Litter Nutrient Concentrations Research Articles

Vegetation drives soil microbial metabolic limitation through modifications of soil properties and microbial biomass during desert grassland-shrubland state anthropogenic transition

Shrub encroachment became widespread in grass-dominated ecosystem regions. However, there is still limited attention on the changes in plant-soil system C:N:P stoichiometry and soil microbial metabolic limitation status caused by anthropogenic encroachment of shrubs in the desert grassland of northwest China, as well as their driving mechanisms. In this study, we quantified the C:N:P stoichiometry of plant-litter-soil, soil physicochemical properties, microbial biomass, extracellular enzyme activities, and microbial metabolic limitation status during the anthropogenic transition from grassland to shrubland. Here, our results showed that anthropogenic shrub encroachment reduced plant C, soil water, and soil nutrient contents while increasing N and P contents in both plants and litter. The correlation also suggested that litter nutrient content relied on plant nutrients, while plants depleted soil nutrients. Secondly, with the gradient of shrub encroachment, the stoichiometry (except for soil C:N ratio) of plant-litter-soil showed a decreasing trend and a positive correlation. Furthermore, our study indicated that shrub encroachment reduced soil microbial biomass and extracellular enzyme activities, altering microbial stoichiometry and patterns of enzyme allocation. Redundancy analysis revealed that microbial biomass, extracellular enzyme activities, and stoichiometry were mainly driven by soil water content, nutrient content, and nutrient stoichiometry. The vector-threshold element ratio model revealed that along the transition from desert grassland to shrubland, soil microbial nutrient limitation shifted from P to N, while energy (C) limitation intensified. The soil microbial metabolic limitation was driven jointly by plants and litter through modifications of soil properties and microbial biomass. Additionally, soil properties played a crucial role among these factors. In summary, over the past 40 years, shrub anthropogenic encroachment has formed a desert grassland-shrub mosaic landscape, depleted soil water and nutrient contents, and altered ecological stoichiometry and microbial metabolic limitation patterns in northwest China. This study provides new insights into the C, N, and P cycling in plant-soil systems following shrub encroachment caused by global climate change and anthropogenic disturbances.

Nitrogen Deposition Reduces the Rate of Leaf Litter Decomposition: A Global Study

The litter decomposition of plant leaves is a vital process in carbon (C) and nitrogen (N) cycling in global terrestrial ecosystems. However, previous assessments of the key determinants of the N deposition effects of litter decomposition have been more controversial. In this meta-analysis, we compared the overall effects of N addition on the litter decomposition rates, litter nutrient content (C and N), and litter constituent (lignin and cellulose) residual rates using a log response ratio approach. Our results showed that exogenous N addition increased the N content and inhibited lignin degradation in litter. N deposition decreased the leaf litter decomposition rate by increasing the lignin and N residues and decreasing the litter C content and soil pH. The analysis also concluded that the initial litter C/N ratio, lignin content, and soil pH were main factors in mediating the effect of N deposition on litter decomposition rate. Overall, the results of this study indicate that N deposition can slow decomposition rates by inhibiting N release and lignin degradation of litter. Notably, these results emphasize that the effect of N deposition on litter decomposition mainly depends on the endogenous quality of the litter and soil pH in the decomposition environment.

The Nutrient Content of Litter and Manure from Different Poultry Systems—Updating and Establishing the Nutrient Profile

