水分和种植密度对干热河谷车桑子生长性状及种内相互关系的影响

水分是干热河谷植物生长过程中最主要的限制因子，种植密度增加也会引起植物生长的资源限制，两者交互作用下植物生长性状及种内关系的变化特征还不清楚。以干热河谷优势植物——车桑子为研究对象，根据元谋干热河谷年均生长季降雨量设置3种水分梯度：高水分、中水分和低水分，同时在各水分梯度下设置4个种植密度：1、2、4、9株/盆，探究水分、种植密度及其交互作用对车桑子生长性状、生物量分配及种内相互作用的影响。结果表明：（1）低水分条件下，车桑子生长和水分生理受到抑制，但车桑子在较低的叶水势下依然能够保持较高的相对含水量；（2）干旱胁迫显著降低了车桑子总生物量和单株生物量，显著增加了枯叶生物量比例，低水分和中水分条件下，增加种植密度对总生物无显著影响；而高水分条件下，增加种植密度显著提高了车桑子总生物量；（3）低水分显著增加了茎、叶生物量的异速生长指数，将更多生物量分配到叶，而种植密度增加显著降低了茎、叶生物量的异速生长指数，增加了茎的生物量分配；（4）通过相对邻体效应的计算，各处理条件下，车桑子种内关系均表现为竞争作用，并且，这种竞争作用的强度随水分的减少和密度的增加而增加。在高密度条件下（9棵/盆），增加水分不会减轻种内竞争作用。综上，水分和种植密度均会对车桑子个体的生理生长产生影响，在植被恢复过程中，应考虑水分和种植密度对车桑子个体产生的资源限制作用。

Effects of water and planting density on the growth characteristics and intraspecific relationships of Dodonaea viscosa in a dry-hot valley

Water is the most important limiting factor in the growth of plants in dry-hot valleys; furthermore, the increase in planting density also causes resource limitation in plant growth. However, the interactive effects of water and planting density on plant growth characteristics and intraspecific relationships are not clear. In this study, Dodonaea viscosa, a dominant species in dry-hot valleys was used as the research subject. According to the rainfall during the growing season of Yuanmou dry-hot valley, D. viscosa was planted with three water levels (high water, medium water, and low water) and at four densities (1, 2, 4, and 9 plants/pot) to explore the influence of water, planting density, and their interaction on growth, biomass accumulation, and intraspecific interaction of D. viscosa. The results showed that (1) under the low-water treatment, the growth and water physiology of D. viscosa were inhibited, but the relative water content was still high when the leaf water potential decreased greatly. (2) Drought stress significantly reduced the total biomass and individual biomass and significantly increased the proportion of litter biomass. Under the low-water and medium-water treatments, the increase in planting density had no significant effect on total biomass, whereas under the high-water treatment, the increase in planting density significantly improved total biomass of D. viscosa. (3) The allometric exponent of stem biomass and leaf biomass was significantly greater under the low-water treatment, which indicated relatively more biomass was allocated to leaves, and the allometric exponent decreased under high-planting density. (4) The intraspecific relationship of D. viscosa exhibited a competitive effect, and the intensity of the competitive effect increased with decreased water content and increased with an increase in planting density. Under the high-density treatment (9 plants/pot), increasing water content did not reduce the competitive effect. In conclusion, both water and planting density affected the growth and physiological characteristics of D. viscosa. In the process of vegetation restoration, the effect of water and planting density on resource constraints of D. viscosa should be considered.