Effects of gravel mulch on aeolian transport:a field wind tunnel simulation

The shape,size and coverage of gravels have significant impacts on aeolian sand transport.This study provided an understanding of aeolian transport over the gravel mulching surfaces at different wind velocities by means of a mobile wind tunnel simulation.The tested gravel coverage increased from 5% to 80%,with a progressive increment of 5%.The gravels used in the experiments have three sizes in diameter.Wind velocities were measured using 10 sand-proof pitot-static probes,and mean velocity fields were obtained and discussed.The results showed that mean velocity fields obtained over different gravel mulches were similar.The analysis of wind speed patterns revealed an inherent link between gravel mulches and mean airflow characteristics on the gravel surfaces.The optimal gravel coverage is considered to be the critical level above or below which aeolian transport characteristics differ strongly.According to the present study,the optimal gravel coverage was found to be around 30% or 40%.Threshold velocity linearly increased with gravel coverage.Sand transport rate first increased with height above the wind tunnel floor(Hf),reaching a peak at some midpoint,and then decreased.     

Evidence on the response of Patagonian forage grasses to the mulching effect of recent tephra deposits in Argentina

In Patagonia, arid and semiarid lands are being affected both by inappropriate management practices, which are leading to degradation, and by volcanic activity, whose effects are still unclear. This study aimed to test whether superficial deposition of volcanic tephra could benefit two of the most prominent Patagonian forage grass species (Poa ligularis and Pappostipa speciosa var. speciosa). Pots with P. ligularis and P. speciosa were kept under wet (W) and dry (D) conditions in the presence (T+) or absence (T?) of tephra for 105 days, and then were all well-watered. We determined the effects of tephra on soil water retention and conservation, soil moisture content (% v/v), plant growth, stomatal conductance (gs), and gs recovery capacity. The water regime significantly affected both species performance and gs. The presence of tephra increased soil water conservation, soil moisture content in wet conditions, and P. ligularis gs in wet conditions, and decreased senescence in dry conditions (9% in P. ligularis and 16% in P. speciosa). The presence of tephra allowed roots to grow in 8/10 and 2/10 pots in W conditions for P. ligularis and P. speciosa, respectively, and in only 1/10 pots in D conditions, only for P. ligularis. Tephra was also associated with gs recovery after dry conditions. Poa ligularis was more positively affected by tephra than P. speciosa, probably because P. ligularis has higher phenotypic plasticity. The positive effects of tephra may increase the resilience and resistance of P. speciosa and P. ligularis to periods of water shortage.     

黄土地表生物结皮对土壤贮水性能及水分入渗特征的影响

采用双环法对山西省偏关县3种结皮覆盖下(苔藓藻结皮、藻结皮和薄层藻结皮)土壤的贮水性能和渗透特征进行了对比研究.结果表明:不同结皮覆盖下土壤的贮水能力受结皮厚度和孔隙度状况的影响较大,0～10 cm土层饱和贮水量为502.69～525.80 t/hm2 ,滞留贮水量为169.71～198.29 t/hm2;初渗速率的变化范围为5. 19～11.10 mm/min,无结皮最高,苔藓藻结皮最低;稳渗速率变化范围为1.6 7～2.67 mm/min.采用的3种入渗模型(Kostiakov模型、Horton模型和Ph ilip模型)中Horton模型的拟合值更接近于实测值, 决定系数R2在0.98～0.99,更适用于描述本研究区具有生物结皮土壤的入渗特征.     

一种土壤调理剂对玉米幼苗抗旱性的影响

为研究新型高效土壤调理剂M3T对作物抗旱性的影响,开展水分胁迫下不同浓度M3T对盆栽玉米幼苗的抗旱性影响的试验。结果表明:添加M3T可增强土壤保水能力;M3T处理延长玉米幼苗的存活时间3~11天,增加玉米幼苗的株高和生物量;玉米幼苗体内叶绿素、丙二醛、脯氨酸、可溶性蛋白含量及过氧化物酶和超氧化歧化酶活性的动态测定结果表明,未加M3T的处理玉米幼苗最早感受到水分胁迫而产生生理生化反应,M3T处理的玉米幼苗出现水分胁迫反应延迟。干旱胁迫下,0.01%~0.03%M3T处理有利于玉米幼苗生长,0.04%~0.05%M3T处理增强了玉米幼苗抗旱性,其存活时间更长;0.02%~0.03%M3T处理下农作物在干旱胁迫下可正常生长发育,且具有较好的抗旱性,为较佳处理。     

