Soliveres Santiago, Maestre Fernando T, Eldridge David J, Delgado-Baquerizo Manuel, Quero José Luis, Bowker Matthew A, Gallardo Antonio
Área de Biodiversidad y Conservación. Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, 28933 Móstoles, Spain. ; Institute of Plant Sciences, University of Bern, 3013 Bern, Switzerland.
Área de Biodiversidad y Conservación. Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, 28933 Móstoles, Spain.
Glob Ecol Biogeogr. 2014 Dec 1;23(12):1408-1416. doi: 10.1111/geb.12215.
The global spread of woody plants into grasslands is predicted to increase over the coming century. While there is general agreement regarding the anthropogenic causes of this phenomenon, its ecological consequences are less certain. We analyzed how woody vegetation of differing cover affects plant diversity (richness and evenness) and multiple ecosystem functions (multifunctionality) in global drylands, and how this changes with aridity.
224 dryland sites from all continents except Antarctica widely differing in their environmental conditions (from arid to dry-subhumid sites) and woody covers (from 0 to 100%).
Using a standardized field survey, we measured the cover, richness and evenness of perennial vegetation. At each site, we measured 14 ecosystem functions related to soil fertility and the build-up of nutrient pools. These functions are critical for maintaining ecosystem function in drylands.
Species richness and ecosystem multifunctionality were strongly influenced by woody vegetation, with both variables peaking at relative woody covers (RWC) of 41-60%. This relationship shifted with aridity. We observed linear positive effects of RWC in dry-subhumid sites. These positive trends shifted to hump-shaped RWC-diversity and multifunctionality relationships under semiarid environments. Finally, hump-shaped (richness, evenness) or linear negative (multifunctionality) effects of RWC were found under the most arid conditions.
Plant diversity and multifunctionality peaked at intermediate levels of woody cover, although this relationship became increasingly positive under wetter environments. This comprehensive study accounts for multiple ecosystem attributes across a range of woody covers and environmental conditions. Our results help us to reconcile contrasting views of woody encroachment found in current literature and can be used to improve predictions of the likely effects of encroachment on biodiversity and ecosystem services.
预计在未来一个世纪，木本植物在全球范围内向草原的扩张将会加剧。虽然对于这一现象的人为成因已基本达成共识，但其生态后果却尚无定论。我们分析了不同覆盖度的木本植被如何影响全球旱地的植物多样性（丰富度和均匀度）以及多种生态系统功能（多功能性），以及这种影响如何随干旱程度而变化。
来自除南极洲以外各大洲的224个旱地站点，其环境条件（从干旱到半干旱）和木本植物覆盖度（从0到100%）差异很大。
通过标准化的实地调查，我们测量了多年生植被的覆盖度、丰富度和均匀度。在每个站点，我们测量了14种与土壤肥力和养分库积累相关的生态系统功能。这些功能对于维持旱地的生态系统功能至关重要。
物种丰富度和生态系统多功能性受到木本植被的强烈影响，这两个变量在相对木本覆盖度（RWC）为41 - 60%时达到峰值。这种关系随干旱程度而变化。我们在半干旱地区观察到RWC呈线性正效应。在半干旱环境下，这些积极趋势转变为RWC与多样性及多功能性之间的驼峰形关系。最后，在最干旱的条件下，发现RWC对丰富度、均匀度呈驼峰形影响，对多功能性呈线性负影响。
植物多样性和多功能性在木本覆盖度处于中等水平时达到峰值，尽管在更湿润的环境下这种关系变得越来越呈正相关。这项全面的研究考虑了一系列木本覆盖度和环境条件下的多种生态系统属性。我们的结果有助于调和当前文献中关于木本植物入侵的不同观点，并可用于改进对入侵可能对生物多样性和生态系统服务产生的影响的预测。