Representative samples of litter and/or manure from 12 of the most common poultry systems were collected and analysed to provide an accurate nutrient profile from each system. For many systems (turkeys, broilers under indirect heating systems, and pullets), there were no previous values with which to compare composition, but for other systems (broiler breeders and layers), nitrogen and phosphate content were lower as a result of changes in diet and advancements in genetics and management. Nitrogen and phosphate output per 1000 birds was calculated for each system using analysed values for nitrogen and phosphate and measured litter/manure output. Due to a lack of data, it was not possible to compare the nutrient profile of all systems with published values, but where this was possible, some important differences were apparent. For example, the nitrogen and phosphate contents of BB (0–18 weeks) litter were 31% lower and 73% higher than current standard values. Similar differences were also observed for BB (18–60 weeks) (26% lower in nitrogen and 51% higher in phosphate). Turkey litter was found to contain 14% less nitrogen and 37% less phosphate than standard values. Litter from pullet systems contained higher levels of DM (72%), nitrogen, and phosphate than standard values. Litter from free range laying systems also contained higher DM (46%), nitrogen, and phosphate than standard values. This information will be useful in updating environmental legislation and ensuring that poultry producers are able to calculate accurate nutrient management plans for their enterprises. This study also established relations between litter/manure dry matter (DM) and nutrient profile, meaning that this simple measured parameter can be used to predict nutrient profile. The strongest relations were observed between DM and N (R2 = 0.65), DM and phosphate (R2 = 0.53), and DM and MgO (R2 = 0.69). The weakest relation was observed between DM and WSP content (R2 = 0.21), although still significant (p = 0.046). It was concluded that it is necessary to consider the relation within individual systems when using DM as a predictor of nutrient profile rather than using a combined system approach. The water-soluble phosphorus (WSP) content of litter/manure was determined and a baseline was established for each production system. It was also shown that DM is positively related (p < 0.05) to WSP content. This will be important for future legislative compliance based on the WSP content of litter/manure.

Interactive effects of soil moisture, air temperature and litter nutrient diversity on soil microbial communities and Folsomia candida population

Soil organisms play a key role in carbon and nutrient cycling in forest ecosystems. While soil organisms are strongly influenced by litter chemistry and are highly sensitive to abiotic conditions, little is known about the interactive effects of these two factors. To address this gap in knowledge, we conducted a 10 week microcosm experiment in which we simulated the effects of climate change on soil ecology. More specifically, we studied relationships among litter nutrient concentration, microbial biomass, Collembola demographic parameters, and litter decomposition, exploring the potential impacts of increasing air temperature and decreasing soil moisture. To develop a gradient of nutrient concentrations, we created six tree litter mixtures with materials gathered from Quercus pubescens and its companion species. In contrast to microbes, we observed that Collembola abundance and litter decomposition were interactively affected by soil moisture and air temperature: the negative effect of increasing air temperature on Collembola abundance was amplified by reduced soil moisture, whereas the positive effect of increasing air temperature on litter decomposition disappeared under reduced soil moisture conditions. In contrast to fungi, the response of bacterial biomass and Collembola abundance to litter nutrient concentration was dependent on abiotic conditions. More specifically, the relationships between nutrients, especially calcium and magnesium, and bacterial biomass and Collembola abundance were less robust or disappeared under drier or warmer conditions. In conclusion, our findings underscore that ongoing climate change could affect soil organisms directly as well as indirectly, by altering their responses to litter nutrient concentrations. In addition, we found that nutrient‐rich habitats might be more affected than nutrient‐poor habitats by altered climatic conditions.

Leaf litter nutrient content reveals benefits to traditional cropping systems in the Amazon

Soil fertility in the Amazon rainforest is very dependent to litter decomposition as a source of organic carbon and nutrients. Thus, land use that promote high litter decomposition might play a positive influence on soil chemical properties. The present study aimed to quantify the nutritional content of litter in anthropized and natural environments in Southern Amazonas. The study was conducted on two properties in the municipality of Canutama, in four areas: native forest, annatto, cupuassu, and guarana. In each area, 10 conical collectors (0.21 m²) were installed at a height of 0.3 m from the ground. The samples collected in each area for each month were dried in a forced circulation oven at 60ºC until reaching constant mass and weighed. Macro- and micronutrient content analyses were performed by sulfuric solubilization (N), nitric perchloric solubilization (Ca, Mg, P, K, Na, S, Cu, Fe, Mn, and Zn) and incineration (B). Variance analysis and comparison of means by Tukey test at the 5% probability level were applied to the data obtained, along with a multivariate analysis. This comparison was carried out by evaluating the overall average of a whole year of litter formation, as well as for formation within each month evaluated. Sulfur (S) was the only macronutrient that did not differ between environments (0.1 and 0.2 g kg-1). Macronutrients and micronutrient contents of litter (N: 16.92; Mg: 1.08; Cu: 16.00; Zn: 31.70; B: 104.40; g kg-1) were significantly highest in the annatto area. Annato also presents higher K (9.92 g kg-1) and P (0.70 g kg-1) contents. The litter of natural forest and guarana are richer in P (0.88 g kg-1) and Ca (g kg-1), respectively. Cupuassu litter showed lower nutritional contents, especially in macronutrients contents (N: 9.04; P: 0.51; K: 0.28; Ca: 0.76; Mg: 0.44; g kg-1). This indicates that traditional Amazonian agroecosystems may positively to improve quality of litter and impact nutrient cycling in soils highly weathered in the region.

