Litter Nutrient Research Articles

Foliar Nutrient Composition of 19 Tree Species Grown on a Phytocapped Landfill Site

An alternative landfill capping technique ‘Phytocapping’ (establishment of perennial plants on a layer of soil placed over the waste) was trailed at Rockhampton, Australia, as it is eco-friendly, less expensive and socially acceptable. In this capping, trees are used as ‘Bio-pumps and Screens’ and soil cover as ‘Storage’. They together minimise water percolation leading to reduced leachate production. Twenty one tree species were grown on two depths of soil (700 mm and 1400 mm) and monitored for their growth and their ability to restrict water infiltration through the waste. A very common question raised by most scientist and engineers is growth and survival of tree species in a landfill environment. Hence to determine the conditions and health of the tree species, foliar and foliar litter nutrient concentrations were measured in all the tree species grown on the phytocapped landfill site. The 3 year-old trees showed slightly elevated levels of nutrient and this will continue as the trees mature and develop more roots. The trees in the 700 mm soil cover contained slightly higher leaf concentrations of nutrients due to the possible closer proximity of their roots to the waste.

Decomposition of leaf litter of some evergreen broadleaf trees in Korea

Litter decomposition is an important process in terrestrial ecosystem. However, studies on decomposition are rare, es- pecially in evergreen broadleaf trees. We collected the leaf litter of five evergreen broadleaf trees ( Daphniphyllum mac- ropodum, Dendropanax morbifera, Castanopsis cuspidata var. thunbergii, Machilus thunbergii and Quercus acuta), and carried out a decomposition experiment using the litterbag method in Ju-do, Wando-gun, Korea for 731 days from De- cember 25, 2011 to December 25, 2013. Among the five experimental tree species, C. cuspidata var. thunbergii distribution was limited in Jeju Island, and D. macropodum was distributed at the highest latitude at Mt. Baekyang (N 35°40'). About 2% of the initial litter mass of D. macropodum and D. morbifera remained, while 20.9% remained for C. cuspidata var. thunbergii, 30.4% for M. thunbergii, and 31.6% for Q. acuta. D. macropodum litter decayed four times faster (k = 2.02 yr -1 ) than the litter of Q. acuta (k = 0.58 yr -1 ). The decomposition of litter was positively influenced by thermal climate such as accumulated mean daily air temperature (year day index) and precipitation, as well as by physical characteristics such as thickness (R 2 =0.939, P = 0.007) and specific leaf area (SLA) ( R 2 = 0.964, P = 0.003). The characteristics of chemical composition such as lignin (R 2 = 0.939, P = 0.007) and water-soluble materials (R 2 = 0.898, P = 0.014) showed significant correlations with litter decomposition. However, the nutrients in litter showed complicated species-specific trends. The litter of D. macropodum and D. morbifera had fast decomposition despite their low nitrogen concentration and high C/N ratio. This means that the litter decomposition was more strongly affected by physical characteristics than chemical composition and nutrient content. On the other hand, the litter of Q. acuta which had the slowest decay rate had a high amount of N and low C/N ratio. Thus, the decomposition of Q. acuta litter was more affected by the P content of the litter than the N content, although all litter had similar physical characteristics.

The importance of litter traits and decomposers for litter decomposition: a comparison of aquatic and terrestrial ecosystems within and across biomes

Summary Plant leaf litter comprises the major common source of energy and nutrients in forested soil and freshwater ecosystems world‐wide. However, despite the similarity of physical and biochemical processes, generalizations across aquatic and terrestrial ecosystems regarding litter decomposition drivers remain elusive. We re‐analysed data from a published field decomposition experiment conducted in two ecosystems (forest floors and streams) across five biomes (from the tropics to subarctic) with increasing decomposer community complexity (microbes, microbes and mesofauna, microbes and meso‐ and macrofauna). Using a wide litter quality gradient (15 litter combinations), we aimed to disentangle the roles of decomposer community complexity from that of leaf litter traits (18 traits encompassing four broad trait categories: nutrients, C quality, physical structure and stoichiometry) on litter C and N loss. Comparisons of decomposition drivers between ecosystems were evaluated across and within biomes. Differences in environmental conditions (e.g. climate, soil/water fertility) and litter nutrients – with a particular focus on Mg and Ca – across biomes were the major drivers of litter C loss in both ecosystems, but decomposer complexity also played a prominent role in streams. Within biomes, we observed consistent effects of litter nutrients and stoichiometry on litter C and N loss between ecosystems, but the effects of decomposer complexity differed between streams and forest floors in the temperate, Mediterranean and tropical biomes. Our results highlight that, beyond the litter traits commonly identified as controlling decomposition (e.g. C, N and lignin), micronutrients (e.g. Mg and Ca) can also play an important, and globally consistent, role in both aquatic and terrestrial ecosystems. In addition, in forest streams the complexity of decomposer communities had similar importance as litter traits for predicting litter C and N turnover across all five biomes. The identification of common drivers in our large‐scale ecosystem comparison suggests a basis to develop common models across aquatic and terrestrial ecosystems for C and N dynamics during decomposition. Future modelling efforts should account for the global similarities (litter micronutrient effects) and biome‐level differences (contingent decomposer effects) found between ecosystems.

