Table of Content

10 March 2022, Volume 41 Issue 3

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Age calibration and growth stage division for naturally regenerated seedlings and saplings of Pinus koraiensis Sieb. et Zucc.

GE Xiao-wen, ZHU Jiao-jun, LU De-liang, ZHU Chun-yu, GAO Ping-zhen, YANG Xiao-yan

2022, 41(3):  417-426.  doi:10.13292/j.1000-4890.202202.016

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Accurately obtaining the age of regenerated individuals is the precondition for understanding regeneration status, quantifying regeneration age structure, and dividing regeneration stages, which is important for foresters to formulate reasonable forest management plan. However, two commonly used methods for age estimation of regenerated individuals have some deficiencies. Counting the number of rings (N_r) is destructive, while counting the number of whorls (N_w) lacks accuracy for many tree species including Korean pine (Pinus koraiensis). Further, the methods for growth stage division have not been uniformed. To accurately, efficiently, and non-destructively estimate the age of natural regeneration individuals of Korean pine, and divide growth stages of its regeneration layer reasonably, regeneration census including the root collar diameter and height of Korean pine (a total of 6831 individuals) was conducted in the primary mixed broadleaved-Korean pine forest in Lesser Khingan MountainsChangbai Mountains areas. Their ages were preliminarily estimated by traditional methods (counting the number of bud scars or whorls). Meanwhile, 153 regenerated individuals of Korean pine were destructively sampled by cutting base disk and counting N_r of the bottom section. Six calibration models between N_w and N_r were established. Method for growth stage division was proposed based on the biological characteristics of Korean pine and literature analysis (from 53 literatures). Results showed that directly using N_w as the age of regeneration individuals would underestimate age, while the calibrated N_w by the regression model (N_r=1.199N_w+2.962) was much closer to real age. According to the real age, height, and diameter at breast height (DBH) of regeneration individuals, the regeneration layer of Korean pine was divided into four stages, which were young seedlings (age ≤3 a), old seedlings (age >3 a and height <30 cm), small saplings (30 cm ≤ height <150 cm), and tall saplings (height≥150 cm and DBH <5 cm).

Carbon, nitrogen and phosphorus stoichiometric characteristics of plants, leaf litter and soils in Pinus tabuliformis and Ulmus pumila plantations

WANG Kai, QI Yue-tong, LIU Jian-hua, JIAO Xiang-li, LIU Huan-bin

2022, 41(3):  427-434.  doi:10.13292/j.1000-4890.202203.020

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In this study, we analyzed the concentrations of C, N and P in plant organs (leaf, branch and fine root), leaf litter and soils (0-10, 10-20, and 20-40 cm soil layer) in Pinus tabuliformis and Ulmus pumila plantations. Foliar N and P resorption efficiencies were calculated, and the nutrient cycling characteristics of the twoplantations were discussed. The results showed that concentrations of C, N and P in different organs of P.tabuliformis were 493-577, 6.34-17.22 and 0.66-1.91 g·kg^-1. The C and P concentrations of leaves and branches were higher than those of fine roots, while N concentrations followed the rank of leaf > branch > fine root. With the increased leaf and branch age of P. tabuliformis, N and P concentrations gradually decreased, while C∶N and C∶P gradually increased. The C, N and P concentrations in different organs of U. pumila were 404-472, 3.22-17.45 and 1.73-3.48 g·kg^-1. C concentrations were higher in leaves and branches than in fine roots, while N and P concentrations followed the rank of leaf > branch > fine root. C concentrations, C∶P and N∶P in leaves, branches and fine roots, and N concentrations in fine roots, and C∶N in leaves and branches of P.tabuliformis were higher than those of U. pumila, while P concentrations in leaves, branches and fine roots, N concentrations in leaves and C∶N in fine roots of P.tabuliformis were lower than those of U. pumila. Leaf litter C concentration, C∶N, C∶P, and N∶P were higher but N and P concentrations were lower in P. tabuliformis than in U. pumila.  P resorptionefficiency was higher in P. tabuliformisthan in U. pumila. Soil C, N and P concentrations were lower in P. tabuliformis plantation (2.47-5.52, 0.21-0.53 and 0.015-0.063 g·kg^-1) than in U. pumila plantation (4.82-12.22, 0.41-1.10 and 0.075-0.081 g·kg^-1). These results indicated that relatively more nutrients were allocated to leaves and branches and higher P resorption efficiency in P. tabuliformis plantation, resulting in less dependence on soil P. U. pumila allocated more nutrients to leaves and that returned to the soil through leaf litter, which were beneficial for nutrient cycling in plant-litter soil systems.

Species composition and community structure of a mixed broadleaf conifer forest dominated by Liriodendron chinense in the Jiugong Mountain, central China.

