尾巨桉林不同生长发育阶段的土壤理化性质与林下植物多样性的动态变化趋势及其规律

Soil Physicochemical Properties and Dynamic Changes of Understory Plant Diversity at Different Growth and Development Stages of Eucalyptus urophylla×Eucalyptus grandis Plantation

[目的]对比滇南山地桉树纸浆林不同龄组的林分生长指标、土壤理化性质与林下植物多样性的变化及相关性,探索桉树人工林从幼龄林至过熟林不同生长发育阶段的土壤理化性质与林下植物多样性的动态变化趋势及其规律,旨在为桉树纸浆林可持续经营提供理论依据。[方法]本研究选取土壤以粗粒结晶岩、泥类岩和碳酸盐岩发育形成的赤红壤或红壤,海拔1400~1700 m立地条件基本一致的样地106块,分属5个不同龄组,通过方差、多重比较和冗余分析不同龄组的生长指标、土壤因子和植物多样性指数之间的差异,采用相关性分析揭示它们之间的关联性。[结果]不同龄组尾巨桉的树高、胸径和活立木蓄积量随林分生长而呈增长趋势,中龄林时增速较快,而到成熟林(7~8 a)时增速放缓。不同龄组间土壤孔隙度和土壤含水量差异显著,并随林分生长过程整体呈先上升后下降的趋势,在近熟林时达到最高值。不同龄组的土壤全氮差异显著,且林木树高、胸径和活立木蓄积量的生长与全氮有较强正相关。尾巨桉林下草本和总灌草的丰富度指数、草本均匀度指数与土壤有机质、有效锌呈正相关。灌木的丰富度指数与土壤含水量、有效氮、有效铜呈正相关。草本和灌木的Shannnon-Wiener指数与土壤全氮呈正相关,与土壤密度、pH值呈较大的负相关。灌木Pielou均匀度指数与土壤全钾呈正相关。其中,土壤有机质对尾巨桉林下植被多样性的影响最大,解释比例达18.3%(F=13.21,P<0.05)。[结论]滇南山地立地生境相近的尾巨桉人工林,幼龄林生长与草本植物存在竞争关系,植物多样性对土壤结构及其物理性质的影响大于化学性质的影响,近成熟时,总灌草、灌木生物多样性达最大值,揭示了近成熟后桉树人工林生态系统进入自恢复演替。

[Objective]To study the growth status,soil physical and chemical properties and understory plant diversity of Eucalyptus urophylla×Eucalyptus grandis pulpwood plantation of different age groups in southern Yunnan for providing theoretical basis for sustainable management of eucalyptus pulpwood plantation.[Method]In this study,106 plots of red soil or red soil developed from coarse-grained crystalline rocks,muddy rocks,and carbonate rocks,with similar site conditions at an altitude of 1400~1700 meters,belonging to 5 different age groups.The differences in growth indicators,soil factors,and plant diversity indices among different age groups were analyzed through variance,multiple comparisons,and redundancy analysis.Correlation analysis was also used to reveal the correlation between them.[Result]The height,DBH and living wood growing stock of E.urophylla×E.grandis plantation in different age groups increased with the growth of the stand.The growth rate was faster in the middle-aged forest,but slowed down in the mature forest(7-8a).There were significant differences in soil porosity and soil moisture content among different age groups,and the overall trend showed an increase and then a decrease with the growth of the stand,reaching the highest value in the near mature forest.There were significant differences in soil total nitrogen among different age groups,and the growth of tree height,diameter at breast height,and stand volume were significantly correlated with total nitrogen.The richness index and evenness index of herbaceous and total shrubland under the Eucalyptus urophylla forest were positively correlated with soil organic matter and available zinc.The richness index of shrubs was positively correlated with soil moisture,available nitrogen,and available copper.The Shannon Wiener index of herbs and shrubs was positively correlated with soil total nitrogen,while it was significantly negatively correlated with soil bulk density and pH value.The evenness index of shrub Pielou was positively correlated with soil total potassium.Among them,soil organic matter had the greatest impact on the understory vegetation diversity of Eucalyptus urophyllus,with the variance accounting for 18.3%(F=13.21,P<0.05).[Conclusion]There is a competitive relationship between the growth of young E.urophylla×E.grandis plantation and herbaceous plants.The influence of plant diversity on soil structure and physical properties is greater than that of chemical properties.At near maturity,the total shrub and shrub biodiversity reaches the maximum,which reveals that the eucalyptus plantation ecosystem enters self-restoring succession after near maturity.