辽北农牧交错带土地荒漠化及景观格局变化研究

以1999年和2010年两期TM遥感影像为基础数据,借助地理信息系统技术及Fragstats 3.3景观格局分析软件,分析了辽北农牧交错带11年间土地荒漠化变化特征及景观格局的演变规律。结果表明:1999—2010年研究区荒漠化土地呈减少趋势,减少了18 114.93 hm2,其中轻度荒漠化土地的减少对该时期荒漠化土地减少起主导作用;斑块数明显增加,景观破碎化程度加剧,景观多样性有所增强,其中轻度荒漠化景观始终为研究区优势景观,中度荒漠化景观类型斑块形状趋于规整有连片趋势,重度荒漠化景观有所减少。     

西藏荒漠化动态变化研究

西藏是青藏高原主体,也是环境敏感和荒漠化比较严重的区域之一。掌握西藏荒漠化的动态变化对于该区荒漠化治理规划的制定和实现国土资源的可持续利用具有重要意义。利用西藏的两期荒漠化监测数据进行了对比分析研究。结果表明,与1999年相比,目前西藏荒漠化总体上呈恶化趋势,但局部得到逆转。1999年～2004年的5年间,西藏荒漠化面积增加6.47万hm^2;荒漠化程度有加重趋势,表现为轻度荒漠化、重度荒漠化和极重度荒漠化面积分别减少8.26%、1.78%和0.41%,中度荒漠化面积增加10.45%;荒漠化空间分布发生了一定的变化,干旱区荒漠化面积减少11.17万hm^2,而半干旱区和亚湿润干旱区的荒漠化呈一定的扩展趋势（未统计冻融荒漠化土地）,其中阿里、日喀则地区荒漠化面积扩大,其他区的荒漠化面积则有不同程度的减少。气候暖化和降水变化是西藏荒漠化变化的主要原因,但人为因素对西藏荒漠化的发展起了一定的促进和缓解的作用。     

河北省山区土壤侵蚀动态变化趋势研究

对比分析两次土壤侵蚀遥感调查结果显示:河北省山区极强度和强度土壤侵蚀得到了有效遏止,极强度侵蚀面积减少了818.22 km²,强度侵蚀面积减少了4 293.38 km²;中度和轻度土壤侵蚀面积呈增加趋势,中度土壤侵蚀面积增加3 314.86 km²,轻度土壤侵蚀面积增加6 153.9 km²;河北省山区土壤侵蚀总面积增加,轻度以上的土壤侵蚀面积增加4 357.16 km²。张家口市土壤侵蚀变化比较明显,极强度和强度土壤侵蚀面积明显减少,减少了3 646.46 km²,而中度和轻度侵蚀面积大幅度增加,增加了9 599.69 km²,轻度以上的土壤侵蚀面积增加了5 953.23 km²。     

基于GIMMS NDVI的黄土高原地区荒漠化时空特征分析

气候暖干化发展趋势使干旱半干旱地区生态环境受到荒漠化发展的胁迫,植被覆盖度能有效地表达研究区植被分布状况及荒漠化程度。利用遥感技术手段监测区域植被覆盖和荒漠化发展趋势是非常有效的途径。为了给黄土高原地区生态环境建设和荒漠化治理提供科技信息,利用1986—2006年的GIMMS AVHRR NDVI数据,采用像元二分法估算植被覆盖度;借鉴水蚀风蚀研究成果确定植被覆盖度和荒漠化关系并进行分级,对黄土高原地区荒漠化程度及时空变化进行分析。结果表明:1)黄土高原约64%的地区为植被覆盖度为10%~50%的中度和重度荒漠化区;约1/3的地区为植被覆盖度在50%以上的轻度和非荒漠化区;约3%的地区为植被覆盖度<10%的强烈荒漠化区。2)1986—2006年间,黄土高原地区整体上荒漠化程度表现为降低趋势,期间,中度和重度荒漠化面积显著减少,非荒漠化面积明显增加,而强烈荒漠化面积扩大。荒漠化程度的时间变化具有10年尺度特征。3)中度和重度荒漠化的区域具有转化频繁和连片性特征,轻度和非荒漠化区域空间转化零散破碎,强烈荒漠化扩大区域主要在宁夏甘肃的沿黄两岸。     

