Microclimate and CO2 fluxes on continuous fine days in the Xihu desert wetland,China

The Xihu desert wetland is located in an extremely arid area in Dunhuang,Gansu province of Northwest China.The area is home to an unusual geographic and ecological environment that is considered unique,both in China and the world.Microclimate is not only related to topography,but is also affected by the physical properties of underlying ground surfaces.Microclimate and CO2 flux have different characteristics under different underlying surface conditions.However,until now,few studies have investigated the microclimate characteristics and CO2 flux in this area.The eddy covariance technique(ECT) is a widely used and effective method for studying such factors in different ecosystems.Basing on data from continuous fine days obtained in the Dunhuang Xihu desert wetland between September 2012 and September 2013,this paper discussed and compared the characteristics of daily microclimate variations and CO2 fluxes between the two periods.Results from both years showed that there was a level of turbulent mixing and updraft in the area,and that the turbulent momentum flux was controlled by wind shear under good weather conditions.The horizontal wind velocity,friction wind velocity and vertical wind velocity were commendably consistent with each other.Air temperature in the surface layer followed an initial decreasing trend,followed by an increasing then decreasing trend under similar net radiation conditions.With changes in air temperature,the soil temperature in the surface layer follows a more obvious sinusoidal fluctuation than that in the subsoil.Components of ground surface radiation during the two study periods showed typical diurnal variations.The maximum diurnal absorption of CO2 occurred at around 11:00(Beijing time) in the Xihu desert wetland,and the concentrations of CO2 in both periods gradually decreased with time.This area was therefore considered to act as a carbon sink during the two observation periods.     

近40年洮河流域干燥度变化趋势分析

利用洮河流域7个气象站1971-2010年的地面气象观测资料,根据Holdridge生命地带模型对洮河流域近40 a的干燥度变化进行了分析。结果表明：近40 a洮河流域内可能蒸散率（PER）以0．02·10a-1～0．07·10a-1的趋势上升,20世纪90年代后 PER的平均值比20世纪90年代前上升了0．12,洮河流域从20世纪90年代开始出现了明显的变干的趋势;近40 a洮河流域温度呈明显上升趋势,上升趋势为0．32～0．54℃·10a-1,20世纪80年代末到90年代洮河流域气温出现了暖突变;降水量呈减少的趋势,其中以中、下游减少最明显,减少趋势为13．3～21．8 mm·10a-1;洮河流域出现了明显的暖干化趋势。     

内陆干旱区农业发展的水资源“增长阻力”——黑河中游实证研究

水资源短缺已成为制约内陆干旱区农业可持续发展的关键因子。本文在借鉴罗默的“增长阻力”概念模型的基础上,以地处黑河中游的民乐县和临泽县为典型研究区域,利用2000—2010年的农业生产面板数据集,度量了水资源紧缺对内陆干旱区农业生产的制约程度。结果表明,由于水资源要素的限制,民乐县和临泽县的农业总产值平均每年的增速要比上年降低0.9979个百分点和0.6228个百分点。在此基础上,对“增长阻力”的影响因素进行了进一步分析,并从节水设施改造,构建农田水利设施的长效机制,发展特色节水农业,提高水资源社会化管理水平和营造节水型社会建设的氛围五个方面,就如何减少水资源要素对农业发展的“增长阻力”提出了相应的政策建议。     

Effects of cotton field management practices on soil CO2 emission and C balance in an arid region of Northwest China

