Water use characteristics of coexisting sand-binding vegetation in two typical soil habitats in the desert steppe of China

Understanding the water use characteristics and water relationship of coexisting vegetation in a mixed-species plantation of trees and shrubs is crucial for the sustainable restoration of degraded arid areas. This study investigated the water use characteristic of coexisting sand-binding vegetation combinations in the sierozem habitat (Populus przewalskii Maxim namely Populus-S and Caragana liouana) and aeolian sandy soil habitats (Populus przewalskii Maxim namely Populus-A and Salix psammophila) of the desert steppe. By analysing the δ²H and δ¹⁸O isotopes in xylem, soil water, groundwater and precipitation, a Bayesian MixSIAR model was employed to quantitatively assess the water utilization characteristics of plants. Throughout the growing season, in the sierozem habitat, C. liouana exhibits the highest efficiency in utilizing soil moisture above 60 cm (53.45%) and displays adaptable water use strategies. In contrast, Populus-A predominantly relies on deep soil moisture below 60 cm plus groundwater (63.89%). In the aeolian sandy soil habitat, both Populus-A and S. psammophila similarly favour deep soil moisture below the 60 cm soil plus groundwater (66.77% and 67.60%, respectively). During the transition period from the dry to the wet seasons, although both Populus-A and S. psammophila in the aeolian sandy soil habitat shifted their water sources from deeper to shallower ones, there was considerable overlap in the water sources used by Populus-A and S. psammophila. This overlap led to competition for water resources and exacerbated the depletion of deep soil moisture in both seasons. Conversely, in the sierozem habitat, the partitioning of water sources between Populus-S and C. liouana facilitated the allocation and utilization of water resources between the two species. The findings highlight the need for species-specific consideration in water resource allocation within mixed-species plantations of trees and shrubs, which is crucial for sustainable vegetation restoration in sand-binding ecosystems.     

Revealing ecosystem services relationships and their driving factors for five basins of Beijing

A clear understanding of the relationships among multiple ecosystem services(ESs) is the foundation for sustainable urban ecosystem management. Quantitatively identifying the factors that influence ES trade-offs and synergies can contribute to deepening ES research, from knowledge building to decision making. This study simulated soil conservation, water yield and carbon sequestration in Beijing, China, from 2015–2018. The spatial trade-offs and synergies of these three ESs within the five major river basins in Beijing were explored using geographically weighted regression. Furthermore, geographical detector was applied to quantitatively identify the driving mechanism of the environmental factors for the ES trade-offs and synergies. The results show the following:(1) the spatial relationships between soil conservation and water yield, as well as between water yield and carbon sequestration, were mainly trade-offs. There was a spatial synergy between soil conservation and carbon sequestration.(2) Regarding the spatial trade-off/synergy between soil conservation and water yield in Beijing, the dominant influencing factor was temperature/elevation, and the dominant interactions of the spatial trade-off and synergy between these two ESs in Beijing and the Chaobai River Basin are all manifested in the superposition of precipitation and potential evapotranspiration, temperature, and elevation.(3) Topographic factors were the dominant factors influencing the spatial relationship between soil conservation and carbon sequestration in Beijing and its five major river basins. As a result of the distribution of water systems and hydrological characteristics of the basins, differences were observed in the effects of different combinations of interaction factors on the spatial relationship between these two ESs in different basins.(4) Temperature had the strongest explanatory power in terms of the spatial trade-offs and synergies between water yield and carbon sequestration. The interactions between precipitation and temperature and between precipitation and elevation were the dominant interactions affecting the spatial relationship between water yield and carbon sequestration in Beijing. Overall, the explanatory power of influencing factors on the trade-offs and synergies and the degree of interaction between factors coexist in different basins with consistency and differences. Therefore, understanding the quantitative characteristics of basin-scale spatial trade-offs and synergies between ESs is important for ecosystem management and the promotion of synergy in different basins.     

沙漠地质记录和人类活动遗迹数据汇交规范化

数据汇交是实现数据共享的前提,是实现科学数据的持续累积、科学整合和有效管理可持续发展的重要基础.分析了沙漠地质记录和人类活动遗迹数据汇交规范化存在的问题,强调了制定沙漠地质记录和人类活动遗迹数据汇交规范的必要性,根据沙漠地质记录和人类活动遗迹资料的数据特性,对数据分类并建立不同专题数据库,因地制宜采纳国际和国内现行的规...     

