Soil Respiration Is Influenced by Seasonality, Forest Succession and Contrasting Biophysical Controls in a Tropical Dry Forest in Northwestern Mexico

Soil respiration (R-S) is an important component of the C cycle because it contributes significant CO2 emissions to the atmosphere that result from metabolism and respiration of its autotrophic and heterotrophic components. However, the relative importance of different biophysical controls that drive the variability of this flux and their influence along forest succession pathways is still unknown. We incorporate multiyear R-S, ecosystem flux and meteorological measurements in old-growth (OG), mid-secondary (MS) and early-secondary (ES) tropical dry forests (TDFs) with the goal of assessing the temporal variation of R-S and identifying the biophysical controls at each site by applying structural equation models (SEM). Along forest succession, R-S followed the pattern of precipitation events; we identified by the end of the wet season that R-S was sustained by a longer period at OG, while in MS and ES, R-S decreased according to the soil moisture availability. According to SEM, soil moisture and soil temperature exert an effect on the variability of R-S in all sites. However, we found that R-S was also controlled by the vapor pressure deficit at MS and gross primary production at OG and ES. Our results suggest that seasonality has a different impact on R-S along forest succession in TDFs found in northwestern Mexico and highlights the relevance of considering additional biophysical controls of R-S for a better understanding this critical process of the C cycle.