保护区周边居民薪柴采集对乔木分布的影响——以四川王朗大熊猫自然保护区为例

保护区内周边地区的自然村庄中人们的日常生活对于村庄附近的森林群落结构有着重要的影响。通过分析乔木蓄积量和“乔木-灌木”复合系统中乔木的相对密度随着距离村落中心远近变化的函数关系，揭示当地居民薪柴采集活动对于乔木分布影响的规律。首先对于四川省平武县木座乡、木皮乡和白马乡里10个村庄进行随机入户农村家庭经济调查，掌握基本经济条件；然后对于调查结果进行聚类分析，选定小河、厄里和详述加3个典型村庄作为研究对象。按照距村落中心距离远近作梯度样带调查，计算出各个样带中的木材蓄积量和“乔木一灌木”复合系统中乔木的相对密度，利用数理统计方法进行模型拟合。拟合结果显示：（1）贫富差距对于乔木分布规律没有明显的影响，3个村落的数据分析结果类似。说明这3个村落的贫富差距还没有足以影响村落周围乔木分布。（2）木材蓄积量和“乔木．灌木”复合系统中乔木的相对密度与距村落中心位置距离的函数关系分别符合Logistic模型和Growth模型。在距离小于第1域值（3，4km）的时候，因变量随着自变量——距离的增加而缓慢增加。这说明这一区域内乔木分布受到薪柴采集活动影响很大，虽然也有所增加但是趋势不明显。当距离在第1域值（3～4km）至第2域值（7—8km）的时候，曲线切线斜率突然增大。这说明薪柴采集活动频率和强度迅速增加，因而导致乔木的蓄积量和密度都快速恢复。当距离继续增大的时候，因变量增长速率又逐渐回落，乔木分布也已经与原始林中的状态相似。

The impact of firewood collection by local people on the distributing of arbors around the nature reserves: A case study in Wanglang Nature Reserve for Giant Panda(Sichuan)

The activities of local people living in or around the nature reserves have important influences on the structure of forest communities. This study focused on the influences, which come from the firewood collecting by the local people, on the distribution of arbors. Through the investigation in 10 villages near the Wanglang nature reserve, the income levels of the villages were divided into 3 ranks using the K-means Cluster, and 3 villages, which are the closest to the average values of each rank, were chosen to do the detailed analysis. At 90 sites around these 3 villages, some information was recorded on the characteristics of arbors (species, height, diameter at breast height, and percentage of cover) and shrubbery (species, height, quantity, percentage of cover, basal diameter and weight). Based on these data, the results indicated that the cumulative quality of the timber and the tree density relative to the one of shrubby both were the function of the distance to the center of the village (independent variable). By using the SPSS (Statistical Program for Social Sciences), regressive curves estimation was made in 10 math models. From the results of estimating, significant difference could not be found among the 3 villages so that the conclusion can be made as follow: the economic gaps existing in these 3 villages didn't affect obviously the distribution of the arbors. It is because that the economic differences lying among the 3 villages are not significant enough to cause the changing on the approaches and the quantities of firewood collection of the local people. In addition, the results of curve estimation show that the R2 reaches the peak when comparing the function between the independent variable and the cumulative quality of the timber with the Logistic Model. Simultaneously, the maximum R2 appeared when we compared the function curve composed by the independent variable and the tree density relative to the one of shrubby with the Growth Model. The distributing pattern can be easily found from the curve of the function. At first, the dependent variable ascended gently along with the increasing of the independent variable, which illustrates that if the distance to the center of the village is less than the first threshold (between 3 km to 4 km), firewood collection plays a key role in the distribution of arbors. Even if the quality and the quantity increase, the trend changes slightly. However, if the distance keeps going up, the slope of the curve rises up suddenly and sharply. The trend is caused by the dramatic intensity reducing of the negative disturbance from firewood collecting, and the existing range lies from the first threshold to the second threshold (between 7 km to 8 km). And after that, due to the human's influence on firewood collecting reduce gradually and almost can be ignored, the increasing trend of the curve becomes gentle again, and finally, the quality and quantity of the arbors go back to what they are in the original state.