R_s of mobile and semi-fixed sand was positively correlated with soil water content, but not in other three fixed sandlands. R_s was correlated with soil total nitrogen, organic carbon, bulk density, porosity, quantity of bacteria, quantity of actinomycetes and quantity of fungi. Our results indicated that in the process of desertification reversal, the increases of soil organic carbon and nitrogen content and the abundance of microbes, the improvement of soil texture and the accumulation of plant biomass could dramatically enhance soil respiration and reduce its temperature sensitivity, which were the main driving forces to change carbon cycle of desert soil, and mediate the effects of soil water on soil respiration.

Effects of water supply on biomass yield, root/shoot ratio and water use efficiency of forage crops in intercropping systems

LIU Ya-nan, LAI Xing-fa, YANG Qian, WANG Zi-kui

2020, 31(1):  113-121.  doi:10.13287/j.1001-9332.202001.008

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Rainfall is limited and unevenly distributed across different seasons in the sub-humid but drought-prone area on Loess Plateau, China. Understanding the effects of water supply on the growth of forage crops is of great significance for guiding forage cultivation. Pot experiment was carried out in a shelter in this study. There were five cropping patterns, including monoculture of common vetch, oat and maize, oat/common vetch intercropping, and oat/maize intercropping. There were three water supply levels, including high (low limit of 70% field capacity), medium (low limit of 55% of field capacity) and low (low limit of 40% of field capacity) water. The results showed that land equivalent ratio in the oat/common vetch intercropping group were 1.20, 1.21 and 1.19 at the high, medium and low water supply levels, respectively, and those in the oat/maize intercropping were 1.17, 1.11 and 1.03. Such results indicate that all of the intercropping systems had yield advantages compared with all monoculture. Among the five planting patterns under the same water supply level, the total dry matter yield of maize monoculture was the highest, and that of common vetch monoculture was the lowest. Yields of dry matter and crude protein of oat increased with the decreases of water supply, while common vetch and corn monoculture showed opposite trends. On per plant basis, intercropping increased dry matter yield and crude protein yield of oat, while decreased the yield of common vetch and maize, oat showed an intercropping advantage. Compared with the high water treatment, dry matter yield of the oat/common vetch intercropping increased insignificantly by 4.1% and 4.8% respectively compared with that in the treatments of medium water and low water, whereas dry matter yield of the oat/maize intercropping was significantly reduced by 8.0% and 13.0% respectively. Compared with high water treatment, root/shoot ratio of the oat/common vetch intercropping was significantly increased by 33.4% and 58.4% under the treatments of medium and low water respectively. However, medium and low water supply significantly reduced root/shoot ratio in the oat/maize intercropping. Compared with high water treatment, water use efficiency of the oat/common vetch intercropping significantly increased by 11.7% and 12.9% under the treatments of medium and low water respectively, while water use efficiency of oat/maize intercropping was not affected by water application. In summary, yield of forage maize monoculture and oat/forage maize intercropping were higher, but they were sensitive to water shortage and had low yield stability. Under insufficient water conditions, yield stability, crude protein production and water use efficiency in oat/common vetch intercropping system were greater. Consequently, we suggest this system should be used in the study area.

Impacts of herbicide-resistant soybean ZUTS-33 with g10-epsps gene on field biodiversity

LIU Lai-pan, SHEN Wen-jing, XUE Kun, LIU Biao

2020, 31(1):  122-128.  doi:10.13287/j.1001-9332.202001.010

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Evaluating the impacts of genetically modified crops on biodiversity is a necessary step before their release to the field and obtaining environmental safety certificates. To assess the ecological safety of herbicide-resistant soybean ZUTS-33, we compared arthropod diversity, diseases occurrence, nodule number, and weed diversity through spraying herbicide or water on ZUTS-33, and its parental control receptor HC-3 and main cultivar soybean ZH-13 in a field experiment. The results showed that there was no significant difference of arthropod diversity (number of insects per 100 plants, Shannon index, Simpson index and Pielou index), diseases incidence rates and disease index, nodules and weed diversity between ZUTS-33 and non-genetically modified control soybean HC-3 and ZH-13. Spraying herbicide on ZUTS-33 had no significant effect on arthropod diversity, diseases and rhizobium compared with those treatments of spraying clear water on ZUTS-33, non-genetically modified control HC-3 and ZH-13, and the abundance of weeds were significantly decreased.

Effects of slow-release urea combined with common urea application layered in different soil depths on soil nitrogen, enzyme activity, and maize yield

WU Peng, WANG Yu-feng, ZHANG Yi-fei, CHEN Tian-yu, YANG Li, XUE Ying-wen, YANG Ke-jun

2020, 31(1):  129-138.  doi:10.13287/j.1001-9332.202001.021

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We examined the effects of a combination of slow-release urea (PCU) and common urea (PU) applied at different soil depths (0-30 cm soil layer) on inorganic nitrogen content, enzyme activity, and crop yield during two years (2017-2018) in a field experiment. There were eight treatments: CK (without N fertilizer); PU₁(common urea applied at 5-10 cm deep soil layer); PU₂(common urea applied at 5-10 cm deep soil layer, 60% seed fertilizer + 40% topdressing); PU₃(20% common urea at 5-10 cm soil depth, 30% common urea at 15-20 cm soil depth, 50% common urea at 25-30 cm soil depth); PCU₁(20% total nitrogen application rate at 5-10 cm soil depth, 30% total nitrogen application rate at 15-20 cm soil depth, 50% total nitrogen application rate at 25-30 cm soil depth), the N fertilizer at 5-10 cm was common urea, but, at 15-20 and 25-30 cm, it was a combination of PCU and PU at ratios of 3:7 and 3:7; PCU₂ was as PCU₁ but the ratio of PCU and PU was 5:5 at 15-20 cm and 5:5 at 25-30 cm; in PCU₃, the ratio of PCU and PU was 3:7 at 15-20 cm and 5:5 at 25-30 cm; in PCU₄, the ratio of PCU and PU was 5:5 at 15-20 cm and 3:7 at 25-30 cm. The results showed that PU₁ could meet nitrogen demand at the 0-10 cm layer in the early growth stage compared with CK. PU₂ and PU₃ could meet nitrogen demand for 10-30 cm soil layer in the early stage of maize development. The combined application of slow release urea and common urea could meet nitrogen demand for the whole growth period of maize. In the filling and maturing period, combined application of slow release and common urea significantly increased not only NO₃^--N, NH₄⁺-N, and alkali-hydrolyzed nitrogen contents but also urease and protease activities in the 10-20 cm and 20-30 cm soil layers compared with PU₁-PU₃. Compared with PU₃, maize yield increased by 2.3%-24.6% and 1.3%-16.5% in the PCU₁-PCU₄ treatments in 2017 and 2018, respectively. PCU₄ had the highest yield, with 13899 and 12439 kg·hm^-2, respectively. Therefore, the combined application of slow-release and common urea at different soil layers could meet nitrogen demand in the early growth stage of maize and increase the content of inorganic nitrogen and enzyme activities in the 10-30 cm soil layers in the later growth period, which promoted the growth and increased the yield of maize. Among all the treatments PCU₄ treatment was the most effective.

