Abstract
Abstract. 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 the potential for substantial interception by groundcover vegetation and surface litter. In this study, we developed an approach to quantify “total” interception (i.e., including forest canopy, understory, and surface litter layers) using measurements of shallow soil moisture dynamics during rainfall events. Across 34 pine and mixed forest stands in Florida (USA), we used soil moisture and precipitation (P) data to estimate interception storage capacity (βs), a parameter required to estimate total annual interception (Ia) relative to P. Estimated values for βs(mean βs=0.30 cm; 0.01≤βs≤0.62 cm) and Ia∕P (mean Ia/P=0.14; 0.06≤Ia/P≤0.21) were broadly consistent with reported literature values for these ecosystems and were significantly predicted by forest structural attributes (leaf area index and percent ground cover) as well as other site variables (e.g., water table depth). The best-fit model was dominated by LAI and explained nearly 80 % of observed βs variation. These results suggest that whole-forest interception can be estimated using near-surface soil moisture time series, though additional direct comparisons would further support this assertion. Additionally, variability in interception across a single forest type underscores the need for expanded empirical measurement. Potential cost savings and logistical advantages of this proposed method relative to conventional, labor-intensive interception measurements may improve empirical estimation of this critical water budget element.
Highlights
Rainfall interception (I ) is the fraction of incident rainfall stored by above-ground ecosystem structures and subsequently returned to the atmosphere via evaporation (E), never reaching the soil surface and never directly supporting transpiration (T ) (Savenije, 2004)
Direct measurements are often obtained from differences between total rainfall and water that passes through the canopy to elevated above-ground collectors plus water that runs down tree trunks during natural (e.g., Bryant et al, 2005; Ghimire et al, 2012, 2017) or simulated (e.g., Guevara-Escobar et al, 2007; Putuhena and Cordery, 1996) rainfall events
Plot-scale leaf area index (LAI) was moderately correlated with plot-mean βs, describing roughly 32 % of observed variation across plots (Fig. 4a)
Summary
Rainfall interception (I ) is the fraction of incident rainfall stored by above-ground ecosystem structures (i.e., vegetation and litter layers) and subsequently returned to the atmosphere via evaporation (E), never reaching the soil surface and never directly supporting transpiration (T ) (Savenije, 2004). Direct measurements are often obtained from differences between total rainfall and water that passes through the canopy to elevated above-ground collectors (throughfall) plus water that runs down tree trunks (stemflow) during natural (e.g., Bryant et al, 2005; Ghimire et al, 2012, 2017) or simulated (e.g., Guevara-Escobar et al, 2007; Putuhena and Cordery, 1996) rainfall events. This method yields the rainfall fraction held by and subsequently evap-
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