我国喀斯特断陷盆地石漠化区植物群落构建机制研究

喀斯特断陷盆地是我国石漠化综合治理8大喀斯特类型中治理成效最低、治理难度最大的区域，面临石漠化严重、干旱频发、植被恢复难等突出问题。文中针对水分是影响喀斯特断陷盆地石漠化治理与植被恢复成效最关键的限制因素，综合分析了国内外水分梯度差异与植物群落构建机制研究动态与发展趋势；提出利用日趋成熟的水分脆弱性评价方法，通过建立基于耦合暴露度、敏感性及适应性的水资源脆弱性评价指标体系，以满足遥感影像分辨率和植物群落调查样地大小的评价单元进行水分脆弱性评估；在建立物种库—功能性状—生境特征数据库的基础上，提出基于功能性状差异进行喀斯特断陷盆地植物群落机制构建的研究方案。提出的研究方案有望解决喀斯特断陷盆地石漠化区水分梯度特征与分布格局、自然植物群落组配规律及其生境特征、水分梯度与生境要素对植物群落特征及功能性状组成的影响规律等关键科学问题，可为不同脆弱生态区植被恢复群落构建机制研究提供重要参考和借鉴。     

包膜含缩节胺氯化钾对棉花产量及土壤钾素的影响

棉花是具无限生长特性的喜钾作物，为解决其生育期内多次追施钾肥和叶面喷施缩节胺的用工问题，实现轻简化种植目标，研究包膜含缩节胺氯化钾对棉花产量、经济效益和土壤钾素变化特征的影响。试验设5个处理，分别为一次基施180 kg?hm-2包膜含缩节胺氯化钾（CRKMC）、减少30%钾素用量（126 kg?hm-2）的包膜含缩节胺氯化钾（70%CRKMC）、基施180 kg·hm^-2普通包膜氯化钾（CRK）、分次施用180 kg?hm-2普通氯化钾（KCl）和对照（CK，不施钾肥），后三个处理叶面喷施三次缩节胺。结果表明：等量施钾条件下，CRKMC和CRK较KCl籽棉产量分别增加8.81%和9.36%，经济效益分别增加15.53%和12.86%，70%CRKMC较KCl增产6.53%，增加净收入13.64%。CRKMC抑制棉花盛花期前的株高，提高后期株高、茎粗和叶绿素含量，使生物量较KCl增加18.56%~24.98%，提高钾素吸收量，表观利用率增加25.06~38.83个百分点。CRKMC中的钾素和缩节胺在土壤中呈“先慢后快而后趋于平缓”的规律，释放高峰出现在盛花期至始絮期，显著提高蕾期以后土壤中的速效钾含量。因此，土壤基施包膜含缩节胺氯化钾，可合理协调棉花生长势指标，满足钾素吸收需求，减少30%用量仍有较高的经济效益和钾素利用率，实现了缩节胺和钾素在同一时空条件下的一体化调控，有助于棉花减肥、高产和轻简化种植。     

The Application of GIS in Small Watershed Classification in Loess Plateau

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铅胁迫对金丝草生长及生理生化的影响

采用土培方法,探究不同梯度铅胁迫(0、1000、2000和3000 mg·kg^-1)对金丝草生长形态、体内抗氧化系统和渗透调节物质的影响。结果表明:低浓度(1000 mg·kg^-1)处理会诱导金丝草叶片过氧化物酶(POD)活性、可溶性蛋白(SP)含量和根系抗超氧阴离子自由基活力(ASAFR)、可溶性糖(SS)及脯氨酸(Pro)含量增加,使得金丝草植株总抗氧化能力(T-AOC)处于较高水平,促进了金丝草株高、叶长和生物量的增加。随胁迫浓度增加,高浓度(2000~3000 mg·kg^-1)处理下,金丝草叶片和根系丙二醛(MDA)含量迅速增加,株高、叶长、叶面积和生物量下降,生长受到抑制。但金丝草通过增强叶片和根系POD、过氧化氢酶(CAT)活性来抵御过氧化作用,提高可溶性蛋白和可溶性糖含量维持细胞正常运作,增加根系生物量占比来加强根系发育,一定程度适应了高浓度铅胁迫。综上表明,金丝草主要通过叶片和根系不同抗氧化酶差异化响应、提高渗透调节物质含量,提升金丝草植株总抗氧化能力等途径来提高Pb耐性,对Pb污染矿区植物修复有较大潜力。     

