Recommendations
Given the growing number of policies citing hydrological benefits of forest conservation in the tropics, there is a need for more tropical case studies of hydrological effects accompanying forest cover changes. Our contribution examines leaf wetness in relation to crop type and vegetation height to better understand hydrologic reactions to deforestation in premontane tropical systems with much higher (~5000 mm) annual precipitation than in previous studies. Although this insight about LWD was not directly compared to direct measures of canopy interception or evaporation, the great relevance of our findings for extremely moist environments justifies further study. Particularly in watersheds in tropical regions undergoing deforestation, there is a need for more detailed water budgeting between forests and agricultural land.
The additive hydrological effects at the watershed scale deduced from our results suggest broader landscape changes accompanying deforestation, although inherent complications exist from scaling between leaf-level and watershed-level effects (Jarvis, 1995). Furthermore, these results are more informative with intense removal of forest cover, since severe reductions in leaf area have more potential to alter interception. And yet relatively small canopy gaps similar to those found with selective logging led to drastically shorter drying times. LWD may not be as important in temperate climates, but in the humid tropics there is potential for this parameter to indicate an effect of deforestation on streamflow, as a relatively high interception of precipitation has been demonstrated (Wang et al., 2007, Good et al., 2017) compared to arid systems where soil evaporation accounts for more evaporation than intercepted precipitation (Cavanaugh et al., 2011). It is reasonable to assume that interception and LWD are positively related, and that post-rainfall evaporation is faster in lower stature vegetation than tall canopies. However, all else equal, LWD has the potential to actually reduce interception since storage turnover rates are lower. It is important to study LWD so it can be linked to storage to determine turnover.