Fu Sun Shi

Root rot disease is a significant constraint to sweet cherry production in the highlands of southwest China, causing substantial yield losses. While the disease is prevalent, the complex interplay of climate, topography, soil, and management practices on its development remains poorly understood. To address this knowledge gap, a field survey encompassing 95 field sites was conducted to assess disease incidence (DI) and canopy damage index (_CDI). Our results showed that the average DI and _CDI were 27.04 and 20.52%, respectively. DI and _CDI were influenced by management practices: they both increased with the number of planting years and were lower with Cerasus szechuanica rootstock and composted animal manures compared with Da-qingye rootstock and uncomposted animal manures. Climatic and topographic factors also played an important role in observing higher DI at higher altitudes and shady slopes (P < 0.05). Moreover, both DI and _CDI demonstrated positive correlations with the aridity index and sunshine duration and negative correlations with mean annual temperature and mean annual precipitation (P < 0.05). Soil properties, including moisture content, bulk density, pH, and sand content, were positively associated with DI and _CDI, while clay content and available potassium exhibited negative correlation. The present study emphasizes the combined impact of multiple factors on root rot disease in sweet cherry, with management practices and soil properties having a more decisive effect than climate and topography. These findings provide crucial insights for developing effective disease management strategies.

Reforestation plays a vital role in restoring the soil degradation areas. However, the mechanisms by which different restoration approaches affect the soil properties and microbial communities remain unclear. Aiming to understand the interactions between plant species, soil properties, and microbial communities in different restoration approaches, we investigated the soil microbial community using nontargeted metabolomics to explore how the reforestation approach affects soil physicochemical properties, soil metabolites, and soil microbial communities. The results showed that the reforestation approach, soil layer, and their interactive effects significantly affected soil organic carbon, total nitrogen, dissolved organic carbon, available phosphorus concentrations, and root traits. The diversity and composition of bacterial and fungal communities in natural reforestation (NR) were different from those in artificial mono-plantations, and their network interactions were more significant in NR than in artificial plantations. A clear separation of metabolites between the artificial plantations and NR was observed in the soil metabolite analysis. Two pathways, linoleic acid metabolism, and valine, leucine, and isoleucine biosynthesis, were significantly regulated between the artificial mono-plantations and NR. Different soil traits were significantly correlated with dominant microbial taxa in the four reforestation approaches. 13-L-hydroperoxylinoleic acid, 13-S-hydroxyoctadecadienoic acid, homovanillin, and 9,10-epoxyoctadecenoic acid showed the highest correlation with the microbial taxa in the network. Partial least squares path modeling (PLS-PM) shows that root-mediated soil physicochemical properties were the primary factors affecting the bacterial community among the reforestation approaches. The soil fungal community is directly regulated by plant roots in the subsoil and indirectly regulated by the root-mediated physicochemical properties in the topsoil. We conclude that different reforestation approaches affect the soil microbial community through root and soil physicochemical properties rather than soil metabolites.

Sweet cherry (Prunus avium L.) has become an economically important fruit in China. And its cultivation area has significantly expanded over the last three decades (Wang et al. 2020; Zhao et al. 20...

Root-rot disease has lead to serious reduction in yields and jeopardized the survival of the economically and ecologically important Zanthoxylum bungeanum trees cultured in Sichuan Province. In order to investigate the interaction between the microbiome and the root-rot disease, a metagenomic analysis was performed to characterize the microbial communities and functions in Z. bungeanum root endosphere, rhizosphere and bulk soil with/without root-rot disease. Soil physicochemical properties, microbial population size and enzyme activities were also analyzed for finding their interactions with the root-rot disease. As results, lower total nitrogen (TN) and available phosphorus (AP) contents but higher pH in rhizosphere and bulk soil, as well as lower substrate-induced respiration (SIR) and higher protease activity in bulk soil of diseased trees were found, in comparison with that of healthy trees. Microbial diversity and community composition were changed by root-rot disease in the endosphere, but not in rhizosphere and bulk soils. The endophytic microbiome of diseased trees presented higher Proteobacteria abundance and lower abundances of Bacteroidetes, Firmicutes and dominant fungal phyla. The relative abundances of nitrogen cycle- and carbon cycle-related genes in endophytic microbiomes were different between the diseased and healthy trees. Based on ANOSIM and PCoA, functional profiles (KEGG and CAZy) of microbiomes in rhizosphere and bulk soil shifted significantly between the diseased and healthy trees. In addition, soil pH, TN, AP, SIR, invertase and protease were estimated as the main factors influencing the shifts of taxonomic and functional groups in microbiomes of rhizosphere and bulk soil. Conclusively, the imbalance of root and soil microbial function groups might lead to shifts in the root endosphere-rhizosphere microenvironment, which in turn resulted in Z. bungeanum root-rot.

