5. Conclusions
Forest degradation is increasingly recognized as a major threat to global biodiversity and ecosystems’ capacity to provide ecosystem services. This study contributes to our understanding of the impacts of forest degradation on soil quality and function in SDTFs. Whereas previous studies of this ecosystem have focused on the effects of land-use conversion on soils, particularly agriculture, our study is among the first to examine soil impacts of forest degradation resulting from chronic disturbance. The effects of forest degradation might not be as obvious as those from deforestation, but understanding them is as important for ensuring ecosystem integrity and resilience as fathoming the impacts of land-use change.
Our findings showed a consistent and steady reduction in soil quality and function that paralleled the loss of vegetative structure and diversity along a gradient of SDTF degradation. Above and belowground conditions were clearly linked in the different forest states and between seasons. This implies that while degradation can drive the loss of soil C, N and enzymatic activity through the depletion of vegetation biomass and richness, well-designed restoration strategies can help reverse those losses.
The case of arid land, however, suggests that extreme forest degradation could lead to an alternate state in which critical biochemical pathways cease to function. Diminished soil quality, low enzymatic activity, and a high POC/MAOC ratio suggested that this state lies beyond a critical threshold of ecosystem resilience and requires serious intervention to recover soil functionality. The question as to whether continued disturbance to this state would lead to desertification requires urgent attention.