以系统的开放统筹基层地震应急

县(区)地震工作由于人员、资源匮乏一直是地震应急的薄弱环节, 在人员、编制、资源都不能快速增加的前提下, 主动开放自身系统, 更好融入社会应急体系, 同时促进自身发展不失为一种可行的举措.     

Climate,vegetation, and soil controls on hydraulic redistribution in shallow tree roots

Hydraulic redistribution defined as the translocation of soil moisture by plant root systems in response to water potential gradients is a phenomenon widely documented in different climate, vegetation, and soil conditions. Past research has largely focused on hydraulic redistribution in deep tree roots with access to groundwater and/or winter rainfall, while the case of relatively shallow (i.e., ≈1–2 m deep) tree roots has remained poorly investigated. In fact, it is not clear how hydraulic redistribution in shallow root zones is affected by climate, vegetation, and soil properties. In this study, we developed a model to investigate the climate, vegetation, and soil controls on the net direction and magnitude of hydraulic redistribution in shallow tree root systems at the growing season to yearly timescale. We used the model to evaluate the effect of hydraulic redistribution on the water stress of trees and grasses. We found that hydraulic lift increases with decreasing rainfall frequency, depth of the rooting zone, root density in the deep soil and tree leaf area index; at the same time for a given rainfall frequency, hydraulic lift increases with increasing average rainstorm depth and soil hydraulic conductivity. We propose that water drainage into deeper soil layers can lead to the emergence of vertical water potential gradients sufficient to explain the occurrence of hydraulic lift in shallow tree roots without invoking the presence of a shallow water table or winter precipitation. We also found that hydraulic descent reduces the water stress of trees and hydraulic lift reduces the water stress of grass with important implications on tree–grass interactions.     

Decomposition of mangrove roots: Effects of location,nutrients, species identity and mix in a Kenyan forest

Mangrove trees may allocate >50% of their biomass to roots. Dead roots often form peat, which can make mangroves significant carbon sinks and allow them to raise the soil surface and thus survive rising sea levels. Understanding mangrove root production and decomposition is hence of theoretical and applied importance. The current work explored the effects of species, site, and root size and root nutrients on decomposition. Decomposition of fine (≤3 mm diameter) and coarse (>3 mm diameter, up to a maximum of ∼9 mm) roots from three mangrove species, Avicennia marina, Bruguiera gymnorrhiza and Ceriops tagal was measured over 12 months at 6 sites along a tidal gradient in Gazi Bay, Kenya. C:N and P:N ratios in fresh and decomposed roots were measured, and the effects on decomposition of root size and age, of mixing roots from A. marina and C. tagal, of enriching B. gymnorrhiza roots with N and P and of artefacts caused by bagging roots were recorded. There were significant differences between species, with 76, 47 and 44 % mean dry weight lost after one year for A. marina, B. gymnorrhiza and C. tagal respectively, and between sites, with generally slower decomposition at dryer, high tidal areas. N enriched B. gymnorrhiza roots decomposed significantly faster than un-enriched controls; there was no effect of P enrichment. Mixing A. marina and C. tagal roots caused significantly enhanced decomposition in C. tagal. These results suggest that N availability was an important determinant of decomposition, since differences between species reflected the initial C: N ratios. The relatively slow decomposition rates recorded concur with other studies, and may overestimate natural rates, since larger (10–20 mm diameter), more mature and un-bagged roots all showed significantly slower rates.     

Physical mechanisms of plant roots affecting weathering and leaching of loess soil

Vegetation is an important factor in maintaining ecological balance and improving eco-environment. For improving environment, vegetation cover, as a substitute for the integrated action of stems and leaves, seems to be a crucial factor. However, recent st…     

福建万木林自然保护区米槠和杉木细根分解动态

应用网袋法和砂滤管法对福建省万木林自然保护区米槠、杉木细根及两树种细根混合样品分解进行了为期两年的研究。结果表明：（1）两种方法研究细根分解,米槠细根在自身群落中分解最快,月分解速率分别为0．0052（0～1mm）和0．0080（1～2mm）。此外,米槠细根及其混合样品在米槠林中分解,1～2mm径级分解快于0～1mm径级;而杉木细根及其混合样品在杉木林中分解,规律相反。林地土壤环境条件、各径级细根自身的质量特性是影响细根分解的主要因子。（2）两种方法所得结果均能应用Olso负指数方程进行较好的拟合,拟合的各项指标相近。在亚热带森林生态系统中,运用砂滤管法研究细根分解具有可行性。此外,砂滤管法研究细根分解过程中养分的释放规律,具有一定的应用前景。     

极端干旱区胡杨吸水根系的分布与模拟研究

依据2006年7月在极度干旱区内蒙古额济纳旗的实测资料,对胡杨吸水根系根长密度的分布特征进行了分析和拟合,建立了根长密度垂直方向和水平方向的一维、二维分布函数,以期对胡杨根系吸水及胡杨SPAC系统进一步的研究提供有力的试验依据和理论支持。试验结果表明:在垂直方向,吸水根根量主要集中在0~80 cm的土层内,占吸水根总量的97.60%;在水平方向,0~220 cm范围内根长密度随距离的增加而逐渐增大;220~400 cm范围内根长密度随距离的增加而逐渐减小;在0~20 cm范围内,吸水根系仅占总量的0.47%;在160~220 cm范围内,吸水根系分布最为密集,占总量的18.57%。统一采用指数函数对胡杨吸水根系根长密度分布函数进行了拟合,拟合函数与实测数据的相关系数平方分别为:0.888 4、0.680、0.73和0.685,说明胡杨吸水根系根长密度分布也具有与果树相似的规律,基本符合指数衰减规律。     

Analytical study of the effect of the geometrical parameters during the interaction of regular wave-horizontal plate-current

The present work is an analytical study of the influence of geometrical parameters, such as length, thickness and immersion of the plate, on the reflection coefficient of a regular wave for an immersed horizontal plate in the presence of a uniform current with the same direction as the propagation of the incident regular wave. This study was performed using the linearized potential theory with the evanescent modes while searching for complex roots to the dispersion equation that are neither pure real nor pure imaginary. The results show that the effects of the immersion and the relative length on the reflection coefficient of the plate are accentuated by the presence of the current, whereas the plate thickness practically does not have an effect if it is relatively small.     

毛乌素沙地沙柳细根分布规律及与土壤水分分布的关系

以2 mm为粗、细根的划分界限,采用根钻法对毛乌素沙地的单株沙柳及沙柳林地的细根分布进行了调查研究,同时测量土壤含水率。结果表明,沙柳细根垂直分布深度为1.5 m左右,且随土壤深度的增加细根生物量逐渐减少,细根根量最大值出现在表层,在0～20 cm范围内集中分布,约占总根量的一半左右。沙柳水平根系发达,细根主要分布在冠幅半径3倍左右的范围内,表明沙柳通过水平扩展来获取分布于土壤浅层的大气降水;丘顶沙柳林地根量小于丘底林地根量,土壤水分的含量和分布决定沙柳细根根量的大小和分布。     

加强广西气象部门基层财务管理工作的思考

通过分析目前广西气象部门基层财务管理现状存在的问题,提出加强基层财务管理的一些建议。