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Annals of Botany Feb 2012Fine root decomposition is an important determinant of nutrient and carbon cycling in grasslands; however, little is known about the factors controlling root... (Comparative Study)
Comparative Study
BACKGROUND AND AIMS
Fine root decomposition is an important determinant of nutrient and carbon cycling in grasslands; however, little is known about the factors controlling root decomposition among species. Our aim was to investigate whether interspecific variation in the potential decomposition rate of fine roots could be accounted for by root chemical and morphological traits, life history and taxonomic affiliation. We also investigated the co-ordinated variation in root and leaf traits and potential decomposition rates.
METHODS
We analysed potential decomposition rates and the chemical and morphological traits of fine roots on 18 Mediterranean herbaceous species grown in controlled conditions. The results were compared with those obtained for leaves in a previous study conducted on similar species.
KEY RESULTS
Differences in the potential decomposition rates of fine roots between species were accounted for by root chemical composition, but not by morphological traits. The root potential decomposition rate varied with taxonomy, but not with life history. Poaceae, with high cellulose concentration and low concentrations of soluble compounds and phosphorus, decomposed more slowly than Asteraceae and Fabaceae. Patterns of root traits, including decomposition rate, mirrored those of leaf traits, resulting in a similar species clustering.
CONCLUSIONS
The highly co-ordinated variation of roots and leaves in terms of traits and potential decomposition rate suggests that changes in the functional composition of communities in response to anthropogenic changes will strongly affect biogeochemical cycles at the ecosystem level.
Topics: France; Mediterranean Region; Nitrogen; Phosphorus; Plant Leaves; Plant Roots; Poaceae; Soil
PubMed: 22143881
DOI: 10.1093/aob/mcr297 -
The Science of the Total Environment Jul 2022Sediment phosphorus (P) recycling is one of the key issues in lake water quality management. We studied sediment P mobility in Võrtsjärv, a large shallow lake in...
Sediment phosphorus (P) recycling is one of the key issues in lake water quality management. We studied sediment P mobility in Võrtsjärv, a large shallow lake in Estonia using both sorption experiments and long-term (1985-2020) monitoring data of the lake. Over the years studied, the lake has undergone a decline in external phosphorus loading (EL), while no improvement in phytoplankton indicators was observed. The results of the sorption experiments revealed that it may be successfully used as a tool to determine P forms involved in P retention, as up to 100% of the P from the water column was detected in sediments. Incubation of wet sediment is preferred to dry because of the sensitivity of organic P to desiccation. In the sediments of Võrtsjärv, the labile P (Lab-P) and iron bound (Fe-P) fractions are the major forms of the mobile pool that supply internal P load as sediment released P. The internal P load calculated from summer total P (TP) increases (IL) in the water column was on average 42%, but could reach 240% of EL at extreme environmental conditions. IL was correlated with the active area, which resembles the area involved in redox-related P release in polymictic lakes, and with the mean bottom shear stress in summer. IL showed a similar decreasing pattern as the external P load over the years 1985-2020, and was likely driven by the decrease of the pool of releasable P. Similarly, the decreases in sediment loading by P retention in our P sorption experiment were associated with decreases in the concentration of the potentially mobile P forms (mainly Lab-P and Fe-P). These results show that changes in external P loading can successfully control internal P loading and are useful in water quality management of large lakes.
Topics: Environmental Monitoring; Eutrophication; Geologic Sediments; Lakes; Phosphorus; Water Pollutants, Chemical
PubMed: 35306066
DOI: 10.1016/j.scitotenv.2022.154572 -
The Science of the Total Environment Aug 2012One of the consequences of human impacts on floodplains is a change in sedimentation leading to enhanced floodplain aggradation. Thus, accumulated sediments rich in...
One of the consequences of human impacts on floodplains is a change in sedimentation leading to enhanced floodplain aggradation. Thus, accumulated sediments rich in nutrients might interfere with floodplain restoration. In this study we investigated the phosphorus release behavior of sediments from shallow backwaters of an isolated floodplain of the Danube River situated east of the city of Vienna with the aim to understand the effects of changes in dry/wet cycles on established floodplain sediments. In the light of restoration plans aiming at increased surface water exchange with the river main channel, the response of sediments to frequent alternations between desiccation and inundation periods is a key issue as changes of sediment properties are expected to affect phosphorus release. In order to determine the effect of changing hydrological conditions on internal phosphorus loading, we exposed sediments to different dry/wet treatments in a laboratory experiment. Total phosphorus (TP) release from sediments into the water column increased with increasing duration of dry periods prior to re-wetting. Partial correlation analysis showed significant positive correlations between ΔTP and ΔNH(4)(+) as well as between ΔTP and ΔFe(3+) concentrations (Δ refers to the difference between the final and initial concentration during the wetting period), indicating that enhanced mineralization rates leading to a concomitant release of NH(4)(+) and TP and the reduction of iron hydroxides leading to a concomitant release of Fe(3+) and TP are the mechanisms responsible for the rise in TP. Repeated drying and wetting resulted in elevated phosphorus release. This effect was more pronounced when drying periods led to an 80% reduction in water content, indicating that the degree of drying is a major determinant controlling phosphorus release upon re-wetting. The reconnection of isolated floodplains will favor fluctuating hydrologic conditions and is therefore expected to initially lead to high rates of phosphorus release from sediments.
