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Harvest residues can play a crucial role in conserving nutrients for recycling in forests, but little is known about the rates of decomposition and nutrient release from these residues following logging in tropical acacia plantations. In this study, we examined the biomass and nutrient content of harvest residue components (bark, leaves, and branches) using the litterbag technique for a 1.5-year-period following harvest of a seven-year-old Acacia mangium plantation in Northern Vietnam. At harvest, the total dry biomass of harvest residues was 18 t ha&minus, 1 comprising bark (8.9 t ha&minus, 1), branches (6.6 t ha&minus, 1), and leaves (2.5 t ha&minus, 1). The retained bark on site conserved 51% N, 29% P, 32% K, 64% Ca, and 24% Mg content from harvest residues for recycling. Decomposition rate of the leaves was the most rapid (k = 1.47 year&minus, 1, t0.5 = 0.47 year), then branches (k = 0.54 year&minus, t0.5 = 1.29 year), and bark (k = 0.22 year&minus, t0.5 = 3.09 year). During decomposition, the loss of nutrients from harvest residues was K &asymp, Ca &gt, N &gt, P&gt, Mg. Decomposition of harvest residues and the associated rate of nutrient release can potentially supply a significant amount of nutrients required for stand development in the next rotation.

Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2018-11-20T18:16:09Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Flavia de Oliveira.pdf: 1587499 bytes, checksum: 2fb58a43f13e11f2b66666d67ce47b88 (MD5) Made available in DSpace on 2018-11-20T18:16:09Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Flavia de Oliveira.pdf: 1587499 bytes, checksum: 2fb58a43f13e11f2b66666d67ce47b88 (MD5) Previous issue date: 2018-08-31 Sistemas integrados de produção agropecuária (SIPA) integram em um mesmo espaço vários componentes, tais como lavoura, pastagens, animais, bem como árvores de forma sinérgica. Quando bem manejado, pode trazer a sustentabilidade para a propriedade. Um dos desafios em tais sistemas é o entendimento da dinâmica de nutrientes e o possível reaproveitamento destes pela cultura sucessora. O objetivo deste trabalho foi avaliar o aporte de liteira e dos macronutrientes, como nitrogênio (N), fósforo (P), potássio (K) e enxofre (S) em SIPA, com ausência e presença de árvores (~159 árvores ha-1), submetidos a doses de nitrogênio (90 e 180 kg N ha-1, N90 e N180, respectivamente) na fase pastagem. O experimento foi conduzido no Instituto Agronômico do Paraná, município de Ponta Grossa, Paraná. O delineamento experimental utilizado foi o de blocos ao acaso com quatro tratamentos e três repetições. De modo a melhor representar o ambiente arborizado, foi feita a subdivisão da unidade experimental em três posições entre linha das árvores. O experimento iniciou em 2006, com o plantio de árvores em arranjo de 14 x 3m. Durante o inverno cultiva-se aveia preta e azevém, pastejada por bovinos de corte, e, durante o verão, soja/milho. O presente experimento iniciou na fase pastagem de 2013, a qual antecedeu a cultura do milho (safra 2013/2014), estendendo-se até a fase pastagem no inverno de 2014. Durante a lavoura de milho e pastagem (2014), foram inseridos litter bags com os resíduos da cultura anterior, no momento das suas respectivas semeaduras. Aos 8, 15, 30, 60, 90, 120, 153 e 165 dias após a semeadura do milho e da pastagem foram coletadas as amostras dos litter bags, pesadas suas respectivas massas secas (MS) e quantificados os macronutrientes. Também foram calculadas as taxas de decomposição do resíduo e da liberação de macronutrientes. Em geral, a quantidade inicial de resíduo, tanto da pastagem como do milho, foi inferior nos tratamentos com árvores (-28%). Diferenças significativas foram observadas entre os tratamentos nos teores iniciais em N (variando de 12 no ILPF N90 até 14 g/kg no ILPF N180) do resíduo da pastagem e para os teores iniciais de K (variando entre 6,5 no ILP N90 até 12 g/kg no ILPF N90) e S (variando de 0,68 ILPF N90 até 0,91g/kg ILP N90) no resíduo do milho. As posições entre as linhas das árvores afetaram apenas os teores iniciais de N e S dos resíduos. Em relação a dinâmica de decomposição dos resíduos e liberação de macronutrientes, diferenças significativas entre os tratamentos foram observadas somente para decomposição do resíduo da pastagem e liberação de P do mesmo. A fração ativa da MS da pastagem variou entre 44 (ILPF N90) a 59 % (ILP N180). O tempo de meia vida (T1/2) variou entre 11 (ILP N90) e 54 (ILPF N180) dias para MS e entre 6 (ILP N90) e 21 (ILPF N90) dias para o P. O T1/2 do N foi de 19 dias, enquanto que para K e S foi de 13 dias. Em relação ao resíduo do milho, o T1/2 variou entre 5 (no caso de N) e 24 (no caso de P) dias. No mínimo 44% do resíduo proveniente da pastagem foi decomposto ao longo dos 165 dias de exposição à campo dos litter