林分年龄对落叶松人工林细根生物量的影响

【目的】随着森林的发育过程,林木个体的生长和生物量分配,以及林分水平的结构和功能均发生了明显的变化。然而,细根生物量与林分年龄的联系,目前仍然了解有限。本研究以黑龙江省帽儿山地区兴安落叶松人工林为研究对象,比较了同一林分在19年和32年生时林分水平(单位面积)和单株水平细根生物量的垂直分布和季节动态,分析了影响细根生物量变化的林分与土壤因子,旨在明确林分年龄对细根生物量的影响和潜在的机制。【方法】在生长季内的5月、7月和9月,采用土钻法获取土壤0~30 cm深度细根并测定生物量,同时测定林分特征和土壤养分和水分含量。【结果】随林龄增加,落叶松人工林单位面积细根生物量显著下降,而单株细根生物量变化不显著;与19年生林分相比,32年生林分土壤表层(0~10 cm)细根生物量占总细根生物量的比例明显下降,土壤亚表层(10~20 cm)和底层(20~30 cm)细根生物量所占比例增加,呈现出细根向深层土壤增生的趋势。土壤表层(0~10cm)单位面积细根生物量随林分年龄的变化趋势与林分密度和胸高断面积、土壤铵态氮浓度变化有关,但是单株细根生物量受林分和土壤因子的影响均不显著。【结论】林分发育过程中,落叶松细根生物量降低,细根的资源吸收策略发生了明显的改变。

Effect of Stand Age on Fine Root Biomass in A Larix gmelinii Plantation

【Objective】With the stand development,the growth and biomass allocation of trees at the individual level,and the structure and function of forests at the ecosystem level,both shift markedly. However,the relationship between fine root standing biomass and stand age is still remained unclear. The objective of this study was to reveal the impact of stand age on the dynamics of fine root(diameter 2 mm)biomass in forest ecosystems. We determined the vertical and seasonal dynamics of fine root biomass at the stand and individual tree levels in a Larix gmelinii plantation under two ages of 19 and 32 years in Maoershan,Heilongjiang Province,and analyzed their relations to stand and soil characteristics. 【Method】Fine root standing biomass to a soil depth of 0-30 cm was determined with soil core method in May,July,and September during the growing season. Stand characteristics and soil nutrients and water availability were measured concurrently.【Result】The results showed that fine root biomass per unit area declined significantly associated with stand aging,whereas fine root biomass per tree not. Compared with the stand age of 19 years,the proportion of fine root biomass of the surface soil(0-10 cm)to the whole soil profile(0-30 cm)decreased at the stand age of 32 years,but the proportions of subsurface(10-20 cm)and deep soil(20-30 cm)increased markedly,indicating the fine root tended to proliferate at the deeper soils. The dynamics of fine root biomass per unit area at the surface soil(0-10 cm)with stand aging were in relation with stand density,basal area at the breast height,soil ammonium concentration,however,fine root biomass per tree did not show any correlations with stand or soil characteristics.【Conclusion】These findings suggest that fine root biomass decreased,while resource acquisition strategy of fine roots changed associated with the development of L. gmelinii stand.