Combining chronosequences and multi-census approaches to understand patterns of succession in subtropical montane forests of NW Argentina

Question

How does the diversity of successional forests evolve with stand age, and to what extent do permanent plots validate the previously studied successional patterns of tree diversity and composition observed through chronosequences? To evaluate the role of successional forests as reservoirs for many species, it is essential to examine how biodiversity recovers with the age of the stand. We studied patterns of taxonomic and functional diversity, as well as species composition during forest succession, by combining chronosequences and permanent plot monitoring.

Location

Subtropical montane forests in NW Argentina.

Methods

We used data from two chronosequences of plots monitored for 30 years in lower and upper montane forests dominated by native trees (LMF-Native and UMF-Native), and one chronosequence of plots dominated by the exotic tree Ligustrum lucidum, monitored for 10 years in low montane forests (LMF-Invaded). We analyzed changes in taxonomic (species richness, Shannon diversity, Simpson diversity) and functional diversity, as well as composition with forest age.

Results

Taxonomic and functional diversity increased between 30 and 70 years of succession in LMF-Native and UMF-Native. Successional LMF-Native forests reached the diversity of mature forests earlier than UMF-Native. In LMF-Invaded, taxonomic and functional diversity decreased in the same period because of the increasing dominance of the exotic species Ligustrum lucidum. In non-invaded chronosequences (LMF-Native and UMF-Native) we observed a convergence towards the composition of mature forests; however, each successional forest kept its identity for 30 years.

Conclusions

Diversity and composition followed different successional trajectories depending on the type of forest. We found that successional patterns, such as changes in taxonomic and functional diversity, predicted with the chronosequence approach, were confirmed with data from plot monitoring. The effects of pre-abandonment conditions persist in the diversity and composition of successional forests monitored between 10 and 30 years.