秸秆还田对半干旱区农田土壤养分含量及玉米光合作用的影响

为了提升和保育辽西半干旱区农田土壤质量,采用盆栽试验的方式探讨了不同处理方式、不同用量玉米秸秆还田对土壤养分含量的影响。结果表明,秸秆还田后,其土壤含水量比对照组提高了3%~7%;有机质含量比对照组提高幅度为1.9%~19%;全氮含量比对照组提高幅度为0.7%~14.4%;速效磷含量比对照组提高了2.51~14.75 mg/kg;速效钾含量比对照组提高了7.33~188.07 mg/kg;碱解氮含量比对照组提高了8.46mg/kg;净光合速率比对照组提高了3~11.03 CO2μmol/(m2.s);秸秆还田可以缓解土壤碱化。     

多效唑和PVA对轻度干旱下多年生黑麦草幼苗抗旱性的影响

轻度干旱下,对聚乙烯醇(Polyvinyl alcohol,PVA)浸种预处理的多年生黑麦草(Lolium perenne L.)品种'旋风'的幼苗叶面喷施不同剂量(150、300、450 mg/m2)的多效唑,探讨PVA浸种及叶面喷施多效唑处理对多年生黑麦草生长及幼苗抗旱性的影响.结果表明:与对照相比,2%PVA浸种的多年生黑麦草成苗率提高0.13倍(P＜0.01),叶片相对含水量提高0.03倍(P＜0.05);2%PVA漫种 叶面喷施150 mg/m2多效唑处理的多年生黑麦草叶片相对合水量增加0.04倍,SOD、POD和CAT活性分别提高0.40、0.44和0.17倍,MDA含量降低51.58%.植株生长高度降低42.57%,差异均显著(P＜0.05),且比单独喷施多效唑、单一2%PVA漫种的抗旱效果显著;2%PVA浸种处理下,300～450 mg/m2多效唑缓解轻度干旱对黑麦草的胁迫作用明显或显著降低.综合效应表明,2%PVA浸种预处理 叶面喷施150 mg/m2多效唑处理能有效减轻水分匮乏对幼苗的胁迫并廷缓植株生长,处理效果最佳.     

Effects of artificially cultivated biological soil crusts on soil nutrients and biological activities in the Loess Plateau

Biological soil crusts （BSCs） play an important role in the early succession of vegetation restoration in the Loess Plateau, China. To evaluate the effects of artificially cultivated BSCs on the soil surface micro-envir- onment, we obtained natural moss crusts and moss-lichen crusts from the Loess Plateau of Shaanxi province, and subsequently inoculated and cultivated on horizontal and sloping surfaces of loess soil in a greenhouse. The chemical and biological properties of the subsoil under cultivated BSCs were determined after 10 weeks of cul- tivation. The results indicated that BSCs coverage was more than 65% after 10 weeks of cultivation. Moss crust coverage reached 40% after 5 weeks of cultivation. Compared with the control, soil organic matter and available nitrogen contents in moss crust with the horizontal treatments increased by 100.87% and 48.23%, respectively; increased by 67.56% and 52.17% with the sloping treatments, respectively; they also increased in moss-lichen crust with horizontal and sloping treatments, but there was no significant difference. Available phosphorus in cultivated BSCs was reduced, soil pH was lower and cationic exchange capacity was higher in cultivated BSCs than in the control. Alkaline phosphatase, urease and invertase activities were increased in artificially cultivated BSCs, and alkaline phosphatase activity in all cultivated BSCs was obviously higher than that in the control. Numbers of soil bacteria, fungi and actinomycetes were increased in the formation process of cultivated BSCs. These results indicate that BSCs could be formed rapidly in short-term cultivation and improve the mi- cro-environment of soil surface, which provides a scientific reference for vegetation restoration and ecological reconstruction in the Loess Plateau. China.     