bags. Em relação ao resíduo do milho, 30% foi decomposto ao longo de 90 dias, independente do tratamento. Máximas liberações (37; 2,8; 62 e 2,5 kg/há de N, P, K e S, respectivamente) de nutrientes foram observadas no ILP N180 para o resíduo da pastagem, principalmente em função da maior quantidade de resíduo inicial neste tratamento. Para o resíduo do milho, máximas liberações ocorreram no ILP N90 para N (48 kg/ha), P (17,4 kg/ha) e S (4,8 kg/ha), em função da maior quantidade de resíduo inicial neste tratamento, e no ILPF N90 para K (82 kg/ha), em função do maior teor inicial em K. Portanto, tais quantidades cicladas devem ser consideradas no manejo da fertilização. Desbastes precisam ser intensificados no ILPF para reduzir o nível de sombreamento e evitar grandes reduções nas quantidades de resíduo, para otimizar os benefícios da ciclagem de nutrientes. Integrated Crop Livestock Systems (ICLS) comprehend in a same space several components, such as grain and forages crops, animals and tree component of synergistic form. When well managed, it can bring sustainability to the property. One of the challenges in such systems is the understanding of the nutrient dynamics and the possible reutilization of these by the successor culture. The objective of this study was to evaluate the contribution of litter and macronutrients, such as nitrogen (N), phosphorus (P), potassium (K) and sulfur (S) in ICLS, with absence and presence of trees ), submitted to nitrogen doses (90 and 180 kg N ha-1, N90 and N180, respectively) in the pasture phase. The experiment was carried out at the Agronomic Institute of Paraná, municipality of Ponta Grossa, Paraná. The experimental design was a randomized block design with four treatments (ILP N90, ILP N180, ILPF N90 and ILPF N180, being ILP, integration of livestock and ILPF, integration of livestock and forest) and three replications. In order to better represents the wooded environment, the experimental unit was subdivided into three positions (1m, 3.5m and 7m distance from the tree line). The experiment began in 2006 with the planting of trees in arrangement of 14 x 3m. During winter, black oats and ryegrass are grazed by beef cattle and, in the summer, soybean/corn. The present experiment started in the pasture phase of 2013, which preceded the corn crop (crop 2013/2014), extending until the pasture stage in the winter of 2014. During maize and pasture (2014), litter bags were inserted with the residues from the previous crop, at the time of their respective sowing. The samples were collected at 8, 15, 30, 60, 90, 120, 153, and 165 days after sowing of maize and pasture. The samples were performed to dry masses (DM) measure and macronutrients determination. The rates of decomposition of the residue and the release of macronutrients were also calculated. Overall, the initial amount of residue from both pasture and maize was lower in tree treatments (-28%). Differences were observed between treatments at initial N contents (ranging from 12 in ILPF N90 to 14 g / kg in ILPF N180) of the pasture residue and for the initial K contents (ranging from 6.5 in ILP N90 to 12 g / kg in ILPF N90) and S (ranging from 0.68 ILPF N90 to 0.91 g / kg ILP N90) in the corn residue. The positions between the tree lines affected only the initial N and S contents of the residues. In relation to the dynamics of the decomposition of the residues and the release of macronutrients, significant differences between the treatments were observed only for the decomposition of the pasture residue and the release of P from the same. The active fraction of DM from pasture ranged from 44 (ILPF N90) to 59% (ILP N180). The half-life time (T1/2) varied between 11 (ILP N90) and 54 (ILPF N180) days for MS and between 6 (ILP N90) and 21 (ILPF N90) days for P. O T1/2 of N was 19 days, whereas for K and S it was 13 days. In relation to maize residue, T1/2 ranged from 5 (in the case of N) to 24 (in the case of P) days. At least 44% of the pasture residue was decomposed during the 165 days of exposure to litter bags. Regarding corn residue, 30% was decomposed over 90 days, regardless of the treatment. The maximum nutrient release (37, 2.8, 62 and 2.5 kg/ha of N, P, K and S respectively) was observed in the ILP N180 for the pasture residue, mainly due to the higher amount of initial residue in this treatment. For the maize residue, maximum releases occurred in ILP N90 for N (48 kg/ha), P (17.4 kg/ha) and S (4.8 kg / ha), due to the higher amount of initial residue in this treatment, and in ILPF N90 for K (82 kg / ha), as a function of the higher starting content in K. Therefore, such cycled quantities should be considered in the management of fertilization. Slabs need to be intensified in the ILPF to reduce the level of shading and avoid large reductions in residue amounts to optimize the benefits of nutrient cycling.