Effects of water-fertilizer coupling on the yield of spring maize under shallow-buried drip irrigation in semi-arid region of western Liaoning Province

WANG Shi-jie, YIN Guang-hua, LI Zhong, GU Jian, MA Ning-ning, FENG Hao-yuan, LIU Yong-qi

2020, 31(1):  139-147.  doi:10.13287/j.1001-9332.202001.025

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To reveal the coupling effect of water and fertilizer on the yield of spring maize under shallow-buried drip irrigation in semi-arid area of western Liaoning, a field experiment was conducted with the quadratic regression orthogonal design of three factors (water, nitrogen and potassium) crossed with five levels in 2017-2018. A quadratic regression model was established with yield (Y) as the dependent variable and irrigation amount (W), nitrogen (N) and potassium (K) application amounts as independent variables to analyze the coupling relationships between Y and W, N and K, respectively. The results showed that the shallow-drip irrigation water-fertilizer coupling had significant impact on yield. The single factor of W, N and K promoted the yield, with their effects ranking as W>N>K. The effect of two-factor interaction on yield increased first and then decreased which ranked as WN>WK>NK. Considering the three-factor coupling effect on yield, the combination of abundant water, nitrogen and potassium was the highest, followed by high water, nitrogen and potassium, and low water, nitrogen and potassium the lowest. As the optimal treatments found by the model, we obtained the suitable water-fertilizer application range of shallow-buried drip irrigation with higher target yield of 8000-8810 kg·hm^-2, that was, the irrigation amount was 43-61 mm, nitrogen 138-343 kg·hm^-2 and potassium 79-163 kg·hm^-2 under the ambient natural rainfall. The results provided a referable basis for application of water-fertilizer integrated cropping pattern under shallow-buried drip irrigation in semi-arid area of northern China.

Impacts of combined N and Zn application on Zn translocation, partitioning, and accumulation in Triticum aestivum

YANG Xi-wen, SONG Miao, LI Qiu-jie, ZHOU Su-mei, HAN Shao-yu, CHEN Xu, XU Li-li, HE De-xian

2020, 31(1):  148-156.  doi:10.13287/j.1001-9332.202001.027

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Field experiment was conducted to examine the effects of combined application of N and Zn fertilizers on translocation, distribution, and accumulation of Zn in different organs in wheat plants. The results showed that Zn concentration and Zn accumulation in each organ were significantly different under different treatments. Compared with N₃ (120 kg·hm^-2), the grain Zn concentration of N₁ (240 kg·hm^-2) and N₂ (180 kg·hm^-2) increased 22.0% and 8.9%, respectively. Compared with the non-Zn application treatment (CK), grain Zn concentration under ZnS (soil Zn fertilization), ZnF (foliar Zn fertilization), and ZnS+ZnF (soil Zn fertilization combined with foliar Zn fertilization) treatments were increased by 5.4%, 60.5% and 72.8%, while Zn accumulation in grain were increased by 21.3% 82.5% and 102.4%, respectively. Zn in grain mainly came from the remobilization of Zn uptaken after antheis, with the accumulative contribution being 89.9% and 100.0% in ZnF and ZnS+ZnF, respectively. Compared with ZnS, Zn fertilizer recovery and use efficiency of ZnF and ZnS+ZnF were increased by 4.8, 1.1 times and 7.9, 2.2 times, respectively. Under current condition, Zn concentration and Zn accumulation in different organs of wheat increased with increasing N rate when it was less than 240 kg·hm^-2, which was significantly increased in the grain by foliar Zn application. Therefore, Zn concentration and Zn accumulation in wheat grain could be increased by maintaining the high-yield N fertilization and combining the foliar Zn application in the late growth stage, which would improve Zn nutritional quality of wheat grain.

Effects of long-term fertilization on soil organic phosphorus fractions and wheat yield in farmland of Loess Plateau

LIU Jin, LI Chun-yue, XING Ya-wei, WANG Yi, XUE Ying-long, WANG Cong-rong, DANG Ting-hui

