Rainfall and fog interception at the lower and upper altitudinal limits of cloud forest in Veracruz, Mexico

摘要

Comparisons of rainfall and fog interception among different types of tropical mon-tane cloud forest usually reveal large differences, but the variation in these processes within a given forest type has rarely been studied. In the present study, the altitudinal variation of rainfall (I-p) and fog (I-f) interception was investigated for a lower mon-tane cloud forest in central Veracruz, Mexico. For this, rainfall (P), net rainfall, fog presence (visibility), and meteorological variables were measured in the "Santuario" natural reserve (1,300 m asl) during two sampling periods that were representative of the dry and wet seasons, respectively. In addition, the canopy water storage capacity (C-m) was determined. The results were then compared with data published for the "Cortadura" reserve (2,170 m). There was no evidence of I-f in Santuario, whereas it was estimated at 8% of the dry-season P in Cortadura. In Santuario, relative I-p was 22% and 9% of P during the dry and wet seasons, respectively (compared with 20% and 18% of P, respectively, in Cortadura). Average rainfall event size and C-m were the main factors determining the relative I-p at both sites. C-m was much lower in Santuario (1.0 mm) than in Cortadura (3.9 and 2.8 mm in the wet and dry seasons, respectively). However, because during the dry season the average rainfall event size was much lower in Santuario, relative I-p was similar between sites. In contrast, during the wet season, the average event size was similar between sites, so that the difference in C-m caused an important altitudinal variation in relative I-p.