Topics: Austria; Desiccation; Environmental Monitoring; Floods; Geologic Sediments; Phosphorus; Rivers; Time Factors; Water Pollutants, Chemical
PubMed: 22750178
DOI: 10.1016/j.scitotenv.2012.06.025 -
PloS One 2018Assessing algal nutrient limitation is critical for understanding the interaction of primary production and nutrient cycling in streams, and nutrient diffusing substrate...
Assessing algal nutrient limitation is critical for understanding the interaction of primary production and nutrient cycling in streams, and nutrient diffusing substrate (NDS) experiments are often used to determine limiting nutrients such as nitrogen (N) and phosphorus (P). Unexpectedly, many experiments have also shown decreased algal biomass on NDS P treatments compared to controls. To address whether inhibition of algal growth results from direct P toxicity, NDS preparation artifacts, or environmental covariates, we first quantified the frequency of nutrient inhibition in published experiments. We also conducted a meta-analysis to determine whether heterotrophic microbial competition or selective grazing could explain decreases in algal biomass with P additions. We then deployed field experiments to determine whether P-inhibition of algal growth could be explained by P toxicity, differences in phosphate cation (K vs. Na), differences in phosphate form (monobasic vs. dibasic), or production of H2O2 during NDS preparation. We found significant inhibition of algal growth in 12.9% of published NDS P experiments as compared to 4.7% and 3.6% of N and NP experiments. The meta-analysis linear models did not show enhanced heterotrophy on NDS P treatments or selective grazing of P-rich algae. Our field experiments did not show inhibition of autotrophic growth with P additions, but we found significantly lower gross primary productivity (GPP) and biomass-specific GPP of benthic algae on monobasic phosphate salts as compared to dibasic phosphate salts, likely because of reduced pH levels. Additionally, we note that past field experiments and meta-analyses support the plausibility of direct P toxicity or phosphate form (monobasic vs. dibasic) leading to inhibition of algal growth, particularly when other resources such as N or light are limiting. Given that multiple mechanisms may be acting simultaneously, we recommend practical, cost-effective steps to minimize the potential for P- inhibition of algal growth as an artifact of NDS experimental design.
Topics: Autotrophic Processes; Biomass; Eutrophication; Hydrogen Peroxide; Microalgae; Nitrogen; Nutritional Physiological Phenomena; Phosphorus; Rivers
PubMed: 30335857
DOI: 10.1371/journal.pone.0205684 -
Journal of Dairy Science Mar 2008Monitoring or accurately predicting manure quantities and nutrient concentrations is important for dairy farms facing strict environmental regulations. The objectives of...
Monitoring or accurately predicting manure quantities and nutrient concentrations is important for dairy farms facing strict environmental regulations. The objectives of this project were to determine the daily out-flow of manure nutrients from a free-stall barn using mass balance and to compare results with published excretion models. The project was conducted at the free-stall facility housing the lactating cow herd of the Virginia Tech Dairy Center in 2005. The herd consisted of 142 (+/-8.9) Holstein and Jersey cows with a mean body weight of 568 (+/-6.2) kg and average milk yield of 29.8 (+/-1.7) kg/d with 3.18% (+/-0.07) true protein and 3.81% (+/-0.13) milk fat on 18 sampling days. The intakes of dry matter (DM), N, and P were estimated from the formulated ration. Daily consumption averaged 21.7 (+/-0.27) kg of DM with 17.7% (+/-0.26) crude protein and 0.46% (+/-0.03) P. Approximately 110 (+/- 27.9) kg/d of sawdust was used as bedding; its contribution to manure flow was subtracted. The alleys in the free-stall barn were flushed every 6 h with recycled wastewater, and the slurry was collected. On 18 sampling days the volumes and constituents of the flushwater and the flushed manure were determined for a 6-h flush cycle and extrapolated to daily values. Net daily flow of solids and nutrients in manure were calculated as the differences between masses in flushed slurry and flushwater. Nitrogen and P excretion were also calculated from dietary inputs and milk output. The flow was compared with the American Society of Agricultural Engineers' (ASAE) standards. Each cow produced 5.80 kg/d of total solids (remainder after drying at 105 degrees C). The ASAE standard predicted DM (remainder after drying at 60 degrees C) excretion of 8.02 to 8.53 kg/d per cow. Recovery of P amounted to 74.8 g/d per cow. Overall, 102% of intake P was recovered; 75.1% in the manure outflow and 26.9% in milk. About 285 g/d and 148 g/d of N per cow were recaptured in manure and milk, respectively; 182 g/d was presumably volatilized. All models of N excretion appeared to underestimate N excretion. Volatilization rate of N amounted to 18.1%/h for the 6-h flush interval. Measured outflow of manure-P from the facility was similar to excretion predictions. Presentation of excreted solids as both total solids and DM is warranted. We conclude that using excretion prediction equations is useful for predicting excretion and outflow of P in a lactating cow facility, but N excretion predictions exhibited bias and have to be used prudently for predicting N outflow and N volatilization.
