Rule-based analysis of throughfall kinetic energy to evaluate biotic and abiotic factor thresholds to mitigate erosive power

Abstract

Below vegetation, throughfall kinetic energy (TKE) is an important factor to express the potential of rainfall to detach soil particles and thus for predicting soil erosion rates. TKE is affected by many biotic (e.g. tree height, leaf area index) and abiotic (e.g. throughfall amount) factors because of changes in rain drop size and velocity. However, studies modelling TKE with a high number of those factors are lacking. This study presents a new approach to model TKE. We used 20 biotic and abiotic factors to evaluate thresholds of those factors that can mitigate TKE and thus decrease soil erosion. Using these thresholds, an optimal set of biotic and abiotic factors was identified to minimize TKE. The model approach combined recursive feature elimination, random forest (RF) variable importance and classification and regression trees (CARTs). TKE was determined using 1405 splash cup measurements during five rainfall events in a subtropical Chinese tree plantation with five-year-old trees in 2013. Our results showed that leaf area, tree height, leaf area index and crown area are the most prominent vegetation traits to model TKE. To reduce TKE, the optimal set of biotic and abiotic factors was a leaf area lower than 6700 mm2, a tree height lower than 290 cm combined with a crown base height lower than 60 cm, a leaf area index smaller than 1, more than 47 branches per tree and using single tree species neighbourhoods. Rainfall characteristics, such as amount and duration, further classified high or low TKE. These findings are important for the establishment of forest plantations that aim to minimize soil erosion in young succession stages using TKE modelling.

A new concept for estimating the influence of vegetation on throughfall kinetic energy using aerial laser scanning

“…However, for the relation of LAI and TKE inconsistent findings are described in previous studies. For example, Nanko et al () and Geißler et al () found a negative influence of LAI on TKE below trees larger than 15 m. Goebes et al () in contrast, found a positive correlation of LAI and TKE in an early‐successional forest plantation. These differences might result from differences in the vertical distribution of the leaf area, especially due to varying vegetation heights.…”

“…The crown base height (CBH) can be seen as ‘the last barrier' of the canopy (Goebes et al, ) determining the lowest falling height of drips. Although, CBH is found to be rather influential on TKE (Nanko et al, ; Goebes et al, ) it does not represent the whole vegetation: The presence of shrubs and other vegetation below the crown lead to re‐interception.…”

Throughfall drop size distributions: a review and prospectus for future research

“…This finding was later substantiated by others (e.g., Refs 9,11,19,43,and 57). Readers specifically interested in throughfall DSD and throughfall kinetic energy in relation to soil erosion are referred to Nanko et al, 21 Geißler et al, 24 and Goebes et al, 58 among others whose calculations of throughfall kinetic energy assume that the fall height of release throughfall is equal to the canopy height from which the droplets detach. 20,50,52,[59][60][61] In addition to its application to soil erosion studies, throughfall DSD is useful to estimate canopy interception loss.…”

Sediment Reallocations due to Erosive Rainfall Events in the Three Gorges Reservoir Area, Central China

“…In this context, soils inhere ecosystem functions that have direct impact on human societies (Berendse et al, 2015). Examples of these soil functions include water purification by filtration, food production by forming a support system for plants, stabilizing climate change by carbon sequestration and the provision of a physical basis for human activities (Keesstra et al, 2012;Goebes et al, 2015). However, soil erosion and the accompanied loss of topsoil result in soil quality degradation, and therefore in a declining capacity of soils to provide the ecosystem functions (Lal, 2003;Morgan, 2005;Boardman, 2006).…”