Changes in both soil organic C storage and soil respiration in farmland ecosystems may affect atmospheric CO2 concentration and global C cycle. The objective of this field experiment was to study the effects of three crop field management practices on soil CO2 emission and C balance in a cotton field in an arid region of Northwest China. The three management practices were irrigation methods（drip and flood）, stubble managements（stubble-incorporated and stubble-removed） and fertilizer amendments（no fertilizer（CK）, chicken manure（OM）, inorganic N, P and K fertilizer（NPK）, and inorganic fertilizer plus chicken manure（NPK＋OM））. The results showed that within the C pool range, soil CO2 emission during the whole growing season was higher in the drip irrigation treatment than in the corresponding flood irrigation treatment, while soil organic C concentration was larger in the flood irrigation treatment than in the corresponding drip irrigation treatment. Furthermore, soil CO2 emission and organic C concentration were all higher in the stubble-incorporated treatment than in the corresponding stubble-removed treatment, and larger in the NPK＋OM treatment than in the other three fertilizer amendments within the C pool range. The combination of flood irrigation, stubble incorporation and application of either NPK＋OM or OM increased soil organic C concentration in the 0-60 cm soil depth. Calculation of net ecosystem productivity（NEP） under different management practices indicated that the combination of drip irrigation, stubble incorporation and NPK＋OM increased the size of the C pool most, followed by the combination of drip irrigation, stubble incorporation and NPK. In conclusion, management practices have significant impacts on soil CO2 emission, organic C concentration and C balance in cotton fields. Consequently, appropriate management practices, such as the combination of drip irrigation, stubble incorporation, and either NPK＋OM or NPK could increase soil C storage in cotton fie     

Influence of vegetation parameters on runoff and sediment characteristics in patterned Artemisia capillaris plots

Vegetation patterns are important in the regulation of earth surface hydrological processes in arid and semi-arid areas. Laboratory-simulated rainfall experiments were used at the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Yangling, northwestern China, to quantify the effects of Artemisia capillaris patterns on runoff and soil loss. The quantitative relationships between runoff/sediment yield and vegeta- tion parameters were also thoroughly analyzed using the path analysis method for identifying the reduction mechanism of vegetation on soil erosion. A simulated rainfall intensity of 90 mm/h was applied on a control plot without vegetation(C0) and on the other three different vegetation distribution patterns: a checkerboard pattern(CP), a banded pattern perpendicular to the slope direction(BP), and a single long strip parallel to the slope direction(LP). Each patterned plot received two sets of experiments, i.e. intact plants and roots only, respectively. All treatments had three replicates. The results showed that all the three other different patterns(CP, BP and LP) of A. capillaris could effectively reduce the runoff and sediment yield. Compared with C0, the other three intact plant plots had a 12%–25% less runoff and 58%–92% less sediment. Roots contributed more to sediment reduction(46%–70%), whereas shoots contributed more to runoff reduction(57%–81%). BP and CP exhibited preferable controlling effects on soil erosion compared with LP. Path analysis indicated that root length density and plant number were key pa- rameters influencing runoff rate, while root surface area density and root weight density were central indicators affecting sediment rate. The results indicated that an appropriate increase of sowing density has practical signifi- cance in conserving soil and water.     

Interaction between Cd and Pb in the soil-plant system: a case study of an arid oasis soil-cole system

The Hexi Corridor,our study area,is located in Northwest China and is also the most developed area of oasis farming in arid regions of Northwestern China.However,the rapid development of metallurgy and chemical industries in this region poses a great threat to the accumulation of heavy metals in crops.The objectives of this study are(1)to determine the influence of heavy metals on plant growth;(2)to assess the translocation capability of heavy metals in soil-plant system;and(3)to investigate the interaction between heavy metals.Pot experiments were conducted on cole(Brassica campestris L.)grown in the arid oasis soils singly and jointly treated with cadmium(Cd)and lead(Pb).Nine treatments were applied into the pots.Under the same planting conditions,three scenarios of Cd,Pb and Cd–Pb were designed to compare the interaction between Cd and Pb.The results showed that the response of cole weights to Cd,Pb and Cd–Pb treatments was slight,while Cd and Pb uptakes in cole were more sensitive to the single effects of Cd and Pb concentration in soils from the lower treatment levels.Under the influence of the single Cd,Pb and joint Cd–Pb treatments,Cd concentrations were lower in the cole roots than in the shoots,while for Pb,the results were opposite.Comparison studies revealed that the interaction of Cd and Pb could weaken the cole’s ability to uptake,concentrate and translocate heavy metals in arid oasis soils.     