We evaluated nutrient cycling by measuring leaf litter production and decomposition in the Brazilian savanna (cerrado sensu stricto) on eutrophic (calcareous) and dystrophic (arenitic) Neosols over the same spatiotemporal scale. We installed three transects in the Cerrado with plots in each Neosol type. Areas along the transects were randomly chosen for determining soil chemical properties, and accumulated leaf litter was collected monthly for a year for analysis. We used litter bags to test for a correlation between loss of dry mass and nutrient release. The calcareous cerrado had higher levels of macronutrients, higher pH, and lower Al compared to the arenitic cerrado. The estimated annual release of leaf litter nutrients in kg ha-1 yr-1 was higher in the calcareous cerrado. Nutrient concentration was significantly higher in different months in the calcareous cerrado, except for S and N. In general, the loss of dry mass was not correlated with nutrient release. Calcareous Neosol is unique to the cerrado sensu stricto, and retains more nutrients and facilitates higher leaf litter chemical quality than cerrado of the same physiognomy on dystrophic soils. Nutrient release is not always related to loss of dry mass, regardless of the amount of leaf litter.

The involvement of volunteers in the monitoring of the environment holds great potential to gather information on a wider temporal and spatial scale than is currently possible. However, the mass involvement of citizens in monitoring freshwater health is a relatively new field and subject to uncertainty. Here, we examine 1192 samples collected across 46 temperate ponds (&lt, 2 ha) and 29 temperate lakes (&gt, 2 ha) by 120 volunteers trained through the FreshWater Watch citizen science programme to consider if the approach is able to (a) identify well established patterns in water quality and biological indicators (i.e., fish), and (b) provide a potentially useful basis for the identification of pollution sources in urban or peri-urban landscapes. Seasonal patterns observed agreed well with established principles of nutrient dynamics, algal bloom seasonality, and broad biological trends between ponds and lakes. Further, observational data collected by the volunteers suggested plausible links between the presence of residential discharge and water level fluctuation and significant increases in algal bloom observations between peri-urban and urban sites. We suggest that citizen science can have a role to play in complementing regulatory monitoring efforts and that local citizens should be empowered to become stewards of their local freshwater resources.

Source at https://doi.org/10.5194/bg-15-6503-2018. Diatoms are generally the dominant contributors to the Arctic Ocean spring bloom, which is a key event in regional food webs in terms of capacity for secondary production and organic matter export. Dissolved silicic acid is an obligate nutrient for diatoms and has been declining in the European Arctic since the early 1990s. The lack of regional silicon cycling information precludes understanding the consequences of such changes for diatom productivity during the Arctic spring bloom. This study communicates the results from a cruise in the European Arctic around Svalbard, which reports the first concurrent data on biogenic silica production and export, export of diatom cells, the degree of kinetic limitation by ambient silicic acid, and diatom contribution to primary production. Regional biogenic silica production rates were significantly lower than those achievable in the Southern Ocean and silicic acid concentration limited the biogenic silica production rate in 95 % of samples. Compared to diatoms in the Atlantic subtropical gyre, regional diatoms are less adapted for silicic acid uptake at low concentration, and at some stations during the present study, silicon kinetic limitation may have been intense enough to limit diatom growth. Thus, silicic acid can play a critical role in diatom spring bloom dynamics. The diatom contribution to primary production was variable, ranging from

Plant growth regulators (PGRs) potentially improve the productivity and nutritional quality of crops through modulation of morphology, physiology and nutrient dynamics within plants. However, the effect of PGRs may differ under environments with deficient and adequate nutrients. Here the role of mepiquat chloride (MC) on the yield and seed nutritional quality of cotton was explored under boron (B) deficiency and adequate conditions in a two-year field study. Mepiquat chloride was foliar-applied at different dosages (0 and 70 mg L-1) and growth stages (squaring and flowering) and B was applied into soil (0, 1, 1.5, 2 and 2.5 kg ha-1) to establish B deficiency and adequate levels. Seed cotton yield and seed nutritional quality were substantially higher under adequate B conditions, compared to B deficiency. Nonetheless, MC applications improved the seed cotton yield, seed oil yield, seed protein yield and concentration of seed mineral nutrients (N, P, K, B, Zn and Fe except for Mn) under both B deficiency and adequate conditions. Nonetheless, the improvement in all traits caused by MC application was greater under adequate B conditions (2-2.5 kg ha-1 B), compared to B deficiency conditions. Furthermore, the application of MC at squaring proved more beneficial in improving the seed cotton yield and nutritional quality, compared to the flowering stage. In conclusion, MC application improves seed cotton yield and cotton seed nutritional quality under both deficient and adequate B conditions, through an improved nutrient accumulation in seed tissues; however, the efficacy of MC is affected by B deficiency. RESUMO: Os reguladores de crescimento vegetal (RCV) melhoram potencialmente a produtividade e a qualidade nutricional das culturas através da modulação da morfologia, fisiologia e dinâmica dos nutrientes nas plantas. No entanto, o efeito dos RCV pode diferir sob ambientes com deficiência ou conteúdos adequados de nutrientes. O papel do cloreto de mepiquat (CM) na produtividade e na qualidade nutricional da semente de algodão foi explorado sob deficiência ou condições adequadas de boro em um estudo de campo de dois anos. O cloreto de mepiquat foi aplicado nas folhas em diferentes doses (0 e 70 mg L-1) e estádios de crescimento (formação de botões florais e abertura das flores), e o B foi aplicado no solo (0, 1, 1,5, 2 e 2,5 kg ha-1) para estabelecer deficiência e níveis adequados desse nutriente. O rendimento do algodão e a qualidade nutricional das sementes foram substancialmente maiores em condições de B adequadas, comparadas à deficiência de B. No entanto, as aplicações de CM melhoraram o rendimento do algodão, o rendimento de óleo de sementes, o rendimento de proteína de sementes e a concentração de nutrientes minerais de sementes (N, P, K, B, Zn e Fe, exceto Mn) sob deficiência e condições adequadas de B. Entretanto, a melhoria em todas as características causada pela aplicação de CM foi maior em condições de B adequadas (2-2,5 kg ha-1 de B), quando comparadas às condições de deficiência. Além disso, a aplicação de CM durante a formação dos botões mostrou-se mais benéfica na melhoria do rendimento do algodão e da qualidade nutricional, em comparação com o estádio de abertura das flores. Em conclusão, a aplicação de CM melhora o rendimento do algodão e a qualidade nutricional das suas sementes em condições de deficiência e condições adequadas de B, por meio de melhor acumulação de nutrientes nos tecidos das sementes; contudo, a eficácia do CM é afetada pela deficiência de B.

