Litterfall Fluxes Research Articles

Total atmospheric mercury deposition in forested areas in South Korea

Abstract. In this study, mercury (Hg) was sampled weekly in dry and wet deposition and throughfall and monthly in litterfall, and as it was volatilized from soil from August 2008 to February 2010 to identify the factors influencing the amount of atmospheric Hg deposited to forested areas in a temperate deciduous forest in South Korea. For this location there was no significant correlation between the estimated monthly dry deposition flux (litterfall + throughfall – wet deposition) (6.7 µg m−2 yr−1) and directly measured dry deposition (9.9 µg m−2 yr−1) likely due primarily to Hg losses from the litterfall collector. Dry deposition fluxes in cold seasons (fall and winter) were lower than in warmer seasons (spring and summer). The volume-weighted mean (VWM) Hg concentrations in both precipitation and throughfall were highest in winter, likely due to increased scavenging by snow events. Since South Korea experiences abundant rainfall in summer, VWM Hg concentrations in summer were lower than in other seasons. Litterfall fluxes were highest in the late fall to early winter, when leaves were dropped from the trees (September to November). The cumulative annual Hg emission flux from soil was 6.8 µg m−2 yr−1. Based on these data, the yearly deposition fluxes of Hg calculated using two input approaches (wet deposition + dry deposition or throughfall + litterfall) were 6.8 and 3.6 µg m−2 yr−1, respectively. This is the first reported study which measured the amount of atmospheric Hg deposited to forested areas in South Korea, and thus our results provide useful information to compare against data related to Hg fate and transport in this part of the world.

Mercury in coniferous and deciduous upland forests in northern New England, USA: implications of climate change

Abstract. Climatic changes in the northeastern US are expected to cause coniferous stands to transition to deciduous stands over the next hundred years. Mercury (Hg) sequestration in forest soils may change as a result. In order to understand potential effects of such a transition, we studied aboveground vegetation and soils at paired coniferous and deciduous stands on eight mountains in Vermont and New Hampshire, USA. Organic horizons at coniferous stands accumulated more total Hg (THg; 42 ± 6 g ha−1) than deciduous stands (30 ± 4 g ha−1). Total Hg pools in the mineral horizons were similar for coniferous (46 ± 8 g ha−1) and deciduous stands (45 ± 7 g ha−1). Soil properties (C, % clay, and pH) explained 56 % of the variation in mineral soil Hg concentration when multiply regressed. Foliar and bole wood Hg concentrations were generally greater for coniferous species than deciduous species. Using allometric equations, we estimated that aboveground accumulation of Hg in foliage and woody biomass was similar between vegetation types but that coniferous stands have significantly smaller annual litterfall fluxes (0.03 g ha−1 yr−1) than deciduous stands (0.24 g ha−1 yr−1). We conclude that organic horizon Hg accumulation is influenced by vegetation type but mineral horizon Hg accumulation is primarily controlled by soil properties. Further investigations into the effect of vegetation type on volatilization, atmospheric deposition, and leaching rates are needed to constrain regional Hg cycling rates.

Seasonal Mercury Dynamics in a New England Vernal Pool

Mercury fluxes into and transformations within a small vernal pool in Massachusetts were investigated over a wet-dry-wet cycle. We measured the deposition of total mercury (HgT) and methyl mercury (MeHg) via litterfall between October 6 and December 2, 2010. Litterfall fluxes were 10 μg m−2 and 80 ng m−2, respectively, over that time period. Average HgT concentration in litterfall was 33 ± 2 ng gdw−1; 0.9 % was present as MeHg. The HgT content of the litter layer increased slightly throughout the year, reaching 55 ± 20 ng gdw−1 inside and 42 ± 7 ng gdw−1 outside the pool. Litter %MeHg increased only to 1.5 % on the forest floor, while it increased dramatically in the vernal pool after inundation in late November, reaching 9 % by early spring. Measurements in pool benthic invertebrates show that two types of shredders bioaccumulated MeHg 4–9-fold relative to the leaf litter substrate. Overall, our results indicate significant production and bioaccumulation of MeHg in this vernal pool. This de novo MeHg could impact resident amphibians or be exported to the surrounding forest.

