Soil moisture‐based drought monitoring at different time scales: a case study for the U.S. Great Plains

Short‐term agricultural drought and longer term hydrological drought have important ecological and socioeconomic impacts. Soil moisture monitoring networks have potential to assist in the quantification of drought conditions because soil moisture changes are mostly due to precipitation and evapotranspiration, the two dominant water balance components in most areas. In this study, the Palmer approach to calculating a drought index was combined with a soil water content‐based moisture anomaly calculation. A drought lag time parameter was introduced to quantify the time between the start of a moisture anomaly and the onset of drought. The methodology was applied to four shortgrass prairie sites along a North‐South transect in the U.S. Great Plains with an 18‐year soil moisture record. Short time lags led to high periodicity of the resulting drought index, appropriate for assessing short‐term drought conditions at the field scale (agricultural drought). Conversely, long time lags led to low periodicity of the drought index, being more indicative of long‐term drought conditions at the watershed or basin scale (hydrological drought). The influence of daily, weekly, and monthly time steps on the drought index was examined and found to be marginal. The drought index calculated with a short drought lag time showed evidence of being normally distributed. A longer data record is needed to assess the statistical distribution of the drought index for longer drought lag times.     

藏北高寒草地生态系统服务价值评估

藏北高寒草地是我国重要的畜牧业生产基地和生态安全屏障.然而,高寒草地退化使生态系统服务功能减弱,生态服务价值降低,不仅严重影响了藏北高原畜牧业生产和牧民生活,而且直接威胁到区域生态安全及东亚水资源安全.因此,本研究在综合考虑草地生态系统的地域差异性、空间异质性和区域经济发展水平差异性的基础上,选择了贡献率较高的12项指标,对藏北那曲不同类型和不同退化程度高寒草地的生态服务价值进行评估.结果表明,藏北那曲地区高寒草地生态系统的年总生态服务价值为1199.07亿元,其中,高寒草原、高寒荒漠、高寒荒漠草原和高寒草甸提供的生态服务价值分别占总生态服务价值的62.9%、1.5%、8.0%和28.1%.从退化程度上看,未退化、轻度退化、中度退化和严重退化草地提供的生态服务价值分别占总生态服务价值的54.9%、29.3%、11.0%和4.8%.     

Sustainable rangeland management using a multi-fuzzy model: how to deal with heterogeneous experts' knowledge

While fuzzy specialists commonly use homogeneous experts' knowledge to construct fuzzy models, it is much more difficult to deal with knowledge elicited from a heterogeneous group of experts. This issue is exemplified in the area of sustainable rangeland management (SRM). One way to deal with the diversity of opinions is to develop a fuzzy system for all experts and to combine all these, the so-called primary systems, into one multi-fuzzy model. To derive each of the primary fuzzy systems, several semi-structured interviews were held in three different areas of the Fars province in Southwest Iran using the knowledge of a group of administrative experts. To obtain the final output of the multi-fuzzy model, we applied different 'voting' methods. The first method simply uses the arithmetic average of the primary outputs as the final output of the multi-fuzzy model. This final output represents an estimation of the right rate of stocking (RRS). We also propose other (un)supervised voting methods. Most importantly, by harmonising the primary outputs such that outliers get less emphasis, we introduce an unsupervised voting method for calculating a weighted estimate of the RRS. This harmonising method is expected to provide a new useful tool for policymakers dealing with heterogenity in experts' opinions: it is especially useful where limited field data are available and one is forced to rely on experts' knowledge only. By constructing the three fuzzy models based on the elicitation of heterogeneous experts' knowledge, our study shows the multidimensional vaguenesses that exist in SRM. Finally, by comparing the final RRS with its common values, this study strongly points to the existence of overgrazing in pastures in the three regions of the Fars province in Southwest Iran.     

Water Development Strategy as a Driving Force for Sustained Rangeland Management by Local Communities in Sub-Saharan Africa

Water is the major food component for the maintenance of animals. Although Africa is endowed with diverse agricultural environments, the survival of animals in Sahelian and sub-Sahelian Africa is threatened by the lack of water. Animals need water as an essential nutrient, a component of the body, and for conductive or evaporative cooling. Water needs are met mainly through drinking free water and to a lesser extent by utilising water that forms part of the feed. However during the long dry season, surface water resources dwindle and the water content of available forage decreases, thereby increasing the animals’ demand for water. Consequently animals have to walk for long distances to obtain adequate forage and water, which in turn raises the demand for these resources. Water can be used to direct and regulate rangeland management in this open access environment, to maintain range resources and to improve their quality. Water development, which takes into consideration usable forage, despite some intra- or inter-annual variability, plays an important role and its spatial distribution will affect the grazing intensity of forage resources. Sound water development and management strategies integrating local communities in the decision-making will set up a firm basis for sustained range management in the free and open access environment of sub-Saharan Africa where lack of financial input, social and cultural habits and above all the environmental condition do not permit large scale fencing as in other parts of the world.     

