毛乌素沙地沙柳液流特征及其对环境因子的响应

应用Flow32-1K包裹式热平衡液流仪,对毛乌素沙地沙柳不同径级枝条液流进行长期监测,同步观测试验样地气象变化,分析沙柳枝条液流变化规律并建立与环境因子关系模型。结果表明:(1)沙柳枝条随着径级的增加液流日变化从宽峰曲线到明显的单峰曲线,并且液流速率呈增大趋势;天气条件对液流影响较大,雨天液流速率波动较剧烈,呈明显的多峰曲线;晴天时液流速率变化呈明显的双峰曲线,雨天沙柳枝条液流速率及日液流量均比晴天低,随着径级增大,晴天和雨天日累计液流量差值逐渐变大。(2)液流速率与地表温度、大气温度、饱和水汽压差、太阳辐射和风速呈极显著正相关关系,与空气相对湿度呈极显著负相关关系。(3)雨天环境因子中饱和水汽压差和空气相对湿度对液流速率的影响较大,拟合结果平均R2在0.8以上;晴天太阳辐射强度是控制沙柳枝条液流速率的重要因子,拟合结果平均R~2在0.85以上。通过对沙柳枝条液流速率进行监测,分析沙柳群落的蒸腾消耗特征,为沙地水资源合理利用与群落结构优化调控提供数据支撑。     

不同种源沙柳(Salix psammophila)苗木蒸腾耗水特性的研究

于2004年生长季节利用BP3400精密天平等仪器,在人工模拟干旱的条件下,对5个种源沙柳苗木的连日耗水量和耗水速率日变化规律进行观测。结果表明:5个种源沙柳的连日耗水量呈现一致的波动递减趋势;耗水速率日变化均呈明显的"单峰型"曲线,峰值出现在12:00-14:00,随干旱胁迫的加剧,民勤和榆林种源提前到10:00-14:00。白天平均耗水速率和最大耗水速率均是适宜水分>中度干旱>严重干旱。民勤种源在整个干旱胁迫过程中总耗水量最小为1876.9g,其次是达拉特种源(1972.8g)和盐池种源(2001.8g),耗水量最大是乌审旗(2200.6g)和榆林种源(2112.9g)。沙柳各种源最大耗水速率与白天平均耗水速率的比值非常接近,平均为1.56,根据这一比例关系,在对沙柳的最大耗水速率进行测定后,可以推算出其白天的平均耗水速率,并进一步推算白天(或整天)的耗水量。     

灌丛密度对毛乌素沙地南缘沙柳生长及土壤水分动态的影响

在毛乌素沙地南缘选择不同栽植密度(0.2、0.6株/m2和0.8株/m2)的沙柳人工灌丛,对沙柳生长特征及土壤水分进行研究。结果表明:不同栽植密度沙柳的生长特征存在显著差异,沙柳株高、平均冠幅直径、地上生物量、叶片生物量和茎生物量随着栽植密度的增加呈先增加后降低趋势。不同栽植密度沙柳灌丛土壤水分动态存在明显差异,沙柳灌丛土壤含水量随着栽植密度增大呈先增加后降低趋势,在栽植密度0.6株/m2(T2)达到最大值。在毛乌素沙地生境条件下,与水资源容量相适应的沙柳栽植密度约为0.6株/m2,在该栽植密度下土壤水分含量基本上能满足沙柳的生理生态需水。     

沙柳方格沙障对库布齐沙漠沙丘粒度分布的影响

为定量探讨沙柳方格沙障对沙粒粒度组成与特征的影响,以流动沙丘(LS)、设障2a沙丘(TS)和设障6a沙丘(SS)为研究对象,在沙丘不同部位、不同土层和障格内不同位置进行取样,分析样品的粒度组成与特征。结果表明:1)随着设障年限的增加,粘粒和粉粒含量增加,细砂含量下降,SS粘粒和粉粒含量与TS和LS的含量差异显著,而TS和LS二者间差异不明显;LS、TS各粒级含量在三个层次间差异均不明显,而SS 0-5cm的粘粒、粉粒以及极细砂粒体积含量较其他2层差异显著。2)SS的频率分布曲线变化幅度小于TS和LS的频率分布曲线变化幅度。各沙丘的平均粒径MZ、分选系数δ、偏度SK、峰度KG的大小顺序均表现为SS相似文献   

