Litter Production Research Articles

Soil carbon and nutrient stocks under Scots pine plantations in comparison to European beech forests: a paired-plot study across forests with different management history and precipitation regimes

BackgroundOrganic carbon stored in forest soils (SOC) represents an important element of the global C cycle. It is thought that the C storage capacity of the stable pool can be enhanced by increasing forest productivity, but empirical evidence in support of this assumption from forests differing in tree species and productivity, while stocking on similar substrate, is scarce.MethodsWe determined the stocks of SOC and macro-nutrients (nitrogen, phosphorus, calcium, potassium and magnesium) in nine paired European beech/Scots pine stands on similar Pleistocene sandy substrates across a precipitation gradient (560–820 mm∙yr− 1) in northern Germany and explored the influence of tree species, forest history, climate, and soil pH on SOC and nutrient pools.ResultsWhile the organic layer stored on average about 80% more C under pine than beech, the pools of SOC and total N in the total profile (organic layer plus mineral soil measured to 60 cm and extrapolated to 100 cm) were greater under pine by about 40% and 20%, respectively. This contrasts with a higher annual production of foliar litter and a much higher fine root biomass in beech stands, indicating that soil C sequestration is unrelated to the production of leaf litter and fine roots in these stands on Pleistocene sandy soils. The pools of available P and basic cations tended to be higher under beech. Neither precipitation nor temperature influenced the SOC pool, whereas tree species was a key driver. An extended data set (which included additional pine stands established more recently on former agricultural soil) revealed that, besides tree species identity, forest continuity is an important factor determining the SOC and nutrient pools of these stands.ConclusionWe conclude that tree species identity can exert a considerable influence on the stocks of SOC and macronutrients, which may be unrelated to productivity but closely linked to species-specific forest management histories, thus masking weaker climate and soil chemistry effects on pool sizes.

Relationships between litter size, sex ratio and within-litter birth weight variation in a sow herd and consequences on weaning performance.

Routine selection for litter size has resulted in an increase in the proportion of lightweight piglets. There is a need to balance prolificacy with litter uniformity to maximize profit. A total of 3,465 piglets from 310 litter records obtained from 2016 until 2019 at the Pig Industry Board research unit, Arcturus, Zimbabwe were used to determine the relationships between litter size, sex ratio, and within-litter birth weight variation in the sow herd and consequences on performance at weaning. The regression procedure of SAS was used to determine the relationships between litter size, sex ratio, and within-litter birth weight variation. The regression procedure was also used to determine the relationships between number born alive, within-litter birth weight variation, and sex ratio, and litter performance traits at weaning. Parity of sow, year, and month of farrowing did not affect sex ratio (P > 0.05). The number born alive and number of piglets born had no relationship with sex ratio (P > 0.05). As the sex ratio increased, percent survival of piglets at weaning also increased linearly (P < 0.05). As the proportion of males in litters increased, within-litter birth weight variation and within-litter weaning weight variation increased reaching maximum as the proportion of males in litters approached 0.5 and then decreased onwards. As the proportion of males in litters approached 1, within-litter birth weight variation and within-litter weaning weight variation reached their least values. In conclusion, within-litter sex ratio does not vary with parity, year, and month of farrowing. Within-litter weight variation is highest in litters with equal number of male and female piglets and lowest in unisex litters. This implies that the production of unisex litters can help to reduce the variation in the weight of pigs at birth, weaning, and marketing which is one of the biggest economic challenges faced by pork producers.

