Use of Summer Precipitation Along a Summer Precipitation Gradient

该提案旨在了解普通干旱地区植物利用夏季降水事件的能力，以及不同水源对生长和干物质生产效率的影响。初步数据表明，西部山间地区的一些优势多年生物种似乎不利用夏季降水，尽管夏季降水是这些生态系统年水输入的主要组成部分。本文建议研究几种与植物对夏季降水的利用有关的假设，以及这与沿夏季降水增加梯度的生物质生产效率之间的关系。研究将集中于使用稳定同位素分析来确定水源和干物质生产效率。野外研究将在5个站点进行，这些站点夏季降水量在15% - 52%之间，但总降水量和温度在其他方面相似。研究将重点关注沙漠与温带森林生态系统过渡中的优势亚乔木种：杜松（Juniperus osteosperma）、松（Pinus edulis）和灌丛栎（Quercus gambelii）。拟议的研究在应用方面具有很强的潜力。稳定同位素分析提供了包括水分利用和干物质生产效率在内的植物参数的综合长期估计。从这项研究中获得的信息和技术将有助于确定用于森林木材和纸浆树种评价的性状种类。林农和农学家已经开始使用这些稳定同位素方法对不同的遗传品系进行综合分析。

This proposal is directed at understanding the ability of common arid region plants to utilize summer precipitation events and the consequences of different water sources for growth and for the efficiency of dry matter production. Preliminary data indicate that several of the dominant perennial species in the Intermountain West appear not to utilize summer precipitation, even though summer rain is a major component of the annual water input to these ecosystems. It is proposed to examine several hypotheses related to a plant's utilization of summer precipitation and how this relates to the efficiency of biomass production along a gradient of increasing summer precipitation. Research will be centered on using stable isotope analyses to determine both water sources and efficiency of dry matter production. Field studies will be conducted at five sites, which range from 15% to 52% summer precipitation, but which are otherwise similar in total precipitation and temperature. The study will focus on dominant tree-subtree species in the ecosystem transitional between desert and temperate forest ecosystems: Juniper (Juniperus osteosperma), pinyon pine (Pinus edulis) and scrub oak (Quercus gambelii). There is strong potential for applied aspects of the proposed research. Stable isotope analyses provide integrated long-term estimates of plant parameters involving water use and efficiency of dry matter production. The information and techniques derived from this study will be useful in determining the kinds of characters to be used for evaluation of forest timber and pulp species. Foresters and agronomists are already beginning to use these stable isotope approaches for integrated analyses of different genetic lines.