Modelling vegetation dynamics in heterogeneous pasture-woodland landscapes
Modelling vegetation dynamics in heterogeneous pasture-woodland landscapes
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DOI：
10.1016/j.ecolmodel.2008.05.013
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发表时间：
2008-09-24
影响因子：
3.1
通讯作者：
Gillet, Francois
中科院分区：
文献类型：
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作者：
Gillet, Francois
最近的知识树木再生，移动镶嵌在草本层或牛的活动，植被和景观结构之间的复杂的相互作用，允许开发一种新的，空间上明确的，镶嵌分区模型的动态的森林草原生态系统（WOODPAM）。该确定性模型考虑了三个层次：焦点层是植物群落，代表景观中的一个单元或斑块，具有可变的局部蓄积密度，草本和灌木群落以及大小结构的乔木种群是低层斑块的组成部分，在空间上是隐式的;将斑块聚集在建立更高级别的牧区管理单元中，模拟试验应用于一个牧场，林地景观，以评估等级组织的生态相互作用对植被和牛栖息地利用的时空格局的后果。在第一种设想中，全球环境和管理条件固定在观测到的初始值上。植被和牛的栖息地利用的模式演变在很长一段时间向一个永久的状态为主的森林牧场，强烈依赖于环境的空间配置。景观动态非常缓慢，第二种情景考虑到气候变化的影响，即考虑到年气温的线性上升，这影响到饲料生产和植被动态的速度。结果表明，在斑块水平上，植被多样性下降，格局变得不稳定，并出现长周期的循环演替，牲畜选择性在保持植被多样性和异质性方面发挥着重要作用。高选择性发生在低的整体放养率，诱导景观缓慢破碎成开放的牧场和封闭的森林和木材牧场的下降。低选择性发生在高利用率，减少景观的异质性。这些结果进行了讨论，结合放牧生态学和林地动态的最新理论。(C)2008 Elsevier B. V.保留所有权利。
Recent knowledge about tree regeneration, shifting mosaic in the herb layer or complex interactions between cattle activities, vegetation and landscape structure has allowed the development of a novel, spatially explicit, mosaic compartment model of the dynamics of silvopastoral ecosystems (WOODPAM). This deterministic model considers three hierarchical levels: the focal level is the phytocoenosis, represented by a cell or a patch in the landscape with a variable local stock density; herb and shrub communities as well as size-structured tree populations are the components of each patch at the lower level, spatially implicit; patches are aggregated in a pastoral management unit building the higher level, with an externally controlled global stock density.Simulation experiments were applied to a pasture-woodland landscape in order to assess the consequences of hierarchically organized ecological interactions on spatio-temporal patterns of vegetation and cattle habitat use. In the first scenario, the global environmental and management conditions were fixed to their observed initial values. The patterns of vegetation and cattle habitat use evolved at very long term toward a permanent state dominated by wood-pastures, strongly dependent on the spatial configuration of the environment. Landscape dynamics being very slow, the second scenario took into account the effect of climate change, by considering a linear increase of the annual temperature, which influenced forage production and the speed of vegetation dynamics. in this simulation, closed forests and densely wooded pastures tended to dominate, vegetation diversity decreased, the patterns became unstable and long-period cyclic successions appeared at patch level.Model simulations emphasized the role of livestock selectivity to preserve vegetation variability and heterogeneity at long term. A high selectivity occurs at low overall stocking rate, inducing a slow fragmentation of the landscape into open pastures and closed forests and a decline of wood-pastures. A low selectivity occurs at high utilization rates, decreasing the heterogeneity of the landscape.These results are discussed in the light of the recent theories binding grazing ecology and woodland dynamics. (C) 2008 Elsevier B.V. All rights reserved.