A grassland ecosystem model of the Xilingol steppe, Inner Mongolia, China

The natural grassland ecosystem of the Xilingol steppe has traditionally been the source of the most productive and highest quality agriculture in northern China. Unfortunately, the area is now experiencing degradation due to resource overuse. In an attempt to forecast grassland production and to sustain the ecosystem, we built a time-dependent simulation model of the ecosystem based on long-range weather forecasts (several weeks to several months). The model incorporated five state variables including above- and belowground biomass, the amount of standing dead plant material, livestock (sheep) weight, and the amount of excrement per unit ground area. Within the model, solar light energy is fixed by grassland vegetation and flows through the other variables via a variety of organism-environment interactions. The model was written using a set of simultaneous differential equations and was numerically analyzed. The values of the time-dependent parameters controlling energy flow were determined based on data accumulated in experiments and field surveys executed at a grassland experimental station located in Xilingol, as well as by reference to related literature. We used daily meteorological data including air temperature and rainfall recorded at the Xilinhot Meteorological Observatory. Simulated results for several stocking densities coincided well with the data of aboveground plant biomass observed at the experimental station in 1990, 1993, and 1997. We obtained reasonable simulation results for five stocking densities, three air temperature patterns, and five rainfall patterns. When a month-long drought, which sometimes occurs in this area, was forecast by a local weather station, a decrease in grassland production was forecast by the model. Such forecasts will assist in the management of livestock, forage preservation, and grassland conservation.     

陆地生态系统呼吸温度敏感性及影响因素研究

陆地生态系统是全球第二大碳库,生态系统呼吸的任何细微变化都会在很大程度上影响着全球碳循环,改变大气中CO2浓度,而气候变化(如气候变暖)反过来会影响生态系统呼吸,从而增强温室效应.呼吸对温度的敏感性系数(Q10)是定量气候-碳循环反馈的一个关键参数,其相关研究仍存在较大的不确定性.本文探究了Q10的影响因素、时空变异性及机理解释,阐述了表观Q10和内在Q10的机理差异,指出内在Q10是有机物分解对温度的敏感性,更能反映生态系统碳循环对气候变化的本质反馈.     

花岗岩颗粒流模型循环压缩作用下裂纹特征分析

为了分析花岗岩颗粒流模型循环作用下的裂纹特征，基于花岗岩单轴压缩试验得到的应力应变曲线，完成了PFC3D数值试验的参数标定，探讨了不同循环次数下数值试件内部裂纹数目、分布和角度的变化规律。研究结果表明:平行黏结模型能够正确表达花岗岩的主要力学性质；在数值试验加载至破坏过程中，裂纹数目以应力应变曲线峰值点为分界，峰后阶段产生的裂纹数占总裂纹数的60%~90%;张剪裂纹最初产生于试件两端，随着加载进行，裂纹向着试件中部发展贯通，最终形成宏观剪切破坏带；剪切裂纹的角度分布方向明显，与轴向加载方向相同；张拉裂纹角度分布则在轴向加载方向和水平方向上略显集中。研究结果可为矿山安全回采矿柱提供依据。     

Evaluating weather effects on interannual variation in net ecosystem productivity of a coastal temperate forest landscape: A model intercomparison

