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Alternaria spores are a common component of the bioaerosol. Many Alternaria species are plant pathogens, and their conidia are catalogued as important aeroallergens. Several aerobiological studies showing a strong relationship between concentrations of airborne spore and meteorological parameters have consequently been developed. However, the Alternaria airborne load variation has not been thoroughly investigated because it is difficult to assess their sources, as they are a very common and widely established phytopathogen. The objective of this study is to estimate the impact of vegetation and land uses as potential sources on airborne spore load and to know their influence, particularly, in cases of long-medium distance transport. The daily airborne spore concentration was studied over a 5-year period in León and Valladolid, two localities of Castilla y León (Spain), with differences in their bioclimatic and land use aspects. Moreover, the land use analysis carried out within a 30 km radius of each monitoring station was combined with air mass data in order to search for potential emission sources. The results showed a great spatial variation between the two areas, which are relatively close to each other. The fact that the spore concentrations recorded in Valladolid were higher than those in León was owing to prevailing winds originating from large areas covered by cereal crops, especially during the harvest period. However, the prevailing winds in León came from areas dominated by forest and shrubland, which explains the low airborne spore load, since the main Alternaria sources were the grasslands located next to the trap. Furthermore, the risk days in this location presented an unusual wind direction. This study reveals the importance of land cover and wind speed and direction data for establishing potential airborne routes of spore transport in order to improve the Alternaria forecasting models. The importance of conducting Alternaria aerobiological studies at a local level is also highlighted. [Display omitted] • There is a great spatial variation in Alternaria airborne load between nearby areas. • The analysis of land use around each trap is crucial to explain spore variation. • High frequencies of low wind speeds from Alternaria sources cause high spore levels. • Cereal crops and grasslands are the most important Alternaria emission sources. • Harvest season with favorable spore transport conditions is the period of greatest risk. [ABSTRACT FROM AUTHOR]

In temperate drylands, livestock grazing and irrigation agriculture alter biocrust cover and thereby soil nitrogen (N) dynamics. However, the influence of land use on biocrusts and soil N dynamics in tropical drylands is unknown. We evaluated the influence of rainfed agriculture and firewood extraction on biocrust functional groups and soil N dynamics in a tropical dryland. We collected biocrusts in abandoned croplands resulting from rainfed agriculture and mesquite shrublands resulting from firewood extraction to measure the cover of heterocystous cyanobacteria, non-heterocystous cyanobacteria, cyanolichens, and chlorolichens. We also collected soil below biocrusts to evaluate soil N dynamics (total and available N, N transformation rates, microbial biomass N), energy availability (total C), and microbial activity (C mineralization). We evaluated the correlation between biocrust functional group cover and soil N dynamics, and between microbial activity and soil N dynamics. In abandoned croplands, heterocystous cyanobacteria had high cover and were associated to altered soil N dynamics. In mesquite shrublands, cyanolichens had high cover and were associated to unaltered soil N dynamics. In this tropical dryland, both activities have contrasting changes in biocrust functional group cover and soil N dynamics, probably due to differences in energy availability and soil microenvironments for microbial activity under biocrusts. • Heterocystous cyanobacteria had high cover values in abandoned croplands. • H. cyanobacteria had low N availability, transformation, and immobilization. • Cyanolichens had high cover values in mesquite shrublands. • Cyanolichens had high N availability, transformation, and immobilization. • H. cyanobacteria favor soil N losses, while cyanolichens favor soil N conservation. [ABSTRACT FROM AUTHOR]

The temporal speeds and spatial scales at which ecosystem processes operate are often at odds with the scale and speed at which natural resources such as soil, water and vegetation are managed those. Scale mismatches often occur as a result of the time-lag between policy development, implementation and observable changes in natural capital in particular. In this study, we analyse some of the transformations that can occur in complex forest-shrubland socio-ecological systems undergoing biophysical and socioeconomic change. We use a Multiway Factor Analysis (MFA) applied to a representative set of variables to assess changes in components of natural, economic and social capitals over time. Our results indicate similarities among variables and spatial units (i.e. municipalities) which allows us to rank the variables used to describe the SES according to their rapidity of change. The novelty of the proposed framework lies in the fact that the assessment of rapidity-to-change, based on the MFA, takes into account the multivariate relationships among the system's variables, identifying the net rate of change for the whole system, and the relative impact that individual variables exert on the system itself. The aim of this study was to assess the influence of fast and slow variables on the evolution of socio-economic systems based on simplified multivariate procedures applicable to vastly different socio-economic contexts and conditions. This study also contributes to quantitative analysis methods for long-established socio-ecological systems, which may help in designing more effective, and sustainable land management strategies in environmentally sensitive areas. [ABSTRACT FROM AUTHOR]

Abstract: Fire and atmospheric N deposition have the capacity to alter the N and C cycling and storage of semi-arid shrublands. Thus, we measured the pre- and post-fire soil and tissue C and N dynamics of three southern California chaparral stands exposed to varying levels of N deposition. Total soil N was positively correlated with N deposition exposure before and after fire, indicating that fire did little to alter patterns of soil N enrichment from atmospheric N deposition. Fire caused a significant increase in soil extractable N, and this increase was positively correlated with N deposition indicating that fire enhanced soil N availability more at sites exposed to high N deposition. Fire also caused the tissue N concentration of regenerating Adenostoma fasciculatum (chamise) shrubs to be significantly correlated with N deposition; however, the correlation was negative during the first year of fire recovery (r 2=0.62) and positive during the second (r 2=0.94) indicating complex and transient dynamics in shrub growth and N concentration. Overall, our results suggest that periodic fire in chaparral may not reduce the potential for N enrichment that develops over decades of N deposition and have important implications for the propensity of these semi-arid shrublands to become “N-saturated”. [Copyright &y& Elsevier]

The degradation of soil resources is accelerating owing to water erosion induced by detrimental land use/land cover (LULC) practices. Although the relationship between affecting factors associated with LULC and soil erosion has been well-documented, a systematic review of LULC for erosion control is lacking. A quantitative synthesis of 1270 runoff and 1302 sediment observations from 79 references covering 57 sites was conducted to assess the effects of LULC on erosion control in the red soil hilly region (RSHR) of southern China. The results indicated that the maximum runoff and soil loss were found in bare land (BL), but the minimum runoff and soil loss were detected in cropland and grassland, respectively. Among the 16 land use subtypes, BL left for natural succession had the highest runoff, but the lowest runoff was found in orchard with contact cover; the soil loss was largest for cropland without conservation measures, while the minimum value was detected in natural shrubland. When the vegetation coverage exceeded 60%, runoff and soil loss both tended to reach a stable rate. Land use with a multi-layer vegetation structure or ground/contact cover or broadleaf plant had less runoff and lower sediment values. In addition, soil loss decreased sharply during the initial 3 y of vegetation restoration, and then slowly declined until reaching a relatively stable rate after 15 y of succession. Our results confirmed that land use (except for BL) has a limited influence on soil erosion provided that suitable land cover is established. This study revealed that sustainable land management measures should be adopted based on local conditions to reduce soil erosion induced by irrational LULC. These findings can serve as a scientific basis for policy makers and land managers with respect to water erosion control in the RSHR. • Effect of land use/cover on water erosion control was evaluated in southern China. • No land use is erosion-prone provided suitable land cover is established. • Soil loss tends to reach a stable rate when the vegetation coverage exceeded 60%. • Low erosion rates were found in land use with multi-layer/ground vegetation cover. • Soil and water loss attained a low level after 15 years' vegetation succession. [ABSTRACT FROM AUTHOR]