|Soil water content (SWC) is a key factor limiting ecosystem sustainability in arid and semi-arid areas of the Hexi Corridor of China, which is characterized by an ecological environment that is vulnerable to climate change. However, there is a knowledge gap regarding the large-scale spatial distribution of SWC in this region. The specific objectives of this study were to determine the spatial distribution patterns of SWC across the Hexi Corridor and identify the factors responsible for spatial variation of SWC at a regional scale. This study collected and analyzed SWC in the 0–100 cm soil profile from 109 field sampling sites (farmland, grassland and forestland) across the Hexi Corridor in 2017. We selected 17 factors, including land use, topography (latitude, longitude, elevation, slope gradient, and slope aspect), soil properties (soil clay content, soil silt content, soil bulk density, saturated hydraulic conductivity, field capacity, and soil organic carbon content), climate factors (mean annual precipitation, potential evaporation, and aridity index), plant characteristic (vegetation coverage) and planting pattern (irrigation or rain-fed), as possible environmental variables to analyze their effects on SWC. The results showed that SWC was 0.083 (±0.067) g/g in the 0–100 cm soil profile and decreased in the order of farmland, grassland and forestland. The SWC in the upper soil layers (0–20, 20–40 and 40–60 cm) had obvious difference when the mean annual precipitation differed by 200 mm. The SWC decreased from southeast to northwest following the same pattern as precipitation, and had a moderate to strong spatial dependence in a large effective range (75–378 km). The SWC showed a similar distribution and had no significant difference between soil layers in the 0–100 cm soil profile. The principal component analysis showed that the mean annual precipitation, geographical position (longitude and latitude) and soil properties (soil bulk density and soil clay content) were the main factors dominating the variance of environmental variables. A stepwise linear regression equation showed that plant characteristic (vegetation coverage) and soil properties (soil organic carbon content, field capacity and soil clay content) were the optimal factors to predict the variation of SWC. Soil clay content could be better to explain the SWC variation in the deeper soil layers compared with the other factors.|
|Soil salinization is a serious ecological and environmental problem because it adversely affects sustainable development worldwide, especially in arid and semi-arid regions. It is crucial and urgent that advanced technologies are used to efficiently and accurately assess the status of salinization processes. Case studies to determine the relations between particular types of salinization and their spectral reflectances are essential because of the distinctive characteristics of the reflectance spectra of particular salts. During April 2015 we collected surface soil samples (0–10 cm depth) at 64 field sites in the downstream area of Minqin Oasis in Northwest China, an area that is undergoing serious salinization. We developed a linear model for determination of salt content in soil from hyperspectral data as follows. First, we undertook chemical analysis of the soil samples to determine their soluble salt contents. We then measured the reflectance spectra of the soil samples, which we post-processed using a continuum-removed reflectance algorithm to enhance the absorption features and better discriminate subtle differences in spectral features. We applied a normalized difference salinity index to the continuum-removed hyperspectral data to obtain all possible waveband pairs. Correlation of the indices obtained for all of the waveband pairs with the wavebands corresponding to measured soil salinities showed that two wavebands centred at wavelengths of 1358 and 2382 nm had the highest sensitivity to salinity. We then applied the linear regression modelling to the data from half of the soil samples to develop a soil salinity index for the relationships between wavebands and laboratory measured soluble salt content. We used the hyperspectral data from the remaining samples to validate the model. The salt content in soil from Minqin Oasis were well produced by the model. Our results indicate that wavelengths at 1358 and 2382 nm are the optimal wavebands for monitoring the concentrations of chlorine and sulphate compounds, the predominant salts at Minqin Oasis. Our modelling provides a reference for future case studies on the use of hyperspectral data for predictive quantitative estimation of salt content in soils in arid regions. Further research is warranted on the application of this method to remotely sensed hyperspectral data to investigate its potential use for large-scale mapping of the extent and severity of soil salinity.|
|With the aim to investigate if the halophyte Halothamnus iraqensis Botsch. can be suitable for re-vegetation and remediation of salt-affected lands, this study evaluated (1) the effects of photoperiod, thermoperiod, storage period and wings' presence on its seed germination, and (2) the ability of its seeds to have successful germination recovery after salt stress. Germination tests in different photoperiods (12 h light/12 h darkness and total darkness) and thermoperiods (15°C/20°C and 20°C/25°C) were conducted for seeds collected in 2012, 2013, 2014, 2015 and 2016. The seeds collected in 2016 were sown under different salinity levels (0, 100, 200, 400 and 600 mM NaCl) to assess the salinity tolerance during the germination. Wings' presence highly inhibited seed germination of this species in both photoperiods and thermoperiods under all salinity level treatments. In addition, the germination recovery occurred well when seeds were deprived of their wings. The photoperiod of 12 h light/12 h darkness and the thermoperiod of 15°C/20°C were the best conditions for seed germination. Germination percentages of H. iraqensis seeds decreased with the increasing storage duration, especially after three years of the collection. In addition, H. iraqensis seeds were able to germinate under different salinity levels, and their germination percentages decreased with increasing salinity levels. H. iraqensis seeds have the ability to recover their germination after alleviating the salt stress, irrespective of photoperiod, highlighting the halophilous character of this species.|