Increased aridity and chronic anthropogenic disturbance reduce litter productivity in a Caatinga dry forest

Tropical dry forest productivity is thought to be driven by a combination of natural factors, particularly total water availability and seasonality. However, most of the world’s dry forests have been converted into forest successional mosaics by a combination of slash-and-burn agriculture and exploitation of forest products, which has potential impacts for forest productivity. Here, we examined litter production, nutrient concentrations and fluxes across regenerating and old-growth stands of a Caatinga dry forest during a 48-mo period, assessing the impact of annual rainfall, forest aboveground biomass, soil fertility, forest successional status, stand age and chronic anthropogenic disturbance. We found our sites to have low litter productivity, producing 0.193 ± 0.016 Mg ha−1 yr−1 (mean ± SE) of litter. Moreover, litter production was highly seasonal (> 90% during the dry season), and varied substantially across forest stands (from 0.0035 to 0.564 Mg ha−1 yr−1), but with no differences relative to forest successional status; i.e. similar litter production in regenerating and old-growth stands. Litter production was affected by precipitation, soil fertility and chronic anthropogenic disturbance. Litter nutrient concentration was highly variable across forest stands, but concentration responded very little to our focal drivers. Litter N-concentration was relatively high, while P was very low resulting in a small flux to the soil via litter decomposition. In contrast to litter nutrient concentrations, nutrient fluxes were more predictable, particularly considering forest successional status. Our results suggest that Caatinga dry forest on sandy soils is a low-productivity ecosystem, probably due to a combination of natural and anthropogenic drivers.

Chronic anthropogenic disturbance alters litter decomposition and nutrient concentrations and stocks across a Caatinga dry forest chronosequence

Litter decomposition plays a key role in the cycling and storage of nutrients in terrestrial ecosystems. However, very little is known about decomposition processes and their underlying drivers in tropical dry forests, particularly in human-modified landscapes. Here, we evaluate decomposition rates and nutrient concentrations and stocks in the litter of a Caatinga dry forest chronosequence, in northeast Brazil. Litter decomposition was monitored for a year across forest stands of varying ages and old-growth forests. The litter decomposition rate was highly variable across forest stands, although on average decomposition occurred slowly, with approximately 50% of the initial litter mass still present after one year. The decomposition rate is responsive to forest type and negatively affected by chronic disturbance. Litter nutrient concentration decreased along the decomposition process, exhibiting a nutrient-specific mineralization rate. Response to drivers was also nutrient specific, with precipitation and chronic disturbances playing prominent roles. Nutrient stocks in the remaining litter were higher in old-growth forests, and final stocks of certain nutrients also responded to multiple drivers. Our results suggest that the Caatinga dry forest experiences a slow rate of litter decomposition and mineralization, although rates exhibit considerable variability across forest stands and environmental conditions. Thus, chronic disturbance plays a role by either facilitating or reducing litter decomposition, mineralization rate, and the stocks transferred to the soil. Consequently, these factors have implications for nutrient availability, including goat consumption and subsequent loss of nutrients.

