摘要：鼠害是影响草原生态健康的重要因素，了解小型啮齿动物种群密度时空分布特征，对精准的鼠害综合防治具有重要意义。以往对小型啮齿动物时空分布的研究多局限于静态的站点分布或小范围的种群密度时间变化分析，缺乏对较大时空尺度小型啮齿动物种群密度变化的分析。从已发表的文献中收集了天山北坡草地1982—2015年小尺度的有效洞口密度实地调查信息，同时结合环境因子数据，再根据海拔将研究区划分为≤900 m和>900 m 2类，运用Cubist模型和随机森林模型，分析有效洞口密度时空分布。结果表明：（1）1982—2015年天山北坡海拔≤900 m地区的有效洞口密度总体呈增加趋势，而海拔>900 m的地区总体呈减少趋势。基于Cubist模型构建有效洞口密度与环境因子的模型拟合精度明显优于随机森林模型。（2）植被状况、气象因子和放牧强度是天山北坡有效洞口密度时空分布主要的环境驱动因素。在天山北坡内海拔≤900 m和>900 m的地区中，有效洞口密度的驱动机制存在着显著差异。（3）在海拔≤900 m地区，影响有效洞口密度时空分布主要是叶面积指数，而对于海拔>900 m地区为归一化植被指数。这可能是受到大沙鼠（Rhom⁃bomys opimus）和黄兔尾鼠（Eolagurus luteus）消耗不同类型植被的影响。
摘要：Abstract: A knowledge of the tree-ring stable nitrogen isotope ratio (δ15N) can deepen our understanding of forest ecosystem dynamics by indicating the long-term availability, cycling and sources of nitrogen (N). However, the radial mobility of N blurs the interannual variations in the long-term N records. Previous studies of the chemical extraction of tree rings before analysis had produced inconsistent results and it is still unclear whether it is necessary to pre-treat wood samples from specific tree species to remove soluble N compounds before determining the δ15N values. We compared the effects of pre-treatment with organic solvents and hot ultrapure water on the N concentration and δ15N of tree rings from endemic Qinghai spruce (Picea crassifolia) growing in the interior of the central Qilian Mountains, China, during the last 60 a. We assessed the effects of different preparation protocols on the removal of the labile N compounds and investigated the need to pre-treat wood samples before determining the δ15N values of tree rings. Increasing trends of the tree-ring N concentration were consistently observed in both the extracted and unextracted wood samples. The total N removed by extraction with organic solvents was about 17.60%, with a significantly higher amount in the sapwood section (P<0.01). The δ15N values of tree rings decreased consistently from 1960 to 2019 in both the extracted and unextracted wood samples. Extraction with organic solvents increased the δ15N values markedly by about 5.2‰ and reduced the variations in the δ15N series. However, extraction with hot ultrapure water had little effect, with only a slight decrease in the δ15N values of about 0.5‰. Our results showed that the radial pattern in the inter-ring movement of N in Qinghai spruce was not minimized by extraction with either organic solvents or hot ultrapure water. It is unnecessary to conduct hot ultrapure water extraction for the wood samples from Qinghai spruce because of its negligible effect on the removal of the labile N. The δ15N variation trend of tree rings in the unextracted wood samples was not influenced by the heartwood–sapwood transition zone. We suggest that the δ15N values of the unextracted wood samples of the climate-sensitive Qinghai spruce could be used to explore the ecophysiological dynamics while focusing on the long-term variations.