Sewage sludge processing determines its impact on soil microbial community structure and function

Composting and thermal drying are amongst the most commonly used post-digestion processes for allowing sanitation and biological stabilization of sewage sludge from municipal treatment plants, and making it suitable as soil conditioner for use in agriculture. To assess the impact of sludge-derived materials on soil microbial properties, fresh (LAF), composted (LAC) and thermally dried (LAT) sludge fractions, each resulting from a different post-treatment process of a same aerobically digested sewage sludge, were added at 1% (w/w) application rate on two contrasting (a loam and a loamy sand) soils and incubated under laboratory conditions for 28 days. Soil respiration, microbial ATP content, hydrolytic activities and arginine ammonification rate were monitored throughout the incubation period. Results showed that soil biochemical variables, including the metabolic quotient (qCO₂), were markedly stimulated after sludge application, and the magnitude of this stimulatory effect was dependent on sludge type (precisely LAT > LAF > LAC), but not on soil type. This effect was related to the content of stable organic matter, which was lower in LAT. Genetic fingerprinting by PCR–DGGE revealed that compositional shifts of soil bacterial and, at greater extent, actinobacterial communities were responsive to the amendment with a differing sludge fraction. The observed time-dependent changes in the DGGE profiles of amended soils reflected the microbial turnover dependent on the sludge nutrient input, whereas no indications of adverse effects of sludge-borne contaminants were noted. Our findings indicate that composting rather thermal drying can represent a more appropriate post-digestion process to make sewage sludge suitable for use as soil conditioner in agriculture.     

Micro-scale heterogeneity in urban forest soils affects fine root foraging by ornamental seedlings of Buddhist pine and Northeast yew

Urban soils are frequently characterized by a strong heterogeneity caused by intense anthropogenic activity and land use changes. Soil heterogeneity is commonly known to affect tree root development, but little has been detected concerning root foraging by ornamental trees in heterogeneous urban soils at micro-scale. In this study, Buddhist pine [Podocarpus macrophyllus (Thunb.) D. Don] and Northeast yew (Taxus cuspidata S. et Z.) were selected as ornamental tree species for a two-year study. In the first-year, seedlings were cultured under contrasting photoperiods to generate different morphologies. In the second year, seedlings were transplanted to pots filled with soils collected from an urban forest. Controlled-release fertilizers (N-P₂O₅-K₂O, 14-13-13) were evenly broadcasted to a half patch of the pot (heterogeneity) or to both halves (homogeneity) on the surface 5 cm beneath the pot-top at the rate of 0.135 g N seedling⁻¹. In the fertilized heterogeneous patch, larger Buddhist pine seedlings had greater dry weight, length, surface area, volume, number of tips, and morphological foraging-precision in fine roots. Compared to Northeast yew seedlings under natural photoperiod in the first year, those under the extended photoperiod had larger size, greater fine root biomass, and length but lower foraging-precision in the second year. N and P concentrations in second-year fine roots mainly increased with the availability of patches generated by fertilization for both species. In conclusion, the ability to forage for nutrients by ornamental tree seedlings in heterogeneous urban forest soils was species-specific. Buddhist pine seedlings had higher foraging precision in heterogeneous urban soils than Northeast yew seedlings due to their response to the extended photoperiod during culture.     

黄土坡面结皮对土壤水稳性团聚体的稳定性和可蚀性的影响

为了探析微地形下土壤受雨滴打击后产生的结皮类型及团聚体组成差异。通过人工模拟降雨,研究坡面不同位置的结皮土壤水稳性团聚体分布特征、稳定性以及土壤可蚀性的变化情况。结果表明：（1）土壤水稳性团聚体以大团聚体（粒径>0.25 mm）含量为指标,原状土、结构结皮、沉积结皮、过渡带结皮>0.25 mm粒级的水稳性团聚体分别占37.28%、43.58%、36.69%、40.34%;（2）以降雨历时5 min为例,原状土、结构结皮、沉积结皮、过渡带结皮的水稳性团聚体的破坏率分别为：51.49%、46.00%、62.76%、51.02%;（3）原状土、结构结皮、沉积结皮、过渡带结皮的水稳性团聚体的平均重量直径分别为：0.15、0.20、0.14、0.17 mm;（4）原状土、结构结皮、沉积结皮、过渡带结皮土壤可蚀性K值的大小分别为：0.223、0.200、0.229、0.205。微地形下产生结皮差异使得水稳性团聚体分布有所区别,因此土壤水稳性团聚体稳定性和可蚀性存在差异。     