Carbon and nutrients of Scots pine stands on sandy soils in Lithuania in relation to bioenergy sustainability

Sustainable forestry is based on the principle that harvesting practices should avoid negative influence on soil fertility, wood production and long-term soil carbon (C) stocks. We examined C and nutrient concentrations and stocks of Scots pine (Pinus sylvestris L.) stands on Arenosols in south-western Lithuania. The stands were 10, 20, 40, 50 and 65 years of age. C concentrations were relatively constant, while the concentrations of N, P, K, Ca, Mg and S often varied between compartments and stand ages.The total aboveground stocks of nitrogen (N) were estimated to be in the range of 185–260 kg ha−1, and 78–189 kg ha−1 for calcium (Ca), 75–104 kg ha−1 for potassium (K), 22–33 kg ha−1 for phosphorus (P), 21–41 kg ha−1 for magnesium (Mg) and 16–28 kg ha−1 for sulphur (S). Corresponding stocks of the crown alone were 139–207 kg ha−1 of N, 54–88 kg ha−1 of Ca, 44–79 kg ha−1 of K, 15–26 kg ha−1 of P, 15–23 kg ha−1 of Mg, and 11–15 kg ha−1 of S. Biomass, C and nutrient stocks in the crown did not change with age, whereas the stemwood stocks increased with stand age. The total removals of C and N over a whole 100-year rotation were simulated to be 129 Mg ha−1 and 449 kg ha−1, respectively. An example scenario was created to compare the magnitude of potential nutrient removals with the atmospheric influx, soil stocks, and the internal litterfall flux. We suggest that intensified utilisation of these stands for bioenergy may be sustainable.

Litterfall mercury deposition in Atlantic forest ecosystem from SE – Brazil

Litterfall is believed to be the major flux of Hg to soils in forested landscapes, yet much less is known about this input on tropical environment. The Hg litterfall flux was measured during one year in Atlantic Forest fragment, located within Rio de Janeiro urban perimeter, in the Southeastern region of Brazil. The results indicated a mean annual Hg concentration of 238 ± 52 ng g−1 and a total annual Hg deposition of 184 ± 8.2 μg m−2 y−1. The negative correlation observed between rain precipitation and Hg concentrations is probably related to the higher photosynthetic activity observed during summer. The total Hg concentration in leaves from the most abundant species varied from 60 to 215 ng g−1. Hg concentration showed a positive correlation with stomatal and trichomes densities. These characteristics support the hypothesis that Tropical Forest is an efficient mercury sink and litter plays a key role in Hg dynamics.

Response of the N and P cycles of an old-growth montane forest in Ecuador to experimental low-level N and P amendments

Atmospheric nitrogen (N) and phosphorus (P) depositions are expected to increase in the tropics as a consequence of increasing human activities in the next decades. In the literature, it is frequently assumed that tropical montane forests are N-limited, while tropical lowland forests are P-limited. In a low-level N and P addition experiment, we determined the short-term response of N and P cycles in a north Andean montane forest on Palaeozoic shists and metasandstones at an elevation of 2100m a.s.l. to increased N and P inputs. We evaluated experimental N, P and N+P additions (50kgha−1yr−1 of N, 10kgha−1yr−1 of P and 50kg+10kgha−1yr−1 of N and P, respectively) and an untreated control in a fourfold replicated randomized block design. We collected litter leachate, mineral soil solution (0.15 and 0.30m depths), throughfall and litterfall before the treatment began (August 2007) until 16 months after the first nutrient application (April 2009). Less than 10 and 1% of the applied N and P, respectively, leached below the organic layer which contained almost all roots and no significant leaching losses of N and P occurred to below 0.15m mineral soil depth. Deposited N and P from the atmosphere in dry and wet form were retained in the canopy of the control treatment using a canopy budget model. Nitrogen and P retention by the canopy were reduced and N and P fluxes in throughfall and litterfall increased in their respective treatments. The increase in N and P fluxes in throughfall after fertilization was equivalent to 2.5% of the applied N and 2% of the applied P. The fluxes of N and P in litterfall were up to 15% and 3%, respectively, higher in the N and N+P than in the control treatments. We conclude that the expected elevated N and P deposition in the tropics will be retained in the ecosystem, at least in the short term and hence, N and P concentrations in stream water will not increase. Our results suggest that in the studied tropical montane forest ecosystem on Palaeozoic bedrock, N and P are co-limiting the growth of organisms in the canopy and organic layer.