Abstract: Litter decomposition is an important component of the nutrient recycling process and is highly sensitive to climate change. However, the impacts of warming and increased precipitation on litter decomposition have not been well studied, especially in the alpine grassland of Tianshan Mountains. We conducted a manipulative warming and increased precipitation experiment combined with different grassland types to examine the impact of litter quality and climate change on the litter decomposition rate based on three dominant species (Astragalus mongholicus, Potentilla anserina, and Festuca ovina) in Tianshan Mountains from 2019 to 2021. The results of this study indicated there were significant differences in litter quality, specific leaf area, and leaf dry matter content. In addition, litter quality exerted significant effects on litter decomposition, and the litter decomposition rate varied in different grassland types. Increased precipitation significantly accelerated the litter decomposition of P. anserina; however, it had no significant effect on the litter decomposition of A. mongholicus and F. ovina. However, warming consistently decreased the litter decomposition rate, with the strongest impact on the litter decomposition of F. ovina. There was a significant interaction between increased precipitation and litter type, but there was no significant interaction between warming and litter type. These results indicated that warming and increased precipitation significantly influenced litter decomposition; however, the strength was dependent on litter quality. In addition, soil water content played a crucial role in regulating litter decomposition in different grassland types. Moreover, we found that the litter decomposition rate exhibited a hump-shaped or linear response to the increase of soil water content. Our study emphasizes that ongoing climate change significantly altered litter decomposition in the alpine grassland, which is of great significance for understanding the nutrient supply and turnover of litter.
Abstract: Caragana korshinskii Kom. and Tamarix ramosissima Ledeb. are pioneer shrubs for water and soil conservation, and for windbreak and sand fixation in arid and semi-arid areas. Understanding the water use characteristics of different pioneer shrubs at different ages is of great importance for their survival when extreme rainfall occurs. In recent years, the stable isotope tracing technique has been used in exploring the water use strategies of plants. However, the widespread δ2H offsets of stem water from its potential sources result in conflicting interpretations of water utilization of plants in arid and semi-arid areas. In this study, we used three sets of hydrogen and oxygen stable isotope data (δ2H and δ18O, corrected δ2H_c1 based on SW-excess and δ18O, and corrected δ2H_c2 based on −8.1‰ and δ18O) as inputs for the MixSIAR model to explore the water use characteristics of C. korshinskii and T. ramosissima at different ages and in response to rainfall. The results showed that δ2H_c1 and δ18O have the best performance, and the contribution rate of deep soil water was underestimated because of δ2H offset. During the dry periods, C. korshinskii and T. ramosissima at different ages both obtained mostly water from deeper soil layers. After rainfall, the proportions of surface (0–10 cm) and shallow (10–40 cm) soil water for C. korshinskii and T. ramosissima at different ages both increased. Nevertheless, there were different response mechanisms of these two plants for rainfall. In addition, C. korshinskii absorbed various potential water sources, while T. ramosissima only used deep water. These flexible water use characteristics of C. korshinskii and T. ramosissima might facilitate the coexistence of plants once extreme rainfall occurs. Thus, reasonable allocation of different plants may be a good vegetation restoration program in western Chinese Loess Plateau.
Abstract: Rapid industrialization and urbanization have led to the most serious habitat degradation in China, especially in the loess hilly area of the Yellow River Basin, where the ecological environment is relatively fragile. The contradiction between economic development and ecological environment protection has aroused widespread concern. In this study, we used the habitat quality of Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST-HQ) model at different scales to evaluate the dynamic evolution characteristics of habitat quality in Lanzhou City, Gansu Province of China. The spatiotemporal variations of habitat quality were analyzed by spatial autocorrelation. A Geographical Detector (Geodetector) model was used to explore the driving factors that influencing the spatial differentiation of habitat quality, including natural factors, socio-economic factors, and ecological protection factors. The results showed that the habitat quality index of Lanzhou City decreased from 0.4638 to 0.4548 during 2000–2018. The areas with reduced the habitat quality index were mainly located in the Yellow River Basin and Qinwangchuan Basin, where are the main urban areas and the new economic development areas, respectively. The spatial distribution of habitat quality presented a trend of high in the surrounding areas and low in the middle, and showed a significant positive spatial autocorrelation. With the increase of study scale, the spatial distribution of habitat quality changed from concentrated to dispersed. The spatial differentiation of habitat quality in the study area was the result of multiple factors. Among them, topographic relief and slope were the key factors. The synergistic enhancement among these driving factors intensified the spatial differentiation of habitat quality. The findings of this study can provide a scientific basis for land resources utilization and ecosystem restoration in the arid and semi-arid land.
