Episodic rewetting enhances carbon and nitrogen release from chaparral soils

The short-term pulse of carbon (C) and nitrogen (N) mineralization that accompanies the wetting of dry soils may dominate annual C and N production in many arid and semi-arid environments characterized by seasonal transitions. We used a laboratory incubation to evaluate the impact of short-term fluctuations in soil moisture on long-term carbon and nitrogen dynamics, and the degree to which rewetting enhances C and N release. Following repeated drying and rewetting of chaparral soils, cumulative CO₂ release in rewet soils was 2.2-3.7 times greater than from soils maintained at equivalent mean soil moisture and represented 12-18% of the total soil C pool. Rewetting frequency did not affect cumulative CO₂ release but did enhance N turnover, and net N mineralization and nitrification increased with rewetting in spite of significant reductions in nitrification potential. Litter addition decreased inorganic N release but enhanced dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) from dry soils, indicating the potential importance of a litter-derived pulse to short-term nutrient dynamics.     

盐胁迫对普通小麦-大赖草异附加系种子萌发及幼苗生长的影响

以中国春和普通小麦-大赖草异附加系DA5Lr、DA7Lr、AddLr11″、AddLr2″DA7Lr#1S和DA5Lr#1L为试材,研究了NaCl对其种子萌发和幼苗生长的影响。结果表明,随着NaCl浓度的升高,它们的发芽率、发芽势、发芽指数、活力指数、芽长、单株鲜、干重及胚芽鞘相对生长率均受到抑制,而DA7Lr材料受抑制程度明显低于其它材料。在100mmol/LNaCl胁迫下,DA7Lr的种子发芽率下降率、发芽势下降率、发芽指数下降率、活力指数下降率和芽长下降率分别为22.92%、16.28%、57.38%、69.39%和25.54%,分别低于中国春种子32.64%、49.78%、23.25%、4.31%和10.66%;100mmol/LNaCl胁迫48h,DA7Lr种子胚芽鞘相对生长率为0.267mm/h,比中国春提高117.1%;100mmol/LNaCl胁迫下,第9天调查结果,DA7Lr幼苗单株鲜、干重分别为76.4mg和10.6mg,分别比中国春增加7.1%和82.8%,表现出了较高的耐盐性。     

小麦背景下冰草6P染色体特异EST标记的开发

小麦-冰草[Agropyron cristatum (L. ) Gaertn.] 6P附加系普冰4844-12具有多粒等可用于小麦改良的优异基因。为高效率检测由小麦-冰草6P附加系衍生的易位系和渐渗系,以普冰4844-12及其亲本普通小麦Fukuhokomugi和冰草Z559 (2n=4x=28, PPPP)为材料,通过对冰草转录组测序获得的EST序列设计的P基因组EST分子标记引物,筛选在普通小麦背景下的6P染色体特异分子标记。结果从1 453对P基因组EST引物中筛选出130对小麦-冰草6P附加系特异标记引物。进而将这些特异标记与NCBI nr蛋白质数据库及小麦EST序列进行了比对,发现4条冰草EST序列的功能注释与抗病、抗逆相关;36条冰草EST与已经定位的小麦EST具有较高的相似性,其中33条(91.67%)位于小麦第6部分同源群染色体。为了进一步验证这些标记的特异性,分别对其中4个具有功能注释的EST标记在中国春等7个普通小麦背景下和随机选择的5个标记在小麦-冰草6P易位系背景下进行了检测,结果证明其确实可用于检测6P染色体。这些冰草6P染色体特异标记的开发为大规模地鉴定小麦-冰草衍生后代中P染色质成分奠定了基础。     

小麦-冰草附加系与小麦-杀配子染色体附加系杂交F1的细胞学特性

以小麦-冰草附加系与中国春-柱穗山羊草杀配子染色体2C附加系杂交，对杂交F1的形态学及细胞学特性进行了研究，为利用杀配子染色体诱导小麦ABD组和冰草P组染色体变异，创造小麦-冰草染色体易位系奠定基础。对8个小麦-冰草二体附加系同中国春-杀配子染色体附加系杂交F1的形态学、育性以及细胞学特性的观察结果表明，小麦-冰草不同附加系P染色体的传递能力存在差异。F₁花粉母细胞减数分裂中存在染色体异常，平均35.3%的细胞含3个以上的单价体，74.0%的四分体含有微核，20.3%和23.8%的细胞含有染色体断片和桥，在某些组合中有多价体、四分体多裂和退化现象。杀配子染色体的诱变在配子形成的过程中已经开始发生作用。不同杂交组合之间F₁植株自交结实率为51.67%~71.37%，反映出杀配子染色体2C在小麦-冰草不同附加系背景下对其育性的影响存在差异。     

盐酸羟胺促进分级Fenton氧化土壤长链原油的试验研究

H₂O₂分次投加可以提高石油烃(total petroleum hydrocarbons,TPH)去除率,本试验选用900 mmol/L H₂O₂分3次投加的方式进行分级Fenton氧化修复长链原油污染土壤。在Fe²⁺、固相铁、Fe²⁺+盐酸羟胺、固相铁+盐酸羟胺4种催化体系下进行试验,发现在向Fe²⁺体系和固相铁体系加入盐酸羟胺后,后两级反应·OH强度明显增强,是未加入盐酸羟胺体系下的3倍～4倍,TPH及长链烃氧化量也大幅提高。采用向Fenton体系中加入盐酸羟胺的方式,克服了分级Fenton氧化过程中由于Fe²⁺不足导致·OH强度较第一级显著降低、TPH及长链烃氧化量大幅下降的缺陷,促进了后两级反应过程中·OH的产生,从而大大提高了后两级TPH及长链烃的去除效果,使后两级去除效果与第一级接近,能够维持在较高水平,为急需短时间进行的土壤修复提供了一定的理论依据。     

