Temporal persistence of throughfall heterogeneity below and between the canopies of juvenile lodgepole pine (Pinus contorta)

Abstract

AbstractFrom May to October 2010, throughfall associated with 38 rainfall events in three below‐canopy zones (inner canopy, mid‐canopy and canopy periphery) of nine juvenile lodgepole pine trees and in open areas between canopies was measured along north, south, east and west transects radiating from each tree bole. Median cumulative throughfall (%) significantly differed among the canopy zones under differing rain depth classes and was negatively correlated with tree size metrics, but only for certain combinations of canopy zones and rain depth classes. Although median cumulative throughfall (%) was negatively correlated with canopy cover fraction when all below‐canopy gauges were considered, this relationship only held true for the inner‐canopy and mid‐canopy zones under relatively small rain depth classes. Additionally, cumulative throughfall (%) was often dependent on transect direction, with event throughfall showing a dependence on the direction of storm origin. Throughfall coefficient of variation (%) also varied by zone and was a function of not only rainfall depth but also other storm variables such as the maximum 30‐min rainfall intensity and the number and duration of intra‐storm breaks. Temporal persistence of throughfall was assessed using time stability plots and Spearman rank coefficients of rain event and depth class pairings for all gauges and by canopy zone, and the influence of temporal lag and meteorological variables on persistence was assessed. The implications of our findings on throughfall sampling and for future ecohydrological studies in juvenile lodgepole pine and similar stands are discussed. Copyright © 2015 John Wiley & Sons, Ltd.