Topics: Animals; Body Weight; Cattle; Diet; Eating; Fats; Female; Lactation; Manure; Milk; Milk Proteins; Nitrogen; Phosphorus; Species Specificity; Urea; Volatilization
PubMed: 18292283
DOI: 10.3168/jds.2007-0605 -
Nature Communications Jul 2021Experiments showed that biodiversity increases grassland productivity and nutrient exploitation, potentially reducing fertiliser needs. Enhancing biodiversity could...
Experiments showed that biodiversity increases grassland productivity and nutrient exploitation, potentially reducing fertiliser needs. Enhancing biodiversity could improve P-use efficiency of grasslands, which is beneficial given that rock-derived P fertilisers are expected to become scarce in the future. Here, we show in a biodiversity experiment that more diverse plant communities were able to exploit P resources more completely than less diverse ones. In the agricultural grasslands that we studied, management effects either overruled or modified the driving role of plant diversity observed in the biodiversity experiment. Nevertheless, we show that greater above- (plants) and belowground (mycorrhizal fungi) biodiversity contributed to tightening the P cycle in agricultural grasslands, as reduced management intensity and the associated increased biodiversity fostered the exploitation of P resources. Our results demonstrate that promoting a high above- and belowground biodiversity has ecological (biodiversity protection) and economical (fertiliser savings) benefits. Such win-win situations for farmers and biodiversity are crucial to convince farmers of the benefits of biodiversity and thus counteract global biodiversity loss.
Topics: Agriculture; Biodiversity; Biomass; Fertilizers; Grassland; Latent Class Analysis; Mycorrhizae; Phosphorus; Plants; Soil; Soil Microbiology
PubMed: 34290234
DOI: 10.1038/s41467-021-24714-4 -
Journal of Environmental Management Nov 2023Mechanical separation of anaerobic digestate has been identified as a method to reduce pollution risk to waterways by partitioning phosphorus in the solid fraction and...
Mechanical separation of anaerobic digestate has been identified as a method to reduce pollution risk to waterways by partitioning phosphorus in the solid fraction and reducing its application to land. Separators have adjustable parameters which affect separation efficiency, and hence the degree of phosphorous partitioning, but information on how these parameters affect separation performance is limited in the literature. Two well known technologies were investigated, decanter centrifuge and screw press, to determine the most efficient method of separation. Counterweight load and the use of an oscillator were adjusted for the screw press, while bowl speed, auger differential speed, feed rate and polymer addition were modified for the decanter centrifuge. Separation efficiency was determined for total solids, phosphorus, nitrogen, potassium, and carbon, and the total solids content of resulting fractions was measured. The decanter centrifuge had higher separation efficiency for phosphorus in all cases, ranging from 51% to 71.5%, while the screw press had a phosphorus separation efficiency ranging from 8.5% to 10.9% for digestate of ∼5% solids (slurry/grass silage mix). Separation by decanter centrifuge partitioned up to 56% of nitrogen in the solid fraction leaving a reduced nitrogen content in the liquid fraction available for land spreading; this nitrogen would most likely need to be replaced by chemical fertiliser which would add to the cost of the system. The decanter centrifuge is better suited to cases where phosphorus recovery is the most important factor, while the screw press could be advantageous in cases where cost is a limiting factor.
