Erosion reduces soil microbial diversity, network complexity and multifunctionality

While soil erosion drives land degradation, the impact of erosion on soil microbial communities and multiple soil functions remains unclear. This hinders our ability to assess the true impact of erosion on soil ecosystem services and our ability to restore eroded environments. Here we examined the effect of erosion on microbial communities at two sites with contrasting soil texture and climates. Eroded plots had lower microbial network complexity, fewer microbial taxa, and fewer associations among microbial taxa, relative to non-eroded plots. Soil erosion also shifted microbial community composition, with decreased relative abundances of dominant phyla such as Proteobacteria, Bacteroidetes, and Gemmatimonadetes. In contrast, erosion led to an increase in the relative abundances of some bacterial families involved in N cycling, such as Acetobacteraceae and Beijerinckiaceae. Changes in microbiota characteristics were strongly related with erosion-induced changes in soil multifunctionality. Together, these results demonstrate that soil erosion has a significant negative impact on soil microbial diversity and functionality

Transmission of Hypervirulence traits via sexual reproduction within and between lineages of the human fungal pathogen cryptococcus gattii.

Since 1999 a lineage of the pathogen Cryptococcus gattii has been infecting humans and other animals in Canada and the Pacific Northwest of the USA. It is now the largest outbreak of a life-threatening fungal infection in a healthy population in recorded history. The high virulence of outbreak strains is closely linked to the ability of the pathogen to undergo rapid mitochondrial tubularisation and proliferation following engulfment by host phagocytes. Most outbreaks spread by geographic expansion across suitable niches, but it is known that genetic re-assortment and hybridisation can also lead to rapid range and host expansion. In the context of C. gattii, however, the likelihood of virulence traits associated with the outbreak lineages spreading to other lineages via genetic exchange is currently unknown. Here we address this question by conducting outgroup crosses between distantly related C. gattii lineages (VGII and VGIII) and ingroup crosses between isolates from the same molecular type (VGII). Systematic phenotypic characterisation shows that virulence traits are transmitted to outgroups infrequently, but readily inherited during ingroup crosses. In addition, we observed higher levels of biparental (as opposed to uniparental) mitochondrial inheritance during VGII ingroup sexual mating in this species and provide evidence for mitochondrial recombination following mating. Taken together, our data suggest that hypervirulence can spread among the C. gattii lineages VGII and VGIII, potentially creating novel hypervirulent genotypes, and that current models of uniparental mitochondrial inheritance in the Cryptococcus genus may not be universal

New genetic loci link adipose and insulin biology to body fat distribution.

Body fat distribution is a heritable trait and a well-established predictor of adverse metabolic outcomes, independent of overall adiposity. To increase our understanding of the genetic basis of body fat distribution and its molecular links to cardiometabolic traits, here we conduct genome-wide association meta-analyses of traits related to waist and hip circumferences in up to 224,459 individuals. We identify 49 loci (33 new) associated with waist-to-hip ratio adjusted for body mass index (BMI), and an additional 19 loci newly associated with related waist and hip circumference measures (P < 5 × 10(-8)). In total, 20 of the 49 waist-to-hip ratio adjusted for BMI loci show significant sexual dimorphism, 19 of which display a stronger effect in women. The identified loci were enriched for genes expressed in adipose tissue and for putative regulatory elements in adipocytes. Pathway analyses implicated adipogenesis, angiogenesis, transcriptional regulation and insulin resistance as processes affecting fat distribution, providing insight into potential pathophysiological mechanisms

Drying-wetting cycles consistently increase net nitrogen mineralization in 25 agricultural soils across intensity and number of drying-wetting cycles

An increase in extreme weather events such as heavy rainfall and extreme drought causes intensive and frequent drying-wetting (DW) cycles, which have strong effects on the availability of nitrogen (N) for plant growth and development. How the effects of DW cycles on N turnover vary with the intensity and number of DW cycles and soil properties has not been clearly addressed, which hinders predicting soil biogeochemical cycles in a changing world. Herein, we examined the response of net N mineralization in agricultural soils measured at a standard temperature (25&deg;C) to DW cycles varying in intensity and number. A total of 25 soils differing in texture and organic matter content were collected to create a soil property gradient. We also established the relationships of DW cycle effects on net N mineralization to soil properties. The DW cycles significantly increased N mineralization by 11.05&plusmn;0.66 mg kg-1 (+81.7%), and the increase was consistent across DW intensities and numbers for most soils. The release of inorganic N was dependent on soil properties, while the regulation of soil properties on DW effects varied with DW intensity, with stronger regulation under intense DW cycles (60% to 0% field capacity) than under moderate DW cycles (100% to 20% field capacity). The effect of intense DW cycles on NH4+ increased with clay content but decreased with soil pH and sand content. The effect on NO3- has opposite responses to these soil properties when compared with the effects on NH4+. The effect on total inorganic N increased with soil pH and inorganic N concentration. These results indicated that DW cycles have the potential to increase N availability in agricultural soils and highlighted the underestimation of N availability predicted with averaged soil moisture instead of real-time soil moisture under changing soil moisture conditions.</p

