湖南栎类天然次生林幼树更新特征及影响因子

以湖南典型栎类天然次生林为研究对象,基于51块样地的调查数据,采用k-means聚类分析划分林分类型,研究湖南不同栎类天然次生林幼树更新特征,分析了湖南不同栎类天然次生林幼树更新指标(幼树密度、幼树平均地径、平均高以及平均冠幅)与环境因子、林分因子的相关性,旨在阐明环境因子、林分因子对幼树更新的影响,以期为湖南不同栎类天然次生林的恢复与经营管理提供理论依据。结果表明:(1)利用聚类分析可将研究区内栎类天然次生林划分为5个类型,包括甜槠锥栗混交林(CC)、亮叶水青冈多脉青冈混交林(FC)、石栎樟树混交林(LC)、枹栎甜槠混交林(QC)、青冈栎混交林(CG)。(2)不同类型栎类天然次生林更新幼树优势种分化明显,物种丰富度差异显著(P0.05)。5种不同栎类次生林幼树密度均未超过500株/hm~2,更新情况较差;幼树数量差异显著(P0.05),为亮叶水青冈多脉青冈混交林石栎樟树混交林青冈栎混交林枹栎甜槠混交林甜槠锥栗混交林;生长情况差异显著(P0.05),为青冈栎混交林亮叶水青冈多脉青冈混交林枹栎甜槠混交林甜槠锥栗混交林石栎樟树混交林。(3)相关分析结果显示,不同类型次生林幼树更新的主要影响因子存在差异。甜槠锥栗混交林中幼树密度与腐殖质厚度呈显著负相关(P0.05);幼树平均高与灌木盖度呈显著正相关(P0.05);幼树平均地径与草本盖度、灌木盖度呈显著正相关(P0.05)。亮叶水青冈多脉青冈混交林中幼树密度与海拔、腐殖质厚度、枯落物厚度呈显著正相关(P0.05),与草本盖度呈极显著正相关(P0.01);幼树平均地径与郁闭度呈显著负相关(P0.05);幼树平均高、幼树平均冠幅与坡位呈显著正相关(P0.05)。石栎樟树混交林中幼树密度与坡向、土壤厚度呈显著正相关(P0.05),其余因子对幼树生长无显著影响。枹栎甜槠混交林中幼树密度与郁闭度、乔木密度呈极显著正相关(P0.01),与坡位呈显著负相关(P0.05);幼树平均冠幅与坡度呈显著负相关(P0.05)。青冈栎混交林中幼树平均地径与土壤厚度呈显著正相关(P0.05),与乔木密度呈极显著正相关(P0.01);幼树平均冠幅与灌木盖度呈显著正相关(P0.05)。

Regeneration characteristics and related factors affecting saplings in Quercus spp. natural secondary forests in Hunan Province, China

Quercus forest is a typical forest type in Hu''nan Province, which plays an important role in water and soil conservation, and maintaining ecological stability. However, most of the natural regeneration of Quercus forest in Hunan is poor, because of limited research on Quercus regeneration mechanisms, and ineffective management. Based on field investigation data, we analyzed typical Quercus natural secondary forests in Hunan, and used k-means cluster analysis to classify forest types. In this research, we studied sapling regeneration characteristics of different Quercus natural secondary forests in Hunan and examined the correlation of the sapling regeneration index (density, average ground diameter, average height, and average crown width of saplings) with environmental and stand factors in different Quercus natural secondary forests in Hunan. This study aimed to provide a theoretical basis for the restoration and management of natural secondary forests of different Quercus species in Hunan Province. The results showed that the natural secondary forest of Quercus could be divided into five types by cluster analysis, including Castanopsis eyrie-Castanea henryi mixed forest (CC), Fagus lucida-Cyclobalanopsis multinervis mixed forest (FC), Lithocarpus glaber-Cinnamomum bodinieri mixed forest (LC), Quercus serrata-Castanopsis eyrie mixed forest (QC), and Cyclobalanopsis glauca mixed forest (CG). The dominant species and species richness of the regeneration forests of different types of Quercus secondary forests were significantly different(P < 0.05). The sapling density in five different secondary forests of Quercus was < 500 trees/hm², and sapling regeneration was poor. The number of saplings of different Quercus secondary forests was significantly different(P < 0.05), in the order of FC > LC > CG > QC > CC. The sapling growth status in different forests was significantly different(P < 0.05), and in the sequence of CG > FC > QC > CC > LC. The results of the correlation analysis showed that there were differences in the main factors affecting sapling regeneration in different types of secondary forests. In CC, there was a significant negative correlation between the sapling density and humus thickness(P < 0.05), a significant positive correlation between the average sapling height and shrub coverage(P < 0.05), and a significant positive correlation between the average sapling basal diameter and herbaceous and shrub coverage(P < 0.05). In FC, there was a significant positive correlation between sapling density and altitude, humus thickness, and litter thickness(P < 0.05), and a very significant positive correlation with herbaceous coverage(P < 0.01), a significant negative correlation between average ground diameter and canopy density(P < 0.05), and the average sapling height and crown width were significantly positively correlated with the slope position(P < 0.05). In LC, there was a significant positive correlation between sapling density and slope direction and soil thickness(P < 0.05), whereas the other factors had no significant effect on sapling growth. In QC, sapling density was extremely positively correlated with canopy and tree density(P < 0.01), and negatively correlated with slope position(P < 0.05), and the average sapling crown width was negatively correlated with slope(P < 0.05). In CG, the average sapling diameter was significantly positively correlated with soil thickness(P < 0.05), and had an extremely significant positive correlation with tree density(P < 0.01), and the average sapling crown width was positively correlated with shrub coverage(P < 0.05).