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1.
Tamarix taklamakanensis,a dominant species in the Taklimakan Desert of China,plays a crucial role in stabilizing sand dunes and maintaining regional ecosystem stability.This study aimed to determine the water use strategies of T.taklamakanensis in the Taklimakan Desert under a falling groundwater depth.Four typical T.taklamakanensis nabkha habitats(sandy desert of Tazhong site,saline desert-alluvial plain of Qiemo site,desert-oasis ecotone of Qira site and desert-oasis ecotone of Aral site)were selected with different climate,soil,groundwater and plant cover conditions.Stable isotope values of hydrogen and oxygen were measured for plant xylem water,soil water(soil depths within 0–500 cm),snowmelt water and groundwater in the different habitats.Four potential water sources for T.taklamakanensis,defined as shallow,middle and deep soil water,as well as groundwater,were investigated using a Bayesian isotope mixing model.It was found that groundwater in the Taklimakan Desert was not completely recharged by precipitation,but through the river runoff from snowmelt water in the nearby mountain ranges.The surface soil water content was quickly depleted by strong evaporation,groundwater depth was relatively shallow and the height of T.taklamakanensis nabkha was relatively low,thus T.taklamakanensis primarily utilized the middle(23%±1%)and deep(31%±5%)soil water and groundwater(36%±2%)within the sandy desert habitat.T.taklamakanensis mainly used the deep soil water(55%±4%)and a small amount of groundwater(25%±2%)within the saline desert-alluvial plain habitat,where the soil water content was relatively high and the groundwater depth was shallow.In contrast,within the desert-oasis ecotone in the Qira and Aral sites,T.taklamakanensis primarily utilized the deep soil water(35%±1%and 38%±2%,respectively)and may also use groundwater because the height of T.taklamakanensis nabkha was relatively high in these habitats and the soil water content was relatively low,which is associated with the reduced groundwater depth due to excessive water resource exploitation and utilization by surrounding cities.Consequently,T.taklamakanensis showed distinct water use strategies among the different habitats and primarily depended on the relatively stable water sources(deep soil water and groundwater),reflecting its adaptations to the different habitats in the arid desert environment.These findings improve our understanding on determining the water sources and water use strategies of T.taklamakanensis in the Taklimakan Desert. 相似文献
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郁金香属百合科郁金香属多年生鳞茎草本植物,又称洋荷花、草麝香、牡丹百合等,是风靡世界的切花之一,用作花篮、花束和插瓶等装饰品制作,每年的销售量十分巨大,种植者经济效益高。随着产业结构的调整,江苏省许多地方形成郁金香鲜切花基地,但在生产过程中,我们发现每个环节都有可能受到真菌、细菌、病毒病的危害,从而影响到植株的正常生长,降低切花的品质和观赏性,严重时会造成毁灭性危害。因此,防治郁金香病害的发生及发展,是切花生产者首先要考虑的问题。现将郁金香生产中常见的病害发其防治方法介绍如下,以便与广大读者共飨。 相似文献
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The status of regional biodiversity is determined by habitat quality.The effective assessment of habitat quality can help balance the relationship between economic development and biodiversity conservation.Therefore,this study used the InVEST model to conduct a dynamic evaluation of the spatial and temporal changes in habitat quality of the Tarim River Basin in southern Xinjiang Uygur Autonomous Region of China by calc ulating the degradation degree levels for habitat types that were caused by threat factors from 1990 to 2018(represented by four periods of 1990,2000,2010 and 2018).Specifically,we used spatial autocorrelation analysis and Getis-Ord Gi*analysis to divide the study area into three heterogeneous units in terms of habitat quality:cold spot areas,hot spot areas and random areas.Hemeroby index,population density,gross domestic product(GDP),altitude and distance from water source(DWS)were then chosen as the main disturbance factors.Linear correlation and spatial regression models were subsequently used to analyze the influences of disturbance factors on habitat quality.The results demonstrated that the overall level of habitat quality in the TRB was poor,showing a continuous degradation state.The intensity of the negative correlation between habitat quality and Hemeroby index was proven to be strongest in cold spot areas,hot spot areas and random areas.The spatial lag model(SLM)was better suited to spatial regression analysis due to the spatial dependence of habitat quality and disturbance factors in heterogeneous units.By analyzing the model,Hemeroby index was found to have the greatest impact on habitat quality in the studied four periods(1990,2000,2010 and2018).The research results have potential guiding significance for the formulation of reasonable management policies in the TRB as well as other river basins in arid areas. 相似文献
