Graveshovmand6490

The positive effect of nitrogen deposition on soil respiration was mainly in the growing season, with slightly inhibitive effect in the non-growing season.Understanding the changes of runoff, sediment transport, and hydrodynamic parameters of slopes under the influence of landscape patch coverage and connectivity is of great significance for revealing the hydrodynamic mechanism and hydrological connectivity of slope soil erosion process. In this study, the changes of runoff, sediment transport and hydrodynamic parameters of downhill surface in different coverage levels (0%, 20%, 40%, 60%, 90%) and different connectivity modes (vertical path, horizonal path, S-shaped path, random patches) of shrublands were analyzed by field artificial simulated rainfall test. The results showed that, with the increases of shrub cove-rage, runoff yield and sediment yield decreased exponentially. When the coverage increased to more than 60%, the capacity of shrubs to reduce runoff and sediment became stable. Selleck Idasanutlin With the increases of shrub coverage, flow velocity, flow depth, Reynolds number, Froude number, stream power, and flow shear resistance significantly decreased, while Manning's roughness coefficient and Darcy-Weisbach resistance coefficient increased significantly. When shrub coverage increased to more than 60%, there was no significant difference in the eigenvalues of hydraulic parameters. The runoff rate under the four connectivity modes followed the order of vertical path > S-shaped path > horizonal path > random patches. The sediment rate was the largest in the vertical path, followed by the S-shaped path, and the horizonal path was not significantly different from the random patches. The path with poor connectivity (horizonal path, random patches) exhibited stronger resistance of hydraulic transmission and poor hydraulic sedimentation capacity than the well-connected path (vertical path, S-shaped path). Our results could provide important theoretical basis for soil erosion control on the Loess Plateau and high-quality development of the Yellow River basin.To clarify the morphological characteristics of soil preferential flow and the effect of plant roots on its formation, plants from the typical vegetation types of an artificial woodland (Leucaena acacia) and a dry watershed grassland (Heteropogon contortus) of Yuanmou County, Jinsha River were selected as the experimental objects. Based on the staining and tracing method combined with Photoshop CS5 and the Image-Pro Plus 6.0 image processing technology, we analyzed the morphological and distribution characteristics of soil preferential flow under the two planting types and examined the effects of plant roots. We found significant difference in soil preferential flow dyeing area between the woodland and grassland species, and the overall variation trend of the forestland dyeing area ratio decreased with increasing soil depth. The dyeing area of the grassland decreased monotonously with the increases of soil depth. The occurrence degree of soil preferential flow in forest was higher than that of grassland. Root systemaffected the formation of soil preferential flow. At the root diameter ranges of 0≤d≤5 mm and d>10 mm, root length density of the woodland showed a monotonous decreasing trend with increasing soil depth, while in the root diameter range of 5 mm5 mm. The overall change trend of soil preferential flow dyeing area of two vegetation types in the study area decreased with increasing soil depth. Plant root system was closely related to the formation of soil preferential flow. Fine roots could promote while coarse roots may retard the formation of preferential flows.We examined the effects of retention density on plant DBH (diameter at breast height), height, volume growth, stand biomass, and stand economic benefit of Cunninghamia lanceolata plantation by Pingxiang, Guangxi Province. Four treatments of different retention density were set up a 14-year middle-aged Cunninghamia lanceolata plantation, 500, 750 and 1000 trees·hm-2, with stand without thinning as the control (1500 trees·hm-2). Results showed that DBH (20.55 cm), increment in height (15.70 m), and large-diameter timber volume (18.31 m3·hm-2) of the C. lanceolata plantation were the highest in 500 trees·hm-2 treatment. The volume of living trees was the highest in the control (199.63 m3·hm-2), which was significantly higher than that in 500 and 750 trees·hm-2. The biomass of arbor layer and ecosystem, as well as the economic benefit differed significantly across the treatments, with arborous biomass (90.72 t·hm-2), ecosystem biomass (94.97 t·hm-2), and economic benefit (1.184×105 yuan·hm-2) of 1000 trees·hm-2 treatment being significantly higher than others. Reducing stand retention density increased the DBH, plant height, timber diameter, proportion of large diameter timber, average volume and biomass of single timber, but it did not enhance the volume of living trees. The retention density of 1000 trees·hm-2 was the optimum for middle-aged C. lanceolata plantation. Compared with the control, it significantly increased the total stand volume, arbor biomass, ecosystem biomass, and economic benefit by 2.3%, 5.7%, 4.7%, and 5.8%, respectively.Stand age is a key factor affecting carbon stocks and fluxes of forest ecosystem. Quantification of the changes in forest productivity with stand development is critically important for optimizing forest age structure, facilitating maximum utilization of resources, and better realizing the role of forests in regulating the uptake, storage, and emission of CO2. In this study, using space for time substitution approach, we established 12 chronosequence plots in the broadleaf-Korean pine forests of Lushuihe. Using a locally parameterized Biome-BGC model, we simulated the dynamics of net primary productivity (NPP) with stand development and examined the changes with stand development in NPP of broadleaf-Korean pine forests under four developmental scenarios. Results showed that the biomass in broadleaf-Korean pine forests of different age-classes ranked in the order of young stand less then mid-age stand less then mature stand less then over-mature stand, with the average value of (224.35±20.68), (237.23±39.