Collaborative Research: Facilitation, Competition and Woody Patch Dynamics in a Savanna Parkland

9815607 ArcherSavanna研究强调了树木对土壤、小气候和牧草的影响。关于树与树的相互作用以及这些作用如何影响萨卡纳的功能和动态，人们知之甚少。此外，稀树草原的研究在很大程度上是在个别树木散布在长满草的基质中进行的。然而，乔木和灌木岛的形成在许多干旱陆地生态系统中是一种常见的现象，但很少被研究。这个合作项目将量化德克萨斯州中南部热带稀树草原生态系统中覆盖树、蜂蜜和相关的林下灌木之间促进和竞争相互作用的机制。该项目的目标是阐明与草原和开阔稀树草原向闭合树冠带刺林地的地貌转变相关的斑块动态机制。其具体目标是阐明与乔灌木岛的启动和发展相关的机制，并预测这些岛屿上的物种相互作用如何随着时间的推移而在不同的地貌景观中发生变化。这项研究的方法将包括选择性移栽和相互移植实验的结合，这些实验将与资源(光、养分和土壤水分)的操纵以及植物生长、叶片化学、叶片气体交换、植物/土壤水分关系和同位素丰度的测量相结合。结果将提高我们概括草原和稀树草原木本植物增加的演替和竞争的作用和机制的能力，增强我们表示和参数化乔灌草生态系统的空间显式模拟模型的能力，并直接有助于发展监测、管理和操纵草原和稀树草原生态系统的良好基础。

9815607ArcherSavanna research has emphasized tree effects on soils, microclimate and grasses. Little is known of tree-tree interactions and how these might influence sacanna function and dynamics. Furthermore, savanna research has largely been conducted where individual trees are scattered throughout a grassy matrix. However, the formation of tree and shrub islands is a common, but little-studied phenomenon in many arid land ecosystems.This collaborative project will quantify mechanisms of facilitative and competitive interactions between an overstory tree, honey mesquite, and associated understory shrubs in a subtropical savanna ecosystem in south-central Texas. The goal of the project is to elucidate mechanisms of patch dynamics associated with the physiognomic transformation of grassland and open savanna to closed-canopy thorn woodland. The specific objectives are to elucidate the mechanisms associated with the initiation and development of tree-shrub islands, and to predict how species interactions in these islands change across topoedaphically diverse landscapes over time. The approach to this research will involve a combination of selective removal and reciprocal transplant experiments that will be coupled with manipulations of resources (light, nutrients and soil moisture) and measurements of plant growth, foliar chemistry, leaf gas exchange, plant/soil water relations and isotopic abundances. Results will increase our ability to generalize the roles of facilitation and competition in succession and mechanisms of woody plant increase in grasslands and savannas, enhance our ability to represent and parameterize spatially explicit simulation models for tree-shrub-grass ecosystems, and contribute directly to the development of a sound basis for monitoring, managing and manipulating grassland and savanna ecosystems.