华北落叶松林细根生物量对土壤水分、氮营养空间异质性改变的响应

在华北落叶松(Larix principis-rupprechtii)林选取采伐干扰样地和未采伐干扰样地进行对比研究, 分析采伐干扰造成林下土壤水分和氮营养空间异质性的改变对细根生物量空间变异的影响。采用空间格局分析的小支撑、多样点的设计原则, 对每个样点的土壤分3层取样(0-10 cm、10-20 cm、20-30 cm)。进行细根(≤1 mm和1-2 mm)生物量与土壤含水量、全氮、硝态氮、铵态氮和土壤pH的偏相关分析, 以及细根生物量变异函数值和土壤各因子变异函数值的线性回归分析。研究结果表明, 在不同样地, 细根生物量与土壤各因子均表现为正相关关系, 不同土层相关性强弱表现各异, 其中土壤含水量与细根生物量的相关性显著。受采伐干扰后, 细根生物量与土壤含水量、全氮、土壤硝态氮空间变异的关联性更趋于明显。多元线性回归分析结果表明, 采伐干扰样地细根生物量的空间变异更多地受到土壤多因子的综合影响, 而未采伐干扰样地的细根生物量受土壤水分、全氮和硝态氮单独效应的影响更大。

Response of fine root biomass to changes in spatial heterogeneity of soil moisture and nitrogen in Larix principis-rupprechtii forest

Aims Fine root biomass is known to respond to spatial heterogeneity in the distribution of soil characteristics. Cutting disturbance created changes of soil physical and chemical factors, but how the changes affect fine root biomass and turnover processes remain unclear. Our objective was to analyze the relationships of spatial heterogeneity of the fine root biomass with changes of soil moisture and nitrogen by cutting disturbance in Larix principisrupprechtii forest.
Methods This study was conducted in L. principis-rupprechtii forest of Pangquangou National Natural Reserve, located in Guandi Mountain, Shanxi Province, China. Two plots (32 m × 32 m) were placed. Plot A was a disturbed stand, but plot B was undisturbed. Each soil core (30 cm depth) was separated into 3 sections, 0–10, 10–20 and 20–30 cm. The live fine roots were classified into two categories (≤ 1 and 1–2 mm). The partial correlation and the multi-regression coefficients of the semivariance between fine root biomass and soil moisture, nitrogen and pH were analyzed based on theory and methodology of spatial pattern analysis in geostatistics.
Important findings Spatial variability of fine root biomass and spatial heterogeneity of soil nitrogen and soil moisture were positively correlated, with the latter being significantly stronger than the former. After cutting disturbance, the correlation became more significant. The correlation between spatial variability of fine root biomass and spatial heterogeneity of soil ammonium (NH₄⁺) and pH was unclear in disturbed and undisturbed stands. Multiple regressions of soil factors against biomass of fine root were statistically significant. However, spatial distribution of biomass of fine roots was largely affected by soil moisture and total nitrogen and nitrate nitrogen after cutting disturbance.