Table of Content

10 June 2021, Volume 40 Issue 6

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Effects of poplar plantation types on soil phosphorus fractions.

WANG Ya-ru, LIN Xin-yu, HUI Hao, SUN Xiao-dan, CHEN Bin, PAN Yu-yang, CHEN Jian-wei, GUAN Qing-wei

2021, 40(6):  1549-1556.  doi:10.13292/j.1000-4890.202106.015

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Phosphorus is an important limiting nutrient in subtropical forest ecosystems. Clarifying the effects of different poplar plantation types on soil phosphorus fractions is important for the scientific management of poplar plantation in subtropical region. In this study, Populus euramericana pure forest (PE), Populus euramericana +Photinia serrulata mixed forest (PS), and Populuseuramericana+Ligustrum lucidum mixed forest (PL) were selected as the objects. The Hedley phosphorus fraction method modified by Sui was used to examine the effects of different poplar plantation types on soil phosphorus fractions in soil layers of 0-20, 20-40, and 40-60 cm. The results showed that the contents of total phosphorus, total organic phosphorus, available phosphorus, active phosphorus (H₂O-Pi, NaHCO₃-Po, NaHCO₃-Pi) and moderately active phosphorus (NaOH-Po, NaOH-Pi) were higher in the two mixed forests than PE, with stronger effects in PL than PS. The content of available phosphorus in 0-60 cm soil layer of PS and PL was 52.4% and 55.3% higher than that of PE, respectively. Total inorganic phosphorus in 0-20 cm soil layer of PL was significantly decreased. In the 0-20 cm soil layer, the content of NaOH-Pi in the mixed forests was significantly higher than that in the PE, while the contents of H₂O-Pi and NaHCO₃-Pi in the 20-40 cm soil layer and the contents of total phosphorus, total organic phosphorus and NaHCO₃-Po in the 0-40 cm soil layer of both mixed forests were significantly higher than that of the pure forest. The contents of soil phosphorus fractions generally decreased with soil depth. Results of redundancy analysis showed that acid phosphatase activity, soil microbial biomass P and soil total organic carbon were important factors affecting the changes of soil phosphorus fractions. Compared with the pure forest, the multi-layered mixed forest of tree and shrub species can improve soil phosphorus availability and alleviate the phosphorus limitation in subtropical regions.

Coefficients and influencing factors of biomass estimation of Masson pine forest.

YUAN Feng, CHEN Can, XIA Xin-hui, LIU He-na, LI Mao-jin, WU Cheng-zhen

2021, 40(6):  1557-1566.  doi:10.13292/j.1000-4890.202106.019

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To accurately estimate Masson pine forest biomass in China, we analyzed the estimation coefficients including the biomass conversion and expansion factor (BCEF), the biomass expansion factor (BEF), and the ratio of root to stem (R) with their influencing factors based on the data from related literature from 1982 to 2019. The results showed that the average values of BCEF, BEF and R were 0.723±0.138 t·m^-3, 1.390±0.184 and 0.167±0.024, respectively. BCEF, BEF and R all gradually decreased with increasing stand age (r²=0.329, 0.430 and 0.315, respectively) and stand stock volume (r²=0.513, 0.528 and 0.337, respectively), and gradually tended to be stable. BCEF, BEF and R all decreased first and then increased with increasing average tree height, with a fitting accuracy of 0.370, 0.506 and 0.239, respectively. BCEF decreased gradually with increasing average  diameter at breast height (r²=0.306). BEF decreased first and then increased with increasing average diameter at breast height (r²=0.531). There was no relationship between biomass estimation coefficients and climatic factors. R increased with slope (r²=0.298) and increased gradually with altitude (r²=0.277), while BCEF decreased first and then increased with altitude (r²=0.365). Natural pruning during the growth of Masson pine resulted in different stand structure. The slope and altitude would affect plant growth by affecting the availability of light, heat, and water. Hence, the stand structure and topographic factors had a higher degree of fitting with the biomass estimation coefficients. Therefore, the role of stand structure and topography should be considered when estimating the biomass of Masson pine by using biomass estimation coefficients.

Nitrogen and phosphorus interception effects in surface runoff of Pinus massoniana plantation in Danjiangkou reservoir area.

CHENG Chang-jin, ZHANG Jian, SONG Han-qing, LEI Gang, LIU Xue-quan, QI Liang-hua

2021, 40(6):  1567-1573.  doi:10.13292/j.1000-4890.202106.021

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Riparian vegetation buffer zone can effectively remove nonpoint source pollutants from surface runoff. We used the method of simulating surface runoff to investigate the interception effect on pollutants and the influencing factors of different width riparian vegetation buffer zone of four Pinus massoniana plantations with slopes of 11°, 15°, 17° and 21° in the Danjiangkou reservoir area. Soil permeability was measured by double ring infiltration test. Soil density and maximum water-olding capacity were measured by ring knife method. The thickness and biomass of litter under different slopes were measured. The results showed that slope, width, litter thickness and litter biomass were the main factors affecting the interception rate. Under the four slope conditions, the interception rate increased with the width and decreased with the slope. To obtain 80% of interception rate of four non-oint source pollutants, the width of buffer zone should be about 34 m when the slope of the riparian vegetation buffer zone was 11°, about 40 m for the slope of 15°, 45 m for the slope of 17°, and 48 m for the slope was 21°. Our results provide reference for the construction and management of riparian vegetation buffer zone of Pinus massoniana plantations in the reservoir area.

Response of radial growth of Juniperus seravschanica to climate changes in different environmental conditions.

GOU Xiao-xia, ZHANG Tong-wen, YU Shu-long, ZHANG Rui-bo, JIANG Sheng-xia, GUO Yu-lin

2021, 40(6):  1574-1588.  doi:10.13292/j.1000-4890.202106.025

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In this study, tree ring samples of Juniperus seravschanica were collected from three sites in the Kuramenian Mountains, which were used to develop three treering width chronologies. Results of climate-growth response analysis showed that the radial growth of trees showed different responses to temperature and precipitation at different slope directions and at different altitudes. The radial growth of trees at high altitude (2000 m) was mainly affected by precipitation in the current growing season on the northern slope, and was mainly limited by temperature in the previous and current growing seasons on the southern slope. Temperature at the end of the current growing season significantly affected the radial growth of J. seravschanica on the southern slope at low altitude (1600 m). Results of moving correlation analysis and u tests revealed differences in the relationships between the radial growth of J. seravschanicaand climate factors in different sites. The response period of the radial growth of J. seravschanica differed among different sites due to climatic variations. The positive correlation between treering width chronology and precipitation in May-June in the current season was slightly stronger at high altitude on the northern slope. The radial growth of J. seravschanica was mainly affected by temperature at high altitude on the southern slope, which reflected a strong positive correlation between the radial growth of trees and temperature in the previous May and a strong negative correlation between the radial growth of trees and temperature in the previous December. The radial growth of trees at low altitude on the southern slope and at high altitude on the northern slope showed increasingly negativeresponseto precipitation at the end of the growing season.

Responses of decomposition of naturally senescent and green leaf litter to thinning intensity and fertilization in Chinese fir plantation.

YU Tan-wei, GE Zhi-qiang, YAN Qiang, LI Meng-jiao, HONG Xiao-min, CHEN Tian, HU Ya-lin

2021, 40(6):  1589-1598.  doi:10.13292/j.1000-4890.202106.018

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Litter decomposition is an important process of energy flow and nutrient cycling in forests. Leaf litter includes naturally senescent leaf litter (SL) and green leaf litter (GL). It is not clear whether the responses of litter decomposition and nutrient releases between SL and GL to thinning intensity and fertilization in plantations are different. In this study, we compared the effects of thinning intensity and fertilization management on the decomposition rate and nutrient releases of C, N and P in the naturally senescent and green leaf litter in a 13-year-old Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantation. Our results showed that the dynamics of decomposition and nutrient release were similar between SL and GL. The decomposition rate and litter C, N and P releases were significantly faster in GL than SL. The remaining rates of dry matter in SL and GL were 58.4% and 40.5% after 1-year decomposition, respectively. Thinning intensity did not affect decomposition rate and the remaining rates of litter C, N, and P. Fertilization decreased dry matter remaining rate under medium thinning, but increased leaf litter N and P concentrations and the remaining rate of P content. Our results implied that litter chemical properties was one of the most important factors controlling litter decomposition rate and nutrient releases, and highlighted that reserving green leaf litter derived from thinning management was necessary to maintaining soil nutrient in Chinese fir plantations.