2020, 31(1):  157-164.  doi:10.13287/j.1001-9332.202001.028

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Understanding the effects of long-term fertilization on soil organic phosphorus fractions and wheat yield in the Loess Plateau can provide theoretical support for improving phosphorus conversion, utilization, and rational use of fertilizer. We examined the effects of different fertilizer treatments on soil organic phosphorus fractions, wheat yield and soil properties of a farmland in the long-term (1984-2016) positioning test station of Changwu loess soil. There were eight treatments, including no fertilizer (CK), single application of nitrogen fertilizer (N), single application of phosphorus fertilizer (P), application of nitrogen and phosphorus fertilizer (NP), single application of organic fertilizer (M), nitrogen combined with organic fertilizer (MN), phosphorus combined with organic fertilizer (MP), nitrogen and phosphorus combined with organic fertilizer (MNP). The results showed that the range of soil organic phosphorus content was 244.7-429.1 mg·kg^-1 after long-term fertilization. Except for the N treatment, organic phosphorus content was significantly increased by 15.4%-47.9% compared to CK. Long-term application of phosphorus fertilizer changed the content of organic phosphorus fractions in the surface soil (0-20 cm). The treatments of MP and MNP significantly increased the contents of labile organic phosphorus and moderately labile organic phosphorus. The treatments of N, P and NP significantly reduced the content of moderately stable organic phosphorus. The treatments of N, P, NP, MN, MP, MNP all significantly increased the highly stable organic phosphorus. The ratio of soil organic phosphorus fractions to total organic phosphorus content was in order of moderately labile organic phosphorus > highly stable organic phosphorus > labile organic phosphorus > moderately stable organic phosphorus. After long-term fertilizer application, the combination of nitrogen and phosphorus fertilizers, especially with organic fertilizers, significantly increased wheat biomass yield and grain yield. Among all the examined soil properties, organic matter, Olsen-P and total inorganic phosphorus were significantly positively correlated with wheat yield. MP and M could significantly increase the content of Olsen-P, total phosphorus, total inorganic phosphorus, labile organic phosphorus and moderately labile organic phosphorus in the loess soil of Loess Plateau. Our results indicated that the organic and phosphorus fertilizers could improve soil phosphorus components that could be more easily absorbed by crops. In summary, the combination of nitrogen and phosphorus fertilizers, especially with organic fertilizers, could increase soil phosphorus supply in the region and promote the wheat yield, which is important for improving soil quality in the Loess Plateau.

Effects of late sowing of two season crops on annual yield and resource use efficiency in rice-wheat double cropping system

XI Min, DU Xiang-bei, WU Wen-ge, KONG Ling-cong, CHEN Jin-hua, YUE Wei, XU You-zun, ZHOU Yong-jin

2020, 31(1):  165-172.  doi:10.13287/j.1001-9332.202001.023

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The unreasonable resource allocation and lower resource use efficiency for rice-wheat double cropping system in Jianghuai region resulted from climate change severely limit the coordinated development of annually high yield and high efficiency crops. Optimizing seasonal resource allocation through sowing date adjustment is an important way to tap the annual high-yield potential and improve resource use efficiency. To quantify the effects of sowing date of rice and wheat on annual yield and resource allocation and utilization efficiency, field experiments were conducted in 2013-2015. Results showed that compared with the conventional rice-wheat cropping system (T₂), the two seasons appropriate late-cast cropping system (T₃) could coordinate resource allocation in the two seasons through the sowing date adjustment, and transfer the redundant radiation and heat resources in the wheat season to the rice. The distribution rate of accumulated temperature, radiation and rainfall resources for T₃ were: rice season accounted for 60.5%, 46.5% and 56.7%, wheat season accounted for 36.3%, 50.0% and 40.9%, and the ratio between two seasons was 1.67, 0.94 and 1.39, respectively. Rice yield and its proportion of annual production were significantly increased. The wheat yield was significantly decreased, with the variation range being smaller than that of rice. The total annual yield was increased by 336.3 kg·hm^-2 as compared with T₂. The temperature, radiation and rainfall production efficiency for rice in T₃ were increased by 9.8%, 5.6% and 8.3% in compared to T₂, respectively. There was no significant difference in the climate resource utilization efficiency of wheat season. The annual resource production efficiency of T₃ was increased by 4.8%, 3.1% and 6.0% over the T₂, respectively. Earlier (T₁) or latest sowing (T₄) of two seasons cropping system was not appropriate for annual yield formation and resource utilization. In summary, improving resource utilization efficiency in rice season is the key way to increase annual grain yield potential in Jianghuai region. The results provided theoretical and practical bases for the excavation of yield potential of the regional annual cropping system and the adjustment of planting structure.

Effects of reduced chemical fertilizer with organic fertilizer application on soil microbial biomass, enzyme activity and cotton yield

WANG Ning, NAN Hong-yu, FENG Ke-yun

2020, 31(1):  173-181.  doi:10.13287/j.1001-9332.202001.022

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The effects of 20%-40% fertilizer reduction and different organic fertilizers on soil microbial biomass, enzyme activity and cotton yield were examined for three consecutive years in Hexi area of Gansu, Northwest China. The results showed that compared with single chemical fertilizer application, the abundance of soil bacteria and actinomycetes were significantly increased while that of fungi were decreased with chemical fertilizer reduction combined with organic fertilizer. The abundance of soil bacteria was maximum under the treatment of chemical fertilizer reduction combined with common organic fertilizer and bio-organic fertilizer (COBF₂), which was 84.6%, 57.1% and 43.5% higher than that under single application of chemical fertilizer (CF) in the bud stage, boll stage and boll open stage, while the abundance of actinomycetes was maximum under the chemical fertilizer reduction combined with common bio-organic fertilizer (CBF₂), which was 28.2%, 32.7% and 32.2% higher than CF. The abundance of fungi was the lowest in the CBF₂ treatment, which was 35.8%, 29.3%and 13.4% lower than CF treatment in three periods. The ratios of bacteria to fungi, actinomycetes to fungi and the activity of soil urease, catalase, sucrase and alkaline phosphatase were increased by the chemical fertilizer reduction combined with organic fertilizer. COBF₂ was the most effective way to improve enzyme activity. Fertilizer reduction combined with the application of organic fertilizer increased boll number per individual of cotton plant, promoted cotton growth and dry matter accumulation in the ground to a certain extent. The cotton yield under COBF₂ treatment was the highest, which showed an significant increase of 14.2% and 10.9% respectively in seed and lint cotton yield than CF. Our results showed that COBF₂, with 60% reduction of chemical fertilizer combined with 1800 kg·hm^-2 ordinary organic fertilizer and 600 kg·hm^-2 biological organic fertilizer, had the best fertilization effect.

