鄂西南天然林主要乔木树种物种组成及林分空间结构动态变化研究

Study on the Dynamic Changes of Main Tree Species Composition and Stand Spatial Structure of Natural Forest in Southwest Hubei

该研究以鄂西南木林子国家级自然保护区内天然林为研究对象,以森林内胸径≥5 cm的乔木个体为具体分析对象,通过乔木树种重要值及其角尺度、大小比、混交度等林分空间结构参数的一元分布,阐述林分空间分布格局、大小分化程度、林木混交程度及变化,并通过分析林分空间结构参数的二元分布,探究各参数之间的联系,揭示5年间其林分空间结构特征及动态变化,为该林分类型的森林可持续经营提供准确的数据,以促进林分结构理想化,维持该区域物种多样性。结果显示:(1)2014年与2019年林分中主要建群种均为青冈(Cyclobalanopsis glauca),该种在群落中处于优势地位,鹅耳枥(Carpinus turczaninowii)重要值提高0.63%,其在林分中的相对重要性超过杉木(Cunninghamia lanceolata)位居第二,说明在该群落中鹅耳枥具有稳定的种群结构。(2)林分整体依然处于轻微团状分布状态,且各树种强度混交,平均混交度增长0.02,大小比均值降低0.01,林分生长依然处于中庸状态,5年来林分整体空间结构变化较小,但处于由当前林分结构向理想结构的过渡阶段。(3)结构参数两两组合的各组林分空间结构二元分布中,各参数不同取值等级的变化趋势基本不变,但大小比和混交度的二元分布结果显示林分中处于绝对劣势、劣势且零度混交、弱度混交的林木个体减少,林分稳定性得到提高。研究表明,研究区内天然林分空间结构动态变化虽不明显,但处于向更好、更稳定的结构发展中。

With the natural forest in Mulinzi National Nature Reserve in Southwest,Hubei Province as the research object,we took the trees with DBH(diameter at breast height)≥5 cm in forests as specific analysis objects.By analyzing the important value of tree species and their Uniform angle index,Dominance,Mingling stand spatial structure parameters,such as a distribution,stand spatial distribution pattern,size,degree of differentiation,trees mixed degree and the change,and through the stand spatial structure analysis of bivariate distribution,we revealed the spatial structure characteristics and dynamic changes of the stand in five years,to provide accurate data for the sustainable management of the forest type of this stand,in order to promote the ideal stand structure and maintain the species diversity in this area.The results showed that:(1)the main edificator in the 2014 and 2019 standing forest were Cyclobalanopsis glauca,which was dominant in the forest,and the important value of Carpinus turczaninowii increased by 0.63%,and its relative importance in the standing forest ranked second after Cunninghamia lanceolata.It indicated that C.turczaninowii had a stable population structure in this forest;(2)The standing fores were still in a slightly conglomerate distribution state as a whole,and the strength of each tree species was mixed.The average mixing degree increased by 0.02,and the average size ratio decreased by 0.01.The growth of standing forest was still in a moderate state,the overall spatial structure of the standing forest changed little in the past 5 years,but it was in the transition stage from the current standing forest structure to the ideal structure;(3)In the binary distribution of standing forest spatial structure of each group with pairwise combination of structural parameters,the change trend of different value grades of each parameter was basically unchanged,but the binary distribution results of Dominance and Mingling degree show that individual forest trees under situation of absolute disadvantage,disadvantage and zero-degree mixing,and weak-degree mixing were decreased.Meanwhile,the stability of standing forest was improved.Studies have shown that,although the dynamic change of spatial structure of natural stands in the study area is not obvious,they are developing toward better and more stable structure.