秦岭大熊猫栖息地巴山木竹生物量

The biomass of Bashania fargesii in giant pandas habitat in Qinling Mountains

巴山木竹是秦岭大熊猫冬、春季食物的主要来源,其生长状况、数量和空间分布格局与大熊猫的生存与活动有着密切的关系。为了探讨不同立地因子对巴山木竹生物量的影响,确定巴山木竹生长的主导因子和适宜立地条件,在秦岭大熊猫栖息地内选取54块样地,对不同立地条件下巴山木竹生物量进行了测定。通过统计分析,结果表明:由于不同地区气候和土壤条件的差异,导致了巴山木竹生物量亦存在较大差别;巴山木竹生物量在其分布区内随海拔的升高而呈规律性变化,1500—1700 m为最适分布区域,其生物量最大;坡度越大生物量越小,陡坡不适宜竹林的生长;上坡位不利于竹林生长,而中、下坡位生物量没有显著差异;坡向对生物量的影响不明显,均适宜巴山木竹生长;在落叶阔叶和针阔混交林中,当林冠郁闭度>0.6时,竹林生长减弱。在这些立地因子中,影响巴山木竹生物量积累的主导因子是坡位和林冠郁闭度。

Bashania fargesii is one of the middle-large amphipodial bamboos,which distributes mainly in the deciduous broad-leaved forests or coniferous and broad-leaved mixed forests in the elevation of 1100—1900 m in Qinling Mountains.The bamboo（Bashania fargesii） is the principal food source for Qinling giant pandas in winter and spring.The giant pandas′ survival and activity are associated with growth status,quantity and spatial pattern of Bashania fargesii.The bamboo biomass is crucial in exploring Qinling giant pandas′ habitats selection,but also in providing guidelines for the conservation actions of Qinling giant pandas.However,there is lack of empirical research on the spatial distribution characteristics of Bashania fargesii biomass.This study was aimed to investigate the site effects on Bashania fargesii biomass distribution.The key factors and the suitable site condition for the bamboo growth were assessed. The bamboo biomass,height,basal diameter,population,and density with different site conditions（including elevation,slope,slope position,slope aspect,and canopy closure） were measured in 54 sample plots of giant pandas habitat in Foping,Huangbaiyuan and Pingheliang natural reserves.These natural reserves are located on south-facing slope in the middle of the Qinling Mountains in Shaanxi Province.In this research,the effects of different site conditions on the bamboo biomass were analyzed by using the methods of t test and multiple regression with SPSS software.Our results show that the distribution of the bamboo varied regularly by site factors as follows：（1） The bamboo biomass varied significantly in different investigated areas.In this study,the rich biomass density and favorable growth status were found in Foping and Huangbaiyuan natural reserves,while the poor biomass density and less favorable growth status in Pingheliang natural reserves.This was probably caused by the different hydrothermal conditions and characteristics of the community structure of the different investigated areas.（2） The bamboo biomass changed with elevation.The good bamboo communities were located between the elevation of 1500 m and 1700 m,while the bamboo communities were not observed below the elevation of 1300 m and above 1700 m.（3） The bamboo biomass decreased with the increase of slope,and the steep slope was hard for its growth compared with other slopes.（4） The upper slope was difficult for the bamboo growth.The biomass difference was insignificant between the mid and lower slope.（5） The effect of slope aspect on the bamboo biomass was insignificant.Both of the slope aspects were suitable for the bamboo growth.（6） There was a remarkable correlation between the bamboo biomass and the canopy closure.When canopy closure of deciduous broad-leaved forests or coniferous and broad-leaved mixed forests was over 0.6,the bamboo grew feeble. In conclusion,the dominant site factors influencing Bashania fargesii biomass were slop position and canopy closure.The bamboo forests tend to grow relatively tall with thick stems and rich biomass on mid or lower and gentle slopes in deciduous broad-leaved forests or coniferous and broad-leaved mixed forests with medium canopy closure between the elevation of 1500 m and 1700 m.These areas seem to be the most suitable habitats for the giant pandas in winter and spring.