Effects of Na₂WO₄ on ¹⁵N absorption and utilization,¹³C accumulation of apple seedling, and fruit quality

WANG Fen, YUE Yu-jin, LI Min, LUO Jia-kun, GE Shun-feng, JIANG Yuan-mao

2020, 31(1):  182-188.  doi:10.13287/j.1001-9332.202001.024

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Pot culture and field experiments were carried out with one-year-old apple rootstock M9T337 seedlings and five-year-old ‘Yanfu3’/SH6/M. hupehensis Rehd. as test materials respectively. Combined with ¹⁵N and ¹³C isotope tracer technology, we examined the effects of different concentrations of NR inhibitor Na₂WO₄(0, 0.5, 1, 1.5 mmol·L^-1, expressed by CK, T₁, T₂ and T₃ respectively) on ¹⁵N absorption and ¹³C accumulation of seedling and apple quality. The results showed that 0.5-1.0 mmol·L^-1 Na₂WO₄ significantly inhibited shoot growth but not root growth of seedling in the pot experiment. Root growth was significantly inhibited when the concentration of Na₂WO₄ reached 1.5 mmol·L^-1. The NR activity of each treatment was negatively correlated with the concentrations of Na₂WO₄ in the same period, with an order of CK>T₁>T₂>T₃. The content of nitrate in leaves showed the trend of first rising and then decreasing with the extension of processing time. Nitrate content was positively correlated with Na₂WO₄ concentration in the same period, with an order of T₃>T₂>T₁>CK. Spraying Na₂WO₄ reduced the ¹⁵N absorption of each organ and ¹⁵N utilization rate, with such effects increasing with the amount of spraying. With the increases of Na₂WO₄ concentration, ¹³C accumulation on the ground increased first and then decreased, with highest value in T₂ treatment. The ¹³C accumulation of whole plant showed a similar pattern. The results of field experiment showed that Na₂WO₄ application reduced nitrogen contents of leaves and fruits at maturity stage, and increased the anthocyanin content in peel, soluble solids, soluble sugar content and sugar acid ratio in fruits. The T₂ treatment showed the best effect. In summary, T₂ treatment (1.0 mmol·L^-1 Na₂WO₄) could inhibit shoot growth of seedlings, reduce ¹⁵N absorption and utilization, improve ¹³C accumulation, which would improve apple quality.

Effects of exogenous plant hormones on physiological characteristics and yield of sweet potato under drought stress

WANG Jin-qiang, LI Huan, LIU Qing, ZENG Lu-sheng

2020, 31(1):  189-198.  doi:10.13287/j.1001-9332.202001.026

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To explore the alleviation effect of spraying phytohormone on physiological characteristics and yield of sweet potato under drought stress in different periods, and to determine the best period of spraying external plant hormones, the effects on endogenous hormone content, photosynthetic fluorescence characteristics and yield of sweet potato were examined by spraying 6-benzylaminopurine (6-BA), α-naphthylacetic acid (NAA) and abscisic acid (ABA) respectively under drought stress after transplanting for 20 days (early stage), 60 days (middle stage) and 100 days (later stage) under artificial water control. The results showed that compared with spraying water, exogenous phytohormones significantly increased the yield of sweet potato under drought stress, among which 6-BA had the highest effect, followed by NAA and ABA. The effect of spraying in early stage was better than that in middle and late stages. Exogenous phytohormones significantly increased photosynthetic and chlorophyll fluorescence parameters of sweet potato leaves under drought stress at different stages, alleviated the decrease in eatin ribonucleoside (ZR) and auxin (IAA) caused by drought. Stepwise regression analysis showed that endogenous hormones and photosynthetic characteristics were key factors affecting yield of sweet potato. Results of path analysis showed that spraying exogenous plant hormone affected sweet potato yield by changing net photosynthetic rate (P_n), IAA, ZR, maximal photochemical efficiency and photochemical performance index under drought stress at early stage. Therefore, spraying 6-BA could regulate the content of endogenous hormones and improve photosynthetic characteristics of sweet potato at the early growth stage, and thus effectively alleviate the loss of yield caused by drought stress.

Dynamic identification of double-early rice heat and its spatiotemporal characteristics in Jiangxi Province, China

YANG Jian-ying, HUO Zhi-guo, WANG Pei-juan, WU Ding-rong

2020, 31(1):  199-207.  doi:10.13287/j.1001-9332.202001.017

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Constructing evaluation indicator for rice heat damage based on hot weather process (occurring time of hot weather and its duration) can realize the dynamic identification of rice high-temperature heat damage level, which is of great importance to the precisely monitoring, warning and assessment of rice heat. Meteorological, historical disaster and phenological data on double-early rice in Jiangxi Province were integrated to retrieve the historical heat of double-early rice. The dynamic index of high temperature heat injury on early rice based on high temperature weather process was constructed based on K-S distribution fitting test and confidence interval method. The results were verified with reserved independent samples. A rice heat index (M) was calculated, with which rice heat risk was analyzed. The results showed that the starting time and duration of hot weather were key factors affecting the occurrence of rice heat damage, with the effect of starting time greater than the duration. Light, moderate, and severe rice heat for 3-5 d was identified at 10-12, 5-9 and 2-4 d after heading respectively. Similarly, light, moderate and severe rice heat lasting for 6-8 d and >8 d started at 11-18, 8-10, 1-7 d after heading and 12-18, 8-11, 0-7 d after heading respectively. The coincident rate of rice heat damage indicator was 73.7%, and that verified to be identical or one grade different was 89.5%. The linear tendency rate of M from 1981 to 2015 was 0.04·a^-1, with abrupt change from low to high around 1999. A high M (>0.18) was mainly found in the middle and the northeast part of the study area. Increasing trends of a high M occurred in the middle, northeast and south of Jiangxi, with tendency rates > 0.04·a^-1. In general, the indicators constructed in this study realized the dynamic identification of process-based rice heat. The middle and northeast parts of Jiangxi Province were identified as high risk areas for double-early rice heat.

