Shade trees in cacao agroforestry systems: influence on water resource use

可可农林复合系统中的遮荫树：对水资源利用的影响

• 批准号: 175292281
• 负责人: Professor Dr. Dirk Hölscher
• 金额: --
• 依托单位: Abteilung Waldbau und Waldökologie der Tropen
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2014-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/175292281?language=en
• 关键词: Shade; trees; cacao; agroforestry; systems

In cacao agroforestry, competition between cacao and shade trees for limited resources may reduce yields. In particular water availability is regarded a main determinant of cacao yield. Results of our previous experimental study however suggest that (1) there was a strong vertical partitioning of soil water uptake among cacao and shade trees, (2) during low rainfall periods, mainly cacao trees took up the small volumes of water reaching the soil, and (3) an increased shade tree canopy cover led to an increased rather than a decreased water use of cacao trees. This study was conducted at one site and with a single type of shade tree admixture. I thus want to further test these contentions aiming at more general conclusions. The proposed project intends to study cacao cultivation at three different shade tree admixture types (no shade trees, Gliricidia shade trees, native shade trees) with replicated plots at two sites with contrasting rainfall. The methods emphasize the application of stable isotope techniques (deuterium and 18O), using natural abundances as well as tracer experiments, supplemented by tree sap flux studies. Cooperation is planned particularly with a project addressing the productivity and species-specific root distribution in these stands.

在可可农林业中，可可和遮荫树之间争夺有限的资源可能会降低产量。特别是，水的可获得性被认为是可可产量的主要决定因素。然而，我们以前的实验研究结果表明：(1)可可树和遮荫树之间存在很强的土壤水分吸收垂直分配；(2)在降雨量较少的时期，可可树主要吸收到达土壤的少量水分；(3)遮荫树冠盖度的增加导致可可树的用水量增加，而不是减少。这项研究是在一个地点进行的，使用的是单一类型的遮荫树混合物。因此，我想进一步检验这些论点，以得出更普遍的结论。拟议的项目旨在研究三种不同的遮荫树混合类型(无遮荫树、Gliriciia遮荫树、本地遮荫树)的可可种植，并在两个降雨量不同的地点重复设置地块。这些方法强调稳定同位素技术(氚和18O)的应用，利用自然丰度和示踪实验，辅之以树液通量研究。计划开展合作，特别是与一个项目，解决这些林分的生产力和特定物种的根分布问题。