Assessment of Leaf Litter Production in Tropical Trees

Litter is the layer of detached dead plant material present on the surface of the soil. It plays an imperative part in the nutrient budgeting in agroforestry system. The quantum of litter produced varies with species and also seasons. Generally the litter production will be more during summer and less during monsoon times. Further the nature of the tree species like evergreen and deciduous will also influence litter production. In the present study, 10 tree species commonly found in farm lands were identified and selected from the experimental plot, which was located in Southern agro-climatic zone of Tamil Nadu and the soil type is alfisol with a pH of 6.0. The age of the trees was 10 years. The litter collection was done throughout the year on monthly basis and quantities produced were recorded. The data recorded were subjected to statistical analysis. The results revealed the following. Acacia auriculiformis produced a maximum leaf litter of 10.0 t/ha/year followed by Senna siamea. Summer season had more litter (3.55 kg/tree) followed by winter (1.54 kg/ha). A maximum mean monthly litter of 2.54 kg/tree was recorded in Tamarindus indica followed by Acacia mangium (0.76 kg/tree). Senna siamea and Gliricidia produced leaf litter throughout the year. Tamarind produced a maximum annual litter of 30.42 kg/tree followed by Acacia mangium (9.07 kg/tree).

Litter production and nutrient deposition from native woody species in the Brazilian semi-arid region

Litter production and nutrient deposition from native woody species in the Brazilian semi-arid region

Interaction of macroinvertebrates in leaf litter in forest ecosystems: a review

The leaf litter consists of vegetable fragments/waste (e.g., leaves, fruits, twigs) and animals. Acting on soil fertilization through its decomposition and fragmentation by abiotic factors (for example, bacteria, fungi, invertebrates, and vertebrates), helping in the process of nutrient cycling, becoming an alternative in the recovery of degraded areas. Its production varies according to the climatic conditions of the region, being the observation as greater leaf litter production in tropical and subtropical areas, as well as the semi-arid regions, where the plants in greater depth lose their leaves allowing a higher deposition of the biomass in the soil. The leaf litter still acts, as it applies to a diversity of animals that they use as a means to develop. Among the most representative animals are the Annelida (Oligochaeta), Myriapoda (Chilopoda and Diplopoda), Hexapoda (Diptera, Hemiptera, Orthoptera, Coleoptera, Blattodea, Isoptera, Hymenoptera, Lepidoptera, Isopoda, Thysanura), Cheliceriformes Araneae, Scorpiones, Pseudoscorpiones and Opiliones), Mollusca (Gastropoda). All these factors make the leaf litter, a source of nutrients rich in organic compounds that help improve soil fertility and provides the animals that live in it a universe of ecological niches that suit the needs of each species.

Physicochemical characteristic, nutrient, and fish production in different types of mangrove forest in North Sumatra and Aceh Provinces of Indonesia

Mangrove forests are highly productive ecosystems that sustain marine life, including fish communities. This study aimed to analyse mangrove characteristics, physicochemical parameters, nutrient and primary production derived from mangrove litter and estimate the fish production. The study was conducted at five mangrove sites in North Sumatra and the Aceh Provinces, Indonesia. Two sites represented natural forest at North Sumatra and Aceh (Jaring Halus and Langsa). In comparison, two sites were mangroves converted into oil palm plantations (Pulau Sembilan and Pulau Kampai, North Sumatra). The fifth site was a mangrove forest converted into aquacultural ponds (Percut Sei Tuan, North Sumatra). The study displays the dissemination of mangrove species in five different mangrove sites showing diversity. Avicennia spp found in estuarine near a coastal area, Rhizophora spp spread across the sites, and Sonneratia spp were more likely to occur in the mouth of the upstream river. Litter production at the present study site was dominated by Rhizophora spp., followed by Avicennia spp. This finding was very closely related to the nutrients resulting from litter decomposition in the mangrove ecosystem. The primary production value of 870-1,747 g C m-2 year had a significant role as the beginning of the estuary food chain. Our results show a close association between fish productivity and mangrove management, and conservation status. The highest fish production was found in the well-preserved forests (Jaring Halus and Langsa), followed by the sites converted to palm oil plantations (Pulau Sembilan and Pulau Kampai). At the same time, the least fishing productivity was identified at the fishing ponds (Percut Sei Tuan). The present study provides further evidence of the significant role of mangrove ecosystems for fisheries and calls for effective restoration programs to support local food security along the coast of Indonesia.