Exogenous enzyme addition affects litter decomposition by altering the microbial community and litter nutrient content in planted forest

Abstract Litter inputs have great impacts on the soil properties and ecosystem functioning in forests. Rapid litter decomposition leads to decreases in planted forest agricultural waste and enhances the nutrient cycle in forests. The breakdown of litter and the release of various components depend heavily on enzymes. However, the effects of exogenous enzyme preparations on litter decomposition have been hardly investigated. In this study, we examined how these enzymes affected the remaining rate of litter quality, nutrient content (C, N, K), and microbial community diversity. Taking Eriobotrya japonica litter as the research object, five exogenous enzymes (laccase, lignin peroxidase, leucine arylamidase, cellulase, and acid phosphatase) were applied to litter leaves. The mass remaining rate and main nutrient content of the litter were measured during the decomposition period. The microbial diversity attached to the surface of the litter was determined after decomposition at constant temperature and humidity for 189 days. Application of laccase and lignin peroxidase increased litter degradation by affecting microbial diversity, N and K contents. Addition of leucine arylamidase leaded to an increase in N content, and decreased the quality of the litter. The cellulose and lignin decomposition rate in litters was unaffected by the addition of cellulase, laccase, and lignin peroxidase. These results indicate that exogenous addition of enzymes may alter the nutrient content and microbial community, thus affecting litter decomposition. It is imperative to investigate the effects and mechanisms of exogenous enzymes on litter decomposition for regulating decomposition of agricultural waste litter.

Microbial race to colonise leaf litter in a littoral‐lake environment and its relation to nutrient dynamics

Abstract Litter colonisation by fungi and bacteria is essential for decomposition. Although algae are not directly related to the decomposition process, in lentic environment, they usually colonise leaf litter rapidly and stimulate the activity of heterotrophs. We hypothesised that the timing of litter entering the water determines a rapid colonisation by algae, which affects fungal and bacterial colonisation, nutrient dynamics of leaf litter, and decomposition rates. We incubated two leaf litter species, Nothofagus antarctica and Potentilla anserina, in the littoral zone of a lake under two conditions: submerged from the beginning (aquatic: AQ) and near the shoreline (initially terrestrial: T‐A). The T‐A treatment was flooded on day 44, so the decomposition process continued in aquatic conditions. We estimated two decomposition rates, one before day 42 (k42) and one for the whole incubation period (ka), algal and fungal biomass, bacterial abundance, and nutrient (P and N) content in leaf litter throughout the experiment. The timing of litter entering the water affected decomposition rates, k42 and ka were faster in AQ than in T‐A conditions and only the ka was faster in P. anserina than in N. antarctica. Microbial colonisation was also affected. Algal biomass was always higher in the AQ treatment, but bacterial abundance differed between treatments and changed through the decomposition process. Fungal biomass depended on both the treatment and the litter species. Bacterial–algal and fungal–algal relationships in AQ treatment were synergistic and independent of time, while, with terrestrial exposure, microbial relationships depended on the stage of the decomposition process. Nutrient dynamics depended on the treatment and the species, but both species tended to gain or maintain nutrient content throughout the experiment. Fungi were related to N:P changes through the decomposition process. Our results suggest that the conspicuous growth of an autotrophic biofilm on some litter (in P. anserina) might retard decomposition but at the same time stimulate heterotrophic colonisation. Therefore, the study of decomposition in the littoral zone of lakes must include the autotrophic component of biofilms that grow on detritus, since it alters organic matter consumption by decomposers and nutrient dynamics.

Variations in soil nutrient availabilities and foliar nutrient concentrations of trees between temperate monsoon karst and non‐karst forest ecosystems on Mount Ibuki in Japan

