人为干扰对秦巴山区中段植物物种联结性的影响

Effect of Human Disturbance on Interspecific Association of Plants in the Middle of Qinba Mountain Area

为了研究秦巴山区中段植被在不同干扰状态下物种联结性的变化规律,以瀛湖流域为研究对象,按照人为干扰强度的差异,将其分为轻度干扰、中度干扰、重度干扰三个区域,采用典型取样法,在每个区域内设置15个样方套,通过方差比率、χ^(2)检验、OI指数等方法计算乔、灌、草三个层次的物种联结性。结果表明:①在45个样方套中共记录植物100科、195属、256种;乔、灌、草三个层次的科数依次增加,但在3种不同干扰状态下共有科的比例却依次减少,共有种也有相似的变化规律。②不同干扰状态下各层次科的数量变化规律与种的变化规律大致相同,草本植物在中度干扰状态下科数与种数均为最高;灌木层的科数、种数均随着干扰程度的加强而减少;乔木层的变化不明显。③随着干扰的加强,乔、灌、草三个层次的总体联结性均发生变化;乔木层在轻度干扰下呈无联结性,但其测度值较低,极易触及负联结,随着干扰程度的加强,其变化规律为无联结—负联结—无联结;灌木层总体联结关系的变化最为显著,其变化规律为正联结—无联结—负联结;草本层呈现无联结—正联结—无联结的变化规律;④建立2×2列联表,将21个重要值较高的物种进行比较发现,在不同的干扰强度下,无联结关系的物种对所占的比例差异不大,均占主导地位;随着人为干扰强度的加大,负联结关系的物种对数量明显减少,使正、负物种对数量之比加大;同轻度干扰相比,中度、重度干扰下正、负联结关系的显著性均有所削弱;自然状态下呈负联结关系的物种对更容易受人为干扰影响,使其数量与联结程度同时降低;⑤相对而言,研究区内灌木层的破坏程度大于乔木层与草本层。

An experiment was conducted in the Yinghu Lake basin to examine how the interspecies asso‑ciation of plants in central Qinling-Daba mountains changes under different disturbance conditions.The basin was divided into a mild disturbance zone,a moderate disturbance zone,and a heavy disturbance zone according to the degree of human disturbance.The typical sampling methods was used,and 15 quad‑rat sets of samples were set up in each zone.The interspecies association was calculated at the levels of tree,shrub,and herb using variance ratio,χ^(2) test,and OI index.The results revealed that 100 families,195 genera,and 256 species of plants were recorded in the 45 quadrat sets.The number of families in‑creased in sequence of trees,shrubs,and herbs.The proportion of common families,as well as common species reduced in sequence under three disturbance conditions.Under different disturbance states,the number changes of families and species were roughly the same.Herbs had the largest number of both fam‑ilies and species under moderate disturbance.For shrubs,the number of families and species reduced with increasing disturbance degree.For trees,the change was not prominent.With the increase of distur‑bance degree,overall association changed at the tree,shrub,and herb levels.Under mild disturbance,the trees did not show association,but the measured value was quite low and could turn negative any time.As disturbance degree increased,the overall association changed to none-positive-none.Shrubs displayed the most significant change in overall association,being positive-none-negative.The associa‑tion of herbs was none-positive-none.Comparison of 21 species with high importance values in a 2×2 ta‑ble revealed that the proportion of non-associated species pairs did not change much under different dis‑turbance degrees and was always dominant.As the degree of human disturbance increased,the number of negatively associated species pairs reduced markedly,increasing the population ratio between positive and negative species pairs.Compared with mild disturbance,both positive and negative associations were less significant under heavy disturbance.Under natural conditions,negatively associated species pairs were more susceptible to human disturbance,leading to a reduction in both the number and association degree.Shrub in the study area was more heavily disturbed than trees and herbs.