Understanding the spatial distributions and corresponding variation mechanisms of key soil nutrients in fragile karst ecosystems can assist in promoting sustainable development.  However, due to the implementation of ecological restoration initiatives such as land-use conversions, novel changes in the spatial characteristics of soil nutrients remain unknown.  To address this gap, we explored nutrient variations and the drivers of the variation in the 0–15 cm topsoil layer using a regional-scale sampling method in a typical karst area in northwest Guangxi Zhuang Autonomous Region, Southwest China.  Descriptive statistics, geostatistics, and spatial analysis were used to assess the soil nutrient variability.  The results indicated that soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and total potassium (TK) concentrations showed moderate variations, with coefficients of variance being 0.60, 0.60, 0.71, and 0.72, respectively.  Moreover, they demonstrated positive spatial autocorrelations, with global Moran’s indices being 0.68, 0.77, 0.64, and 0.68, respectively.  However, local Moran’s index values were low, indicating large spatial variations in soil nutrients.  The best-fitting semi-variogram models for SOC, TN, TP, and TK concentrations were spherical, Gaussian, exponential, and exponential, respectively.  According to the classification criteria of the Second National Soil Census in China, SOC and TN concentrations were relatively sufficient, with the proportions of rich and very rich levels being up to 90.9 and 96.0%, respectively.  TP concentration was in the medium-deficient level, with the areas of medium and deficient levels accounting for 33.7 and 30.1% of the total, respectively.  TK concentration was deficient, with the cumulative area of extremely deficient, very deficient, and deficient levels accounting for 87.6% of the total area.  Consequently, the terrestrial ecosystems in the study area were more vulnerable to soil P and K than soil N deficiencies.  Furthermore, variance partitioning analysis of the influencing factors showed that, except for the interactions, the single effect of other soil properties accounted more for soil nutrient variations than spatial and environmental variables.  These results will aid in the future management of terrestrial ecosystems.

The velvet protein family serves as a crucial factor in coordinating development and secondary metabolism in numerous pathogenic fungi.  However, no previous research has examined the function of the velvet protein family in Fusarium oxysporum f. sp. niveum (FON), a pathogen causing a highly destructive disease in watermelon.  In this study, ∆fovel1 and ∆folae1 deletion mutants and ∆fovel1-C and ∆folae1-C corresponding complementation mutants of FON were validated.  Additionally, the phenotypic, biochemical, and virulence effects of the deletion mutants were investigated.  Compared to the wild-type strains, the ∆fovel1 and ∆folae1 mutants exhibited altered mycelial phenotype, reduced conidiation, and decreased production of bikaverin and fusaric acid.  Furthermore, their virulence on watermelon plant roots significantly decreased.  All these alterations in mutants were restored in corresponding complementation strains.  Notably, yeast two-hybrid results demonstrated an interaction between FoVel1 and FoLae1.  This study reveals that FoVEL1 and FoLAE1 play essential roles in secondary metabolism, conidiation, and virulence in FON.  These findings enhance our understanding of the genetic and functional roles of VEL1 and LAE1 in pathogenic fungi.