我国常用湖泊营养状态指数研究进展与展望

湖泊(包括自然湖泊和人工水库)富营养化已成为世界性的环境问题,营养状态指数是目前最流行的富营养化水平量化方法。然而,不同营养状态指数的基本逻辑和适用水体等方面存在明显差异,不当选取可能会造成营养水平和相关水华风险的错误估计,并引发湖泊保护和修复措施的错位。鉴于此,本文对我国常用营养状态指数的构建思路、共性和差异以及不确定性来源等进行了综述。总体来看,营养状态指数基本构建思路分3种:1) Carlson指数型(如TSI),以透明度(SD)为核心参数,使用SD的2倍变化对应指数的10分差值,假定SD 为64 m时记为指数值0分;2)改良TSI指数型(如TSIm),以叶绿素a(Chl.a)为核心参数,使用Chl.a的2.5倍变化对应指数的10分差值,假定Chl.a 1000 μg/L对应该指数100分;3)营养足迹指数型(如TFI),该指数亦使用Chl.a指示藻类生物量,Chl.a的e倍关系对应藻类生物量的二倍变化和指数10分差值,假定Chl.a为10 μg/L时对应该指数50分。根据上述假设得出对应的基础参数评估方程,然后均以基础参数(SD或Chl.a)与衍生参数间的经验方程 “直接替换”获得衍生参数的评估方程。如上可知,营养状态指数均体现了数值增大表征藻类初级生产力和伴随的水华风险提高的共性,同时本文也从:1)数据集属性和基础指标评估方程获取的方法;2)衍生指标评估方程获取的统计原理;3)分项指标的权重设置方式3个方面分析营养状态指数之间的差异性。未来展望方面,首先,鉴于当前营养状态指数均属于通用性指数,因而建议未来基于上述3种基本类型开发因地制宜的营养状态指数,实现湖泊藻类生产力和水华风险的精准指示;其次,营养状态指数的生态学依据是藻类限制因子理论,营养状态指数各分项指标(即基于总氮、总磷、SD和Chl.a)的差异可以指示初级生产力的限制因子,建议未来开展营养状态指数分项指标差异机制研究,以指导藻类水华防控措施精准施策;再次,除富营养化外,湖泊生态健康受损往往也与其它压力有关,建议未来开展湖泊生态健康对富营养化和其他压力的综合响应机制研究,制定服务于湖泊生态系统健康提升的精准调控路径。本文目的并非将营养状态指数的通用属性“复杂化”,而是旨在阐明营养状态指数的“前世今生”,进而为广大湖泊富营养化相关人员使用指数时提供参考,也希望为我国湖泊营养状态精准量化、后续保护和修复措施的精准实施提供科学依据。     

全球气候变化对红树林生态系统的影响、挑战与机遇

红树林是以红树植物为主体的常绿灌木或乔木组成的潮滩湿地木本植物群落, 具有“四高”特性(高生产力、高归还率、高分解率和高抗逆性)的典型海洋生态系统; 目前, 全球约有红树林1700万公顷, 主要分布在南北半球25℃等温线内。红树林生态系统的净初级生产力高达2000gC·m^-2·a^-1, 具有高强度的物质循环、能量流动以及丰富的生物多样性, 对热带、亚热带海洋生态系统的维持与发展起到关键作用, 并在全球变化过程中扮演着十分重要的角色。近30年来, 全球气候变化已引起了国内外学者的极大关注。红树林生态系统位于热带、亚热带海岸潮间带, 是一个脆弱的、敏感的生态系统, 也是首先受全球气候变化影响的典型海洋生态系统之一。作为全球海岸带地区应对全球气候变化最为重要的生态屏障之一, 气候变化将严重影响着全球红树林的生存和分布方式。本文将从全球变暖、海平面上升、大气中CO₂浓度的增加和极端天气4个主要方面, 揭示全球气候变化对红树林生态系统的影响与变化特征, 阐述红树林对全球变暖、海平面上升、大气中CO₂浓度增加和极端天气响应与适应的生态学机制, 并简要概述了红树林在减缓全球气候变化危害中的重要作用。全球气候变化也将为红树林的研究、保护和发展带来机遇与挑战。     

地球生态系统的气温和水温补充机制

首次提出了地球生态系统的气温和水温补充机制,并用框图模型说明了补充机制在运行过程中的每个流程,阐明了人类对生态环境的影响过程、生态环境变化对地球生态系统的影响过程以及地球生态系统对环境变化的响应过程,解释了气温和水温的补充起因。研究结果表明,人类是引起环境变化的起源以及其变化后的结果又作用于人类,即人类排放二氧化碳引起气温和水温的上升,地球生态系统又借助其补充机制使得气温和水温下降恢复到正常的动态平衡。尽管这个补充机制带来了沙尘暴、洪水和风暴潮,但由人类引起水温和气温上升造成的灾害要比自然界中这3种灾害要深重得多。自然界的这3种灾害是局部的、短期的,而人类引起水温和气温上升的灾害却是全球的、长期的。     

