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Abstract: In arid lands, the shifts in dominant plant types from grasses to shrubs can significantly alter the ecosystem function and biogeochemistry cycles. However, the magnitude of these alterations and its inherent mechanisms are still poorly understood. In this study, we measured soil respiration and NPP over two growing seasons in 2006–2007 in the co-occurring perennial grass and desert shrub ecosystems at the Ordos Plateau of Inner Mongolia, China. Over the two growing seasons, the desert shrub site presented higher aboveground biomass and NPP while lower soil respiration relative to the grass site (p < 0.05). In this paper, we can not determine that whether vegetation conversion or soil texture change drive the site difference in soil respiration because we did not control for soil texture. We suppose that the site difference in pulse response of soil respiration might play an essential role in regulating this soil respiration gap. In all the growing seasons, surface soil moisture (0–10 cm) was identified as the major driver of soil respiration at both sites. Compared to the linear soil moisture model, the integrated model incorporating both surface soil moisture and air temperature was performed better in predicting the dynamics of soil respiration. [Copyright &y& Elsevier]

Abstract: This paper presents a multilayered ecosystem modelling approach that combines the simulation of the biogeochemistry of a coastal ecosystem with the simulation of the main forcing functions, such as catchment loading and aquaculture activities. This approach was developed as a tool for sustainable management of coastal ecosystems. A key feature is to simulate management scenarios that account for changes in multiple uses and enable assessment of cumulative impacts of coastal activities. The model was applied to a coastal zone in China with large aquaculture production and multiple catchment uses, and where management efforts to improve water quality are under way. Development scenarios designed in conjunction with local managers and aquaculture producers include the reduction of fish cages and treatment of wastewater. Despite the reduction in nutrient loading simulated in three different scenarios, inorganic nutrient concentrations in the bay were predicted to exceed the thresholds for poor quality defined by Chinese seawater quality legislation. For all scenarios there is still a Moderate High to High nutrient loading from the catchment, so further reductions might be enacted, together with additional decreases in fish cage culture. The model predicts that overall, shellfish production decreases by 10%–28% using any of these development scenarios, principally because shellfish growth is being sustained by the substances to be reduced for improvement of water quality. The model outcomes indicate that this may be counteracted by zoning of shellfish aquaculture at the ecosystem level in order to optimize trade-offs between productivity and environmental effects. The present case study exemplifies the value of multilayered ecosystem modelling as a tool for Integrated Coastal Zone Management and for the adoption of ecosystem approaches for marine resource management. This modelling approach can be applied worldwide, and may be particularly useful for the application of coastal management regulation, for instance in the implementation of the European Marine Strategy Framework Directive. [Copyright &y& Elsevier]