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.