Quantity and optical characteristics of dissolved organic matter derived from decomposing leaf litter on the ground and in the air in typical subtropical plantations.

DING Yi-dong, XU Jiang-qi, ZHENG Jiao, WU Pan-pan, MAO Rong

2021, 40(6):  1599-1608.  doi:10.13292/j.1000-4890.202106.004

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In this study, we collected leaf litter from four main afforestation species (i.e., Liquidambar formosana, Schima superba, Pinus massoniana, and Pinus elliottii) in subtropical regions of Jiangxi Province. Litter was decomposed for 150 and 360 days in the air and on the ground. Then, we assessed the effects of decomposition position on the amount, C∶N∶P stoichiometry and ultraviolet-visible absorbance optical properties of litterderived dissolved organic matter (DOM) in subtropical plantations. After 150 days decomposition, L. formosana,P. massoniana, and P. elliottiilitter decomposed on the ground produced higher dissolved organic carbon (DOC) amounts than those in the air, whereas the pattern of S. superba litter was opposite. After 360 days of decomposition, the effect of decomposition position on litter-derived DOC production was species-specific. After 150 days of decomposition, C∶N, C∶P, and N∶P ratios were higher in the leachate of tree litter decomposed in the air than those on the ground. The effect of decomposition position on C∶N∶P stoichiometry was dependent on litter type after 360 days of decomposition. Litter of broad-leaved tree species (L. formosana and S. superba) decomposed in the air often had lower SUVA₂₅₄, SUVA₂₈₀, and SUVA₃₅₀ values (i.e., lower aromaticity of DOM), but higher S_275-295 and S_350-400 values (i.e., lower molecular weight) in the leachates than that on the ground after 150 and 360 days of decomposition. For coniferous trees (P. massoniana and P. elliotti), litter-derived DOM aromaticity and molecular weight were lower in the air than on the ground after 150 days of decomposition, but greater after 360 days of decomposition. These results suggest that decomposition position is an important factor determining the quantity and quality of litter-derived DOM in subtropical plantations, and such effect is regulated by tree species and the stage of decomposition.

Effects of adding exogenous carbon with different chemical structure on the dynamics of organic carbon mineralization in red and sandy soils.

LI Meng-jiao, CHEN Tian, HONG Xiao-min, YU Tan-wei, HU Ya-lin

2021, 40(6):  1609-1617.  doi:10.13292/j.1000-4890.202106.002

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Exogenous organic carbon input is one of the most important factors regulating the balance of soil organic carbon (SOC) input and output. The effects of adding exogenous carbon with different chemical structures to soils with different textures on the CO₂ emission from mineralization of organic carbon are still unclear. In this study, we added four kinds of exogenous carbon (sucrose, starch, cellulose and lignin) to red soil and sandy soil with different texture, and compared the impacts on CO₂ release rates, cumulative amount and its proportion of CO₂-C loss. The aim of our study is to provide new insights on how soil texture and chemical structure of exogenous carbon drive soil organic carbon turnover. Our results showed that exogenous carbon addition increased CO₂ release rates, cumulative amounts, and the proportion of C loss, with the magnitude of such impacts varying among different exogenous carbon treatments. Soil texture had significant effects on CO₂ release rates, cumulative amounts, and the proportion of C loss. There were significant interactions between exogenous carbon and soil texture. Sandy soil had higher CO₂release rates, cumulative amounts and C loss proportion than red soil. The dynamics of CO₂release rates differed among exogenous carbon treatments. The peak values of CO₂ release rate in the complexstructured organic carbon treatments were usually delayed as compared to sucrose addition. Our results suggest that the effects of exogenous carbon addition on the organic carbon mineralization are closely related to the chemical structure of exogenous organic carbon and soil texture.

Effects of Larix gmelinii stand age on composition and organic carbon content of soil aggregates.

WANG Bing, ZHOU Yang, ZHANG Qiu-liang

2021, 40(6):  1618-1628.  doi:10.13292/j.1000-4890.202106.017

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We explored the effects of Larix gmelinii forest age on distribution, stability and organic carbon content of soil aggregates, based on 28 plots with different forest ages (young, middle-aged, near-mature, mature and over-mature). We measured soil physicochemical indices, soil aggregates and their organic carbon content in different soil layers. The results showed that: (1) The proportion of microaggregates (0.053-0.25 mm) was the lowest in all ages of L. gmelinii forest. Except for the near-mature forest, soil aggregates in all forests were dominated by macroaggregates (0.25-2 mm), accounting for 44.13%-50.34% of the total aggregate content. With increasing stand age, macroaggregate (0.25-2 mm), mean weight diameter (MWD) and geometric mean diameter (GMD) decreased at first and then increased. (2) The organic carbon content of soil aggregates in different aged L. gmeliniiforests was the highest in the 0.25-2 mm and the lowest in the 0.053-0.25 mm aggregates. The organic carbon content of soil aggregates in each particle size decreased with increasing soil depth. (3) Soil macroaggregate content, MWD, GMD and organic carbon content of soil aggregates were significantly positively correlated with total organic carbon, soil water content, available potassium and total phosphorus, and negatively correlated with soil pH and metal oxide content. The relationships between soil microaggregate content and soil physicochemical indices were opposite to that of macroaggregate. Forest age affected distribution, stability and organic carbon content of soil aggregates in L. gmelinii forest. Organic matter and metal oxides contributed to the formation and stability of macroaggregates (0.25-2 mm) and microaggregates (<0.25 mm), respectively.

Temporal and spatial variations of water potential and hydraulic conductivity of typical plant species in Badain Jaran Desert.

QIN Jie, SI Jian-hua, JIA Bing, ZHAO Chun-yan

2021, 40(6):  1629-1638.  doi:10.13292/j.1000-4890.202106.016

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We measured soil water potential, plant water potential, and hydraulic conductivity of four typical plant species, namely Zygophyllum xanthoxylon, Artemisia ordosica, Ferula bungeana, and Nitraria tangutorum, in different locations of high sandy mountains in the Badain Jaran Desert and at different distances from the lake, with the aim to uncover the mechanisms of water transport. The results showed that: (1) water potential values shared the same characteristics for all the four plant species, namely, root>stem>leaf. Among those species, the averagewater potential of various organs of the shrub N. tangutorum was the lowest, while that of the perennial herbaceous F. bungeana was the highest. In terms of location, the same species had the lowest water potential in the upper part of the sandy mountain, and the highest in the lower part of the sandy mountain. The lowest and highest water potential of each organ of N. Tangutorumwas obtained at 100 m and 20 m away from the lake, respectively. In terms of diurnal variation, water potential values of all species were the highest before dawn. (2) Soil water potential of all plots fluctuated and rose with increasing soil depth. (3) Among the four species, hydraulic conductivity was highest in Z. xanthoxylonand lowest in F. bungeana. In terms of location, hydraulic conductivity of all species on the sandy mountain shared the same characteristics, namely, upper part > middle part > lower part. The hydraulic conductivity of N. Tangutorum at different distances from the lake showed as 20 m away from the lake < 50 m away from the lake < 100 m away from the lake. In terms of diurnal variation, hydraulic conductivity of all species was the lowest at midday. Our results suggest that plant water potential and hydraulic conductivity were positively correlated and that there is an adaptive water transport strategy for plants to maintain their water balance and support their growth in special habitats.

Effects of biofertilizer and rotten straw on soil salinity and oat quality in saline alkaline soil.