|Intraspecific trait variation and heritability in different environmental conditions not only suggest a potential for an evolutionary response but also have important ecological consequences at the population, community, and ecosystem levels. However, the contribution of quantitative trait variation within a grassland species to evolutionary responses or ecological consequences is seldom documented. Leymus chinensis is an important dominant species in semi-arid grasslands of China, which has seriously suffered from drought and high temperature stresses in recent decades. In the present study, we measured variation and heritability of 10 quantitative traits, namely the number of tillers, maximum shoot height, number of rhizomes, maximum rhizome length, rhizome mass, aboveground mass, root mass, maximum net photosynthetic rate (Pmax), specific leaf area (SLA), and leaf length to leaf width ratio (LL/LW), for 10 genotypes of L. chinensis under one non-stress (Ck) condition and three environmental stress conditions (i.e., drought (Dr), high temperature (Ht), and both drought and high temperature (DrHt)). Result indicated that (1) the interaction of genotype and environmental condition (G×E) was significant for 6 traits but not significant for the other 4 traits as shown by two-way analysis of variance (ANOVA), suggesting that different selection forces were placed for different traits on the factors dominating phenotypic responses to different environmental conditions. Moreover, these significant G×E effects on traits indicated significantly different phenotypic adaptive responses among L. chinensis genotypes to different environmental conditions. Additionally, individuals could be grouped according to environmental condition rather than genotype as shown by canonical discriminant analysis, indicating that environmental condition played a more important role in affecting phenotypic variation than genotype; (2) by one-way ANOVA, significant differences among L. chinensis genotypes were found in all 10 traits under Ck and Dr conditions, in 8 traits under DrHt condition and only in 4 traits under Ht condition; and (3) all 10 traits showed relatively low or non-measurable broad-sense heritability (H2) under stress conditions. However, the lowest H2 value for most traits did not occur under DrHt condition, which supported the hypothesis of 'unfavorable conditions have unpredictable effects' rather than 'unfavorable conditions decrease heritability'. Results from our experiment might aid to improve predictions on the potential impacts of climate changes on L. chinensis and eventually species conservation and ecosystem restoration.|
Soil organic carbon (SOC) and soil total nitrogen (STN) in arid regions are important components of global C and the N cycles, and their response to climate change will have important implications for both ecosystem processes and global climate feedbacks. Grassland ecosystems of Funyun County in the southern foot of the Altay Mountains are characterized by complex topography, suggesting large variability in the spatial distribution of SOC and STN. However, there has been little investigation of SOC and STN on grasslands in arid regions with a mountain-basin structure. Therefore, we investigated the characteristics of SOC and STN in different grassland types in a mountain-basin system at the southern foot of the Altai Mountains, north of the Junggar Basin in China, and explored their potential influencing factors and relationships with meteorological factors and soil properties. We found that the concentrations and storages of SOC and STN varied significantly with grassland type, and showed a decreasing trend along a decreasing elevation gradient in alpine meadow, mountain meadow, temperate typical steppe, temperate steppe desert, and temperate steppe desert. In addition, the SOC and STN concentrations decreased with depth, except in the temperate desert steppe. According to Pearson's correlation values and redundancy analysis, the mean annual precipitation, soil moisture content and soil available N concentration were significantly positively correlated with the SOC and STN concentrations. In contrast, the mean annual temperature, pH, and soil bulk density were significantly and negatively correlated with the SOC and STN concentrations. The mean annual precipitation and mean annual temperature were the primary factors related to the SOC and STN concentrations. The distributions of the SOC and STN concentrations were highly regulated by the elevation-induced differences in meteorological factors. Mean annual precipitation and mean annual temperature together explained 97.85% and 98.38% of the overall variations in the SOC and STN concentrations, respectively, at soil depth of 0–40 cm, with precipitation making the greatest contribution. Our results provide a basis for estimating and predicting SOC and STN concentrations in grasslands in arid regions with a mountain-basin structure.