Delimitation of urban development boundary based on ecological sensitivity evaluation and CA-Markov simulation in plain city:A case of Nanchang, Jiangxi, China

YI Dan, ZHAO Xiao-min, GUO Xi, ZHAO Li-hong, ZHANG Han, HAN Yi, Roshan Subedi, LUO Zhi-jun

2020, 31(1):  208-218.  doi:10.13287/j.1001-9332.202001.013

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The rational delimitation of urban development boundary plays an important role in guiding the orderly growth of urban space and ensure proper environment health of urban space. In this study, we evaluated the ecological sensitivity of Nanchang City from four aspects (soil erosion, habitat, geological disaster and water resource) and simulated urban expansion in 2020 based on CA-Markov and land use data in 2000, 2010 and 2015. Spatial decision-making analysis of the two aspects was carried out in combination to the future development of the study area. We proposed a new method of delimitating urban development boundary integrating environmental protection and urban development through the dynamic coordination of both aspects. The results showed that ecological sensitivity of Nanchang City was moderate. The scale of urban construction land based on CA Markov simulation was 1239.67 km², which slightly exceeded the planned construction land target (1201.65 km²). When the dynamic adjustment was done by superimposing the ecological sensitivity evaluation results with the expansion simulation results, the adjusted construction land scale of Nanchang City was 1193.15 km², which met the planned requirement. Consideration of the coordination of protection and development could not only protect the ecological space, but also help to guide the orderly growth of urban space and ensure the healthy development of urban space, and thus was an important way to achieve a win-win situation between rational urban development and ecological protection.

Ecological quality assessment and the impact of urbanization based on RSEI model for Nanjing, Jiangsu Province, China

HANG Xin, LUO Xiao-chun, CAO Yun, LI Ya-chun

2020, 31(1):  219-229.  doi:10.13287/j.1001-9332.202001.030

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Using Landsat 5/TM and Landsat 8/OLI images in 2000 and 2017, based on remote sensing ecological index (RSEI) model, combined with meteorological observation data and socio-economic data in Nanjing from 2000 to 2017, we analyzed and evaluated the ecological environment changes and the characteristic ecological areas in Nanjing. The results showed that the average RSEI of Nanjing decreased from 0.626 to 0.618 during 2000-2017. The RSEI values could be divided into five grades: bad, poor, fair, good and excellent. The proportion of area above good grade decreased from 61.0% to 57.1%, while that below poor grade increased slightly. Compared with 2000, the proportion of areas with improved ecological environment quality was 34.5%, 34.7% area had deteriorated, and 30.8% area remained unchanged in 2017. Among them, the ecological quality of main urban area had significantly improved, and the area with improved ecological quality exceeded that of deterioration. The ecological quality of new urban area and suburbs had deteriorated. The area with poor ecological environment exceeded the area of improvement. Among the three ecological protection areas, the ecological quality of Zijin Mountain was significantly better than that of Laoshan Mountain and Jiangxinzhou. The urbanization rate was negatively correlated with RSEI, with a correlation coefficient of -0.91. The urbanization process would have negative impacts on the ecological environment in general. However, strict protection and management measures could maintain the good ecological environment even improve it.

Temporal and spatial variations of impervious surface landscape pattern and the driving factors in Xiamen City, China

ZHOU Zheng-long, SHA Jin-ming, FAN Yue-xin,SHUAI Chen, GAO Shang

2020, 31(1):  230-238.  doi:10.13287/j.1001-9332.202001.018

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Xiamen is one of China’s five major special economic zones and is the core city of Haixi Economic Zone, with a high level of urbanization. Monitoring and driving force analysis of impervious surfaces can increase our understanding of urbanization process and have important significance for urban landscape pattern research and urban ecological environment construction. We used the Landsat remote sensing image data from 1978 to 2018 to reveal the temporal and spatial variation characteristics of the impervious surface landscape in Xiamen in the past 40 years, using the full-restricted least squares method, landscape pattern analysis, slope gradient analysis and correlation analysis. We further analyzed its relationship with social and economic factors. The results showed that, during 1978-2018, the impervious surface of Xiamen increased by 348.96 km², with a mean annual increase of 8.72 km². The impervious surface dynamics reached a maximum of 9.0% in 2005-2010. More than 86.6% of the impervious surface of Xiamen was distributed within 6° of slope, with a tendency to expand to a greater slope in 2010-2018. With the increases of slope, the proportion of impervious surface decreased, the density of plaque decreased with the shape tending to be regular and continuous, the degree of fragmentation of the impervious surface increased. The increases of impervious surface in Xiamen was significantly related to the regional economic aggregate and population. In the study period, the spatial pattern of impervious surface in Xiamen significantly altered. In the future urban planning process, the extent and speed of impervious surface expansion should be coordinated to avoid ecological problems caused by excessive impervious surface to meet the need for sustainable development of Xiamen.

Comparison on driving mechanism of county ecological efficiency: With three counties in the mountainous area of southern Ningxia, China as an example

ZHOU Jun-jun, FAN Xin-gang, YANG Mei-ling, XIAO Cheng-quan, JIA Hong-li

2020, 31(1):  239-248.  doi:10.13287/j.1001-9332.202001.011

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With Tongxin, Xiji, and Longde counties in the mountainous area of southern Ningxia as the research area, we used extended-exergy analysis (EEA) to compare their ecological efficiency driving mechanism in 2008-2017 to explore the causes of their variation in ecological degradation. The results showed that the overall difference of ecological efficiency in the three counties was significant during the study period. The ecological efficiency of Tongxin was low, with large inter-annual variation. The ecological efficiency of Xiji was stable, and the overall efficiency of Longde was the highest. The difference of exergy scale was small among the three counties. The exergy proportion in the economic sectors was not coordinated, which were dominated by agricultural and residential sectors. The economic sectors presented significant capital-pull-type and labor-intensive characteristics, indicating the driving force for ecological degradation mainly came from agricultural production and residents’ lives in underdeveloped regions. The system’s internal exergy conversion rate and the external energy exchange rate of the three counties were extremely low, constituting a simple network circulation path with high input, low storage, low opening and low conversion, which weakened the endogenous development of social economic subsystem and threatened the fragile ecosystem.