尿素类型与灌溉管理对玉米节水保肥的影响

水分和氮素管理对提高作物产量具有重要作用。笔者研究尿素类型与灌溉管理对玉米节水保肥的影响以达到玉米高氮肥利用效率和高产田的生产目标。本研究在2016—2017年开展2年完全随机区组设计试验,讨论了尿素类型（普通尿素和控释尿素）及灌溉对玉米土壤和氮素利用的影响。每种尿素类型设置2种氮素水平,分别为75、150 kg N/hm ²,以不施氮肥为对照。水分设置2种灌溉水平,分别为全生育期不灌水和灌浆阶段灌水85 mm。结果表明：在灌溉与施氮水平相同下,0~40 cm土层应用控释尿素处理氮含量较高,但在更深的土壤层低于普通尿素处理;相对于不灌溉,灌溉增加了硝态氮的损失,但施用控释尿素的处理硝态氮损失低于施用普通尿素处理;灌溉条件下施用控释尿素可以提高玉米氮素吸收,并使更多的氮向籽粒中转移;与普通尿素相比,控释尿素提高了氮肥利用率,降低土壤对氮需求的依赖。控释尿素低氮的释放可以减少硝态氮在土壤中的存留时间而迅速被玉米吸收,从而降低硝态氮的损失风险,提高了土壤氮肥利用效率。综上,控释尿素与少量灌溉相结合适用于华北半湿润地区达到玉米高氮肥利用效率和高产田的生产目标。     

胶莱盆地北部风尘堆积物光释光年代序列研究

山东省胶莱盆地的高岗部位存在大量的风尘堆积物,对其年代的研究一直存在较大的分歧.对胶莱盆地的潍坊前埠下风尘堆积剖面进行了系统的光释光年代测试,并与其以北16.9km的昌邑县徐林庄剖面的年代进行了对比,初步建立了胶莱盆地风尘堆积的光释光年代序列,研究表明该区风尘堆积主要是晚第四纪以来形成的堆积物.     

Contribution of green manure legumes to nitrogen dynamics in traditional winter wheat cropping system in the Loess Plateau of China

Excessive application of N fertilizer in pursuit of higher yields is common due to poor soil fertility and low crop productivity. However, this practice causes serious soil depletion and N loss in the traditional wheat cropping system in the Loess Plateau of China. Growing summer legumes as the green manure (GM) crop is a viable solution because of its unique ability to fix atmospheric N₂. Actually, little is known about the contribution of GM N to grain and N utilization in the subsequent crop. Therefore, we conducted a four-year field experiment with four winter wheat-based rotations (summer fallow-wheat, Huai bean–wheat, soybean–wheat, and mung bean–wheat) and four nitrogen fertilizer rates applied to wheat (0, 108, 135, and 162 kg N/ha) to investigate the fate of GM nitrogen via decomposition, utilization by wheat, and contribution to grain production and nitrogen economy through GM legumes. Here we showed that GM legumes accumulated 53–76 kg N/ha per year. After decomposing for approximately one year, more than 32 kg N/ha was released from GM legumes. The amount of nitrogen released via GM decomposition that was subsequently utilized by wheat was 7–27 kg N/ha. Incorporation of GM legumes effectively replaced 13–48% (average 31%) of the applied mineral nitrogen fertilizer. Additionally, the GM approach during the fallow period reduced the risk of nitrate-N leaching to depths of 0–100 cm and 100–200 cm by 4.8 and 19.6 kg N/ha, respectively. The soil nitrogen pool was effectively improved by incorporation of GM legumes at the times of wheat sowing. Cultivation of leguminous GM during summer is a better option than bare fallow to maintain the soil nitrogen pool, and decrease the rates required for N fertilization not only in the Loess Plateau of China but also in other similar dryland regions worldwide.