U.S.-Argentina Cooperative Research on Grass/Shrub Interactions in Two Temperate Semiarid Regions

该奖项支持科罗拉多州立大学的William K. Laurenroth教授和布宜诺斯艾利斯大学的O. E. Sala教授就半干旱地区草/灌木相互作用进行的合作研究。干旱半干旱区植被以禾草或灌木/矮乔木两种植物生命形式之一为主。在半干旱地区，灌木和灌丛地取代草和草地是一个严重的世界性问题。与灌木侵占问题相关的是关于这两种主要形式之间资源分配的一系列理论问题。其他问题来自于对草原和灌丛地地理分布的研究。模拟草和灌木之间相互作用的模型在预测热带稀树草原上的相互作用方面非常成功。这些模型通常简化并限制了资源分配的假设，即共存的禾草和木本植物对土壤水分的利用差异是由于获得不同的土层（双层假设）。研究人员计划研究这些模型在温带地区的适用性问题。此外，研究人员计划在现有资源分配理论模型的基础上，探索生物地理模型的潜力，以更好地预测草原和灌丛地的分布。该项目的北美站点位于科罗拉多州的中央十字地带，是由美国国家科学基金会资助的长期生态研究（LTER）全国网络的一部分。比较来自阿根廷场地的结果，不仅有助于继续长期合作，有助于我们对木本植物/草相互作用的理论理解，而且有助于判断场地的管理潜力，并有助于制定替代土地利用的决策。

This award supports cooperative research between Prof. William K. Laurenroth of Colorado State University and Prof. O. E. Sala of the University of Buenos Aires on grass/shrub interactions in semiarid regions. The vegetation of arid and semiarid regions is dominated by one of two life-forms of plants: grasses or shrubs/low trees. The replacement of grasses and grasslands by shrubs and shrublands is a serious worldwide problem in semiarid regions. Associated with this problem of brush encroachment is a collection of theoretical problems concerned with resource partitioning between these two dominant forms. Other problems arise from the study of the geographical distribution of grasslands and shrublands. Models that emulate the interaction between grasses and shrubs have been quite successful in predicting that interaction in tropical savannas. These models often make the simplifying--and limiting with regards to resource allocation--assumption that differentials in soil water use by coexisting grasses and woody plants is due to access to different soil layers (two-layer hypothesis). The investigators plan to study the question of the applicability of such models to temperate regions. Additionally, the investigators plan to explore the potential for a biogeographic model, based upon current theoretical models of resource partitioning, that may be used to better predict the distribution of grasslands and shrublands. The North American site for this project is in the Central Crossland Region in Colorado and is part of a nationwide network for long-term ecological research (LTER) funded by NSF. Comparison of results coming from the Argentinian site, will not only serve to continue a long standing collaboration and aid our theoretical understanding of woody plant/grass interactions, but will also aid in judging the management potential of sites and in the decision making about alternate land uses.