Spatial heterogeneity of soil fungal diversity in area with presence of Stellera chamaejasme on the degraded alpine meadow

LIU Yong-mei, ZHAO Fan, HE Wei, WANG Lei, LI Jing-zhong, LIU Jian-hong

2020, 31(1):  249-258.  doi:10.13287/j.1001-9332.202001.039

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Stellera chamaejasme is one of the most serious weeds in Qinhai-Tibetan Plateau, the rapid expansion of which exerts an increasing effect on the alpine meadow ecosystem. With high-throughput sequencing technology, geostatistics and GIS method, the spatial heterogeneity of soil fungal diversity in Stellera occurrence area and the spatial correlation between Stellera coverage and soil fungal diversity were investigated in a typical degraded alpine meadow of the Qilian Mountain. Compared to no-Stellera area, the fungi richness in Stellera area decreased, the dominance increased, and the α-diversity reduced. The difference of fungal species composition enhanced and β-diversity significantly increased. The spatial pattern of soil fungal diversity was affected by the invasion of Stellera, resulting in higher fragmentation in occurrence area. Spatial heterogeneity of species composition increased remarkably, and spatial stability of α-diversity and β-diversity decreased. The portion of positive correlation and negative correlation interlaced, indicating no clear spatial correlation between Stellera coverage and soil fungal diversity. Our results indicate that the spatial pattern of soil fungal diversity was affected by the interaction of soil and vegetation in Stellera invaded meadows.

Floral composition and ecological distribution of wood-decaying fungi in Laojunshan National Park, Southwest China

LI Jun-ning, LI Qiu-shi, WEI Yu-lian

2020, 31(1):  259-265.  doi:10.13287/j.1001-9332.202001.037

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Wood-decaying fungi are important components of forest ecosystem, mainly growing on the dead wood and decomposing lignin, cellulose, and hemi-cellulose. Understanding the ecological distribution of wood-decaying fungi are necessary to reveal their ecological function. In this study, we investigated wood-decaying fungi at three sites with different altitudes in Laojunshan National Park. Fruit bodies of fungi were collected and identified based on morphological and molecular analy-sis. In total 68 species were recorded, belonging to 40 genera, 21 families and 8 orders. Polyporaceae, Fomitopsidaceae, and Hymenochaetaceae were dominant families. The floral composition showed a distinct north temperate character, which was the most important element among all the bio-geographical elements with the highest percentage of 38.2%. These wood-decaying fungi can be divided into two ecological types: saprophytic (63 species) and ectomycohizal (5 species). Among these saprophytic fungi, 51 species could cause white rot and 12 species cause brown rot. The amounts of fungal species in deciduous broad-leaf forest (DBF), coniferous broad-leaved mixed forest (CBMF) and dark coniferous forest (DCF) were 34, 26 and 22, respectively. Postia fragilis and Stereum hirsutum, distributed in all the three types of forests, were dominant species of Laojunshan National Park.

Effect of N₂O produced by indigenous denitrifiers in oil reservoir on the physical properties of crude oil

LIU Chang, BAO Hong-xu, CUI Qing-feng, XIU Jian-long, ZHAO Feng, SHI Rong-jiu, HAN Si-qin, ZHANG Ying

2020, 31(1):  266-274.  doi:10.13287/j.1001-9332.202001.038

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The success of microbial enhanced oil recovery (MEOR) relies on complex microbial processes. Nevertheless, the contribution and mechanism of in-situ denitrification to microbial oil recovery remain unclear. In this study, eight denitrifying bacterial strains, designated T1, D1, D44, D46, D15, S1, S2 and S6, were isolated from the produced water of Xinjiang Oilfield, China, by a double layered plate method. The16S rDNA gene sequences of these denitrifying strains shared 100% similarity with Pseudomonas stutzeri (T1, D1, and D44), Pseudomonas putida (D46 and D15), and Pseudomonas aeruginosa (S1, S2, S6), respectively. The N₂O production effects of these strains on the physical properties of crude oil were evaluated with batch experiment. Results showed that the highest total gas yield was observed with sucrose as carbon source, and the maximal concentration of N₂O occurred with glycerol as carbon source. The denitrification process by these bacterial strains led to volume expansion and viscosity reduction of crude oil. Crude oil expansion rate was positively correlated with the concentration of N₂O, with a correlation coefficient of 0.983, but not correlated with the volume of total gas production. Strain S1, S2, and S6 produced 530-730 mg·L^-1 of surfactant using glycerol as ole carbon source, which could reduce surface tension and emulsify crude oil. However, these surfactant-producing strains produced less N₂O, exhibited weaker effects on oil swelling and viscosity reduction, compared to the none-surfactant-producing denitrifying strains. Our results suggested that more attention should be paid to the ability of N₂O production by denitrifying bacteria when exploiting microbial resources towards enhancing oil recovery.

Distribution and environmental characteristics of the spawning grounds of Scomberomorus niphonius in the coastal waters of Yellow Sea, China

WAN Rong, SONG Peng-bo, LI Zeng-guang, LONG Xiang-yu

2020, 31(1):  275-281.  doi:10.13287/j.1001-9332.202001.032

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Japanese Spanish mackerel (Scomberomorus niphonius) is one of the main economic fish species in the Yellow Sea. To understand its spawning habitat and population dynamics in the early stage, we examined the distribution and environmental characteristics of spawning ground of Japanese Spanish mackerel using their egg survey data collecting in 2015 (late May) and 2017 (late May) in the coastal waters of Yellow Sea. The generalized additive model (GAM) with the Tweedie distribution was used to analyze the distribution and environmental characteristics of its spawning ground. The results showed that egg distribution was significantly related to the location (i.e., latitude and longitude), water depth, and sea surface temperature (SST), but not related to sea surface salinity (SSS). The optimal range of depth and SST were 15-30 m and 16-20 ℃, respectively. The mackerel spawning ground mainly distributed in the region Shidao fishing ground (area near 36°30′ N,121°48′ E) and Haizhou Bay (33°30′-36° N,119°30′-121°30′ E). There were some clear inter-annual differences in the distribution of mackerel spawning ground, with the spawning ground tending to northward in the year with higher sea temperature. Therefore, it is necessary to manage and protect the above spawning ground (especially the Haizhou Bay), establishing the corresponding ecological protection and restoration strategy, to realize sustainable exploitation of mackerel fisheries resources in the Yellow Sea.

