Nutrient fluxes in stemflow and throughfall in three successional stages of an upper montane rain forest in Costa Rica

Abstract

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.