Forest Research Centre, Southern Cross University, Australia.
Silviculture Research Institute, Vietnam Academy of Forest Sciences, Ha Noi, Vietnam.
PLoS One. 2020 May 29;15(5):e0233524. doi: 10.1371/journal.pone.0233524. eCollection 2020.
Understanding the requirements and tolerances of the seedlings of climax species is fundamental for tropical forest restoration. This study investigates how the presence and abundance of seedlings of a previously dominant, now threatened species (Dipterocapus dyeri Pierre), varies across a range of environmental conditions. Dipterocapus dyeri seedling abundance and site characteristics were recorded at 122 observation points (4 m2) at nine clusters from two sites. Seedling presence (p = 0.065) and abundance varied significantly (p = 0.001) between the two sites, and was strongly correlated with adult D. dyeri dominance and lower soil pH, and weakly correlated with canopy openness and total stand basal area. Dipterocarpus dyeri seedlings were also grown in shade houses with three light levels on two soils. Seedling survival was significantly lower at the lowest light level (<10% full irradiance) at 13% for the forest soil and 25% for degraded soil. At higher irradiance the seedling survival rates were greater than 99%. Moisture levels remained high at the lowest light level and many seedlings died from fungal infection. We concluded that secondary forests which contain adequate numbers of adult D. dyeri as seed sources, light availability, soil pH of < 5.0, and good drainage strongly favour survival and growth of D. dyeri seedlings. Historically, D. dyeri was dominant in moist deciduous tropical forest across south-eastern Vietnam, but today it is rare. Active management of these recovering forests is essential in order to recover this high-value, climax forest species.
了解顶极物种幼苗的需求和耐受性对于热带森林恢复至关重要。本研究调查了先前占优势、现在受到威胁的物种（Dipterocapus dyeri Pierre）的幼苗在一系列环境条件下的存在和丰度如何变化。在两个地点的九个集群的 122 个观察点（4 m2）记录了 Dipterocapus dyeri 幼苗的丰度和地点特征。幼苗的存在（p = 0.065）和丰度在两个地点之间存在显著差异（p = 0.001），与成年 D. dyeri 的优势和较低的土壤 pH 值密切相关，与树冠开阔度和总林分基部面积弱相关。还在两个土壤上的三个光照水平的荫棚中种植了 Dipterocarpus dyeri 幼苗。在最低光照水平（<10%全光照）下，幼苗的存活率显著降低，森林土壤为 13%，退化土壤为 25%。在较高的辐照度下，幼苗的存活率大于 99%。在最低光照水平下，水分水平仍然很高，许多幼苗因真菌感染而死亡。我们得出结论，含有足够数量成年 D. dyeri 作为种子源的次生林、光照可用性、pH 值<5.0 和良好的排水条件强烈有利于 D. dyeri 幼苗的存活和生长。历史上，D. dyeri 在越南东南部的湿润落叶热带森林中占主导地位，但如今却很少见。为了恢复这种高价值的顶极森林物种，必须对这些正在恢复的森林进行积极管理。
