青海省森林细根生物量及其影响因子

细根是植物吸收水分和养分的主要器官。全球变暖背景下,研究森林细根生物量及其环境因子的变化对生态系统碳平衡、碳收支及其贡献率具有重要意义。采用土钻法和室内分析法对青海省森林6个海拔梯度上5种林分类型的细根生物量和土壤理化性质进行测定,并分析了与环境因子之间的相互关系。结果表明:(1)青海省森林0—40 cm土层总细根生物量平均为8.50 t/hm~2,随着海拔梯度的增加先降低后升高,不同海拔梯度细根生物量差异显著(P0.05),最大值出现在2100—2400 m处。(2)5种林分0—40 cm土层总细根生物量为:白桦白杨云杉圆柏山杨,不同林分间细根生物量差异不显著。(3)细根垂直分布随土层深度增加而减少,且70%的细根集中在表层(0—20 cm)。(4)土壤容重深层(20—40 cm)显著大于表层(P0.05),并随海拔梯度逐步增加,且林分间差异较大。(5)全碳(Total carbon, TC)、全氮(Total nitrogen, TN)、全磷(Total phosphorus, TP)含量表层显著高于深层。TC、TN随海拔升高先增后降低,TP则随海拔逐步降低。不同林分间土壤养分差异较明显。(6)结构方程模型分析得到海拔、土层、容重直接影响细根生物量,细根生物量直接影响土壤养分。林分类型通过土壤容重间接影响细根生物量。因此,林分和海拔通过影响土壤微环境而影响到细根生物量及其空间分布格局。

Forest biomass and its influencing factors in Qinghai Province

Fine roots are the main organs that plants use to absorb water and nutrients. In the context of global warming, it is of great significance to study the biomass of fine roots and the environmental factors affecting carbon balance, carbon budget, and contribution rate of the ecosystem. In this study, the soil drilling method and indoor analysis were used to determine the fine root biomass and soil physical and chemical properties of 5 species in forest system on 6 elevations in Qinghai Province. The relationships between fine root biomass and environmental factors were further analyzed. The results showed that:(1) In Qinghai Province, the average of the total fine root biomass was 8.50 t/hm² in 0-40 cm soil depth. With the altitude increase along the gradient, fine root biomass decreased first and then increased. There were significant differences in the biomass of fine roots among different altitudes (P < 0.05), and the highest peak of fine root biomass appeared at 2100-2400 m. (2) The total fine root biomass of 5 forest species in the 0-40 cm depth was as follows:Betula platyphylla < Populus tomentosa < Picea asperata < Sabina chinensis < Populus davidiana. There were no significant differences in biomass of fine roots among different stands. (3) Fine root biomass decreased with the soil depth, and 70% of the fine roots were concentrated in 0-20 cm soil layer. (4) Soil bulk density in the 20-40 cm soil layer was significantly greater than that in the 0-20 cm soil layer (P < 0.05). It increased with the altitude, and there were substantial differences among the 5 forest species. (5) The contents of total carbon (TC), total nitrogen (TN) and total phosphorus (TP) in the surface soils (0-20 cm) were significantly higher than those in the deeper soils (20-40 cm). TC and TN increased first and then decreased, while TP decreased with the altitude gradient. The differences in soil nutrients between different forest species were obvious. (6) SEM analysis showed that the fine root biomass was significantly correlated with altitude, soil layer, and bulk density, and the biomass of fine roots directly affected soil nutrients. The forest species affected the fine root biomass indirectly. Therefore, the plant species and elevation affected the biomass and spatial distribution of fine roots by influencing the soil micro-environment.