Interception of Tropical Rain Forest: Performance of a Canopy Water Balance Model

Abstract

The throughfall in dry evergreen forest and mixed forest in central Guyana (South America) was measured over a period of 17 months using both a moving and a fixed stratified random sampling scheme. The throughfall, stemflow and canopy cover fractions of the two forest types were not significantly different. The data set was used to test the canopy water balance model designed by Rutter et al. (1971). Compared with both forest types, the model underestimated the total interception fraction: 13.4% for the Rutter model as opposed to 17.3 and 16.0% of the rainfall for dry evergreen forest and mixed forest. This was caused by a severe underestimation of interception on days with a rainfall of more than approximately 10 mm. Compared with the rainfall frequency distribution of the area, accurate model results were obtained for 20% of the rainfall only. Sensitivity analysis shows that an increase of saturation storage capacity or potential evaporation by 150% will give an acceptable accumulated interception, but that this is caused by large overestimation on days with a low amount of rainfall. The Rutter model was extended with a layered representation of the canopy, with simulation of the microclimate, but using basically the same input data. This resulted in a higher total interception fraction (16.3% of the rainfall), especially in the range 5–20 mm/day, because of a larger storage at the start of each rainstorm and an increased surface available for evaporation.

Estimating spatial patterns of rainfall interception from remotely sensed vegetation indices and spectral mixture analysis

“…All in all, this often results in a large variability and uncertainty of interception estimates, especially for natural vegetation, even for the same vegetation type and/or plant species. Jetten (1996), for instance, finds average annual interception losses for two tropical forest types of 0.21 with standard errors of 0.1, which is similar to the findings of Fritch (1990) in French Guyana and Lloyd et al (1988) in Brazil. Values for crops and orchards that are usually more homogeneous may show less variability.…”

The importance of epiphytes to total rainfall interception by a tropical montane rain forest in Costa Rica

“…Three other forests in the latter area exhibited canopy capacities of 1.16 -1.32 mm, corresponding with LAI values of 4.4 -5.5 m 2 m 22 (Tobón-Marin, 1999). Therefore, although the presently derived LAI is (much) higher than those of any of the cited lowland forests, the corresponding canopy storage capacity associated with the leaves of the overstorey trees in the Talamancan forest is very similar to the average of 1.12 mm derived for these and other Amazonian forests (Elsenbeer et al, 1994;Jetten, 1996). Because differences in forest structure are already incorporated to some extent through the use of the LAI, it is likely that the difference in leaf water holding capacity is largely due to differences in methodology.…”

Quantifying rainfall and cloud water interception in upland forests of Norfolk Island

“…Forest canopy coverage can be quite variable making the measurement of throughfall complicated. Other forest studies have used roving gauges (e.g., Jetten, 1996; Shuttleworth, 1988) or large numbers of rain gauges (e.g., Hölscher et al, 2004; Holwerda et al, 2006) to account for this variation but this was not feasible in this study due to the remoteness of the location and requirement for long‐term observations. Following the approach of McJannet, Wallace, and Reddell (2007a) we deployed a series of trough systems at each site.…”