Which Agroforestry Practice Is Beneficial? A Comparative Assessment of the Traditional and the Improved Agroforestry Techniques in the Midhills of Nepal

Farmers are predominantly adopting two forms of agroforestry, traditional and improved practices, in the midhills of Nepal, but their efficacy on a comparative basis is poorly assessed, so farmers often confuse whether to continue the traditional practice or embrace the improved practice. We carried out a study in six villages of three districts, interviewed 210 farmers adopting each practice, organized six focus group discussions, and interacted with 24 key informants to compare agroforestry practices from income generation and forest conservation perspectives. An individual household adopting the improved practice annually generated 841.60 US$, which was more than two folds of the traditional practitioner. Similarly, the improved practitioner annually fulfilled 84% demand for forest products from the adopted agroforestry practice, whereas the traditional practitioner only fulfilled about 50%. The fodder, fuelwood, and timber productions were found to be significantly higher in the improved practice, whereas leaf litter production was found to be almost similar. The improved practitioners seemed to be self-sustained in forest products, where the traditional practitioners only satisfied half of their requirements from the agroforestry practice. The study concludes that the improved agroforestry practice is more beneficial compared to the traditional practice. Therefore, we suggest the traditional practitioners to modify their ongoing practice to enhance the contribution of agroforestry practice at the local level.

Leaf-litter production in human-modified Amazonian forests following the El Niño-mediated drought and fires of 2015–2016

Leaf-litter production is an essential part of the carbon cycle of tropical forests. In the Amazon, it is influenced by climate, presenting high levels during the driest months of the year. However, it is less established how extreme climatic events may impact leaf-litter production in the long term. Even more unclear is how litter production is affected by human-driven disturbances. Here we examine the effects of the 2015–16 El Niño drought and subsequent fires in the leaf-litter production of human-modified Amazonian forests, thus investigating the interactions of a climatic extreme with anthropogenic disturbances on this key process of the Amazonian carbon cycle. We sampled leaf litter from April 2015 until March 2019 across 20 plots located in the eastern Brazilian Amazon, in a total of 11,548 samples. Plots were distributed along a pre-El Niño gradient of human disturbance, including undisturbed, logged, logged-and-burned, and secondary forests. All plots were impacted by the extreme drought caused by the 2015–16 El Niño, and eight were also impacted by understory fires. We found a significant and non-linear relationship between precipitation and monthly leaf-litter production – above 300 mm of monthly precipitation, the production of leaf-litter becomes independent of rainfall. Surprisingly, this relationship was not influenced by pre-El Niño forest disturbance class. During the El Niño, leaf-litter production was higher, decreasing sharply in the following year, especially in El Niño-fire-affected forests. Between 2017 and 2019, all forests experienced a gradual increase in the production of leaf litter. However, the mechanisms behind this increase remain unclear and are likely different between forests affected only by the El Niño drought and those affected by both the drought and fires. Our results suggest that while leaf-litter production may be insensitive to past human disturbances, it is affected, in the short term, by extreme climatic events, especially in forests impacted by El Niño fires.

Root, not aboveground litter, controls soil carbon storage under grazing exclusion across grasslands worldwide

