西北半干湿地区雨水花园植物应用及适宜性评价

为了科学地选择适宜于西北半干湿地区雨水花园栽植的植物种类,在分析国内外研究的基础上,对位于西北半干湿地区的西咸新区典型雨水花园进行实地调研。采用层次分析法,从生态学特性、观赏特性、功能特性对雨水花园种植的76种植物进行适宜性综合评价,从3个准则层和10个指标层构建评价体系。结果发现:截留雨水能力、抗逆能力、花期花色、净化水体能力4个指标对于雨水花园植物选择的影响最大;金叶女贞、白花草木犀、千屈菜等的适宜性较好,葱兰、酢浆草、佛甲草等的适宜性较差。根据雨水花园的类型及蓄水情况,提出边缘区、缓冲区、蓄水区适宜栽植的植物类型,并总结出选择的原则。研究结果可为西北半干湿地区雨水花园植物适宜性选择提供依据。

Impact of Wetland Change on Local Climate in Semi-arid Zone of Northeast China

Wetlands are sensitive to climate change, in the same time, wetlands can influence climate. This study analyzed the spa- rio-temporal characteristics of wetland change in the semi-arid zone of Northeast China from 1985 to 2010, and investigated the impact of large area of wetland change on local climate. Results showed that the total area of wetlands was on a rise in the study area. Although natural wetlands （marshes, riparians and lakes） decreased, constructed wetlands （rice fields） increased significantly, and the highest in- crease rate in many places exceeded 30%. Anthropogenic activities are major driving factors for wetland change. Wetland change pro- duced an impact on local climate, mainly on maximum temperature and precipitation during the period of May-September. The increase （or decrease） of wetland area could reduce （or increase） the increment of maximum temperature and the decrement of precipitation. The changes in both maximum temperature and precipitation corresponded with wetland change in spatial distribution. Wetland change played a more important role in moderating local climate compared to the contribution of woodland and grassland changes in the study area. Cold-humid effect of wetlands was main way to moderating local climate as well as alleviating climatic wanning and drying in the study area, and heterogeneity of underlying surface broadened the cold-humid effect of wetlands.

Application of Developed Grid-GA Distributed Hydrologic Model in Semi-Humid and Semi-Arid Basin

A grid and Green-Ampt based （Grid-GA）distributed hydrologic physical model was developed for flood simulation and forecasting in semi-humid and semi-arid basin. Based on topographical information of each grid cell extracted fi＇om the digital elevation model （DEM） and Green-Ampt infiltration method, the Grid-GA model takes into consideration the redistribution of water content, and consists of vegetation and root interception, evapotranspiration, runoff generation via the excess infiltration mechanism, runoff concentration, and flow routing. The downslope redis- tribution of soil moisture is explicitly calculated on a grid basis, and water exchange among grids within runoff routing along the river drainage networks is taken into consideration. The proposed model and Xin＇anjiang model were ap- plied to the upper Lushi basin in the Luohe River, a tributary of the Yellow River, with an area of 4 716 km2 for flood simulation. Results show that both models perform well in flood simulation and can be used for flood forecasting in semi-humid and semi-arid region.

Global vulnerability to agricultural drought and its spatial characteristics

As an important part of agricultural drought risk, agricultural drought vulnerability helps effectively prevent and alleviate drought impacts by quantifying the vulnerability as well as identifying its spatial distribution characteristics. In this study, global agricultural cultivation regions were chosen as the study area; six main crops(wheat, maize, rice, barley, soybean,sorghum) were selected as the hazard-affected body of agricultural drought. Then, global vulnerability to agricultural drought was assessed at a 0.5° resolution and finally, its distribution characteristics were revealed. The results indicated that the area percentages of different grades of global vulnerability to agricultural drought from low to very high were 38.96%, 28.41%,25.37%, and 7.26%, respectively. This means that the total area percentage of high and very high vulnerability zones exceeded30% of the study area. Although high and very high vulnerability zones were mainly distributed in arid and semi-arid regions,approximately 40% of those above were distributed in humid and semi-humid regions. In addition, only about 15% of the population in this study was located in the high vulnerability regions. Among the vulnerability factors, water deficit during the growing season and the irrigation area ratio are the key factors affecting regional vulnerability. Therefore, the vulnerability could be reduced by adjusting crop planting dates and structures as well as by improving irrigation level and capacity.

Regional applicability of seven meteorological drought indices in China

The definition of a drought index is the foundation of drought research.However,because of the complexity of drought,there is no a unified drought index appropriate for different drought types and objects at the same time.Therefore,it is crucial to determine the regional applicability of various drought indices.Using terrestrial water storage obtained from the Gravity Recovery And Climate Experiment,and the observed soil moisture and streamflow in China,we evaluated the regional applicability of seven meteorological drought indices:the Palmer Drought Severity Index(PDSI),modified PDSI(PDSI_CN) based on observations in China,self-calibrating PDSI(scPDSI),Surface Wetness Index(SWI),Standardized Precipitation Index(SPI),Standardized Precipitation Evapotranspiration Index(SPEI),and soil moisture simulations conducted using the community land model driven by observed atmospheric forcing(CLM3.5/ObsFC).The results showed that the scPDSI is most appropriate for China.However,it should be noted that the scPDSI reduces the value range slightly compared with the PDSI and PDSI_CN;thus,the classification of dry and wet conditions should be adjusted accordingly.Some problems might exist when using the PDSI and PDSI_CN in humid and arid areas because of the unsuitability of empiricalparameters.The SPI and SPEI are more appropriate for humid areas than arid and semiarid areas.This is because contributions of temperature variation to drought are neglected in the SPI,but overestimated in the SPEI,when potential evapotranspiration is estimated by the Thornthwaite method in these areas.Consequently,the SPI and SPEI tend to induce wetter and drier results,respectively.The CLM3.5/ObsFC is suitable for China before 2000,but not for arid and semiarid areas after 2000.Consistent with other drought indices,the SWI shows similar interannual and decadal change characteristics in detecting annual dry/wet variations.Although the long-term trends of drought areas in China detected by these seven drought indices during 1961-2013 are consistent,obvious differences exist among the values of drought areas,which might be attributable to the definitions of the drought indices in addition to climatic change.