土壤水热条件对祁连山荒漠草原土壤CO2通量的影响

采用美国Li-COR公司生产的LI-6400-09土壤呼吸室和LI-6400便携式光合作用测量系统,在2004年生长季节对祁连山荒漠草原土壤CO2通量与温度和土壤水分的关系进行了连续观测研究。结果显示,基于室内试验数据,土壤CO2通量与土壤温度及土壤含水量的关系都可以用曲线方程很好地模拟。通过野外对祁连山荒漠草原土壤CO2通量、土壤温度、土壤含水量和降水等因子的观测发现,生长季节土壤CO2通量的日平均值介于1.94～9.32μmol.m-2.s-1。土壤CO2通量7～8月份达到最大值,5月与9月份次之,整个生长过程总的变化趋势呈单峰曲线形式。在5～11月份7个月的时间里,祁连山荒漠草原CO2释放量大约为1.01×108μmol.m-2。此外,加水试验也表明在干旱季节土壤水分对土壤CO2通量整体变化的重要性。     

古尔班通古特沙漠风沙土土壤蒸发特征

土壤表面蒸发是降水的无效损失,其大小直接决定着降水转化为有效土壤水的效率,从而间接决定了植物可利用水分的多寡。在降水稀少的沙漠区,定量认识土壤蒸发的大小和其所占降水的比例显得尤为重要。在2004年全生长期(5~9月)应用自制的微型蒸渗仪(Micro-Lysime-ter)测定了风沙土(有结皮覆盖的丘间低地和裸露沙丘顶部)和对照的荒漠盐碱土的土壤蒸发。结果表明:在相似的气象条件下,风沙土区的丘间低地和荒漠盐碱土的日平均蒸发量分别约是裸露沙丘(风沙土区)的2倍和3倍。整个生长期裸露沙丘的累积蒸发量为18.7mm,丘间低地为38.8mm,荒漠盐碱土为52.1mm。根据整个观测期的累积蒸发量和累积降雨量计算得出的蒸发降雨比分别为:裸露沙丘0.20,丘间低地0.42,荒漠盐碱土0.62,表明裸露沙丘由降水转化为土壤水而储存的比率最高。同时,从数据分析中可以看出:在风沙土区0~5cm土层的含水量对土壤蒸发起决定作用,而盐碱土区的土壤蒸发则受到更深层次土壤水分的影响。裸露沙丘低的土壤蒸发、高的降水转化效率,为植被恢复奠定了良好的基础。因此,裸露沙丘的低蒸发量可以视为植被状况对生态水文过程的一种良性反馈。     

氮输入对陆地生态系统碳循环关键过程的影响

碳氮作为陆地生态系统最关键的两大生源要素,它们在自然界的循环过程中不仅各自对全球变暖做出重要贡献,而且两者的循环过程显著耦合,互相影响各自的作用和效果。从氮元素对植物光合作用、呼吸作用以及土壤呼吸作用影响的角度入手,综述了氮输入对陆地生态系统碳固定和碳排放这两个碳循环关键过程的影响特征和机理,分析了陆地生态系统碳源汇对氮素变化响应的不确定性,在此基础上对未来的相关重点研究方向进行了探讨和展望。     

基于遥感的中国北方风沙地貌类型分析

风沙地貌在我国有广泛的分布,特别在北方,对区域生态安全、社会经济发展有重大影响。为了了解我国风沙地貌最新状况,通过解译2000~2002年的Landsat7 ETM影像,建立了我国风沙地貌类型数据库。对北方风沙地貌的分析表明:1.我国北方风沙地貌主要分布在新疆、内蒙古、青海、宁夏、甘肃、陕西、吉林、黑龙江8省区,其中以新疆、内蒙古的面积最广、地貌类型最丰富;2.类型多样性上,干旱区沙漠的地貌类型远比半干旱区的沙地丰富,其中有些类型分布普遍,还有些类型仅仅局限于特定区域,是在特定的风力、风向、植被等作用下形成的;3.沙丘动态上,沙漠除古尔班通古特与乌兰布和沙漠以固定、半固定为主外其他都以流动为主,沙地沙丘则以固定、半固定状态占优势。本文从沙丘形态类型角度分析了我国风沙地貌的最新特征,具有定位、定量特点,所建数据库不仅能用于风沙地貌的定期遥感监测,还能对沙丘形态演化进行定位监测研究。