Characteristics of seawater nutrients during the occurrence of brown tide in the coastal area of Qinhuangdao, China

ZHANG Jian-le, WANG Quan-ying, ZHANG Yong-feng, ZHANG Wan-lei, LI Li

2020, 31(1):  282-292.  doi:10.13287/j.1001-9332.202001.009

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Brown tide that occurred in Qinhuangdao coastal waters from 2009 to 2015 caused huge losses of local marine aquaculture and coastal tourism, with devastating effects on marine ecosystems. Nutrients are important biogenic elements for algal growth. It is of great significance to examine the fluctuation characteristics of nutrients in the process of brown tide to understand the nutritional mechanism of brown tide. Based on the survey data of 30 stations located in Qinhuangdao coastal area from April to June 2014, we analyzed nutrient characteristics during the occurrence of brown tide and its relationship with the population dynamics of Aureococcus anophagefferens. The results showed that the concentration of dissolved nitrogen (DN) in April, May and June 2014 was 265.65, 355.36 and 323.71 μg·L^-1 respectively, and the concentration of dissolved organic nitrogen (DON) was 196.98, 242.88 and 177.69 μg·L^-1, accounting for 74.2%, 68.3% and 54.9% of DN, respectively. The concentration of dissolved phosphorus (DP) in April, May and June was 15.95, 11.39 and 11.14 μg·L^-1 respectively. In April and May, PO₄^3--P accounted for a large proportion of the DP, 74.8% and 80.9% respectively. In June, the proportion of PO₄^3--P in DP fell to 33.8%, and the proportion of dissolved organic phosphorus (DOP) in DP rose to 66.2%. The concentration of SiO₃^2--Si in April, May and June was 70.95, 181.13 and 120.68 μg·L^-1, respectively. Except for dissolved inorganic nitrogen (DIN) in May and DON, the distribution of other nutrients had clear characteristics that it decreased gradually from inshore to the offshore, with the relatively high concentrations in river mouth. Through R-factor analysis and nutrient structure analysis, it was found that in April, brown tide was at the development stage, and DOP might be the main driving factor for the growth of A. anophagefferens. In May, brown tide was at the maintenance stage, and water temperature became the main controlling factor. When water temperature was higher than 12 ℃, brown tide could occur. In June, brown tide began to decay, and PO₄^3--P had greater effects on the community structure of phytoplankton. DON was the important factor causing the outbreak of brown tide, with a concentration threshold of 150 μg·L^-1 and the ratio DON/DIN being greater than 1.

Interspecific association of main fish species in the Haizhou Bay and its adjacent waters

WANG Jiao, ZHANG Chong-liang, XUE Ying, REN Yi-ping, XU Bin-duo

2020, 31(1):  293-300.  doi:10.13287/j.1001-9332.202001.036

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It is important to reveal the interspecific association and correlation of main species for deep understanding of fish community structure and function. Based on data collected from the bottom trawl surveys from 2013 to 2017 in the Haizhou Bay and the adjacent waters, we analyzed interspecific association of main species using Chi-square test, Jaccard index, and Spearman rank correlation coefficient. There were consistent results from χ²-test, Jaccard index, and Spearman’s rank correlation analysis. The proportion of positively correlated species pairs was high in different years, whereas the number of significant or extremely significant species pairs was low. There were 9, 6, 7, 1, 0 significant or extremely significant species pairs over different years based on Jaccard index. There were 12, 20, 13, 5, 6 significant or extremely significant species pairs over different years based on Spearman’s rank correlation coefficient. While there were inter-annual changes in related species pairs, the relationship between significant species pairs was relatively stable, indicating a relatively stable interspecific association in the main fish communities. The species within the same ecological type could replace each other in the niche, which have adapted to environmental changes in Haizhou Bay and its adjacent waters.

Trophic level of main organisms in coastal water of Lyusi fishing ground based on stable isotope method

GAO Shi-ke, YU Wen-wen, ZHANG Shuo

2020, 31(1):  301-308.  doi:10.13287/j.1001-9332.202001.031

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We measured the ratio of δ¹³C and δ¹⁵N values to estimate the trophic level of main organisms based on a fisheries resource survey in coastal water of Lyusi fishing ground carried out in September 2018. The results showed that δ¹³C values of the main organisms ranged from -24.27‰ to -13.24‰, with an average of (-17.15±1.85)‰. The δ¹⁵N values ranged from 4.30‰ to 14.61‰, with an average of (11.21±1.90)‰. Results from cluster analysis demonstrated that the main organisms in the coastal water of Lyusi fishery ground could be divided into four trophic groups. The first group was consisted mainly by middle and small fishes, shrimps and other invertebrates. The second group included the small-sized fishes like Konosirus punctatus, Mugil cephalus, etc. and shrimps like Exopalaemon annandalei, Exopalamon carincauda, etc. The phytoplankton belonged to the third group. The fourth group was zooplankton. In the trophic spectrum, the trophic levels of fish, shrimps and crabs, shellfish were 3.2-4.7, 3.2-4.2 and 2.0-4.1, respectively. Most species belonged to the category of middle and high-level consumers. In this survey, the average trophic level of the same species in the coastal waters of Lyusi fishing ground was 0.6, which was higher than that in the East China Sea and Yellow Sea. There was niche overlap of most fish, shrimps and crabs. Those results indicated the growth environment and nutrient structure of most living organisms in this area were generally similar.

Prediction of potential distribution of the invasive species Procambarus clarkii in China based on ecological niche models

XIAO Qi, ZHANG Meng-ting, WU Yi, DING Hui, LEI Jun-cheng, ZHU Shan-liang, ZHANG Zhen-hua, CHEN Lian

2020, 31(1):  309-318.  doi:10.13287/j.1001-9332.202001.029

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Procambarus clarkii was introduced into China as an important aquatic product in early 20th century. It has characteristics of high fertility, rapid growth, adaptability and digging burrows, which could cause damage of crops, cropland and facilities, decrease local biodiversity and thus threaten local ecosystem. Thus, predicting the potential distribution of P. clarkii in response to climate change was essential for preventing and monitoring this species. Based on the distribution of P. clarkii, the maximum entropy (MaxEnt) and genetic algorithm for rule-set production (GARP) models were used to predict its distribution in China under current climate and four climate scenarios (RCP 2.6, RCP 4.5, RCP 6.0, RCP 8.5) in two periods, 2041-2060 and 2061-2080. Then, the modeling results were tested by ROC curves. The results showed that under current climate, the highly suitable region for distribution predicted by the MaxEnt and GARP models were Shanghai, Jiangsu, Zhejiang and Anhui along the Yangtze River. The main environmental variables affecting its distribution were mean temperature of the coldest quarter, minimum temperature of the warmest month, and temperature seasonality, maximum temperature of the warmest month, precipitation of the driest month. Under the future climate scenarios, the suitable area of P. clarkii distribution varied in 2061-2080. The total suitable area of P. clarkii would increase under RCP2.6 and RCP 4.5, whereas under RCP 8.5 the suitable area of P. clarkii would increase, and then decrease. In RCP 6.0, there was no change. The suitable areas of P. clarkii would disperse to different latitude areas and migrate toward high altitude.

