不同植被恢复类型的土壤肥力质量评价

科学确定森林土壤肥力指标并进行肥力质量的评价,对立地生产力和多目标森林经营的研究有着重要意义。以采伐(径级12 cm择伐)迹地上发育来的稀树灌丛、针叶林、针阔混交林和常绿阔叶林为研究对象,进行每木调查与群落分析,并比较各群落土壤因子间的差异,用典范对应分析(CCA)和因子分析对土壤肥力质量进行定量评价。结果表明,CCA可以有效地筛选土壤肥力质量指标,有助于质量指标的科学确定;土壤肥力质量综合评价分值为稀树灌丛(0.438)常绿阔叶林(0.414)针阔混交林(-0.170)针叶林(-0.331);演替初期(19 a)的植被恢复并未使土壤结构发生明显变化,土壤肥力质量是下降的;无人为干扰的3种群落类型,针叶林表现为更高的生物量积累,而天然更新的常绿阔叶林则更有利于生物多样性的增加与土壤养分的保蓄。

Soil fertility quality assessment under different vegetation restoration patterns

Soil fertility quality assessment based on scientifically determined indicators has significant implications for the study of stand productivity and multi-objective forest management. We carried out plant census and community analysis, and compared soil physicochemical properties among forest communities in Kanghe Nature Reserve. The four community types, i.e., scrub, evergreen broadleaved forest, coniferous-broadleaved mixed forest, and coniferous forest, represented different vegetation restoration patterns originating from a selective-logging (at 12 cm diameter) event on the subtropical evergreen broadleaved forest. The main soil factors influencing tree composition and distribution were screened by Canonical Correspondence Analysis (CCA), which were subsequently used to build the minimum data set (MDS). Soil fertility quality was quantitatively assessed with Factor Analysis on MDS.The results showed that distribution of tree species was unevened. With the lowest species richness, the coniferous forest was exclusively dominated by Cunninghamia lanceolata, whereas in the most species rich evergreen broadleaved forest, codominant tree species existed. Average tree DBH (diameter at breast height) decreased successively among coniferous forest, coniferous-broadleaved mixed forest and evergreen broadleaved forest.Soils were highly acidic (pH < 5.0) and the content of AvK, ExMg, AvMn, AvZn and AvFe had no significant difference(P > 0.05)across the four forest communities. A lower canopy density due to less canopy trees resulted in the lower soil moisture content in the scrub community, which had a higher mineral element content than other vegetation patterns as a whole. Distribution of trees was closely related to soil environmental factors, but the results of CCA indicated that there was no significant correlation (Monte Carlo Test,P > 0.05) between composition and distribution of tree species and the seven soil factors, i.e., AN, ExCa, AvK, TP, ST, AP and NCP, which should be excluded when building the MDS. Therefore, the findings revealed that CCA was an effective tool for screening soil fertility quality indicators and establishing MDS by demonstrating the effect of soil fertility on plant patterns.Factor analysis was applied on MDS to assess the fertility quality and the cumulative variance explained by five principal components was 84.67%, indicating this evaluation method was reliable. The integrated soil fertility quality assessment scores for scrub, evergreen broadleaved forest, coniferous-broadleaved mixed forest, and coniferous forest were, in a descending order, 0.438, 0.414, -0.170, and -0.331, respectively. Vegetation restoration did not obviously change soil structural parameters, such as soil texture, capillary porosity, non-capillary porosity, and bulk porosity, however, soil fertility quality declined in the early succession stage (19 a). In the three community types without human disturbance, coniferous forest had the highest biomass accumulation, whereas evergreen broadleaved forest from natural regeneration was more conducive to the increase of biodiversity and soil nutrient accumulation. Site-specific indicators, including soil physicochemical factors and biological factors, should be selected in future assessment of soil fertility quality. The appropriate quantitative ecological methods could make the determination of evaluation index more scientific.