模拟降雨条件下3种类型土壤氮磷钾养分流失量的比较

通过模拟降雨试验方法,研究比较了褐土、棕壤与红壤氮磷钾养分流失量。结果表明:在模拟降雨条件下,3种类型土壤中褐土径流量及产沙量最小,红壤最大;土壤全氮、有效磷、速效钾养分随径流流失量占到流失总量的77.27%~99.79%,径流是土壤养分流失的主要驱动力;红壤全氮、有效磷、速效钾养分流失总量最大,褐土最小,棕壤与褐土相比高出4.70%~41.01%,比红壤减少0.30%~17.69%。土壤类型及性质不同使土壤养分流失量存在根本差异,有效地改良土壤,控制及减少径流与泥沙流失是防治土壤养分流失的关键。     

典型石漠化地区不同植被类型地表水土流失特征研究

在典型喀斯特石漠化地区广西凌云县设置径流小区,通过对不同植被类型地表径流及养分流失观测与分析,结果表明,喀斯特石漠化地区,在降雨历时短且大雨以上强度的降雨条件下存在地表径流,单次径流系数平均值在1.5%～13.8%之间,年平均径流量为75.86 mm.地表径流量与每次降雨量之间具有显著的相关性,其相关系数在0.896 7～0.947 5之间.不同植被类型间年径流量差异极显著,农耕地产生的年径流量最大,达122.75 mm,灌木林地产生的年径流量最小,达54.08 mm.径流中泥沙浓度整体表现出春秋季浓度高,夏季浓度低的趋势.不同植被类型间的侵蚀模数差异极显著,侵蚀模数平均达到45.88 t/km2·a,属微度侵蚀.耕作加剧了土壤扰动,对土壤流失有显著的影响,农耕地土壤侵蚀模数(98.91 t/km2·a)最大,灌木林地土壤流失量(5.42t/km2·a)最小.径流中全N浓度呈现出随时间而下降的趋势,全P、全K浓度呈现出春秋季高、夏季低的趋势.不同植被类型间流失全N、全P、全K总量差异极显著,植被能够有效减少地表径流及养分的损失,在该地区应该促进植被恢复.     

不同治理措施在红壤坡耕地的水土保持效益

在云南省抚仙湖流域澄江尖山河小流域坡耕地建立了野外标准径流小区,并布设了1.2m宽等高反坡阶和2.0m宽草带两种坡耕地水土保持措施,观测次降雨的地表径流量和土壤流失量,并与原状坡耕地进行对比,分析两种措施的水土保持效益。结果表明:(1)两种措施之间的地表径流量和土壤流失量差异性均显著。修筑等高反坡阶的地表径流深为113.64mm,比原状坡耕地减少了61.9%,土壤流失量为714.7t/km2,比原状坡耕地减少了77.4%;布设草带的地表径流深为82.76mm,比原状坡耕地减少了72.2%,土壤流失量为370.1t/km2,比原状坡耕地减少了88.3%。(2)两种措施之间的减流和减沙效益差异性均显著,等高反坡阶的减流和减沙效益指数平均分别达0.57和0.97,草带的减流和减沙效益指数平均分别达0.79和0.76。(3)两种措施均大幅削减了地表径流和泥沙的氮、磷养分输出总量,发挥了较好的保肥作用。与原状坡耕地相比,等高反坡阶对总氮削减率为81.9%,对总磷削减率为44.3%;草带对总氮削减率为74.7%,对总磷削减率为83.7%。     

辽宁省不同耕作方式对坡耕地水土及氮磷养分流失的影响效果

在天然降雨条件下,研究传统耕作、免耕、免耕秸秆覆盖、横垄4种耕作方式对坡耕地水土流失和养分流失的影响效果。结果表明:与传统耕作相比,其他3种耕作方式均能减少水土流失,产流量分别较之减少19.3%,27.1%,31.8%,泥沙量对应减少12.4%,21.5%,57.8%;各耕作小区径流中养分流失量差异显著;泥沙中全磷流失特征为T1>T3>T2>T4,其他耕作小区比传统耕作小区减少流失依次为8.6%,5.1%,12.1%;泥沙中的全氮流失特征为T1>T2>T3>T4,其他耕作小区比传统耕作小区减少流失依次为6.4%,10.3%,34.3%。坡耕地土壤侵蚀量与径流量呈显著相关。     

横垄耕作的面源污染截留效应研究

为了解横垄耕作的面源污染截留效应,选取吉林省长春市莫家沟小流域横垄耕作坡耕地为研究区,应用210Pbex核素示踪技术得到研究区土壤侵蚀模数为2 268 t/(km2.a),吸附态氮、磷流失负荷分别为4 889、2 022 kg/a;运用RU-SLE2.0模型,模拟在同等立地条件下顺坡耕作土壤侵蚀模数约为6 200 t/(km2.a)。对比结果表明:横垄耕作较顺坡耕作可减少约63%的土壤流失量及随土壤流失的吸附态氮磷负荷。     