Carbon resources, soil organisms, and nitrogen availability: Landscape patterns in a northern hardwood forest

The interactions among different components of detrital food webs are likely to influence carbon processing and linkages between C and nutrient cycling. Our objective was to identify potentially important interactions in detrital food webs at the Hubbard Brook Experimental Forest, NH, USA, by exploring relationships among C resources, microbial biomass, microarthropod abundance and nitrogen availability as they vary across the landscape. We found significant spatial variation in microarthropod abundance in the forest floor across elevation zones in two watersheds, with consistently higher abundance in low-elevation hardwoods and upper conifer zones and lower abundance in mid- and high-elevation hardwoods. The same pattern was observed in the Oe horizon for microbial biomass C and respiration but not for N transformations; however, no patterns were observed in the Oa horizon. Microarthropod abundance and microbial biomass C were significantly positively correlated, but neither were related to forest floor mass or to annual aboveground fine litterfall flux. Instead, a positive correlation with fine root biomass suggests that C supply from roots plays a key role in the fungal channel of the detrital food web of these forests. The lack of relationship between patterns of microarthropod abundance and net N mineralization leads us to hypothesize that spatial patterns of nitrogen availability are not closely linked to variation in carbon flow through the detrital food web, within this forested landscape. In contrast, microarthropod abundance and net N mineralization did exhibit similar interannual variation and may respond to the same temporal controls.

Nutrient transfer by leaf litterfall during a sugar maple decline episode at Lake Clair watershed, Québec, Canada

In a declining sugar maple (SM) stand, we tested the hypothesis that an increasing relative abundance of American beech (AB) and yellow birch (YB) would improve litter quality by providing a higher proportion of litterfall richer in base cations and lower in acidity. From 1989 to 2006, SM leaf fall diminished from 59% (1,718 kg ha−1 year−1) to 36% (915 kg ha−1 year−1) of the total leaf fall biomass. Overall, the increase in AB and YB litterfall compensated for the SM decrease, resulting in constant annual leaf litterfall fluxes (2,803 kg ha−1 year−1) over the period studied. However, because the leaf litter for AB and YB had Ca and Mg concentrations 2–3 times higher than did SM, Ca and Mg concentrations and fluxes in leaf litterfall significantly increased between 1989 and 2006. Leaf litterfall of AB and YB also has a higher base/acid ratio than SM. Consequently, changes in forest composition following SM decline led to a clear improvement in litterfall quality in terms of base cations content and fluxes and acid–base properties.

Litterfall and nutrient return in five tree species in a common garden experiment

Canopy litterfall is a significant pathway for return of nutrients and carbon (C) to the soil in forest ecosystems. Litterfall was studied in five even-aged stands of Norway spruce, Sitka spruce, Douglas-fir, European beech and common oak at three different locations in Denmark; two sandy sites, Ulborg and Lindet in Jutland, and one loamy site, Frederiksborg on Zealand. Litterfall was collected during three years from 1994 to 1996 in all five species and during six years from 1994 to 1999 in Norway spruce, Sitka spruce and European beech. The average total litterfall was in the range of 3200–3700 kg ha −1 yr −1 and did not differ significantly among tree species. There were no significant differences in total litterfall among sites during the short period, but during the longer period the richer site Frederiksborg had significantly higher total and foliar litterfall amounts compared to the more nutrient-poor sites Lindet and Ulborg. There were close relationships between foliar and total litterfall suggesting that foliar litterfall can be reliably estimated from total litterfall. Beech and oak bud scale litter was significantly related to foliar litterfall. The amount of branch and twig litter was significantly higher in oak than in other tree species. The average foliar litterfall was well related to the annual volume increment. The relationship differed markedly from previously reported relationships based on global litterfall data suggesting that such relationships are better evaluated at the regional level. Nutrient concentrations and fluxes in foliar litterfall were not significantly different among the five tree species. However, there was a significant effect of site on most nutrient concentrations of the three litterfall fractions, and foliar fluxes of P, Ca and Mn were all significantly highest at Frederiksborg and lowest at Ulborg. The similarity in litterfall inputs to the forest floor under these five tree species suggested that previous reports of large variability in forest floor accumulation should primarily be attributed to differences in litter decomposition.