AbstractGrazing exclusion is a common management strategy for improving grasslands degraded due to overgrazing. Although previous meta‐analyses proved that grazing exclusion improved soil carbon (C) storage of grasslands in China, we know little about its effect on grassland ecosystems elsewhere and whether litter accumulation induced by grazing exclusion regulates soil C storage. Using meta‐analysis, we integrated 91 publications to examine the effects of grazing exclusion on community litter and soil C storage, accompanied by analysis of the regulating roles of body size of herbivore, climatic conditions, and grazing exclusion duration. We found that grazing exclusion enhanced litter biomass and decomposition rate but did not change litter chemical quality. Generally, grazing exclusion enhanced plant production and soil C storage across grassland worldwide. Exclusion of medium and small herbivores had stronger effects on aboveground litter production and soil C storage than exclusion of large herbivores, and grazing exclusion's enhancement on litter production and soil C storage tended to increase as grazing exclusion proceeded. Notably, grazing exclusion‐induced increase in aboveground litter biomass was attributed to the increase in biomass of graminoids, while root biomass, not aboveground litter biomass, primarily regulated the increase in soil C storage. The stimulating effect of grazing exclusion on soil C storage was enhanced possibly due to enhanced root biomass response along a precipitation gradient. Generally, our study provided new insights that management practice under grazing exclusion should take plant community dynamics, grazing exclusion duration, preceding grazer type, and climate conditions into account simultaneously.

Decline in nutrient inputs from litterfall following forest plantation in subtropical China

The rapid conversion of natural broadleaved forests to plantations (mainly Cunninghamia lanceolata and Pinus massoniana) in subtropical China has resulted in a substantial decline in soil fertility, but the biogeochemical mechanism behind this decline remains not fully understood. Litterfall is an important source of nutrients that are returned to soils through litter deposition and decomposition. We assessed various types of litterfall (leaves, twigs, flowers, fruits and unidentified litter) monthly and their carbon (C), nitrogen (N), phosphorus (P) and potassium (K) inputs to soils in a natural broadleaved forest (Castanopsis carlesii) and in P. massoniana and C. lanceolata plantations over 10 years. The total litterfall was 21–25% lower in plantations than in the C. carlesii forest, resulting in much lower C (−17% and −14%), N (−62% and −52%), P (−24% and −32%) and K (−53% and −40%) inputs from litterfall in the P. massoniana and C. lanceolata plantations. Leaves accounted for 72–76% of the total litterfall, so we compiled available data on the nutrient release from the three foliar litters during the 1st year of decomposition throughout subtropical China. The decomposition rates of P. massoniana and C. lanceolata needle litter were only half that of C. carlesii leaf litter, and the lower initial quality of P. massoniana and C. lanceolata needle litter relative to C. carlesii leaf litter resulted in significantly lower amounts of N (−95% and −76%) and P (−48% and −25%) being released. These results suggest that low nutrient (N, P and K) inputs due to low litter production and slow nutrient release due to slow litter decomposition are two important biogeochemical reasons for the decline in soil fertility in plantations in subtropical China.

Litterfall guided soil nutrient return in Eucalyptus based agroforestry system

Here, the arrangement of litterfall and nutrient return to the soil by the seven-year-old plantations of Eucalyptus under different spacings established on sodic wastelands in northern India was determined. The litterfall was sorted into leaf wood and miscellaneous. Further, the seasonal variation of litterfall obtained under three different spacings was recorded. Maximum leaf litter production was observed in 3×3 m spacing followed by 6×1.5 m during the winter season. Whereas, the minimum leaf litter was recorded in 17×1×1 m spacing. Similarly, the maximum wood litter production was observed at the spacing of 3×3 m spacing in rainy season followed by 6×1.5 m.The weights of nutrients returned through annual litterfall in 3×3 spacing returned the highest amount of N (2.16 g/m2 year) followed by 6×1.5 and 17×1×1 spacing.. Whereas, two-year data of litterfall of E. tereticornis showed the 17×1×1 spacing returned the highest amount of P in next year through leaf litter followed by 6×1.5 and minimum 3×3 spacing. Overall, this study provides important information regarding the litterfall guided soil nutrient return to the soil under North Indian conditions.