土壤干旱对麦田燕麦孢囊线虫Heterodera avenae发生动态的影响

为明确土壤干旱对麦田燕麦孢囊线虫Heterodera avenae(Ha)发生动态的影响,于2014年分别对灌溉和非灌溉小区定期取样,通过对土壤中线虫的分离和小麦根组织中线虫的镜检,确定灌溉和非灌溉小区中Ha各虫态的发生密度。结果表明,与非灌溉小区相比,灌溉小区土壤中2龄幼虫和白色雌虫以及根组织中2、3或4龄幼虫的群体密度在4—5月均明显较高;尤其在4月,灌溉小区2龄幼虫平均孵出量和侵入量分别为3.0条/100 g土壤和19.0条/10 g根,而非灌溉小区的分别仅为0.6条/100 g土壤和1.0条/10 g根。在小麦生长期,灌溉小区的Ha群体密度略有增长,繁殖系数为1.04,而非灌溉小区的显著下降,繁殖系数仅为0.09。研究表明,土壤严重干旱能抑制Ha 2龄幼虫的孵出和侵入,减少3、4龄幼虫和白色雌虫发生数量,导致繁殖系数显著下降。     

土壤干旱对小麦叶片光合和氮素水平及其转运效率的影响

研究了两个冬小麦品种(济南17和鲁麦21)的叶片氮素含量动态变化及其转运效率对4个土壤水分水平分别占土壤最大持水量的75%～80%、55%～60%、40%～45%及30%～35%)的响应。结果表明:中度和严重土壤干旱显著降低了叶片相对含水量、叶绿素含量、光合速率、气孔导度、氮素含量和生物产量,但中度干旱提高了叶片氮素转运效率和籽粒蛋白质含量。尽管高蛋白小麦品种济南17叶片的氮素含量较低,但氮素转运效率较高,适度土壤干旱对其籽粒蛋白质的激发作用亦较强。表明适度土壤水分亏缺可促进叶片氮素向籽粒运转,有利于改善小麦品质。     

垄沟覆膜集雨系统膜垄保墒增温对马铃薯产量的影响

大田试验,观测半干旱黄土高原地区垄沟覆膜集雨系统中覆膜垄的增温保墒作用对马铃薯产量的影响.试验设4个处理,P30:30 cm宽垄覆膜,60 cm宽沟;P45:45 cm宽垄覆膜,60 cm宽沟;P60:60 cm宽垄覆膜,60cm宽沟;P0:裸地平作.结果表明,覆于垄上的地膜有提高垄下土壤温度和保持垄下土壤湿度的作用,集于沟中的部分降雨会渗透到垄下,形成降雨在沟中和垄下的分布.由于部分根系在膜垄下生长,从而使马铃薯受到地膜覆盖的增温保墒作用,生长迅速.P20、P45、P60的产量、水分利用效率显著高于裸地平作,而耗水量显著低于裸地平作.     

干旱指数及其在青海东部旱区特征分析上的应用

在土壤水分平衡关系分析的基础上,提出了分析和评估旱害的5项指标:贫水指数、凋萎指数、降水指数、综合指数和干旱指数,并依据干旱指数对乐都浅山地区1961～1999年的粮食生产进行了年型分类。结果为:39a间共发生特大旱1a,大旱年3a,中旱年19a,轻旱年11a,平水年5a;发生机率分别为2.6%、7.69%、48.72%、26.21%、12.82%。同时认为青海东部地区旱区作物需水和耗水参数矛盾突出,干旱几乎年年发生,具有明显的难以预测性、多变性和不可控性。     

花铃期干旱胁迫对不同棉花品种光合特性影响及抗旱性评价

以28份抗旱性不同的棉花品种为材料,通过大田花铃期水分胁迫,以抗旱系数和主成分分析综合评价各个棉花品种的抗旱水平,并对其评价和等级进行划分。结果表明,各个棉花品种在花铃期干旱胁迫下,各指标反应程度不同,其中叶绿素、净光合速率、水蒸汽压亏缺、气孔导度变化较明显,通过RI值聚类分析,将材料分成4个大类,第Ⅰ类为高抗型品种有C1470、ND359-5、新炮1号、新陆中39等18份品种;第Ⅱ类为中抗型的包括天合995、吉扎81、大铃棉、TM-1、10615-1、塔什干7号;第Ⅲ类为敏感型的包括新陆早1号、新石K7、鲁棉28;第Ⅳ为极敏感型的新陆早26。进一步利用逐步回归建立回归方程D=-1.496+0.775Ci+0.160Gs-0.020VPD+0.719Pn+0.799Tr-0.241WUE+0.663Chl(R2=0.996),筛选出7个指标,分别为Ci、Gs、VPD、A、Tr、WUE、Chl,各材料估计精度大于97.55%。     