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In this study,we analyzed the hydrological and meteorological data from the Syr Darya River Basin during the period of 1930–2015 to investigate variations in river runoff and the impacts of climate change and human activities on river runoff.The Syr Darya River,which is supplied by snow and glacier meltwater upstream,is an important freshwater source for Central Asia,as nearly half of the population is concentrated in this area.River runoff in this arid region is sensitive to climate change and human activities.Therefore,estimation of the climatic and hydrological changes and the quantification of the impacts of climate change and human activities on river runoff are of great concern and important for regional water resources management.The long-term trends of hydrological time series from the selected 11 hydrological stations in the Syr Darya River Basin were examined by non-parametric methods,including the Pettitt change point test and Mann-Kendall trend tests.It was found that 8 out of 11 hydrological stations showed significant downward trends in river runof f.Change of river runoff variations occurred in the year around 1960.Moreover,during the study period(1930–2015),annual mean temperature,annual precipitation,and annual potential evapotranspiration in the river basin increased substantially.We employed hydrological sensitivity method to evaluate the impacts of climate change and human activities on river runoff based on precipitation and potential evapotranspiration.It was estimated that human activities accounted for over 82.6%–98.7%of the reduction in river runoff,mainly owing to water withdrawal for irrigation purpose.The observed variations in river runoff can subsequently lead to adverse ecological consequences from an ecological and regional water resources management perspective. 相似文献
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水稻秧苗僵苗的症状表现是植株矮小,叶片细瘦,直立不披散,稻丛呈簇立状,根细而稀,新根少。根据秧苗初期因僵苗程度不同,长相长势有所区别,大致可分3个阶段：发僵,为黄化阶段,叶色较淡,矮小萎黄,锈根多,白根少,呈现出营养不良的症状;以后随着生理缺磷程度的加重,进入蓝化阶段，叶色暗绿发蓝，有的黄中带红，叶片沿纵脉呈环状卷曲，老根直伸向下，根毛稀少，这是由于生理缺磷影响能量代谢，使光合作用产物的运输受到严重阻碍导致的；僵苗严重时为红化阶段，老叶变红色，其余叶片除最新抽出叶呈全绿色外，均有不同程度的叶尖枯焦，远看苗色发红。 相似文献
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国内农业植物检疫（以下简称植物检疫）是以法律法规为依据、检疫技术为后盾、植物检疫行政许可和执法监督为保障来控制农业有害生物传播、蔓延、危害,达到促进农产品流通,保护农业生态,确保农业生产高产、优质、高效的目的。植物检疫行政许可在植物检疫工作中起着关键的作用。现把江山市2005年以来贯彻实施《行政许可法》和农业部有关农业行政许可规定过程中的有关情况概述如下。 相似文献
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As an important natural resource,forest land plays a key role in the maintenance of ecological security.However,variations of forest land in the agropastoral ecotone of northern China(AENC)have attracted little attention.Taking the AENC as an example and based on remote-sensing images from 2000,2010 to 2020,we explored the spatiotemporal variation of forest land and its driving factors using the land-use transfer matrix,spatial autocorrelation analysis and spatial error model.The results showed that from 2000 to 2020,the total area of forest land in the AENC increased from 75,547.52 to 77,359.96 km2 and the changes were dominated by the transformations among forest land,grassland and cropland,which occurred mainly in areas with the elevation of 500-2000 m and slope of 15°-25°.There was obvious spatial agglomeration of forest land in the AENC from 2000 to 2020,with hot spots of forest land gathered in the southern marginal areas of the Yanshan Mountains and the low mountainous and hilly areas of the Loess Plateau.The sub-hot spots around hot spots moved southward,the sub-cold spots spread to the surrounding areas and the cold spots disappeared.The spatiotemporal variation of forest land resulted from the interactions of natural environment,socioeconomic and policy factors from 2000 to 2020.The variables of average annual precipitation,slope,terrain relief,ecological conversion program and afforestation policy for barren mountains affected the spatial pattern of forest land positively,while those of annual average temperature,slope and road network density influenced it negatively. 相似文献
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Taking Gansu province as a model case,this study provides an integrated analysis on the eco-economic system of arid and semi-arid region based on emergy synthesis theory. Through calculating the values of renewable emergy flow,non-renewable resources,imported emergy,exported emergy,waste emergy,and total emergy during the period of 1978-2007,the performance of Gansu eco-economic system was analyzed. The results indicated that the renewable emergy flow within the province basically remained steady state which was estimated at 2.99×1022 solar emjoules (sej) from 1978 to 2007. The imported emergy and exported emergy were estimated at 3.75×1017 sej and 2.99×1020 sej in 1978 and increased to 1.07×1022 sej and 1.44×1022 sej respectively in 2007. The nonrenewable emergy flow was estimated at 1.62×1022 sej and increased to 1.85×1023 sej,with annual growth rate of 8.7%,while the estimated total emergy was 4.58×1022 sej in 1978 and increased to 2.11×1023 sej in 2007,with annual growth rate of 5.41%. Our results indicate a deteriorate situation between economic development and environmental protection in the region. The rapid economic growth in the past thirty years was based on a great consumption of nonrenewable resource and caused continuous decrease in the capacity of sustainable development. The environmental loading ratio was 0.53 in 1978,increased to 6.06 in 2007,indicating a rapid degradation of the regional environment quality. We calculated that the actual population was 1.53 times the renewable resource population in 1978,increased to 7.06 times in 2007. During the period of 1978-2007,the emergy rose from 2.45×1015 sej/(capita·a) to 8.07×1015 sej/(capita·a). Our analysis revealed that the emergy density presented a trend of gradual increase,and then the emergy currency ratio in Gansu decreased from 7.08×1013 sej/Chinese Yuan to 7.82×1012 sej/Chinese Yuan. 相似文献
9.