LU Pei-na, LIU Jing-hui, ZHAO Bao-ping, YANG Yan-ming, MI Jun-zhen, MA Bin, LIU Min

2021, 40(6):  1639-1649.  doi:10.13292/j.1000-4890.202106.003

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We explored the effects of organic amendments under continuous cropping of oat on alkali-saline soils and oat quality in the Haitu Saline-alkali Experimental Station of Inner Mongolia Agricultural University during 2016-2018. There were four treatments, including control (CK), biofertilizer (F), rotten straw (S), and combined bio-fertilizer and rotten straw (FS). We measured soil pH, watersoluble salt ions concentration, and oat quality. The results showed that soil pH, salt content, and the concentrations of Ca²⁺, Mg²⁺, Na⁺, HCO₃^-+CO₃^2- and SO₄^2- gradually decreased, while the K⁺ and Cl^- contents increased in the 0-40 cm for all treatments with the increasing planting years of oats. Compared to the pre-improvement in 2016, the contents of soil cations (Ca²⁺, Mg²⁺, Na⁺) were decreased by 80.22%, 82.78%, 78.24% and 80.87%, and the soil SO₄^2- contents were decreased by 63.91%, 77.87%, 56.27% and 80.88%, while the soil K⁺ contents were increased by 142.00%, 171.88%, 49.65% and 93.28% in CK, F, S, FS treatments in 2018, respectively. FS treatment significantly increased crude protein content by 4.04%, increased crude fat content by 9.09%, increased K⁺ content by 6.30%, and increased Na⁺ content by 40.00% for oat grains and significantly increased crude protein content by 21.26%, neutral detergent fiber content by 2.09%, acid detergent fiber content by 4.25%, and K⁺ content by 71.24% for oat plants. The crude fat content of oat plants was significantly decreased by 6.34% after three years of improvement. Compared to CK, the correlation between soil properties and oat quality was weakened in FS treatment during the process of improvement. Therefore, the combined application of bio-fertilizer and rotten straw could effectively relief soil salinity and improve oat grain and forage qualities on saline-alkali land.

Effects of N, P, and K fertilization on yield and quality of Ginkgo biloba fruit and sarcotesta.

FENG Jia-yi, XIE Shan-yan, WU Dao-ming, OUYANG Jian-hui, ZENG Shu-cai

2021, 40(6):  1650-1659.  doi:10.13292/j.1000-4890.202106.022

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We examined the effects of different combinations of N, P, and K fertilizers on the yield and quality of Ginkgo biloba fruit and sarcotesta, with the aim to provide a theoretical basis for the oriented cultivation of fruit-harvesting Ginkgo biloba and the resource utilization of sarcotesta. Different combinations of N, P, and K fertilizer application were set up, including N fertilizer+P fertilizer (T1), N fertilizer+K fertilizer (T2), P fertilizer+K fertilizer (T3), N fertilizer+P fertilizer+half of K fertilizer (T4), N fertilizer+half of P fertilizer+K fertilizer (T5), half of N fertilizer+P fertilizer+K fertilizer (T6), N fertilizer+P fertilizer+K fertilizer (T7), with no fertilizer application as the control (CK). We measured the characteristics and yield of Ginkgo biloba fruit and sarcotesta, the contents of flavonoids in sarcotesta and the total flavonoids yield of sarcotesta under different treatments. The correlation between fruit and sarcotesta parameters was analyzed. The comprehensive evaluation of different treatments was carried out by the membership function and principal component analysis. Results showed that fertilization significantly increased the size and fresh weight of single fruit, fruit quantity, fruit yield, and dry weight of sarcotesta. The fruit number in T6 (2096 grains·plant^-1) was the higher, while the yields of sarcotesta in both T2 (2.59 kg·plant^-1) and T6 (2.43 kg·plant^-1) were significantly higher than that of other treatments. Furthermore, all fertilizer applications significantly increased the contents of quercetin and total flavonoids in the sarcotesta. The yield of total flavonoids in T2 treatment (658.32 mg·plant^-1) was the highest. The yield of sarcotesta and fruit quantity was significantly correlated with fruit yield (P<0.01). The correlation between total flavonoids yield of sarcotesta and fruit and sarcotesta indices except sarcotesta thickness was also significant (P<0.01). The order of comprehensive effects of fertilization on fruit and sarcotesta was T2>T6>T4>T3>T5>T1>T7>CK. T2 \[the combined application of N fertilizer (0.20 kg N·plant^-1) and K fertilizer(0.24kg K₂O·plant^-1)\] was the optimal fertilization scheme for yield and quality of fruit and sarcotesta, followed by T6 \[the combined application of half of N fertilizer (0.10 kg N·plant^-1), P fertilizer (0.32 kg P₂O₅·plant^-1) and K fertilizer (0.24 kg K₂O·plant^-1)\]. Our results indicated that reducing fertilizer amount did not decrease yield but had better fertilization effects on yield and quality. In practice, fertilizer application scheme should be optimized to improve fertilizer utilization rate.

 

Point pattern analysis of Ligularia virgaurea and Potentilla fragarioides populations in Maqu alpine meadow.

ZHANG Guo-juan, LIU Min-xia, LI Bo-wen, MU Ruo-lan, YU Rui-xin, XU Lu, LI Liang

2021, 40(6):  1660-1668.  doi:10.13292/j.1000-4890.202106.001

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Studies of the spatial distribution of plant populations are an important means to reveal the alteration of plant population, community, and ecosystem with environmental changes. In this study, we investigated the spatial pattern of two dominant species Ligularia virgaurea and Potentilla fragarioides in alpine meadow of Gannan under different groundwater depths of 0.1, 0.5 and 1.0 m, using Ripley K function. The results showed that: (1) with increasing groundwater depth, the contents of soil water and soil nutrients (SOC, STN, STP) decreased gradually; the individual abundance, plant height, biomass and coverage of L. virgaureapopulation decreased first and then increased, while these parameters of P. fragarioides population showed gradual decrease patterns. (2) When the groundwater depth was 0.1 m, the whole L. virgaurea population showed an aggregation distribution, while the P. fragarioides population showed a random distribution. When the groundwater depth was 0.5 m, L. virgaureapopulation showed an aggregation distribution at a large scale. With increasing scale, the aggregation degree gradually reduced, and finally reached a random distribution. At the scale of 0-2.9 m, the population of P. fragarioides showed an aggregation distribution, while at the scale of 2.9-3.6 m and 3.6-5 m, it showed a random distribution and an uniform distribution, respectively. When the groundwater depth was 1.0 m, L. virgaurea population showed an aggregation distribution and a random distribution in the range of 0-2.3 m and 2.3-5 m, respectively. P. fragarioides population showed an aggregation distribution in the range of 0-4.4 m, and tended to be a random distribution in the range of 4.4-5 m. (3) When the groundwater depth was 0.1 m, the two populations were negatively correlated at the whole scale. When the groundwater depth was 0.5 m, the two populations were uncorrelated. When the groundwater depth was 1.0 m, the two populations were positively correlated at small scale, and gradually became uncorrelated with increasing scale.

Effects of nitrogen and phosphorus addition on soil nutrients and plant biomass in a typical Poyang Lake marshland.

WEN Min, HU Qi-wu, YANG Wen-jing, WU Qin, YAO Bo

2021, 40(6):  1669-1676.  doi:10.13292/j.1000-4890.202106.035

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Under constant anthropogenic disturbance, it is critical to understand the response of wetlands to nitrogen (N) and phosphorus (P) addition for protecting and maintaining wetland ecosystem functions. To evaluate the effects of N and P addition on soil nutrients and plant biomass in wetlands, a field experiment was conducted in a typical Carex wetland from the Poyang Lake Nanji National Nature Reserve. There were seven treatments: control, three levels of N addition (5, 10 and 30 g N·m^-2·a^-1), and three levels of P addition (0.6, 1.2 and 3.0 g P·m^-2·a^-1). The results showed that N and P addition significantly increased soil total and available N and P concentrations. Both the above and below ground biomass of Carex community significantly increased with increasing N and P addition levels. The effects of N and P addition on the root/shoot ratios ofCarex community were different, in that N addition reduced but P addition increased the root/shoot ratios. Both total and available contents of the corresponding added elements in soils were closely related to plant biomass. Overall, soils and plants in the Poyang Lake wetlands were relatively sensitive to N and P inputs.

