Relative Contribution Of Vegetation Research Articles

Plant Biomass and Soil Nutrients Mainly Explain the Variation of Soil Microbial Communities During Secondary Succession on the Loess Plateau.

Soil microorganisms play an important role in the circulation of materials and nutrients between plants and soil ecosystems, but the drivers of microbial community composition and diversity remain uncertain in different vegetation restoration patterns. We studied soil physicochemical properties (i.e., soil moisture, bulk density, pH, soil nutrients, available nutrients), plant characteristics (i.e., Shannon index [HPlant] and Richness index [SPlant], litter biomass [LB], and fine root biomass [FRB]), and microbial variables (biomass, enzyme activity, diversity, and composition of bacterial and fungal communities) in different plant succession patterns (Robinia pseudoacacia [MF], Caragana korshinskii [SF], and grassland [GL]) on the Loess Plateau. The herb communities, soil microbial biomass, and enzyme activities were strongly affected by vegetation restoration, and soil bacterial and fungal communities were significantly different from each other at the sites. Correlation analysis showed that LB and FRB were significantly positively correlated with the Chao index of soil bacteria, soil microbial biomass, enzyme activities, Proteobacteria, Zygomycota, and Cercozoa, while negatively correlated with Actinobacteria and Basidiomycota. In addition, soil water content (SW), pH, and nutrients have important effects on the bacterial and fungal diversities, as well as Acidobacteria, Proteobacteria, Actinobacteria, Nitrospirae, Zygomycota, and microbial biomass. Furthermore, plant characteristics and soil properties modulated the composition and diversity of soil microorganisms, respectively. Overall, the relative contribution of vegetation and soil to the diversity and composition of soil bacterial and fungal communities illustrated that plant characteristics and soil properties may synergistically modulate soil microbial communities, and the composition and diversity of soil bacterial and fungal communities mainly depend on plant biomass and soil nutrients.

Soil pH and nutrients shape the vertical distribution of microbial communities in an alpine wetland

Soil microbial communities are vital for maintaining functions of alpine wetland ecosystems, which have been shown to be sensitive to climate change and anthropogenic disturbances in recent decades. The diversity and community structure of soil bacteria and fungi are often highly heterogeneous across vegetation types and soil layers. However, the relative contributions of vegetation, soil properties, and spatial structure to variation in the microbial community remain unclear. Here, we studied the linkage between plant functional groups, soil water content, pH as well as nutrient contents and soil microbial diversity and communities in different soil layers (0–20 cm and 20–40 cm) in Lalu Wetland on the Tibetan Plateau. Plant and soil samples from eighteen plots of six sites were collected to determine the community structure of bacteria and fungi, plant functional groups, and soil characteristics. Our results showed that bacterial and fungal diversity at the 0–20 cm soil depth were significantly negatively (Shannon index, r = −0.65, P < 0.01) and positively (phylogenetic diversity, r = 0.72, P < 0.001) related to pH, respectively. Soil ammonium content was positively correlated with bacterial diversity at the 20–40 cm soil layer (Shannon index: r = 0.55, P < 0.05). Bacterial community structure was most significantly related to soil organic carbon. Fungal diversity and community structure were significantly related to soil organic carbon, available phosphorus, and available potassium. Spatial structure explained 30–50% of the variation in bacterial and fungal community structures in different soil layers in Lalu wetland. In conclusion, pH and soil nutrients were the main factors driving variation in microbial diversity and community structure in the upper and deeper soil layers, respectively. Spatial structure contributed more than vegetation and soil characteristics to explaining variation in bacterial and fungal community structures in both upper and deeper soil layers.

Plant biomass and soil organic carbon are main factors influencing dry-season ecosystem carbon rates in the coastal zone of the Yellow River Delta.