Mercury budget of a small forested boreal catchment in southeast Norway

We present input and output fluxes of total mercury (Hg tot) and methyl mercury (MeHg) based on throughfall, litterfall and stream water samples from 2004/2005 from a small forested catchment (Langtjern) in Norway. Hg tot input via throughfall and litterfall was estimated to 6.7 and 2.7 µg m − 2 yr − 1 , respectively, which is considerably lower than previously reported from other boreal catchments in Scandinavia. A likely cause for the low input flux is the sparseness and low productivity of the forest in the Langtjern catchment, with less atmospheric scavenging and lower litterfall fluxes than previously studied sites. In addition there has been a general decrease in mercury (Hg) in the atmosphere on the northern hemisphere in the last decade. The estimated output flux of Hg tot with surface water was 2.5 µg m − 2 yr − 1 , which is comparable to what has been reported elsewhere. The ratio of Hg tot output flux to input flux was 26%, which is considerably higher than reported from other sites. This illustrates that catchment properties have greater importance for surface water export of Hg than the current atmospheric input. The estimated total soil pool of Hg tot in the catchment was 17.4 mg m − 2 . This corresponds to roughly 8000 years of the current surface water output flux and 2000 years of the current input flux.

Biogeochemistry of Organic and Inorganic Arsenic Species in a Forested Catchment in Germany

Little is known about the fate and behavior of diffuse inputs of arsenic (As) species in forested catchments which often are the sources of drinking water. The objective of this study was to investigate the mobility and transformation of different As species in forest ecosystems to assess the environmental risk related to the diffuse pollution of As. We determined concentrations and fluxes in precipitation, litterfall, soil solutions (Oa horizon and 20- and 90-cm depth), and runoff of organic and inorganic As species and Astotal in a forest ecosystem in NE-Bavaria, Germany. The concentrations of Astotal were mostly <1 microg As L(-1) in aqueous samples and were highest in forestfloor percolates (7.6 microg As L(-1)). In litterfall, the concentrations of As species never exceeded 0.1 microg As g(-1). Arsenate and arsenite were the prevalent As species in all samples. Organic As species, comprising monomethylarsonic acid, dimethylarsinic acid, trimethylarsine oxide, arsenobetaine, and three unidentified organic As species, were mostly found in throughfall reaching up to 45% of Astotal. The total deposition of Astotal (calculated as throughfall + litterfall) was 5.6 g As ha(-1) yr(-1) with 16% contribution of litterfall. The annual Astotal fluxes were 30 g As ha(-1) yr(-1) for forest floor percolates, 8.0 g As ha(-1) yr(-1) at 20-cm soil depth, and 1.4 g As ha(-1) yr(-1) at 90-cm soil depth. The annual runoff of Astotal from the catchment amounted to 3.8 g As ha(-1) yr(-1). The annual fluxes of total organic As species was highest in total deposition (1.1 g As ha(-1) yr(-1)) and decreased largely with depth in the soil profile. The annual runoff of total organic As species was only 0.08 g As ha(-1) yr(-1). Significant correlations in soil solutions and runoff were found between Astotal and dissolved organic C and Fe. Correlations between Astotal concentrations in runoff and water fluxes were seasonally dependent and with a steeper slope in the growing season than in the dormant season. The elevated concentrations of organic As species in throughfall indicate microbial methylation of As in the phyllosphere, but no evidence for methylation in the soil was found. The mass balance of the catchment points out the strong retention and probable degradation or oxidation of organic As species and arsenite but also to mobilizable pools of Astotal and arsenate. The forest floor is presently a source, whereas the mineral soil is a sink for Astotal and arsenate. The As concentrations in runoff seem to be controlled by As mobilization from forest floor and riparian wetland soils during heavy rain events and superficial flow. The risk for excessment of the drinking water threshold concentrations of As in runoff and soil solutions is considered low at our site.

