Assessing the vulnerability of riparian vegetation to invasion by Mimulus guttatus: relative importance of biotic and abiotic variables in determining species occurrence and abundance

Riparian habitats are particularly susceptible to invasion by non‐native plants. At present, attempts to build consensus as to what the primary drivers of plant invasion in riparian ecosystems might be is hindered by the absence of common standards for data collected on plant species (e.g. occurrence, or relative abundance). Mimulus guttatus L., a non‐native riparian plant species, was used as a model to determine how environmental drivers influence two aspects of invasibility: species occurrence and abundance (assessed in relation to three variables number of patches, patch area and number of stems per patch). Mimulus occurrence and abundance, together with 20 environmental variables, were surveyed in almost 700 contiguous 50‐m‐long riverbank segments within a catchment in north‐east Scotland. More than half of the segments had been colonized by Mimulus. Occurrence and number of patches responded to similar environmental gradients, particularly bare sediment, boulders, high soil moisture, short‐statured ruderal communities, and open canopies, and tended to be highest downstream where the river was widest. In contrast to occurrence and patch number, patch area and stem number per patch were higher in the upper reaches of the catchment and were positively associated with low tree canopy and vegetation dominated by light‐demanding species and smaller‐statured species. Patch area and stem number per patch were also positively related to grazing. This study has highlighted the importance of assessing more than one measure of invasion success (occurrence or patch number and either patch area or stem number per patch), as they are each determined by a different suite of environmental variables. Abiotic factors, such as sediment availability and presence of boulders, appeared to be the major determinants of occurrence and patch number, whereas biotic factors, such as interspecific competition and grazing, were more important ecological determinants underlying area and stem number per patch.     

山水林田湖草生态修复工程的社会-生态系统(SES)分析框架及应用——以浙江省钱塘江源头区域为例

“山水林田湖草生命共同体”是人与自然和谐共处的指导原则,也是人类实现可持续发展的有效实践路径。根据Ostrom提出的社会-生态系统（SES）框架,以浙江省钱塘江源头区域为研究区,构建集流域、陆地和人类活动为一体的社会-生态系统（SES）概念框架,为生态修复工程提供一个问题导向的分析策略。研究发现基于Ostrom构建的钱塘江源头区域山水林田湖草生态修复工程的SES框架,可以用来诊断关键问题、分析影响因素、设定行动情景和评估结果,从而形成完整的实施和解决问题策略。由诊断关键问题得出,该区域面临地质灾害多发、水土流失、环境污染、生物结构单一等多重问题,而人类活动如城市扩张、过度开发自然资源、污染物排放等则是造成社会-生态系统失衡的主要因素。通过行动情景设置将SES框架中涉及的影响因素、解决途径、评价标准、期望的成效以及反馈机制等进行梳理,对研究区的社会-生态系统进行全面分析。根据设立的评价体系对生态修复工程进行生态环境和社会经济效果的动态评估,并不断地根据评价结果进行修正以获得最佳的预期成效。该框架为解决钱塘江源头区域山水林田湖草生态修复工程所面临的问题提供了一个系统的解决方案,并可根据研究区的特点进行相应调整,是一个具有强适用性的社会-生态系统分析框架。     

Assessing the effects of land-use change on plant traits, communities and ecosystem functioning in grasslands: a standardized methodology and lessons from an application to 11 European sites

BACKGROUND AND AIMS: A standardized methodology to assess the impacts of land-use changes on vegetation and ecosystem functioning is presented. It assumes that species traits are central to these impacts, and is designed to be applicable in different historical, climatic contexts and local settings. Preliminary results are presented to show its applicability. METHODS: Eleven sites, representative of various types of land-use changes occurring in marginal agro-ecosystems across Europe and Israel, were selected. Climatic data were obtained at the site level; soil data, disturbance and nutrition indices were described at the plot level within sites. Sixteen traits describing plant stature, leaf characteristics and reproductive phase were recorded on the most abundant species of each treatment. These data were combined with species abundance to calculate trait values weighed by the abundance of species in the communities. The ecosystem properties selected were components of above-ground net primary productivity and decomposition of litter. KEY RESULTS: The wide variety of land-use systems that characterize marginal landscapes across Europe was reflected by the different disturbance indices, and were also reflected in soil and/or nutrient availability gradients. The trait toolkit allowed us to describe adequately the functional response of vegetation to land-use changes, but we suggest that some traits (vegetative plant height, stem dry matter content) should be omitted in studies involving mainly herbaceous species. Using the example of the relationship between leaf dry matter content and above-ground dead material, we demonstrate how the data collected may be used to analyse direct effects of climate and land use on ecosystem properties vs. indirect effects via changes in plant traits. CONCLUSIONS: This work shows the applicability of a set of protocols that can be widely applied to assess the impacts of global change drivers on species, communities and ecosystems.