Abstract: Robinia pseudoacacia L. (RP) restoration has increased vegetation cover in semi-arid regions on the Loess Plateau of China, but ecological problems have also occurred due to RP restoration, such as reduced soil moisture. Further, it is still uncertain how microbial diversity, composition and assembly processes change with RP restoration in semi-arid regions. Therefore, amplicon sequencing of small subunit ribosomal ribonucleic acid (16S rRNA) and internal transcribed spacer (ITS) genes was performed to study soil bacterial and fungal diversity, composition and assembly processes at four study sites with different stand ages of RP plantations (Y10, RP plantation with stand ages less than 10 a; Y15, RP plantation with stand ages approximately 15 a; Y25, RP plantation with stand ages approximately 25 a; and Y40, RP plantation with stand ages approximately 40 a) along a 40-a chronosequence on the Loess Plateau. The diversity of soil bacteria and fungi increased significantly during the restoration period from 10 to 15 a (P<0.05). However, compared with Y15, bacterial diversity was lower at Y25 and Y40, and fungal diversity remained stable during the restoration period between 25 and 40 a. The relative abundances of Proteobacteria and Ascomycota increased during the restoration period from 10 to 15 a. Conversely, after 15 a of restoration, they both decreased, whereas the relative abundances of Actinomycetes, Acidobacteria and Basidiomycota gradually increased. The variations in soil bacterial communities were mainly related to changes in soil total nitrogen, nitrate nitrogen and moisture contents, while soil fungal communities were mainly shaped by soil organic carbon and nitrate nitrogen contents. Bacterial communities were structured by the heterogeneous selection and stochastic process, while fungal communities were structured primarily by the stochastic process. The RP restoration induced an increase in the relative importance of heterogeneous selection on bacterial communities. Overall, this study reveals the changes in microbial diversity, community composition and assembly processes with RP restoration on the Loess Plateau and provides a new perspective on the effects of vegetation restoration on soil microbial communities in semi-arid regions.
处理小区均为167株梨树（约占地667 m2），重复3次；各小区土样分0~20 cm、20~40 cm、40~60 cm
和全盐量均有降低。（3）黑地膜覆盖下0~20 cm和20~40 cm土层的碱解氮含量分别为73.00 mg·g-1和