Lignin and enhanced litter turnover in tree plantations of lowland Costa Rica

We quantified the effect of overstory species composition on forest floor dynamics in lowland Costa Rica. Aboveground litter production and forest floor mass were measured over 1 year in 16-year-old single-species plantations established in a randomized complete block design with four blocks. The tree species investigated (=experimental treatments) were Hyeronima alchorneoides, Pentaclethra macroloba, Pinus patula subsp. tecunumanii, Virola koschnyi, Vochysia ferruginea, and Vochysia guatemalensis. Organic matter fluxes in litterfall, which averaged 10.1 Mg ha −1 year −1, were similar to those reported from comparable Neotropical plantations, whereas nitrogen fluxes in litterfall (up to 210 kgN ha −1 year −1) were high. Litter production was significantly greater beneath Hyeronima and V. ferruginea than beneath Virola, primarily due to high rates of non-woody litter production by Hyeronima, large amounts of twig litter production by V. ferruginea, and low production of both fractions by Virola. V. ferruginea had significantly more branch litter on the ground than did any other species, whereas Hyeronima had the largest accumulations of non-woody (mostly leaf) litter. Accumulations of woody litter correlated closely with rates of branchfall: branches ≤1 cm in diameter persisted on the forest floor for 0.9 year on average, independent of species. Rates of decay of non-woody litter, in contrast, varied significantly among species, with fastest rates (2.8 year −1) observed beneath Pentaclethra and the slowest decay rates (1.5 year −1) in plots of V. guatemalensis. Contrary to expectations, litter decay rates increased with increasing lignin contents, paralleling results of a concomitant study that found a significant negative correlation between litter lignin and surface-soil organic matter content. Our results demonstrate that different overstory-tree species generate significantly different forest floors, in terms of mass, composition and dynamics. These differences affect soil restoration, tree regeneration and other ecological processes important to selecting species for tropical plantation establishment and reforestation efforts.

Spatial associations of humus, nutrients and soils in mixed dipterocarp forest at Lambir, Sarawak, Malaysian Borneo

Discrete humus layers are common on podzols under temperate coniferous and tropical heath forests, and patchy layers also occur under some temperate broadleaved forests on non-podzolic soils. We used multiple data sets to test the reported association of humus with oligotrophic but non-podzolic soils under non-heath dipterocarp forest at Lambir, Sarawak. We examined the distribution, morphology and nutrient dynamics of necromass on soils derived from sandstone and shale. Concentrations of the main mineral nutrients were lower in fresh litter on the very oligotrophic sandstone soils than on shale. The rates of litterfall were similar, so that annual litterfall fluxes of all nutrients were lower on sandstone. The lower nutrient concentrations and fluxes in the litter on sandstone resulted in slower decomposition, longer residence times and larger standing crops of forest-floor necromass, with lower concentrations of nutrients. The necromass on sandstone sequestered significantly more N, K and Mg but less Ca and Mn than on shale, with no significant difference for P. The variations in necromass nutrient dynamics were associated with morphological differences. There were mats of densely rooted humus under the litter on sandstone, whereas litter lay directly over the mineral topsoil on shale. Spatial associations with soil nutrients were weak for necromass thickness, but clear for humus. The proportions of nutrients in the litterfall and necromass reflected the stoichiometric profiles of the soils. We attribute the differences in necromass nutrient dynamics and their association with soil reserve nutrients to lower rates of nutrient replenishment from the weathering of sandstone than from shale. Necromass characteristics are robust field indicators of multivariate edaphic differences in these and other tropical forests on Acrisols/Ultisols derived from Tertiary clastic sediments.

Investigation of Mercury Exchange between Forest Canopy Vegetation and the Atmosphere Using a New Dynamic Chamber

This paper presents the design of a dynamic chamber system that allows full transmission of PAR and UV radiation and permits enclosed intact foliage to maintain normal physiological function while Hg(0) flux rates are quantified in the field. Black spruce and jack pine foliage both emitted and absorbed Hg(0), exhibiting compensation points near atmospheric Hg(0) concentrations of approximately 2-3 ng m(-3). Using enriched stable Hg isotope spikes, patterns of spike Hg(ll) retention on foliage were investigated. Hg(0) evasion rates from foliage were simultaneously measured using the chamber to determine if the decline of foliar spike Hg(II) concentrations over time could be explained by the photoreduction and re-emission of spike Hg to the atmosphere. This mass balance approach suggested that spike Hg(0) fluxes alone could not account for the measured decrease in spike Hg(II) on foliage following application, implying that eitherthe chamber underestimates the true photoreduction of Hg(ll) to Hg(0) on foliage, or other mechanisms of Hg(II) loss from foliage, such as cuticle weathering, are in effect. The radiation spectrum responsible for the photoreduction of newly deposited Hg(II) on foliage was also investigated. Our spike experiments suggest that some of the Hg(ll) in wet deposition retained by the forest canopy may be rapidly photoreduced to Hg(0) and re-emitted back to the atmosphere, while another portion may be retained by foliage at the end of the growing season, with some being deposited in litterfall. This finding has implications for the estimation of Hg dry deposition based on throughfall and litterfall fluxes.

