Impact of land-use changes and sedimentation on the Muhammad Nur Reservoir, South Kalimantan, Indonesia

The Muhammad Nur Reservoir (MNR) is a major multipurpose reservoir located on the Riam Kanan River in the Indonesian Province of South Kalimantan. The MNR has a high sediment trap efficiency and there is concern that accelerated erosion in the catchment, resulting from inappropriate land use, poses a significant threat to the storage capacity and effective life span of the reservoir. Furthermore, on-going deforestation of large parts of the catchment may have changed the inflow pattern to the reservoir. This paper uses data from fieldwork and published information from different sources to examine the extent of erosion and sedimentation in the catchment and the sediment delivery to the reservoir. Water level variations in the reservoir over a 22-year period are examined for changes that might indicate an alteration of the hydrologic balance in the catchment.     

泾河中游现代洪水痕迹调查对实测洪水的校核

通过对泾河流域实地调查,在泾河中游景村水文站上下游发现了3处非常明显的4次洪水痕迹.结合实地走访,资料查阅等,准确确定了4次洪痕的对应年代,并通过弯道超高水位的计算,以及水位一流量关系和比降法模型模拟,推算出了这4次洪痕对应的流量,与实测洪水资料相比较,流量基本接近,误差分别在1.42%～4021%和~2.13%～3.16%之间.研究表明,为了提高水文测量的精度,可以借助河岸遗留的洪水痕迹校核实测洪峰流量,同时也可为历史洪水调查和缺乏水文观测站数据的流域以洪痕推算特大洪峰流量提供科学的依据.     

不同氮素水平下冬小麦叶片酚酸类物质代谢对FACE的响应

利用开放式空气CO2浓度升高(Free Air Carbon-dioxide Enrichment, FACE)平台, 研究了低氮(LN)和常氮(NN)水平下, 大气CO2浓度升高对冬小麦叶片酚酸类物质代谢的影响.结果表明, CO2浓度升高对小麦叶片水杨酸、对羟基苯甲酸、肉桂酸、阿魏酸和香草酸含量的影响随供氮水平的不同而有所差异.低氮下小麦通过提高叶片苯丙氨酸解氨酶(PAL)活性(30.1%)而使其含量均显著增加, 增幅分别达33.7%、119.6%、26.7%、39.9%和28.6%; 而常氮下PAL活性和酚酸类含量变化均未达显著水平.可见, 大气CO2浓度升高对冬小麦酚酸类物质代谢的影响受氮水平的调控, 在未来CO2浓度升高条件下, 选择适宜的施肥水平将显得更为重要.此外, 总酚含量与水杨酸、对羟基苯甲酸、肉桂酸、阿魏酸和香草酸等含量变化趋势基本一致, 且总酚含量变化的79.6%～151.4%是由这几种酚酸含量变化引起的, 说明CO2浓度升高使水杨酸、对羟基苯甲酸、肉桂酸、阿魏酸和香草酸等含量增加是总酚含量增加的直接原因.低氮条件下大气CO2浓度升高将通过改变酚酸类物质代谢而间接影响小麦与伴生杂草的关系.     

Can differences in soil community composition after peat meadow restoration lead to different decomposition and mineralization rates?

Reducing decomposition and mineralization of organic matter by increasing groundwater levels is a common approach to reduce plant nutrient availability in many peat meadow restoration projects. The soil community is the main driver of these processes, but how community composition is affected by peat meadow restoration is largely unknown. Furthermore, it is unclear whether restoration induced changes could lead to altered decomposition and mineralization rates. We determined soil community composition in restored peat meadows with different groundwater levels and soil pH. This composition was subsequently used in food web model calculations of C and N mineralization rates to assess whether differences in soil community composition may have contributed to differences in decomposition and mineralization rates observed between these meadows.Community composition of micro-organisms, Collembola and Enchytraeidae differed considerably between meadows and were correlated with differences in groundwater levels and soil pH. Collembolan and enchytraeid species from wet and neutral environments were more abundant at meadows with higher groundwater levels. Lower fungal to bacterial PLFA ratios and higher numbers of protozoa indicated an increased importance of the bacterial part of the food web at meadows with higher groundwater levels. Food web model calculations suggested that the observed changes in community composition would lead to higher rates of C and N mineralization at meadows with high groundwater levels. Results from modeling were consistent with field measurements of C mineralization, but not with measurements of N mineralization.We conclude that understanding changes in soil community composition in response to specific restoration measures may help us to better understand ecosystem responses to wetland restoration schemes, especially regarding soil biogeochemical processes.     

Establishing Soil Silicon Test Procedure and Critical Silicon Level for Rice in Louisiana Soils

Calibration of crop responses to applied silicon (Si) serves as a basis for developing Si fertilizer recommendation guidelines. A greenhouse experiment was set up in a randomized complete block design with five replications, two sources of Si (wollastonite and slag) and four Si rates (0, 170, 340 and 680 kg ha^?1) to calibrate plant-available Si for growing rice in Louisiana soils. Silicon concentrations were determined in soils using seven different extraction procedures. Based on a quadratic model (p < 0.05), the estimated soil Si critical level using 0.01 M calcium chloride (CaCl₂) for Sharkey clay soil was 110 mg kg^?1 while for Crowley silt loam and Commerce silt loam, levels were 37 and 43 mg kg^?1, respectively. These results suggest that suitability of an extractant that gives the best estimate of plant-available Si could considerably depend on soil type and it is unlikely that there is a universal extractant for all soils.     

