Canopy Interception for a Tallgrass Prairie under Juniper Encroachment

Abstract

Rainfall partitioning and redistribution by canopies are important ecohydrological processes underlying ecosystem dynamics. We quantified and contrasted spatial and temporal variations of rainfall redistribution for a juniper (Juniperus virginiana, redcedar) woodland and a tallgrass prairie in the south-central Great Plains, USA. Our results showed that redcedar trees had high canopy storage capacity (S) ranging from 2.14 mm for open stands to 3.44 mm for closed stands. The canopy funneling ratios (F) of redcedar trees varied substantially among stand type and tree size. The open stands and smaller trees usually had higher F values and were more efficient in partitioning rainfall into stemflow. Larger trees were more effective in partitioning rainfall into throughfall and no significant changes in the total interception ratios among canopy types and tree size were found. The S values were highly variable for tallgrass prairie, ranging from 0.27 mm at early growing season to 3.86 mm at senescence. As a result, the rainfall interception by tallgrass prairie was characterized by high temporal instability. On an annual basis, our results showed no significant difference in total rainfall loss to canopy interception between redcedar trees and tallgrass prairie. Increasing structural complexity associated with redcedar encroachment into tallgrass prairie changes the rainfall redistribution and partitioning pattern at both the temporal and spatial scales, but does not change the overall canopy interception ratios compared with unburned and ungrazed tallgrass prairie. Our findings support the idea of convergence in interception ratio for different canopy structures under the same precipitation regime. The temporal change in rainfall interception loss from redcedar encroachment is important to understand how juniper encroachment will interact with changing rainfall regime and potentially alter regional streamflow under climate change.

Relationships between rainfall and throughfall in a secondary forest in southeastern Brazil: an evaluation of different statistical models

“…The following models were tested: linear (Equation 1); power (Equation 2) (STAELENS et al, 2006(STAELENS et al, , 2008; logarithmic (Equation 3) (ZOU et al, 2015); and exponential (Equation 4) (CARLYLE-MOSES; LAUREANO;PRICE, 2004).…”

“…In addition, it is also possible to obtain parameters for the modelling of other hydrological processes from linear models (PYPKER et al, 2005;ZOU et al, 2015), such as canopy water storage capacity, the fraction of direct TF, amongst others. For example, the inverse value of the parameter a obtained by the linear model in the present study (Table 2) represents the canopy water storage capacity, indicating the RF depth needed to saturate the canopy and promote TF (LORENZON; DIAS; LEITE, 2013;STAELENS et al, 2008;TONELLO et al, 2014).…”

“…In contrast, when throughfall is considered in terms of percentage of rainfall (TF % ), the relationship between the variables is not linear (ZOU et al, 2015). Fan et al (2015) observed that the increase of rainfall depth positively affects TF % until a threshold where no further increases are detected.…”

“…However, these models incorporate some degree of uncertainty in their inferences, due to the simplification of systems (i.e., non-incorporation of all influencing factors) (CARIBONI et al, 2007). Despite its importance, few studies evaluating the adjustment of nonlinear models to describe the relationship between rainfall and throughfall estimates were carried out (CARLYLE-MOSES; LAUREANO; PRICE, 2004;ZOU et al, 2015). The identification of these patterns in empirical studies highlights the need for studies that address this gap, improving the understanding of how these variables interact with each other.…”

“…When the interactions between these variables are established, it is possible to model other associated hydrological processes (i.e. canopy interception) (PYPKER et al, 2005;ZOU et al, 2015) and to define strategies for sampling throughfall with smaller errors in the estimates (CARLYLE-MOSES; LAUREANO; PRICE, 2004;MCKEE, 2014;HOLWERDA;SCATENA;BRUIJNZEEL, 2006;RITTER;REGALADO, 2014;RODRIGO;ÀVILA, 2001;SARI;PAIVA;PAIVA, 2015;ZIEGLER et al, 2009). Thus, knowledge of the characteristics and dynamics of hydrological processes in forest ecosystems can provide subsidies for more efficient watershed management, in order to guarantee the water supply in quantity and quality necessary for human activities.…”