Forest productivity is strongly affected by seasonal weather patterns and by natural or anthropogenic disturbances. However weather effects on forest productivity are not currently represented in inventory-based models such as CBM-CFS3 used in national forest C accounting programs. To evaluate different approaches to modelling these effects, a model intercomparison was conducted among CBM-CFS3 and four process models (ecosys, CN-CLASS, Can-IBIS and 3PG) over a 2500 ha landscape in the Oyster River (OR) area of British Columbia, Canada. The process models used local weather data to simulate net primary productivity (NPP), net ecosystem productivity (NEP) and net biome productivity (NBP) from 1920 to 2005. Other inputs used by the process and inventory models were generated from soil, land cover and disturbance records. During a period of intense disturbance from 1928 to 1943, simulated NBP diverged considerably among the models. This divergence was attributed to differences among models in the sizes of detrital and humus C stocks in different soil layers to which a uniform set of soil C transformation coefficients was applied during disturbances. After the disturbance period, divergence in modelled NBP among models was much smaller, and attributed mainly to differences in simulated NPP caused by different approaches to modelling weather effects on productivity. In spite of these differences, age-detrended variation in annual NPP and NEP of closed canopy forest stands was negatively correlated with mean daily maximum air temperature during July-September (T_amax) in all process models (R² = 0.4-0.6), indicating that these correlations were robust. The negative correlation between T_amax and NEP was attributed to different processes in different models, which were tested by comparing CO₂ fluxes from these models with those measured by eddy covariance (EC) under contrasting air temperatures (T_a). The general agreement in sensitivity of annual NPP to T_amax among the process models led to the development of a generalized algorithm for weather effects on NPP of coastal temperate coniferous forests for use in inventory-based models such as CBM-CFS3: NPP′ = NPP − 57.1 (T_amax − 18.6), where NPP and NPP′ are the current and temperature-adjusted annual NPP estimates from the inventory-based model, 18.6 is the long-term mean daily maximum air temperature during July-September, and T_amax is the mean value for the current year. Our analysis indicated that the sensitivity of NPP to T_amax was nonlinear, so that this algorithm should not be extrapolated beyond the conditions of this study. However the process-based methodology to estimate weather effects on NPP and NEP developed in this study is widely applicable to other forest types and may be adopted for other inventory based forest carbon cycle models.     

荒漠生态系统监测研究指标体系

新疆环境保护科学研究所自1984年接受“荒漠生态系统监测指标体系的观测研究”课题,在乌鲁木齐北部90km处的沙漠边缘建立了“准噶尔沙漠生态系统定位研究站”,自1987年正式开展了“荒漠生态系统定位观测研究”工作,从古尔班通沙漠中部至天山博格达峰中山带选定了沙漠、沙漠边缘、山前洪冲积扇、前山和中山带五个观测场,沙漠四季进行定位观测,同时,在站内进行多项目的连续观测,现集五年观测研究经验,结合中国科学院及国外研究站的先进经验,建立了荒漠生态系统指标体系。     

Ecological Linkages Between Headwaters and Downstream Ecosystems: Transport of Organic Matter,Invertebrates, and Wood Down Headwater Channels1

Abstract: Headwater streams make up a large proportion of the total length and watershed area of fluvial networks, and are partially characterized by the large volume of organic matter (large wood, detritus, and dissolved organic matter) and invertebrate inputs from the riparian forest, relative to stream size. Much of those inputs are exported to downstream reaches through time where they potentially subsidize river communities. The relative rates, timing, and conversion processes that carry inputs from small streams to downstream reaches are reasonably well quantified. For example, larger particles are converted to smaller particles, which are more easily exported. Also, dissolved organic matter and surface biofilms are converted to larger particles which can be more easily intercepted by consumers. However, the quality of these materials as it affects biological activity downstream is not well known, nor is the extent to which timing permits biological use of those particles. These ecological unknowns need to be resolved. Further, land uses may disrupt and diminish material transport to downstream reaches by removing sources (e.g., forest harvest), by affecting transport and decomposition processes (e.g., flow regulation, irrigation, changes in biotic communities), and by altering mechanisms of storage within headwaters (e.g., channelization). We present conceptual models of energy and nutrient fluxes that outline small stream processes and pathways important to downstream communities, and we identify informational gaps that, if filled, could significantly advance the understanding of linkages between headwater streams and larger rivers. The models, based on empirical evidence and best professional judgment, suggest that navigable waters are significantly influenced by headwater streams through hydrological and ecological connectivities, and land use can dramatically influence these natural connectivities, impacting downstream riverine ecosystems.     

