Abstract
The active effect of natural regeneration on understory vegetation and diversity on clear-cut forestlands, in contrast to conifer reforestation, is still controversial. Here we investigated differences in understory vegetation by comparing naturally regenerated deciduous forests (NR) and reforested spruce plantations (SP) aged 20–40 years on 12 similar clear-cuts of subalpine old-growth spruce-fir forests from the eastern Tibetan Plateau. We found that 283 of the 334 vascular plant species recorded were present in NR plots, while only 264 species occurred in SP plots. This was consistent with richer species, higher cover, and stem (or shoot) density of tree seedlings, shrubs, and ferns in the NR plots than in the SP plots. Moreover, understory plant diversity was limited under dense canopy cover, which occurred more frequently in the SP plots. Our findings implied that natural deciduous tree regeneration could better preserve understory vegetation and biodiversity than spruce reforestation after clear-cutting. This result further informed practices to reduce tree canopy cover for spruce plantations or to integrate natural regeneration and reforestation for clear-cuts in order to promote understory vegetation and species diversity conservation.
Highlights
Species composition, diversity, and structure of understory vegetation are keys to providing complex structure and conserving indigenous floras within forests [1,2]
We addressed three questions: (1) Which regeneration strategies result in higher vascular plant diversity in the forest understory: natural regeneration or spruce reforestation? (2) How do the vascular plant groups differ in species composition, richness, and community structure between the understory of the two forests? (3) What are the differences in structures of the overstory and understory and their relationships between the two forests? We hypothesized that: (H1) The naturally regenerated forests would host higher species diversity compared to the planted spruce forests, with woody plant diversity being the key driver of the diversity difference; and (H2) the tree canopy structure of the two forests disparately influences the structure and species diversity of the understory
We implemented the current study to compare the understory structure and vascular plant diversity between the naturally regenerated deciduous forest and the reforested spruce plantation with similar age, following the same clear-cut logging of old-growth spruce-fir forests in the eastern Tibetan Plateau
Summary
Diversity, and structure of understory vegetation are keys to providing complex structure and conserving indigenous floras within forests [1,2]. The understory community and biodiversity are focal objectives for sustainable forest management, effective forest biodiversity conservation, and successful forest restoration [4,6,9]. The effects of different strategic applications for forest regeneration on understory vegetation and species diversity on clear-cuts remains controversial, advocating further study [9,10,11,12]. It is a challenge for forest managers to promote forest regeneration, while conserving indigenous biodiversity in a large area of clear-cut forestlands. Natural regeneration and conifer reforestation on clear-cuts are two major regeneration strategies that have been long employed in the northwestern Sichuan Province, China [13], and globally [14]
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