Dryland Ecosystems (dryland + ecosystem)

Distribution by Scientific Domains

Selected Abstracts

Toward an improved legislative framework for China's land degradation control

Zhou Ke
Abstract The Chinese government has recently been attaching increasing importance to the application of effective legal tools to tackle land degradation (LD) issues. Based on the concept of sustainable development, China began developing and reaping the benefits of environmental and natural resources legislation including LD control regulations in the 1990s. In the past three years, some central-western provinces in China have been implementing a "People's Republic of China/Global Environment Facility (PRC/GEF) Partnership on LD Control of Dryland Ecosystems", which is based on an integrated ecosystem management (IEM) approach. IEM is designed to achieve a balanced, scientific and participatory approach to natural resources management, which creates the potential to improve the quality of Chinese environmental law and policy procedures. The paper studies the existing Chinese national laws and regulations pertinent to LD control within 9 areas covering land, desertification, soil erosion, grassland, forest, water, agriculture, wild animals and plants, and environment protection in detail, against IEM principles and basic legal elements. The main objective is to identify problems and provide feasible solutions and recommendations for the improvement of the existing laws and regulations. The authors conclude that the development of an improved national legislative framework is essential if LD control is to be successfully achieved. The paper is partly based on Component 1 , Improving Policies, Laws and Regulations for Land Degradation Control under PRC/GEF Partnership on Land Degradation in Dryland Ecosystems (TA 4357). [source]

Predicting the unexpected: using a qualitative model of a New Zealand dryland ecosystem to anticipate pest management outcomes

Abstract Pest management is expensive and there is often uncertainty about the benefits for the resources being protected. There can also be unintended consequences for other parts of the ecosystem, especially in complex food webs. In making decisions managers generally have to rely on qualitative information collected in a piecemeal fashion. A method to assist decision making is a qualitative modelling approach using fuzzy cognitive maps, a directed graphical model related to neural networks that can take account of interactions between pests and conservation assets in complex food webs. Using all available information on relationships between native and exotic resources and consumers, we generated hypotheses about potential consequences of single-species and multi-species pest control on the long-term equilibrium abundances of other biotic components of an ecosystem. We applied the model to a dryland ecosystem in New Zealand because we had good information on its trophic structure, but the information on the strength of species interactions was imprecise. Our model suggested that pest control is unlikely to significantly boost native invertebrates and lizards in this ecosystem, suggesting that other forms of management may be required for these groups. Most of the pest control regimes tested resulted in greater abundances of at least one other pest species, which could potentially lead to other management problems. Some of the predictions were unexpected, such as more birds resulting from possum and mouse control. We also modelled the effects of an increase in invasive rabbits, which led to unexpected declines of stoats, weasels, mice and possums. These unexpected outcomes resulted from complex indirect pathways in the food web. Fuzzy cognitive maps allow rapid construction of prototype models of complex food webs using a wide range of data and expert opinion. Their utility lies in providing direction for future monitoring efforts and generating hypotheses that can be tested with field experiments. [source]

Woody plants modulate the temporal dynamics of soil moisture in a semi-arid mesquite savanna,

ECOHYDROLOGY, Issue 1 2010
Daniel L. Potts
Abstract Climate variability and human activities interact to increase the abundance of woody plants in arid and semi-arid ecosystems worldwide. How woody plants interact with rainfall to influence patterns of soil moisture through time, at different depths in the soil profile and between neighboring landscape patches is poorly known. In a semi-arid mesquite savanna, we deployed a paired array of sensors beneath a mesquite canopy and in an adjacent open area to measure volumetric soil water content (,) every 30 min at several depths between 2004 and 2007. In addition, to quantify temporally dynamic variation in soil moisture between the two microsites and across soil depths we analysed , time-series using fast Fourier transforms (FFT). FFT analyses were consistent with the prediction that by reducing evaporative losses through shade and reducing rainfall inputs through canopy interception of small rainfall events, the mesquite canopy was associated with a decline in high-frequency (hour-to-hour and day-to-day) variation in shallow ,. Finally, we found that, in both microsites, high-frequency , variation declined with increasing soil depth as the influence of evaporative losses and inputs associated with smaller rainfall events declined. In this case, we argue that the buffering of shallow soil moisture against high-frequency variations can enhance nutrient cycling and alter the carbon cycle in dryland ecosystems. Copyright 2009 John Wiley & Sons, Ltd. [source]