LYU Lin-yu, WANG Jian, WU Hao, WANG Shi-tong, ZHOU Tian-yang, XU Yao-zhan, WEI Xin-zeng, JIANG Ming-xi

2022, 41(3):  435-443.  doi:10.13292/j.1000-4890.202202.011

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To understand population structure of Liriodendron chinense and strengthen its in situ conservation, we established a 1 hm² plot in the Jiugongshan National Nature Reserve, central China. We recorded species composition of the plot, and analyzed sizeclass structure, spatial distribution pattern, conspecific association, and interspecific association of seven dominant species. A total of 7159 living individuals were recorded, belonging to 113 species, 76 genera, and 40 families. The dominant species were Daphniphyllum macropodum, Pinus taiwanensis, Eurya muricata, Quercus serrata, Litsea elongate, Neoshirakia japonica,and L. chinense. The sizeclass structure of all individuals showed a reversed “J” shape, indicating good natural regeneration in this community. The sizeclass structure of L. chinense was fluctuating and had great potential to develop into a stable population. L. chinense mainly occurred at the southeast corner of the plot, suggesting an obvious habitat preference. The spatial distribution pattern of L. chinense was aggregated at scales of 0-32 m and 34-35 m, and uniform at scale of 50 m. There were no correlations among sapling, middleaged, and adult individuals ofL. chinense at most scales, with the exception of positive or negative correlations at some scales. Overall, this mixed broadleaf-conifer forest was a transitional community type, with species composition and community structure being instable. Conservation and management should be strengthened to promote the regeneration and survival of natural L. chinense populations.

Woody species diversity in forest gaps and its driving forces in Maolan karst forest.

LI Yu-ling, ZHANG Guang-qi, YANG Ting-ting, QI Yu-jiao

2022, 41(3):  444-453.  doi:10.13292/j.1000-4890.202202.017

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Forest gaps in karst region, commonly formed after medianand small scale disturbance, are important places where woody species could regenerate and exist. Exploring the maintenance and driving forces of woody species diversity has a great significance. In this study, we investigated the gap characteristics and calculated the α diversity of woody species in the gaps in the evergreen and deciduous broadleaved mixed forest in Maolan National Nature, to clarify the relationship between gap characteristics and woody species diversity. We further analyzed the effects of habitat factors on woody species diversity in the forest gaps. The results showed that Lindera communisand Nandina domestica, which had positive regeneration responses to gaps, were the dominant species in gaps. The gaps with larger area and middle age had higher woody species diversity. The accumulating explanatory rate of forest gap characteristics, topographic factors and karst microhabitat was 66.6%. Among which, the explanatory rate of gap characteristics was 36% (gap size alone accounted for 28.2%), that of topographic factor was 23.3% and that of karst microhabitat was 1.9%. The results indicated that gap characteristics were the main driving force of woody species diversity. Therefore, forest gaps with different sizes could be artificially established to promote woody species regeneration in karst forests. Our findings revealed the mechanism of natural regeneration of woody species in degraded karst forests.

Root exudates characteristics and associated soil C and N transformation processes of Cupressus funebris plantation in hilly region of central Sichuan under N deposition.

BAI Zhi-yong, REN Ke-xin, CHEN Meng-yu, GOU Yong-xiang, XU hang, CHEN Lan-ying, XIAO Juan

2022, 41(3):  454-464.  doi:10.13292/j.1000-4890.202202.018

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Root exudates play an important role in regulating forest soil function and soil biogeochemical cycling. However, current understanding on input characteristics of forest root exudates and C and N processes mediated by rhizosphere soil under N deposition is still limited. This study took cypress (Cupressus funebris) plantation in the hilly area of central Sichuan as the research object. Different levels of N addition were used to simulate atmospheric N deposition. In 2020, root exudates were collected and analyzed in different seasons, and microbial biomass and C and N mineralization rate of rhizosphere/non-rhizosphere soils were analyzed, to reveal the seasonal variations of C input rate of root exudates, and the differences in soil C and N microbial process mediated by root exudates under different N addition treatments. The results showed that: (1) N addition significantly reduced C input rate and annual flux of root exudates in cypress plantation, with higher N addition having stronger inhibitory effect on C input of root exudates. (2) N addition significantly inhibited the rhizosphere effects of soil C and N mineralization and soil microbial C and N, with stronger inhibition effect of higher N treatment on soil C and N microbial processes. (3) The rhizosphere effect of root C and N process showed seasonal variation that gradually increased in spring and summer, and decreased in autumn and winter, peaking in summer. Our results demonstrated that N addition significantly reduced the rate and flux of root exudates of cypress forest, and significantly inhibited the microbial C and N transformation in rhizosphere soil. The intensity of inhibitory effect was related to N addition level, which confirmed the close relationship between forest root mexudatesmicrobial characteristics transformation processes of soil nutrients. Our results improved the understanding of forest rhizosphere processes under global change and provided scientific basis for adaptive management and ecological restoration of large-scale plantation forests in hilly area of central Sichuan.

Effects of precipitation change and nutrient addition on soil respiration in Hulunber meadow steppe.

TAO Dong-xue, LI Wen-jin, YANG Tian, KE Yu-guang, XU Chong, ZHAO Jin-ling, WU Hong-hui, YU Qiang

2022, 41(3):  465-472.  doi:10.13292/j.1000-4890.202202.031

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Soil respiration is an important part of terrestrial carbon cycling. Understanding its response to precipitation changes and nutrient addition can help to assess how global changes affect terrestrial carbon cycling. However, few studies have focused on the interactive effects of precipitation change and nutrient deposition on soil respiration. We conducted a field-manipulated experiment with increasing or decreasing precipitation and adding nutrient to simulate precipitation change and nutrient deposition on a meadow steppe in Hulunber, to explore the main and interactive effects of those two global change factors on soil respiration and the underlying mechanisms. The results showed that increasing precipitation did not affect soil respiration, while drought significantly reduced soil respiration. Nutrient addition had a limiting inhibitory effect on soil respiration, but its interaction with changing precipitation was not significant. Increasing precipitation significantly increased soil moisture, but did not affect soil temperature. Drought significantly reduced soil moisture and increased soil temperature. Nutrient addition significantly increased soluble inorganic carbon, inorganic nitrogen, and aboveground net primary productivity, and reduced soil moisture. Soil respiration was negatively correlated with soil temperature, but positively correlated with soil moisture, microbial biomass carbon and microbial biomass nitrogen. Soil moisture, soil temperature, microbial biomass carbon and microbial biomass nitrogen explained 56.3%, 26%, 16.6%, and 19.6% of the variation in soil respiration, respectively, indicating that soil moisture was the key factor regulating soil respiration. These findings may facilitate the understanding of soil respiration in meadow steppe under scenarios of global change.