Effects of coupling of soil type and nitrogen application level on rice yield and nitrogen use efficiency.

MA Jun, XU Tian, YE Ying, ZHAO Kao-cheng, LIN Yi-cheng, SHA Lin-xian, ZHU Tao, ZHUANG Heng-yang

2021, 40(6):  1677-1686.  doi:10.13292/j.1000-4890.202106.032

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To clarify the effects of soil type and nitrogen (N) application level on rice yield and N use efficiency, we conducted a field experiment with four N application levels (N₀ (0 kg N·hm^-2), N₁ (180 kg N·hm^-2), N₂ (270 kg N·hm^-2) and N₃ (360 kg N·hm^-2)) under yellow clay and sandy loam soils with rice cultivars ‘Nanjing 9108’, ‘Yangjing 4227’, ‘Zhendao 18’ and ‘Nanjing 46’ as experiment materials. The results showed that, except for the N₂ treatment of ‘Zhendao 18’, the yields of the other varieties under all N treatments under the yellow clay were significantly higher than that under the sandy loam. The yields of ‘Nanjing 9108’, ‘Yangjing 4227’, ‘Zhendao 18’ and ‘Nanjing 46’ under the yellow clay soil were 23.1%-87.4%, 12.2%-39.8%, -1% to 34.7% and 2.2%-20.9% higher compared with the yields under the sandy loam soil, respectively. The number of panicles and seed setting rate of all ricevarieties were higher under the yellow clay soil, while the number of grains per panicle was higher in sandy loam soil. Soil type and its interaction with N application level significantly affected rice yields and yield components. The positive effects of N addition on yield were stronger in sandy loam soil than that in yellow clay soil. Nitrogen use efficiency was decreased with increasing N fertilizer application level, while the lower agronomic utilization of N was found in yellow clay soil for all rice varieties. Soil type had a significant effect on the agronomic utilization of N, while soil type and N level interacted to affect N apparent utilization.

Effects of drought stress at key growth stages on yield and grain quality of spring maize.

CHEN Ni-na, JI Rui-peng, JIA Qing-yu, FENG Rui, MI Na, ZHANG Shu-jie, ZHANG Yu-shu, YU Wen-ying

2021, 40(6):  1687-1694.  doi:10.13292/j.1000-4890.202106.033

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To explore the effects of different drought conditions at different growth stages on the yield and grain quality of spring maize, a comparative experiment of moderate and severe drought stress was conducted using cultivar Danyu 405 to analyze the effects of drought on maize yield and structural traits, grain water content, and quality composition at three key growth stages (jointing, tasseling, and milking stages) of spring maize. The results showed that drought significantly increased maize bald tip ratio, grain amino acid, and crude protein content by 85.3%, 10.6%, and 14.9% respectively. Drought significantly decreased 100kernel weight, theoretical yield, grain water content, and starch content by 14.2%, 30.5%, 29.7%, and 45.2% respectively. Drought had minor effects on ear length, ear thickness, and grain fat content. Grain starch content was most sensitive to drought during jointing stage. Ear thickness, bald tip ratio, grain water content, fat content, and amino acid content were most affected by drought during tasseling stage, while ear length, 100grain weight, yield, and grain crude protein content were most affected by drought during milking stage. With the increases of drought degree, the yield and grain quality of maize were affected more, with the effects on grain quality being more significant than that on yield. Our results lay a foundation for future high-yield and high-quality maize production and provide an important theoretical basis for understanding the mechanism underlying the responses of agricultural production to climate change.

Responses of leaf functional traits of Zanthoxylum planispinum var. dintanensis to premature senescence.

LI Hong, YU Yang-hua, LONG Jian, LI Juan

2021, 40(6):  1695-1704.  doi:10.13292/j.1000-4890.202106.028

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To understand the effects of recession on leaf functional traits of Zanthoxylum planispinum var. dintanensis and its recession response strategy, we investigated the leaf functional traits and soil physicochemical properties of normal and prematurely declining Z. planispinum var. dintanensis plantations. The results showed that specific leaf area, leaf phosphorus concentration, stable carbon isotope abundance, and leaf dry matter content were increased under premature senescence. The concentrations of organic carbon, nitrogen, potassium, and stable nitrogen isotopein leaves were decreased by premature senescence. There were significant differences in specific leaf area and stable carbon isotope abundance between normal and prematurely declining plantations. The correlations among leaf factors of prematurely declining plantation were weaker than that in normal plantation. The results of relative importance analysis and redundancy analysis revealed that soil moisture had the strongest effect on leaf functional traits such as specific leaf area and stable carbon isotope abundance in Z. planispinum var. dintanensis, followed by nitrogen, potassium, and calcium concentrations. Limited elements of normal and prematurely declining Z. planispinum var. dintanensis varied with phenological stage. The premature declining caused the reduction of nitrogen and phosphorus use efficiency of Z. planispinum var. dintanensis. Z.planispinum var. dintanensis would further reduce specific leaf area to improve its water use efficiency but maintain leaf dry matter content. These findings may provide a scientific basis for the maintenance of ecosystem stability and the improvement of yield and quality of Z. planispinum var. dintanensis.


The proportion of Frankliniella occidentalis and its population activity pattern with Orius similis on Capsicum annuum.

HU Chang-xiong, DUAN Pan, LI Yi-ru, LYU Bu-dian, ZHANG Xiao-ming, CHEN Guo-hua

2021, 40(6):  1705-1715.  doi:10.13292/j.1000-4890.202106.027

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To clarify the thrips species, population dynamics, and diurnal activities of dominant species Frankliniella occidentalis and natural enemy Orius similis on Capsicum annuum in different planting environments, fivepoint sampling and clapping method were used to investigate the thrips and O. similis on three varieties of C. annuum in greenhouse (Luosi chili) and open field (Luosi chili, Taikong chili, and Zhoupi chili) conditions. The differences in thrips species and the population dynamics were analyzed under both planting environments. The diurnal activities of F. occidentalis were monitored by blue sticky traps. The results showed that 10 thrips species were recorded in the open field and six thrips species were recorded in the greenhouse onC. annuum. F. occidentalis was the dominant thrips species on C. annuumunder both planting environments. The peak period of F. occidentalis population occurred from late June to mid-July. Population size reached  33.4 and 18.0 individuals per plant in the greenhouse and in the open field in 2019, and  32.2 and 17.9 individuals per plant in 2020, respectively. Population size of O. similis peaked in midJuly, being 10-20 d later than that of F. occidentalis. The abundance of F. occidentalis in main activity period was significantly higher than that in early and late periods (P<0.05) in both planting environments. However,O. similis had the highest population in main and late activity periods (P>0.05). F. occidentalis had the highest abundance in the greenhouse (P<0.05). O. similis had the highest abundance in the open field (P<0.05) in the main activity period of both insect species. F. occidentalis was not active in night, but showed more frequent activity in daytime. The main activity time period in daytime was mainly from 12:00 to 16:00 in the open field and from 10:00 to 18:00 in the greenhouse. The species composition of thrips and the population dynamics of F. occidentalis and predator O. similis were significantly affected by the planting environment of C. annuum. Population growth of F. occidentalis was promoted while the population of O. similis was suppressed in the greenhouse condition. Our results suggested that the planting area of C. annuum in open field can be appropriately increased around the greenhouse to increase the natural population of O. similis, in order to enhance the natural control ability of F. occidentalis.

The relationship between foliar K⁺ and Na⁺ concentrations and photosynthetic parameters of cotton seedlings under salt stress.