赣北第四纪红壤坡耕地水土及氮磷流失特征

坡耕地水土及养分流失严重,该研究于2011年利用赣北第四纪红壤区野外径流小区定位观测试验数据,分析坡耕地水土及氮、磷、有机质流失特征。结果表明：地表产流产沙为裸露地最高、顺坡耕作和顺坡+植物篱次之,横坡耕作最小,横坡耕作比顺坡耕作减少径流62.71%、减少土壤侵蚀82.9%;坡耕地径流携带的可溶性氮、铵氮、硝态氮、可溶性磷的流失量都表现为裸地最大,横坡耕作最小;坡耕地泥沙携带的全氮、全磷、碱解氮、速效磷的流失量表现为裸地最大,横坡耕作最小;坡耕地可溶性氮中以有机氮流失为主,无机氮中以铵氮流失为主,泥沙中磷的流失主要以泥沙结合态流失。该研究可为坡耕地水土流失和面源污染防治提供科学依据。     

退耕还林后榆林市土壤侵蚀和养分流失功效研究

为了研究退耕还林后植被覆盖变化对黄土高原地区土壤侵蚀的影响,利用RUSLE土壤侵蚀模型结合RS、GIS技术估算了陕西省榆林市2000—2013年土壤侵蚀模数。结果表明,2000年以来NDVI从0.20增加到0.33,表现出东南部增长快于西北部的空间特征。降雨量最小和最大年份是2000年和2001年,对应的土壤侵蚀模数分别为2 071.97t/(km~2·a)和8 968.82t/(km~2·a)。在模拟最大和最小降雨条件下,2013年土壤侵蚀模数分别为1 218t/(km~2·a)和5 375t/(km~2·a),土壤流失总量比2000年和2001年分别减少了40%和41%,约0.35×10~8 t和1.52×10~8 t。随着侵蚀量的减少,土壤养分流失得到了有效控制,2013年比2002年土壤有机质、全氮、碱解氮、速效磷和速效钾含量累计减少562 049.65t。退耕还林后,榆林市土壤侵蚀呈现总量减少、侵蚀强度降低的趋势,表明退耕还林政策取得了明显的水土保持效益。     

重庆南平镇岩溶槽谷区不同土地利用类型地表水土流失

研究岩溶区水土流失特征有助于更好地开展岩溶地区水土保持,防止石漠化。通过在岩溶区不同土地利用类型布设9个径流场,利用2008-01－2010-08野外雨季的监测资料,得到岩溶区地表水土流失特征。结果表明：速效钾在土壤中易被淋失,磷富集度平均值最低,全氮、水解氮、有机质富集度的平均含量居中。从土地利用类型来看,富集度表现明显的是坡耕地（自然坡耕地强于移土培肥坡耕地）,其次是林地,金银花地和草地富集度最低。根据相关系数可知淤泥养分含量与降雨强度呈极显著相关关系,淤泥养分含量与降雨量成正相关,但是相关性差。淤泥养分流失总量是通过泥沙量与淤泥养分含量来共同体现的。土壤侵蚀模数从大到小的顺序依次为自然坡耕地>移土培肥坡耕地>草地>金银花地 >林地。岩溶区并不是每场降雨都要产生径流,主要是大雨尤其是暴雨才生产径流。岩溶区水土流失径流系数平均值在2.31%～14.72%。该研究有助于更好地理解岩溶区水土流失特征,为治理岩溶区水土流失提供科学依据。     

水平阶影响坡地产流产沙及氮磷流失的试验研究

选取我国西南部抚仙湖流域典型小流域——尖山河流域为试验区,在天然降雨条件下,研究有、无水平阶作为拦水带对红壤坡地产流产沙及土壤氮磷素流失的影响。结果表明:与无水平阶相比较,水平阶具有显著降低产流、减少产沙的作用,可使径流量和产沙量分别减少67.9%,79.5%;水平阶使径流中总氮和氨氮浓度以及泥沙中全氮和速效磷的浓度增加,使径流中的总磷浓度及泥沙中的全氮和速效磷浓度降低;水平阶使各形态的氮磷素输出量均显著减少;水平阶使坡耕地氮磷素流失总量分别减少了53.47%和86.83%。其中,泥沙结合态氮、磷素分别减少了30.89%和84.99%,随径流流失量分别减少了22.58%和1.84%。红壤坡耕地在无水平阶措施下,土壤氮素流失以泥沙结合态为主;在水平阶措施下以径流流失为主,但磷素始终都以泥沙结合态流失为主。综上所述,坡耕地推行水平阶作为拦水带,对南方降雨丰沛地区,是提高土地生产力,减少水土流失及面源污染的行之有效的方法。     

不同雨强条件下红壤坡地养分流失特征研究

采用人工模拟降雨装置 ,对红壤坡地养分流失特征进行了试验研究 ,结果表明 :在雨强较大情况下 ,土壤养分以泥沙形式随径流迁移 ;当雨强较小时 ,随径流迁移的可溶态养分流失量占流失泥沙养分量的比例较高 ,土壤养分流失氮、磷、钾分别达到 5 3.12 % ,2 3.1% ,2 1.5 % ;不同形态的养分在流失泥沙中均有养分富集现象 ,但富集率各不相同 ;土壤养分流失量与雨强及泥沙流失量呈正相关关系。     

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。     

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.     

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.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.     

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,     

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,     

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,     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

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.