森林生态系统的水文调节功能及生态学机制研究进展

森林水文调节功能是森林所实现的重要服务功能之一,可是由于森林资源被无节制的开采利用,导致人们不断遭受森林破环所带来的洪旱灾害。因此关于森林生态水文功能研究已成为生态学和水文学的研究重点之一。近年来,国内外对森林水文调节过程及其生态学机制进行了广泛深入的研究,所以文章从森林的水文过程出发,对林冠截留、树干流、凋落物层截留、林地水分涵养和蒸发蒸腾及其影响因子的国内外研究现状进行了归纳分析,研究认为林地各冠层均能够截留降雨,降低雨水动能,从而减少地表径流的产生和对地表的冲击;凋落物层能蓄留水分、抑制蒸散、减缓地表径流;而树干流改变降雨水平空间格局,影响水分入渗以及土壤水源涵养。森林结构复杂,明显改变了降雨分配过程,而森林水文过程及调节功能又受到森林结构的制约,因此定量定性探讨森林生态系统的结构、过程与水文调节功能之间关系,是未来森林生态水文功能研究的重点。     

近20年我国生态补偿研究进展与实践模式

本研究通过对20年来我国生态补偿相关文献的发文数量、重要文献等进行统计,采用文献检索和文献计量等方法,分析我国在生态补偿研究区域、研究领域、关键环节等方面的研究趋势,并基于政策变迁视角,从政策的制定思路、政策文本形式以及政策执行主体等维度来探究我国生态补偿20年政策发展历程,提炼出具有中国特色的生态补偿模式的形成过程。结果显示,热点领域和热点区域研究直接受政策导向影响,区域重大战略催生区域生态补偿研究呈井喷式增长,生态补偿政策实践力度大、范围广、领域多,制度设计从分散体现走向精准聚焦,补偿领域从单点起步走向全面布局,补偿模式由自上而下走向多元参与。随着我国生态文明建设迈入新征程,展望生态补偿未来改革和创新路径,建议围绕“全面”“综合”“多元”“民生”等核心关键词,探索基于多学科交叉的创新性研究,将生态补偿的研究进一步与制度创新、技术创新等相结合,以法制化、多元化、市场化和信息化为核心,推动生态补偿向更加立体、更加纵深和更加系统的方向发展。     

2018年3月两会期间北京重污染过程边界层气象的演变分析

为研究北京冬季重污染过程的污染特征及成因,采用边界层风场、温/湿场和气溶胶垂直探测等雷达综合遥测手段,对2018年3月北京两会期间的一次典型重污染过程,从边界层气象要素演变进行综合研究.结果表明:①整个污染过程历时7 d,轻度以上污染时数达118 h（占污染过程总小时数的69.8%）,严重污染时数达16 h（占污染过程总小时数的9.5%）,ρ（PM_2.5）最高达333.5 μg/m3.②从气溶胶的垂直空间演变来看,重污染天气的形成,除受本地源排放积累的影响外,还存在北京南部和东部的外部污染传输.贴地或上部逆温的稳定温度层结基本上对应ρ（PM_2.5）的累积过程,其中,重污染时段逆温维持达68 h,逆温层厚度为500~1 100 m,最大平均逆温强度为0.6℃/（100 m）.大气边界层高度偏低（积累过程白天在1 000 m以下,夜间只有300~500 m）,导致污染物持续积累.整个污染过程中,高湿时段引起PM_2.5吸湿增长和转化加重了污染程度;近地层持续小风导致污染积累;西南、东或东南方向大风层（10 m/s左右）向低空下探,有利于污染的缓解;强西北风或北风作用,使污染得以清除.研究显示,污染过程与边界层气象要素的演变密切相关.      

御临河流域河流湿地生态系统服务价值评价

御临河流域河流湿地具有非常重要的生态服务功能,包括直接使用价值和间接使用价值。直接使用价值有物质生产功能、水资源服务、旅游休闲功能、科研文化功能等,间接使用价值包括气体调节功能、水分调蓄功能及河岸带湿地污染净化功能的价值等。本研究采用市场价值法、碳税法、影子工程法、类比法及旅行费用法对御临河流域河流湿地生态系统服务价值进行了初步估算,其生态系统服务总价值为4.39亿元人民币,是2000年该流域GDP的28.52%。研究结果表明,御临河流域河流湿地生态系统的服务价值是不容忽视的。在进行流域规划管理时必须重视自然生态系统的潜在价值,才能保证流域生态系统的健康及可持续发展。