| Popis: |
Fine roots play an important role in energy flow and substance cycling in forests. How-ever, the estimates of biomass, production and turnover of fine roots remain large uncertainties, and the mechanism underlying local-scale spatial variation in fine roots is still unclear. In a temperate secondary forest in the Maoer Mountain in Northeast China, we investigated the vertical distribution of fine root biomass and necromass at the 0-100 cm profile and the dynamics, production and turnover rate of fine root in 0-20 cm soil layer. The sequential coring (including the Decision Matrix and the Maximum-Minimum formula) and the ingrowth core (3 cm diameter and 5 cm diameter) were compared in estimating production and turnover rate of fine roots. Forest stand variables that might affect fine roots were also explored. The results showed that 76.8% of fine root biomass and 62.9% of necromass concentrated in the 0-20 cm soil layer, and that both decreased exponentially with increa-sing soil depth. The seasonal variation in both fine root biomass and necromass was not significant in 0-20 cm soil layer, which might be related to the negligible snowfall in winter and the extremely high precipitation in summer. There was no significant difference in the results of the estimated fine root production between two diameter ingrowth cores. After log-transformed, fine root production and turnover rate estimated by the Decision Matrix, the Maximum-Minimum formula and ingrowth cores were significantly different among methods. With the increases of soil nutrient concentrations, fine root biomass/fine root necromass ratio significantly increased, fine root necromass significantly decreased, whereas fine root biomass, productivity, and turnover rate were not related to soil nutrient. There was a significant positive correlation between fine root production and aboveground woody biomass increment in the previous-year but not current-year.细根在森林生态系统能量流动与物质循环中占有重要地位,但其生物量、生产和周转测定尚存在很大的不确定性,而且局域尺度空间变异机制尚不清楚。本研究分析了帽儿山温带天然次生林活细根生物量和死细根生物量在0～100 cm剖面的垂直分布与0～20 cm细根的季节动态、生产力和周转率,对比了采用连续根钻法(包括决策矩阵法和极差法)和内生长袋(直径3和5 cm)估测细根生产力和细根周转率,并探讨了可能影响细根的林分因子。结果表明: 76.8%的活细根生物量和62.9%的死细根生物量均集中在0～20 cm土层,随着深度增加,二者均呈指数形式减少。活细根生物量和死细根生物量的季节变化不显著,可能与冬季几乎无降雪而夏季降雨异常多有关。2种直径内生长袋估计的细根生产力无显著差异;对数转换后决策矩阵、极差法和内生长法估计的细根生产力和细根周转率差异显著。随着土壤养分增加,活细根生物量和死细根生物量比值显著增加,死细根生物量显著减少,但活细根生物量、细根生产力和细根周转率均无显著变化;细根周转率与前一年地上木质生物量增长量呈显著正相关,但与当年地上木质生物量增长量无显著相关关系。. |
