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[en] It has been suggested that the leaf litter layer influences soil infiltration processes in hillslopes. This paper examines the effect of the presence of the leaf litter layer in an oak woodland on conservative tracer transport measured in situ using time domain reflectometry (TDR) probes. This was done using repeated tracer miscible displacement studies, first with the litter layer intact and then again after removal of the litter layer. Tracer transport, as measured breakthrough curves (BTCs), was characterized using temporal moment analyses. These plot scale studies, performed at a field location in northern California, did not identify consistent changes in tracer transport patterns in the vertical transport plots before and after litter layer removal. In contrast, downslope lateral tracer displacement in the upper 20 cm of the soil did change after litter removal. However, no differences were evident deeper in the soil (30-50 cm) in temporal moments before and after litter removal during lateral tracer transport. This result demonstrates that the litter layer had a localized (near soil surface) influence on lateral transport. This influence may be explained by vertical anisotropy in effective soil hydraulic conductivity on the direction of lateral flow relative to the soil surface in the hillslope plots. It was demonstrated that the litter presence promotes a more vertical direction for the lateral flow in the first 20 cm of the soil. Despite the small changes in the first 20 cm observed in tracer transport after litter removal, the physical presence of the leaf litter layer was not found to be a major influence on tracer transport at the 30- to 50-cm depth in this hillslope soil where most of the lateral flow occurs
[en] The decomposition of a forest litter in forest ecosystems contaminated by radionuclides is accompanied by the accumulation of organomineral compounds associated with 137Cs in deeper soil layers. The highest level of 13Cs in the upper organic-reach soil layers was found in the insoluble fraction of organic matter, hemicellulose and cellulose. Due to a high level of the 137Cs accumulation in a forest litter, the last generates a substantial part of the 137Cs background in forests
[en] Mangroves in Peninsular Malaysia are typical of tropical forest setting. Nevertheless, the state of the mangrove forests has led to various classifications; natural and degraded mangroves. The study aimed to utilize litter fall (production and standing crop) potential as a means of evaluating the degree of productivity of the mangrove types across seasons, in addition to determining the abundance of carbon and nitrogen in the Peninsular mangrove forest. Leaf litter accounted for more than 70% of the total litter production in both natural and degraded mangroves, and the peak month for such production was December; 82.7% and 82.2%, for Sungai Haji Dorani and Kuala Selangor Nature Park, respectively. The degraded mangrove recorded higher concentration of total N (6.16 mg/g) than the natural mangrove forest (5.60 mg/g) at significant level. However, the organic carbon (CO) content across the litter parts varied with the three seasons. The CO of leaf litter was at the peak during the dry season, however, analysis on the branch and fruit revealed that during the intermediate and wet seasons CO level could be higher than the concentration observed at dry season. Though, the study concluded that both mangrove types in Peninsular Malaysia showed high similarity in the degree of litter production, yet the identified differences suggest that counter measures need to be adopted in order to protect mangroves from degradation and possible productivity loss. (author)
[en] The effects of elevated carbon dioxide on the chemistry and subsequent response of stream microorganisms growing on leaf litter of three riparian tree species (quaking aspen, white willow and sugar maple) were studied. Results showed that the effects were species-specific, i.e. aspen leaves contained high concentrations of lignin, maple leafs contained higher concentrations of soluble phenolic compounds and willow leaves contained higher concentrations of carbohydrate-bound condensed tannins. Initially, the higher concentrations of soluble phenolic compounds in maple leaves were rapidly leached in stream water, but overall, the impact of altered leaf chemistry on riparian trees grown under elevated carbon dioxide was clearly variable; no strongly suppressed microbial activity during stream incubation was observed. Any evidence of suppression observed, was species-specific. 49 refs., 2 tabs., 3 figs
[en] Variation of tritium concentration was examined for 100 days in the course of degradation of fresh pine needles, which were left on a pine forest floor. No difference was observed on free water tritium (FWT) and organically bound tritium (OBT) concentrations of sterilized samples by gamma-ray irradiation or fumigation and control samples, attributable to incomplete sterilization. The OBT concentrations did not increase within the experimental period as the level of humus collected from the forest floor. The results suggest that a longer degradation time, more than 100 days, is necessary to elevate OBT up to the level, which is observed in the general environment. (author)