FU Yuan-yuan, JIANG Xiao-hui, SHEN Xiao-jun, SUN Wen-jun, ZHANG Jun-peng, Abubakar Sunusi Amin, GAO Yang

2021, 40(6):  1716-1722.  doi:10.13292/j.1000-4890.202106.013

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To understand the relationships between leaf K⁺, Na⁺ concentration and photosynthetic parameters (net photosynthetic rate, maximum carboxylation rate, maximum electron transport rate, mesophyll conductance) in cotton seedlings under salt stress, we measured the concentrations of K⁺ and Na⁺ and photosynthetic parameters in cotton seedling leaves under four levels of salt stress (50, 100, 150 and 200 mmol·L^-1) and control (0 mmol·L^-1). The results showed that there was a significantly positive correlation between foliar Na⁺ concentration and salt level, with a determination coefficient (R²) of 0.958. Foliar K⁺ concentration decreased with increasing salt levels, with R² of 0.871. Moreover, the Na⁺/K⁺ ratio was positively related to salt levels. There was an extremely significant negative correlation between K⁺ and Na⁺ concentration in the leaves. Foliar Na⁺ concentration was negatively correlated with net photosynthetic rate, mesophyll conductance, maximum carboxylation rate, dark respiration rate and maximum electric transport rate, with the correlation coefficients of -0.878, -0.861, -0.835, -0.837, and -0.813, respectively. Foliar K⁺ concentration was positively correlated with net photosynthetic rate, mesophyll conductance, maximum carboxylation rate, dark respiration rate and maximum electron transport rate, with the correlation coefficients of 0.718, 0.735, 0.645, 0.856 and 0.603,respectively. Under the salt stress of 150 mmol·L^-1, foliar K⁺ and Na⁺ concentrations were 11.54 and 3.32 mg·g^-1, which was the threshold of potassium and sodium ions affecting photosynthetic parameters. The results could provide an important reference for alleviating the ion damage on plants under salt stress.

Effects of dark septate endophyte on the growth, photosynthesis and mineral nutrition of Arundo donax under cadmium stress.

TENG Qiu-mei, ZHANG Zhong-feng, XU Guang-ping, ZHOU Long-wu, HUANG Yu-qing, CAO Yan-qiang

2021, 40(6):  1723-1733.  doi:10.13292/j.1000-4890.202106.007

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Cadmium (Cd) pollution in soil is a global problem. Mycorrhizalplant symbiosis can effectively repair Cd-contaminated soil. To understand the cadmium tolerance mechanism of Arundos donax inoculated with dark septate endophyte (DSE), a pot experiment was carried out to investigate the effects of DSE inoculation on the growth, photosynthesis and mineral nutrition of A. donax under Cd stress. The results showed that inoculation of DSE significantly improved the growth ofA. donax under Cd stress. Compared with CK, plant height, number of tillers, and aboveground biomass were increased by 12.97%-20.08%, 7.69%-45.45%, and 18.97%-28.35%, respectively. In addition, the apparent quantum rate and dark respiration rate were increased by 17.50%-46.77% and 7.81%-52.42%. The concentrations of total N, P, and K in roots were increased by 12.99%-40.60%, 18.07%-38.18%, and 23.00%-48.67%, respectively. The Cd concentrations in shoots and roots were significantly increased by 62.11%-91.87% and 8.13%-71.01%, respectively. The effects of DSE on A. donax under Cd stress varied with strains inoculated. The Cd translocation factor of LZ01LZ03 treatments were all greater than 1. The LZ01A. donax symbiont was the best combination under the experimental conditions. Cd stress and DSE had a significant interaction effect on the growth, photosynthesis and nutrient concentration of A. donax, with significant correlations among these three traits. The results indicated that inoculation with DSE can promote the growth and photosynthesis of A. donax, increase mineral nutrition, and enhance Cd absorption and transportation of A. donax under Cd stress. DSEA. donax symbiont is relatively resistant to Cd stress, with potential application prospect to Cd contaminated soil remediation.

Differences in physiological response and absorption capacity of nitrogen and phosphorus across different geographical populations of Spirodela polyrrhiza.

LIU Yan-hong, WU Lei, LIN Yi-bin, LIAO Lu, ZHAO Yi, YE Mao, ZENG Ren-sen, SUN Zhong-xiang

2021, 40(6):  1734-1744.  doi:10.13292/j.1000-4890.202106.010

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The discharge of wastewater from livestock farms with high-concentration nitrogen and phosphorus causes huge environmental pollution. Spirodela polyrrhiza has a strong ability to purify water pollutants. However, studies on the absorption and purification of nitrogen and phosphorus by different geographic populations of S. polyrrhiza are still lacking. In this study, 15 S. polyrrhiza populations were collected from different regions of southern China to examine the differences in physiological response and absorption capacity of nitrogen and phosphorus in waters of different geographic populations of S. polyrrhiza. The results showed that the growth phenotypes and physiological indicators (number of thallus, fresh weight, dry weight, root length, and protein content) of S. polyrrhiza significantly differed among the geographic populations (P<0.001). The physiological response and absorption ability of different geographic populations of S. polyrrhiza to nitrogen and phosphorus in water were quite different. Different geographic populations of S. polyrrhiza had different tolerance ability to high nitrogen concentration, with the nitrogen tolerance index ranging from 64.47% to 119.42%. Among them, Kunming and Leshan populations had the highest nitrogen absorption capacity (0.12 and 0.11 mg·pot^-1·d^-1, respectively). The tolerance of different geographic populations to high phosphorus was quite different, with the phosphorus tolerance index ranging from 81.22% to 157.73%. The phosphorus absorption ability of Dali and Wuhan populations was the highest (0.06 and 0.05 mg·pot^-1·d^-1, respectively). The number of thallus, biomass, and tolerance were significantly positively correlated to purifying ability of nitrogen and phosphorus across different geographic populations, indicating that those factors play an important role in purifying nitrogen and phosphorus. This study revealed the physiological response of different geographic populations of S. polyrrhiza to high concentrations of nitrogen and phosphorus and the differences in the ability to purify nitrogen and phosphorus in water at the growth phenotype and physiological level. Meanwhile, we obtained S. polyrrhiza populations with ideal purification effects on nitrogen and phosphorus pollution in waters. The results will provide a scientific basis for the rational use of S. polyrrhiza resources for water purification.

Methane flux and its influencing factors in the permafrost region of the Qilian Mountains.  

MAO Nan, LIU Gui-min, LI Li-sha, LI Xiao-ming, ZHANG Bo, XU Hai-yan, WU Xiao-dong

2021, 40(6):  1745-1752.  doi:10.13292/j.1000-4890.202106.005

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Global warming stimulates soil organic carbon decomposition in permafrost regions, which releases methane (CH₄) into the atmosphere. However, the relationship between CH₄emission flux and environmental factors in permafrost regions is unclear. In this study, we measured the CH₄ release rate of alpine wet meadow, alpine meadow, and alpine grassland in the permafrost region in the northern Qinghai-Tibet Plateau from June 2019 to January 2020, using static chamber-gas chromatography. We examined the relationships of CH₄ emission and soil physical and chemical properties. The results showed that the average monthly CH₄ release rate was0.080 mg·m^-2·h^-1 in alpine wet meadow, -1.132 mg·m^-2·h^-1 in alpine meadow, and -0.541 mg·m^-2·h^-1 in alpine grassland. The CH₄ emission flux showed obvious seasonal variations. The CH₄ emission fluxes in July and August were significantly higher than that in other months. There was a positive correlation between soil temperature and CH₄ emission flux. The rate of CH₄ production was positively correlated with soil moisture and total carbon content in the 0-15 cm layer of alpine wet meadow, and positively correlated with the contents of soil organic carbon, total carbon, and total nitrogen in the 15-30 cm layer. The rate of CH₄ production was negatively correlated with soil conductivity in the 15-30 cm layer of the alpine steppe. Our results indicate that meadows and grasslands are CH₄ sinks, and that vegetation types are the main factors affecting CH₄ release in permafrost regions. The CH₄ release rate is related to soil carbon and nitrogen contents, electrical conductivity, and soil temperature.