多枝赖草及其转育后代对大麦黄矮病毒PAV和GAV株系的抗性研究

 本文针对大麦黄矮病毒(BYDV) PAV和GAV株系,采用生物学和血清学(ELISA)相结合的鉴定方法,对多枝赖草以及它与普通小麦杂交获得的二体附加系Line24等材料进行抗性测定。首次证明了多枝赖草对我国BYDV-PAV和GAV株系免疫或高抗,而普通小麦-多枝赖草二体附加系Line24以及2个易位系高耐这2种株系。     

Impacts of conservation agriculture on total soil organic carbon retention potential under an irrigated agro-ecosystem of the western Indo-Gangetic Plains

Sequestration of C in arable soils has been considered as a potential mechanism to mitigate the elevated levels of atmospheric greenhouse gases. We evaluated impacts of conservation agriculture on change in total soil organic C (SOC) and relationship between C addition and storage in a sandy loam soil of the Indo-Gangetic Plains. Cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) crops were grown during the first three years (2008–2011) and in the last year, maize (Zea mays L.), wheat and green gram (Vigna radiate L.) were cultivated. Results indicate the plots under zero tillage with bed planting (ZT-B) and zero tillage with flat planting (ZT-F) had nearly 28 and 26% higher total SOC stock compared with conventional tillage and bed planting (CT-B) (∼5.5 Mg ha⁻¹) in the 0–5 cm soil layer. Plots under ZT-B and ZT-F contained higher total SOC stocks in the 0–5 and 5–15 cm soil layers than CT-B plots. Although there were significant variations in total SOC stocks in the surface layers, SOC stocks were similar under all treatments in the 0–30 cm soil layer. Residue management had no impact on SOC stocks in all layers, despite plots under cotton/maize + wheat residue (C/M+ W RES) contained ∼13% higher total SOC concentration than no residue treated plots (N RES; ∼7.6 g kg⁻¹) in the 0–5 cm layer. Hence, tillage and residue management interaction effects were not significant. Although CT-B and ZT-F had similar maize aboveground biomass yields, CT-F treated plots yielded 16% less maize biomass than CT-B plots. However, both wheat and green gram (2012) yields were not affected by tillage. Plots under C/M + W RES had ∼17, 13, 13 and 32% higher mean cotton, maize, wheat and green gram aboveground biomass yields than N RES plots, yielding ∼16% higher estimated root (and rhizodeposition) C input in the 0–30 cm soil layer than N RES plots. About 9.3% of the gross C input contributed towards the increase in SOC content under the residue treated plots. However, ∼7.6 and 10.2% of the gross C input contributed towards the increase in SOC content under CT and ZT, respectively. Thus, both ZT and partial or full residue retention is recommended for higher soil C retention and sustained crop productivity.     

短期氮磷添加对荒漠草原土壤活性有机碳的影响

以干旱、半干旱地区荒漠草原土壤为研究对象,研究氮(N)、磷(P)添加对荒漠草原0~30 cm土层土壤溶解性有机碳、微生物生物量碳和易氧化有机碳含量及有效率、土壤碳库管理指数(CPMI)、敏感指数(SI)的影响,探讨N、P添加后土壤溶解性有机碳、微生物生物量碳和易氧化有机碳对碳库管理指数的表征作用。结果表明,N添加、P添加或NP共同添加对荒漠草原0~20 cm土壤溶解性有机碳的累积有显著促进作用,但对0~20 cm土壤微生物生物量碳无显著影响。NP共同添加显著增加0~10 cm土层土壤易氧化有机碳。0~30 cm土层N、P添加的土壤溶解性有机碳的各项敏感指数均高于易氧化有机碳,说明土壤溶解性有机碳对短期N、P添加反应最敏感,因此可作为荒漠草原短期N、P添加对土壤有机碳变化的指示物。短期N、P添加能提高碳库管理指数,增加土壤有机质含量,促进荒漠草原土壤恢复。     

碳酸钾添加比例对玉米秸秆生物炭表面特性的影响

在600 oC的热解温度下通过添加不同比例的碳酸钾制备活性生物炭。对比分析了碳酸钾活化生物炭（KBC）和普通生物炭（BC）的特性,包括生物炭红外光谱特征、表面官能团、比表面积和孔径分布及吸附动力学过程等。结果表明,经碳酸钾活化的生物炭比表面积大为提高,最高达到566 m2?g-1（KBC-2-600）,而普通生物炭（BC600）的比表面积仅为86.8 m2?g-1,KBC600系列的介孔孔容和微孔孔容均显著的高于BC600,介孔孔容平均扩大了16倍,微孔孔容平均扩大了4倍,同时提高了微孔率。经碳酸钾活化的生物炭表面官能团的数量和饱和度发生改变,在1 256 cm-1～3 414 cm-1处,官能团的总体含量均低于普通生物炭,酯类羰基消失,形成氢键的能力减弱,非饱和醚类增加,芳香性和非极性提高,此表面特征更有利于吸附非极性芳香类污染物。对萘吸附的动力学实验表明,BC600和KBC-4-600均适合拟二级动力学模型拟合,经碳酸钾活化后,生物炭的吸附性能提高,颗粒内扩散模型拟合结果表明,经碳酸钾活化后,生物炭内部孔隙复杂程度和数量均得到提高。碳酸钾活化的生物炭表面性质优良,作为高效吸附剂用于修复非极性芳香类污染有很大潜力。