[en] We evaluated the carbon budget of coarse woody debris (CWD) in a temperate broad-leafed secondary forest. On the basis of a field survey conducted in 2003, the mass of CWD was estimated at 9.30 tC/ha, with snags amounting to 60% of the total mass. Mean annual CWD input mass was estimated to be 0.61 tC/ha/yr by monitoring tree mortality in the forest from 1999 to 2004. We evaluated the CWD decomposition rate as the CO2 evolution rate from CWD by measuring CO2 emissions from 91 CWD samples (RCWD) with a closed dynamic chamber and infrared gas analysis system. The relationships between RCWD and temperature in the chamber, water content of the CWD, and other CWD characteristics were determined. By scaling the measured RCWD to the ecosystem, we estimated that the annual RCWD in the forest in 2003 was 0.50 tC/ha/yr or 10%-16% of the total heterotrophic respiration. Therefore, 0.11 tC/ha/yr or 7% of the forest net ecosystem production was sequestered by CWD. In a young forest, in which CWD input and decomposition are not balanced, the CWD carbon budget needs to be quantified for accurate evaluation of the forest carbon cycle and NEP
[en] Here we investigate the response of soils and litter to 5 years of experimental additions of ammonium (NH4), nitrate (NO3), and ammonia (NH3) to an ombrotrophic peatland. We test the importance of direct (via soil) and indirect (via litter) effects on phosphatase activity and efflux of CO2. We also determined how species representing different functional types responded to the nitrogen treatments. Our results demonstrate that additions of NO3, NH4 and NH3 all stimulated phosphatase activity but the effects were dependent on species of litter and mechanism (direct or indirect). Deposition of NH3 had no effect on efflux of CO2 from Calluna vulgaris litter, despite it showing signs of stress in the field, whereas both NO3 and NH4 reduced CO2 fluxes. Our results show that the collective impacts on peatlands of the three principal forms of nitrogen in atmospheric deposition are a result of differential effects and mechanisms on individual components. - We found that nitrogen deposition affects microbial activity associated with litter through both indirect and direct mechanisms, but these effects were dependent on the chemical form of inorganic nitrogen compounds.
[en] Chemical changes in leaf input to forest soils have been reported to affect decay processes. In this work, litter mass loss and decomposition constants (k) during 200 days in solid-state fermentation of the native tree Celtis tala Gill. ex Planch. and the exotic one Ligustrum lucidum Ait. with three common litter saprotrophic basidiomycetes were compared. Alterations in litter quality were characterized by solid-state 13C NMR spectroscopy, pH, soluble sugars, ammonium, proteins, and phenol content determination and were associated with extracellular lignocellulolytic enzyme production. Differences in substrate decomposition related to litter type were observed for Leratiomyces ceres, achieving a higher k in the exotic L. lucidum litter, which might be attributed to the induction of manganese peroxidase activity. Substrate preference for alkyl C and more degradation of lignified compounds were found in such substrates. Although no statistical differences in mass loss were observed for the rest of the fungi assayed, we detected changes in several of the parameters evaluated. This suggests that exotic invasions may alter ecosystem functioning by accelerating decomposition processes through an increased fungal ligninolytic activity. (author)
[en] A signature of globalization is the prevalence of exotic trees along reforested urban and rural riparian zones in the neotropics, but little is known about the instream processing of its leaf litter. In this study, leaf litter breakdown rates were measured during 35 days using mesh bags within a reference headwater stream for seven exotic and three native tree species commonly used in urban and rural reforestation. Artocarpus altilis, Schefflera actinophylla and Terminalia catappa scored the highest mass loss rates (>85 %; mean life: t50 <15 d), while Cecropia sp. and Cespedesia macrophylla (mass loss =36 and 15 %; t50 =58 and 172 d, respectively) scored the lowest rates. However, a broad range of rates was observed among the ten species studied. The carbon to phosphorus ratio (c:p) and toughness of the leaf litter were the best predictors of breakdown rates. However, these leaf properties were not correlated with the very low values of macro invertebrates abundance and diversity, and the few morpho classified as shredders. Therefore physical rather than biological controls seem to best explain the observed variability of mass loss rates, and thus slow decomposing leaf litter species seems to provide a habitat rather than a food resource, particularly to collectors. This study suggests that riparian reforestation will propagate species-specific ecological influences on instream processes such as leaf litter processing depending on leaf quality properties, therefore ecosystem-wide influences should be considered for improving reforestation strategies. Future studies should test for differences in breakdown rates and colonization by macro invertebrates relative for leaf litter species origin (native vs. exotic).
[en] Litterfall was monitored for 1 year on Walker Branch Watershed (97.5 ha) in eastern Tennessee. Data were collected from 80 plots, each with a 1 m2 litter trap, and were stratified in two alternate ways for analysis. In one case, a conventional cover-type map was used to separate the plots into one of four cover types. In the other case, plots were separated into four groups based on multivariate stratification of overstory basal-area data. Subtle differences among strata in seasonal dynamics, total annual quantity, and elemental concentration of litterfall were detected better under the multivariate stratification than under the cover-type stratification. This study demonstrates that analysis of the structure of an ecosystem using multivariate techniques provides a firm basis for subsequent analysis of functions within that system