氮、水交互对长白山阔叶红松林细根形态及生产量的影响

土壤养分和水分的变化深刻影响着森林生态系统的碳分配,进而影响树木细根形态结构和生产量。本文以我国长白山阔叶红松林为研究对象,研究氮沉降增加(50 kg/(hm·a))和降雨量减少(30%穿透雨,约210 mm/a)情形下,细根形态结构和生产量的时空响应特征。结果表明,细根形态结构和生产量受多种因素(处理、取样时间、取样层次)的共同影响。施氮样地(N)显著降低了0~10 cm土壤层细根直径,从而增加了比根长, 减少降雨样地(D)细根根长密度增加了1.55~3.24倍,细根生产量增加了104 g/(m·a), 减少降雨同时施氮样地(DN)10~20 cm土壤层细根直径和生产量显著增加。因此,长白山阔叶红松林不同土壤层细根在氮和水分吸收功能上可能存在分化,氮沉降增加、降雨格局变化及其交互作用在不同程度上驱动着细根形态和生产量的时空变化。 

Effects of nitrogen﹣water interaction on fine root morphology and production in a mi.ed Pinus koraiensis forest in Changbai Mountains,northeastern China

Changing soil nutrient and water profoundly influence carbon allocation in the forest ecosystem, and then impact morphology and production of tree fine roots. We studied the responses of fine root morphology and production in scenarios of increased nitrogen deposition (50 kg/( ha·yr) ) and decreased precipitation (30% throughfall, about 210 mm/yr) in a broadleaf﹣Pinus koraiensis forest in Changbai Mountains, northeastern China. Results demonstrated that various factors ( treatment, sampling date, soil layer) collectively influenced the morphology and production of fine roots. Nitrogen fertilization ( N ) significantly decreased the diameter, but increased specific root length of fine roots in 0 -10 cm soil layer;the root length density in dry treatment plots ( D) had been raised by 1. 55-2. 44 times and the production of fine roots increased by 104 g/( m2·yr) as compared with CK plots; decreased throughfall and nitrogen fertilization ( DN) significantly increased the diameter and production of fine roots in 10-20 cm soil layer. Thus, there might be the functional differentiation on nitrogen and water uptake of fine roots in different soil layers in the mixed Pinus koraiensis forest, and the spatial﹣temporal variations of fine root morphology and production are activated by nitrogen deposition, changed precipitation and their interactions.