Evaluation of snow models in terrestrial biosphere models using ground observation and satellite data: impact on terrestrial ecosystem processes

Snow is important for water management, and an important component of the terrestrial biosphere and climate system. In this study, the snow models included in the Biome‐BGC and Terrestrial Observation and Prediction System (TOPS) terrestrial biosphere models are compared against ground and satellite observations over the Columbia River Basin in the US and Canada and the impacts of differences in snow models on simulated terrestrial ecosystem processes are analysed. First, a point‐based comparison of ground observations against model and satellite estimates of snow dynamics are conducted. Next, model and satellite snow estimates for the entire Columbia River Basin are compared. Then, using two different TOPS simulations, the default TOPS model (TOPS with TOPS snow model) and the TOPS model with the Biome‐BGC snow model, the impacts of snow model selection on runoff and gross primary production (GPP) are investigated. TOPS snow model predictions were consistent with ground and satellite estimates of seasonal and interannual variations in snow cover, snow water equivalent, and snow season length; however, in the Biome‐BGC snow model, the snow pack melted too early, leading to extensive underpredictions of snow season length and snow covered area. These biases led to earlier simulated peak runoff and reductions in summer GPP, underscoring the need for accurate snow models within terrestrial ecosystem models. Copyright © 2007 John Wiley & Sons, Ltd.     

全球生态系统的状况与趋势

简要介绍了千年生态系统评估（MA）项目状况与趋势工作组的报告《生态系统与人类福祉：现状与趋势》中的第3部分，即“对提供生态系统服务的各类系统的评估”。评估结果表明，在20世纪的后50年，全球生态系统的变化幅度和速度皆超过了人类历史上有记录的任何一个相等时间段的情况，目前人类活动实际上已经显著地改变了地球上的所有生态系统。这些变化主要表现在：① 大约1/4的地球陆地表层已经转变为垦殖系统，而且在1950年之后的30年中，转变为农田的土地面积比1700—1850年这150年间转变的总和还要多；②全球大多数的重要流域，由于水资源利用造成的栖息地丧失与破碎化，以及由于养分、沉积物、盐分及有毒物质造成的污染，已经显著地破坏了河流、湖泊和盐水沼泽等湿地生态系统的功能与生物多样性；③ 旱区系统存在着水资源匮乏、过度垦殖、过度放牧和过度砍伐树木等问题，生态状况尤其令人担忧；④ 栖息地的丧失与破碎化、过度开发、污染以及气候变化，已经对海滨系统造成了严重的生态威胁；⑤ 不可持续的农业开发模式，已经严重地破坏了热带森林生态系统的结构与功能。     

塔里木河流域生态系统健康评价指标体系的构建

流域生态系统健康评价研究是目前生态学研究的一个新概念、新问题,旨在探讨在人类强烈活动干扰下遭忖受严重污染与退化的流域生态系统的健康问题,生态系统健康是人类与环境间的相互协调关系及实现生态可持续发展的重要基础.依据野外调查资料、遥感影像和社会经济数据,分析表明：水资源是决定塔里木河流域生态系统健康与否的关键因素,人类对水资源的不合理开发利用是导致本流域生态环境恶化的根本原因.因此从水资源、生物多样性、生态系统的弹性和经济社会几方面的健康出发,选取相应的一系列指标,构建了塔里木河流域生态系统健康评价指标体系,并确立了各指标健康程度的度量标准.从而为本流域的生态环境管理提供可参考的理论基础.     

基于物元模型的城市生态健康评价

基于生态系统自身的特点、人类在生态系统中的影响和城市生态系统的内涵,建立了城市生态系统健康评价指标体系,确定了城市生态系统健康评价标准.针对传统评价方法中量化指标丢失信息的情况,提出应用物元模型进行城市生态系统健康评价.利用所建立的模型,以大连城市生态系统为例进行城市生态系统健康状况分析.用指数超标法确定了指标的权重,建立了评价物元、节域和经典域矩阵,通过计算关联函数确定了评定等级.评价结果表明:2000～2003年大连城市生态系统一直处于健康的发展状态,具有良好的可持续发展趋势,但健康程度并不高,部分指标有所恶化.     

优质高产天宝蕉的农业地质环境分析

在天宝蕉产区的农业地质背景和天宝蕉品质分析的基础上,对二者的相互关系进行了研究,得出优质天宝蕉产区的主要农业地质特征是:(1)天宝香蕉的优质区主要分布在九龙江Ⅰ级阶地和红土台地上;(2)优质天宝蕉的成土母质为第四系全新统冲洪积层和第四系残坡积层;(3)优质天宝蕉种植区的土壤主要为灰泥田和赤砂土;(4)天宝蕉优质区成土母质富集元素最多,土壤全量中Na2O、MgO、CaO的含量较高,土壤有效态含量中Cu、Zn元素的含量较高;(5)天宝香蕉优质区的水位埋深较浅,土壤的持水透水能力适中。同时提出了对非优质香蕉的种植区补充土壤营养元素、改良土质和增加蕉园的灌溉等土壤改良建议。     

Sustainable fresh water resources management in northern Kuwait—A remote sensing view from Raudatain basin