Mechanisms linking fungal conditioning of leaf litter to detritivore feeding activity

Saprotrophic fungi are one of the primary groups of organisms responsible for decomposition and nutrient cycling processes. Aside from their direct effects on litter decomposition, these organisms may indirectly affect litter invertebrate activity via fungal-mediated conditioning (i.e. ‘priming’) of litter substrates. While this priming effect is generally assumed to take place, this assumption is based on correlative observations and feeding preference trials rather than experimental discrimination of the mechanisms driving the process. We used a microcosm experiment of brown-rot (Fistulina hepatica, Fomitopsis lilacinogilva) and white-rot (Pycnoporus coccineus) fungi on two sclerophyllous leaf litters (Eucalyptus loxophleba and Acacia acuminata) to test if a fungal-mediated change in plant litter increased the nutritive value of the food source, and if a change in cell-wall (structural) compounds reduced the toughness of leaves, resulting in increased feeding activity by invertebrates. Brown- and white-rot fungal colonization had significant and diverse effects on the total nutrient concentrations and proportions of cellulose, lignin and hemicellulose of the leaf litter–fungi complex. However, significant decreases in leaf toughness and increases in mass loss and leaf fragmentation associated with detritivorous millipede (Ommatoiulus moreletii) activity only occurred in white-rot primed microcosms relative to the control. The mechanisms by which the white-rot fungus affected both leaf toughness and millipede feeding activity differed between leaf litters. In E. loxophleba microcosms, reduced leaf toughness and increased millipede grazing were mediated by relative changes in litter inorganic chemistry, rather than structural compounds, whereas in A. acuminata microcosms the effects of fungal priming were not mediated by either. These results suggest that, in the early stages of decomposition, fungal priming effects on leaf litter nutrients are a more important determinant of litter–invertebrate interactions than changes to litter structural compounds. Furthermore, different species of fungi interact with different litter types and invertebrates in functionally different ways.

Subsurface Band Application of Poultry Litter and Its Influence on Phosphorus Concentration and Retention after Runoff from Permanent Pastures.

Excessive phosphorus (P) loss from agricultural fields is a major cause of eutrophication to rivers, lakes, and streams. To mitigate P loss after poultry litter (PL) applications, technology is being developed to apply litter below the soil surface. Thus, research was conducted to evaluate the effects of subsurface PL banding on soil P under pasture management. Treatments consisted of surface-broadcasted or subsurface-banded PL (38 cm apart) at 9 Mg ha, surface-broadcasted commercial fertilizer (CF; urea and triple superphosphate blend) at N (330 kg N ha) and P (315 kg N ha) application rates equivalent to PL, and a nonfertilized control. Runoff events lasting 40 min were simulated in bermudagrass ( L.) pastures on common soil types of the Coastal Plain and Piedmont regions. One day later, Mehlich-1 and water-soluble P concentrations in soil were measured at depths of 0 to 5 cm and 5 to 10 cm to determine P distribution and movement. The greatest P concentrations were observed at the shallow depth for all treatments. Phosphorus measurements at the point of application for PL bands were greater than for the surface-applied treatments (PL and CF) and control. Measurements between subsurface PL bands were slightly higher than the control but were statistically similar, suggesting that this application method can abate short-term P movement. Results obtained from this study show that subsurface band applying PL could increase P retention and reduce movement by precluding contact between surface water and litter nutrients.