Food source and feeding habit of Helice tientsinensis from the common reed vegetation in high marsh of Yellow River Delta, China

LAN Si-qun, ZHANG Li-wen, YI Hua-peng, XU Chang-lin, LU Feng, FENG Guang-hai, HAN Guang-xuan

2020, 31(1):  319-325.  doi:10.13287/j.1001-9332.202001.034

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Investigating the composition of food sources with stable isotope method can provide direct evidence for the top-down control in the coastal wetland. In this study, we examined food source and feeding habit of Helice tientsinensis of common reed (Phragmites australis) vegetation in high marsh of Yellow River Delta. The results showed that the density of crab was (5.5±1.5) ind·m^-2, with the behavior of climbing P. australis to feed on the leaves at night. Under the same indoor experimental condition, H. tientsinensis showed feeding preference on fresh leaves of P. aus-tralis. The stable isotope food source analysis showed that the leaves of P. australis were one of the important food sources of H. tientsinensis in the field. There were temporal variations in the proportion of fresh leaves [May: (6.4±4.9)%, July: (5.8±4.9)%, September: (12.5±8.8)%] and dead leaves [May: (12.4±7.8)%, July: (15.5±9.9)%, September: (15.1±9.4)%]. Therefore, H. tientsinensis could inhibit P. australis’s growth and affect litter decomposition through feeding disturbance behavior.

Isolation and screening of a phytate phosphate-solubilizing Paenibacillus sp. and its growth-promoting effect on rice seeding

QU Lu-lu, PENG Chang-lian, LI Shu-bin

2020, 31(1):  326-332.  doi:10.13287/j.1001-9332.202001.033

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The phosphate-solubilizing medium plate screening and heavy metal resistance rescreening were used to isolate a phosphate-solubilizing bacterium (coded ZLT11) from the rhizosphere of Mikania micrantha. Results from 16S rRNA gene sequence analysis revealed that the strain ZLT11 belonged to Paenibacillus sp. The amount of phosphorus solubilized from calcium phytate and phytic acid by the ZLT11 was 84.10 and 73.84 mg·L^-1, respectively. The maximum phosphate solubilizing activity to calcium phytate (95.66 mg·L^-1) was at 30 ℃ and initial pH 9.0. The strain ZLT11 displayed the tolerance to ≤ 400 mg·L^-1 Pb ²⁺, ≤ 100 mg·L^-1 Cd ²⁺, and ≤ 40 mg·L^-1 Hg ²⁺. With calcium phytate as phosphorus source, the inoculation strain ZLT11 treatment increased the average root length, root number, seedling height and total biomass of rice seedlings by 106.7%, 76.6%, 49.0% and 46.3%, respectively. The strain ZLT11 could improve rice seedlings growth under Cd stress.

Mechanism underlying photocatalyzed degradation of methyl orange by layered black phosphorus

HAN Ya-qi, LEI Lei, YANG Chen, ZHANG Si-yu, ZHAO Qing, ZHANG Xue-jiao

2020, 31(1):  333-339.  doi:10.13287/j.1001-9332.202001.035

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A large amount of azo dye wastewater is discharged into the environment, with serious risks to ecosystems and human health. Therefore, the development of treatment technology of azo dye wastewater was of practical significance. Photocatalytic methods showed promising application prospects due to easy to implement and effective. In this study, layered black phosphorus nanosheet (LBP) was used as a catalyst through liquid phase exfoliation method. Methyl orange (MO) was employed as a model azo dye to investigate the catalytic mechanism of LBP. The dominant transient species involved in the photocatalytic reaction was probed by quenching and fluorescence probe experiments. Degradation pathways of MO were proposed according to degradation products identified by the liquid chromatography-mass spectrometry. The results showed that degradation rate (k_obs) of MO at acidic condition (pH=3.0) or alkaline condition (pH=11.0) was higher than that at neutral condition (pH=7.0). Degradation pathways of MO included that the azo bond was attacked by hydroxyl radicals (·OH) photogenerated by the LBP, and the intermediate products were further oxidized by ·OH to produce N, N-dimethyl-4-(2-p-phenylmethylhydrazine) aniline, 2-(dimethylamino)-5-((4(dimethylamino) phenyl) diazenyl) phenol and N, N-dimethyl-4-nitroaniline.

Reviews

Research progress on the relationship between biodiversity and ecosystem services

WEN Zhi, ZHENG Hua, OUYANG Zhi-yun

2020, 31(1):  340-348.  doi:10.13287/j.1001-9332.202001.003

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The relationship between biodiversity and ecosystem services is one of the hot topics in ecological research. The ways that the relationship is applied to the development of ecosystem management and policy have gradually gained attention after the Millennium Ecosystem Services Assessment in 2005. However, applying theoretical understanding of the relationship into practical management still faces challenges. Examining recent progresses may help to guide practices and po-licies. We summarized recent progress in researches on the relationship between biodiversity and ecosystem services in terms of the impacts of biodiversity on single ecosystem service, ecosystem multifunctionality and trade-offs of ecosystem services, as well as how environmental changes affected these relationships. Moreover, we outlined the application of these relationships in nature reserve management, forest management, degraded ecosystem restoration, and agro-ecosystem improvement. We further analyzed the shortcomings in relationship studies and then emphasized that future research and practice trends are the interaction of different biodiversity components and multiple trophic levels on ecosystem services, the coupling effects of environmental changes on the relationships, and practical approaches to biodiversity for improving ecosystem services.