The paper presents time and cost effective remote sensing technology to estimate recharge potential of fresh water shallow aquifers for their sustainable management of water resources in arid ecosystem. Precipitation measurement of Raudatain basin in Kuwait from TRMM data has been made and integrated with geological, geomorphological and hyrological data, to estimate the recharge potential of this basin. The total precipitation in the basin is estimated at 334 MCM for the year 2003. The initial losses are estimated at 78.43% and the transmission loss at 14.866% of the net precipitation.For sustainable management of the ground water resources, recharge wells have been proposed in the higher order streams to augment the Raudatain aquifer in Kuwait. If the available quantity of precipitation can be successfully utilized, it will reduce considerable pressure on desalination, which leads to increased salinity at the coast in Arabian Gulf.     

Spatial patterns of terrestrial net ecosystem productivity in China during 1981–2000

As the third largest country in the world, China has highly variable environmental condition and ecological pattern in both space and time. Quantification of the spatial-temporal pattern and dynamic of terrestrial ecosystem carbon cycle in China is of great significance to regional and global carbon budget. In this study, we used a high-resolution climate database and an improved ecosystem process-based model to quantify spatio-temporal pattern and dynamic of net ecosystem productivity (NEP) in China and its responses to climate change during 1981 to 2000. The results showed that NEP increased from north to south and from northeast to southwest. Positive NEP (carbon sinks) occurred in the west of Southwest China, southeastern Tibet, Sanjiang Plain, Da Hinggan Mountains and the mid-west of North China. Negative NEP (carbon sources) were mainly found in Central China, the south of Southwest China, the north of Xinjiang, west and north of Inner Mongolia, and parts of North China. From the 1980s to 1990s, the increasing trend of NEP occurred in the middle of Northeast China Plain and the Loess Plateau and decreasing trends mainly occurred in a greater part of Central China. In the study period, natural forests had minimal carbon uptake, while grassland and shrublands accounted for nearly three fourths of the total carbon terrestrial uptakes in China during 1981–2000. Supported by the Ministry of Science and Technology of China (G2002CB412507), the Major Program of the National Natural Science Foundation of China (Grant No.30590384), the “Hundred Talent” Program of the Chinese Academy of Sciences, and K C WONE Education Foundation     

朔州市近45 a气温变化及对农业生产的影响

利用1961～2005年朔州市6个气象观测站的气温资料,用气候倾向率、滑动平均等方法,对朔州市近45a气温变化特征作了统计分析。结果表明:45a来,朔州市的年平均气温、年平均最高气温、年平均最低气温自20世纪70年代中期以来呈上升趋势,平均气温以0.43℃/10a的速度上升;平均最低气温升温幅度明显高于平均最高气温;进入20世纪90年代后,这种趋势有所加快,尤其以冬季升温最为明显。1987年以来朔州相继出现了15个暖冬,较强的暖冬年份出现在1995年以后。气候变暖对农业生产互有利弊。如何趋利避害,确保当地农业高产优产是需要进一步研究的问题。     

A Conceptual Framework for Enhancing the Utility of Rainfall Hazard Forecasts for Agriculture in Marginal Environments

Semi-arid and dry sub-humid areas (especially in the tropics) are characterized by high inter-annual and intra-seasonal rainfall variability. Agriculture, which employs the bulk of the rapidly increasing populations, is largely rain-fed, low-input based and highly resource dependent. Recent spates of drought have, therefore, exacerbated the now-too-familiar specter of famine and starvation in these areas with glaring examples being the recurring episodes in sub-Saharan Africa since the great Sahel drought of 1969–1973. A great need for accurate and timely hazard forecast products in aid of agriculture thus exists.Several schemes are currently employed by various agencies around the globe in this direction. There does remain, however, a gap between product provision and user expectations. This paper examines this gap suggesting a five-point framework within which it can be addressed as an action agenda for the climate science community. The paper posits that changes are possible to existing methodologies (related to three of these points), which, within the context of current science, can greatly enhance the utility of forecast products for agriculture in marginal areas. The remaining two points have, however, been identified as requiring additional applied research and necessary pointers for addressing these issues are provided. First is the need for appropriate impact-related indicators for intra-seasonal and interannual rainfall variability that are easy to compute, amenable to forecasting and follow closely the experiences of farmers in marginal areas. The second is a consideration of appropriate forecast information formatting and communication medium that guarantee effective feedback between forecast producers and users. Specific examples of the status quo and of work currently underway are cited from southern Africa – a region currently attracting international attention as a result of recent droughts and the threat of famine.     

Impacts of land-use and climate changes on ecosystem productivity and carbon cycle in the cropping-grazing transitional zone in China

Terrestrial ecosystems are both a carbon source and sink, therefore play an important role in the global carbon cycle that act as a link of interactions between human activities and climate changes[1,2]. Climate change impacts ecosystem carbon cycle through af- fecting biological processes, e.g. plant photosynthesis, respiration, and soil carbon decomposition. Land-use change directly modifies the distribution and structure of terrestrial ecosystems and hence the carbon storage and fluxes. Usi…