@corresponding author: lauralozano@csic.es
Abstract. Forest degradation is increasingly recognized as a
major threat to global biodiversity and ecosystems’ capacity to provide
ecosystem services. This study examined the impacts of forest
degradation on soil quality and function in a seasonally dry tropical
forest (SDTF) of Ecuador. We compared soil physical-chemical properties,
enzymatic activity, particulate organic carbon (POC) and
mineral-associated organic carbon (MAOC) along a gradient of SDTF
degradation in the dry and rainy season. Our findings showed a
consistent and steady reduction in soil quality (total C and N) and
function (dehydrogenase and β-glucosidase activity) that paralleled the
loss of vegetative structure and diversity along the degradation
gradient. Soil physical-chemical properties were less variable and
enzymatic activity was generally higher in the dry season compared to
the rainy season. We also showed for the first time a significant and
uniform decrease in POC and MAOC with ecosystem degradation in a SDTF.
The relative proportion of these two components was constant along the
gradient except for the most degraded state (arid land), where POC was
higher in proportion to MAOC, suggesting that a functional tipping point
may be crossed with extreme forest degradation. These findings address
an important knowledge gap for SDTFs by showing a consistent loss of
soil quality and functionality with degradation and suggest that extreme
degradation can result in an alternate state with compromised
resilience.
Keywords (max 6): forest degradation; seasonally dry tropical
forest; soil function; enzyme activity; POC; MAOC