Coastal wetlands are considered as a significant sink of global carbon due to their tremendous organic carbon storage. Coastal CO2 and CH4 flux rates play an important role in regulating atmospheric CO2 and CH4 concentrations. However, the relative contributions of vegetation, soil properties, and spatial structure on dry-season ecosystem carbon (C) rates (net ecosystem CO2 exchange, NEE; ecosystem respiration, ER; gross ecosystem productivity, GEP; and CH4) remain unclear at a regional scale. Here, we compared dry-season ecosystem C rates, plant, and soil properties across three vegetation types from 13 locations at a regional scale in the Yellow River Delta (YRD). The results showed that the Phragmites australis stand had the greatest NEE (-1365.4 μmol m-2 s-1), ER (660.2 μmol m-2 s-1), GEP (-2025.5 μmol m-2 s-1) and acted as a CH4 source (0.27 μmol m-2 s-1), whereas the Suaeda heteroptera and Tamarix chinensis stands uptook CH4 (-0.02 to -0.12 μmol m-2 s-1). Stepwise multiple regression analysis demonstrated that plant biomass was the main factor explaining all of the investigated carbon rates (GEP, ER, NEE, and CH4); while soil organic carbon was shown to be the most important for explaining the variability in the processes of carbon release to the atmosphere, i.e., ER and CH4. Variation partitioning results showed that vegetation and soil properties played equally important roles in shaping the pattern of C rates in the YRD. These results provide a better understanding of the link between ecosystem C rates and environmental drivers, and provide a framework to predict regional-scale ecosystem C fluxes under future climate change.

Quantifying influences and relative importance of fire weather, topography, and vegetation on fire size and fire severity in a Chinese boreal forest landscape

Fire size and fire severity are two crucial parameters for describing fire regimes that reflect spatial heterogeneities of fire spread behavior and its interaction with the environment. Determining how environmental controls regulate these two metrics of the fire regime is of critical importance for predicting response of fire to climate change and designing strategic fire management plans. Here, we evaluated influences and relative contributions of fire weather, topography, and vegetation on fire size and fire severity in a Chinese boreal forest ecosystem. We also compared how relative contributions vary along a continuous gradient of spatial scales using a moving-window resampling approach. Results showed fire weather was the dominant driving factor for fire size, while vegetation and topography exerted stronger influences on fire severity. Such relative influences on fire size and fire severity possessed different scale dependence. For fire size, small burns (<130ha) were mainly constrained by vegetation as it accounted for nearly 43% relative importance, but larger burns (>200ha) were more strongly influenced by extreme fire weather conditions, which accounted for more than 50% relative importance. In contrast, the relative importance of fire weather on fire severity was always less than 20% across the entire range of spatial scales, while relative contributions of vegetation were relatively stable and always greater than 45%. Our study suggests that fuel treatments may have little effect on reducing fire size in boreal forests, but may function to mitigate the severity of future fires. Vegetation type and terrain conditions are important factors to consider for improving efficiency of fuel management.

Evaluating the relative contributions of vegetation and flooding in controlling channel widening: the case of the Nepean River, southeastern Australia

Many lowland stream channels have dramatically widened over the last two centuries. There has been considerable debate about whether this widening was caused by an unusually large flood, by a series of large floods, or by decreased bank stability caused by clearing of riparian vegetation. The relative effects of floods and vegetation can be disentangled in southeastern Australia where streams have undergone both clearing of bank vegetation, and decadal sequences of relatively higher and lower flood magnitude and frequency. Archival aerial photographs of the Nepean River, in southeastern Australia, suggest that banks did not erode during periods of low flood magnitude (drought-dominated regime: from 1901–1949) whether they were cleared or not. However, during periods of flood-dominated regime (1950 to 1970s) only cleared stream banks eroded. Thus, on the upper Nepean River, clearing alone was insufficient to trigger erosion by small floods, and even large floods were unable to erode vegetated banks. The conclusion is that substantial channel widening in this river required both clearing of bank vegetation, and periods of unusually large and frequent floods. This conclusion is supported by geomechanical modelling that examine the reduction in bank shear strength arising from the loss of tree-root reinforcement. The modelling also suggests that bank instability arising from devegetation amplifies the potential for bank failure during the drawdown phase of a flood, leading to channel widening.