Pine wilt disease (PWD) is a devastating forest disease that severely impacts pine trees, with widespread outbreaks leading to catastrophic damage in pine forests worldwide. Our study aims to investigate the dynamics of PWD infection on soil physicochemical properties and biological activities, as well as the interrelationships between them. Soil samples were collected from 0 to 10 cm and 10 to 20 cm depths in subtropical Pinus massoniana (Masson pine) forests with PWD infection years of 0 (non-infection), 6, 10, and 16 years. The physicochemical properties, microbial biomass, and enzymatic activities of these soil samples were measured. The results revealed that soil non-capillary porosity, clay, microbial biomass carbon and microbial biomass nitrogen decreased significantly in 6 years forests. Available potassium consistently decreased with longer invasion periods, while soil polyphenol oxidase, leucine amino peptidase, and available phosphorous peaked in 6 years forests and then declined over time. The soil physicochemical properties, biological activities all decreased as soil depth increased. Redundancy analysis and Mantel tests underscored the critical role of Total potassium, pH, Total phosphorous, and bulk density in shaping microbial activities. This study demonstrated that PWD infection significantly effect on soil physicochemical properties, microbial biomass, and enzymatic activities with the chronosequence progresses. These finding contribute to a deeper understanding of how invasive pathogens like PWD can reshape soil environments, with implications for forest conservation and restoration practices.

Salinity is recognized as a significant abiotic stressor that impairs crop growth and productivity. Elevated- soil and irrigation water salinity poses substantial ecological challenges for agriculture, particularly in semiarid and arid regions. High sodium (Na+) concentrations induce osmotic stress, leading to water deficits within plant cells. However, using nanoparticles can mitigate salt stress and enhance plant growth. This study investigates the effects of selenium nanoparticles on the physiobiochemical characteristics of Citrus limon L. seedlings under salt stress. Selenium nanoparticles act as both reducing and capping agents. Six-month-old lemon seedlings were subjected to varying salinity levels (100 mM and 200 mM NaCl) and treated with foliar applications of selenium nanoparticles at- 25 mg/L and 50 mg/L concentration. Most of the nano- structures were observed in the size range of 20-40 nm and anisotropic and irregular in shape. The results indicated that 200 mM NaCl significantly reduced the morphological and physiobiochemical parameters of the seedlings. However, a 50 mg/L concentration of SeNPs notably improved fresh and dry weights of roots and shoots and increased chlorophyll content. Biochemical attributes such as SOD, POD, CAT, APX, TSS, TFA, Proline, H2O2, and MDA were elevated under 200 mM NaCl, while NPK levels decreased. A concentration of 50 mg/L SeNPs was identified as optimal for enhancing the morphological and physiobiochemical parameters of C . limon seedlings under salt stress.

Although several management options are adopted to redirect post-fire forest ecosystems towards less vulnerable and more resilient and functional communities, little is known about the interactions among tree stand age, prefire forest management, and slope aspects, and their consequences for plant species and soil properties recovery immediately after severe wildfires. To address this knowledge need, this study evaluates the post-fire changes in species richness and diversity (with a specific focus on regeneration mechanisms and life forms) of regenerating plants as well as the main physico-chemical and biological properties of burned soils with the reciprocal relations. Plant cover and diversity, and many soil properties have been monitored in forests of southeast Spain with mature, middle and young stands, presence of pre-fire treatments or not, and north and south hillslopes about one year after the fire. To this aim, the reciprocal relationships among soil properties and plants were evaluated adopting a combination of statistical techniques (PERMANOVA, Non-metric Multi-Dimensional Scaling, Distance-based Linear Modelling, Distance-based Redundancy Analysis, and Spearman correlation analysis). The damage to soil and vegetation was so high that both plants and pre-fire soil properties slowly recovered. Only a few life forms of vegetation (geophytes and herbaceous chamaephytes) were influenced by the stand age. If combined with soil aspect, stand age resulted in significantly lower germinating species in mature stands and lower resprouters in young stands, both on south hillslopes. Plant diversity was high, and the post-fire regeneration did not change the species richness and evenness. The post-fire changes in soil properties were limited, and only slight small differences in pH and betaglucosidase among stands of different age were found. No evident associations between soil properties and plant diversity were revealed by the low correlation coefficient. The low variance in plant cover and diversity, as well as in soil properties, resulted in a low accuracy of the dbRDA model to reproduce its variability among sites with different pre-fire characteristics.

Permafrost degradation by global warming is expected to alter the hydrological processes, which results in changes in vegetation species composition and gives rise to community succession. Ecotones are sensitive transition areas between ecosystem boundaries, attract particular interest due to their ecological importance and prompt responses to the environmental variables. However, the characteristics of soil microbial communities and extracellular enzymes along the forest-wetland ecotone in high-latitude permafrost region remain poorly understood. In this study, we evaluated the variations of soil bacterial and fungal community structures and soil extracellular enzymatic activities of 0-10 cm and 10-20 cm soil layers in five different wetland types along environmental gradients, including Larix gmelinii swamp (LY), Betula platyphylla swamp (BH), Alnus sibirica var. hirsute swamp (MCY), thicket swamp (GC), and tussock swamp (CC). The relative abundances of some dominant bacterial (Actinobacteria and Verrucomicrobia) and fungal (Ascomycota and Basidiomycota) phyla differed significantly among different wetlands, while bacterial and fungal alpha diversity was not strongly affected by soil depth. PCoA results showed that vegetation type, rather than soil depth explained more variation of soil microbial community structure. beta-glucosidase and beta-N-acetylglucosaminidase activities were significantly lower in GC and CC than in LY, BH, and MCY, while acid phosphatase activity was significantly higher in BH and GC than LY and CC. Altogether, the data suggest that soil moisture content (SMC) was the most important environmental factor contributing to the bacterial and fungal communities, while extracellular enzymatic activities were closely related to soil total organic carbon (TOC), nitrate nitrogen (NO3--N) and total phosphorus (TP).