渠系前馈蓄量补偿控制时滞参数算法比较与改进

输水明渠系统控制算法主要由前馈及反馈模块组成,其中前馈模块较大程度上影响了系统控制性能。基于蓄量主动补偿的前馈控制算法受时滞参数影响较大,为比较现有多种算法实际控制性能优劣,并寻求不依赖复杂数值计算的简化时滞参数算法,该文进行了横向的算法比较与优化开发。文章基于蓄量阶跃补偿及蓄量二次补偿2类算法,结合改进比例-积分(proportional-integral,PI)反馈控制器,对典型测试渠系及实际工程渠系建模仿真,选取稳定时间、最大超调流量、绝对值误差积分(integral of absolute magnitude of error,IAE)和绝对流量变化积分(integrated absolute discharge change,IAQ)指标分析了蓄量阶跃补偿、动力波原理、水量平衡模型3种时滞参数算法的控制效果。结果显示,在实际工程渠系中,小流量工况下,蓄量阶跃补偿算法的稳定时间比水量平衡模型算法的稳定时间减小40.42%;大流量工况下,蓄量阶跃补偿算法的最大超调流量最小,仅比目标流量高3%,该算法的稳定时间比水量平衡模型算法的稳定时间减少25.45%。结果表明蓄量阶跃补偿算法控制效果较好,但该算法在推求渠池所需蓄量补偿值时需进行水面线推求,文章依据渠道蓄量变化与流量变化间的线性关系,提出简化的时滞参数显式算法。较传统数值算法,时滞参数显式算法与蓄量阶跃补偿算法的时滞参数差值百分比小于8%,在满足实际工程需求的同时,可明显减少推求所需蓄量补偿值的计算量。文章的比较结论及所提出的简化算法对输配水渠道系统,尤其是大型渠道系统调度具有一定的理论价值和应用前景。     

Indirect regulation of heterotrophic peat soil respiration by water level via microbial community structure and temperature sensitivity

Northern peatlands contain a considerable share of the terrestrial carbon (C) pool, which climate change will likely affect in the future. The magnitude of this effect, however, remains uncertain, due mainly to difficulties in predicting decomposition rates in the old peat layers. We studied the effects of water level depth (WL) and soil temperature on heterotrophic soil respiration originating from peat decomposition (R_PD) in six drained peatlands using a chamber technique. The microbial community structure was determined through PLFA. Within the studied sites, temperature appeared to be the main driver of R_PD. However, our results indicate that there exist mechanisms related to lower WL conditions that can tone down the effect of temperature on R_PD. These mechanisms were described with a mathematical model that included the optimum WL response of R_PD and the effect of average WL conditions on the temperature sensitivity of R_PD. The following implications were apparent from the model parameterisation: (1) The instantaneous effect of WL on R_PD followed a Gaussian form; the optimum WL for R_PD was 61 cm. The tolerance of R_PD to the WL, however, was rather broad, indicating that the overall effect of WL was relatively weak. (2) The temperature sensitivity of R_PD depended on the average WL of the plot: plots with a high average WL showed higher temperature sensitivity than did those under drier conditions. This variation in temperature sensitivity of R_PD correlated with microbial community structure. Thus, moisture stress in the surface peat layer or, alternatively, the lowered temperature sensitivity of R_PD in low water level conditions via microbial community structure and biomass may restrict R_PD. We conclude that a warmer future climate may raise R_PD in drained peatlands only if the subsequent decrease in the moisture of the surface peat layers is minor and, thus, conditions remain favourable for decomposition.     

兴隆庄采煤塌陷蓄水区降水量与地下水位分析

为解决矿区水资源紧缺现象,规划利用塌陷蓄水区水资源成为首选,而掌握塌陷蓄水区水文情况,是塌陷区水资源合理规划利用的前提。以兴隆庄采煤塌陷蓄水区为例,收集整理了蓄水区附近5个水文站1956-2008年降水量及14个地下水观测站1988-2008年地下水位的资料,进行降水量与地下水位分析。结果表明:塌陷蓄水区降水的年度和年内分布不均匀,丰水期和枯水期交替出现。地下水动态类型属于入渗-径流-开采型,随季节和降水量的变化呈现周期性变化,年内变化规律为"下降-上升-下降"3个阶段,地下水流向为东北到西南方向。降水与地下水位关系较为密切,降水量的变化和地下水位年变幅的变化过程趋势一致,且具有滞后性,降水量与延缓1个月的地下水位的线性关系较好。     

基于GIS平台的地下水埋深与植被盖度响应关系研究

由于我国北方地区多为干旱半干旱气候,降雨稀少、蒸发强烈、生态环境脆弱,因此地下水的水位埋深对区内的植被生态有着重要的影响。本次研究以ARCGIS空间分析技术为平台,以我国通辽地区为典型研究对象,在充分掌握区内地质、水文地质以及生态植被等条件的基础上,从区域尺度上定量分析了植被生长状况与地下水位埋深的相互关系。研究表明:在内蒙古通辽地区,适宜植被生长的最佳地下水埋深为2～2.4m,植被能够生长的地下水埋深范围是1.3～3.8m,不适宜植被生长的地下水埋深范围是3.8～7.5m,当地下水埋深大于7.5m时,地下水埋深与植被覆盖度相关度很小。     

河北省桑属植物染色体倍数性研究

研究了桑属植物５个种３２个品种的染色体倍数性，发现宽城１０号等９个品种为三倍体（２ｎ＝３ｘ＝４２），其余为二倍体（２ｎ＝２ｘ＝２８）。