Quantification of biomass and litter in agroforestry system with sour orange cultivation in the Brazilian Amazon

The knowledge of the quantity and composition of the deposited biomass is useful to plan the nutrient management of cultivations in agroforestry systems. The objective of this work was to evaluate the production of biomass and litter in two agroforestry systems with organic and conventional cultivations of sour orange. The areas use models of orange production by monoculture and under agroforestry systems: the first agroforestry system is composed of rows of brazilian mahogany (Swietenia macrophylla K.) accompanied by double rows of orange trees (Citrus aurantium L.); the second system is composed of rows of ingá (Ingá edulis Mart.) accompanied by double rows of orange trees. A completely randomized design was used in a 10x2 factorial scheme, with 4 replications. The locations within the management systems were organized as follows: agroforestry system composed of mahogany trees; Ingá trees agroforestry system; conventional sour orange monoculture system. The areas that the biomass and litter were collected in the locations in the systems were: between plants in the row for cultivation of forest species that make up the system; between rows of the forest species row and orange cultivation row; between plants in the orange cultivation row; between rows of the double row of orange cultivation. Two periods were analyzed in the experiment: the months of lowest and highest rainfall. Agroforestry systems promoted greater biomass and litter to the soil compared to monoculture. In this way, they were configured as a beneficial practice for the soil in sour orange crops in the Brazilian Amazon.

79 Direct and Indirect Effects of Heat Stress on the Hepatic and Ovarian Proteome in Gilts

Abstract Seasonal infertility (SI) caused by heat stress (HS) impacts the US swine industry by reducing litter size, farrowing rates, and production efficiency. Identifying the biological underpinnings of SI is a foundational step towards developing mitigation strategies to reduce the nearly $1 billion annual revenue losses to the swine industry. The study objective was to investigate the direct and indirect effects of HS via HS conditioned serum infusion in swine. We hypothesized gilts housed in thermoneutral (TN) conditions receiving gradual infusions of serum obtained from HS gilts would experience altered endocrine and metabolic function compared to gilts receiving serum from TN gilts. Prepubertal gilts (n = 18) were assigned to donor or recipient groups and donors were allocated to TN or HS environments. Blood was collected from HS donors and TN donors exposed to 24-hours of HS or TN conditions, respectively. Serum was infused into recipients housed in TN conditions via indwelling jugular catheters. Over a 24-hour period approximately 20% of the estimated recipient gilt serum volume from donors (pooled by treatment) was infused into recipients. After infusions were completed, gilts were euthanized and tissues collected. Increased rectal temperatures were observed in HS recipients compared to TN recipients (P ≤ 0.05). Protein extracts from liver and ovary underwent proteomic analysis via liquid-chromatography with tandem mass-spectrometry (LC-MS/MS) to assess protein abundance. In the liver and ovary, we identified 135 and 264 proteins, respectively, that were differentially abundant between TN and HS recipients (P &amp;lt; 0.10). Gene Ontology enrichment analysis identified alterations to pathways involved in hormone regulation, immune response, and apoptosis. Collectively, these data demonstrate gilts receiving HS serum experienced altered endocrine and metabolic function compared to gilts receiving TN serum. This project was supported in part by the Iowa Pork Producers Association. USDA is an equal opportunity provider and employer.

Control of felinine-derived malodor in cat litter.