AbstractPlants growing on karst soils, which are characterized by high pH (>7.5–8.0) and low phosphorus availability, often exhibit phosphorus deficiency. However, little is known about the soil nutrient availabilities and foliar nutrient concentrations of trees in karst ecosystems with lower soil pH (<7.0). In this study, we analyzed soil properties and nutrient concentrations of leaf litter from two secondary forests in the Asian monsoon temperate region of Japan, one on karst (limestone) soil and the other on non‐karst (sandstone) soil. We also compared the live leaf nutrient concentrations of four dominant tree species (Carpinus tschonoskii, Cornus macrophylla, Neolitsea sericea, and Quercus variabilis) found in both sites. The karst soil had a higher pH (6.5) than the non‐karst soil (5.6), as well as higher phosphorus concentrations and calcium availability, but lower potassium availability. The phosphorus concentrations measured using Truog ([NH4]2SO4) and Olsen (NaHCO3) extraction methods were both higher in the karst soil. The availabilities of ammonium and nitrate in the soil did not differ significantly between the sites. The concentrations of calcium, potassium, and phosphorus in the live leaves and leaf litter reflected their availability in the soil, and the litter nitrogen concentration was higher in the karst forest. Overall, this karst soil with a relatively low pH (6.5) was rich in phosphorus but poor in potassium. Karst soil may provide a large quantity of phosphorus for trees at low pH. Future research should investigate the change in phosphorus availability of karst soils at different degrees of weathering.

Nutrient stoichiometric and resorption characteristics of the petals of four common urban greening Rosaceae tree species.

Nutrient resorption efficiency and stoichiometric ratios are important strategies for understanding plants. The present study examined whether or not the nutrient resorption process of plant petals is similar to that of leaves and other vegetative organs, as well as the nutrient restriction status of the whole flowering process of plants in urban ecosystems. Four Rosaceae tree species, Prunus yedoensis Matsum, Prunus serrulata var. lannesiana, Malus micromalus Makino, and Prunus cerasifera 'Atropurpurea', were selected as urban greening species to analyze the contents of C, N, P, and K elements in the petals and their stoichiometric ratios and nutrient resorption efficiencies. The results show interspecific differences in nutrient contents, stoichiometric ratios, and nutrient resorption efficiency of the fresh petals and petal litter of the four Rosaceae species. The nutrient resorption process was similar to that of the leaves before the petals fell. The nutrient contents of petals were higher than that of leaves at the global level, but the stoichiometric ratio and nutrient resorption efficiency of petals were lower. According to the "relative resorption hypothesis", N was limiting during the entire flowering period. The nutrient resorption efficiency of petals was positively correlated with nutrient variation. The correlation between the nutrient resorption efficiency of petals with nutrient content and stoichiometric ratio of petal litter was stronger. The experimental results provide scientific basis and theoretical support for the selection, scientific maintenance and fertilization management of Rosaceae tree species in urban greening.

Litterfall production, decomposition and litter nutrient contents in a mined area revegetated with different forest species

Afforestation of sites disturbed after bauxite mining is the favorite technique to restore all ecosystem functions. The nature of the tree species used for revegetation of post-mining land can accelerate the recovery of soil organic matter and nutrient cycles. This study aimed to determine the litterfall production, decomposition rate and nutrient content from three types of forest cover ( Eucalyptus , Anadenanthera peregrina , mixed plantation of 16 native species) planted in a bauxite mining area in recovery. Litterfall [...]

Litter Deposition and Nutrient Cycling of Invaded Environments by Cryptostegia madagascariensis at Tropical Cambisols from Northeastern Brazil

Cryptostegia madagascariensis is an invasive plant species that covers 11% of the Brazilian northeastern territory, but its role on the litter trait in tropical ecosystems remains unclear. Here, we analyzed and compared the litter deposition, litter nutrient content, soil organic matter, and the litter decay rate from invaded and non-invaded environments by C. madagascariensis at a tropical Cambisol. The PCA analysis revealed that litter deposition, litter quality, and soil organic matter were correlated with the invaded environment. We grew plant species in greenhouse conditions to obtain a standard litter material to use in our litter bags in field conditions. We found that litter decay rate was higher in the invaded environment than in the non-invaded one. Our results suggest that C. madagascariensis changes litter traits in tropical ecosystems that in turn create negative plant–soil feedback to the native species by creating a physical barrier on soil surface and to promote its own rhizosphere.

