四种不同生活型树种细根寿命及影响因素

以4种不同生活型树种(常绿阔叶和针叶树种、落叶阔叶和针叶树种)为研究对象,通过微根管法现地观测细根的生长动态,比较不同生活型树种细根寿命在种内和种间的差异,探讨影响细根寿命的主要因子,研究结果对理解和预测森林生态系统碳及养分循环过程具有重要的理论意义。结果表明:(1)细根形态特征(分枝结构和直径)显著影响种内细根寿命,分枝等级越低、直径越小,细根的寿命越短;(2)4个树种的细根寿命表现出明显的土层效应和季节效应,即随土壤深度增加,细根的累积存活率逐渐增加,寿命延长;而不同季节出生的细根其寿命长短模式在树种间不一致,春季或夏季出生的细根寿命要长于秋冬季;(3)常绿树种(柳杉、石栎)的细根寿命要长于落叶树种(池杉、麻栎),同时,针叶树种(池杉、柳杉)的细根寿命要长于阔叶树种(麻栎、石栎)。在同一树种内,细根寿命受细根直径、根系分枝结构、土壤环境因子(土层)等因素显著影响,但在不同树种间,细根寿命可能更依赖于树木生长速率、碳分配模式等树木整体的功能性状差异。

Fine root lifespan and influencing factors of four tree species with different life forms

In this study, four tree species with different life forms (evergreen broad-leaved, coniferous species, deciduous broad-leaved, and coniferous species) were used as the experimental materials. The growth dynamics of fine roots were observed by minirhizotron method. We compared differences in the root lifespan for tree species with different life forms within and between species, and also explored the main factors affecting the lifespan of fine roots. The study would help us to understand carbon and nutrient cycling processes in forest ecosystems. The results showed that: (1) fine root morphological characteristics (branched structure and root diameter) significantly affected the lifespan of fine roots within the species. The fine root lifespan with the lower branching order and the smaller diameter was shorter than that of the higher-order roots and the coarser roots. (2) The root lifespan showed obvious soil layer effect and the seasonal effect, that is, with the increase of soil depth, the cumulative survival rate of fine roots gradually increased and the root lifespan was prolonged; while the lifespan pattern of fine roots born in different seasons was inconsistent among tree species. The lifespan of the fine roots born in spring or summer was longer than that born in autumn and winter. (3) The fine roots lifespan of evergreen trees (Lithocarpus glaber and Cryptomeria fortunei) was longer than that of deciduous trees (Quercus acutissima and Taxodium ascendens). The fine root lifespan of conifers trees was longer than that of broadleaf species. Generally, within the tree species, the fine root lifespan is significantly affected by factors such as fine root diameter, root branching structure, and soil environmental factors (soil layer). However, between tree species, fine root lifespan may be more dependent on the differences in functional traits of trees as a whole, such as tree growth rate, carbohydrate distribution patterns.