Estimating Interception from Near-Surface Soil Moisture Response

Subodh Acharya, Daniel McLaughlin, David Kaplan, Matthew J. Cohen
2019 Hydrology and Earth System Sciences Discussions  
<p><strong>Abstract.</strong> Interception is the storage and subsequent evaporation of rainfall by above-ground structures, including canopy and groundcover vegetation and surface litter. Accurately quantifying interception is critical for understanding how ecosystems partition incoming precipitation, but it is difficult and costly to measure, leading most studies to rely on modeled interception estimates. Moreover, forest interception estimates typically focus only on canopy storage, despite
more » ... y storage, despite the potential for substantial interception by groundcover vegetation and surface litter. In this study, we developed an approach to quantify <q>total</q> interception losses (i.e., including forest canopy, understory, and surface litter layers) using measurements of shallow soil moisture dynamics during rainfall events. Across 36 pine and mixed forest stands in Florida (USA), we used soil moisture and rainfall data to estimate the interception storage capacity (<i>β</i><sub><i>s</i></sub>), a parameter required to estimate total annual interception losses (<i>I</i><sub><i>a</i></sub>) relative to rainfall (R). Estimated values for <i>β</i><sub><i>s</i></sub> (mean <i>β</i><sub><i>s</i></sub>&amp;thinsp;=&amp;thinsp;0.30&amp;thinsp;cm; 0.01&amp;thinsp;≤&amp;thinsp;<i>β</i><sub><i>s</i></sub>&amp;thinsp;≤&amp;thinsp;0.62&amp;thinsp;cm) and <i>I</i><sub><i>a</i></sub>/<i>R</i> (mean <i>I</i><sub><i>a</i></sub>/<i>R</i>&amp;thinsp;=&amp;thinsp;0.14; 0.06&amp;thinsp;≤&amp;thinsp;<i>I</i><sub><i>a</i></sub>/<i>R</i>&amp;thinsp;≤&amp;thinsp;0.21) were consistent with reported literature values for these ecosystems and were significantly predicted by forest structural attributes (leaf area index and percent groundcover), as well as other site variables (e.g., water table depth). The best-fit model was dominated by LAI and explained nearly 80&amp;thinsp;% of observed <i>β</i><sub><i>s</i></sub> variation. These results suggest that whole-forest interception can be measured using a single near-surface soil moisture time series and highlight the variability in interception losses across a single forest type, underscoring the need for expanded empirical measurement. Potential cost savings and logistical advantages of this method relative to conventional, labor-intensive interception measurements may improve empirical estimation of this critical water budget element.</p>
doi:10.5194/hess-2019-157 fatcat:skzx5clwabeizn2oavfzehwxaa