干旱胁迫对5个种源沙柳(Salix psammophila)气体交换及水分利用效率的影响

在盆栽条件下,对5个种源沙柳进行了水分胁迫处理,在不同干旱阶段对苗木叶水势、土壤含水率、蒸腾速率、光合速率等气体交换特性及水分利用效率进行了研究.结果表明:沙柳属于亚低水势忍耐脱水耐旱树种,叶水势随土壤含水量的下降而下降,变化趋势可用双曲线方程y=a b/x(0.389 0＜a＜0.520 3,8.906 6＜b＜11.466 9)拟合,其中民勤种源沙柳的双曲线方程中b值最低,为8.91,表现出较强的耐旱特性.在正常水分供应条件下,榆林种源沙柳的光合速率为23.89 μmol/(m2·s),水分利用效率为3.44 μmol/mmol,表现出很强的光合生产能力.随着干旱胁迫的加剧,各种源沙柳苗木的水分利用效率均有不同程度增加,民勤种源沙柳的增加值最大,为0.75 μmol/mmol,表现出了较强的抵抗干旱的能力,而榆林种源沙柳对水分亏缺则非常敏感,光合速率、蒸腾速率都急剧下降.这充分表明在水分供应充足的条件下,榆林种源沙柳具有最大的光合生产潜力;而当遇到干旱胁迫时,民勤种源沙柳则表现出极强的维持体内水分平衡的能力,是5个种源中最耐旱的种源.     

机械沙障抗拉力学特性研究——以临策铁路沿线高立式和平铺式沙障为例

为揭示机械沙障抗拉力学特性,优选合适的阻沙固沙材料,利用TY8000系列伺服控制机对试验对象进行纵向拉伸试验.结果表明:当孔隙度为均一型(全疏型或全密型)时,不同材料沙障的试样宽度与抗拉力均呈幂函数正相关,与抗拉强度呈幂函数负相关,其抗拉力与伸长量变化曲线均为单峰曲线;当材料相同时,不同孔隙度沙障的试样宽度与抗拉力均呈...     

河西绿洲灌区农户对循环农业工程的行为响应及其影响因素研究

以河西绿洲灌区为例,从农户行为角度出发,采用主成分分析和OLS回归模型探讨了农户对循环农业工程的行为响应机制.研究表明:绝大部分样本农户对循环农业工程的响应较明显,农户间的响应程度差异较小.农户的年龄、文化程度、兼业情况、劳动力数、耕地面积、地理区位、信息获取能力和周围人参与循环农业的比例对循环农业的行为响应呈显著的正向影响,而农户对当地基础设施建设的满意度及其运销能力对循环农业的行为响应呈显著的负向影响.因此,发展循环农业不仅要关注农户层面,还应综合考虑其它多方面的因素,特别是市场环境和政策环境等软条件.保障耕地面积不减少,实现循环农业要求的规模经济效应,会使农户更加积极的采用环保循环的生产生活方式对循环农业作出行为响应.     

循环率对波涌灌间歇入渗特性和地下水水质影响的研究

通过肥液(KNO3溶液)室内入渗试验,模拟研究了地下水位为150 cm条件下,循环率对肥液间歇入渗土壤和地下水中NO3--N运移特性的影响.结果表明, 相同净入渗时间和周期条件下,在一定范围内循环率越小,间歇时间越长,土壤水分再分布越充分,间歇入渗减渗作用越强;与循环率为1/2相比,循环率为1/3的平均入渗率减小不显著,当循环率减小至1/4时,减渗程度明显增大;随循环率的减小累计入渗量减小;循环率取值为1/3时,随水分迁移进入地下水的硝态氮量最小.     

库布齐沙漠沙柳林复壮更新技术措施研究

沙柳是干旱、半干旱地区重要的防风固沙树种和工业用材林树种。研究沙柳复壮更新技术措施对于维护区域生态环境,促进沙柳相关产业的快速、可持续发展具有重要的现实意义。本文以库布齐沙漠东段衰退的沙柳林为研究对象,探讨了"设置沙障"、"地表平茬"、"常规平茬"、"施肥"和"不同密度造林"对沙柳高生长和地径两个形态指标的影响。试验结果表明:5种不同复壮更新技术措施对沙柳的高生长和地径生长均有显著促进作用(P<0.05);其中,密度为4 m×2m、3 m×2m的设置对沙柳的高生长和地径增长均有显著促进作用,"施肥"的处理对沙柳的高生长效果比较显著,"设立沙障"的处理对沙柳的地径生长效果更好。     

ACQ-D防腐剂处理对沙柳沙障防腐性能的影响

采用常温浸渍处理方式,研究了氨溶烷基铵铜(ACQ-D)防腐剂浸泡时间及处理浓度对沙柳沙障吸药量及失重率的影响,进而评价ACQ-D防腐剂对沙柳沙障的防腐性能。试验结果表明:沙柳沙障吸药量随浸泡时间的延长而增加,经24h和48h处理的吸药量差异不显著,不同浓度处理吸药量达到标准的浸泡时间不同;经防腐剂处理的沙柳沙障失重率明显小于对照,且失重率随防腐剂浓度的增加而减小;各处理沙柳沙障的耐腐性均达到耐腐的等级。     

3种滨河植物单根抗拉特性与其微观结构关系

为分析黄河源区高寒草甸植物单根的抗拉力学性质及其护岸的微观力学机理,以华扁穗草、线叶嵩草和金露梅3种优势滨河植物为研究对象,通过开展单根拉伸试验和石蜡切片试验,定量分析3种植物单根力学特性及其与微观结构的关系.结果表明,当根径在<0.5 mm、0.5～1.0 mm和>1.0 mm 3个根径级别时,3种植物单根抗拉力和延...     

