Diversity and structure of the lower strata in two successional stages in a subtropical forest, Southern Brazil

ABSTRACT Currently, in Paraná State, forest remnants in advanced successional stages account for less than 1% of its original area. This study compared the understory community across different successional stages of the Araucaria Forest in southern Brazil. Forest remnants, one in intermediate and another in advanced stage of natural regeneration were selected, and a total of 38 plots of 5 × 5 m were sampled. Individuals reaching at least 2 m high or having circumference up to 15 cm at height 1.3 m above the soil surface were measured and identified. In the forest at an intermediate stage, 68 species were recorded being mostly light-dependent, with Nectandra megapotamica as the most important species. On the other hand, at an advanced stage, less species were found (52 species) but most individuals were shade-tolerant, with Rudgea jasminoides as the most important species. These differences are most probably caused because of the canopy density of each fragment. As the comparison with other studies is impaired due to different plot sizes and inclusion criteria, we suggest the standardization to improve knowledge and support biodiversity conservation of the southern tropical forest of Brazil.

摘要 当前，巴西巴拉那州（Paraná State）内处于顶级演替阶段的森林残存斑块仅占其原始森林面积的1%以下。本研究针对巴西南部南洋杉林（Araucaria Forest）不同演替阶段的林下群落开展对比分析。研究选取两处分别处于自然演替中期与顶级阶段的森林残存斑块，共布设38个5×5米的样地进行采样。对株高至少达2米，或距地表1.3米处树干周长不超过15厘米的个体进行测量与物种鉴定。在演替中期的林分中，共记录到68个物种，其中以喜光物种占比最高，优势种为Nectandra megapotamica。与之相对，顶级演替阶段的林分中记录的物种数更少（52种），但多数个体为耐阴物种，优势种为Rudgea jasminoides。上述群落结构差异大概率源于各斑块的林冠郁闭度不同。由于不同研究间因样地尺寸与物种纳入标准存在差异，导致跨研究对比存在一定困难，因此本研究建议统一标准化研究方法，以深化对巴西南部热带森林的认知，并为其生物多样性保护提供科学支撑。