The influence of soil depth on plant speciesresponse to grazing within a semi-arid savanna
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- 作者：Fuhlendorf ; Samuel D. ; Smeins ; Fred E.
- 关键词：Ecology ; Functional groups ; Diversity ; Herbivory ; Heterogeneity ; Patch dynamics ; Pattern ; Plant ; animal interaction ; Rangelands ; Redundancy ; Scale ; Shifting mosaic ; Succession
- 刊名：Plant Ecology
- 出版时间：1998
- 出版年：1998
- 期刊代码：97_13850237
- 类别：med
- 卷：138
- 期：1
- 页码：89-96
- 数据来源：sp
摘要
Grassland patches within a semi-arid savanna wereevaluated over 45-years for (1) local temporaldynamics of basal area for five dominant grass specieswithin long-term heavily grazed and ungrazedtreatments, (2) the influence of soil depth (resourceavailability) on vegetation dynamics, and (3) theapplicability of community-level grazing responsegroups over fine-scale patterns of soil heterogeneity.Temporal patterns in species composition and basalarea were dependent upon soil depth. In the heavygrazed treatment, Hilaria belangeri dominateddeep soils while Erioneuron pilosum andBouteloua trifida were restricted to shallow soils.In the ungrazed treatment, removal of grazing resultedin successional changes that were significantlydifferent across soil depths. After 45 years withoutgrazing, Eriochloa sericea was most abundant ondeep soils while Bouteloua curtipendula was moreabundant on intermediate and shallow soils.Community-level functional groups that are based ongrazing were not appropriate when multiplepattern-driving variables were considered acrossmultiple scales indicating that functional groupsshould only be applied to certain processes atspecific scales. Within the ungrazed treatments,variable soil depths have resulted in a shiftingmosaic in time and space where early- andlate-successional species co-exist continuously butspatially separated within the community. In theheavily grazed treatment, species are somewhatspatially arranged by soil depths, but much of theinherent heterogeneity is eliminated and speciescomposition is dominated by the threegrazing-resistant short-grasses. Broad scalesuccessional changes may appear linear and predictablewhile at finer scales, the same changes may bedescribed as non-linear and dependent upon soil depthresulting in thresholds that are partially explainedby weather patterns, seed bank limitations andcompetitive inhibitions.