Optimization of Trichoderma longibrachiatum biological fertilizer and its effects on growth, physiology and soil nutrients of Phoebe bournei seedlings

LEI Jiao-jiao, YU Cun, TIAN Li, YUAN Wei, ZHU Jing, YAO Ying

2022, 41(3):  473-478.  doi:10.13292/j.1000-4890.202202.012

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We used rapeseed oil cake and wheat bran as the main substrates to optimize the solid-state fermentation conditions of Trichoderma longibrachiatum fertilizer by measuring spore germination of T. longibrachiatum under different conditions. We treated 2-year-old Phoebe bournei seedlings with T. longibrachiatum fertilizer and with equal amounts of sterilized fertilizer fermentation substrate as control, and examined the growth, physiology and soil nutrients of P. bournei seedlings after 60 d conventional management in greenhouse. The results showed that after 4 d fermentation under the optimized conditions of 7∶3 ratio of rapeseed oil cake to wheat bran, pH 6, 25 ℃, solidliquid ratio of 1∶3, initial inoculum of 0.5×10⁸ cfu·g^-1 and full light, the spore concentration of T. longibrachiatum reached 1.38×10⁹ cfu·g^-1. The T. longibrachiatum fertilizer effectively enhanced growth indices of P. bournei seedlings, including seedling height, wet weight, dry weight, leaf area, root length, and root activity. Moreover, T. longibrachiatum fertilizer improved rhizosphere soil fertility of P. bournei seedlings, including total nitrogen, total phosphorus, available phosphorus, available potassium, hydrolyzed nitrogen, organic matter contents, and enzyme activities. T. longibrachiatum biological fertilizer can obviously promote the growth and physiological activity of P. bournei seedlings and rhizosphere soil fertility.

Effects of straw returning modes on maize seedling growth under different soil conditions.

WANG Shuai, ZHU Han-yu, YANG Zhan-hui, JIANG Zi-zhu, TAO Yu-zhao, LIU Chang-zhuang, Jan M FAHEEM, LI Ming

2022, 41(3):  479-486.  doi:10.13292/j.1000-4890.202202.036

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To explore the ecophysiological mechanism underlying the effects of straw returning on maize seedling growth, three types of soils (black soil, loess and acid soil) were selected, two methods of straw returning to the field (straw mulching and straw mixing) and two stone treatments (stone covering and stone mixing) in black soil were set up. The morphological changes of aboveground and belowground parts and the physiological indices of stress resistance under different treatments were compared. The results showed that straw returning significantly increased plant height, leaf area, dry matter weight, chlorophyll fluorescence parameters, root length, root surface area, root tip number, and active absorption area of roots at seedling stage. The straw mixing treatment performed better than straw mulching treatment. Straw returning decreased superoxide dismutase and catalase activities and malondialdehyde content, with mulching treatment performing better than mixing treatment. Although the fertility of loess was different from that of black soil and acid soil, the effects of straw returning were the same. Both stone treatments inhibited root growth. Straw returning treatments (either mulching or mixing) performed better than stone treatments. Therefore, straw returning promoted root growth and nutrient absorption mainly by changing soil biochemical properties, and thus enhanced the growth of aboveground parts.

Degradation characteristics and adaptability of corn stover by composite microbial system at low temperature.

ZHANG Bi-zhou, BORJIGIN Qingge-er, GAO Ju-lin, YU Xiao-fang, HU Shu-ping, ZHANG Xin, WANG Fu-gui, HAN Sheng-cai

2022, 41(3):  487-494.  doi:10.13292/j.1000-4890.202202.030

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The slow decomposition of stover returned to field in winter leads to low emergence rate of seedlings and aggravation of diseases and insect pests in northern China. Here, we explored the degradation characteristics of corn stover by exogenous rot promoting microorganisms under low temperature, with the aim to provide scientific support for field application of low-temperature corn stover degradation compound bacteria. Achromobacter deleyi (A3), Pseudomonas plecoglossicida(A4),Aspergillus terreus(A), andPhanerochaete chrysosporium(P) were used to build composite microbial system GF-Z. The results showed that degradation rate of corn stover by the composite microbial system GF-Z under 15 ℃ cultivated for 30 d was 38.79%. The activities of filter paper enzyme (FPA), xylanase and laccase were 14.59 U·mL^-1, 5.86 U·mL^-1 and 54.49 U·mL^-1, respectively. Under the conditions of salt concentration 0.02%-2.5% and initial pH 4.0-9.0, the activities of FPA, xylanase and laccase of GF-Z were maintained above 81%, and the degradation rate of corn stover was 36.2%-37.5%. When temperature ranged from 13 to 25 ℃, the activities of FPA, xylanase and laccase of GF-Z were maintained above 85%, and the degradation rate of corn stover reached 38.79%.