Changes in litter quality caused by simulated nitrogen deposition reinforce the N‐induced suppression of litter decay

Rates of nitrogen (N) deposition are increasing in industrialized and rapidly developing nations. Simulated N deposition suppresses plant litter decay rates, in particular for low quality (high lignin) litter. Litter quality is a primary driver of litter decomposition; however, it is not clear how changes in litter quality caused by long‐term ecosystem exposure to chronic N additions interact with altered soil N‐availability to influence litter decay dynamics. To document the effects of simulated N deposition on litter quality, we conducted a meta‐analysis of available litter nutrient data from simulated N deposition experiments in temperate forests. To directly test whether changes in litter quality caused by N deposition affect decay rates, we also conducted a reciprocal litterbag study in an existing N addition experiment, where a northern hardwood forest has been exposed to simulated N deposition for more than 20 years. The experiment enabled us to disentangle the effects of N additions, litter quality, and their interactions on litter decay dynamics. We measured litter mass loss and extracellular enzyme activities after one and two years of decomposition. The meta‐analysis demonstrated that simulated N deposition causes decreases of leaf Al, B, Ca, Mg, Mn, P, and Zn concentrations, and increased leaf N concentrations. Moreover, higher cumulative amounts of simulated N deposition result in greater decreases of leaf Ca and Mn concentrations. In the field experiment, litter originally collected from N‐enriched plots exhibited similar N‐induced nutrient changes as observed in our meta‐analysis and also had lower lignolytic enzyme activities and decay rates than litter collected from control plots. The decreased litter decay rates observed with simulated N deposition were a result of the combined effects of the N fertilization itself and the historical effects of N deposition on tree litter chemistry. The data suggest that changes in litter quality caused directly by long‐term N enrichment reinforce the negative effects of simulated N deposition on litter decay, particularly for high lignin species. The slowed decay associated with changes in litter quality caused by N enrichment itself may partly explain the accumulation of organic matter previously observed at ours and at other simulated N deposition experiments.

Differences in Ecosystem Carbon Distribution and Nutrient Cycling Linked to Forest Tree Species Composition in a Mid-Successional Boreal Forest

In the boreal forest of Alaska, increased fire severity associated with climate change is expanding deciduous forest cover in areas previously dominated by black spruce (Picea mariana). Needle-leaf conifer and broad-leaf deciduous species are commonly associated with differences in tree growth, carbon (C) and nutrient cycling, and C accumulation in soils. Although this suggests that changes in tree species composition in Alaska could impact C and nutrient pools and fluxes, few studies have measured these linkages. We quantified C, nitrogen, phosphorus, and base cation pools and fluxes in three stands of black spruce and Alaska paper birch (Betula neoalaskana) that established following a single fire event in 1958. Paper birch consistently displayed characteristics of more rapid C and nutrient cycling, including greater aboveground net primary productivity, higher live foliage and litter nutrient concentrations, and larger ammonium and nitrate pools in the soil organic layer (SOL). Ecosystem C stocks (aboveground + SOL + 0–10 cm mineral soil) were similar for the two species; however, in black spruce, 78% of measured C was found in soil pools, primarily in the SOL, whereas aboveground biomass dominated ecosystem C pools in birch forest. Radiocarbon analysis indicated that approximately one-quarter of the black spruce SOL C accumulated prior to the 1958 fire, whereas no pre-fire C was observed in birch soils. Our findings suggest that tree species exert a strong influence over C and nutrient cycling in boreal forest and forest compositional shifts may have long-term implications for ecosystem C and nutrient dynamics.

Leaf litter resource quality induces morphological changes in wood frog (Lithobates sylvaticus) metamorphs.

For organisms that exhibit complex life cycles, resource conditions experienced by individuals before metamorphosis can strongly affect phenotypes later in life. Such resource-induced effects are known to arise from variation in resource quantity, yet little is known regarding effects stemming from variation in resource quality (e.g., chemistry). For larval anurans, we hypothesized that variation in resource quality will induce a gradient of effects on metamorph morphology. We conducted an outdoor mesocosm experiment in which we manipulated resource quality by rearing larval wood frogs (Lithobates sylvaticus) under 11 leaf litter treatments. The litter species represented plant species found in open- and closed-canopy wetlands and included many plant species of current conservation concern (e.g., green ash, common reed). Consistent with our hypothesis, we found a gradient of responses for nearly all mass-adjusted morphological dimensions. Hindlimb dimensions and gut mass were positively associated with litter nutrient content and decomposition rate. In contrast, forelimb length and head width were positively associated with concentrations of phenolic acids and dissolved organic carbon. Limb lengths and widths were positively related with the duration of larval period, and we discuss possible hormonal mechanisms underlying this relationship. There were very few, broad differences in morphological traits of metamorphs between open- and closed-canopy litter species or between litter and no-litter treatments. This suggests that the effects of litter on metamorph morphology are litter species-specific, indicating that the effects of changing plant community structure in and around wetlands will largely depend on plant species composition.

