nutrient inputs
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2022 ◽  
Vol 5 ◽  
Author(s):  
Juergen Esperschuetz ◽  
Mark Bloomberg

Intensive pastoral farming has been linked to adverse environmental effects such as soil degradation and increased fluxes of nitrogen, phosphorus, sediments, and pathogens into waterways, resulting in their degradation. Stand-off pads are engineered structures covered with bedding materials, available for occupation by stock to minimise those adverse effects to soil and water bodies. Wood chips are ideal for bedding due to their low cost, high water holding capacity, and stock preference as resting areas. While they reduce the mobility of both nutrients and pathogens, their effectiveness depends on the type of wood, size of the chips, pH, pad design, and feeding management used. Dissolved organic carbon, present in wood residue, may slow nitrogen mineralisation thereby decreasing loss via leachate. This effect depends on plant tannins and nutrients already stored within the plant tissue. Poplar and willow have high concentrations of tannins in leaves and bark with potential nitrification-inhibiting properties. When grown on-farm, these deep-rooted trees also reduce nitrogen leaching and prevent soil erosion. This review addresses the use of temporary stand-off pads within poplar or willow silvopastoral systems. Harvested trees can provide suitable wood chips for constructing the stand-off pad, while the deep rooting systems of the trees will reduce the moisture content of the pad, preventing waterlogging. A key objective is to discuss the feasibility and establishment of multiple temporary stand-off pads that allow for stock rotation from pad to pad, and subsequent on-site composting of wood-wastes into fertiliser, reducing both nutrient inputs and losses in agricultural systems. The review highlights the potential suitability of poplar and willow tree species for such a system.


Author(s):  
Emma Ladouceur ◽  
Shane Blowes ◽  
Jonathan Chase ◽  
Adam Clark ◽  
Magda Garbowski ◽  
...  

Global change drivers such as anthropogenic nutrient inputs simultaneously alter biodiversity, species composition, and ecosystem functions such as above ground biomass. These changes are interconnected by complex feedbacks among extinction, invasion, and shifting relative abundance. Here, we use a novel temporal application of the Price equation to separate species richness and biomass change through time and quantify the functional contributions of species that are lost, gained, and persist under ambient and experimental nutrient addition in 59 global grasslands. Under ambient conditions, compositional and biomass turnover was high, but species losses (i.e., local extinctions) were balanced by gains (i.e. colonization). Under fertilization, there was biomass loss associated with species loss. Few species were gained in fertilized conditions over time but those that were, and species that persisted, contributed to net biomass gains, outweighing biomass loss. These components of community change are associated with distinct effects on measures of ecosystem functioning.


2022 ◽  
Author(s):  
Gabriela Musin ◽  
María Victoria Torres ◽  
Débora de Azevedo Carvalho

The Metabolic Theory of Ecology (MET) and the Ecological Stoichiometry Theory (EST) are central and complementary in the consumer-driven recycling conceptual basis. The comprehension of physiological processes of organisms at different levels of organizations is essential to explore and predict nutrient recycling behavior in different scenarios, and to design integrated productive systems that efficiently use the nutrient inputs through an adjusted mass balance. We fed with fish-feed three species of decapods from different families and with aquacultural potential to explore the animal-mediated nutrient dynamic and its applicability in productive systems. We tested whether physiological (body mass, body elemental content), ecological (diet), taxonomic and experimental (time of incubation) variables predicts N and P excretion rates and ratios across and within taxa. We also analysed body mass and body elemental content independently as predictors of N and P excretion of decapods across, among and within taxa. Finally, we verified if body content scales allometrically across and within taxa and if differed among taxa. Body mass and taxonomic identity predicted nutrient excretion rates both across and within taxa. When physiological variables were analysed independently, body size best predicted nutrient mineralization in both scales of analyses. Regarding body elemental content, only body P content scaled negatively with body mass across taxa. Results showed higher N-requirements and lower C:N of prawns than anomurans and crabs. The role of crustaceans as nutrient recyclers depends mainly on the species and body mass, and should be considered to select complementary species that efficiently use feed resources. Prawns need more protein in their feed and might be integrated with fish of higher N-requirements, while crabs and anomurans, with fish of lower N-requirements. Our study contributed to the background of MTE and EST through empirical data obtained from decapods and provided useful information to achieve more efficient aquaculture integration systems.