Responses of dryland soil respiration and soil carbon pool size to abrupt vs. gradual and individual vs. combined changes in soil temperature, precipitation, and atmospheric [CO2]: a simulation analysis

Abstract With the large extent and great amount of soil carbon (C) storage, drylands play an important role in terrestrial C balance and feedbacks to climate change. Yet, how dryland soils respond to gradual and concomitant changes in multiple global change drivers [e.g., temperature (Ts), precipitation (Ppt), and atmospheric [CO2] (CO2)] has rarely been studied. We used a process-based ecosystem model patch arid land simulator to simulate dryland soil respiration (Rs) and C pool size (Cs) changes to abrupt vs. gradual and single vs. combined alterations in Ts, Ppt and CO2 at multiple treatment levels. Results showed that abrupt perturbations generally resulted in larger Rs and had longer differentiated impacts than did gradual perturbations. Rs was stimulated by increases in Ts, Ppt, and CO2 in a nonlinear fashion (e.g., parabolically or asymptotically) but suppressed by Ppt reduction. Warming mainly stimulated heterotrophic Rs (i.e., Rh) whereas Ppt and CO2 influenced autotrophic Rs (i.e., Ra). The combined effects of warming, Ppt, and CO2 were nonadditive of primary single-factor effects as a result of substantial interactions among these factors. Warming amplified the effects of both Ppt addition and CO2 elevation whereas Ppt addition and CO2 elevation counteracted with each other. Precipitation reduction either magnified or suppressed warming and CO2 effects, depending on the magnitude of factor's alteration and the components of Rs (Ra or Rh) being examined. Overall, Ppt had dominant influence on dryland Rs and Cs over Ts and CO2. Increasing Ppt individually or in combination with Ts and CO2 benefited soil C sequestration. We therefore suggested that global change experimental studies for dryland ecosystems should focus more on the effects of precipitation regime changes and the combined effects of Ppt with other global change factors (e.g., Ts, CO2, and N deposition). [source]

Livelihood diversification and implications on dryland resources of central Tanzania

Emma T. Liwenga
Abstract The concern over sustainable livelihoods in African drylands is an issue that has received considerable attention from researchers and policy makers alike. Over the past two decades African rural areas have undergone rapid changes, whereby, rural income diversification has become the most salient feature. With a particular focus on dryland ecosystems, among the major challenges facing communities in these areas is recurrent drought leading to conditions of food insecurity. This paper draws on experience on coping mechanisms for food insecurity from an agro-pastoral community in Mvumi, located in the semiarid areas of central Tanzania. An understanding of livelihoods of people in this area has involved examining how communities have managed to adjust their livelihood in the midst of challenges resulting not only from drought but also from various forces such as socio,economic, political and ecological factors. It has been found out that, despite profound food crisis in this area, people are not always desperate and that there are possibilities for realizing some hidden potentials of dryland resources for livelihood diversification. The issue of sustainable natural resource management in such areas is, however, questionable because of some adverse environmental effects associated with some of the coping mechanisms. [source]

Can isotropy vs. anisotropy in the spatial association of plant species reveal physical vs. biotic facilitation?

Peter Haase
In dryland ecosystems and other harsh environments, a large part of the vegetation is often clustered, appearing as ,islands'. If ,independent' species, usually colonizers, can be distinguished from species which are ,dependent' on the presence of the colonizing species for successful establishment and/or persistence, the type of spatial pattern of the association - isotropic (spatially symmetric) or anisotropic (spatially asymmetric) - can give information on the underlying environmental factors driving the process of association. Modified spatial pattern analysis based on Ripley's K -function can be applied to bivariate clustered patterns by cardinal direction in order to detect possible anisotropy in the pattern of association. The method was applied to mapped distribution patterns of two types of semi-arid shrubland in southeastern Spain. In shrubland of Retama sphaerocarpa, low shrubs of Artemisia barrelieri were significantly clustered under the canopy of the Retama shrubs in all four cardinal directions, suggesting an isotropic facilitation effect. In low shrubland dominated by Anthyllis cytisoides and Artemisia barrelieri, Anthyllis shrubs occurred more frequently than expected on the eastern side (and downslope) of an Artemisia shrub. The possible environmental factors driving the two association patterns are discussed and recommendations for further applications of the analytical method are given. [source]