The main aim of this study was to evaluate the impact of the alien invasive bivalve Corbicula fluminea (Müller, 1774) in the nutrient dynamics of temperate estuarine systems (oligohaline areas) under climate change scenarios. The scenarios simulated shifts in climatic conditions, following salinity (0 or 5) and temperature (24 or 30 °C) changes, usual during drought and heat wave events. The effect of the individual size/age (different size classes with fixed biomass) and density (various densities of

Background and aims Differences among plant genotypes can influence ecosystem functioning such as the rate of litter decomposition. Little is known, however, of the strength of genotypic links between litter quality, microbial abundance and litter decomposition within plant populations, or the likelihood that these processes are driven by natural selection. Methods We used 19 Betula pendula genotypes randomly selected from a local population in south-eastern Finland to establish a long-term, 35-month litter decomposition trial on forest ground. We analysed the effect of litter quality (N, phenolics and triterpenoids) of senescent leaves and decomposed litter on microbial abundance and litter mass loss. Results We found that while litter quality and mass loss both had significant genotypic variation, the genotypic variation among silver birch trees in the quantity of bacterial and fungal DNA was marginal. In addition, although the quantity of bacterial DNA at individual tree level was negatively associated with most secondary metabolites of litter and positively with litter N, litter chemistry was not genotypically linked to litter mass loss. Conclusions Contrary to our expectations, these results suggest that natural selection may have limited influence on overall microbial DNA and litter decomposition rate in B. pendula populations by reworking the genetically controlled foliage chemistry of these populations.

Processes underlying soil organic matter (SOM) transformations are meeting growing interest as SOM contains more carbon (C) than global vegetation and the atmosphere combined. Therefore, SOM is a crucial element of the C cycle, especially in ecosystems rich in organic matter, such as boreal forests. However, climate change may shift the fate of this SOM from C sink into C source, accelerating global warming. These processes require a better understanding of the involved mechanisms driving both the C cycle and the interlinked nitrogen (N) cycle. SOM transformations are balanced by a network of interactions between biological, chemical and physical factors. In this review, we discuss the findings of the most recent studies to the current state of knowledge about the main drivers in SOM transformations. We focus on plant-derived secondary metabolites, as their biochemical traits, especially interactions with soil microbial communities, organic N compounds and enzymes make them potential regulators of SOM decomposition. However, these regulatory abilities of plant-derived compounds are not fully explored.

Background and Aims The oxalate-carbonate pathway (OCP) has been observed in acidic tropical soils with low alkaline cation content where compartments are transient and fed by the rapid turnover of organic matter. By acting on edaphic parameters, the OCP may influence soil nutrient distribution. This study aims at assessing the influence of the OCP on soil nutrients within an agroforestry system associated to oxalogenic iroko trees. Methods Soil nutrient distribution was studied in a 30 m long and 1 m deep transect starting at the iroko tree towards the vegetation surrounding it. Results Processes controlling nutrient distributions varied with both distance and depth. The tree drastically impacted edaphic variables, in the first instance pH. Changes in pH generated gradients of calcium and magnesium, both of the exchangeable and the total fraction. In contrast, total phosphorus and potassium distribution were mostly influenced by depth. Conclusions This downward gradient fits the "plant cycling model" that explains the effect of vegetation on the recharge of soil nutrients. This is the first example of the effect of the OCP on soil nutrient distribution. Considering that the OCP is not restricted to the iroko tree, this study highlights a more general pattern of forest dynamics developed on highly weathered tropical soils.

