Abrahamsenpuggaard6541

Anthropogenic pressure coupled with high rainfall and diverse heterogeneous landscapes (e.g., land use and topography) has resulted in severe water erosion in the red soil hilly region (RSHR) of China. Soil and water conservation measures (SWCMs) have been extensively implemented, and their effects on runoff and sediment control have been widely tested at plot scales. However, it is difficult to gain an overview of the efficiency of SWCMs due to the difficulty of directly upscaling field observations to regional scales. We conducted a meta-analysis of 498 field plots covering 53 sites in the RSHR to evaluate the efficiency of different SWCMs and identify optimal conservation practices. The results were as follows (i) SWCMs involving erosion control (92%) had a greater efficiency than those focusing on runoff reduction (73%). (ii) The implementation of combined measures was more effective than single measures for reducing runoff and soil loss. (iii) All thirty SWCMs showed a significant effect with respect to runoff and sediment control, except for contour tillage effect on reduction of soil loss. (iv) The maximum and minimum ratios between runoff and sediment reduction were found in orchard and cropland, respectively. (v) Six measures, mulching, tree crop + grass, tree crop + hedgerows, tree crop + grass cover + terrace, tree crop + hedgerows + terrace and hedgerows + contour tillage, can be recommended as high effective SWCMs in the RSHR. This study provides a systematic overview quantifying the factors controlling the effectiveness of SWCMs in the RSHR and can serve as a scientific foundation enabling decision makers to implement suitable SWCMs in mitigating land degradation due to water erosion.There is concern for variations of the carbon footprint (CF) and ecosystem service value of carbon sequestration (ESVCS) related to nitrogen (N) fertilizer rate in rice production under future climate change. To explore possible future ecological effects of N fertilizer rate, a DeNitrification-DeComposition (DNDC) model combined with Representative Concentration Pathway (RCP) projections (RCP 4.5 and RCP 8.5) were used to predict the CF and ESVCS of rice production. Torin 2 The model was validated by a two-year field experiment, and then seven N fertilizer levels (0, 75, 150, 190, 225, 300, and 375 kg N/ha) were set for prediction from 2015 to 2050. The validation results indicated a good fit between the DNDC-simulated and observed data of GHG emission and rice yield. Under RCP 8.5, the mean CF was 4.5-8.7% higher and the average ESVCS was 3.6-7.4% lower than those under RCP 4.5. The effects of N fertilizer rate on CF and ESVCS were consistent between the two climate change scenarios. In both RCPs, it was found that CF and ESVCS were mainly influenced by N fertilizer rate due to the latter's effect on CH4 emissions and crop carbon fixation. CH4 was the main contributor to CF during 2015-2050, accounting for 43.9-58.3% of the total CF. Agricultural inputs were also large contributors to CF, and N fertilizer increased the indirect GHG emissions by 24.6-122.2% compared with no N fertilization treatment. Among the studied N fertilizer rates, 190 kg N/ha was the optimal rate, obtaining the lowest CF and highest ESVCS. These results indicate that, under future climate change, an N fertilizer rate of 190 kg N/ha could achieve a trade-off between high yield, reduction of CF, and improvement of ESVCS in rice production.Rapid urbanization and land expansion persistently shrink urban green field, which accelerates soil sealing and land degradation. Spatio-tempral pattern analysis of green field caused by soil sealing contributes to its protection but quantitative tools are rare. Taking Shanghai-Hangzhou Bay Urban Agglomeration (SHBUA) as an example, we interpreted Landsat imagery into three categories green filed (such as farmland, grass, forest etc.), gray field (impervious surface) and water bodies in 1994, 2003, 2009, and 2015. We first analyzed swallowed green field by soil sealing and then calculated density (proportion) of green field in concentric rings using gradient analysis. Results show that green field density increases slowly around the city center followed by a sharp increase from urban core areas to urban fringe, and then slowly increases again until at a stable level, presenting an S-shape overall. We proposed an S-shaped function that can fit the spatial gradient of green field density well in nine represented cities. We further compare spatial gradients of densities of green field and gray field. This study provides a quantitative tool to characterize the spatial distribution of green field within cities, which supports to find hotspots of green field loss due to soil sealing and further identify prior areas for green field protection.There is an increasing need to study the effects of trace metal micronutrients on microorganisms in natural waters. For Fe, small Fe-binding ligands called siderophores, which are secreted from cells and bind Fe with high affinity, have been demonstrated to modulate bioavailability of this critical nutrient. Relatively little is known about secretion of strong Cu-binding ligands (chalkophores) that may help organisms navigate the divide between Cu nutrition and toxicity. A barrier to environmental chalkophore research is a lack of literature on chalkophore analysis. Here we report the development of a quantitative, high-throughput approach to chalkophore screening based on a popular competitive-ligand binding assay for siderophores wherein ligands compete for metal in a chromogenic ternary complex of chrome azurol sulfonate-metal-surfactant. We developed the assay for high-throughput analysis using a microplate reader. The method performance is slightly better than that of comparable screening approaches for siderophores. We find that levels of other metals in natural samples may be capable of causing matrix interferences (a neglected source of analytical uncertainty in siderophore screening) and that for our method this can be overcome by standard additions. In this respect the high-throughput nature of the technique is a distinct advantage. To demonstrate practical use, we tested samples from field mesocosm studies that were set up with and without Cu and Fe amendments; we find trends in results that are logical in the environmental context of our application. This approach will be useful in areas such as risk assessment for a rapid survey of metal speciation and bioavailability; investigators who perform structural studies might also benefit from this approach to rapidly screen and select samples with high Fe/Cu binding capacity for further study.