半干旱区土地利用方式对土壤碳氮矿化的影响

通过研究云雾山草原自然保护区草地、农地、灌木林土壤有机碳和氮的含量和矿化特征,分析了半干旱黄土区不同土地利用方式对土壤碳氮循环的影响。结果表明,土壤有机碳和全氮平均含量在草地转变为农地后分别降低了53%和64%,在转变为灌木林地后分别降低了54%和44%。不同土地利用方式下土壤有机碳矿化速率均随土层深度的增加逐渐降低,降幅介于29%~46%之间;有机碳矿化比例则逐渐增加,增幅介于45%~67%之间。土壤氮素矿化速率、矿化比例和硝化速率均随土层加深逐渐降低,而且0~20 cm土层氮素矿化体现为硝化过程和铵态氮的固定作用,且硝化过程占主导作用;40~80 cm土层硝化过程和铵化过程的比例接近,表明深层土壤氮素矿化由硝化过程和铵化过程共同主导。草地转化为农地和灌木林地后有机碳矿化速率显著降低,其降低幅度随土层加深逐渐减小;但有机碳矿化比例则有所增加,其增幅随土层加深而增大。草地利用方式发生变化后,土壤氮素矿化速率和矿化比例、硝化速率和铵化速率均显著降低,这些指标在表层土壤以草地转变为农地后降低较多,在深层土壤以草地转变为灌木林地降低较多。综上,半干旱黄土区草地转变为农地和灌木林地后,土壤碳氮循环强度和有效性显著降低,因此应避免草地向其它利用方式的转变。     

氮磷营养对柴胡抗旱性的影响

在盆栽条件下研究了氮、磷营养对柴胡(Bupleurumchinense.DC)抗旱性的影响。结果表明,在实验控制的干旱条件下,施用氮肥降低了叶片保水力,尤其高氮处理显著降低叶片相对含水量(RWC),并明显降低了细胞膜稳定性,严重抑制根系生长;施氮可减缓干旱条件下叶绿素a/b的下降程度,从而对光合作用有一定的促进作用,证明高氮降低了柴胡的抗干旱能力。而施用磷肥可增强细胞膜稳定性,促进根系生长,保持柴胡吸水和失水之间的平衡;并能够降低气孔对光合的限制从而保持在干旱下的光合能力。实验证明磷肥能够使柴胡在水分胁迫情况下能保持体内水分及其代谢的平衡,增强柴胡的抗旱能力。     

Precipitation and soil particle size co-determine spatial distribution of biological soil crusts in the Gurbantunggut Desert,China

Biological soil crusts(BSCs) are bio-sedimentary associations that play crucial ecological roles in arid and semi-arid regions. In the Gurbantunggut Desert of China, more than 27% of the land surface is characterized by a predominant cover of lichen-dominated BSCs that contribute to the stability of the desert. However, little is known about the major factors that limit the spatial distribution of BSCs at a macro scale. In this study, the cover of BSCs was investigated along a precipitation gradient from the margins to the center of the Gurbantunggut Desert. Environmental variables including precipitation, soil particle size, soil p H, electrical conductivity, soil organic carbon, total salt, total nitrogen, total phosphorus and total potassium were analyzed at a macro scale to determine their association with differing assemblages of BSCs(cyanobacteria crusts, lichen crusts and moss crusts) using constrained linear ordination redundancy analysis(RDA). A model of BSCs distribution correlated with environmental variables that dominated the first two axes of the RDA was constructed to clearly demonstrate the succession stages of BSCs. The study determined that soil particle size(represented by coarse sand content) and precipitation are the most significant drivers influencing the spatial distribution of BSCs at a macro scale in the Gurbantunggut Desert. The cover of lichen and moss crusts increased with increasing precipitation, while the cover of cyanobacteria crusts decreased with increasing precipitation. The cover of lichen and moss crusts was negatively associated with coarse sand content, whereas the cover of cyanobacteria crusts was positively correlated with coarse sand content. These findings highlight the need for both the availability of soil moisture and a relatively stable of soil matrix, not only for the growth of BSCs but more importantly, for the regeneration and rehabilitation of disturbed BSC communities in arid and semi-arid lands. Thereby, this study will provide a theory basis to effectively increase soil stability in desert regions.     