Nutrient controls on carbohydrate and lignin decomposition in beech litter

Nutrient pollution has increased plant litter nutrient concentrations in many ecosystems, which may profoundly impact litter decomposition and change the chemical composition of litter inputs to soils. Here, we report on a mesocosm experiment to study how variations in the nitrogen (N) and phosphorus (P) concentrations in Fagus sylvatica (European beech) litter from four sites differing in bedrock, atmospheric deposition, and climate affect lignin and carbohydrate loss rates and residual litter chemistry. We show with pyrolysis GC/MS and elemental analysis that nutrient concentrations had a strong influence on changes in litter chemistry during early decomposition (0–181 days), when greater lignin loss rates were associated with low P concentrations, whereas carbohydrate and bulk C loss were associated with high N concentrations. Nutrient concentrations, in contrast, did not influence changes in litter chemistry in the later decomposition stage (181–475 days), where the decomposition rates of lignin, carbohydrates, and bulk C all increased with litter N concentration and no differences in decomposition rates between major compound classes were detected. Our data indicate that these differences were related to the transition from increasing to constant or declining microbial biomass, and an associated decrease in microbial dependence on the mobilization of nutrients from the insoluble litter fraction.

Dynamic Change Characteristics of Litter and Nutrient Return in Subtropical Evergreen Broad-Leaved Forest in Different Extreme Weather Disturbance Years in Ailao Mountain, Yunnan Province

By studying the dynamic change characteristics of litter production, composition, nutrient content, and return amount of different components in different extreme weather interference years of Ailao Mountain evergreen broad-leaved forest, the paper provides theoretical support for the post-disaster nutrient cycle, ecological recovery, and sustainable development of the subtropical mid-mountain humid evergreen broad-leaved forest. Square litter collectors were randomly set up to collect litter. After drying to a constant mass, we calculated the seasonal and annual litter volume and the contents of organic carbon (C), total nitrogen (N), total phosphorus (P), total potassium (k), total sulfur (S), total calcium (Ca), and total magnesium (Mg). Finally, the nutrient return amount is comprehensively calculated according to the litter amount and element content. We tracked dynamic changes in litter quantity, nutrient composition, and nutrient components across different years. The results showed that the amount of litter from 2005 to 2015 was 7704–8818 kg·hm−2, and the order of magnitude was: 2005 (normal year) > 2015 (extreme snow and ice weather interference) > 2010 (extreme drought weather interference); the composition mainly included branches, leaves, fruit (flowers), and other components (bark, moss, lichen, etc.), of which the proportion of leaves was the largest, accounting for 41.70%–61.52%; The monthly changes and total amounts in different years exhibited single or double peak changes, and the monthly litter components in different years showed significant seasonality. In this study, the nutrient content of litter was higher than that of litter branches each year. The total amount of litter and the nutrient concentration of each component are C, Ca, N, K, Mg, S, and P, from large to small. The order of nutrient return in different years was the same as that of litter, and the returns of nutrients in litter leaves were greater than that of litter branches. The ratio of nutrient returns of litter and litter branches from 2005 to 2010 was 2.03, 1.23, and 3.69, respectively. The research shows that the litter decreased correspondingly under the extreme weather disturbance, and the impact of the extreme dry weather disturbance was greater than that of the extreme ice and snow weather disturbance. However, the evergreen broad-leaved forest in the study area recovers well after being disturbed. The annual litter amount and nutrient return amount is similar to that of evergreen broad-leaved forests in the same latitude and normal years in other subtropical regions. The decomposition rate and seasonal dynamics of litter nutrients are not greatly affected by extreme weather.

