羊啃食动力学模拟与内蒙古西部气候变化适应

 将定性分析、民主参与式评估和定量数值模拟方法结合起来,对阿拉善气候变化适应问题进行了简要评估并重点分析了土地退化、放牧和草原管理策略之间的关系。阿拉善主要的适应政策是禁牧和生态移民。禁牧后荒漠草原植被得到恢复,但移民增加了绿洲压力,过度开垦又造成周边土地沙化;过度抽取地下水致使水位下降并伴随咸水入侵和地表盐碱化。禁牧的另一个副作用是造成草原鼠害加重及火灾风险增加,生物多样性也呈现先升后降趋势。一些灌木因缺乏啃食出现退化迹象等,说明一定程度的啃食有利于维持草原生态平衡。因此,动物是草原生态系统不可或缺的成员之一。我们用一个包含动物啃食等的森林生态动力模式模拟了啃食动力学,结果表明,有限的放牧有利于草场更新并能充分利用草原资源;过度放牧导致草场退化并伴随羊群死亡。因此,需要将圈养和限制性放牧结合起来,制定可持续性适应政策。

Simulation of Goat and Sheep Grazing Dynamics and Climate Change Adaptation Strategies in West Inner Mongolia, China

This paper focus on climate change adaptation,land use management and grazing strategies in Alxa League,Inner Mongolia,China by use of social survey,statistical analysis and numerical modeling.Results suggest that the climate change adaptation must keep a balance between sustainable development of local economics and ecological system.Our investigation shows that grazing ban and ecological migration are two major adaptation strategies in Alxa League.Grazing ban has led to a quick regeneration of local steppe on the one hand,and on the other hand the migration has enhanced pressure on emigrant towns.For instance,increase of population in the towns of over-cultivation has caused land degradation around the towns,and over-use of deep ground water has made ground water drop and surface soil salinization.The grazing ban has also led to a series of negative effects,such as increase in mouse population and fire risk due to accumulation of dry matter,and the final decrease of biological diversity although there is an initial increase since grazing ban.Some local shrubs degrade without grazing,showing that a certain extent grazing can maintain the ecological balance of stepepe.It turns out that ungulate plays an important role in the ecological system of the west Inner Mongolia.To quantitatively investigate the grazing effect,we made a numerical simulation of local grassland NPP(Net Primary Production) under different grazing pressures with a forest dynamical model(FORSPACE),which incorporated ungulate grazing,wild fire,hydrological process,ecological system,and climate change.It confirmed that suitable grazing or controllable grazing would be not only in favorable to vegetation growth in dry land,especially to local shrubs,but also alternated in reducing the pressure of the emigrant towns and increase the income of local residents.By contrast,over grazing would destroy surface vegetation and lead to animal death.So local adaptation policy modification is proposed to allow some extent grazing,and encourage enclosed economical animals feeding.The policy should combine both local economic development and ecological conservation under global warming background.