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Epiphytic biomass, canopy humus and associated canopy water storage capacity are known to vary greatly between old-growth tropical montane cloud forests but for regenerating forests such data are virtually absent. The present study was conducted in an old-growth cloud forest and in a 30-year-old secondary forest (SF) on windexposed slopes in the Cordillera de Tilará n (Monteverde area) in northern Costa Rica. Epiphytic vegetation in both forests was dominated by bryophytes. Epiphyte mat weight (epiphyte biomass and canopy humus) at the stand level was 1,035 kg ha -1 in the SF and 16,215 kg ha -1 in the old-growth forest (OGF). The water contents of epiphytic bryophytes in the OGF were determined gravimetrically in situ and showed maximum values of 418% ± 74 (SD)% of dry weight and minimum values of 36% ± 10 (SD)%. Maximum stand water storage of non-vascular epiphytes and canopy humus at Monteverde was estimated at 0.36 mm for the SF and 4.95 mm for the OGF. Epiphytic bryophytes exhibited more dynamic wetting and drying cycles compared to canopy humus. Maximum water loss through evaporation was 251% of dry weight (bryophytes) and 117% of dry weight (canopy humus) within 3 days of sunny weather without precipitation. Despite the high potential water storage capacity of epiphytic bryophytes and canopy humus the actually available storage is likely to be much smaller depending on antecedent rainfall and evaporative conditions.

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Nutrient fluxes in stemflow and throughfall were compared among three successional stages of an upper montane rain forest and related to structural characteristics of the stands (stem density, leaf area, epiphyte abundance). An old-growth forest stand, an early successional (10-y-old) forest stand and a mid-successional (40-y-old) forest stand were studied in the Cordillera Talamanca, Costa Rica. All three sites were dominated by Quercus copeyensis with a variable admixture of other tree species. There was no difference in the average stand leaf area index between the old-growth forest and the early successional forest. A significantly higher leaf area was found in the mid-successional forest. There were large differences in litterfall from non-vascular epiphytes (mosses, liverworts and lichens) which reflected differences in epiphyte abundance, with highest values in the old-growth forest. Total nutrient transfer via stemflow and throughfall from the canopy to the soil showed only minor differences among the stands. The stands differed widely in the ratio of nutrient transport via stemflow to the total nutrient flux by water below the canopy. The K flux with stemflow accounted for 5% of the total in the old-growth forest but it accounted for 17% (early successional forest) and 26% (mid-successional forest) in the secondary forests. It is concluded that differences in canopy structure and epiphyte abundance in old-growth and secondary forests resulted in large differences in the partitioning of nutrient transport into stemflow and throughfall components although total nutrient transfers via water reaching the soil were similar.

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Tropical upper montane forests usually comprise trees of small stature with a relatively low aboveground productivity. In contrast to this rule, in the Cordillera de Talamanca (Costa Rica), tall trees ([35 m in height and more than 60 cm in diameter) are characteristic for the upper montane old-growth oak forests which are growing at an altitude of almost 3,000 m close to the alpine timberline. For these exceptional forests, productivity data are not yet available. In this study, we analyzed litterfall and its components (tree leaves, litter of epiphytic vascular and non-vascular plants, mistletoes, twigs and other canopy debris) in three forest stands belonging to different successional stages and related seasonal changes in litterfall to micrometeorological variables. The studied stands were early-successional forest (10-15-year-old), mid-successional forest (40-year-old), and old-growth forest. The stands are dominated by Quercus copeyensis and are located at 2,900-m altitude. Total litterfall was highest in the mid-successional forest (1,720 g m -2 y -1 ), and reached 1,288 g m -2 y -1 in the old-growth forest and 934 g m -2 y -1 in the earlysuccessional forest. Litter mass was dominated by leaves in all stages (56-84% of total litterfall). In the oldgrowth forest, however, twigs and small canopy debris particles (33%), epiphytes (6%), and mistletoes (5%) also contributed substantially to litter mass. Leaf litterfall showed a clear seasonal pattern with a negative correlation to monthly precipitation and highest values in the dry season (January-April). However, the strongest correlation existed with minimum air temperature (negative), probably because temperatures already dropped at the end of the rainy season, when precipitation had not yet declined and leaf shedding already increased. In contrast, litterfall of epiphyte mass, and twigs and other debris was mostly dependent on occasional strong winds. We conclude that the upper montane oak forests of the Cordillera de Talamanca are exceptional with respect to the large tree size and the relatively high productivity as indicated by litterfall. Litter mass was especially high in the mid-successional and old-growth forests, where the observed annual totals are among the highest recorded for tropical forests so far.

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