Decomposition of 51 semidesert species from wide-ranging phylogeny is faster in standing and sand-buried than in surface leaf litters: implications for carbon and nutrient dynamics

Higher than expected litter decomposition rates have been observed in dry, sunny environments due to photochemical or physical degradation. However, our understanding of carbon and nutrient fluxes of standing and buried litters compared to surface litter in such areas is still scarce. We sampled leaf litters from 51 species in a semiarid dune ecosystem and incubated them in three positions: surface, sand-buried and simulated standing. Decomposition was much faster in buried litter and somewhat faster in simulated standing litter than in surface litter. This pattern was independent of the incubation period, phylogenetic group or growth form. Litter position and incubation period significantly impacted litter nutrient dynamics. The nitrogen (N) and phosphorus (P) losses were faster in buried and simulated standing litters than in surface litter. The N loss was slower than P loss in 6-month decomposed litter but the former was relatively faster than the latter in the second phase up to 12 months of incubation. Our study shows that substantial mass and nutrient losses in simulated standing and buried litters can be a candidate explanation why drylands have higher carbon and nutrient fluxes than expected based on surface litter decomposition data alone.

Litterfall and nutrient return along a disturbance gradient in a tropical montane forest

Litterfall plays an important role in nutrient cycling and maintenance of soil fertility in terrestrial ecosystems. Annual and seasonal variation in litterfall have been investigated in various habitats, however, seasonality in nutrient supply is less well documented. We studied litterfall over two years and seasonal litter nutrient input over one year across a tropical disturbance gradient from mature forest to monoculture tea plantation. Total litter production in the mature forests and regenerating forests was not significantly different. However, tea plantations had significantly lower litter production. Total litterfall in forest habitats showed a clear seasonal pattern with a peak during the dry season (Mar.–May), as has been reported for other tropical seasonal forests. Contrary to expectations, there was no significant difference in litter nutrient concentrations across the disturbance gradient, although there was a substantial change in plant species composition. Litter nutrient concentrations also did not vary significantly across seasons, again contrary to our expectations. Thus, nutrient input was driven solely by the seasonal litterfall pattern. Our results suggest that at a landscape scale turnover in species composition linked to anthropogenic disturbance may not always lead to changes in litter quality, presumably because a similar spectra of leaf types may exist across communities. Seasonal litterfall patterns, which have been more commonly studied, may prove a reasonable proxy for nutrient input in forests.

A Survey of Terrestrial Gastropods of the Alice L. Kibbe Life Science Station in West-Central Illinois

Abstract Terrestrial gastropods are vital components in terrestrial ecosystems and are thought to play a key role in litter decomposition and nutrient release in temperate and tropical forests. As part of an effort to expand our knowledge of gastropod diversity in west-central Illinois, we conducted a survey of terrestrial gastropods of the Alice L. Kibbe Life Science Station in west-central Illinois from April to May 2013. We sampled at 9 different sites within representative stands of 5 of the prevalent forest types at the station and documented a total of 20 species representing 11 families and 17 genera, including 12 new records for Hancock County. The Polygyridae was the most diverse family (7 species). Although this study sheds additional light on the terrestrial gastropod fauna of west-central Illinois, further surveys are needed to establish baseline data and assess future trends in response to habitat modification and climate change throughout the region.

Isolating the effects of precipitation, soil conditions, and litter quality on leaf litter decomposition in lowland tropical forests

Global change drivers such as climate change influence decomposition by altering extrinsic site conditions and intrinsic litter traits. This study aimed to quantify the relative importance of these two pathways for litter decomposition in tropical forests. The effects of soil nutrient availability, mean annual precipitation (MAP), and leaf litter chemistry on decomposition were isolated by measuring mass loss of leaf litter from 10 tropical tree species transplanted to 19 sites along independent gradients of soil fertility and precipitation in Panama. Across species, litter nitrogen (N) content ranged from 7.1 to 13 mg N g−1 and phosphorus (P) from 0.077 to 0.56 mg P g−1. Across sites, soil N content ranged from 1.7 to 5.5 g N kg−1, soil P from 77 to 1500 mg P kg−1, and MAP from 1900 to 2700 mm. Variation in leaf litter mass loss was explained largely by litter species identity (55 %). Site only explained a small, but significant, amount of variance (6.5 %); soil C:N ratio explained this response. Notably, neither litter nutrient content nor MAP were significant predictors of litter decomposition. Changes in tree species composition may influence decomposition rates more than changes to site conditions.