Distribution characteristics and pollution assessment of heavy metals in water and sediments of Aha Reservoir of Guizhou in different seasons.

ZHANG Wei, ZHANG Li-li

2021, 40(6):  1753-1765.  doi:10.13292/j.1000-4890.202106.006

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Clarifying the distribution of heavy metals in water and sediment across different seasons and evaluating their pollution are helpful to better understand the spatiotemporal dynamics of heavy metal pollution and its environmental effects in lakes and reservoirs. We analyzed the vertical distribution and the pollution evaluation of eight heavy metals in stratified water and sediments of different seasons in Aha Reservoir. The concentrations of eight heavy metals in the stratified water were in an order as Ni>As>Zn>Cu>Cr>Co>Pb>Cd. The increases in the concentrations of heavy metals in the hypoxic bottom water in summer and autumn were related to the release of heavy metals caused by the reduction of iron and manganese in the surface sediments. In the lake water mixing period of winter and spring, there was limited vertical change of heavy metals in the stratified water. The concentrations of eight heavy metals in the sediments were following an order of Zn>Ni>Cr>Co>Cu>As>Pb>Cd. The seasonal variation of the peak concentrations of heavy metals in the active sediment layer (above 12 cm) was related to the combined effects of the redox status of the sedimentwater interface and the corresponding seasonal variation of ironmanganese reduction and sulfate dissimilatory reduction. The concentration, pollution degree, and potential ecological risk of heavy metals (mainly Co, Ni, As and Cd) in the active layer of sediments in the Aha Reservoir were higher in summer and autumn than that in winter and spring. The influence of pore water diffusion into overlying water was very limited. The concentrations of heavy metals in the water in all the four seasons of Aha Reservoir did not exceed the standard limit specified in the “Surface Water Environmental Quality Standard” (GB 3838-2002) Class I standard and “Drinking Water Sanitary Standard” (GB 5749-2006), indicating that the water of Aha Reservoir had no heavy metals pollution.

 

Adsorption of arsenic on the sediments of Kuitun River in Xinjiang and the effects of organic acids on adsorption.

WANG Zhe, ZHAO Zhi-xi, LIU Yang qiu-fan, SUN Mei-ling

2021, 40(6):  1766-1774.  doi:10.13292/j.1000-4890.202106.008

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As a common organic matter in sediments, organic acids have important impacts on the migration behavior of arsenic in groundwater. We investigated the adsorption of arsenic on the main components of sediments in the Kuitun River Basin, Xinjiang, and examined the effects of organic acids on the adsorption of arsenic on goethite. Through XRD characterization and sediment element concentration measurement, we found that the main components of sediments in this area were calcium carbonate, quartz sand, aluminum phosphate, and goethite, with goethite contributing the most to arsenic adsorption. We further investigated the effects of common organic acids (glacial acetic acid, malonic acid, succinic acid, glutaric acid, and citric acid) on the adsorption of arsenic on goethite. The results showed that organic acids inhibited the adsorption of arsenic, with the inhibitory effect being related to the structure of the organic acids. As the increases of the number of carboxyl groups and the decreases of the length of the carbon chain, the inhibitory effect of organic acids on arsenic adsorption was more significant. Citric acid had the strongest effect on arsenic adsorption. The arsenic adsorption process conformed to the pseudo secondorder kinetics and Freundlich adsorption model. The results of infrared spectroscopy showed that citric acid and arsenic had competitive adsorption on the surface of goethite. The results of Zeta potential measurement showed that citric acid formed a negatively charged complex on the surface of goethite.

Heavy metal contamination in soils and enrichment capacity of typical tree species in shelterbelt along Hefei Loop Expressway.

ZHANG Qian-jin, CHEN Yong-sheng, LIU Hua, WANG Jia-nan

2021, 40(6):  1775-1782.  doi:10.13292/j.1000-4890.202106.024

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To understand the heavy metal pollution in soils of the shelterbelt along the Hefei Loop Expressway and the heavy metal accumulation ability of typical tree species (Populus canadensis, Koelreuteria paniculata, Ligustrum lucidum, Nerium oleander, and Salix babylonica) in the shelterbelt, we collected xylem samples from trunks and branches and soil samples from 60 sampling points in 12 sampling strips perpendicular to the shelterbelt. The concentrations of five kinds of heavy metals (Pb, Cd, Hg, Cr, and As) were measured by inductively coupled plasma emission spectrometry (ICPAES). The results showed that the concentrations of those five kinds of heavy metals in the soils all exceed the background values. The average concentration of Cd in the soil was 15.3 times of the background value. The concentrations of heavy metals in the soil tended to decrease with increasing distance from the expressway. Within the range of 35 m from the expressway, the comprehensive potential ecological risk of soil decreased significantly with increasing distance, but tended to be stable beyond 35 m from the expressway and was reduced to a slight level. The comprehensive enrichment ability of the five tree species to heavy metals was declining with an order ofNerium oleander, Ligustrum lucidum, Koelreuteria paniculata, Salix babylonica, and Populus canadensis.

 

Impacts of climate change on potential geographical distribution of golden pheasant (Chrysolophus pictus), an endemic species in China.

YE Wei-jia, YANG Nan, YANG Biao, LI Yun, ZHANG Jin-dong, CHEN Dong-mei, ZHOU Cai-quan, ZHONG Xue, ZHANG Jun

2021, 40(6):  1783-1792.  doi:10.13292/j.1000-4890.202106.023

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Range shifts of species driven by climate change are a major factor resulting in biodiversity loss and species extinction. Understanding the responses of geographical distribution to climate change has important implications for long-term biological conservation and management. The golden pheasant (Chrysolophus pictus) is a typical montane pheasant species endemic in China. In this study, we used the maximum-entropy model (MaxEnt) to analyze its current and future geographic distribution under different climate scenarios and predicted the effects of climate change on its distribution and habitat quality. The results showed that: (1) current range of golden pheasant widely distributes in central and western China, with a total area of 306191 km²; (2) its suitable distribution range will shrink under future climate scenarios, with a trend of shifting toward both northwest and higher elevation; (3) under the scenario of climate change, the habitat suitability will gradually decrease and the degree of habitat fragmentation will increase. Although its distribution range is relatively large and well connected at present, it will be threatened by range shrinking and habitat quality declining in the future. For the long-term protection of golden pheasant, we suggest investigate and verify its actual distribution, pay more attention to protect the core distribution range and climate refuges, establish corridors to enhance habitat connectivity, and adjust nature reserves network following the range shifts.

Current distribution of Asian Great Bustard (Otis tarda dybowskii) in China.

LI Chao, ZHOU Jing-ying, GONG Ming-hao, TIAN Xiu-hua, MENG De-rong, LIU Chun-guang, DANG Da-peng, LIU Gang

2021, 40(6):  1793-1801.  doi:10.13292/j.1000-4890.202106.009

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Asian Great Bustard (Otis tarda dybowskii) was once widely distributed in 19 provinces and municipalities in China. However, the habitat quality is getting worse and its distribution range is shrinking due to human disturbance. There is a lack of comprehensive knowledge about the distribution of the Asian Great Bustard, which is not conducive to the identification of key protected areas and the scientific formulation of protection countermeasures. By combining data from field surveys, bird watching records, published data and network reports of Asian Great Bustard in the past 20 years, the occurrence data were collected and the distributions of breeding sites, wintering sites and stopover sites were analyzed. The results showed Asian Great Bustard was currently distributed in 14 provinces and municipalities, with 70.91% of occurrence sites being located in Inner Mongolia, Henan and Shaanxi. Tumuji National Nature Reserve, Huihe National Nature Reserve and Gaogeshitai Hanwula National Nature Reserve in Inner Mongolia were the main breeding sites. However, 14.72% of breeding sites were outside the reserves. The wintering sites were mainly distributed in the Yellow River wetland at the junction of Shaanxi, Shanxi and Henan, the National Nature Reserve of the Yellow River Wetland for Birds in Xinxiang of Henan, and Cangzhou and Baiyangdian of Hebei. The middle and lower reaches of the Yellow River were the southernmost extension of wintering areas. Tumuji National Nature Reserve and Mingshui National Nature Reserve had relatively stable records of wintering populations, with partial migration behavior being observed. The stopover sites were relatively scattered, including Wuliangsuhai Nature Reserve, Gaogeshitai Hanwula National Nature Reserve, Huihe National Nature Reserve, Momoge National Nature Reserve, Shandian River National Wetland Park, Cangzhou in Hebei, Yeya Lake in Beijing, Qingdianwa Wetland in Tianjin. These important habitats were the key areas that should be protected with priority. Controlling of potential risks and raising public awareness would contribute to reducing human interference and improving the survival rates of Asian Great Bustard. Through integrating the distribution data of the past 20 years, we obtained a more comprehensive understanding of the distribution of the Asian Great Bustard, and discussed threats challenging Asian Great Bustard habitats. This study provides a scientific support for the implementation of protection countermeasures.

