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Introduction: Extreme environments such as prolonged high temperatures and droughts can cause vulnerability of vegetation ecosystems. The dry-hot valleys of Southwestern China, known for their extremely high annual temperature, lack of water, and unique non-zonal "hot island" habitat in the global temperate zone, provide exceptional sites for studying how plant adapts to the prolonged dry and hot environment. However, the specific local biotic-environment relationships in these regions remain incompletely elucidated. The study aims to evaluate how valley-type Savanna vegetation species and their communities adapt to long-term drought and high-temperature stress environments. Methods: The study investigated the changes in species diversity and communities' aboveground biomass of a valley-type Savanna vegetation along an elevation gradient of Yuanmou dry-hot valley in Jinsha River basin, southwest China. Subsequently, a general linear model was utilized to simulate the distribution pattern of species diversities and their constituent biomass along the elevation gradient. Finally, the RDA and VPH mothed were used to evaluate the impacts and contributions of environmental factors or variables on the patterns. Results and discussion: The field survey reveals an altitudinal gradient effect on the valley-type Savanna, with a dominant species of shrubs and herbs plants distribution below an elevation of 1700m, and a significant positive relationship between the SR, Shannon-Wiener, Simpson, and Pielou indices and altitudes. Relatively, the community aboveground biomass did not increase significantly with elevation, which was mainly due to a decreased biomass of herbaceous plants along the elevation. Different regulators of shrub-herbaceous plant species and their functional groups made different elevation patterns of species diversity and aboveground biomass in valley-type Savannas. Herbaceous plants are responsible for maintaining species diversity and ensuring stability in the aboveground biomass of the vegetation. However, the influence of shrubs on aboveground biomass became more pronounced as environmental conditions varied along the altitudinal gradient. Furthermore, species diversity was mainly influenced by soil and climatic environmental factors, whereas community biomass was mainly regulated by plant species or functional groups. The study demonstrates that the spatial pattern of valley-type Savanna was formed as a result of different environmental responses and the productive capacity of retained plant species or functional groups to climate-soil factors, highlighting the value of the Yuanmou dry-hot Valley as a microcosm for exploring the intricate interactions between vegetation evolution and changes in environmental factors.
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The valleyes of Hengduan Mountains contain the landscapes with high heterogeneity as well as high diversity of climate and vegetation types. To explore the soil cycling of four elements (C, N, P, S) across the parallel valleys of Nujiang River, Lancang River, Jinsha River and Yuanjiang River in western Yunnan, we collected top soils (0-10 cm) in forests, grasslands, and croplands. The activities of soil enzymes, including ß-glucosidase (BG), ß-N-acetylglucosaminidase (NAG), acid phosphatase (AP), and sulfatase (SU), which drive the soil C, N, P and S cycling, were determined. We analyzed the relationships of soil enzymatic activities and their stoichiometric characteristics with environmental factors. The activities of both AP and NAG had significant difference among different basins and different land types. The activities of AP, BG, NAG and SU were significantly positively related with each other. From southeast to northwest, the activities of BG, NAG, and SU increased with the altitude. Across all basins, the ecoenzymatic ratios of soils always ranked as AP:SU > BG:SU > NAG:SU > BG:NAG > BG:AP > NAG:AP. Compared with forest and grassland soil, cropland soils in each watershed had a higher BG:NAG and a lower NAG:AP (except Yuanjiang River basin). Moreover, AP:SU, BG:SU and NAG:SU of cropland soils were lower than those of forest and grassland in Yuanjiang River basin. However, they were higher than forest and lower than grassland in both Lancang River basin and Jinsha River basin. Soil enzyme activities and enzymatic stoichiometry were affected by physicochemical properties of soil, climate, and location, with the most contribution from soil physicochemical properties. Agricultural land use significantly affected the stoichiometry of C:N:P acquiring enzymes in soils by reducing the activity of N-degrading enzymes relative, resulting in the increases of BG:NAG and the decreases of NAG:AP. Agricultural activities had limited effects on other enzymatic stoichiometries.
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Nitrógeno , Suelo , China , Bosques , Nitrógeno/análisis , Microbiología del SueloRESUMEN
BACKGROUND: Chinese bayberry (Myrica rubra) is a subtropical fruit crop widely grown in southern China. Twig dieback is a disease of Chinese bayberry caused by Pestalotiopsis spp. and results in great economic losses to Chinese bayberry production. A virus survey was conducted in the population of Pestalotiopsis spp. infecting M. rubra in China. We explored the viral diversity in Pestalotiopsis spp., which may provide resources for further development as biocontrol agents of twig dieback. METHODS: Strains of Pestalotiopsis spp. were isolated from diseased twigs of M. rubra, and cultured on potato dextrose agar for RNA extraction. The total RNA of each strain was extracted, mixed, and used for RNA sequencing. The resulting sequences were deduplicated, annotated, and then used for phylogenetic analysis. RESULTS: Seven novel viruses were characterized from 59 isolates of M. rubra collected from 14 localities in China. Based on the phylogenetic analysis, these viruses were classified into five viral families/orders, Botourmiaviridae, Mitoviridae, Partitiviridae, Tymovirales and Bunyavirales, and one virus, Pestalotiopsis negative-stranded RNA virus 1, which likely belongs to a new viral family. CONCLUSIONS: Metatranscriptomics analysis showed the presence of various mycoviruses in Pestalotiopsis spp. isolated from M. rubra in China. The genomes of eight putative viruses were identified, seven of which were nearly full-length. Some of these viruses of Pestalotiopsis spp. may have the potential for the biological control of twig dieback of M. rubra.