The aim of this study was to evaluate the relationships among changes in the soil microstructure, soil physicochemical traits and microbial communities during desertification. Soil samples were collected from grasslands at different stages of desertification, from an area of the Tibetan Plateau. Soil aggregate fractionation and soil physicochemical properties were analysed using standard methods, and the abundance and diversity of bacteria associated with different aggregate fractions were estimated by quantitative PCR and Illumina Miseq amplicon sequencing . Sequential changes in response to desertification stages were detected in the analysed features. For instance, soil nutrients, microbial biomass C and N, water content and pH initially changed during the light desertification stage; then, the soil aggregation decreased during the intermediate stages; and finally, bacterial abundance and diversity decreased during heavy and severe desertification stages. During grassland desertification, vegetation coverage positively influenced soil aggregation by affecting soil properties (e.g., pH and SOC), whereas bacterial communities in FMi (free microaggregates) and FSC (free silt and clay) were negatively related to soil aggregation. This study reports novel information concerning the desertification process and the sequential modification of soil traits and interactions among soil physical properties (aggregate composition), soil nutrients and the soil microbial community in the grasslands of the Tibetan Plateau. Highlights: Bacterial community was more sensitive in macroaggregates than in microaggregates. Composition of small macroaggregates and associated bacteria changed during desertification. Bacterial community in microaggregates, silt and clay negatively affected aggregation. Vegetation coverage affected aggregation by changing soil traits and bacterial community.

Soil microbial activity varies seasonally in frozen alpine soils during cold seasons and plays a crucial role in available N pool accumulation in soil. The intra- and interannual patterns of microbial and nutrient dynamics reflect the influences of changing weather factors, and thus provide important insights into the biogeochemical cycles and ecological functions of ecosystems. We documented the seasonal and interannual dynamics of soil microbial and available N in an alpine meadow in the eastern part of Qinghai–Tibet Plateau, China, between April 2011 and October 2013. Soil was collected in the middle of each month and analyzed for water content, microbial biomass C (MBC) and N (MBN), dissolved organic C and N, and inorganic N. Soil microbial community composition was measured by the dilution-plate method. Fungi and actinomycetes dominated the microbial community during the nongrowing seasons, and the proportion of bacteria increased considerably during the early growing seasons. Trends of consistently increasing MBC and available N pools were observed during the nongrowing seasons. MBC sharply declined during soil thaw and was accompanied by a peak in available N pool. Induced by changes in soil temperatures, significant shifts in the structures and functions of microbial communities were observed during the winter–spring transition and largely contributed to microbial reduction. The divergent seasonal dynamics of different N forms showed a complementary nutrient supply pattern during the growing season. Similarities between the interannual dynamics of microbial biomass and available N pools were observed, and soil temperature and water conditions were the primary environmental factors driving interannual fluctuations. Owing to the changes in climate, seasonal soil microbial activities and nutrient supply patterns are expected to change further, and these changes may have crucial implications for the productivity and biodiversity of alpine ecosystems.

Soil microbial activity occurs seasonally in frozen alpine soils during cold seasons and plays a crucial role in available N pool accumulation in soil. The intra- and interannual patterns of microbial and nutrient dynamics reflect the influences of changing weather factors, and thus provide important insights into the biogeochemical cycles and ecological functions of ecosystems. We documented seasonal and interannual dynamics of soil microbial and available N in an alpine meadow in the eastern part of Qinghai-Tibet Plateau, China between April 2011 and October 2013. Soil samples were collected in the middle of each month and were analyzed for water content, microbial biomass C (MBC) and N, dissolved organic C and N, and inorganic N; soil microbial community compositions were measured by the dilution-plate method. Fungi and actinomycetes dominated the microbial community during the non-growing seasons, and the number of bacteria increased considerably during the early growing seasons. Consistently increasing trends of MBC and available N pools were observed during the non-growing seasons. MBC sharply declined during soil thaw and was accompanied by a peak of available N pool. Induced by soil temperatures, significant shifts in the structure and functions of microbial communities were found during the winter-spring transition and largely contributed to microbial reduction. Divergent seasonal dynamics of different N forms showed a complementary nutrient supply pattern during the growing season. Similar interannual dynamics were observed between microbial biomass and available N pools, and soil temperature and water condition were the primary environmental factors driving these year-to-year fluctuations. Under the background of changing climate, the seasonal soil microbial activity and nutrient supply patterns will be further changed, having important implications to the productivity and biodiversity of alpine ecosystems.

Litters of reproductive organs have rarely been studied despite their role in allocating nutrients for offspring reproduction. This study determines the mechanism through which flower litters efficiently increase the available soil nutrient pool. Field experiments were conducted to collect plant litters and calculate biomass production in an alpine meadow of the eastern Tibetan Plateau. C, N, P, lignin, cellulose content, and their relevant ratios of litters were analyzed to identify their decomposition features. A pot experiment was performed to determine the effects of litter addition on the soil nutrition pool by comparing the treated and control samples. The litter-bag method was used to verify decomposition rates. The flower litters of phanerophyte plants were comparable with non-flower litters. Biomass partitioning of other herbaceous species accounted for 10–40 % of the aboveground biomass. Flower litter possessed significantly higher N and P levels but less C ∕ N, N ∕ P, lignin ∕ N, and lignin and cellulose concentrations than leaf litter. The litter-bag experiment confirmed that the flower litters of Rhododendron przewalskii and Meconopsis integrifolia decompose approximately 3 times faster than mixed litters within 50 days. Pot experiment findings indicated that flower litter addition significantly increased the available nutrient pool and soil microbial productivity. The time of litter fall significantly influenced soil available N and P, and soil microbial biomass. Flower litters fed the soil nutrition pool and influenced nutrition cycling in alpine ecosystems more efficiently because of their non-ignorable production, faster decomposition rate, and higher nutrient contents compared with non-flower litters. The underlying mechanism can enrich nutrients, which return to the soil, and non-structural carbohydrates, which feed and enhance the transitions of soil microorganisms.