Ranch Ownership Change and New Approaches to Water Resource Management in Southwestern Montana: Implications for Fisheries1

Abstract:  This article reports on a survey of ranch owners in high amenity areas in southwestern Montana that have experienced marked ownership change over the last two decades. Specifically, we focus on findings from a set of questions targeting water resource and riparian area management. After reviewing the results, we consider how new owners may be managing water resources differently than longtime owners and what the ecological implications of this shift in management might be for Montana’s prized wild fisheries. Uses more closely associated with new owners than with longtime owners include water reallocation to instream uses, aquatic and riparian ecosystem restoration, and fish pond construction. These uses have both positive and negative impacts on the region’s fisheries. Our findings suggest that current laws and institutions guiding the management of water resources and the aquatic and riparian ecosystems they support may not be adequate to address emerging conservation opportunities and challenges.     

封育措施对半干旱沙地草场植被群落特征及地上生物量的影响

随着干早区草场非平衡态理论的提出和发展，退化草场封育的时间、方式与草场恢复间的关系已成为目前研究的主要课题之一：作者选择完全封育、季节封育和未封育3种措施进行对半干早沙地草场的植被特征及其生物量进行比较研究，结果表明，在封育处理的年份中，不同封育措施（放牧压力）是决定植被差异的主要因子。完全封育区和季节封育区植物以一年生草本为主，在植物种数量、生物多样性上差异并不显著，未封育区植被则以多年生草本为主，且Simpson和Shannon多样性指数与前两者差异均显著；完全封育并未导致一些牲畜喜食植物种的完全消失，但一些饲用价值差的植物如平卧碱蓬等大量出现在完全封育的群落中，同时旱生和强旱生植物的比例明显增加。尽管3种措施地上部分总生物量差异并不显著，但各群落中主要植物种的地上部分生物量则存在这一定的差异，从3种措施植被的饲用价值来看，季节封育区植被的饲用价值较高，表明季节封育可以促进并提高草场的放牧利用价值。     

基于RUE的不同草地类生态评价研究——以河西走廊为例

选择降水利用效率（RUE）作为评价指标,对河西走廊代表性草地类--温性荒漠、高寒草甸、温性草原进行生态评价研究。通过植被指数提取、降水Co-Kriging插值、图层叠加,得到河西走廊区域2006-2010年的RUE(NDVI)、RUE(PVI)、RUE(TSAVI)数据,并与地上生物量进行相关分析,筛选出适合不同草地类的RUE作为该区域生态评价的指标。结果表明：1）温性荒漠区RUE(PVI)与草地生物量风干重正相关性最高（R²=0.879）,高寒草甸区RUE(NDVI)与草地生物量风干重的正相关性最高（R²=0.876）,温性草原区RUE(TSAVI)与草地生物量风干重的正相关性最高（R²=0.895）。2）温性荒漠区、温性草原区生态均处于退化过程,高寒草甸区处于恢复过程。研究认为选择合适的RUE值可作为不同草地类生态评价指标,并具有理论的可行性和实践的可靠性。     

不同产权制度下青藏高原地区草地资源使用的效率与公平性分析

论文基于四川省若尔盖牧区两个村落的田野调查,通过草地资源使用的效率和公平性指标,比较草场使用权全村共有和牧户私有这两种产权制度下的经济与社会效益。研究表明,在青藏高原牧区,草场使用权全村共有较牧户私有在资源使用的效率与公平性两个方面均能获得更好的表现。这是因为全村共有的使用权制度更契合当地的自然与社会实情,这包括草地资源时空差异大的自然条件、藏传佛教浸润下的文化氛围以及较强的社区自组织管理能力的社会背景。因此,建议我国在制定与推行草场使用权制度时,应考虑制度实施地的自然环境与社会文化等各方面背景因素,不能简单地在所有牧区强行推进一种产权制度。     

中国自然草地生态系统服务价值

文中参照Constaza等提出的方法,在对草地生态系统服务价格根据其生物量订正的基础上,逐项估计了各类草地生态系统的各项生态系统服务价值,得出全国草地生态系统每年的服务价值为14979×10⁸US＄。其中扰乱管理价值占1607%,水管理和水供应价值占1444%,侵蚀控制和沉积保存价值占908%,废物处理价值占4203%,授粉价值占783%,生物控制价值占72%,食物和原材料生产价值占2226%,娱乐和文化价值占578%,其它如气体管理价值、土壤形成价值和栖息地价值低于5%。受各类草地生物群落分布广度和单位面积生态服务功能强弱的综合影响,各类草地的生态服务价值贡献率有很大差异,其中,沼泽类对草地生态系统总服务价值的贡献率为5234%。温性草原类、热性草丛类、热性灌草丛类、低地草甸类和高寒草甸类对总服务价值的贡献分别在503%～774%之间,其余类型的草地生态服务价值贡献率在5%以下。