Spatial heterogeneity for grain size distribution of eolian sand soil on longitudinal dunes in the southern Gurbantunggut Desert 总被引：3，自引：1，他引：2
The grain size composition, distribution characteristics and spatial variation of eolian sand soil on distinct positions across two longitudinal dunes and interdune areas were studied by means of conventional grain size analysis and geostatistical methods. In the study, 184 samples of eolian sand soil from the 0-30cm layer were systemically collected and measured from two longitudinal dunes and interdunes in the southern Gurbantunggut Desert. The results show that the dominant grain sizes are fine and very fine sands, and the differences of grain size compositions between the distinct geomorphologic positions are significant. The contents of clay and silt are highest on the interdune areas and lowest on the crests, and higher on the leeward slopes than on the windward slopes. The contents of very fine and fine sands are highest on the windward slopes and lowest on the crests. The contents of medium, coarse and very coarse sands are lowest on the interdune lands, and highest on the crests, and are identical on the two slopes. The coarser sizes (φ1) and mean sizes (Mz) for eolian sand soil all have a varying tendency from fine to coarse sizes with interdune area → leeward slope → windward slope → crest, and the sorting (σ) are poorly to well sorted. The results of geostatistical analysis reveal that φ1, Mz and σ values are moderately to strongly spatially autocorrelated. The values of the spatially correlated ranges are φ1<σ相似文献
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1 农业形势及农作物重大病虫害发生情况 2007年是实施"十一五"规划的第2年.中央一系列的政策继续向农业倾斜.农业部提出了发展现代农业的"十大行动"计划,各级植物保护技术推广部门,进一步加大了对农作物有害生物的防控力度,全力服务于发展现代农业"十大行动"计划的实施,各项工作进展顺利. 相似文献
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苜蓿田地表蜘蛛边缘效应及苜蓿刈割后的溢出效应 总被引：1，自引：0，他引：1
为明确不同类型苜蓿田地表蜘蛛边缘效应及苜蓿刈割后地表蜘蛛溢出效应在小麦田与玉米田之间的差异,于2015年5—7月采用陷阱法调查了银川平原不同类型苜蓿田及邻作玉米田和小麦田中的蜘蛛种类及个体数,比较苜蓿田边缘区及中心区蜘蛛群落多样性指数和个体数量的时空变化以及苜蓿田刈割前后相邻农田边界处蜘蛛群落的时空动态变化。结果表明,在整个取样季节共采集蜘蛛标本7 894头,隶属10科22种,其中苜蓿单作田中蜘蛛个体数量最多,共2 550头;苜蓿-小麦邻作田中蜘蛛群落物种丰富度最高,共17种。星豹蛛Pardosa astrigera和甘肃平腹蛛Gnaphosa kansuensis为优势种,分别占个体总数的38.08%和27.17%。非量度多维尺度(non-metric multidimensional scaling,NMDS)分析显示苜蓿单作田同苜蓿邻(间)作田蜘蛛群落的结构组成差异较大,且在苜蓿田边界处和内部存在差异。不同类型苜蓿田边界处和内部蜘蛛群落的多样性指数、优势度指数、个体数量和丰富度在取样的不同时期存在显著差异。刈割可以促进苜蓿田中地表蜘蛛向邻作农田中迁移,苜蓿刈割后与苜蓿田邻作的小麦田和玉米田中蜘蛛个体数量和多样性指数均存在溢出效应,溢出效应的范围为距界面处0~20 m。小麦田中蜘蛛个体数量密度和多样性指数总体高于玉米田,溢出效应的持续时间为1~7 d,高于玉米田。 相似文献
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用血清学方法评价稻田狼蛛对稻纵卷叶螟的控制作用 总被引：6，自引：0，他引：6
