TEMPORAL AND SPATIAL VARIABILITY OF THE DIAMETER DISTRIBUTION IN A SECONDARY BRAZILIAN ATLANTIC FOREST SUGGESTS SITE-SPECIFIC MANAGEMENT PRACTICES

ABSTRACT The diameter distribution of a forest makes it possible to understand its ecological processes and to define actions related to forest management aiming at forest conservation, biodiversity increase, production, and carbon sequestration, among others. This study aimed to identify variation in the diameter distribution in a secondary Atlantic Forest, as a function of sites, over 24 years. The diameter at 1.3 m in height (dbh) was measured for each tree over 5.0 cm dbh, in ten sites, from 1992 to 2016. It was analyzed the quadratic mean diameter (Dq), the Dq annual periodic increment (APIDq), the Liocourt’s Quotient (q), and the diameter distribution with Meyer’s exponential model. The average APIDq over 24 years was 0.03 cm year-1, an average increase of 0.21%, with site variation ranging from 0.74% to -0.45%. The diameter distribution of the forest as a whole maintained the reverse J-shaped over 24-years. When the sites in each inventory year were analyzed, the variation in the diameter distribution was evident, and there were differences in the recovery capacity of the reverse J-shaped distribution from 1992 to 2016. The overall results indicate that, whenever possible, the management plan to recover the structure of the Atlantic Forest remnants should be site-specific, particularly in the mountainous region where the environmental conditions are quite diverse.

**摘要** 森林直径分布可为解析其生态过程提供科学依据，同时为森林保护、生物多样性提升、木材生产及碳固存等多重经营目标的落地提供支撑。本研究旨在探究24年间次生大西洋森林的直径分布随立地条件的变化规律。

研究于1992年至2016年间，在10个调查样地内对胸径（diameter at breast height, DBH）≥5.0 cm的所有林木进行胸径测量。分析指标涵盖二次平均直径（quadratic mean diameter, Dq）、Dq年定期生长量（annual periodic increment of Dq, APIDq）、李库尔特商数（Liocourt’s Quotient）以及基于迈耶指数模型（Meyer’s exponential model）的直径分布拟合结果。

24年间整体APIDq平均值为0.03 cm·年⁻¹，平均增长率达0.21%；各立地的APIDq变化范围为-0.45%至0.74%。整个研究区域的森林直径分布在24年监测周期内始终保持反J形分布特征。若按调查年份分别分析各立地的直径分布，则可见显著的分布差异，且1992年至2016年间各立地的反J形分布恢复能力存在明显分化。

综合研究结果表明，若要恢复大西洋森林残遗林分的结构，应尽可能采用立地特异性经营方案，在环境条件异质性较强的山地区域尤其需要如此。