Soil physical and hydraulic properties under different land uses in the black soil region of Northeast China

Black soil is inherently productive and fertile but is subject to soil erosion. Understanding the distribution of soil physical and hydraulic properties of the soil profile under various land uses would help reveal the mechanism behind the degradation of black soil. In this study, we investigated the variation in soil physical and hydraulic properties with land uses and soil depths in the black soil area of Northeast China. Disturbed samples and undisturbed soil cores were collected from 0–100 cm soil depths under agricultural land (AL), forestland (FL), and shrub land (SL). Our results showed that the land use and soil depth significantly affected the soil bulk density (BD), field capacity (FC), capillary moisture capacity (CMC), saturated hydraulic conductivity (Ks), and soil water retention curve (θs and α). Small macroaggregates accounted for most of the soil mass and were significantly higher in FL but lower in AL for the 0–50 cm of the soil samples. The FC, CMC, and Ks decreased, but the BD increased with the soil depth across the three land-use types. In addition, the soil in AL had a higher BD but lower CMC and Ks than the soil in FL and SL for most soil depths. These results indicated that land use can influence the variation in soil physical and hydraulic properties within the 0–100 cm soil depth, and agricultural use is a major reason for soil degradation in this black soil region.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Spatial Variation in Soil Physico-Chemical Properties along Slope Position in a Small Agricultural Watershed Scale

Both cropland management and slop erosion are important factors influencing soil properties, but there are relatively few studies on their combined effects. Studies at the agricultural watershed scale can satisfy both of these conditions, and to reduce the effects of soil heterogeneity due to differences in spatial scale, it is better to select different slopes in the same small watershed. To understand how soil properties will respond to the variation of slope position and cropland management at an agricultural watershed, we present the distribution of soil bulk density (BD), saturated hydraulic conductivity (Ks), water-stable aggregates, soil organic carbon (OC), nitrogen (N), and phosphorus (P) at four slope positions in two cropland management systems of a small agricultural watershed in the black soil region of northeast China. The selected four slope positions include upper slope, middle slope, lower slope, and footslope positions. The two cropland management systems consist of a sustainable cropland system (i.e., contour ridge tillage at upper slope position, longitudinal ridge tillage at middle slope and lower slope positions, and grassland at footslope position) and a conventional cropland system (i.e., contour ridge tillage at upper slope position, longitudinal ridge tillage at middle slope, lower slope positions, and footslope positions). The results showed that soil bulk density and microaggregates decreased but the concentration of OC and nutrients, Ks, and small-macroaggregate increased from the upper slope position to the lower slope position in both the conventional and sustainable croplands, which was due to the interaction effect of cultivation with erosion. In comparison with conventional cropland, sustainable cropland has greater Ks, large-macroaggregate, small-macroaggregate, microaggregate, and concentrations and stocks of OC, N, and P, but showed lower bulk density and silt + clay fraction. However, the prominent differences in both croplands were presented in the footslope position, which is ascribed to the interaction of cultivation, erosion, and cropland management. These results highlighted that sustainable cropland management practice has the potential to improve soil structure and prevent soil and nutrient loss

Responses of soil aggregate stability, erodibility and nutrient enrichment to simulated extreme heavy rainfall

Extreme precipitation regime under global change context is estimated to cause heavy rainstorms and longer drought intervals. Temporal variations of soil structure and erosion characteristics during and after heavy rainstorms were less investigated, particularly across a wide soil texture gradient. In this study, 15 soils were selected with clay content ranging in 12.9&ndash;38.2%. Soil erosion characteristics and enrichment ratios of organic carbon (EROC) and nitrogen (ERN) were measured during 3 successive rainfall simulations at slope of 15&deg; and intensity of 120mm h&minus;1. The water-stable aggregate distribution was measured for soils before and after rainfall and drying. The mean weight diameter (MWD) of water-stable aggregate remained unchanged before (1.476 &plusmn; 0.182) and after rainfall and drying (1.406 &plusmn; 0.135 mm), but decreased for soils with higher organic carbon contents. Soil erodibility (K factor) averaged in 0.018 &plusmn; 0.003, 0.011 &plusmn; 0.001 and 0.008 &plusmn; 0.001 in 3 successive rainfall events, with 42% and 27% decreases after each event, respectively (P &lt; 0.05); and the decreases were greater for less aggregated soils or coarser textured soils. Stepwise regression showed that the &lt;0.25 mm water-stable aggregate explained most variations of K and its dynamics. The EROC and ERN were close to 1 and were not correlated with clay content or MWD (P &gt; 0.05). The ERN decreased first and then remained stable, and EROC was unchanged during successive rainfalls. These results indicated that soil texture or aggregation status affected soil erodibility and its temporal changes in successive rainstorms. </p