Effects of irrigation water purification coupling with paddy soil Cd resistance measures on the reduction of Cd accumulation in rice.

ZENG Zhao-xia, LIU Xiao-li, ZENG Fu-ping, ZHANG Hao, ZOU Zhi-gang

2022, 41(3):  495-502.  doi:10.13292/j.1000-4890.202202.034

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Reducing heavy metal inputs is one of the key measures for the safety of agricultural production. We investigated heavy metal pollution sources and excessive irrigation water status at watershed scale in a typical Cd polluted Huanjiang section of Great Huanjiang River Basin. We purified irrigation water by the grit chamber and 3-level constructed wetland system, and simultaneously coupled with adding slaked lime and biochar materials into paddy soil as Cd activity control measures. The main objective of this study was to understand the combined reduction effects of Cd contaminated irrigation water purification with soil Cd activity control on Cd accumulation in rice. Results showed that Cd concentration in irrigation water displayed obvious fluctuation during April to November 2020, with the maximum and minimum inflow concentration of 8.38  and 2.15 μg·L^-1 into the constructed wetland system, respectively. The mean Cd concentration declined from 5.88±3.27 to 0.69±0.35 μg·L^-1 after purification through the constructed wetland system, while no reduction effect was observed in the grit chamber process. The best Cd removal result was observed in the firstclass wetland, the total Cd removal rate of the wetland system reached 88.3%, and the effluent water quality satisfied the irrigation water standard. The addition of hydrated lime, biochar and lime plus biochar reduced Cd accumulation in rice grain by 9.2%, 1.5% and 20.0%, respectively, compared to the single irrigation water purification treatment. Single lime treatment with the same addition amount performed better than biochar treatment. The reduction rate of Cd in rice grain under the treatment of irrigation water purification coupled with passivation materials reached 45.8% compared with the local traditional rice production mode. Therefore, irrigation water purification by constructed wetland system, combined with soil Cd activity control, could effectively reduce Cd input into the paddy soil and Cd accumulation in rice, and thus effectively improved rice production security coefficient. The results can provide scientific support and practical reference for the safety production of Cd-contaminated rice fields in southern China.

Toxicological responses of metamorphosed juvenile frog to pesticide stress at the period of tadpoles.

YANG Shu-yu, ZHANG Rui, ZHAO Wen-ge, YU Dong

2022, 41(3):  503-511.  doi:10.13292/j.1000-4890.202202.032

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We investigated the changes of the expression of antioxidant enzymes and detoxification enzymes and cytochrome P450 3A (CYP3A) in liver tissue of Rana dybowskii after exposure to atrazine and chlorpyrifos in tadpoles stage. Experiments were carried out under different concentrations of atrazine and chlorpyrifos, either alone or combined. The activities of catalase (CAT), superoxide dismutase (SOD), acetylcholinesterase (AChE), carboxylesterase (CbE), and relative expression of CYP3A mRNA were measured in the liver tissue of Rana dybowskii at the period of metamorphosis completion. The results showed that the activities of antioxidant enzymes (SOD and CAT) and detoxification enzymes (AchE and CbE) and relative expression of CYP3A mRNA in the liver tissue were significantly decreased with increasing pesticide concentrations. These results suggested that exposure of to single and combined pesticides at tadpole stage could make Rana dybowskii toxic at the period of metamorphosis completion, and significantly changed the activities of antioxidant enzymes and detoxification enzymes, and relative expression of CYP3A mRNA. The expression of CYP3A mRNA showed similar responses with the levels of antioxidant enzymes and detoxification enzymes.

Optimal scale analysis of the effects of farmland landscape heterogeneity on soil arthropod diversity.

BIAN Zhen-xing, YANG Yu-jing, GUO Xiao-yu, GUAN Ming-hao, YU Miao

2022, 41(3):  512-519.  doi:10.13292/j.1000-4890.202202.033

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The homogenization and fragmentation of agricultural landscape is one of the important reasons for the losses of agricultural biodiversity in modern times. In order to clarify the impacts of landscape heterogeneity on arthropod diversity, we analyzed the correlation between arthropod diversity and landscape heterogeneity at different scales in Changtu County, a typical agricultural area in the Lower Liaohe Plain. The results showed that 1000 m was the optimal scale to study the effects of landscape index on arthropod diversity in farmlands. Simpson diversity index of arthropods was significantly correlated with landscape’s Shannon diversity index (P<0.01), landscape’s CONTAG index, and Shannon evenness index (P<0.05). The diversity of arthropods was higher and the distribution was uniform when the agricultural landscape was heterogeneous, the patch types were complex and there were dominant patches. Shannon diversity index of arthropods was extremely significantly correlated with landscape’s Shannon diversity index (P<0.01). Margalef richness index of arthropods was significantly correlated with landscape’s Shannon diversity index (P<0.05). The number of ground-dwelling arthropod species in farmlands was higher and the community was more complex when the degree of landscape fragmentation was low, the number of patch types was small, and the complexity and variability of patch types were low.

Inhibitory effects of rhamnolipid crude extract on plant pathogenic fungi.