Rust resistance in Salix to Melampsora larici-epitea

A total of 174 Salix (willow) clones belonging to 57 species and 14 interspecific hybrids were inoculated with seven pathotypes of Melampsora larici-epitea using the leaf disc method. Infection types were scored based on the uredinial pustule area data and the inoculum density. A close correlation ( R ² = 0·82) was found between the average pustule area and the average number of spores produced. Most of the willows were also assessed in the field for rust in 1999. Most willow clones belonging to the species native to western Europe were infected by the rust. In inoculation experiments, uredinia developed on 46 S. viminalis clones, out of a total of 47. In the field, all the S. viminalis clones were infected by rust. Within the subgenus Vetrix , eight out of the 17 willow species that originated from North and South America produced rust pustules in inoculation experiments. Of these, S. pellita was most susceptible. Salix irrorata and S. lasiolepsis var. bracelinae produced well developed pustules after inoculation but no rust infections were detected in the field. In both leaf disc tests and field assessments, no rust infections were found on S. candida , S. cordata , S. drummondiana , S. eriocephala , S. hookeriana , S. houghtonii , S. humilis , S. rigida var. mackenziana and S. syrticola . Of 12 species of subgenus Vetrix native to northeast Asia and Japan, only S. kochiana was susceptible both in inoculation tests and in the field. Salix rossica produced no symptoms in leaf disc tests but showed low levels of infection in the field. The maximum infection type scores in leaf disc tests were highly significantly correlated with field disease severity scores (Spearman rank correlation coefficient was 0·76, P  < 1 × 10⁻¹⁰).     

Diversity in root traits of sorghum genotypes in response to Striga hermonthica infestation

Striga hermonthica is a major biotic constraint to agriculture in the lowland areas of Ethiopia where sorghum is a major stable crop. A pot and a field experiment were conducted in 2011 during the rainy season using 10 sorghum genotypes. Each experiment had infested and non‐infested conditions as the main plots and the 10 genotypes as subplots. The aim of this study was to examine the response of root traits of the sorghum genotypes to S. hermonthica infested conditions and to investigate relationships among S. hermonthica, root and growth traits of sorghum genotypes. Sorghum genotypes were categorized in to three groups, that is, low, moderate and high S. hermonthica count groups. Each group showed a differential response to root traits. Low S. hermonthica count groups had significantly lower root length, root length density, root to shoot ratio and root dry weight compared with susceptible groups. In contrast to low S. hermonthica count groups, moderate S. hermonthica count groups had higher root length, root length density, root to shoot ratio and root dry weight. Highly significant and strong relations were observed among root traits of sorghum, indicating that any of the root traits can be used as indicators for resistance. The result indicates different reactions in root traits in the upper soil layer may be useful for genetic improvement of S. hermonthica resistance and tolerance breeding in sorghum.     

Variable response of open-pollinated seedling progeny of avocado to Phytophthora root rot

Phytophthora root rot, caused byPhytophthora cinnamomi Rands, is the most important disease of avocado (Persea americana Miller). In an attempt to identify root rot-resistant rootstocks that could ultimately be used under conditions in southern Florida, we screened open-pollinated progeny of avocado from the National Germplasm Repository in Miami. From 1996 to 1998, a total of 2,355 seedlings from 51 accessions were examined in potting mix artificially infested withP. cinnamomi. Most seedlings developed severe root rot, but tolerance was observed in some families (i.e., progeny of certain accessions). Although the most susceptible families developed mean disease ratings of up to 97% root necrosis, mean ratings for the most tolerant families were less than 60%. There was also a strong relationship between the racial background of the female parent and the tolerance of seedlings. Seedlings of the West Indian race and hybrids between it and the Guatemalan race were significantly more tolerant than those from other parents (P< 0.05). Individuals in several families developed < 50% root necrosis, the arbitrary standard of tolerance in this study. Twelve families accounted for 82% (188 of 229) of the tolerant seedlings, and only two of these did not have a West Indian or Guatemalan × West Indian pedigree. Broad-sense heritability for PRR tolerance was 0.45. This is the first report on the inheritance of PRR tolerance in avocado and on the influence of genotype and racial pedigree under controlled conditions.