Malodors stemming from soiled cat litter are a major frustration for cat owners, despite the widespread use of absorbent litters with claims of odor control. Technologies for effective litter odor control have not been rigorously evaluated. Here, we report on the effectiveness of a novel litter formulation of 1-monochlorodimethylhydantoin (MCDMH)-modified clinoptilolite zeolite (MCDMH-Z) to control the odors of 3-mercapto-3-methylbutanol (3M3MB) and ammonia, the principal products generated by the enzymatic breakdown of felinine and urea, respectively. The efficacy of MCDMH-Z for the odor control of 3M3MB was determined by solid-phase microextraction and gas chromatography mass spectrometry analysis, colorimetric analysis and a sensory panel. Enzyme inhibition was monitored by a colorimetric coupled assay for ammonia. The antimicrobial properties were measured by a reduction in colony-forming units (CFUs). 3M3MB proved highly susceptible to modification by MCDMH-Z granules. Headspace above litter exposed to MCDMH-Z showed no detectable 3M3MB; levels >59 ng were detected in commercially available products. Urease activity decreased by >97% after incubation with MCDMH-Z to 0.14 mg/ml. Cat litter F showed comparable inhibition (0.13 mg/ml); others showed less inhibition, producing up to 4.8 mg/ml of ammonia. MCDMH-Z reduced the CFUs of Proteus vulgaris by six log reduction values in 30 mins; in the same amount of time, no reduction was seen with commercial products tested. The odor control capability of the MCDMH-Z granules was further supported by a sensory panel scoring 3M3MB-spiked litters. Samples of commercially available litter products showed an effect on malodor, or inhibition of urease, or contained antimicrobial activity; no samples were capable of accomplishing these concurrently. In contrast, MCDMH-Z granules were effective in all three test categories. Control of felinine-derived odors, in particular, has the potential to improve cat owner satisfaction, and may beneficially affect cat behaviors provoked by pheromonally active sulfurous metabolites deposited in the litter.

Carbon Storage of Single Tree and Mixed Tree Dominant Species Stands in a Reserve Forest—Case Study of the Eastern Sub-Himalayan Region of India

In recent decades, carbon (C) management is an important point on the agenda to identify the best viable mitigation strategies for its reduction. The study was conducted at Jaldapara National Park located in the Eastern Himalayan region of India. The study quantified litter production, decomposition, periodic nutrient release, soil fertility status, and soil organic carbon (SOC) of five major forest stands i.e., Tectona grandis (TGDS), Shorea robusta (SRDS), Michelia champaca (MCDS), Lagerstroemia parviflora (LPDS) and miscellaneous stand (MS). A stratified random nested quadrate method was adopted for sample collection. Results reveal that the greatest amount of litter production and decomposition was under MCDS followed by MS, LPDS, SRDS, and the smallest under TGDS. The material annual turnover through litter decomposition in all the stands varies between 96.46% and 99.34%. The content and amount of the available nutrients in litter varied significantly among the stands. Moreover, release of these nutrients was nearly equal to the amount available in the initial litter mass. In general, the magnitude of the total nutrient return was in the same order as the total litter fall and the nutrient availability was more closely related to litter nutrient content and soil organic carbon. The range of pH (4.86–5.16), EC (0.34–0.50), soil moisture (27.01–31.03) and available primary nutrients (N: (0.21–0.26 Mg/ha), P: (0.09–0.12 Mg/ha), K: (0.13–0.14 Mg/ha)) also varied significantly among the stands. Significant positive correlations were observed between SOC, N and K. Both the fertility indices exhibited no definite pattern in the stands but a significant correlation between the two indicates the healthy soil fertility status of the stands. SOC varies significantly under different forest stands, but the greatest content was found under MS. The estimated SOC ranges between 75.9 and 107.7 Mg ha−1 up to 60 cm and is reported to be below the Indian average of 182.94 Mg ha−1. The present study strongly recommends that Tectona grandis, Shorea robusta, Michelia champaca, and Lagerstroemia parviflora should be the important commercial timbers of the Eastern Himalayan region because they may help further to increase the C sink in agricultural and degraded landscapes.

Stand Structure, Biomass and Carbon Storage in Gmelina arborea Plantation at Agricultural Landscape in Foothills of Eastern Himalayas