Comparing differences in early-stage decay of macrophyte shoots between in the air and on the sediment surface in a temperate freshwater marsh

Litter decay is a fundamental process in ecosystem carbon flux and nutrient cycling. In wetlands, shoot litters on the sediment surface and in the air are important components of the detritus pool. We used the litterbag method to compare mass losses and nutrient dynamics of culms, sheaths, and leaves from Deyeuxia angustifolia on the sediment surface and in the air from October 2011 to October 2012 in a freshwater marsh in Northeast China. The mass losses for the three litters in the air were only approximately 3% and less than that on the sediment surface after 180 days of decay, but increased to 16–44% after one year of decay and thus exceeded or approached that of surficial corresponding litters. For leaves and sheaths, the increased nutrient (nitrogen and phosphorus) concentrations of aerial litters resulted in an approximately 10% increase in the nutrient amounts after 180 days of decay, which was greater than that of surficial corresponding litters; however, surficial litters exhibited a greater increase or a lesser decrease of nutrient amounts than did aerial corresponding litters after one year of decay. For culms, the litter nutrient amounts in the air were always more or not less than those on the sediment surface during one year of decay, although effects of the litter position on nutrient concentrations were negligible (for nitrogen) or varied over time (for phosphorus). Overall, the litter position significantly affected the decay processes in this marsh. Therefore, it is essential to consider litter mass and decay processes at different positions to comprehensively understand carbon cycle and nutrient turnover in temperate freshwater marshes.

Tree patch distribution drives spatial heterogeneity of soil traits in cork oak woodlands

Spatial heterogeneity of soil resources is linked to tree patch distribution in Mediterranean cork oak woodlands. Tree patch distribution modifies soil traits by varying litterfall inputs due to different tree covers. The spatial heterogeneity of soil resources affects the structure and functioning of the different plant communities on ecosystems. In Mediterranean oak woodlands, the scattered trees play a key role in this spatial heterogeneity and might strongly influence ecosystem functioning and its productivity. To assess the influence of the spatial pattern of trees and litter nutrient content on the spatial heterogeneity of soil properties. We used a combination of geostatistical techniques and a linear mixed model to evaluate the spatial heterogeneity of soil and the seasonal and spatial variability of litter nutrient content, respectively. Soil parameters showed a high spatial heterogeneity. Tree cover was positively related with soil pH, and the organic matter, N, K, and Ca soil content. The return of nutrients to the soil via leaf fall had a marked seasonality and a high spatial variability, but this spatial variability had no effect on the spatial pattern of soil resources. The spatial heterogeneity of soil in cork oak woodlands is mainly driven by tree patches distribution. The importance of the spatial heterogeneity of soil resources and the spatial pattern of trees on the functioning of the dehesa ecosystem makes it necessary to include them in plant nutrition studies and modeling approaches in these ecosystems.

Productivity-efficiency tradeoffs in tropical gallery forest-savanna transitions: linking plant and soil processes through litter input and composition

Vegetation gradients in Central Brazil encompass sharp transitions from savanna to forests, representing an iconic example of how interactions between plants and soils regulate biogeographical boundaries. Here we describe how canopy productivity regulates nutrient inputs to soils, affecting fertility and influencing ecosystem distribution. Based on soil and litter systematically collected during 12 months along a gallery forest-savanna transition, we determined associations between canopy cover (leaf area index—LAI) and the (re)cycling of essential macronutrients. This evaluation was aimed at aggregating information about biogeochemical controls of ecosystem distribution/productivity, to support conservation and management efforts in the region. We confirmed two hypotheses: (i) nutrient inputs via litterfall are significantly higher in forest than in adjacent savanna, and (ii) litter quality varies with canopy productivity and litter nutrient concentrations influence soil fertility reinforcing forest and savanna as alternate stable states. These observations delineate a productivity-efficiency tradeoff in which savannas communities are more efficient in the use of limiting nutrients, yet, less productive than forest communities. The relative importance of different nutrients, apparent on recovery rates in the litter regressed against LAI, revealed that the expansion of forest ecosystems is limited by P > Mg > K > N, with highest conservation observed for P. Differences in Ca input were also significant among ecosystems, but depended solely on the amount of deposited litter, with no differences in recovery rates observed between forests and savannas. A tradeoff-based framework could be used to predict ecotonal stability in the region, with transitions between savannas and forests marked by clear changes in species composition, productivity, litter deposition, and soil fertility.

