宝天曼自然保护区主要森林类型自然度评价

自然度评价对于自然保护区生物多样性保护和森林管理具有重要意义。以宝天曼自然保护区主要林型35个样地为研究对象,对27个群落指标进行主成分分析,计算自然度指数值(N),对N值进行Ward聚类,划分自然度等级。结果表明:宝天曼自然保护区主要林型的自然度可划分为5个等级组,自然度高的样地:N值在2.18—1.13之间,平均林龄94a,占调查样地总数的20.0%;自然度较高的样地:N值在1.01—0.34之间,占调查样地总数的34.3%,平均林龄80a;自然度中等的样地:N值在0.01—-0.47之间,占调查样地总数的17.1%,平均林龄为47a;自然度较低的样地:N值在-0.92—-1.60之间,占调查样地总数的14.3%,平均林龄为26a;自然度低的样地,N值在-1.98—-2.54之间,占调查样地总数的14.3%,平均林龄为21a。前3个主成分中土壤容重、有机质、全氮、硝态氮、林龄、优势树种平均胸径、乔木层、灌木层和草本层的多样性指数荷载较大,是影响森林自然度的主要因子。N值与林龄、乔木层和灌木层的Shannon-Wiener指数、海拔、土壤容重的线性拟合均达到极显著水平(P0.001),与土壤有机质和全氮的关系符合对数曲线(R20.794,R2=0.815,P0.0001)。在海拔1118—1863m区域,森林自然度较高,海拔970m以下区域,森林自然度较低。针对不同自然度等级的森林,分别提出了相应的保护和经营措施。

Naturalness assessment of the main forest types in the Baotianman National Nature Reserve

Assessment of forest naturalness plays an important role in biodiversity conservation and forest management. In the present study, we selected thirty-five plots from the main forest types, and investigated 30 indicators (three topographic indicators and 27 community indicators) in the Baotianman National Nature Reserve. Community indicators (27) were analyzed using the PCA method to determine forest naturalness index values (N). N values were clustered using the Ward cluster method, and naturalness classes were classified according to those cluster groups. The results showed that: the degrees of forest naturalness were divided into five grades: highest naturalness plots: with N values ranging from 2.18 to 1.13, an average stand age of 94a, and total plots accounting for 20.0%; higher naturalness plots: with N values ranging from 1.01 to 0.34, an average stand age of 80a, and total plots accounting for 34.3%; medium naturalness plots: with N values ranging from 0.01 to -0.47, an average stand age of 47a, and total plots accounting for 17.1%; lower naturalness plots: with N values ranging from -0.92 to -1.60, an average stand age of 26a, and total plots accounting for 14.3%; and lowest naturalness plots: with N values ranging from -1.98 to -2.54, an average stand age of 21a, and total plots accounting for of 14.3%. Among the first three principal components, soil bulk density, soil organic matter, total nitrogen, nitrate nitrogen, stand age, mean diameter at breast height (DBH) of the dominant trees, and diversity indices of the arbor, shrub, and herb layers were all greater than the other indicators, and were key factors that influenced forest naturalness. The N value was significantly negatively linear when fitted to soil bulk density (R² = 0.763, P < 0.0001), and significantly positively linear when fitted to stand age, and Shannon-Wiener indices of shrub and arbor layers and altitude, respectively (P < 0.001). Logarithmic curve fitting reached significant levels between N value and soil organic matter, and total nitrogen, respectively (R² > 0.794,R² = 0.815,P < 0.0001). Greater forest naturalness was observed at sites at an altitude of 1118-1863 m. At an altitude of <970 m, forest naturalness sharply decreased. Based on the different classes of forest naturalness, some corresponding measures for discussion and management were proposed.