旱胁迫对啤酒大麦产量及酿造品质的影响

在武威黄羊镇啤酒大麦试验基地进行了干旱胁迫对甘啤6号生育期、农艺性状、籽粒产量、原麦品质、酿造品质的影响试验研究。结果表明:干旱胁迫下甘啤6号各生育期均提前,成活率降低,分蘖减少,株高、穗长、单株穗数、单株粒数、单株粒重、单穗粒重、穗粒数均降低;干旱胁迫使甘啤6号成穗数、穗粒数、千粒重均降低,导致产量降低,其中对成穗数影响最大,其次为穗粒数,对千粒重影响最小;干旱胁迫使大麦蛋白质含量升高,千粒重、淀粉含量和筛选率均降低,千粒重降幅尤其明显;干旱胁迫使麦芽糖化时间、糖化力、粘度、β-葡聚糖、微粉浸出率、粗细粉差降低,粗粉浸出率、a-氨基氮、可溶性氮、蛋白质、库值升高。     

干旱胁迫对马铃薯叶片超微结构及生理指标的影响

选用不耐旱品种‘费乌瑞它’、耐旱性较强品种‘东农308’和耐旱品种‘晋薯2号’的脱毒试管苗为材料,利用含有20%PEG-6000的MS液体培养基进行水分胁迫处理,研究干旱胁迫对马铃薯叶片细胞超微结构和生理指标的影响。结果表明:叶绿体对干旱胁迫反应最为敏感且受损伤最重,胁迫后叶绿体外形肿胀变圆,片层开始松散,间隙增大,甚至出现孔洞。线粒体次之,外膜破坏,嵴减少。对细胞核的影响相对较小。‘费乌瑞它’超微结构损伤最严重,‘东农308’次之,‘晋薯2号’伤害最轻。超微结构发生变化的同时,各项生理指标也随之改变。3个品种丙二醛(MDA)含量升高48.89%~243.27%,并且都达到极显著水平;过氧化物酶(POD)活性升高2.06%~32.98%,‘费乌瑞它’和‘晋薯2号’分别达到极显著和显著水平;不同品种的超氧化物歧化酶(SOD)活性和叶绿素含量变化趋势不一致。上述指标中,丙二醛含量和叶绿体超微结构变化显著,并能较好地表现出不同品种之间抗旱性的差异。     

甘肃黄土高原土壤水分预测及旱情预警模型研究

2006年天水农业气象试验站在自然状态下进行了土壤水分的消退试验,根据试验数据,揭示了土壤水分的消退规律.结果表明,从最适宜土壤湿度的上限开始,土壤含水量随时间的消退为对数曲线.从最适土壤水分含量的上限到下限需5 d时间,土壤失水速度为13.4 mm/d;从轻旱上限消退至严重干旱需20 d时间,土壤水分散失速度为3.9 mm/d.在此基础上建立了100 cm土层土壤含水量的预测模型及土壤干旱预警模型,经不同降水年型土壤水分实测值的检验表明,土壤含水量预测模型准确率较高,土壤干旱预警模型在预测不同程度的土壤干旱时准确率比较高,有一定实用性.     

水杨酸处理对干旱胁迫下丹参幼苗抗氧化能力的影响

以丹参幼苗为试验材料,研究了叶面喷施0.75 mmol/L的水杨酸(SA)对干旱胁迫下丹参幼苗相对含水量、电解质渗漏率、H2O2和丙二醛含量、4种抗氧化酶活性等生理指标的影响。结果表明:随着干旱胁迫的进行,丹参幼苗叶片相对含水量降低,H2O2含量增加,电解质渗漏率和丙二醛含量升高,水杨酸处理则延缓了这些参数变化;尽管SA处理后,CAT、APX活性暂时降低,但在随后的胁迫过程中,丹参幼苗叶片SOD、POD、CAT、APX活性显著高于对照。由此可知:水杨酸处理提高了丹参幼苗抗氧化酶活性,增强了植株对干旱胁迫的抵抗能力。     

土壤干旱对不同小麦品种籽粒淀粉积累和相关酶活性的影响

选用小麦旱地品种长武134和水地品种陕253,研究土壤干旱对小麦籽粒淀粉积累及相关酶活性的影响,探讨土壤干旱影响淀粉积累的酶学机制.结果表明,干旱处理提高了灌浆前期小麦籽粒淀粉积累速率、籽粒SS、AGPase、UGPase、SSS和GBSS酶活性.灌浆后期旱地品种籽粒淀粉积累速率及AGPase、UGPase降低幅度大于...