In the modern era, Gmelina arborea plantations are a hotspot of future research because of their high carbon sequestration potential. The present work was conducted during 2018 to 2020 on a young unmanaged Gmelina farm to understand the ecosystem’s carbon and its dynamics. The study area was categorized into three age classes: ≤5, 5–10, and 10–15 years. In a plantation, Gmelina trees (10%) were randomly selected while other trees (90%) were also taken into the consideration for ecosystem carbon. A stratified random nested quadrate sampling method was adopted for analyzing other vegetation forms under study. Overall, 51 individual species in the studied Gmelina farm were found which includes 23 tree species, 7 shrub species, 16 herbs, 2 climbers, and 3 species of ferns. The estimated quantitative vegetation parameters and diversity indices indicate that the plant assemblages were heterogeneous with native diverse species evenly distributed with fairly higher densities, frequencies, and abundance. Herbs were the most important species followed by shrubs and trees. Consequently, with the increasing age of plantation, the richness of plant species increased. Soil properties were significantly influenced by the age of the plantation but exhibited no discreet trend. Total biomass density and total carbon density increased with increasing plantation age while no drastic variation was found in available soil organic carbon (SOC) because of insignificant variability in litter production. Total carbon, available SOC (up to 60 cm depth) and ecosystem carbon in the three age class plantations fell in the ranges of 54.51–59.91, 48.18–55.73, and 104.81–110.77 Mg ha−1, respectively. The carbon sequestration potential of Gmelina arborea is higher compared to other reported species and highly supportive of converting unutilized agricultural landscapes to reduce the atmospheric carbon dioxide in future.

Effect of vegetation mosaic on spatial heterogeneity of soil organic carbon mineralization and nitrification in an alpine meadow

Patchy distribution of herbaceous species is common in degraded grasslands on the Qinghai-Tibetan Plateau, but the effects of such a mosaic pattern on soil biochemical properties have rarely been studied. We compared soil organic carbon (SOC) mineralization, nitrogen (N) availability, ammonia oxidation and plant N uptake between the following vegetation patch types (plant communities) in an alpine meadow: grass (dominated by Elymus nutans, Poa crymophila and Leymus secalinus), sedge (Kobresia capillifolia and Kobresia humilis), Polygonum viviparum (P. viviparum only), Artemisia smithii (A. smithii only) and Oxytropis kansuensis (O. kansuensis only). All patches had a diameter ranging from about tens of centimeters to several meters. SOC mineralization was faster in patches beneath grass or A. smithii than in those beneath sedge or O. kansuensis, but the faster SOC mineralization beneath grass and A. smithii patches did not result in a difference in SOC storage in the top 30 cm of soil compared with that in other patches. Greater litter production beneath grasses or belowground carbon input (largest root/shoot ratio) beneath A. smithii may have offset the negative effect of rapid SOC mineralization on SOC storage under grass and A. smithii patches. Productive grasses were associated with the highest level of N availability in the soil, consistent with their greater demands for N uptake. Sedge species and A. smithii inhibited nitrification by decreasing the abundance of ammonia oxidation bacteria in soil, in contrast to grasses. The inhibition of biological nitrification under A. smithii explained the finding that the soil beneath this vegetation patch type had the lowest nitrate content as a percentage of total inorganic N. However, the inhibition of nitrification beneath sedges did not induce a decrease in the nitrate content as a percentage of total inorganic N under sedge patches compared with that under grass patches. This suggests that sedges preferentially use ammonium instead of nitrate as their N source. It is concluded that patchy distribution of herbaceous species in alpine meadows created significant spatial heterogeneity in soil biological and biochemical properties at the field scale. Sampling in ecosystem studies clearly needs to take into account such heterogeneity of soil properties and processes in grasslands with patchily distributed vegetation.

Comparative Dynamics of Above-Ground Litter Production and Decomposition from Eucalyptus grandis Hill ex Maiden and Pinus taeda L., and Their Contribution to Soil Organic Carbon

