Dynamics of gaps and large openings in a secondary forest of Northeast China over 50years

摘要

Key messageThe gap dynamics in the studied secondary forest were comparable to those of other temperate forests; large openings were filled within 30years by afforestation; large and medium gaps closed 30-40years after they formed.ContextGaps have important roles in forest regeneration and plant succession. However, it is difficult to determine gap dynamics over long time periods at regional scales.AimsWe studied how the dynamics of gaps and large openings (oversized gaps) changed in a secondary temperate forest over 50years.MethodsWe computed the dynamic indices of gaps (16-3257m(2)) and large openings (>3257m(2)) using remote sensing techniques applied to six satellite images that were taken approximately every 10years. Additionally, number-based gap closure ratios were calculated at each interval.ResultsGap dynamics were comparable in magnitude to those calculated for other temperate forests, and 60% and 53% of the large and medium gaps had closed within 30-40 and 20-30years, respectively. The small gaps closed within 10years, based on ground-level surveys, and 79.2% of large openings that existed in 1964 were covered by artificial forests in 1994.ConclusionGaps of different sizes closed within 40years due to natural regeneration. Large openings had closed within 30years via afforestation. These findings can be used for evaluating recovery status and for predicting succession times in secondary forest structures driven by gap formation.