|第九届国际生态系统服务大会（9th Ecosystem Services Partnership World Conference，ESP9）于2017年12月11日-12月15日在中国深圳召开。本次会议主题为"增强生态系统服务，促进生态文明建设"，旨在探讨生态系统服务科学热点问题，交流最新研究成果，并寻求基于自然的绿色解决方案，进一步推动生态修复与环境保护政策及实践的有机结合，为加强生态修复与生态治理国际合作提供良好交流平台。本文旨在对本次会议的7场特邀报告，30个主题会场内容进行综述，内容围绕当前生态系统服务领域的前沿与热点领域展开，包括生态系统保护管理及可持续性、生物多样性、生态系统脆弱性、生态系统服务评估与模型、气候变化、土地利用与景观、政策与决策分析等方向。|
|以中国知网学术期刊网络出版总库（CNKI）和WEB OF SCIENCE（WOS）中1986-2016年的期刊论文为数据源，以非点源污染或面源污染（non-point pollution or Diffused pollution or non-point source pollution）和模型（Model）为主题进行检索，共检索到国内文献1474篇和国外文献1046篇。利用共词分析方法，同时结合CiteSpace、SPSS和Bibexcel软件对检索结果进行分析，利用Ucinet和NetDraw软件绘制出共词网络可视图，依据处理后的结果对非点源污染模型的研究趋势进行系统的梳理分析，从多个角度对非点源污染模型的研究现状与发展情况进行分析，包括发表文章的关键词、年代分布、发表期刊、著者、高被引文章等，在此基础上分析出国内外在非点源污染模型领域中的研究概况及研究热点，明确非点源污染模型研究的探索方向，为以后非点源污染模型的研究提供理论依据。|
|以WEB OF SCIENCE数据库和中国知网学术期刊网络出版总库中1993-2016年期刊论文作为数据源，以"water footprint（水足迹） "OR（或）" virtual water（虚拟水）"为关键词进行文献检索，利用CiteSpace可视化文献分析工具，对检索出的文献分别进行关键词、作者、发文机构和载文期刊分析，并绘制出相关知识图谱，以此来探讨水足迹研究领域的发展现状以及未来的相关研究热点。结果表明：①水足迹领域相关研究文献数量不断增长，水足迹越来越受到中外学者的关注；②国外水足迹研究主要围绕虚拟水和水足迹展开，且对于水权问题的关注度较高，国内水足迹研究主要着眼于虚拟水贸易和虚拟水消费，应用型研究成为水足迹研究的热点，未来水足迹研究热点可能会围绕"水-粮食-能源"三者的耦合展开，对于水足迹与社会经济问题相结合的研究力度会逐渐增大；③水足迹领域中外文文献的发文作者都集中于少数研究人员，主要发文作者的研究奠定了水足迹研究的基础；④主要的发文机构有Univ Twente、中国科学院等，主要的载文期刊有ECOL ECON、HYDROL EARTH SYST SC、WATER RESOUR MANAG以及《资源科学》《中国人口·资源与环境》《生态学报》等。根据水足迹研究现状，给出了关于水足迹领域未来发展的建议。|