新疆艾比湖湿地LUCC对景观格局演变的影响

以新疆艾比湖湿地保护区为研究区,采用1990年10月5日、2000年9月25日和2015年9月13日TM/ETM+影像,以土壤实测数据为基础,建立适宜的土地利用分类体系,分析了25 a间研究区的土地利用动态变化,以及景观格局的时空演变,从而深入探讨了土地利用变化对景观格局演变的影响。结果表明:(1)25 a间,研究区综合土地利用动态度为0.97%,且呈现逐年降低趋势,土地利用类型随着时间的推移,变化由剧烈逐步驱于平衡状态。1990—2000年间,林地和水田的面积增加,中轻度盐渍地和极重度盐渍地面积依然呈现明显的上升趋势;2000—2015年间,水体面积明显减少,沙漠面积急剧增加,重度盐渍地和极重度盐渍地面积呈现增加趋势。(2)25 a间研究区景观格局发生了很大的变化。蔓延度持续减小,分散与并列指数显著增加,景观的延展性下降,导致景观破碎化加剧。Shannon多样性指数和Shannon均匀度指数均呈现稳步增加趋势,这说明景观的异质性程度呈现上升趋势。(3)土地利用变化改变了景观格局,导致景观分散与并列指数增加,蔓延度降低,均匀度增加,研究区景观整体先向破碎化发展,后略有所好转,逐步向稳定优化的趋势发展,但总体的盐渍化和荒漠化趋势依然严峻。该研究进一步提出了改良方案,对研究区土地资源的合理利用和可持续发展研究具有重要意义。     

基于MODIS的土壤含水量时空变化及干旱化程度分析

以内蒙古锡林郭勒盟为研究区域,基于MODIS数据,反演得到锡林郭勒盟地表含水量指数(SWCI),结合野外实测数据对其进行了修正。选取了2000—2017年每年7月份,枯水年(2007年)、平水年(2015年)和丰水年(2012年)生长季4—9月的数据,结合气象资料对研究区土壤含水量的时空变化特征进行了分析,通过土壤含水量对锡林郭勒盟干旱化程度进行了定量分析。结果表明:(1)锡林郭勒盟土壤含水量空间分布自西南向东北呈条带状逐渐增加趋势,荒漠草原典型草原草甸草原。(2)锡林郭勒盟4—5月份的土壤含水量变化幅度不大,空间分布较均一;6—7月份的土壤含水量随着降水的增减而增减,呈现明显的由西向东增加的空间分布趋势;8月份,土壤含水量基本达到最低值;9月份土壤含水量有所回升。(3)锡林郭勒盟的土壤含水量与降水、水汽压和相对湿度呈正相关,与气温呈负相关。(4)锡林郭勒盟以中度干旱面积为主,重度干旱面积占比最小;其中,苏尼特右旗、二连浩特市、苏尼特左旗、阿巴嘎旗、镶黄旗长期处于中度干旱状态;东乌珠穆沁旗东部、西乌珠穆沁旗东部、多伦县多数情况无旱情发生。     

三峡库区不同土地利用背景下的土壤侵蚀时空变化及其分布规律

土壤侵蚀是影响三峡库区土壤养分流失、河道淤积等一系列生态环境问题的重要原因,本文基于GIS技术,采用通用土壤流失方程,对三峡库区1990、1995、2000、2005和2010年的土壤侵蚀进行计算,并对研究区1990-2010年不同土地利用背景下土壤侵蚀强度的时空变化和分布规律进行定量分析.结果表明:1990-2010年,三峡库区平均土壤侵蚀模数与土壤侵蚀量呈减少的趋势,多年平均土壤侵蚀量为18 356.450 7万t,属于中度侵蚀;从空间上看,研究区微度、轻度侵蚀等级分布面积最广.在同一年分内,6种不同土地利用下土壤侵蚀模数依次为:旱地＞草地＞林地＞未利用地＞水田＞建设用地;不同土地利用下的土壤侵蚀差异显著,不同土地利用对土壤侵蚀的贡献率相差很大;各土地利用类型中,微度侵蚀的面积逐渐增加,中度侵蚀及以上侵蚀等级的侵蚀面积,都不同程度的向低等级转移;随着退耕还林还草及大量农村劳动力的外出,库区的土壤侵蚀总体上呈现转好的趋势,但是局部地区的治理工作仍需加强.     