CHEN Yao, SHI Rong-jiu, ZHENG Liang-can, HAN Si-qin, WANG Yan-hong, ZHANG Ying

2022, 41(3):  520-527.  doi:10.13292/j.1000-4890.202202.035

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Effects of biosurfactants on plant fungal diseases have been received much attention worldwide. Rhamnolipid is an anionic biosurfactant synthesized by Pseudomonas aeruginosa, with great potential as an inhibitor of plant pathogenic fungi. However, the comprehensive evaluation on its antifungal spectrum and antifungal activity is not fully explored. In this study, 29 common plant’s pathogenic fungi were collected. The sensitivity of pathogenic fungi at different taxonomic levels to the inhibition of rhamnolipid was evaluated based on Ainsworth fungal systemic taxonomy. The results showed that the inhibition effect of rhamnolipid on Oomycotawas the best. When the concentration of crude extraction of rhamnolipid was 0.3 g·L^-1, the inhibition rate for Pythium attrantheridium, Pythium irregular, and Pythium acanthicum mycelium was 80%, followed by Deuteromycota. When the concentration was 0.5g·L^-1, the inhibition rate for Verticillium dahliaeand Rhizoctonia solani reached higher than 80%. However, the effect of rhamnolipid was poor, even not effective to inhibit Ascomycetes andZygomycetes of pathogenic fungi. Furthermore, the observation of the morphological structure of fungal hyphae showed that rhamnolipid destroyed the cell wall of fungal mycelium and changed the permeability of cell membrane, and thus inhibited the growth of mycelium. As far as our knowledge, this study is the first one to show that rhamnolipid could inhibit the growth of Fusarium proliferatumand Fusarium redolens. The inhibition rate of rhamnolipid against hyphae was 63% and 74%, respectively, when the crude extraction of rhamnolipid was 1.0 g·L^-1. This study comprehensively evaluated the antifungal spectrum and ability of rhamnolipid from taxonomic status of pathogenic fungi, which provided technical support for the development of biological control technology of plant’s pathogenic fungi.

Particulate matter retention amount by leaves of common tree species in Urumqi People’s Park.

Kailibinuer NUERMAIMAITI, müt HALIK, Nasiman NASIERDING, Aliya BAIDOURELA, Mayinuer REHEMAN

2022, 41(3):  528-535.  doi:10.13292/j.1000-4890.202203.030

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The objective of this study was to explore the vertical and horizontal variations of leaf particulate matter retention amount of park greening trees. Three broad-leaved tree species, Quercus robur,Rhus typhina and Fraxinus rhynchophylla, widely distributed in Urumqi People’s Park and with different canopy structures, were selected. Leaves were collected at 12 positions of different canopy heights (2, 4, 6 m) and directions (east, south, west, north) at leaf maturity stage in July. The difference of retention capacity per unit leaf area of different tree species to atmospheric particulate matter (PM_0.2-3, PM_3-10, PM_>10 and PM_total) at different positions of canopy was analyzed. The results showed that: (1) There was a significant difference in retention amount of different sized particulate matters on leaves among different tree species (P<0.05). The retention capacity of PM_3-10 per unit leaf area of different tree species across different positions was ranked as: Q. robur>R. typhina>F. rhynchophylla, while the retention capacity for PM_0.2-3, PM_>10 and PM_total was ordered as: Q. robur>F. rhynchophylla>R. typhina. Q. robur had the highest and stable retention capacity for particulates of different sizes, R. typhina had better retention capacity for medium-sized particulates, and F. rhynchophylla had better retention capacity for particulates except PM_3-10. (2) There was a certain difference in retention capacity of various particulates at different canopy heights of the three species (P<0.05), and such difference of different sized particulates followed a same pattern, i.e.: 2 m > 4 m > 6 m. Canopy height had a significant effect on leaf retention amount of PM_3-10, PM_>10 and PM_total (P<0.05), with an extremely significant effect on PM_3-10 (P<0.01). There was no significant difference in leaf retention capacity to different sized particulates at different directions of canopy (P>0.05). There was no significant interaction of canopy height and direction (P>0.05). (3) PM_>10 was the main particulate on leaf surface of examined tree species, PM_3-10 was the second, and PM_0.2-3 was the least. PM_0.2-3 was mainly concentrated at 4 m height in the northwest direction, while PM_3-10 was concentrated in the northwest direction, without obvious pattern in canopy height. PM_>10 was more distributed at 2 m height in the bottom of canopy, but there was no obvious pattern in the direction. Our results can provide a scientific basis for reasonable selection of greening tree species for the urban park greening management department.

Variation of extreme precipitation and its influencing factors in monsoon marginal region: A case study of Shiyang River Basin.

HUANG Ju-mei, ZHOU Jun-ju, DOU Jiao, MA Dong-feng, ZHAO Xi, WEI Wei, HU Ke

2022, 41(3):  536-545.  doi:10.13292/j.1000-4890.202202.021

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Global warming leads to an overall increase in atmospheric humidity and precipitation intensity, which aggravates the occurrence of extreme precipitation events. Scientific understanding of regional variations of extreme precipitation and its impacts is of great practical significance to the management and rational utilization of water resources, ecological protection and governance, and sustainable development of agriculture. Based on the daily precipitation data of four meteorological stations in the Shiyang River Basin from 1960 to 2018, we used unitary linear regression analysis and correlation analysis to analyze the variations and influencing factors of extreme precipitation in the Shiyang River Basin. The results showed that the values of extreme precipitation indices of the whole basin were on the rise except the consecutive dry days and wet days. Among them, the annual total precipitation, very wet days, and extremely wet days had a significant upward trend. Spatially, except consecutive wet days, the change tendency rate of other extreme precipitation indices showed an obvious altitude gradient effect, that is, the higher the altitude, the greater the growth rate. The correlation of extreme precipitation with minimum temperature was stronger than that with maximum temperature, indicating that extreme precipitation is more sensitive to minimum temperature than maximum temperature. Under the background of global warming, the changes of extreme precipitation in Shiyang River Basin were the results of the interaction of different atmospheric circulation systems, such as Arctic Polar Vortex, Western Pacific Subtropical High, East Asian Trough, and Tibet Plateau circulation. The rise of regional temperature exacerbated the occurrence of extreme precipitation events.