极端干旱区生态信息表达方法

极端干旱区生态过程与生态现象具有特殊性,分析生态信息的表达模式与方法,对于进一步认识与理解其内涵、特征及规律具有重要的理论价值与现实意义.以20世纪90年代初、2000年的TM和2005年的CBERS-2/CCD影像作为提取生态景观信息图谱的基础资料;依据干旱区MODS特有的耦合关系,将我国极端干旱区的新疆吐鲁番划分为4个一级类型与13个二级类型.同时,借助GIS符号库,从客观真实性与美观实用性等角度,设计了景观生态专题制图符号体系;极端干旱区景观生态信息图谱模式由图形和特殊符号,描述性数字参数,数学模型3个成分组成;在ERDAS 8.5及ArcGIS 9.0的支持下,编制了景观生态专题图,最终实现了景观要素的图谱表达.     

干旱荒漠区封育沙地植被群落特征变化研究

以天然植被围栏封育和人工种植+围栏封育措施下沙地植物群落为对象,以无封护的流动沙地做对照,研究了不同恢复措施对沙地群落物种组成及结构变化的影响.结果表明,(1)封育15 a后,人工种植+围栏封育区侵入物种的丰富度随演替的进展已达12种,其中猪毛菜7.562株/m~2,碟果虫实3.233株/m~2,雾冰藜3.017株/m~2,沙米1.615株/m~2,狗尾草1.112株/m~2.种类组成及生活型结构在向天然植被围栏封育区植物群落靠近,但两者间仍表现出较大差异.(2)在类型组成上,两种封育措施区差异主要表现在优势科及各科种类数量上.(3)在综合多样性特征上,两种措施区草被层的Shannon指数和丰富度指数存在显著差异,而其余各指数两者差异均不显著,但天然植被围栏封育区灌木层的生态优势度指数较高.(4)群落的相似性指数表明,两种封育措施间的植物群落差距较大,且2种封育措施下的植物群落与植被呈零星状分布的无封护措施的流动沙地相比,生态差距均十分显著,这表明封育可明显促进沙地植被的多样性恢复,其中人工种植对沙地植物群落物种多样性恢复的作用是相对缓慢而渐进的.     

极端干旱地区滴灌条件下葡萄生长发育特征

不同滴灌布设方式下,土壤含水率不尽相同,作物的长势和产量也因此受到影响。为探究滴灌管道布置方式和系统技术参数对葡萄植株生长发育特性和产量的影响,并优选出适合吐哈盆地的葡萄滴灌技术参数,该文对不同滴灌技术下土壤含水率以及成熟期葡萄植株生理指标进行观测和分析,结果表明：地面滴灌3管布置、滴头流量2.7 L/h、滴头间距30 cm的处理达到了最优效果,该处理下的土壤含水率、葡萄水分生理指标和产量均处于较高水平。     

干旱区五种野生观赏植物的引种栽培试验

本文采用不同催芽方法、育苗和栽培技术 ,对蒙古扁桃 ( Prunus mongolica Max-im.)、粗壮黄芪 ( Astragalus H oantchy Franch.)、沙冬青 ( Ammopiptanthus mongolicus ( Max-im.) Cheng f.)、山丹 ( L iliun pumilum DC.)和内蒙古野丁香 ( Leptodermis ordosica H.C.)五种分布于内蒙古西部具有观赏价值又为珍稀濒危植物的种子萌发特性、成苗特性进行了研究 ,同时进行了引种栽培技术的初步探索。结果表明 :蒙古扁桃和粗壮黄芪的种子经机械打磨处理后 ,在湿润的沙性基质中栽培效果较好 ,生长两年的植株移栽成活率较高 ;山丹在壤土中萌发率较高 ,异地移栽的山丹 ,如室内栽培 ,需进行春化作用和人工授粉才能开花、结果 ;沙冬青在沙性较强的基质及一定的湿度条件下栽培效果良好 ;内蒙古野丁香则在黏土中生长良好。