A Decision-Support System for Economic Feasibility of Subsurfaced Poultry Litter

Cattle (Bos spp.) producers routinely spread fertilizer or broadcast poultry (Gallus gallus L.) litter to improve forage production. With poultry litter widely available across the southeastern United States and being a cheaper source of plant nutrition than commercial fertilizer when proximal to application sites, the novel application of litter below the soil surface, while costly, allows for greater nutrient retention than broadcasting. Since quantifying costs and benefits of subsurfaced litter is complex, we develop and present a decision support spreadsheet for automated farm-scale model comparisons across modes of nutrient management. We compare subsurfaced litter to commercial fertilizer and broadcast litter in user-specific scenarios involving equipment choices (new, used, custom), desired nutrient needs for crops grown, litter nutrient concentration, and interval between litter application given the slow-release nature of litter compared to commercial fertilizer. Using Visual Basic for Applications programming available with Microsoft Excel®, we develop a decision aid that collects relevant user-specific farm parameters that allow customization of output. Performance data of the innovative subsurface application equipment as observed during field operation and published engineering equipment performance standards, combined with cost information, allow estimation of relative performance metrics. Break-even and sensitivity analyses are performed to identify key equipment modifications or subsidies needed to speed adoption of subsurfacing poultry litter to minimize odor and nutrient runoff externalities experienced with broadcast litter. Results showed that subsurfaced litter can compete with commercial fertilizer on a cost/return basis and especially so in situations where organic farming practices may be targeted. With a longer interval between litter application, enhanced annual capacity utilization of the applicator, and a good match between nutrient needs of crops fertilized and litter nutrient content, the decision aid demonstrated cost savings with subsurfaced litter over commercial fertilizer while being more or less cost-neutral in comparison to broadcast litter. The decision aid lends itself to estimating operation-specific subsidies needed to encourage adoption of subsurface application of litter with the intent to reduce nutrient runoff and odor externalities. Alternatively, the sensitivity analyses pinpointed the need to enhance the performance rate of subsurface application that may be achievable by increasing the implement’s width.

Tree species identity drives nutrient use efficiency in young mixed‐species plantations, at both high and low water availability

Abstract Previous studies have demonstrated that tree species diversity increases productivity and may enhance nutrient cycling in forests. The effect of mixing tree species on stand‐level nutrient use efficiency (NutUE) has seldom been studied, and even less so in the context of climate change. Here we present the first study examining how diversity effects on NutUE may be modified by growing season water availability (low vs. high), and importantly, during periodic drought or on water‐limited sites. We tested the interaction of water availability and tree species diversity (i.e. species richness and species identity) on NutUE in two young, experimental plantations located in south‐western France (ORPHEE), and northern Ontario, Canada (IDENT‐SSM). We calculated stand‐level NutUE as above‐ground net primary productivity (ANPP) divided by the product of litterfall mass and macronutrient concentrations, of monocultures and mixed tree communities composed of several temperate tree species, with a focus on birch and pine at both sites. We found significant species richness and water availability effects on NutUE, but they were weakly and inconsistently expressed, detected only for specific nutrients, and differed between the two sites. Species identity had much stronger effects on NutUE when examined using the birch–pine plots at both sites. At ORPHEE, nitrogen use efficiency (NUE) and phosphorus use efficiency (PUE) were significantly greater in the birch–pine mixture than in each monoculture. This was due to an increase in ANPP coupled with a decrease in litter nutrient concentrations in the two‐species plot that was driven by the dominance of pine in the mixture. In the comparatively younger, denser plots at IDENT‐SSM, birch was the dominant species that resulted in positive mixing effects on ANPP and litter nutrient concentrations and a neutral effect of mixing on NUE and PUE in the birch–pine mixture. Overall, the effects of mixing did not differ with water availability treatments, suggesting that species composition of mixtures is more important than water availability for stand‐level NutUE in these young forest communities. Read the free Plain Language Summary for this article on the Journal blog.

Accumulated litter, nutrient stock and decomposition in an Atlantic Forest fragment

Litter dynamics is one of the fundamental processes for the growth and maintenance of native forest fragments, being considered the main pathway for nutrient cycling in forests. Therefore, studies on accumulated litter and nutrient content provide information for a better understanding of nutrient dynamics. The aim of the study was to evaluate leaf litter and nutrient stock in different seasons and the instantaneous rate of decomposition in an Atlantic Forest Fragment over two years. Litter sampling was carried out in 12 permanent plots with dimensions of 20 m x 50 m. Litter dry mass and nutrient concentration were determined. The average annual accumulation of litter was 5269 kg ha-1. There was no statistically significant difference in the amount of litter between seasons. There was a statistically significant difference in the contents of N, P, K Ca and Mg between the different seasons. Nutrient stocks were 123.3, 92.8, 13.2, 11.8, 9.6, 3.0 kg ha-1 year-1 for Ca, N, Mg, S, K and P respectively. The total of nutrients in the accumulated litter was 253.7 kg ha-1 year-1. The litter renewal time was 281 days. The times required for 50% and 95% litter decomposition were 196 and 850 days. The average litter stocks, nutrients and decomposition are in line with other studies, indicating that the Atlantic Forest fragment seasonal semi-deciduous presents indicators of nutrient cycling. These results show that the ecosystem is sustainable from the point of view of cycling and nutrient release.
 Keywords: ecosystem functions, nutrient cycling, secondary succession.

