Using spectral analysis to confront distributions of individual species with an overall periodic pattern in semi-arid vegetation
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- 作者：Pierre Couteron
- 关键词：Community structure ; Spatial patterns ; Spectral analysis ; Tiger bush ; West Africa ; Woody vegetation
- 刊名：Plant Ecology
- 出版时间：2001
- 出版年：2001
- 期刊代码：97_13850237
- 类别：med
- 卷：156
- 期：2
- 页码：229-243
- 数据来源：sp
摘要
Contrasted and periodic vegetation patterns are observed throughout thesemi-arid tropics. The relation between individual species and theoverall pattern has been investigated from a study site in NorthWest Burkina Faso (West Africa), which displayed periodic woody patterns withvarying levels of contrast and isotropy. The woody vegetation was described fromtwo field plots (320 by 320 ), within which woodyindividuals were either mapped or counted (in quadrats of 10 by10 ). A banded pattern of high intensity (tiger bush on hardsandstone, plot PTG) was compared with a less precise pattern on more favourableedaphic conditions (plot PSP). The periodic nature of the vegetation under studywas directly addressed by interpreting spatial auto- and cross-covariancefunctions through spectra of spatial frequencies (spectral analysis). Theoverall pattern of vegetation was analysed from digitised aerial photographs,while distributions of individual species were characterised from field data. Inboth plots, the densest species (Combretum micranthum G.Don), though only dominant in PTG, had a spatial distribution that closelymatched the overall pattern. Pterocarpus lucens Lepr wasco-dominant in both plots although fairly independent on the periodic pattern.Several species displayed a positive link with the periodic pattern that wasquite loose in PSP and tighter in PTG. This tighter link was concomitant withlower densities for most species. Indeed, only C.micranthum clearly benefited from the high intensity pattern with adensity seven times higher in PTG than in PSP. Consequently, species richnessand diversity were lower in PTG. A single species proved hence of overwhelmingimportance in accounting for the periodic pattern and its persistence throughtime. Spatial distributions of other species pointed rather towardsindividualistic responses to the opportunity/constraint provided by theperiodic pattern in presence of different levels of edaphic and climatic stress.