Precipitation partitioning and related nutrient fluxes in a subtropical forest in Okinawa, Japan

Abstract

-Precipitation partitioning into throughfall and stemflow and related hydrochemical fluxes were examined during a 3 y period from January 1998 to December 2000 in a subtropical evergreen broad-leaved forest on Okinawa Island, Japan. Monthly water samples were collected to determine the concentrations and associated fluxes of bioelements. The mean annual precipitation during the study period was 3325 mm. Typhoons played a central role in the hydrology of the study forest with 11 typhoons contributing 29.1% of the total rainfall over the 3 y period. Throughfall and stemflow contributed 53.9% and 30.9% of the annual rainfall, respectively, implying a rainfall interception of 15.2%. The very high fraction of stemflow could be due to the crown morphology of the dominant species, Castanopsis sieboldii, that has inclined branches and concave shaped leaves. Mean pH in the precipitation was 6.22, and decreased significantly as the water passed through the canopy. Concentrations of total N, DOC, K, Na, Ca, and Mg showed a clear pattern of enrichment in both throughfall and stemflow compared to rainfall. The proximity to the Pacific Ocean strongly influenced the nutrient fluxes via rainfall at our site as illustrated by the extremely high Na fluxes via rainfall (213 kg Na ha -1 y -1 ) and throughfall plus stemflow (291 kg Na ha -1 y -1 ). The mean annual nutrient inputs (in kg ha -1 ) were: total N 43, P 2.6, K 76, Ca 49, Mg 30, Na 291, Al 1.8, Fe 1.0, and Mn 1.1. The input of DOC reached 361 kg C ha -1 y -1 . The high nutrient inputs via net precipitation (throughfall plus stemflow) especially for N at our site is thought to reflect the frequent occurrence of sea salt-induced stress and serious herbivory by insect.Castanopsis sieboldii / dissolved organic carbon / evergreen broad-leaved forest / nutrient cycling / stemflow / throughfall Résumé -Partition des précipitations et flux de nutriments dans une forêt subtropicale d'Okinawa au Japon. La partition des précipitations entre eau arrivant directement au sol et écoulement le long des troncs et flux hydrochimiques liés a été étudié pendant 3 ans de janvier 1998 à décembre 2000 dans une forêt feuillue à feuilles persistantes de l'île d'Okinawa au Japon. Mensuellement des échantillons d'eau étaient collectés pour déterminer les concentrations et les flux des bioéléments. Les précipitations annuelles moyennes pendant la période étudiée ont atteint 3325 mm. Les typhons jouent un rôle central dans l'hydrologie de la forêt étudiée avec 11 typhons contribuant à 29,1 % des précipitations totales pour les 3 ans de la période d'étude. L'eau arrivant directement au sol et l'écoulement le long des troncs représentent respectivement 53,9 % et 30,9 % des précipitations incidentes annuelles, impliquant une interception des précipitations de 15,2 %. La part importante de l'écoulement le long des troncs pourrait être dû à la morphologie des couronnes de l'espèce dominante Castanopsis sieboldii qui a des branches inclinées et des feuilles de formes concaves. Le pH des précipitati...

Dissolved organic carbon in water fluxes of Eucalyptus grandis plantations in northeastern Entre Ríos Province, Argentina

“…A similar trend of total DOC increment in the sequence from precipitation to throughfall and stemflow observed in the E. grandis plantation was reported for some forests too (Moreno et al 2001, Xu et al 2005. However, the magnitude among fluxes differed significantly, since in the E. grandis plantation DOC concentrations in throughfall and stemflow were 3.2 and 33.4 times respectively higher as those in the precipitation, meanwhile, for example, Xu et al (2005) reported 2.7 and 3.6 times, respectively.…”

“…We employed the available data from a 2-year water balance study of Tesón (2012) for the same plantations and the DOC concentrations of the present study to model the DOC annual circulation. For the periods April -March 2003-2005, we added the products of each water flux measurements per its DOC concentration. For the few sampling intervals without DOC measurements, we employed the significant regressions between DOC concentration and water flux obtained in the present study, or the DOC weighted means for fluxes when regressions were not significant.…”

Comparisons of stemflow and its bio-/abiotic influential factors between two xerophytic shrub species

“…Additionally, experimental measurements indicated that C. korshinskii had a larger MTA, LAB, LNB and LAI (an average of 54.4 • , 2509.1 cm 2 , 12 479 and 2.4, respectively) and a smaller ILAB (an average of 21.9 mm 2 ) than did S. psammophila (an average of 48.5 • , 1797.9 cm 2 , 2404, 1.7 and 87.5 mm 2 , respectively). The concave leaf shape, upward leaf orientation (MTA) and densely veined leaf structure (ILAB) (Xu et al, 2005) provided stronger leaf structural support in C. korshinskii for the interception and transportation of precipitation, particularly during highly intense rains. Therefore, in addition to the leaf morphology, C. korshinskii was also equipped with more beneficial leaf structural features for stemflow yield.…”

“…However, as to biotic mechanisms, although the canopy structure (Mauchamp and Janeau, 1993;Crockford and Richardson, 2000;Pypker et al, 2011) and branch architecture (Herwitz, 1987;Murakami, 2009;Carlyle-Moses and Schooling, 2015) have been studied for years, the most important plant traits vary with location and shrub species and have not yet been determined. The effects of the leaves have been studied more recently at a smaller scale, e.g., leaf orientation (Crockford and Richardson, 2000), shape (Xu et al, 2005), arrangement pattern (Owens et al, 2006), pubescence (Garcia-Estringana et al, 2010), area (Sellin et al, 2012), epidermis microrelief (RothNebelsick et al, 2012), amount , or biomass (Yuan et al, 2016). Comparisons of stemflow yield during summer (the growing or foliated season) and winter (the dormant or defoliated season) generally indicate negative effects of leaves because more stemflow occurs during the leafless period (Dolman, 1987;Masukata et al, 1990;Neal et al, 1993;Mużyło et al, 2012).…”

“…The factors, such as a relatively large LNB (Levia et al, 2015;Li et al, 2016), a large LAB , a high LAI (Liang et al, 2009), a big BML (Yuan et al, 2016), a scale-like leaf arrangement (Owens et al, 2006), a small ILAB (Sellin et al, 2012), a concave leaf shape (Xu et al, 2005), a densely veined leaf structure (Xu et al, 2005), an upward leaf orientation (Crockford and Richardson, 2000), leaf pubescence (Garcia-Estringana et al, 2010) and the leaf epidermis microrelief (e.g., the non-hydrophobic leaf surface and the grooves within it) (Roth-Nebelsick et al, 2012), together resulted in retaining a large amount of precipitation in the canopy, supplying water for stemflow yield and providing a beneficial morphology that enables the leaves to function as a highly efficient natural water collecting and channeling system. According to the documentation at Flora of China (Chao and Gong, 1999;Liu et al, 2010) and the field observations in this study, C. korshinskii had more beneficial leaf morphology for stemflow yield than did S. psammophila, owing to a lanceolate and concave leaf shape, a pinnate compound leaf arrangement and a densely sericeous pressed pubescence (Fig.…”