Evidence of longer baseflow recession times following extensive forest regeneration in Puerto Rico

Abstract:

Secondary forests account for 70% of the total forested land in the tropics (FAO, 2010). Yet despite their prevalence, there remains a dearth of knowledge regarding the impact of secondary forests on ecological services, particularly on watershed-scale hydrology (Ellison et al., 2012; Poorter et al., 2016). This is due largely to the lack of long-term observational hydro-climate data in the tropics (Wohl et al., 2012). Given the importance of tropical hydrology to regional and global hydro-climatic interactions, advancing the understanding of how anthropogenic changes impact streamflow at the watershed scale in the humid tropics is crucial.

In this study, 60 years of hydro-climate data and two land cover maps from Puerto Rico, where extensive forest regeneration has occurred, were used to investigate the impact of land cover change on streamflow from 15 mesoscale watersheds. Reforestation was not found to significantly impact total yearly streamflow and baseflow in the studied watersheds, although there was a non-statistically-significant positive relationship between these factors. Baseflow recession times, however, were found to have increased in the most reforested watersheds and decreased in the most urbanized watersheds, providing evidence that land cover changes have likely altered the response of the studied watersheds – with potentially greater soil infiltration and recharge in reforested watersheds leading to greater baseflow and longer recession times. This finding illustrates the importance of considering both water yields and recession behavior in quantifying the effects of land change on streamflow and may prove useful for future research as well as policies.