2022 ◽  
Author(s):  
Zhibo Shao ◽  
Ya-Wei Luo

Abstract. Heterotrophic diazotrophs emerge as a potentially important contributor to the global marine N2 fixation, while the factors controlling their distribution are unclear. Here, we explored what controls the distribution of the most sampled heterotrophic diazotroph phylotype, Gamma A, in the global ocean. First, we analyzed the relationship between nifH-based Gamma A abundance and climatological biological and environmental conditions. The carrying capacity of Gamma A abundance increased with net primary production (NPP) and saturated when NPP reached ~400 mg C m−2 d−1. The reduction in Gamma A abundance from its carrying capacity was mostly related to low temperature, which possibly slowed the decomposition of organic matter, and high concentration of dissolved iron, to which the explanation was elusive but could result from the competition with autotrophic diazotrophs. Using a generalized additive model, these climatological factors together explained 41 % of the variance in the Gamma A abundance. Second, in additional to the climatological background, we found that mesoscale cyclonic eddies can substantially elevate Gamma A abundance, implying that Gamma A can respond to short-term features and benefit from stimulated primary production by nutrient inputs. Overall, our results suggest that the distribution of Gamma A is most likely determined by the supply of organic matters, not by those factors controlling autotrophic diazotrophs, and therefore insight a niche differentiation between the heterotrophic and autotrophic N2 fixation. More samplings on Gamma A and other heterotrophic diazotroph phylotypes are needed to better reveal the controlling mechanisms of heterotrophic N2 fixation in the ocean.


2022 ◽  
Vol 174 ◽  
pp. 113298
Author(s):  
Nicolò Casella ◽  
Giulio Careddu ◽  
Edoardo Calizza ◽  
Simona Sporta Caputi ◽  
Loreto Rossi ◽  
...  

2021 ◽  
Author(s):  
Vojtech Kolar ◽  
Katerina Francova ◽  
Jaroslav Vrba ◽  
Stanislav Grill ◽  
David Boukal

Fishponds play a key role in current pondscapes in many developed countries. Their littoral areas, supporting multiple ecosystem functions including the maintenance of aquatic and riparian biodiversity, have been adversely affected by the move shift towards more intensive aquaculture and widespread eutrophication in the middle 20th century. To counteract these changes, many fishponds received some protection, but its long-term efficiency has not been studied. Here we focus on the role of conservation status in protecting the area of littoral areas of fishponds in Czechia between the years 1950 and 2019. We found that the conservation status of these fishponds did not prevent habitat deterioration in most of the fishponds, especially during the second half of the 20th century. Moreover, we detected no significant effects of the reserve establishment year, fishpond area and conservation target on the littoral areas. This suggests that the conservation measures are insufficient across fishpond reserve types. We attribute the negative trends to persisting high fish stocks, especially of common carp, and eutrophication resulting from additional feeding, pond manuring, and ongoing nutrient inputs from the pond catchments. Sediment dredging and high grazing pressure by waterfowl in some reserves can further aggravate the situation. We conclude that effective protection of the littoral areas requires a paradigm shift towards less intensive fish stock management, more frequent summer drainage, and effective reduction of all nutrient inputs to increase the water quality. Such measures can help recover the littoral areas and the associated biota.


2021 ◽  
Author(s):  
Yuval R. Zelnik ◽  
Stefano Manzoni ◽  
Riccardo Bommarco

Ecosystems worldwide receive large amounts of nutrients from both natural processes and human activities. While direct subsidy effects on primary productivity are relatively well known (the green food web), the indirect effects of subsidies on producers as mediated by the brown food web and predators have been neglected. With a dynamical green-brown food web model, parameterized using empirical estimates from the literature, we illustrate the effect of nutrient subsidies on net primary productivity (i.e., after removing loss to herbivory) in two generic ecosystems, terrestrial and aquatic. We find that nutrient subsidies increase net primary productivity because more nutrients are available, but this effect saturates with higher subsidies. Changing the quality of subsidies from inorganic to organic tends to increase net primary productivity in terrestrial ecosystems, but less often so in aquatic ecosystems. This occurs when organic nutrient inputs promote detritivores in the brown food web, and hence predators that in turn control herbivores, thus promoting primary productivity. This previously largely overlooked effect is further enhanced by ecosystem properties such as fast decomposition and low rates of nutrient additions, and demonstrates the importance of nutrient subsidy quality on ecosystem functioning.