Long-term changes of water quality and the driving factors of Wuliangsuhai Lake.

ZHU Peng-hang, YU Rui-hong, GE Zheng, SUN He-yang, CAO Zheng-xu

2022, 41(3):  546-553. 

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In order to understand the long-term variations of water quality in Wuliangsuhai Lake, we used the power function summation type universal index (EI) for eutrophication evaluation based on water quality data of Wuliangsuhai Lake during 1999-2019, and used the Mann-Kendal and STARS mutation test to examine the mutation of water quality in Wuliangsuhai Lake. The results showed that the eutrophic level in Wuliangsuhai Lake showed a fluctuating decreasing trend. Water quality mutation at inlet, center and outlet areas of the lake occurred in 2012, 2014 and 2016 respectively, with a postponed occurrence of mutation time one after another. Among the three areas, the inlet was generally at medium and heavy eutrophic level, the nutrient concentrations decreased significantly before and after the mutation of water quality, EI decreased by 20.56%, but it was still in algae-type turbid water state. External inputs and autochthonous enrichment were the main reasons for the serious pollution of the inlet area. The center and outlet areas of the lake were at a light eutrophic level, with an overall decreasing trend, fluctuating between grass-algae and algaegrass coexistence. The center area of the lake was mainly influenced by the release of autochthonous nutrients from the sediments. In the outlet area, the trend was mainly affected by the decrease of plant quantity and the digestion and metabolism of fish. The sampling rates with nitrogen/phosphorus ratios greater than 16 in three areas of Wuliangsuhai Lake were 44.2%, 65.7%, and 72.8% respectively, indicating that Wuliangsuhai Lake was phosphorus-limited. Our results provide scientific basis for the management and water quality mutation warning in Wuliangsuhai Lake, and a reference for assessing the changes of water quality in shallow eutrophic lakes in arid areas.

Dynamics of gross primary productivity in Gansu Province based on VPM model.

LI Liang, LIU Min-xia, SONG Jia-ying, ZHANG Guo-juan, WANG Si-yuan

2022, 41(3):  554-561.  doi:10.13292/j.1000-4890.202202.028

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Based on the vegetation photosynthesis model (VPM), we estimated gross primary productivity (GPP) in Gansu Province during 2005-2017, and explored the temporal and spatial variations, variation trend and influencing factors of GPP in different vegetation zones. The results showed that: (1) GPP increased significantly during 2005-2017, with a rate of 6.53 g C·m^-2·a^-1. There were significant differences of GPP among different vegetation zones, with the highest GPP of 1056.03 g C·m^-2·a^-1 in subtropical evergreen broad-leaved forest and the lowest GPP of 164.4 g C·m^-2·a^-1 in temperate desert. (2) In terms of spatial distribution, GPP showed adecreasing trend from southeast to northwest. Qilian Mountains, Qingyang, and southern Gansu were areas with high value. The areas with GPP greater than 500 g C·m^-2·a^-1 accounted for 40.15% of the total area, while the areas with sustained growth of GPP accounted for 83.65%. The areas with poor GPP stability accounted for 30.41%, which mainly distributed in Jiuquan, Wuwei, Lanzhou and Baiyin. The proportion of GPP high aggregation type increased from 29.53% to 30.14%. The high value of GPP increased and became more concentrated in Longnan and Qingyang. (3) The area of woodland increased significantly in Qilian Mountains, Baiyin and Longnan. The area of grassland increased significantly in Jiuquan and Zhangye, while bare land area decreased evidently. The increase of grassland and woodland areas and the reduction of bare land were the main reasons for the increases of GPP in Gansu. (4) The GPP in central Gansu increased with increasing air temperature and precipitation. Rainfall had a positive effect on the increases of GPP in northern Gansu, while temperature had a negative effect on GPP. The change of GPP in southern Gansu showed a contrary pattern.

Estimation of regional peanut LAI based on terrestrial hyperspectrum and GF-1 satellite.

LI Jun-ling, LI Meng-xia, CHEN Zheng

2022, 41(3):  562-568.  doi:10.13292/j.1000-4890.202202.029

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Examining crop leaf area index (LAI) and its dynamic change is of great significance for crop growth monitoring and yield estimation. The inversion of crop growth parameters based on terrestrial hyperspectral data is a hotspot in agricultural remote sensing research. However, most previous studies used terrestrial hyperspectral data to establish the estimation model of crop LAI, which is difficult for regional application. In order to apply the terrestrial hyperspectral research results to the satellite scale and realize the inversion of regional peanut LAI, thereby to monitor the largearea peanut growth, we constructed a variety of wideband spectral indices based on the terrestrial observation spectrum data, and built a remote sensing peanut LAI estimation model based on the hyperspectral index. The hyperspectral index was constructed with the GF-1 satellite sensor spectral response function and the terrestrial hyperspectral data on the basis of plot test and field test of the observation station. By comparing the determination coefficient and verification accuracy of different estimation models, we found that the model based on the RVI index (LAI=0.481RVI^0.830) was the best one for LAI estimation. Based on the optimal model, the peanut LAI distribution was obtained by performing the peanut LAI remote sensing mapping, and the remote sensing inversion LAI accuracy was verified by field data. The results showed that the use of wideband index and GF-1 would be suitable for peanut LAI estimation, which has great significance for monitoring large-area peanut growth.

