COMPORTAMIENTO HIDROLÓGICO DE UN BOSQUE SEMI-SECO BAJO DIFERENTES INTENSIDADES DE ACLAREO EN CHIHUAHUA, MÉXICO.

RASCÓN RAMOS, ARGELIA EMELINA (2021) COMPORTAMIENTO HIDROLÓGICO DE UN BOSQUE SEMI-SECO BAJO DIFERENTES INTENSIDADES DE ACLAREO EN CHIHUAHUA, MÉXICO. Doctorado thesis, UNIVERSIDAD AUTONOMA DE CHIHUAHUA.

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Resumen

The understanding of hydrological processes in semi-dry forests is essential to evaluate the impact of forest management over water availability. The general objective was to analyze the changes in surface runoff and soil moisture of three micro-catchments with similar characteristics (0.19, 0.20, 0.27 ha), subject to different thinning intensities in a semi-dry forest in Chihuahua, Mexico. The specific objectives were analyzed in three studies: 1) to determine the most critical factors in the generation and amount of surface runoff during one rainy season prior to the application of thinning; 2) to analyze the soil moisture dynamics as a function of rainfall and evaluate the changes after three different thinning intensities (0 %, 40 % and 80 %); and 3) to analyze the runoff behavior in the micro-catchments before and after thinning. Vegetation, soil characteristics, precipitation and runoff were measured before (2018) and after thinning (2019). In the first study, it was found that maximum 30-min rainfall intensity, rainfall depth, and soil moisture were the main variables controlling surface runoff. Rainfall intensity was better related to the amount of surface runoff, with an increase in runoff when rainfall intensities were greater than 25 mm h-1. The highest runoff coefficients (10 %) occurred only when the intensity exceeded 30 mm h-1. The interception (36 %) and the drastic decrease in soil moisture suggest that more than 90 % of the rainfall was lost by evapotranspiration. The second study showed that soil moisture was low and similar among the three micro-catchments in 2018 (mean = 8.5 %), and only rainfall events > 30 mm increased soil moisture significantly (29-52 %). After thinning (2019), soil moisture was higher and significantly different among micro-catchments only during rainfall events <10 mm, while a difference was not noted during larger events. The third study revealed that runoff was low (mean coefficient = 1.7 %) and similar among micro-catchments before thinning (2018). Individual events showed differences in runoff among micro-catchments in 2019. The micro-catchment with the highest thinning intensity (80 %) presented greater runoff, followed by the intermediate thinning micro-catchment (40 %) and finally the micro-catchment without thinning. However, the distance between rainfall events led to a decrease in soil moisture, which generated inefficiency of thinning over runoff.

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