Moth diversity in Laodingshan National Forest Park.

SUO Hai-ying, TIE Jun, HOU Qin-wen, LIANG Jing-xuan, BAI Hai-yan

2021, 40(6):  1802-1810.  doi:10.13292/j.1000-4890.202106.014

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We analyzed the community structure and diversity of moths in four habitats, including coniferous forest, broad-leaved deciduous forest, mixed forest, and shrubbery forest (burnedarea), in the Laodingshan National Forest Park in Shanxi Province. A total of 5515 moth individuals, consisting of 13 families, 136 genera, and 172 species, were collected. Crambidae had the highest number of individuals, while Noctuidae had the highest number of species. Among the four habitats, the mixed forest had the highest moth species richness, with 139 species belonging to 13 families and 108 genera. The shrubbery forest had the lowest species richness, with 87 species belonging to 11 families and 77 genera. Noctuidae, Pyralidae, Crambidae, and Geometridae were the dominant families, while Crocidophora auratails, Endotricha portialis, and Dioryctria pryeri were the dominant species. The broadleaved deciduous forest had the highest Simpson index, Shannon index, and Pielou evenness index, while the coniferous forest had the lowest values in these indices. The mixed forest had the highest Margalef richness index, while the shrubbery forest had the lowest. The Simpson index and Shannon index of moths were positively correlated with Pielou evenness index and Margalef richness index. The Jaccard similarity coefficient and Euclidean distance clustering results showed that moth community in the shrubbery forest had a low similarity with those in the other three habitats. The speciesabundance curves in all four habitats fit the logarithmic distribution model, which is in line with the niche preemption hypothesis, indicating the instability of moth community structure and the low habitat quality in Laodingshan National Forest Park.

Fish community characteristics in the confluence area of Wanhe estuary in Anqing section of the Yangtze River.

YE Kun, YAN Yan, ZHU Xiao-yan, JIANG Min, LIN Dan-qing, LIU Kai

2021, 40(6):  1811-1819.  doi:10.13292/j.1000-4890.202106.026

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To clarify the structure and spatiotemporal variation of fish community in river confluence area, a yearround survey was conducted in the estuary of Wanhe River in Anqing. The results showed a total of 65 species (13651 fish) were recorded, belonging to 8 orders, 16 families, and 54 genera. The dominant species were Hemiculter bleekeri,Coilia nasus and Pseudobrama simoni. The values of community diversity indices were: Margalef index 6.92, Shannon index 2.56, Simpson index 0.88, and Pielou index 1.64. The results of clustering analysis showed fish communities from the eight sampling sites could be classified into north bank and south bank groups, with significant difference between the two groups (R=0.583, P=0.029). The results of variance analysis showed that there were no spatial and temporal differences in the characteristic values of fish community diversity. Spatially, the total number of caught individuals and the number and weight of small fish at sites 2 and 3 in the upstream of Wanhe confluence area were significantly higher than those at other sites. Temporally, fish catches and small fish catches in spring and summer were significantly higher than those in autumn and winter. In general, fish community diversity was high in the waters of the Wanhe confluence area, with lower diversity in the north bank than in the south bank. There was a clear characteristic of fish miniaturization.


Non-radiative effect dominates surface temperature changes on the Loess Plateau during the growing season under the background of ecological restoration.

SUN Shu-qing, YAN Jian-wu, LIANG Wei, ZHANG Wei-bin, WANG Feng-jiao, FU Shu-yi, GOU Fen

2021, 40(6):  1820-1829.  doi:10.13292/j.1000-4890.202106.029

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As one of the important factors affecting climate change by human activities, land use changes mainly affect climate system by changing the surface biogeophysical and biogeochemical processes. The impacts of land use change on climate system through biogeochemical processes have been extensively examined, but the understanding of biogeophysical processes is still insufficient, which is not conducive to accurate assessment of regional climate. This study focused on the Loess Plateau that has witnessed largescale and highintensity human activities. Based on the surface radiation energy data, the transfer of cropland from 2000 to 2015 was defined. The biogeophysical differences between cropland, forest, and grassland were quantified. Combined with the energy redistribution factor, the radiative and nonradiative effects of returning cropland to forest and grassland were estimated. Finally, we used the nonradiative forcing index (NRFI) to quantify the contribution of the nonradiative effect to the changes of land surface temperature. Our results showed that land use change caused 0.05 ℃ warming through the radiative effect and 0.21 ℃ cooling through the nonradiative effect on local surface temperature change. The nonradiative effect dominated responses of local temperature to land use change. During the study period, land surface temperature in the growing season dropped by 0.17 ℃ and the contribution of nonradiative effects was 69.7%. Surface temperature changes showed different sensitivity to energy redistribution factors, surface albedo, and soil heat flux. The energy redistribution factor dominated the land surface temperature change and reduced the surface temperature in the growing season by 0.21 ℃. Our results provide a theoretical basis for accurately assessing the influence of land use changes on regional climate and have implications for coping with or mitigating the impacts of climate change in the Loess Plateau.

Spatiotemporal variations and topographic differentiation of fractional vegetation cover in typical counties of Loess Plateau.

YANG Can, WEI Tian-xing, LI Yi-ran, LIU Xiao-hua, CHEN Yu-xuan

2021, 40(6):  1830-1838.  doi:10.13292/j.1000-4890.202106.020

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Exploring the spatiotemporal variations of vegetation on the Loess Plateau and its topographical differentiation effects is of great importance to understanding of the sustainable development modes of “Grain for Green” and the regional ecological evolution. Based on the Landsat image of the growing season from 1997 to 2018, combined with digital elevation model (DEM) data, we analyzed the spatiotemporal variations and topographic differentiation of fractional vegetation cover (FVC) before and after the implementation of the “Grain for Green” in Jixian County, Shanxi Province located in the Loess Plateau. The results showed that: (1) Ecological environment and overall FVC of Jixian County had been significantly improved from 1997 to 2018. With the implementation of the “Grain for Green”, the average annual FVC was increased from 47.87% in 1997 to 58.24% in 2018. However, FVC showed a downward trend in the county town and its surrounding areas. (2) The area with low and medium-low levels of FVC showed a decreasing trend, but the area with medium, mediumhigh, and high level FVC showed an increasing trend. The area with low level FVC (<20%) and medium-low level FVC (20%-40%) was mainly transferred out, while the area with medium level FVC (40%-60%) and medium-high level FVC (60%-80%) was mainly transferred in. FVC grade structure tended to be stable. (3) There were significant differences in vegetation restoration under different altitude, slope, and aspect conditions. The area of FVC located in the altitudes of 1000-1200 m, slopes of 15°-25°, and semi-sunny slopes was significantly increased. Our results can provide a scientific basis for evaluating the effects of regional ecological restoration and optimizing the measures of regional vegetation restoration.

Temporal-spatial variations of vegetation phenology and the influence of topography on phenology in Shanxi Province.