Effects of litter traits, soil biota, and soil chemistry on soil carbon stocks at a common garden with 14 tree species

Tree species interact with soil biota to impact soil organic carbon (C) pools, but it is unclear how this interaction is shaped by various ecological factors. We used multiple regression to describe how ~100 variables were related to soil organic C pools in a common garden experiment with 14 temperate tree species. Potential predictor variables included: (i) the abundance, chemical composition, and decomposition rates of leaf litter and fine roots, (ii) species richness and abundance of bacteria, fungi, and invertebrate animals in soil, and (iii) measures of soil acidity and texture. The amount of organic C in the organic horizon and upper 20 cm of mineral soil (i.e. the combined C pool) was strongly negatively correlated with earthworm abundance and strongly positively correlated with the abundance of aluminum, iron, and protons in mineral soils. After accounting for these factors, we identified additional correlations with soil biota and with litter traits. Rates of leaf litter decomposition, measured as litter mass loss, were negatively correlated with size of the combined soil organic C pool. Somewhat paradoxically, the combined soil organic C pool was also negatively related to the ratio of recalcitrant compounds to nitrogen in leaf litter. These apparent effects of litter traits probably arose because two independent components of litter “quality” were controlling different aspects of decomposition. Leaf litter mass loss rates were positively related with leaf litter calcium concentrations, reflecting greater utilization and depolymerization of calcium-rich leaf litter by earthworms and other soil biota, which presumably led to greater proportional losses of litter C as CO2 or dissolved organic C. The fraction of depolymerized and metabolized litter that is ultimately lost as CO2 is an inverse function of microbial C use efficiency, which increases with litter nutrient concentrations but decreases with concentrations of recalcitrant compounds (e.g. lignin); thus, high ratios of recalcitrant compounds to nitrogen in leaf litter likely caused a greater fraction of depolymerized litter to be lost as CO2. Existing conceptual models of soil C stabilization need to reconcile the effects of litter quality on these two potentially counteracting factors: rates of litter depolymerization and microbial C use efficiency.

Environmental factors and traits that drive plant litter decomposition do not determine home‐field advantage effects

SummaryThe ‘home‐field advantage’ (HFA) hypothesis predicts that plant litter is decomposed faster than expected underneath the plant from which it originates (‘home’) than underneath other plants (‘away’), because decomposer communities are specialized to break down litter from the plants they associate with. However, empirical evidence shows that the occurrence ofHFAis highly variable, and the reasons for this are little understood.In our study, we progress our understanding by investigating whetherHFAis stronger for more recalcitrant litter types and under colder conditions and how soil properties and plant functional traits affect the magnitude and direction ofHFA.In subarctic tundra in northernSweden, we set up a reciprocal transplant litter decomposition experiment along an elevational gradient where three highly contrasting vegetation types (heath, meadow andSalix) occur at all elevations, and where temperature decreases strongly with elevation. In this study, we used a litter bag approach where litters from each elevation × vegetation type combination were decomposed in all combinations of elevation × vegetation type. We also measured community‐level plant functional traits, such as leaf and litter nutrient content. We determined soil biotic and abiotic properties, such as microbial biomass and soil nutrient content, in soil cores collected for each elevation × vegetation type combination.We found that mass loss increased with plant and litter nutrient content and with soil temperature. In contrast, the occurrence ofHFAwas limited in our study system, and its magnitude and direction could not be explained by vegetation type, elevation, plant traits or soil properties, despite these factors serving as powerful drivers of litter mass loss in our study.We conclude that although vegetation type and climate are major drivers of litter mass loss, they do not emerge as important determinants ofHFA. Therefore, while rapid shifts in plant community composition or temperature due to global change are likely to influence litter mass loss directly by altering environmental conditions, plant trait spectra and litter quality, indirect effects of global change resulting from decoupling of specialist interactions between litter and decomposer communities appear to be of less importance.

