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This study had as objectives to: 1) estimate interception loss, 2) relate the
interception loss parameters to the dasometric characteristics of the plant community,
and 3) to fît the analytical interception loss model of Gash to observed interception loss
in four characteristic plant communities of northeastern Mexico. Gross rainfall,
throughfall and stemflow were measured from April 1997 to April 1998 for the
tamaulipan thornscrub plant community and from May 1997 to April 1998 for the
coniferous forests of the Eastern Sierra Madre. Gross rainfall was measured in a
rainguage, throughfall in four throughs in each sampling plot and 12 throughs in plots of
coniferous forests. Stemflow was measured in six pots and collars installed to each of
six shrubs and six trees of the thamaulipan thornscrub and coniferous forests,
respectively. Interception loss parameters were estimated by regression analysis and
tested by differences between sampling plots by a covariance analysis, where gross
rainfall was the covariate. Interception loss model of Gash was validated with an
independent data set. To fit the model parameters two sets of data were utilized, with 27
and 29 rains and to test the goodness of fit, 8 and 10 rains were used for the tamaulipan
thornscrub and the coniferous forests of the eastern Sierra Madre, respectively. The
results showed that sampling plots had statistical differences to interception loss and
stemflow. Stemflow was also statistically different among sampled plant species and
between shrubs of the same plant species. Total interception loss and stemflow were
statistically related to total plant cover, stem diameter ad total tree height. The model of
Gash fitted well obsereved interception loss because the difference between observed
and estimated was not greater than 4 mm or 3.5% of the total rainfall. The results for the
coniferous forests of the eastern Sierra Madre did not show statistical differences to net
rainfall (P>F=0.6500), throughfall (P>F=0.6405), but to stemflow (P>F=0.0001).
Stemflow was also different between trees of genus Pinus (P>F=0.0001) and Quercus
(P>F=0.0001) and it was related to canopy cover, tree diameter and total height. The
model of Gash also fitted well observed interception loss of coniferous forests because
their difference was not larger than 3 mm or 2.8% for the rains of fitting parameters and
validating the model. The sensitivity analysis of Gash model showed that parameters S
(water storage in canopies) and a (the slope of the relationship between interception loss
and gross rainfall) had the largest deviations in total estimated interception loss. It is