A new vegetation model at the topographic scale in Mongolia under human activity and climate change
Abstract
To predict future vegetation not only the changes in climate conditions but those of essential human activities must also be incorporated in a vegetation model, since most terrestrial systems are now under the strong influence of both of these drivers. Previous dynamic vegetation models, however, had difficulties to incorporate these effects in a comparative way and one of the critical barrier was the mismatch of the spatial scales at which both of these drivers are quantified, that is, climate conditions are generally observed and modeled with much coarser resolutions than human activities often influenced by topography or transportation networks. In northern part of Mongolia, where plant growth is basically limited by water availability and grazing pressure by livestock, the vegetation exhibits a clear discontinuous transition between grassland and forest but no sound modeling could be achieved to clarify the transition mechanisms nor to project future vegetation and hence the distribution of ecosystem functions. To tackle this problem, we developed a pair of new models at the topographic scale (Models 1&2) based on the observation in a sample region in Mongolia. Model 1 is a mathematical model for the dynamic interactions among the two plant biomasses (grass and trees) and local soil water content (SWC). We here assume positive/negative feedbacks in plant growth-SWC interaction and uneven grazing pressures for the two plants. Model 2 estimates numerically the spatial distribution of the potential SWC governed by climate and topography conditions in a given region. We used satellite remote sensing data to obtain the spatial distributions of the initial vegetation cover and the topography. By integrating these two models we could successfully reconstruct the current spatial vegetation patterns in our sample area only when we assumed a strong positive feedback in plant growth-SWC interaction and grazing pressure. This result underscores the importance of the positive feedback process at the topographical scale. Further, we suggest the vegetation might exhibit "ecological regime-shift" at this scale under heavy drought and/or livestock grazing pressure. Using this model, we could estimate the change in ecosystem functions by increasing livestock and suggest the maximum sustainable livestock density under given climate change scenarios.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMGC23A0892I
- Keywords:
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- 0410 BIOGEOSCIENCES Biodiversity