WANG Bei-bei, ZHOU Shu-qin, JING Yao-dong, SONG Xiao-jing, WANG Rong-yu

2021, 40(6):  1839-1848.  doi:10.13292/j.1000-4890.202106.030

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To clarify the vegetation phenology characteristics in Shanxi Province, we reconstructed the MODIS NDVI time series from 2000 to 2015 by adopting the Double Logistic fitting method, extracted vegetation phenology using the dynamic threshold method, and then analyzed temporalspatial variations of phenology and the effects of topography on phenological changes. The results showed that phenology in Shanxi Province changed significantly from 2000 to 2015. The start of the growing season (SOS) was advanced by about 0.7 d per year (R²=0.665, P<0.01). The end of the growing season (EOS) was delayed by about 1.5 days per year (R²=0.601, P<0.001). The length of the growing season (LOS) was extended by about 2.2 days per year (R²=0.772, P<0.001). The phenological change rate varied with different vegetation types. Grasslands showed the highest rate of SOS changes, followed by crops and then forestland. Forestland had the highest change rate of EOS, followed by crops and grassland. Forestland had the highest change rate of LOS, followed by grassland and then crops. There were substantial spatial variations in vegetation phenology. From low latitude to high latitude and from west to east, the SOS was delayed, EOS was advanced, and LOS was shortened. Vegetation phenology was significantly different across altitudes, slope aspects, and slope degrees. Vegetation phenology changed significantly with altitude below 1200 m. At higher altitude, SOS was significantly delayed, EOS significantly was advanced, and LOS was significantly shortened. Compared with shade slope, SOS at sunny slope was advanced by about 1 d, the EOS was delayed by about 0.8 d, and the LOS was extended by about 1.8 d. In areas with slope less than 16°, SOS was advanced, EOS wasdelayed, and LOS was extended with the increases of slope. Our results indicate that vegetation phenology varies greatly over a long time span and topography is a crucial factor influencing the spatial pattern of phenology.

Research advances in carbon use efficiency  at multiple scales.

DI Yang-ping, ZENG Hui, ZHANG Yang-jian, CHEN Ning, CONG Nan

2021, 40(6):  1849-1860.  doi:10.13292/j.1000-4890.202106.012

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Carbon use efficiency (CUE) is defined as the proportion of carbon (C) received from the environment that is used for growth. As one of the key indicators for the ability of biological carbon sequestration, it is widely implemented in the carbon cycle and process-based models. Research on CUE is carried out by various methods at multiple scales. However, the results of different methods vary greatly because of the scale-dependence of CUE, which makes the results difficult to integrate, becoming a vital factor restricting the research methods and application of CUE. In this review, we classified the common CUE acquisition methods into plot-scale, ecosystem-scale, landscape & regional scale and continental & global scale. We summarized the characteristics, advantages and limitations of each method. The progress of CUE application in research is reviewed at each scale. It is found that CUE is influenced by biotic and abiotic factors, which control CUE at different spatial and temporal scales. Moreover, the value of CUE varies with methods and scales applied in study. In order to deepen the understanding of CUE, future research should comprehensively consider the interactive effects of biological and environmental factors, improve the accuracy of data measurement, and promote model optimization by integrating multi-scale results.

Advances in biogeochemistry of mercury in the Yangtze River Basin.

ZHANG Qi, GUO Qing-jun, TAO Zheng-hua

2021, 40(6):  1861-1873.  doi:10.13292/j.1000-4890.202106.011

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Since the Industrial Revolution, global pollution of anthropogenic mercury has been worsening, with serious harms to health due to its carcinogenicity, teratogenicity and mutagenicity. Due to the highly concentrated industrial development and population density, a large amount of industrial and mining waste gas, waste water and domestic sewage from chemical industry, steel industry, oil refining, and other industries are discharged into the Yangtze River Basin. To reveal the current situation of mercury pollution in the Yangtze River Basin and its research advances, we summarized recent achievements on the biogeochemical behavior of mercury in the Yangtze River Basin, and discussed the concentration, form, distribution and pollution sources of mercury in different environmental media of atmosphere, water, sediment, aquatic organisms, soil and plants. Subsequently, the geochemical behavior and source analysis of nontraditional mercury isotopes is introduced, and the outlook of the future research is prospected. This review would provide basic data and references for the research and control of mercury pollution in the Yangtze River Basin.

Comprehensive ecological evaluation of small and medium-sized rivers in Beijing plain area.

GUI Yu-ru, BAI Jie, GAO Ting, CHANG Guo-liang, YE Zhi-han, ZHAO Yan-wei, ZENG Yong

2021, 40(6):  1874-1882.  doi:10.13292/j.1000-4890.202106.031

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In the management of small and medium-sized rivers in urban plain areas of China, the main task is to strengthen the flood control function of rivers. However, the study on the ecological status of small and medium-sized rivers is not sufficient, leading to the incomplete identification of ecological problems of small and medium-sized rivers. Consequently, it is difficult to provide decision support for the restoration of small and mediumsized rivers. Here, we constructed a multi-index comprehensive evaluation system, including five elements, 11 indices and four evaluation grades of river water discharge, water quality, aquatic organisms, river morphology, and riparian zone in 11 typical small and medium-sized rivers in Beijing plain area. The index weight was determined using analytic hierarchy process. The matterelement comprehensive evaluation model was established to comprehensively evaluate the ecological status of 11 rivers. Theresults showed that the ecological status of six rivers such as Yongding River Diversion Canal and Yunchaojian River is poor (grade IV), and that of five rivers such as Liangshui River and Nansha River is at moderate level (grade II). Results of the diagnostic analysis showed that the hydrological discharge, water quality, and aquatic organisms of the rivers are poor as a whole, with water shortage, single flow pattern, and poor water quality in different degrees. The overall situation of river morphology and riparian zone is moderate and the artificial degree of some river sections is high, which affects the ecological conditions of the rivers. According to the specific problems of each river identified by the evaluation results, we proposed some suggestions for ecological restoration of small and medium-sized rivers in Beijing plain area.

Eco-environmental quality assessment and cause analysis of Qilian Mountain National Park based on GEE.

ZHANG Hua, SONG Jin-yue, LI Ming, HAN Wu-hong

2021, 40(6):  1883-1894.  doi:10.13292/j.1000-4890.202106.034

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The ecoenvironment is highly related to human life. Remote sensing technique can objectively and quantitatively evaluate the spatial and temporal variations of ecoenvironment quality and thus provide a scientific basis for regional eco-environment management. Based on the Google Earth Engine (GEE) platform, we adopted Landsat TM/OLI remote sensing images as the basic data source to calculate the remote sensing ecological index (RSEI) that reflects the ecoenvironment quality. Using RSEI, we evaluated the eco-environmental quality of Qilian Mountain National Park during 1989-2019 and analyzed the reasons. The results showed that RSEI performed well in assessing the eco-environment quality of Qilian Mountain National Park. Greenness and wetness were the two indices with positive effects on the eco-environment quality, while dryness and heat indices had adverse effects. The analysis of spatial and temporal variations in Qilian Mountain National Park showed that the eco-environment quality presented a trend of “slow decline  rapid decline  increase” during 1989-2019. Changes in eco-environment quality were stable from 1989 to 1999, mainly mildly deteriorated from 1999 to 2009, and mainly mildly improved from 2009 to 2019. The analysis of the causes of eco-environment quality showed that the effects of all the four indices were significant. The strength of natural factors in influencing ecoenvironment quality were in order of greenness > dryness > wetness > heat in 1989; heat > greenness > wetness > dryness in 1999; dryness > heat > wetness > greenness in 2009; and greenness > wetness > dryness > heat in 2019. Animal husbandry was an important factor affecting the eco-environment quality of Qilian Mountains National Park. Our results suggested that the GEEbased platform could be used as a computing platform to evaluate the eco-environment quality of Qilian Mountain National Park. This platform extends the application of RSEI in the evaluation of eco-environment quality at large scale and long time series. The eco-environmental quality of Qilian Mountain National Park has developed in the right direction in recent years, although comprehensive management work needs further improvement.