Three species of the invasive polychaete genus Marenzelleria are among the dominant benthic taxa in many, especially deeper, areas in the Baltic Sea. The population dynamics of the polychaetes in the Baltic are, however, still largely unknown. We conducted monthly samplings of the benthic communities and environmental parameters at five sites with differing depths and sediment characteristics in the northern Baltic Sea (59 degrees 50.896', 23 degrees 15.092') to study the population dynamics, productivity and growth of Marenzelleria spp. from April 2013 to June 2014. The species of Marenzelleria occurring at the study sites were identified by genetic analyses. At the deepest site (33 m) only M. arctia was present, while all three species were found at the shallower, muddy sites (up to 20 m depth). At the shallow (6 m) sandy site only M. viridis and M. neglecta occurred. The sites differed in the seasonal dynamics of the Marenzelleria spp. population, reflecting the different species identities. The muddy sites up to 20 m depth showed clear seasonal dynamics, with the population practically disappearing by winter, whereas more stable populations occurred at the deepest site and at the sandy site. The highest density, biomass and production were observed at the 20 m deep, organic-rich muddy site where all three species recruited. The seasonally very high densities are likely to have important consequences for organic matter processing, and species interactions at these sites. The observed high productivity of the populations has possibly facilitated their establishment, and considerably increased secondary production in especially the deeper areas.

Although the functioning of river floodplains as sink or source of nutrients has been studied extensively for temperate regions, similar studies in tropical regions are less abundant and studies integrating data about floodplain soil, vegetation, and water are scarce. We examined and compared nutrient contents in soil, water, and vegetation tissue in two different vegetation zones on the monsoon Songkhram river floodplain (Thailand). Significant differences were found between bamboo and grass zones. The soil in the bamboo zone is more fertile than the soil in the grass zone, as indicated by the lower C/N ratio, and has significantly higher organic matter and higher total N and K. Bamboo leaf tissue had significantly higher concentrations of nutrients than grass biomass. The growth of the bamboo is P-limited or P and N co-limited, but grass is N-limited. In both zones, the soil-available P and organic carbons after flooding were significantly lower than before flooding. Floodwater in both zones had low dissolved solid concentrations. After the flood peak, most concentrations tended to increase, especially organic carbon and dissolved nitrogen but phosphorus decreased. The results suggest a significant loss of organic carbon from the soil after flooding, indicating that the floodplain acts as a source of carbon that is exported downstream. Nonetheless it is also evident that the floodwater brings in sediment and nutrients. Based on rough estimations of nutrient budgets we conclude that the highly productive bamboo zone adjacent to the river filters out the nutrients before they reach the grass zone.

The objective of this study was to evaluate the effects of seven nitrogen (N2)-fixing and/or phosphorus (P)-solubilizing and siderophore-producing microorganism based bio-fertilizers in single and triple strain combinations isolated from the acidic rhizospheric soil of native tea, grapevine, and wild red raspberries. As a result of this study, bacterial efficiency was found to be variable and depended on the bacterial strains and evaluated growth parameters. Plant growth-promoting rhizobacteria (PGPR) has improved macro- and micro-nutrient concentrations in grapevine leaves, and stimulated plant growth. Triple inoculation and single inoculation based bio fertilizers were found to stimulate overall plant growth, including shoot and leaf weight, main shoot length, leaf ground index, chlorophyll, nitrogen, zinc and iron content of grapevine cv ‘Italy’. Bio-fertilizers increased the nutrients such as nitrogen, zinc and iron concentrations and consequently increased the chlorophyll content of the leaves. © 2018, © 2018 Taylor & Francis.

This work presents the result of a study carried out in the north-western Adriatic Sea, by combining two different types of biogeochemical models with field sampling efforts. A longline mussel farm was taken as a local source of perturbation to the natural particulate organic carbon (POC) downward flux. This flux was first quantified by means of a pelagic model of POC deposition coupled to sediment trap data, and its effects on sediment bioirrigation capacity and organic matter (OM) degradation pathways were investigated constraining an early diagenesis model by using original data collected in sediment porewater. The measurements were performed at stations located inside and outside the area affected by mussel farm deposition. Model-predicted POC fluxes showed marked spatial and temporal variability, which was mostly associated with the dynamics of the farming cycle. Sediment trap data at the two sampled stations (inside and outside of the mussel farm) showed average POC background flux of 20.0–24.2 mmol C m−2 d−1. The difference of organic carbon (OC) fluxes between the two stations was in agreement with model results, ranging between 3.3 and 14.2 mmol C m−2 d−1, and was primarily associated with mussel physiological conditions. Although restricted, these changes in POC fluxes induced visible effects on sediment biogeochemistry. Observed oxygen microprofiles presented a 50 % decrease in oxygen penetration depth (from 2.3 to 1.4 mm), accompanied by an increase in the O2 influx at the station below the mussel farm (19–31 versus 10–12 mmol O2 m−2 d−1) characterised by higher POC flux. Dissolved inorganic carbon (DIC) and NH4+ concentrations showed similar behaviour, with a more evident effect of bioirrigation underneath the farm. This was confirmed through constraining the early diagenesis model, of which calibration leads to an estimation of enhanced and shallower bioirrigation underneath the farm: bioirrigation rates of 40 yr−1 and irrigation depth of 15 cm were estimated inside the shellfish deposition footprint versus 20 yr−1 and 20 cm outside. These findings were confirmed by independent data on macrofauna composition collected at the study site. Early diagenesis model results indicated a larger organic matter mineralisation below the mussel farm (11.1 versus 18.7 mmol m−2 d−1), characterised by similar proportions between oxic and anoxic degradation rates at the two stations, with an increase in the absolute values of oxygen consumed by OM degradation and reduced substances re-oxidation underneath the mussel farm.