云南省水土流失变化趋势分析

1999年与 1 987年两次遥感调查结果对比分析表明 ,云南省水土流失面积减少 5 0 97km2 ,全省轻度、极强度和剧烈流失面积呈减少趋势 ,而中度与强度流失面积呈增加趋势。 1 989年开始实施的“长治”工程范围内水土流失面积明显减少 ,部分县水土流失面积减少 37%～ 47%。全省人为水土流失虽仍较严重 ,但治理速度大于破坏速度 ,总体恶化趋势已得到初步控制     

我国农牧交错区土地退化研究——以宁夏盐池县为例

 从荒漠化发展历史角度出发,通过收集历史资料和固定样地观测,采用数学分析方法,利用马尔可夫链(Markov)模型和模糊模式识别方法对盐池荒漠化现状、动态变化以及荒漠化治理措施效益进行分析。结果表明:1)盐池县近半个世纪以来土地荒漠化呈急剧扩大趋势,荒漠化土地面积平均年增长率4.03％。2)盐池县荒漠化主要原因是在脆弱生态环境基础上,人为不合理经济活动所致。3)如果能做到严格执法,全面落实禁牧政策并加强防沙治沙工程管理,盐池县荒漠化土地将得到全面治理,否则盐池县荒漠化形势将继续恶化。认为能否全面落实禁牧和退耕还林政策,将直接影响盐池县荒漠化防治。     

毛乌素沙地近30年沙漠化土地时空动态演变格局

应用1990—2017年7期遥感影像作为数据源,通过计算沙漠化指数和沙漠化重心迁移等指标,对毛乌素沙地近30年沙漠化时空动态演变格局进行了研究。结果表明:(1) 1990—2017年沙漠化程度处于逆转趋势,沙漠化土地面积共减少1 684.09 km~2,平均62.37 km~2/a的沙漠化土地得到有效的治理。(2)阶段性平均沙漠化指数1990—2000年(快速发展)为2.45,2000—2010年(快速逆转)为2.30;2010—2017年(稳定逆转)为2.01,沙漠化程度明显减轻。(3) 1990—2017年,极重度沙漠化土地重心向西迁移3.42 km;重度沙漠化土地重心向西北方向迁移8.80 km;中度沙漠化土地重心向西北偏移5.42 km;轻度沙漠化土地重心向东南方向延伸9.90 km。沙漠化土地重心由西向东依次为极重度沙漠化、重度沙漠化、中度沙漠化、轻度沙漠化,在沙漠化治理与防治过程中,应根据不同沙漠化土地类型而采取不同的治理对策,做到因地制宜,合理有效地改善沙区环境。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.     

Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater

Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Increase in auxiliary photoprotective photosynthetic pigments in wheat seedlings induced by Azospirillum brasilense

Inoculation of wheat seedlings with the plant growth-promoting bacterium Azospirillum brasilense Cd was immobilized in alginate microbeads and, without applying any stress, significantly increased the quantity of several photosynthetic pigments, such as chlorophyll a, chlorophyll b, and the auxiliary photoprotective pigments violaxanthin, zeaxanthin, antheroxanthin, lutein, neoxanthin, and β-carotene. This resulted in greener plants with no apparent visible stress. After monitoring the quantity of photosynthetic pigments for 4 weeks, we observed that inoculated plants had higher quantities of pigments in shoot and stem. The greatest difference in the quantity of all pigments between inoculated and noninoculated plants occurred in the first week of growth. Regardless of treatment, the quantity of pigments in stems was three to four times less than the quantity of these pigments in shoots. Application of Azospirillum, either as liquid inoculant or as alginate microbeads, did not alter the positive effect of the bacteria on pigment production or the positive response of the plants towards A. brasilense Cd inoculation.     

In-situ enrichment and analysis of atrazine-degrading microbial communities using atrazine-containing porous beads

We examined the community composition of microbes that colonized atrazine-containing beads buried in agricultural soils that differed in atrazine treatment history. Bacterial abundance was 5-40-fold greater in atrazine-fortified beads. In beads containing 20 mg atrazine kg⁻¹ buried in soil with a history of atrazine application (conditioned soil), the abundance of Actinobacteria increased approximately 80-fold whereas in control soil, Actinobacteria were enriched only 10-fold and the gamma-Proteobacteria and Planctomycetes increased by 60- and 25-fold, respectively. The gamma-Proteobacteria were enriched by 120- and 230-fold in beads containing 200 mg atrazine kg⁻¹ in conditioned and control soil, respectively. The results demonstrate that BioSep^® beads are a suitable matrix for recruiting a diverse subset of the bacterial community involved in atrazine degradation.