Soil erosion modelling of burned and mulched soils following a Mediterranean forest wildfire

Soil erosion modelling applied to burned forests in different global regions can be unreliable because of a lack of verification data. Here, we evaluated the following three erosion models: (1) Water Erosion Prediction Project (WEPP), (2) Morgan-Morgan-Finney (MMF) and (3) Universal Soil Loss Equation-Modified (USLE-M). Using field plots that were either untreated or mulched with straw, this study involved observations of soil loss at the event scale at a burned pine forest in Central Eastern Spain. The erosion predictions of the three models were analysed for goodness-of-fit. Optimization of the MMF model with a new procedure to estimate the C-factor resulted in a satisfactory erosion prediction capacity in burned plots with or without the mulching treatment. The WEPP model underestimated erosion in the unburned areas and largely overestimated the soil loss in burned areas. The accuracy of soil loss estimation by the USLE-M model was also poor. Calibration of the curve numbers and C-factors did not improve the USLE-M model estimation. Therefore, we conclude that an optimized MMF model was the most accurate way to estimate soil loss and recommend this approach for in Mediterranean burned forests with or without postfire mulching. This study gives land managers insight about the choice of the most suitable model for erosion predictions in burned forests.     

Collar insertion depth effects on soil respiration in afforested peatlands

Using collars for measuring soil respiration and its component fluxes in closed chamber systems relies on two main assumptions. Firstly, it is assumed that shallow collars prevent lateral soil gas leakage beneath the chamber’s walls and the underestimation of soil CO₂ fluxes, and secondly, the insertion of deeper collars excises all living roots and the autotrophic flux is eliminated. It was hypothesised that previous findings on collar insertion impacts on autotrophic and total soil respiration also apply to afforested peatlands. In these ecosystems, a large fraction of fine roots grow close to the soil surface. Therefore, the use of shallow collars may sever some fine roots and hyphae of mycorrhizal fungi, and therefore, it may lead to underestimation of total soil respiration. It was also hypothesised that this underestimation may be greater than a possible CO₂ leakage from lateral diffusion of soil gas as a result of not using collars. In this study, we measured soil CO₂ efflux in a Sitka spruce and a lodgepole pine plantation on blanket peat in southern Ireland. A surface collar (not inserted into the ground) and six insertion depths (5, 10, 15, 25, 35 and 45 cm) were established to assess the effect of the collar insertion depth on autotrophic and total soil respiration. The insertion depth of 5 cm reduced total soil respiration by 47 and 32% in the spruce and pine stands, respectively. Using nonlinear equations, it was estimated that a frequently used shallow insertion of 1.5 cm would have reduced this efflux by 35 and 20% in each stand, respectively. Moreover, it was demonstrated that this reduction was greater than a possible lateral soil gas leakage. These results suggest that the insertion of shallow collars should be avoided and surface collars permanently anchored in the soil should be used instead.     

Soil Enzymatic Activity in Eucalyptus Grandis Plantations of Different Ages

Eucalyptus plantations have become increasingly common in Latin America. However, because Eucalyptus is an exotic species, its presence has raised concerns about changes in the environment, especially to soil properties. The objective of this study was to investigate possible changes in selected soil enzyme activity after several years of Eucalyptus cultivation. Soil samples were collected from four locations: a native forest (Atlantic Forest) used as a reference for the original soil conditions and three E. grandis plantations aged 2, 3 and 5 years, established in 2008, 2007 and 2005, respectively. The native vegetation had been removed and the soil graded and ploughed to establish these plantations. We evaluated soil enzymatic activities (β‐glucosidase, acid phosphatase, dehydrogenase, urease and arylsulfatase) at each location. The activity of β‐glucosidase, phosphatase, dehydrogenase and urease was improved after 5 years, whereas arylsulphatase was impacted negatively. The multivariate analysis showed that the majority of enzyme activities reached the values observed in native forest after the third year of reforestation. The activity of β‐glucosidase was crucial in differentiating the area with 2 years of reforestation from the native forest. The removal of native vegetation in order to establish commercial plantations raises concerns about the real impacts of this practice on the soil. In the present study, plantations of Eucalyptus improved most of the selected enzyme activities after the third year of reforestation. Copyright © 2015 John Wiley & Sons, Ltd.     

Genetic heterogeneity of wild-type G4P[6] porcine rotavirus strains detected in a diarrhea outbreak in a regularly vaccinated pig herd

Group A rotavirus (RV-A) with short electropherotype was identified by ss-PAGE in a neonatal diarrhea outbreak at a Brazilian pig farm where the sows were regularly vaccinated with a commercial vaccine containing OSU (G5P[7]) and Gottfried (G4P[6]) porcine RV-A (PoRV-A) strains. The ss-PAGE positive stool samples (n=20) were characterized as P[6] genotype by multiplex-nested-RT-PCR assay. The nucleotide analysis of the VP4 gene (VP8*) state that the viruses clustered in P[6] lineages that are also shared by RV-A strains identified in human hosts. Nucleotide analysis of the VP7 gene identified different lineages in G4 including a new lineage tentatively designated IX. The immunological pressure induced by commercial vaccine with a rotavirus containing a G4P[6] genotype of porcine origin (Gottfried strain) might have allowed the selection of PoRV-A strains with characteristics found in RV-A strains isolated of human hosts, such as P[6]-Ie and If, and promoted the selection or emergence of RV-A strains with a new lineage of the G4 genotype. The characterization of PoRV-A strains with unusual genotypes described in this study highlight the importance of surveys on the relationship between human and animal rotavirus strains.     

Salt stress alters the morphoanatomy and primary and secondary metabolites of the leaves and rhizomes of Curcuma longa L.

Journal of Crop Science and Biotechnology - During cultivation, environmental factors can cause changes in the metabolism of Curcuma longa L. that limit its development. This study evaluated the...