土壤-植被-大气连续体中的尺度转换问题

土壤-植被-大气间的相互作用强度高度地依赖于时空尺度。其中,反馈机制贯穿于土壤-植被-大气相互作用的始终。在各个时空尺度中,多因子交互作用,尺度不同起主导作用的过程和控制因子可能有所不同,从而增加了土壤-植被-大气连续体尺度转换研究的难度。从空间和时间尺度上总结了近年来有关学者对尺度转换及反馈机制在模拟中如何应用的研究结果,并在该基础上指出了当前合理描述土壤-植被-大气连续体区域尺度系统行为需要关注的问题和挑战。     

Weathering and vegetation effects in early stages of soil formation

Bedrock surfaces in the Ouachita Mountains, Arkansas, exposed by spillway construction and which had not previously been subjected to surface weathering environments, developed 15–20 cm thick soil covers in less than three decades. All open bedrock joints showed evidence of weathering and biological activity. Rock surfaces and fragments also showed evidence of significant weathering alteration. The results suggest a soil production function whereby weathering and increases in thickness are initially rapid. The rapid initial rate (5 to 10 mm year^− 1) is facilitated by a weathering-favorable regional climate, local topography favoring moisture and sediment accumulation, and aggressive vegetation colonization. The ages of the trees on the bedrock benches suggests that a short period (< 10 years) of pedogenic site preparation is necessary before trees can become established. Initial chemical weathering within newly-exposed rock fractures in resistant sandstone strata and chemical weathering of weak shale layers, coupled with accumulation of organic and mineral debris in fractures and microtopographic depressions facilitates plant establishment, which accelerates local weathering rates.     

Strategic Adaptive Management in freshwater protected areas and their rivers

Aquatic ecosystems are connected over large spatial scales, have varied drivers, strong and often conflicting societal interests and interacting management processes. Many of the world’s protected areas (>100,000, ∼12% of land) include freshwater ecosystems, some specifically declared for freshwater protection, but often supplied by rivers outside their protected boundaries. Such complex socio-ecological systems have considerable challenges. We report on Strategic Adaptive Management (SAM), a management framework that should be implemented, irrespective of resourcing, in protected areas of any river system, ranging from heavily managed or regulated through to pristine rivers. We briefly outline the four stages of the SAM process for aquatic protected areas and present three case studies from South Africa and Australia in different stages of SAM implementation. Progress is incremental, reflecting gaps, problems, and socio-ecological dynamism. Real-world implementation usually means such management is passive although experimentation with environmental flows remains possible. While maturity in SAM is incremental over years or decades, it can and should be applied even if environmental problems are urgent and contentious. The stages of SAM should produce an agreed vision and/or mission among stakeholders, with an appropriate hierarchy of objectives that determines indicators to be measured, allowing ongoing reflection, learning and adaptation. There is no panacea for achieving aquatic conservation, but Strategic Adaptive Management offers hope with its interlinked processes for navigating complexity and learning. SAM in freshwater conservation is progressing because of the imperative for sustainability, history of interaction between scientists and managers and the need for transdisciplinary governance of rivers.