Composting and gypsum amendment of broiler litter to reduce nutrient leaching loss.

The effect of composted litter relative to fresh litter on leaching losses of nutrients has not been well documented. Fresh and composted broiler litter was surface-applied to bermudagrass (hay) [ (L.) Pers.] established in undisturbed soil columns based on N need of the grass in the presence or absence of flue gas desulfurization (FGD) gypsum to evaluate an approach to reduce broiler litter nutrient leaching potential. Columns were periodically leached and biomass was harvested during the 60-d experiment. Total N applied to bermudagrass from broiler litter was 320 kg ha. Gypsum was mixed with fresh and composted litter at the rate based on 20% of litter weight. For composted broiler litter, NO-N, P, K, Cu, and Zn contents in the leachate obtained from the first leaching event were 58, 50, 40, 32, and 38% less than fresh broiler litter, respectively. Significant decreases in NO-N (13%), P (53%), Cu (17%), and Zn (28%) in leachate were obtained when gypsum was mixed with fresh broiler litter. Fresh broiler litter and composted broiler litter applications increased bermudagrass growth compared with the control and gypsum significantly increased yields when mixed with broiler litter. Composted broiler litter application significantly increased N and organic C in the soil compared with fresh litter. Results demonstrate that coapplication of composted broiler litter with FGD gypsum provide the most effective management option for minimizing leaching losses of nutrients while sustaining crop productivity.

Nutrient Composition in Litter Fall in Northern Louisiana Hardwood Deciduous Forests

Minor stream bottoms (alluvial floodplains) in the southeastern United States contain large areas of hardwood forests which are a potential sink for upstream nutrients. As a sink, they serve an important role in reducing the loss of nutrients from the sites via the watershed. However, little is known about nutrients stored in forest litter that have the potential to be cycled back to the forest or lost through removal from the site. Three hardwood stands of varying management regimens that span common scenarios found in north Louisiana were sampled for nutrient concentration and quantity in falling litter including leaf, woody, and other debris. Across sites, the well-drained site constitutively contributed more nutrients in litter than the poorly drained sites. Also, the sampling time spanning from March to October had the most litter fall and subsequent nutrient discharge from the trees. Of the five nutrients measured, nitrogen was the largest component followed by potassium. These features in nutrient quantity have broad implications for nutrient management based on site and timing of timber removal. This study provides novel nutrient levels in litter fall of hardwood forests typical along minor stream bottoms.

Leaf litter nutrient uptake in an intermittent blackwater river: influence of tree species and associated biotic and abiotic drivers

Summary Organic matter may sequester nutrients as it decomposes, increasing in total N and P mass via multiple uptake pathways. During leaf litter decomposition, microbial biomass and accumulated inorganic materials immobilize and retain nutrients, and therefore, both biotic and abiotic drivers may influence detrital nutrient content. We examined the relative importance of these types of nutrient immobilization and compared patterns of nutrient retention in recalcitrant and labile leaf litter. Leaf packs of water oak (Quercus nigra), red maple (Acer rubrum) and Ogeechee tupelo (Nyssa ogeche) were incubated for 431 days in an intermittent blackwater stream and periodically analysed for mass loss, nutrient and metal content, and microbial biomass. These data informed regression models explaining temporal changes in detrital nutrient content. Informal exploratory models compared estimated biologically associated nutrient stocks (fungal, bacterial, leaf tissue) to observed total detrital nutrient stocks. We predicted that (i) labile and recalcitrant leaf litter would act as sinks at different points in the breakdown process, (ii) plant and microbial biomass would not account for the entire mass of retained nutrients, and (iii) total N content would be more closely approximated than total P content solely from nutrients stored in leaf tissue and microbial biomass, due to stronger binding of P to inorganic matter. Labile litter had higher nutrient concentrations throughout the study. However, lower mass loss of recalcitrant litter facilitated greater nutrient retention over longer incubations, suggesting that it may be an important long‐term sink. N and P content were significantly related to both microbial biomass and metal content, with slightly stronger correlation with metal content over longer incubations. Exploratory models demonstrated that a substantial portion of detrital nutrients was not accounted for by living or dead plant and microbial biomass, especially in the case of N. This suggests increased importance of both N and P sorption to inorganic matter over time, with possible additional storage of N complexed with lignin. A better understanding of the influence of these mechanisms may improve our understanding of detrital nutrient uptake, basal resource quality and retention and transport of nutrients in aquatic ecosystems.