土壤含水量对旱季降香黄檀树干呼吸和非结构性碳水化合物的影响

Effects of soil moisture on stem respiration and non-structural carbohydrates of Dalbergia odorifera in the dry season

为研究土壤含水量对旱季树体水势、树干呼吸和边材非结构性碳水化合物(NSCs)变化特征的影响,设置重度隔水(HD)、轻度隔水(LD)、旱季灌溉(DI)和对照(CK)4个土壤含水量水平,每隔半月监测各参数的动态变化。旱季土壤含水量和枝条水势呈下降趋势,各处理从11月底开始表现出显著差异。各处理树干呼吸与树干温度均具有良好的指数函数关系(R2≥0.65,P<0.001),各处理温度敏感系数Q10为DI>CK>LD>HD(P<0.001)。旱季树干温度和树干呼吸均呈下降趋势,且在1月达到最低。各处理树干温度只在气温较低的冬季达差异显著,树干呼吸总体表现为旱季灌溉增加树干呼吸,而干旱降低树干呼吸。旱季淀粉含量下降,可溶性糖含量上升,非结构性碳水化合物总量总体保持不变。各处理边材淀粉和可溶性糖差异显著,而NSCs总量差异不显著。相比于DI和CK,干旱(LD和HD)加速了旱季边材淀粉分解为可溶性糖的速率。树干呼吸与淀粉、可溶性糖均具有显著回归关系,树干呼吸分别解释了淀粉72%和可溶性49%的旱季变化;枝条水势解释了49%树干呼吸、75%淀粉和85%可溶性糖的旱季变化。土壤含水量很可能通过改变树体组织含水量,进而影响边材NSCs和树干呼吸。这些变量之间紧密的联系可能为干旱可以促进降香黄檀心材形成的猜想提供一定的理论基础。另外,基于树干呼吸与树体水势和NSCs的显著关系,树干呼吸可能也会对树木心材形成有一定指示作用。

To investigate the effects of soil moisture on predawn shoot water potential （ψpd） , stem respiration （Rs ） and non-structural carbohydrates （NSCs） during the dry season, four soil moisture levels including heavy drought （HD）, light drought （LD）, dry-season irrigation （DI） and control （CK） were set up in Dalbergia odorifera plantations. All those parameters were measured semimonthly. Soil moisture content and ψpd declined continuously and had significant differences among treatments after November. Rs increased exponentially with temperature and the coefficients of determination were all greater than 0. 65. Q10 differed signifcantly among treatments, following the order of DI〉CK〉LD〉HD. Stem temperature （T） and Rs declined continuously during the dry season and reached their minimum values in January. There was no significant difference of temperature among moisture treatments except in winter. Irrigation increased the Rs rate, and drought decreased it. The soluble sugars tended to increase during the dry season at the cost of starch, which caused a small but non-significant increase in NSCs. The effect of moisture treatments on the content of total NSCs was limited; however, the drought treatment increased the soluble sugars content and decreased the starch content. Low soil moisture induced by drought enhanced the transformation of starch to soluble sugars during winter, when heartwood formed. Rs explained 72% and 49% of the seasonal variation in starch and soluble sugars, respectively. The ψpa explained 49%, 75% and 85% of the variance in the Rs, stem starch and soluble sugars, respectively. Soil moisture likely affects R8 by modulating the amounts of sapwood starch and soluble sugars. These strong relationships provide evidence for the hypothesis that drought would promote heartwood formation in D. odorifera. In addition, given the significant relationship between R8 and NSCs, the variation in the Rs may also indicate changes in heartwood formation.