Litterfall Mercury in Two Forested Watersheds at Acadia National Park, Maine, USA

Litterfall can be an important flux of mercury (Hg) to soils in forested landscapes, yet typically the only available data to evaluate Hg deposition is from precipitation Hg monitoring. Litterfall was collected at 39 sampling sites in two small research watersheds, in 2003 and 2004, and analyzed for total Hg. Four vegetation classes were designated in this study as hardwoods, softwoods, mixed and scrub. The mean litter Hg concentration in softwoods (58.8 ± 3.3 ng Hg g−1 was significantly greater than in mixed (41.7 ± 2.8 ng Hg g−1 and scrub (40.6 ± 2.7 ng Hg g−1, and significantly lower than in hardwoods (31.6 ± 2.6 ng Hg g−1. In contrast, the mean weighted litter Hg flux was not significantly different among vegetation classes. The lack of a significant difference in litter Hg flux between hardwoods and softwoods was attributable to the large autumnal hardwood litter Hg flux being balanced by the higher softwood litter Hg concentrations, along with the higher chronic litterfall flux throughout the winter and spring in softwoods. The estimated annual deposition of Hg via litterfall in Hadlock Brook watershed (10.1 μg m−2 and Cadillac Brook watershed (10.0 μg m−2 was greater than precipitation Hg deposition and similar to or greater than the magnitude of Hg deposition via throughfall. These results demonstrate that litterfall Hg flux to forested landscapes can be at least as important as precipitation Hg inputs.

The Biogeochemistry of Carbon at Hubbard Brook

The Biogeochemistry of Carbon at Hubbard Brook

Biogeochemistry of trimethyllead and lead in a forested ecosystem in Germany

Lead compounds, especially ionic organolead compounds (OLC), are highly toxic and mobile pollutants strongly affecting many ecosystems. Soil pools and fluxes with precipitation, litterfall and runoff of trimethyllead (TML), one of the dominant ionic OLC in the environment, and Pbtotal were investigated in a forested ecosystem in NE-Bavaria, Germany. In addition, ad/desorption of TML to soils was studied in batch experiments and its degradation in soils was investigated using long term incubations. Total soil storage in the catchment was 11.56 mg Pb ha−1 for TML and 222 kg Pb ha−1 for Pbtotal. More than 90% of the soil storage of TML was found in the wetland soils of the catchment representing only 30% of the area. Most Pbtotal (>90%) was found in the upland soils. In upland soils, TML was only detectable in the forest floor. The annual total deposition from the atmosphere, estimated as throughfall + litterfall fluxes, amounted to 3.7 mg Pb ha−1 year−1 for TML and 52 g Pb ha−1 year−1 for Pbtotal. The contribution of litterfall was 1.5 and 32%, respectively. The concentrations of TML and Pbtotal in wet precipitation were: fog > throughfall > bulk precipitation. The annual fluxes with runoff from the catchment was 0.5 mg Pb ha−1 year−1 for TML and 2.8 g Pb ha−1 year−1 for Pbtotal. TML degraded rapidly in the forest floor (Oa horizon) with a half-life (t1/2) of 33.5 days. The degradation of TML in Fen (t1/2 = 421 days) and in the mineral soil (Bw-C horizon, t1/2 = 612 days) was much slower. Emission of tetramethyllead from wetland soils was not observed during the 1 year incubation. The adsorption affinity of TML to different soils was Fen > Oa > A ≥ Bw-C. The ratio of total soil storages to the present annual input were 3.6 years for TML. TML and Pbtotal are still deposited in remote areas even after the use of tetraalkyllead as additives has been terminated for years. The rates of deposition are, however, much lower than in the past. Forest soils act as a sink for deposited TML and Pbtotal. TML is accumulated mostly in wetland soils and seems to be stable under anoxic conditions for a long time. In upland soils, TML decomposes rapidly. Only small amounts of TML are transferred from soils into runoff.

Biogeochemistry of organotin compounds and tin in a forested catchment in Germany