Litter decomposition represents a major contribution to the carbon and nutrient fluxes in forest ecosystems. Nutrient dynamics from decomposing leaf litter were measured for 3 years (1095 days) from three dominant tree species (Quercus serrata, Carpinus laxiflora, Carpinus cordata) in a broadleaved deciduous forest of the Geumsan (Mt.) Long-Term Ecological Research (LTER) site in Korea. Mass loss rates from decomposing leaf litter were significantly lower in the Q. serrata leaf litter (63.4% of the original mass) than in C. laxiflora (80.0%) and C. cordata (83.1%) leaf litter over 1095 days. There was a significant linear relationship between the remaining mass of leaf litter and the incubation months of litterbag (Q. serrata: r2 = 0.96; C. laxiflora: r2 = 0.96; C. cordata: r2 = 0.95). Nitrogen and phosphorus concentrations (mg −1) and remaining stocks (mg bag −1) from decomposing leaf litter were significantly lower in Q. serrata leaf litter than in C. laxiflora and C. cordata leaf litter during the study period. Calcium and magnesium concentration and remaining stocks of initial stage from decomposing litter were significantly higher in C. cordata leaf litter than in that of C. laxiflora and Q. serrata. However, potassium concentration and remaining stocks were not affected by the three leaf litter types. The results indicate that Carpinus spp. (C. laxiflora, C. cordata) leaf litter is a significant and easily decomposable source of nutrients among dominant tree species of a mixed broadleaved deciduous forest in the Geumsan LTER site. Refereed/Peer-reviewed

Given the scarcity of manure and the limited land available for fallowing, cotton cultivation with its input credit schemes is often the main entry point for nutrients in cropping systems of West Africa. In an experiment carried out during 25 years in southern Mali, the crop and soil responses to organic fertilizer (=OF), inorganic fertilizer (=IF), and a combination of both (=OIF) were quantified and compared to a control treatment for a typical cotton-sorghum-groundnut rotation. From 1965 to 1979 (15 years, period 1), fertilizers were only applied on cotton and the control treatment was not fertilized. From 1980 to 1989 (10 years, period 2), the amount of manure applied was split between cotton and sorghum, and inorganic fertilizers were applied to the three crops. Inorganic fertilizers were also applied to plots with cotton and sorghum that were previously unfertilized control treatments. In favorable rainfall seasons maximum yields of fertilized treatments reached ca. 3.5 t ha −1 in the case of cotton and groundnuts, and ca. 2 t ha −1 in the case of sorghum. During period 1, cotton yields were steady (ca. 1 t ha −1 ) when no fertilizers were added. Cotton yields were 20% higher in the OF and OIF treatments than in the IF treatment. Sorghum and groundnut benefited from residual effects of fertilizer application on cotton leading to a 200% and 50% yield increase respectively compared to the control treatment. During period 2, yields of the three crops were similar across fertilized treatments. Groundnut yields in the OF treatment, and cotton yields in the OF and IF treatments were respectively 45%, 30% and 20% significantly higher than those in the respective control treatments. No added benefit on crop yields was observed from the combined use of inorganic and organic fertilizer. Soil nutrient contents (SOC, N, P, K) did not significantly change in any of the treatments after 25 years. Soil pH decreased in treatments receiving inorganic fertilizer. Despite low level of soil organic matter, crops responded to organic or inorganic fertilization and crop productivity over time was mostly influenced by the interaction between fertilization and rainfall variability. Our results highlight the role of cotton in West African landscapes as an entry point of nutrients via fertilization, which impacts positively on the productivity of the other crops in the rotation. Credit schemes by the cotton company for farmers to purchase fertilizer to which they would otherwise not have access are thus crucial for sustained crop productivity.

Tannins, an abundant group of plant secondary compounds, raise interest in different fields of science, owing to their unique chemical characteristics. In chemical ecology, tannins play a crucial role in plant defense against pathogens, herbivores, and changing environmental conditions. In the food industry and in medicine, tannins are important because of their proven positive effect on human health and disease treatment, Such wide interests fueled studies on tannin chemistry, especially on their flagship ability to precipitate proteins. In this Review, we expand the basic knowledge on tannin chemistry to the newest insights from the field. We focus especially on tannin reactions with different non-protein organic N compounds, as well as the complex interactions of tannins with enzymes, resulting in either an increase or decrease in enzyme activity.

