两种石漠化等级下樟树-马尾松混交林林分结构及物种多样性

Stand structure and species diversity of the camphor-masson pine mixed forest under two rocky desertification grades

【目的】在石漠化地区,上层乔木种群和林下植被的出现和发育存在相互作用。结合不同石漠化等级程度,综合分析樟树-马尾松针阔混交林的林分特征,旨在探讨石漠化区域针阔混交林的空间结构特征和物种多样性及其相互关系。【方法】采用典型样地调查法,根据石漠化程度(轻度和重度)各设置3块20 m×40 m样地。使用指标量化方法分别对空间结构和乔灌草层不同生活型的物种多样性进行分析,并采用Pearson相关系数法分析两者之间的相关性。【结果】1)造林初期等比例种植马尾松和樟树,随着时间的演替,马尾松种群处于衰退状态,其他物种侵入形成多树种混交状态,从而形成较为复杂的林分空间结构。2)从物种多样性来看,轻度石漠化区域物种多样性指数优于重度石漠化区域,物种丰富,乔木层更新情况更好,小径阶的其他树种(冬青、光皮树、马褂木等)的生长状况都比较优良,存活率较高。3)从林分空间结构来看,轻度、重度石漠化区域群落的平均混交度分别为0.47、0.38,接近中度混交。平均大小比数都为0.49,表现为接近中庸状态。角尺度分别为0.56、0.50,都表现为随机分布,相关性验证发现,角尺度对不同石漠化程度下物种多样性存在显著影响。4)在石漠化地区,林下植被覆盖度低时,有利于马尾松幼苗定居,长成大树后林下环境得到改善,随着林下植被的增加,林下光照减少,养分竞争,马尾松幼树存活率大幅度降低,因此林下植被与上层乔木种群存在相互作用。【结论】在林下植被和光照、种间竞争等因素的影响下,经过40 a的演替,该地区的樟树-马尾松等比例混交林已经演变为以樟树为主体的多树种复层异龄混交林,但林分空间结构尚未达到理想状态。建议对樟树进行适度间伐,为其他树种的更新提供生存空间,有利于在石漠化区域构建更为稳定的森林群落。

【Objective】In rocky desertification areas,there was an interaction between the emergence and development of upper arbor populations and understory vegetation.In order to explore the spatial structure and species diversity of the coniferous and broad-leaved mixed forest in the rocky desertification region,the stand characteristics of the coniferous and broad-leaved mixed forest of camphor and masson pine were comprehensively analyzed based on different rocky desertification grades.【Method】According to the rocky desertification grades(mild or severe),three 20 m×40 m sample plots were set up by using the method of typical sample plot survey.The index quantification method was used to analyze the spatial structure and species diversity of different life forms in the arbor,shrub and grass layers,and the correlation between them was analyzed by Pearson correlation coefficient method.【Result】1)At the early stage of afforestation,masson pine and camphor were planted in equal proportions.With the succession of time,masson pine population was in a state of decline,and other species invaded to form a mixed state of multiple species,thus forming a more complex spatial structure of the stand.2)From the perspective of species diversity,the species diversity index of mild rocky desertification area was better than that of the severe rocky desertification area,which was rich in species and has a better renewal of the tree layer.The growth status of other small-scale tree species(Holly,Cornus wilsoniana,Liriodendron chinensis,etc.)was good,and the survival rate was high.3)From the perspective of stand spatial structure,the average mixing degree of the communities in the mild and severe rocky desertification areas was 0.47 and 0.38,which was close to a moderate mixing degree.The average size ratio was 0.49,which was close to the mean state.The angle scales were 0.56 and 0.50,respectively,showing a random distribution.Correlation verification showed that angle scales had a significant effect on species diversity of different rocky desertification areas.4)In the rocky desertification area,when the understory vegetation coverage was low,it was beneficial for the masson pine seedlings to settle,and the understory environment will be improved after growing into large trees.With the increase of understory vegetation,the understory light,nutrient competition and the survival rate of young masson pine decreased.Therefore,there was an interaction between understory vegetation and the upper arbor population.【Conclusion】Under the influence of factors such as understory vegetation,light and interspecific competition,the Camphor-Masson pine mixed forest in this area has evolved into a multi-layered heterogeneous mixed forest after 40 years of succession,with camphor tree as the main species.However,the stand spatial structure has not reached the ideal state.It is recommended that camphor should be moderately thinned to provide spaces for the regeneration of other tree species,which is beneficial to the construction of stable forest communities in rocky desertification areas.