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1.
Soil carbon (C) saturation implies an upper limit to a soil's capacity to store C depending on the contents of silt + clay and poorly crystalline Fe and Al oxides. We hypothesized that the poorly crystalline Fe and Al oxides in silt + clay fraction increased the C saturation and thus reduced the capacity of the soil to sorb additional C input. To test the hypothesis, we studied the sorption of dissolved organic carbon (DOC) on silt + clay fractions (<53 µm) of highly weathered oxic soils, collected from three different land uses (i.e., improved pasture, cropping and forest). Soils with high carbon saturation desorbed 38% more C than soils with low C saturation upon addition of DOC, whereas adsorption of DOC was only observed at higher concentration (>15 g kg?1). While high Al oxide concentration significantly increased both the saturation and desorption of DOC, the high Fe oxide concentration significantly increased the desorption of DOC, supporting the proposition that both oxides have influence on the DOC sorption in soil. Our findings provide a new insight into the chemical control of stabilization and destabilization of DOC in soil.  相似文献   
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In this study, we identified the causative agent of postharvest gray-mold rot in sweet persimmon fruit that were collected from Gangneung, Gangwon Province, Korea in October 2016. Symptoms included extensive growth of mycelia on post harvested fruit. The fungus was isolated from infected fruit and cultured on potato dextrose agar (PDA). For identification of the fungus, we examined morphology characteristics and rDNA sequencing analysis of the fungus and confirmed its pathogenicity according to Koch’s postulates. The results of morphological examinations, pathogenicity tests, 5.8S rDNA sequences of the internal transcribed spacer regions (ITS1 and ITS4) and the five nuclear protein-coding genes G3PDH, HSP60, RPB2, MS547 and TUB revealed that the causal agent of postharvest gray-mold rot on sweet persimmon fruit in Korea was Botrytis cinerea.  相似文献   
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Salicylic acid (SA) is an inducer of systemic acquired resistance (SAR) and could be a potential candidate in the control of plant virus diseases. In this study we assayed under controlled conditions the potential effect of three doses of exogenous SA treatment on tomato plants infected with Potato virus X (PVX) and measured their effects on: different physiological parameters (gas exchange, stable isotopes, chlorophyll content), the activation of secondary metabolism, viral accumulation and induction of the expression of pathogenesis-related proteins (PRs) such as ß-1, 3-glucanase (PR2) and chitinase (PR3). SA treatment increased the expression of PR2, the activity of phenylalanine ammonia lyase (PAL) and the concentration of antioxidant compounds at 7 days post-treatment. Earlier expression of PR3 compared to PR2 was observed. SA treatment delayed the detection of PVX by ELISA in uninoculated leaves of mechanically infected tomato plants. Although the effect of PVX infection on physiological parameters was weak, moderate SA treatments showed enhanced photosynthesis, particularly for infected plants. The results obtained confirm that SA promotes major changes in the induction of resistance in tomato plants and suggest that treatment with exogenous SA could be considered to reduce the infections caused by PVX.  相似文献   
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This study examined the effects of organic enrichment on water column, sediments and macrofauna caused by a fish farm in the Mediterranean Sea. Samples were collected on four sampling campaigns over a one‐year cycle. Significant differences were found in the water column in dissolved oxygen, dissolved inorganic nitrogen, phosphate and total phosphorus concentrations between the fish farm and the control. The increase in the dissolved inorganic nitrogen and phosphate concentrations at the fish farm modified the stoichiometric ratios between nutrients, with silicate acting as limiting nutrient at the fish farm 11% more than at the control. Nevertheless, chlorophyll a concentration in the water column was higher at the control station, probably due to the fouling of the underwater fish farm structures. Significant differences were found in sediment concentrations of organic matter, total phosphorus and redox potential between the fish farm and the control. The Canonical Correlation Analysis indicated that organic matter, total phosphorus, redox potential and% of gravels accounted for 68.9% of the total variance in the species data. Changes were observed in macrofauna, with a decrease in number of species and up to a nine‐fold increase in abundance with respect to the control.  相似文献   
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Context

Many nearshore species are distributed in habitat patches connected only through larval dispersal. Genetic research has shown some spatial structure of such metapopulations and modeling studies have shed light onto possible patterns of connectivity and barriers. However, little is known about human impact on their spatial structure and patterns of connectivity.

Objectives

We examine the effects of fishing on the spatial and temporal dynamics of metapopulations of sedentary marine species (red sea urchin and red abalone) interconnected by larval dispersal.

Methods

We constructed a metapopulation model to simulate abalone and sea urchin metapopulations experiencing increasing levels of fishing mortality. We performed the modularity analysis on the yearly larval connectivity matrices produced by these simulations, and analyzed the changes of modularity and the formation of modules over time as indicators of spatial structure.

Results

The analysis revealed a strong modular spatial structure for abalone and a weak spatial signature for sea urchin. In abalone, under exploitation, modularity takes step-wise drops on the path to extinction, and modules breakdown into smaller fragments followed by module and later metapopulation collapse. In contrast, sea urchin showed high modularity variation, indicating high- and low-mixing years, but an abrupt collapse of the metapopulation under strong exploitation.

Conclusions

The results identify a disruption in larval connectivity and a pattern of collapse in highly modular nearshore metapopulations. These results highlight the ability of modularity to detect spatial structure in marine metapopulations, which varies among species, and to show early changes in the spatial structure of exploited metapopulations.
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