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Virus Fúngicos/clasificación , Virus Fúngicos/genética , Myrica/microbiología , Pestalotiopsis/virología , Agentes de Control Biológico , China , Frutas/microbiología , Virus Fúngicos/aislamiento & purificación , Variación Genética , Filogenia , Análisis de Secuencia de ARN , TranscriptomaRESUMEN
Biomass allocation can exert a great influence on plant resource acquisition and nutrient use. However, the role of biomass allocation strategies in shaping plant community composition under nutrient limitations remains poorly addressed. We hypothesized that species-specific allocation strategies can affect plant adaptation to nutrient limitations, resulting in species turnover and changes in community-level biomass allocations across nutrient gradients. In this study, we measured species abundance and the concentrations of nitrogen and phosphorus in leaves and soil nutrients in an arid-hot grassland. We quantified species-specific allocation parameters for stems vs leaves based on allometric scaling relationships. Species-specific stem vs leaf allocation parameters were weighted with species abundances to calculate the community-weighted means driven by species turnover. We found that the community-weighted means of biomass allocation parameters were significantly related to the soil nutrient gradient as well as to leaf stoichiometry, indicating that species-specific allocation strategies can affect plant adaptation to nutrient limitations in the studied grassland. Species that allocate less to stems than leaves tend to dominate nutrient-limited environments. The results support the hypothesis that species-specific allocations affect plant adaptation to nutrient limitations. The allocation trade-off between stems and leaves has the potential to greatly affect plant distribution across nutrient gradients.
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Adaptación Fisiológica , Biomasa , Pradera , Calor , Nitrógeno/deficiencia , Fósforo/deficiencia , Tallos de la Planta/fisiología , Hojas de la Planta/fisiología , Análisis de Componente Principal , Análisis de Regresión , Suelo/químicaRESUMEN
BACKGROUND: Heteropogon contortus is a valuable pasture species that is widely used for vegetation restoration in dry-hot valleys of China. However, to date, its morphological and physiological responses to drought, and the underlying mechanisms are not well understood. This study was aimed to investigate the morphological and physiological changes of H. contortus under drought stress during the dry-hot season. Heteropogon contortus was planted in pots and subjected to four levels of soil water treatments: above 85 % (control), 70-75 % (light stress), 55-60 % (moderate stress) or 35-40 % (severe stress) of field capacity. RESULTS: Within the total stress period (0-29 days), H. contortus grew rapidly in the light stress, whereas severe stress had a negative impact on growth. Aboveground biomass decreased together with increasing drought stress, whereas root biomass increased. Consequently, the root/shoot ratio of the severe stress treatment increased by 80 % compared to that of the control treatment. The ratio of bound water/free water (BW/FW) was the most sensitive parameter to drought and showed a value under severe stress that was 152.83 % more than that in the control treatment. Although leaf water potential (LWP) and leaf relative water content (RWC) decreased with progressive water stress, H. contortus managed to maintain a relatively high RWC (nearly 70 %) in the severe stress condition. We also detected a significant reduction (below 0.6) in the ratio of variable fluorescence/maximum fluorescence (Fv/Fm) in the severe stress treatment. CONCLUSIONS: Our results show that H. contortus adapts to drought mainly by avoidance mechanisms, and its morphological and physiological characteristics are inhibited under severe stress, but can recover at a certain time after re-watering. These findings might help limited water resources to be fully used for vegetation management in the studied region.
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Taking the arid-hot valley of Jinsha River, Southwest China as the object, a comparative study was made on the plant leaf N, P, and K concentrations and ratios as well as their relationships with species dominance in the restoration area and disturbed area, aimed to understand the effects of ecosystem restoration on the plant leaf stoichoimetric characteristics. Ecosystem restoration decreased the plant leaf N and P concentrations and P/K ratio significantly, but had lesser effects on the plant leaf K concentration. In restoration area, the plant leaf N, P, and K concentrations were averagely 10. 405, 0. 604, and 9. 619 g kg-1, being 16. 9% , 34. 9% , and 4. 7% lower than those in disturbed area, respectively. In restoration area, species dominance was significantly negatively correlated with plant leaf P concentration; while the species dominance in disturbed area had a significant negative correlation with plant leaf K concentration. Ecosystem restoration altered the slope and intercept of the scaling relationships among the plant leaf N, P, and K. No significant differences were observed in the leaf N, P, and K concentrations of the same plant species between restoration area and disturbed area, suggesting that the changes of plant leaf stoichiometric characteristics were mainly driven by the shift of species composition in the plant community.
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Conservación de los Recursos Naturales , Ecosistema , Nitrógeno/análisis , Fósforo/análisis , Hojas de la Planta/química , Potasio/análisis , China , Restauración y Remediación Ambiental , Calor , Desarrollo de la Planta , Especificidad de la EspecieRESUMEN
In order to understand the variations of soil faunal diversity under different natural alpine vegetations in West Sichuan, an investigation was made on the soil faunal communities under alpine coniferous forest, shrub, and meadow from August 2008 to June 2009. A total of 48343 individuals were collected, belonging to 7 phyla, 16 classes, 31 orders and 117 families. There was a great difference in the dominant groups of soil macro-fauna, and a significant difference (P < 0.05) in the number of soil faunal groups under different vegetations. Both the individual density and the group number of soil fauna decreased obviously with increasing soil depth, and were significantly higher (P < 0.01) in moss layer than in litter layer in coniferous forest. Significant difference (P < 0.01) was also observed in the density-group index among the three vegetations. The maximum biomass of soil macro-fauna was found in June. Jacard indices indicated that disturbed meadow had the lowest similarity of soil faunal community with the other vegetations. It was suggested that vegetation type had significant effects on the community structure of soil fauna, while aspect, altitude, and disturbance also had definite effects.