Modelling the effects of patch size on vegetation dynamics:: Bracken [Pteridium aquilinum (L.) Kuhn] under grazing

被引:32
作者
Birch, CPD [1 ]
Vuichard, N
Werkman, BR
机构
[1] Macaulay Land Use Res Inst, Aberdeen AB15 8QH, Scotland
[2] ISIMA, F-63173 Aubiere, France
[3] Abisko Sci Res Stn, Climate Impacts Res Ctr, SE-98107 Abisko, Sweden
关键词
bracken; Calluna vulgaris; grazing; heathland; hexagonal grid; indirect competition; invasion; mosaic; spatial simulation; Pteridium aquilinum; trampling;
D O I
10.1006/anbo.1999.1081
中图分类号
Q94 [植物学];
学科分类号
071001 ;
摘要
A new spatial simulation model of vegetation dynamics, called 'VegeTate', was applied to relationships between expansion of bracken (Pteridium aquilinum (L.) Kuhn) patches and grazing. VegeTate simulates multispecies dynamics within each cell of its grid, including localized apparent competition mediated by grazing and trampling. It can be parameterized to simulate various plant communities and species, includes seasonality and uses a hexagonal grid. Dynamics of individual bracken patches in grassland, and of heathland initially containing sparse grass and bracken were simulated. Mixtures of grass and bracken formed mosaics, in which locally high grass densities were associated with low standing mass and high grazing intensity, whereas high bracken densities were associated with high standing mass and low grazing intensity. Control of bracken by grazing depended on the impact of trampling. In simulations, small bracken patches occupying one or a few cells could be controlled by grazing, but not the expansion of large patches. In a sensitivity analysis, this phenomenon was reproduced after substantial changes in parameter values and environmental conditions, suggesting that it should be observable in the held. Interaction between patch size and grazing impact strongly influenced the spatial dynamics of simulated vegetation. The size of bracken patches became bimodal, so that most of the area of bracken was within a few large patches. Both spatial and temporal vegetation dynamics became non-linear. These results are consistent with observations that some bracken patches contain several genets and some genets occupy several patches. The hexagonal grid and trampling were important factors in the simulation results. (C) 2000 Annals of Botany Company.
引用
收藏
页码:63 / 76
页数:14
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