The replacement of native pasture by exotic commercial forest species is an infrequent situation worldwide. In these systems, a new component is introduced, forest litter, which constitutes one of the main ways of incorporating carbon into the soil–plant system. The present work seeks to establish a methodological approach to study the dynamics of litter production and decomposition in an integrated way. The general objective was to characterize and compare the litter production dynamics in 14-year-old Eucalyptus grandis Hill ex Maiden and Pinus taeda L. commercial plantations. During two years, seasonal evaluations of fall, decomposition and accumulation of litter were carried out in stands of both species. In turn, the contribution of carbon from forest species to the soil through isotopic analysis techniques was quantified. Litterfall in E. grandis showed maximums during the spring of the first year and in the spring and summer of the second. In P. taeda, the maximums occurred in summer of the first year and in autumn of the second. In relation to the decomposition rate, the results based on short periods of evaluation between 15 and 21 months did not show differences between species, nor for the different moments of beginning of the evaluation, obtaining average values of 0.0369 month−1 for E. grandis and 0.0357 month−1 for P. taeda. In turn, both the decomposition rate of the material as a whole and the estimates of accumulated biomass in equilibrium state did not show significant differences between the species. Additionally, there was a relevant incorporation of carbon into the soil by forest species, fundamentally in the first few centimeters, substituting an important proportion of the carbon inherited by the original cover of native pastures. Finally, it is necessary to specify that the scope of the findings obtained is greatly limited by the sample size used in this study.

Beryllium cycling through deciduous trees and implications for meteoric 10Be systematics

Application of meteoric 10Be inventories and 10Be/9Be ratios to determine surface ages, erosion rates, and denudation rates requires understanding the conditions under which meteoric 10Be functions as an open vs. closed system near the Earth's surface. Here, we investigate biologically mediated beryllium isotope mobility in an oak-hickory forest in eastern North America. We report meteoric 10Be and 9Be concentrations in soils, roots, and leaves of four deciduous tree species. The data show that beryllium is readily taken-up from the soil by roots, cycled through leaves, and redeposited on the forest floor with autumn leaf abscission. Hickory (genus Carya) dominates beryllium cycling with a spatially averaged annual 10Be flux to the soil surface through litterfall that is four times higher than the atmospheric 10Be deposition rate. Biocycling may thus modulate the shape of meteoric 10Be concentration and 10Be/9Be ratio depth profiles in soils. We present a biocycling model that describes beryllium uptake by roots, redeposition on the surface through litterfall, and retention according to an exponential adsorption rule. This model reproduces the observed form of meteoric 10Be and 9Be depth profiles and the beryllium isotope ratio in foliage at the study site. The model also indicates that both declining and bulge-type meteoric 10Be depth profiles may result from biocycling, even where beryllium loss by leaching is significant, implying that declining meteoric 10Be depth profiles may not be indicative of quantitative 10Be retention. We recommend that biocycling be considered in models of beryllium isotope systematics where hickory or other beryllium accumulating taxa are present and where litter production rates are high.

First Assessment of the Benthic Meiofauna Sensitivity to Low Human-Impacted Mangroves in French Guiana

Bioindicators assess the mangroves ecological state according to the types of pressures but they differ with the ecosystem’s specificities. We investigated benthic meiofauna diversity and structure within the low human-impacted mangroves in French Guiana (South America) in response to sediment variables with various distances to the main city. Contaminant’s concentrations differed among the stations, but they remained below toxicity guidelines. Meiofauna structure (Foraminifera, Kinorhyncha, Nematoda) however varied accordingly. Nematode’s identification brought details on the sediment’s quality. The opportunistic genus Paraethmolaimus (Jensen, 1994) strongly correlated to the higher concentrations of Hg, Pb. Anoxic sediments were marked by organic enrichment in pesticides, PCB, and mangrove litter products and dominance of two tolerant genus, Terschellingia (de Man, 1888) and Spirinia (Gerlach, 1963). In each of these two stations, we found many Desmodora individuals (de Man, 1889) with the presence of epibionts highlighting the nematodes decreased fitness and defenses. Oxic sediments without contaminants were distinguished by the sensitive genera Pseudocella (Filipjev, 1927) and a higher diversity of trophic groups. Our results suggested a nematodes sensitivity to low contaminants concentrations. Further investigations at different spatio-temporal scales and levels of deterioration, would be necessary to use of this group as bioindicator of the mangroves’ ecological status.