64.53 mg·g-1，均显著地高于无覆盖处理，无覆盖条件下土壤碱解氮在深层（40~60 cm土层）积累较
多，显著地高于玉米秸秆和黑地膜覆盖；各处理0~20 cm和20~40 cm土层速效磷含量差异显著，大
盖处理效果均好于无覆盖处理，其中玉米秸秆覆盖在0~20 cm和20~40 cm土层综合得分分别为
为进一步研究胡麻生理生化代谢指标响应干旱胁迫时对胡麻产量的影响，采用盆栽控水法模拟胡麻干旱胁迫，依据2013—2014年甘肃省定西市西巩驿镇胡麻试验数据，建立并检验胡麻干旱胁迫模型，模拟干旱胁迫时对胡麻生理生化指标及产量影响，利用均方根误差（RMSE）和决定系数（R2）描述模型拟合度。结果表明：（1）模型产量模拟值的RMSE为41.3159~155.6685 kg·hm-2，平均值为80.1837 kg·hm-2；R2为0.8929~0.9894，平均值为0.9387，该模型具有较好的拟合度、可行性也较强。（2）在重度干旱胁迫下，抗氧化代谢指标——超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）中，CAT活性表现趋势为下降，终花期POD活性增幅（26.09%~28.00%）最大；渗透调节的3种物质含量均显著上升，其中脯氨酸增幅最大，达236.22%。（3）呈现出极显著相关性的各指标有3组，分别是脯氨酸与叶绿素、丙二醛和CAT活性；可溶性蛋白与丙二醛和CAT活性；POD活性与SOD活性。胡麻生理生化指标响应不同程度干旱胁迫与胡麻的产量有极强的关联，此模型的建立是对胡麻生理生化指标响应干旱胁迫的科学补充，进一步为胡麻的高效生产管理及农业生产系统提供理论依据和支持。
为分析黄河源区高寒草甸植物单根的抗拉力学性质及其护岸的微观力学机理，以华扁穗草、线叶嵩草和金露梅3种优势滨河植物为研究对象，通过开展单根拉伸试验和石蜡切片试验，定量分析3种植物单根力学特性及其与微观结构的关系。结果表明，当根径在<0.5 mm、0.5~1.0 mm和>1.0 mm 3个根径级别时，3种植物单根抗拉力和延伸率均随根径增大而增大；单根抗拉强度和杨氏模量均随根径增大而减小；根系应力-应变曲线表现为单峰曲线。灌木金露梅单根平均抗拉强度是草本植物华扁穗草和线叶嵩草的1.56倍和1.25倍，华扁穗草单根平均延伸率是线叶嵩草和金露梅的1.06倍和1.36倍。草本植物单根抗拉强度主要与其维管柱面积占比有关；而灌木金露梅单根抗拉强度主要与其周皮和次生木质部面积占比有关。综合来看，华扁穗草和线叶嵩草根系抵抗变形的能力较强，主要发挥加筋和减缓河岸变形、破坏的作用；而金露梅刚度强、抗拉强度较大，主要发挥固土护岸的作用。研究结果可为筛选黄河源区优势护岸植物提供科学依据。
为研究黄河源区高寒草地退化对土体理化性质及根-土复合体抗剪强度影响，本研究以位于黄河源区青海河南县地区高寒草地为研究对象，通过开展不同退化程度草地野外取样及室内试验，获得土体密度、含水率、颗粒级配、土壤营养元素和植物根-土复合体抗剪强度指标及变化特征。结果表明：（1）在相同退化程度和取样深度下，南旗村试验区土体平均密度为启龙牧场的1.02~1.29倍，土体含水率表现出随着草地退化程度加剧而降低；2个试验区土壤有机质、全氮、全磷等随着草地退化程度加剧而降低。（2）区内根-土复合体抗剪强度随草地退化程度加剧而降低，启龙牧场与南旗村试验区其上层（0~10 cm）、下层（10~20 cm）降低幅度分别为72.05%、48.77%和77.26%、81.37%；进一步研究表明，根-土复合体所含根系数量和根系干重表现出随着草地退化程度加剧呈逐渐降低，启龙牧场与南旗村试验区其上层和下层的根-土复合体所含根系数量降低幅度分别为79.28%、75.93%和92.48%、39.59%。（3）根据WWM模型和Pearson相关性分析结果可知，根系数量和营养元素含量减少对根-土复合体抗剪强度具有显著降低作用。本研究结果对于黄河源区高寒草地合理防治草地退化，以及水土流失、浅层滑坡等灾害具有实际指导意义。
摘要： 为了解地形因子对树种分布变化的影响，更科学地进行防护林空间配置，本研究利用陕西 省延安市吴起县数字高程模型（DEM）数据以及两期树种分布数据，采用 Pearson 相关分析和随机森林模型，探讨陕西省延安市吴起县典型造林树种［刺槐（Robinia pseudoacacia）、山杏（Armeniaca si⁃birica）、油松（Pinus tabuliformis）和沙棘（Hippophae rhamnoides）］与地形因子（海拔、坡度、坡向、曲 率、地形起伏度和地形粗糙度）的关系。结果表明：（1）2007—2019 年刺槐、山杏和油松的分布呈增 加趋势，研究区内分别在 83.373%、73.271%和 72.415%的区域呈增加趋势；沙棘的分布呈减少趋 势，在 61.737%的区域衰退。（2）通过 Pearson 相关分析和随机森林重要性检验，海拔和坡向是影响 黄土高原地区典型造林树种分布的主要地形因子。（3）4 种主要造林乔灌木树种刺槐、山杏、油松和 沙棘适宜生长海拔范围分别为 1410.105~1510.215 m、1444.873~1553.210 m、1380.132~1451.762 m 和 1365.621~1562.348 m。（4）刺 槐 适 宜 生 长 坡 向 范 围 为 0~20.520° 、50.280° ~62.310° 、82.440° ~ 95.280°和 277.280°~360.000°；山杏适宜生长坡向范围为 0~81.270°和 265.310°~360.000°；油松适宜 生长坡向范围为 0~100.180°；沙棘适宜生长坡向范围为 0~74.540°和 280.820°~360.000°。