Timing of leaf fall and changes in litter nutrient concentration compromise estimates of nutrient fluxes and nutrient resorption efficiency

Nutrient resorption in the canopy and return to soil with litterfall are two major nutrient processes in forested ecosystems. However, leaf-fall phenology and seasonal dynamics of canopy nutrient concentration have not been comprehensively quantified, compromising the confidence in estimates of litterfall nutrient fluxes and nutrient resorption efficiency. Here, we used high-frequency litter collections for 28 species in nine plots for a temperate deciduous broadleaved forest in northeastern China. Based on leaf-fall phenology and temporal shifts in nitrogen (N) and phosphorus (P) concentrations in leaf litter for major tree species, we quantified the errors in canopy nutrient flux and resorption efficiency for 15 species and nine plots. The day of year (DOY) of start of leaf-fall, DOY of peak leaf-fall, and the length of leaf-fall period differed dramatically among tree species. Concentrations of N and P in leaf litter usually declined during the summer and autumn seasons. Annual nutrient fluxes in total canopy litterfall at the ecosystem level were 65.70 ± 6.14 kg N ha−1 and 4.70 ± 0.80 kg P ha−1 of which leaf litterfall accounted for 78 and 76%, respectively. The N (NRE) and P (PRE) resorption efficiencies at the ecosystem level calculated based on the percentage of nutrient pool resorbed from canopy leaves were 49.8 ± 3.9 and 48.0 ± 7.1%, respectively. Calculating nutrient fluxes with species-specific nutrient concentration at the DOY of peak leaf-fall (Nupeak) underestimated N and P fluxes by an average of 11 and 14%; the corresponding errors in N and P fluxes estimated using plot-specific Nupeak were –5 and –7%. In addition, NRE and PRE for major species based on Nupeak were overestimated by an average of 9 and 12%, and those for nine plots by 11 and 17%; using plot-specific Nupeak lowered mean errors in NRE and PRE to 10 and 11%. These results indicate that estimating canopy nutrient fluxes and resorption efficiency using litterfall collected at the DOY of peak leaf-fall can lead to non-negligible errors, and species-specific combined litterfall collected at and slightly before the DOY of peak leaf-fall may be a better metric for estimating nutrient flux and resorption efficiency at both species and ecosystem scales.

Seasonal litterfall and nutrients in an Atlantic Forest fragment

Litter dynamics is one of the fundamental processes for the growth and maintenance of native forest fragments, being considered the main pathway for nutrient cycling in forests. Studies on litter production and nutrient content therefore provide insights that provide a better understanding of nutrient dynamics. This study identifies the seasonality and meteorological conditions that influence the quantity and return of nutrients through litter in an Atlantic Forest fragment. Litter sampling was carried out monthly in 12 permanent plots. Each plot contained 5 littertraps distributed systematically. The litter was classified, and the dry mass and nutrients in the leaves and branches and miscellaneous fractions was quantified. Seasonal behavior was observed, with the highest depositions in the winter season. The average annual production was 6.78 Mg ha-1, with 64.9% being composed of leaves. The mean annual nutrient intake was 135.1, 115.7, 39.7, 23.5, 17.6 and 4.6 kg ha-1 for Ca, N, K, Mg, S and P, respectively. The meteorological variable precipitation influenced the deposition pattern. The increase in nutrient-use efficiency in the second year compared to the first indicates that plants strategically may be re-translocating relative amounts of their nutrients under water stress conditions.
 Keywords: ecosystem functions, nutrient cycling, secondary succession.