Analysis on habitat protection effectiveness of nature reserves based on landscape fragmentation in Southwest China.

LENG Xian, ZENG Yuan, ZHOU Jian, YANG Fei-ling, YE Jin, ZHANG Ji, WU Rui-dong

2022, 41(3):  569-579.  doi:10.13292/j.1000-4890.202202.019

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Humancaused landscape fragmentation is a primary driving force for global biodiversity loss, and a major threat to nature reserves (NRs). However, studies on the effectiveness of NRs in preventing landscape fragmentation are still limited. Based on four phases of land cover data in 1990, 2000, 2010, and 2015 in Southwest China, we constructed a landscape index to quantitatively analyze the effectiveness of 102 NRs in the region in preventing landscape fragmentation. We assessed the impacts of different administrative levels, establishing years and categories of NRs on conservation effectiveness. Finally, we established a human disturbance index in each NR to reveal the impacts of human disturbances on landscape fragmentation. The results showed that: (1) During the past 25 years, the number of NRs with decreased fragmentation was greater than that with increased fragmentation, indicating that NRs were effective in habitat conservation. However, the overall increasing trend of average fragmentation showed that some NRs had lower ability on protecting habitat intactness; (2) There were no significant differences in the conservation effectiveness of four categories of NRs. The administrative levels and their establishing years influenced the effectiveness of these NRs. Before 2000, the effectiveness of provincial NRs and NRs established in 1981-1990 was better than that of national NRs and NRs established in 1958-1980 (P<0.01), respectively. After 2000, the effectiveness between NRs at different levels and established in different years was similar (P>0.05); (3) The relationship between human disturbance index and landscape fragmentation varied in different periods. From 1990 to 2000, there was no significant correlation between them, and NRs demonstrated a strong effect of offsetting human disturbances. From 2000 to 2010, there was a significant correlation between them, and human disturbances were probably the dominant factor increasing landscape fragmentation. From 2010 to 2015, the correlation was no longer significant. It is noteworthy that the influence of natural disturbances should be considered for those NRs with decreased human disturbance index but increased landscape fragmentation.

Changes of spatial synergies or trade-offs of ecosystem services in Heihe River Basin.

HU Xiu-fang, ZHAO Jun, WANG Bei, GAO Chao

2022, 41(3):  580-588.  doi:10.13292/j.1000-4890.202201.001

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Heihe River Basin is an area with important ecofunction. Changes of ecosystem services in this area greatly impact local socioeconomic development and ecological security. The society-ecology-environment problems have been highly concerned. Therefore, it is of great significance to examine the changes of ecosystem services and the synergies and trade-offs between them. In this study, ecosystem services and related synergies/trade-offs from 1990 to 2015 were quantitatively analyzed by the bivariate pixel by pixel correlation analysis based on time series. The results showed that there were synergies between ecosystem services at the whole region in the Heihe River Basin. There were 19 pairs of ecosystem services with synergy > trade-off: relationship between water yield, water conservation, soil conservation, N retention, P retention and carbon storage; 6 pairs with synergy = trade-off: food supply-water yield/water conservation/soil conservation, biodiversity maintenancewater yield/water conservation/P retention; 2 pairs with synergy < trade-off: biodiversity maintenance soil conservation/N retention. There were obvious regional variations in the synergy/trade-off relationship of ecosystem services. There was no synergy/trade-off relationship in 30% of the region. The spatial distribution of synergy/trade-off relationship varied greatly from north to south. The synergy/trade-off relationship was obvious in the south, being a long strip from southeast to northwest. By contrast, the synergy/trade-off relationship was not obvious in the north, the synergy/tradeoff areas were scattered in many points, flocculent and staggered, with low agglomeration.


Evaluation of slope re-vegetation effect: Research progress and prospect.

XU Hui, LYU Qing, YANG Yu-he, MA Jian, TANG Xue-feng, XU Li-gen

2022, 41(3):  589-596.  doi:10.13292/j.1000-4890.202202.009

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Vegetation reconstruction on the excavated slope is an important step of ecological restoration. Therefore, evaluating the effects of slope vegetation reconstruction is of great significance. Here, we reviewed the research progress in the evaluation of slope re-vegetation effect, specifically in the construction of evaluation index system, the acquisition of evaluation index data, and the relevant standard specifications. The evaluation indices of protection performance, soil condition, vegetation condition, landscape effect and comprehensive benefit were reviewed. The methods of slope vegetation survey could be divided into three development stages: manual field survey, satellite remote sensing interpretation, and aerial survey by unmanned aerial vehicle (UAV). Problems in the evaluation of slope vegetation reconstruction effect, including lack of quantitative evaluation data, lack of information technology support, lack of continuous tracking and monitoring, lack of mutual feedback of engineering practice, were summarized. The directions of data quantification, technology modernization, long-term monitoring, and engineering application are proposed as the main topics in the future research.

Research progress of straw mulching technology and its application in farmland.

