Interspecific variation in tree- and stand-scale stemflow funneling ratios in a subtropical deciduous forest in eastern China

Abstract

Stemflow is an important water flux in forested ecosystems, which is influenced by both biotic and abiotic factors. The stemflow funneling ratio, FP, is a straightforward parameter to express the funneling efficiency of individual trees,FP,Bt, or at the stand-scale, FP,Bs. Nevertheless, no known studies have compared the FP and its influencing factors between tree- and stand-scales in a subtropical deciduous forest. In this study, FP values from Q. acutissima and B. papyrifera trees were computed for a subtropical area of eastern China, and examined in relation to five biotic variables and ten abiotic variables. The relative contribution ratio (RCR) of each biotic and abiotic variable to FP,Bt and FP,Bs were evaluated by relative importance analysis. The median FP,Bs of B. papyrifera (104.2) was significantly higher than that of Q. acutissima (62.2), with the median FP,Bt of Q. acutissima and B. papyrifera both varying greatly among individual trees. Projected crown area (RCR = 29.2%) and diameter at breast height (RCR = 21.4%) were the two most important biotic factors governing FP,Bt of Q. acutissima, while the two critical biotic factors affecting FP,Bt of B. papyrifera were trunk lean (RCR = 62.2%) and tree height (RCR = 15.1%), respectively. At the stand scale, gross precipitation (GP), rainfall duration (DE) and vapor pressure deficit (D) were the three most critical factors affecting FP,Bs of Q. acutissima and B. papyrifera. GP and DE exerted positive effects but D a negative effect on stemflow generation. These findings provide new insights into the FP at both tree- and stand-scales within subtropical ecosystems.