Effects of thinning on functional and phylogenetic diversity of regenerated woody plants in plantations over time

Aims

Conversion of natural mixed forests into monoculture plantations results in a loss of biodiversity, and consequently leads to serious ecological problems (e.g. soil acidification and soil fertility declines) by controlling the quantity and quality of litter entering the soil. Plant diversity in the understorey is the most important component of aboveground biodiversity in plantations and plays a critical role in the sustainable development of plantations. Thinning has been proven effective in promoting the regeneration of understorey plants, and most studies have targeted the effects of thinning on a single biodiversity index (e.g. species richness) of the understorey in plantations. The effects of thinning on functional and phylogenetic diversity are less addressed, however, which could limit the full understanding of biodiversity maintenance and potential processes of community assembly integrally in plantations after thinning.

Location

Northeast China.

Methods

We chose young and middle-aged larch (Larix kaempferi) plantations based on the time after thinning (short term, 1–3 years; medium term, 4–9 years; and long term, 10 years or longer), quantified the functional and phylogenetic diversity and the structure of regenerated woody plants in the understorey, and related the functional and phylogenetic diversity to environmental factors (canopy openness and soil nutrients).

Results

Functional richness and evenness decreased over time after thinning in two types of plantations, and in the medium term the functional divergence of young plantations was significantly lower. At short term after thinning, the phylogenetic diversity was higher in two types of plantations. Functional richness was significantly related to canopy openness in young plantations, while functional divergence was closely related to soil phosphorus content in middle-aged plantations. Functional and phylogenetic structure of the regenerated woody community changed from dispersion to clustering and had a significant relationship with environmental conditions (e.g. light availability in both young and middle-aged plantations), highlighting that environmental filtering gradually became the main driving force of community assembly in the regenerated community of the understorey.

Conclusion

The functional and phylogenetic diversity of regenerated woody plants changed over time after thinning under the influence of light availability, and environmental filtering played a crucial role in the assembly of the understorey community. Our study expands the research of biodiversity maintenance by considering the effects of thinning over time, and provides new insights into the management and sustainable development of plantations.