MA Jian-tao, CHAI Shou-xi, CHENG Hong-bo, CHANG Lei

2022, 41(3):  597-602.  doi:10.13292/j.1000-4890.202202.023

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Straw mulching is one of the cultivation measures for drought resistance, moisture conservation, and efficient water use in dryland agriculture. It is a technology for green agriculture to increase production and meet the needs of sustainable development. Straw mulching is an important way of recycling straw resources. It alleviates the haze pollution caused by the illegal incineration of straw and weakens the residual film pollution caused by long-term mulching. However, the effects of straw mulching depend on climatic conditions and crop types. In this review, we expound the effective mechanisms of straw mulching to promote crop yield and water-efficient use from the perspectives of water storage, temperature regulation, moisture retention, and evapotranspiration change of farmlands. Meanwhile, we propose that researches on straw mulching pattern, prevention and control of crop diseases and insect pests, agricultural machinery and agronomy matching, and greenhouse gas emission reduction in straw mulching cultivation should be strengthened, so as to improve relevant techniques and methods, and provide a reference for the improvement and promotion of straw mulching technology.

Analysis of vegetation coverage and diversity of dump based on hyperspectral remote sensing.

XU Mu-sang, LEI Shao-gang, YANG Xing-chen, GONG Chuan-gang, ZHAO Yi-bo, LU Xiao-guang

2022, 41(3):  603-609.  doi:10.13292/j.1000-4890.202202.008

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As a typical disturbed patch in the mining area, dump is a key object of ecological restoration in the mining area. Studying species diversity of artificially reconstructed dump ecosystem and analyzing vegetation coverage and configuration under different slopes can provide reference for plant species selection and configuration scheme for the vegetation reconstruction project in dumping site. With the north slope of Baorixile coal mine dump as the research area, we used UAV hyperspectral remote sensing technology to obtain images. Combined field measurements, we established a typical vegetation spectrum library. We used the spectral angle method to realize the mapping of vegetation type distribution and diversity analysis. The results showed that: (1) The plant community had succeeded from one with species from single-family to that with 15 families, 28 genera, and 32 species. Perennial herbs replaced annual or biennial herbaceous pioneer species. (2) Asteraceae, Leguminosae, Rosaceae, and Gramineae played a major role in vegetation reconstruction, which is consistent with the main plant families of the surrounding natural grassland, showing a forward succession. (3) Vegetation coverage of the study area was mainly at medium and good levels. Excellent vegetation coverage types had a significant distribution advantage on slope III (5°-15°), with a correction coefficient (k) of terrain area difference of 1.11. (4) The slope range of 14°-15° was suitable for plant growth. When the configuration was Cleistogenes squarrosa (29%) +Chenopodium glaucum (28%) + Serratula polycephala (20%) +Astragalus adsurgens (15%) +Sonchus oleraceus (6%), vegetation coverage was the best, which could achieve a better ecological restoration effect. This study provides scientific basis for the terrain shaping, plant species selection, and configuration of mining dumps.

Evaluation of salt tolerance of diploid potato and screening of salt tolerance indices.

ZHAO Ming-hui, BAI Ya-mei, MENG Ling-bo, SUN Ting-ting, WANG De-quan, JING Chong-yang, LYU Wen-he

2022, 41(3):  610-617.  doi:10.13292/j.1000-4890.202202.027

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In order to quickly evaluate the salt tolerance of diploid potato germplasm resources, five morphological indices and eight physiological and biochemical indices of plantlets in vitro of 17 diploid potato clones were measured using principal component analysis, subordinate function analysis, clustering analysis, and stepwise regression. The five morphological indices were simplified into one independent comprehensive index, while the eight physiological and biochemical indices were simplified into four independent comprehensive indices using principal component analysis. Those seventeen clones were classified into three clusters with different salt tolerance using cluster analysis, with A038, A002, and A024 being classified into the salt tolerance cluster. A regression equation of salt tolerance evaluation was established by morphological index. Shoot length, shoot dry weight, root fresh weight, root dry weight, relative water content, MDA content, and proline content could be used to quantify salt tolerance of potato in vitro. This study provides reference for evaluating salt tolerance of potato in vitro, and provides germplasm resources for breeding salt tolerant potato varieties.

Biological mechanism and its application in the prediction of apple flowering time.

FENG Jian-she, XUE Xiao-ping, LI Man-hua, LI Nan

2022, 41(3):  618-624.  doi:10.13292/j.1000-4890.202202.024

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By the correlation analysis, we determined biological indices such as “bud initiation”, “high temperature acceleration”, “low temperature retardation”, and the climate trend background of spring warming. Taking Shandong Province as an example, we established forecast models with biological implications by stepwise regression. The results showed that the first day when daily average temperature steadily passed 5 ℃ is more suitable as the temperature index of “flower bud sprouting” by comprehensive considerations of the correlation coefficient and the number of days required for apple flowering. The critical temperature of “high temperature acceleration” and “low temperature hysteresis” was “daily highest temperature ≥20 ℃” and “daily lowest temperature ≤1 ℃”respectively as found by correlation analysis. Dynamic prediction models were established with different starting point and ending point of accumulated temperature. The prediction effect of the model with accumulated temperature starting point of March 1 and the daily average temperature steadily passed through 5 ℃ is fairly good, but without significant advantage in terms of real prediction effectiveness. With the help of numerical prediction products, the restriction of real data can be overcome, which would improve the initiative and flexibility of forecast services.