Topics: Anaerobiosis; Nitrogen; Environmental Pollution; Manure; Phosphorus
PubMed: 37390731
DOI: 10.1016/j.jenvman.2023.118449 -
International Journal of Environmental... Nov 2018Inappropriate grazing management is one of the most common causes of grassland degradation, and thus, an assessment of soil properties under different grazing...
Inappropriate grazing management is one of the most common causes of grassland degradation, and thus, an assessment of soil properties under different grazing intensities is critical for understanding its effects on ecosystem nutrient cycling and for formulating appropriate management strategies. However, the responses of certain main elements, including soil carbon, nitrogen, and phosphorus, to grazing in alpine meadow ecosystems remain insufficiently clarified. Here, we measured carbon, nitrogen, and phosphorus contents in the topmost 30 cm of soil in an alpine meadow under three grazing intensities (light, moderate, and heavy) and found clear differences in soil physical and chemical properties among different grazing intensities and soil layers. As grazing intensity increased, soil water content, carbon and nitrogen contents and stocks, and carbon to phosphorus and nitrogen to phosphorus ratios decreased, whereas soil bulk density increased. However, soil phosphorus and carbon to nitrogen ratio remained stable. Our findings highlight the negative impacts of heavy grazing intensity, in terms of soil carbon and nitrogen loss and phosphorus mineralization. Moreover, we emphasize that further related studies are necessary to gain a more comprehensive understanding of the effects of grazing on grassland ecosystems, and thereby provide information for sustainable management practices and eco-compensation policies.
Topics: Animals; Biomass; Carbon; China; Environmental Monitoring; Grassland; Herbivory; Livestock; Nitrogen; Phosphorus; Soil
PubMed: 30463233
DOI: 10.3390/ijerph15112584 -
Brazilian Journal of Biology = Revista... 2023Considered the economic engine of many countries, the coffee culture represents an important component of the agricultural chain in Brazil. The growing values of...
Considered the economic engine of many countries, the coffee culture represents an important component of the agricultural chain in Brazil. The growing values of commercialization, planting areas, and crop productivity require the acquisition of quality seedlings, which must receive adequate nutritional support through efficient fertilizers. Slow and controlled-release fertilizers, such as organominerals, gain prominence when it comes to increasing efficiency in the use of phosphorus, as well as plant growth-promoting bacteria (PGPB) with phosphate solubilizing characteristics. This study aimed to evaluate the effect of different sources of mineral and organomineral fertilizers, inoculated and non-inoculated with PGPB on the quality parameters of coffee seedlings. In general, the P sources used in the experiment positively interfered with the development of coffee seedlings. This proves that there is a need for nutritional supplementation for the good development of the seedlings. Among the sources used, the organomineral in granulated form showed better performance in coffee seedlings' growth and physiological parameters, proving to be a viable alternative to commonly used fertilizers. The addition of PGPB showed a significant advantage for seedling quality variables.
Topics: Phosphorus; Seedlings; Coffee; Fertilizers; Bacteria
PubMed: 37075429
DOI: 10.1590/1519-6984.270262 -
TheScientificWorldJournal Aug 2001This paper gives a general overview of the nature and important mechanisms behind internal loading of phosphorus (P), which is a phenomenon appearing frequently in... (Review)
Review
This paper gives a general overview of the nature and important mechanisms behind internal loading of phosphorus (P), which is a phenomenon appearing frequently in shallow, eutrophic lakes upon a reduction of the external loading. Lake water quality is therefore not improved as expected. In particular summer concentrations rise and P retention may be negative during most of the summer. The P release originates from a pool accumulated in the sediment when the external loading was high. In most lake sediments, P bound to redox-sensitive iron compounds or P fixed in more or less labile organic forms constitute major fractions--forms that are potentially mobile and eventually may be released to the lake water. The duration of the recovery period following P loading reduction depends on the loading history, but it may last for decades in lakes with a high sediment P accumulation. During the phase of recovery, both the duration and net P release rates from the sediment seem to decline progressively. Internal P loading is highly influenced by the biological structure as illustrated by lakes shifting from the turbid to the clearwater state as a result of, for example, biomanipulation. In these lakes P concentrations may be reduced to 50% of the pre-biomanipulation level and the period with negative retention during summer can thus be reduced considerably. The duration of internal loading can be reduced significantly by different restoration methods such as dredging to remove accumulated P or addition of iron or alum to elevate the sorption capacity of sediments. However, an important prerequisite for achieving long-term benefits to water quality is a sufficient reduction of the external P loading.
Topics: Ecosystem; Eutrophication; Fresh Water; Geologic Sediments; Phosphorus; Phytoplankton; Water Pollutants
PubMed: 12806078
DOI: 10.1100/tsw.2001.72