Physical properties of water in relation to stemflow leachate dynamics: implications for nutrient cycling

Abstract

Stemflow leachate chemistry from a deciduous canopy tree species monitored during late winter and early spring precipitation events demonstrated significant chemical enrichment. By considering stemflow volume and chemical concentration in relation to the quantity that would be expected in a rain gage occupying an area equivalent to the trunk basal area, manganese was found to be enriched by a mean factor of 1450 and potassium by a mean factor of 580. The most pronounced enrichment was documented during a late winter rain-on-snow event characterized by temperature oscillations near the freezing point. During this event, manganese was enriched by a factor of 4400 and potassium by 1715. We conclude that mixed precipitation events with multiple freeze-melt cycles can generate significantly more leachate than spring rainfall events because of lower air temperatures and increased kinematic viscosity and surface tension of stemflow drainage. These physical properties lengthen the residence time of intercepted precipitation on the woody frame of the tree and promote its funneling from inclined branches. Stemflow represents a spatially localized and enriched point input that may affect tree vigor in early spring. The influence of localized aqueous chemical fluxes to the forest floor on forest biogeochemistry and ecophysiological functioning are discussed.Résumé : La chimie du lessivat du ruissellement sur le tronc d'espèces arborescentes décidues suivie durant les évène-ments pluvieux de la fin de l'hiver et du début du printemps a révélé un enrichissement chimique significatif. En considérant le volume du ruissellement sur le tronc et la concentration chimique en relation avec la quantité à laquelle on s'attendrait dans une jauge à pluie occupant une surface équivalente à la surface terrière du tronc, le manganèse était enrichi en moyenne d'un facteur de 1450 et le potassium, d'un facteur de 580. L'enrichissement le plus prononcé a été observé durant un évènement de pluie et de neige à la fin de l'hiver caractérisé par une température oscillant autour du point de congélation. Durant cet évènement, le manganèse a été enrichi d'un facteur de 4400 et le potassium, d'un facteur de 1715. Nous en concluons que les évènements de précipitation mixte avec des cycles multiples de geldégel peuvent générer significativement plus de lessivat que les évènements pluvieux du printemps en raison des températures plus basses de l'air et d'un accroissement de la viscosité cinématique et de la tension de surface du drainage de l'écoulement sur le tronc. Ces propriétés physiques allongent le temps de résidence de la précipitation interceptée sur la structure ligneuse de l'arbre et favorisent sa canalisation à partir des branches inclinées. Le ruissellement sur le tronc représente un apport localisé particulier, et enrichi, qui peut affecter la vigueur de l'arbre tôt au printemps. L'influence de flux chimiques aqueux vers la couverture morte sur la biogéochimie de la forêt et le fonctionnement écophysiologique sont discutés.[Traduit par la Ré...

Disproportionate single-species contribution to canopy-soil nutrient flux in an Amazonian rainforest

“…The comparability to our data, however, is limited because Levia et al (2011b) used the median as a measure of central tendency, and because both studies (Levia and Herwitz, 2000;Levia et al, 2011b) worked on an event basis and not with flux totals per sampling period as in this study. Nevertheless, the results of these studies indicate that enrichment ratios of individual events vary widely; for instance, K þ shows, depending on meteorological conditions, event-based enrichment ratios as high as 1700 (Levia and Herwitz, 2000). In view of the particularly large solute fluxes from mature babassu palms and considering that these palms occupy only 0.03% of the study area, the forest floor around babassu stems is likely a microsite with soil properties distinct from the bulk soil.…”

“…Stemflow enrichment ratio per trunk basal area E was calculated according to Levia and Herwitz (2000) as…”

“…Data of two other studies, which are based on measurements on a single pignut hickory (Carya glabra Mill.) tree (Levia and Herwitz, 2000), a small group of two American beech (Fagus grandifolia Ehrh. ), and three yellow poplar (Liriodendron tulipifera L.) trees (Levia et al, 2011b) indicate that the enrichment ratios at our study site indeed define the higher end of range: Levia and Herwitz (2000) reported mean K þ enrichment ratios of 580, whereas Levia et al (2011b) found median enrichment ratios that were much lower for most solutes (K þ :88 and 17, NO À 3 :23 and >1, respectively).…”

“…tree (Levia and Herwitz, 2000), a small group of two American beech (Fagus grandifolia Ehrh. ), and three yellow poplar (Liriodendron tulipifera L.) trees (Levia et al, 2011b) indicate that the enrichment ratios at our study site indeed define the higher end of range: Levia and Herwitz (2000) reported mean K þ enrichment ratios of 580, whereas Levia et al (2011b) found median enrichment ratios that were much lower for most solutes (K þ :88 and 17, NO À 3 :23 and >1, respectively). The comparability to our data, however, is limited because Levia et al (2011b) used the median as a measure of central tendency, and because both studies (Levia and Herwitz, 2000;Levia et al, 2011b) worked on an event basis and not with flux totals per sampling period as in this study.…”

Manganese as a site factor for epiphytic lichens

“…Mn concentration in conifer bark primarily depends on Mn concentrations in the soil (HAUCK et al 2002a), as Mn is readily taken up by the tree roots and transfered to the bark through the xylem and xylem parenchyma (LÖVESTAM et al 1990, SLOOF & WOLTERBEEK 1993. Mn concentrations in stemflow are primarily controlled by leaching rates from bark and foliage (LEVIA & HERWITZ 2000), whereas interception of Mn from the atmosphere is of subordinate significance (HAUCK 2003). Thus Mn is primarily a natural site factor for epiphytic lichens, the significance of which may be increased due to anthropogenic soil acidification, as Mn availability increases with decreasing pH (NORVELL 1988).…”