在对稻田狼蛛种群调查和在不同容积条件下的捕食功能反应试验的基础上,对200丛水稻单位容积里的狼蛛种群动态和一头狼蛛捕食一至二龄或三至五龄稻纵卷叶螟数量进行了模拟:N(蜘蛛)=45/(1+exp(1.0769-0.0461t))(?)(1)N_A(一至二龄)=0.5838 No/(1+0.8579 No)(?)(2)N_A(三至五龄)=0.0006 No/(1+0.0007 No)(?)(3)同时,用血清反应方法测得了稻田狼蛛捕食稻纵卷叶螟的阳性反应率(b)和残存时间(d)。在水稻种植后(t)天调查,得知稻纵卷叶螟密度(No),便可按方程(1)、(2)和(3)求得狼蛛密度(a)和被狼蛛捕食的稻纵卷叶螟数(c)。据 Q=a·b·c/100·d可估计稻田狼蛛对稻纵卷叶螟的捕食数量。 相似文献
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中性昆虫在稻田节肢动物群落中作为捕食者营养桥梁作用的研究 总被引：29，自引：2，他引：29
在稻田节肢动物群落中，与水稻无直接营养关系的中性昆虫，如摇蚊、蚊、蝇、弹尾虫等，构成了捕食者猎物的重要组分。系统分析显示，中性昆虫在水稻生长前期为主要的猎物，其丰盛度的比例可高达９０％以上（富阳早稻）。相应地，结网类蜘蛛由于可以大量取食中性昆虫猎物，其个体数量占捕食性天敌的５０％以上，优势种有食虫沟瘤蛛（富阳和句容稻区）、锥腹肖蛸（郑州稻区）等。在一定条件下，结网类捕食者与中性昆虫相对丰盛度的季节动态呈正相关。从农田生态系统的整体性考虑，中性昆虫的生态学意义有必要进一步深入研究 相似文献
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The effects of residues of three commercial pesticides in common use in Europe against cereal pests, on two dominant spider
species, a lycosid and a micryphantid, were evaluated in the laboratory. Insecticide assay methods for juvenile and adult
hunting and adult web-building, ground-dwelling spiders are described. Results varied with different sprayed substrates and
species. Fenvalerate was more toxic than other pesticides and had a longer residual effect on all spiders when tested on moistened
sand than on filter paper. Endosulfan was of high initial toxicity on sand, but was more toxic on filter paper to both adults
and juveniles ofPardosa spp. Pyrazophos was non-toxic to the spiders tested, regardless of substrate. In general, the lycosids were more affected
by pesticides than web-building spiders because of their different life strategies. A sprayed sand substrate matched field
conditions better as a method to test the effects of pesticides on ground-dwelling spiders. 相似文献
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假眼小绿叶蝉的天敌蜘蛛种类及其物种多样性研究 总被引：8，自引：0，他引：8
本文报道了假眼小绿叶蝉的天敌蜘蛛种类,共计２０科８０种,三个生境的物种丰富度指数ＤＭＡ的取值范围在１６．８３３４－１８．２６５７之间,多样性指数Ｈ的范围１．９６２７－２．００５０;均匀度指数Ｊ为０．４８３４－０．５０２６,根据不同生境物种的相似性系数Ｃ进行系统聚类,３个生境在相似系数０．７９３５的水平时全部聚合在一起,化学农药作用的影响。物种多样性明显减少。 相似文献
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陷阱法调查转Bt棉对棉田地面蜘蛛群落的影响 总被引：1，自引：1，他引：0
为明确转Bt棉对非靶标节肢动物棉田蜘蛛群落的影响,在棉花全生长期利用陷阱法对转Bt棉(中棉29)和传统棉田(湘杂3号)蜘蛛的群落多样性及数量动态变化进行了系统调查。结果表明:共采集棉田蜘蛛5 020头,隶属13科33种,其中转Bt棉田2 548头,隶属12科27种,传统棉田2 472头,隶属12科27种;转Bt棉田和传统棉田均以狼蛛科Lycosidae、平腹蛛科Gnaphosidae和隐石蛛科Titanoecidae为优势科,优势科的优势种也均为沟渠豹蛛Pardosa laura、蛞平腹蛛Gnaphosa kompirensis和白斑隐石蛛Nurscia albofasciata,2种棉田在地面蜘蛛群落组成上除少部分稀有物种存在差异外,优势科及优势科的优势种均无显著差异;且3种优势种蜘蛛数量、Shannon-Wiener多样性指数以及物种丰富度均无显著差异;2种棉田地面蜘蛛数量动态变化也无显著差异,均有2个高峰期,分别在苗期和铃期。表明转Bt棉对棉田地面蜘蛛群落无显著影响。 相似文献