Although aquatic ecologists and biogeochemists are well aware of the crucial importance of ecosystem functions, i.e., how biota drive biogeochemical processes and vice-versa, linking these fields in conceptual models is still uncommon. Attempts to explain the variability in elemental cycling consequently miss an important biological component and thereby impede a comprehensive understanding of the underlying processes governing energy and matter flow and transformation. The fate of multiple chemical elements in ecosystems is strongly linked by biotic demand and uptake; thus, considering elemental stoichiometry is important for both biogeochemical and ecological research. Nonetheless, assessments of ecological stoichiometry (ES) often focus on the elemental content of biota rather than taking a more holistic view by examining both elemental pools and fluxes (e.g., organismal stoichiometry and ecosystem process rates). ES theory holds the promise to be a unifying concept to link across hierarchical scales of patterns and processes in ecology, but this has not been fully achieved. Therefore, we propose connecting the expertise of aquatic ecologists and biogeochemists with ES theory as a common currency to connect food webs, ecosystem metabolism, and biogeochemistry, as they are inherently concatenated by the transfer of carbon, nitrogen, and phosphorous through biotic and abiotic nutrient transformation and fluxes. Several new studies exist that demonstrate the connections between food web ecology, biogeochemistry, and ecosystem metabolism. In addition to a general introduction into the topic, this paper presents examples of how these fields can be combined with a focus on ES. In this review, a series of concepts have guided the discussion: (1) changing biogeochemistry affects trophic interactions and ecosystem processes by altering the elemental ratios of key species and assemblages; (2) changing trophic dynamics influences the transformation and fluxes of matter across environmental boundaries; (3) changing ecosystem metabolism will alter the chemical diversity of the non-living environment. Finally, we propose that using ES to link nutrient cycling, trophic dynamics, and ecosystem metabolism would allow for a more holistic understanding of ecosystem functions in a changing environment.

Biochar can be produced from several organic sources with varying nutrients and metal concentrations. Four commercial grade biochars were evaluated as peat substitute. Biochars were characterised for plant nutrients and for biological stability. The results showed that there were negligible quantities of N and P and generally high levels of K and high biological stability. When these materials were mixed with peat at 10, 25 and 50% and nutrients were added to bring them to the same level of nutrients as in fertilized peat, it was found that biochar mixtures considerably reduced the levels of calcium chloride/DTPA (CAT) extractable N (including nitrate), P, and electrical conductivity– greater extent with higher rates of biochar addition except for K. The pH and K levels were increased with biochar addition. The drop in EC has important implications regarding the use of other materials used to dilute peat, for example, composted green waste, the rate of dilution is limited due to high EC and biochar addition gives the potential for higher peat dilution of these materials. Nitrate and phosphorus are very vulnerable to leaching of these nutrients in the environment in peat substrates and the binding of these by biochar has implication for leaching and nutrient application strategy. Root development using Cress test and tomato plant height and biomass using containers, were in some cases better than peat indicating that biochar could be used to dilute peat e.g. for seedling production where root development and rapid growth are very important. Application of biochars resulted in a marked reduction of N (and P) in the plant. There were significant correlation between CAT extractable N and P and corresponding plant concentration, indicating the standard growing media test, CAT, would be suitable for assessing the nutrient status of peat biochar mixes.

International audience; A major challenge of current ecological research is to determine the responses of plant and animal communities and ecosystem processes to future environmental conditions. Ecosystems respond to climate change in complex ways, and the outcome may significantly depend on biodiversity. We studied the relative effects of enhanced drought and of plant species mixture on soil biota and on litter decomposition in a Mediterranean oak forest. We experimentally reduced precipitation, accounting for seasonal precipitation variability, and created a single-species litter (Quercus pubescens), a two-species litter mixture (Q. pubescens + Acer monspessulanum) and a three-species litter mixture (Q. pubescens + A. monspessulanum + Cotinus coggygria).In general, drier conditions affected decomposers negatively, directly by reducing fungal biomass and detritivorous mesofauna, and also indirectly by increasing the predation pressure on detritivorous mesofauna by predatory mesofauna. This is reflected under drier conditions in that Collembola abundance decreased more strongly than Acari abundance. One Collembola group (i.e. Neelipleona) even disappeared completely. Increased drought strongly decreased litter decomposition rates. Mixed litter with two and three plant species positively affected soil biota communities and led to a more efficient litter decomposition process, probably through a greater litter quality. Faster decomposition in mixed litter can thus compensate slower decomposition rates under drier condition. Synthesis. Our results highlight that, within our study system, drier climate strongly impacts on soil biodiversity and hence litter decomposition. Species-rich litter may mitigate such a decline in decomposition rates. Diverse plant communities should hence be maintained to reduce shifts in ecosystem functioning under climate change.