Organotin compounds (OTC) are highly toxic pollutants that have been shown to affect many aquatic ecosystems. Little is known about the input and fate of OTC in terrestrial ecosystems. Here, soil pools, concentrations and fluxes in bulk precipitation, throughfall, fog, litterfall and runoff of OTC and Sn total were investigated in a forested ecosystem ( Picea abies, Karst.) in NE Bavaria, Germany. The concentrations of OTC and Sn total were generally in the order fog>throughfall>bulk precipitation. Average concentrations of OTC total ranged from 57 ng Sn l −1 in fog to 5.8 ng Sn l −1 in bulk precipitation. Concentrations of Sn total were in the same order but between 490 ng Sn l −1 in fog and 140 ng Sn l −1 in bulk precipitation, on average. Average OTC total concentrations in litterfall were 12.9 ng Sn g −1 and those of Sn total in litterfall 38 ng Sn g −1. All OTC concentrations in runoff were lower than in bulk precipitation, while those of Sn total were similar to the concentrations in bulk precipitation. Monobutyltin was the dominating OTC in bulk precipitation, throughfall, fog and litterfall, but was seldom detected in the runoff. The annual total deposition of OTC total (calculated as throughfall+litterfall) was 172 mg Sn ha −1 year −1, with 45 mg Sn ha −1 year −1 represented by litterfall. The annual runoff from the catchment of OTC total amounted to 25 mg Sn ha −1 year −1. The total deposition of Sn total was 4.9 g Sn ha −1 year −1, of which 0.2 g Sn ha −1 year −1 was litterfall. The annual runoff of Sn total was 2.4 g Sn ha −1 year −1. The mass balance showed a high retention of OTC and Sn total in the catchment. The forest soils act as a strong sink for OTC and Sn total. Only small amounts of deposited OTC are released to runoff. The ratio of soil pools to annual accumulation for total OTC (46 years) indicates that OTC inputs have been occurring already for many decades or have been substantially higher in the past than today.

Earthworm Invasion, Fine-root Distributions, and Soil Respiration in North Temperate Forests

The efflux of carbon from soils is a critical link between terrestrial ecosystems and the atmosphere. Current concerns about rising atmospheric carbon dioxide (CO2) concentrations highlight the need to better understand the dynamics of total soil respiration (TSR, sum of root and heterotroph respiration) in changing environments. We investigated the effects of exotic earthworm invasion on TSR, fine-root distributions, and aboveground litterfall flux in two sugar maple-dominated forests in two locations in New York State, USA. The Arnot Forest in central New York was harvested in the late 19th century and has no history of cultivation. Tompkins Farm in eastern New York regenerated following abandonment from cultivation approximately 75 years ago. Arnot had 20% higher total soil CO2 efflux (880 g C m−2year−1) than Tompkins (715 g C m−2year−1). The presence of earthworms had no influence on TSR at either location. However, fine-root (< 1 mm diameter) biomass in earthworm plots (350 g/m2) was significantly lower than in worm-free reference plots (440 g/m2) at Arnot. Fine-root nitrogen (N) concentrations were not influenced by earthworms, and total fine-root N content was significantly reduced in the presence of earthworms at Arnot. Our results indicate that the presence of exotic earthworms is not presently affecting net C emission from soil in these forests. They also suggest a change in root function in earthworm plots that is not associated with higher fine-root N concentration, but that increases efficiency of nutrient uptake and also may enhance the belowground supply of C for heterotroph metabolism.

Dissolved and particulate carbon dynamics in a cool‐temperate forested basin in northern Japan

AbstractWhen evaluating forest functions and their responses to climate change, it is important to clarify carbon dynamics in forested basins. Carbon fluxes in litter fall, throughfall, soil solution, groundwater and stream water were determined from November 1997 to October 1998 for a forest stream ecosystem in a cool‐temperate forested basin in the Tomakomai Experimental Forest, Hokkaido University, northern Japan. The annual carbon input to the stream by litter fall was 0·23 gC m−2 year−1, with the greatest flux in the autumn. Owing to biological decomposition of litter in the stream, the carbon concentration in stream particulate organic matter (&gt;0·45 µm) decreased as particle size decreased. The upstream carbon flux was 1·9 gC m−2 year−1, and the annual carbon output in stream water was 7·6 gC m−2 year−1, mainly as dissolved inorganic carbon (DIC), resulting in net carbon output in stream water of 5·7 gC m−2 year−1. The mean dissolved organic carbon (DOC) concentration in soil solution was higher than that in throughfall and stream water. The estimated annual carbon flux from soil in deep (about 1·5 m) soil solution was 4·4 gC m−2 year−1. About 40% of DOC in soil solution was decomposed and converted to DIC in groundwater. These results indicate that carbon dynamics in the forest stream were affected strongly by decomposition of organic matter in the soil–groundwater–stream continuum and by the hydraulic conditions, which are characterized by a large pool of groundwater and high soil permeability. Copyright © 2001 John Wiley &amp; Sons, Ltd.