Author(s):  
G. Anjana Devaraj ◽  
Sheeba Rebecca Isaac

Background: Bio-recycling of crop residues is contemplated as an environment friendly soil enrichment and conservation practice that sustains agricultural productivity in the long run. Legume residues are privileged by the unique nitrogen fixing capacity and rhizospheric properties that enhance soil fertility, thereby reducing the need for chemical nutrient inputs. The present study was conducted to evaluate the residual effect of red gram on fodder maize cultivated as succeeding crop in the southern laterites of Thiruvananthapuram district, Kerala, India. Methods: The field experiment to assess the effect of red gram residue incorporation on the growth and yield of fodder maize was carried out in the Instructional Farm, College of Agriculture, Vellayani, Kerala during June - August 2019. Fodder maize (African tall) was sown in the plots after incorporation of crop residues of red gram varieties (APK 1 and Vamban (Rg) 3) grown under different planting geometry (40 cm x 20 cm and 60 cm x 30 cm) and NPK doses (40:80:40, 30:60:30 and 20:40:20 kg NPK ha-1) and compared with the package of practices recommendation and in randomized block design (RBD) replicated thrice. Result: Significantly higher quantities of red gram residues were realised and incorporated in the treatments involving a planting geometry of 40 cm x 20 cm and an NPK dose of 40:80:40 kg NPK ha-1 in both varieties used, Vamban (Rg) 3 and APK 1 (T7 and T1). Nutrient contents in the residues and decomposition in T1 and T7 resulted in the maximum additions in soil, available N, P and K status and dehydrogenase activity. Evaluation of the residual effects of the legume on fodder maize revealed the significantly highest growth and yields in maize raised with chemical fertilizers as per package recommendation and, among the residue incorporated treatments, maximum plant height and fodder yields were recorded in the treatment in which residues of Vamban (Rg) 3 raised at 40 cm x 20 cm spacing and fertilised with 40:80:40 kg NPK ha-1 were incorporated, on par with variety APK 1 raised under same management practice. The green fodder yield with residue incorporation was 80-90 per cent that under chemical fertilizer managed treatment. Among the quality parameters, crude protein (9.30%) was the highest with chemical fertilizer application while carbohydrate content (66.23%) was the lowest.


2021 ◽  
Vol 8 ◽  
Author(s):  
Anouk Ollevier ◽  
Jonas Mortelmans ◽  
Anaïs Aubert ◽  
Klaas Deneudt ◽  
Michiel B. Vandegehuchte

Climate driven changes and anthropogenic pressures on the marine environment have been shown to favor the increase in certain potentially harmful species. Among them, Noctiluca scintillans, a common dinoflagellate, often blooms during warm summers and is known to affect plankton communities. In this study, we assessed the dynamics in abundance and cell size of N. scintillans as well as the relationship between N. scintillans and small soft-bodied zooplankton in the Belgian part of the North Sea (BPNS), since negative correlations between these plankton groups have been previously reported for nearby regions. This study is the first to present consistently counted N. scintillans cell numbers and measured cell lengths, through the analysis of ZooScan images from samples taken monthly at stations throughout the coastal zone of the BPNS. The results show that N. scintillans demonstrated clear seasonal dynamics with both high densities and large cell sizes in spring/summer (May-July). The occurrence of N. scintillans in the analyzed plankton samples and the abundance of N. scintillans at the observed peak intensities nearly tripled over a period of 5 years. A zero-inflated model showed a correlation of N. scintillans abundance with temperature as well as with phosphate concentrations, suggesting that anthropogenic influences such as climate change and riverine nutrient inputs could affect the temporal dynamics of the species. The results, on the other hand, did not show any negative impact of N. scintillans on the soft-bodied plankton community.


2021 ◽  
Vol 12 ◽  
Author(s):  
Lian-Lian Fan ◽  
Okhonniyozov Mekrovar ◽  
Yao-Ming Li ◽  
Kai-Hui Li ◽  
Xue-Xi Ma ◽  
...  

Grasslands provide key resource for the millions of people who are dependent on livestock in Tajikistan. Productivity and species richness (SR) are important characteristics of grassland ecosystems and are greatly affected by nutrient inputs. The effect that climate change might have on these characteristics remains unclear. Here, an in situ nitrogen (N) and phosphorus (P) fertilization experiment was conducted at four sites along with an elevational gradient (650, 1,100, 1,250, and 2,000 m) in western Tajikistan over 2 years (2018 and 2019) to examine the influences of nutrient availability and climate change on aboveground biomass (AGB) and SR; precipitation and temperature were also considered to analyze the responses. It demonstrated that enrichment with N, P, and their combinations significantly increased AGB along with an elevational gradient (p < 0.05). AGB increased as the concentrations of nutrients added increased. The maximum AGB, which was 2-fold higher compared with control, was observed when 90 kg N ha–1year–1 and 30 kg P ha–1year–1 were added. In addition, nitrogen addition alone stimulated greater AGB than P addition, although no significant difference was observed between these two treatments. Enrichment with N, P, and their combination had no significant effect on SR; however, SR significantly changed at different elevation. Elevation had direct effect on precipitation and temperature, which, in turn, resulted in variation in AGB and SR. Moreover, both nutrient and elevation had significant effect on AGB and SR, but there was no interaction effect of them. AGB and SR interacted with significant negative correlation. In the high-elevation area, plants grew better in the warmer year (2018); this indicates that grasslands in high mountain areas in Tajikistan might have higher productivity as the climate warms, which will positively affect the economic development of the country.


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