Dissolved inorganic nutrients (NO2--N, NO3--N, NH4+-N, and PO43--P) play a critical role in the effective management ofwater quality and prevention of fish and shrimp diseases in aquaculture systems. In this study, dissolved inorganic nutrient concentrations in the water column and sediment porewater, and the fluxes across the sediment-water interface (SWI) were investigated in three intensive shrimp ponds with zero water exchange to examine nutrient cycling during the different growth stages of shrimps. Distinct changes in the dissolved inorganic nutrient concentrations in both the water column and sediment porewater were observed among the three growth stages. Average NO2--N, NO3--N, NH4+-N, and PO43--P concentrations in the sediment porewater were 3.53, 2.81, 29.68, and 6.44 times higher, respectively, than those in the water column over the study period, indicating that the pond sediment acted as a net source of nutrients to the water column. This was further supported by the net release of nutrients from the sediments to the water column observed during the incubation experiment. Nutrient fluxes were dominated by NH4+-N, while NOx--N (NO2--N and NO3--N) and PO43--P fluxes remained low. The high rates of NH4+-N release from the sediment highlight the need of taking into account the biogeochemical role of sediments in mitigating the problem of water quality degradation in coastal shrimp ponds. Based on a total water surface area of mariculture ponds and a total mariculture production of 2.57 x 10(6) ha and 2.30 x 10(9) kg, respectively, we estimated conservatively that approximately 4.77 x 10(4) tons of total nitrogen and 3.75 x 10(3) tons of total phosphorus are being discharged annually from the mariculture ponds into the adjacent coastal zones across China. Results demonstrated the importance of aquaculture pond effluent as amajor contributor ofwater pollution in the coastal areas of China, and called for actions to properly treat these effluents in alleviating the eutrophication problem in the Chinese coastal zones. (C) 2017 Elsevier B.V. All rights reserved. Funding Agencies|National Science Foundation of China [41671088]; Study-Abroad Grant Project for Graduates of the School of Geographical Sciences [GSABGP201601]; Graduated Student Science and Technology Innovation Project of the School of Geographical Science, Fujian Normal University [GY201601]; Swedish Council VR; Linkoping University; European Research Council ERC [725546]

International audience; Two pelagic mesocosm experiments were conducted to study the impact of ocean acidification on Mediterranean plankton communities. A first experiment took place in summer 2012 in the Bay of Calvi (France) followed by an experiment in winter 2013 in the Bay of Villefranche (France) under pre-bloom conditions. Nine mesocosms were deployed: three served as controls and six were acidified in a targeted partial pressure of CO2 (pCO2) gradient from 450 to 1250 μatm. The evolution of dissolved organic and inorganic nutrient concentrations was observed using nanomolar techniques. The experiments were characterized by a large contribution of organic nutrients to nutrient pools and contrasting in situ conditions with an inorganic N/P ratio of 1.7 in summer and of 117 in winter. In the Bay of Calvi, initial conditions were representative of the summer oligotrophic Mediterranean Sea. While inorganic phosphate concentrations were depleted during both experiments, in situ inorganic nitrogen concentrations were higher in winter. However, nitrate was rapidly consumed in winter in all mesocosms during the acidification phase, leading to a decrease in N/P ratio to 13. During these first mesocosm experiments conducted in a low nutrient low chlorophyll area, nutrient dynamics were insensitive to CO2 enrichment, indicating that nutrient speciation and related biological processes were likely not impacted. During both experiments, nitrate and phosphate dynamics were controlled by the activity of small species that are favored in low nutrient conditions. In contrast to the theoretical knowledge, no increase in iron solubility at high pCO2 was observed.

The biodiversity in aquatic systems are indirectly controlled by their nutrient dynamics. The abundance of phytoplanktons and zooplanktons depends on the availability of nutrients such as nitrates, phosphates and silicates since these are the building blocks for their further growth. The phytoplanktons act as prey for the next higher trophic level including various fishes and other small organisms. One of the factors that enchant the migratory birds at some particular locations is the availability of the species of organisms that they prey on. In this paper a preliminary analysis is done to explore the nutrient dynamics of selected tropical aquatic systems in order to correlate the arrival of migratory birds at those locations. Water samples are collected from coastal region of Aleppey, Purakkad and Koonthankulam Bird Sancturay. The latter two sites are the important destination of many migratory water birds including Pallus Gull, Heuglins Gull, Bar-headed goose, Comb Duck and Spot Billed Pelican. The samples are analyzed chemically to trace the nutrient compositions and the related chemical parameters such as temperature, pH, conductivity, primary productivity, chloride, salinity, turbidity, nitrate, phosphate, dissolved oxygen and biochemical oxygen demand. Remarkable differences are observed mainly in the composition of phosphate, organic matter content and salinity. Finally, an attempt has been done to correlate the biodiversity of these locations with the chemical parameters and the prevailing nutrient compositions. DOI: http://dx.doi.org/10.3126/ije.v3i1.9943 International Journal of Environment Vol.3(1) 2014: 68-77