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51.
The effect of land cover/vegetation on soil water dynamic in the hilly area of the loess plateau,China 总被引:1,自引:0,他引:1
Severe soil and water loss has lead to widespread land degradation in China's loess plateau. During the past decades, a great deal of effort was made on vegetation restoration to reduce soil and water loss in the loess plateau. However, due to water shortage the efficiency of vegetation restoration was not as satisfactory as expected. As part of a vegetation restoration project, we conducted research aiming to understand the relationship between vegetation pattern and soil water dynamics. The goal was to find vegetation types appropriate for the loess plateau with scarce water resources. In 1986, fifteen plots of land were planted with five vegetation types: pine woodland, shrubland, sloping cropland, alfalfa and semi-natural grassland. Soil water content, runoff, soil erosion were measured for each plot. Environmental variables, such as rainfall, evaporation and temperature, were recorded simultaneously by an automated meteorological station. The relationship between land cover pattern and soil water dynamic was evaluated by using statistical models. We found that: (1) soil water loss occurred during the growing season, and it reached the maximum in the second half of July; (2) soil water was not fully replenished from rainfall during the rainy season; (3) pine woodland induced the largest water loss to surface runoff, followed by sloping cropland, alfalfa, semi-natural grassland and shrubland; the poor capability of pine woodland for water conservation may be attributed to soil compaction and poor ground coverage under the tree; (4) in most cases, soil water of the five vegetation types was low except for shrubland and semi-natural grassland where it was moderate-high during a few periods. These conditions inhibit sustainable vegetation growth in the semi-arid loess hilly area of the loess plateau, China. 相似文献
52.
固定化纤维素酶催化反应动力学模型研究 总被引:1,自引:0,他引:1
建立固定化纤维素酶反应动力学模型,在此基础上系统研究了席勒模数、产物竞争性抑制、体系宏观底物浓度等因素对球形载体内部底物分布的影响,并讨论了各因素对固定化纤维素酶效率因子的影响。结果表明席勒模数增大使载体内底物浓度降低,效率因子减小;产物竞争性抑制增大使载体内底物浓度升高,对效率因子的影响与席勒模数和体系宏观底物浓度有关,共存的产物竞争性抑制和内扩散限制之间存在相互减弱对方影响的效应;体系宏观底物浓度增大使载体内底物浓度升高,效率因子增大,可以减弱席勒模数与产物竞争性抑制的影响。 相似文献
53.
Presence of indigenous rhizobia nodulating promiscuous soyabean was determined in 92, mainly sandy soils, from wetter agro-ecological zones of Zimbabwe suited to soyabean production. A total of 129 isolates were obtained from nodules of promiscuous soyabean varieties, Magoye and Hernon 147, and a specific variety, Roan grown in potted soils. Magoye nodulated in 80%, Hernon 147 in 50% and Roan in only 25% of the 92 soils tested. Rhizobia populations ranged from undetectable to 2.4×104 cells g−1 of soil. Twenty-one of these isolates were tested for symbiotic effectiveness on two varieties, promiscuous Magoye and specific Roan. Differences in parameters such as nodule numbers, nodule weights and total N fixed reflected diversity among the indigenous isolates. Three isolates had significantly higher N2-fixing potential in comparison with the commercial strain MAR 1491 on promiscuous Magoye. Host ranges of 34 isolates were evaluated on nine legume species: Arachis hypogaea, Cajanus cajan, Crotalaria juncea, Glycine max, Macroptilium atropurpureum, Phaseolus vulgaris, Sesbania sesbania, Vigna subterranea, Vigna unguiculata. Of these 34 isolates, 33 formed nodules with M. atropurpureum of which 61% were moderately effective to very effective while all nodulated V. unguiculata with 58% being moderately effective to very effective. Twenty-eight isolates nodulated V. subterranea and C. cajan (short season variety) with 76 and 36% of these being moderately to very effective, respectively. None of the isolates formed nodules on Phaseolus vulgaris, Arachis hypogaea or Sesbania sesban. Our results indicate that the ability of even specific varieties of soyabean to nodulate with indigenous isolates in African soils is greater than generally assumed. 相似文献
54.
Fábio R. C. F. César Takashi Muraoka Rodrigo C. da Silva Luiz Francisco Souza-Filho 《Journal of plant nutrition》2020,43(18):2773-2784
Abstract A possible way to improve phosphate rock (PR) agronomic performance is through the addition of elemental sulfur (S0). We used 32P isotope dilution method to assess the P taken up by crops treated with PR. Two experiments, one with common bean and other with upland rice, were carried out, to evaluate the effect of S0 on the agronomic performance of two contrasting PR, applied in different methods. Gafsa (GPR) and Patos de Minas (PPR) were used as the high and low reactivity PR, respectively. The experiments were arranged in completely randomized design on factorial structure 2?×?2 × 2?+?2; which means 2 PR (GPR and PPR) versus 2?S0 condition (with or without-S0) versus 2 application methods (band and broadcast) plus 2 additional treatments (control and triple superphosphate). In band application the S0 increased the amount of P uptake by plants from fertilizer of GPR from 2.57 to 9.86?mg pot?1 for common bean and of 2.26 to 7.05?mg pot?1 to rice. Regardless the management adopted, less than 2% of P applied as PPR has been taken up by crops. The addition of S0 as a strategy to increase the agronomic performance of PR is PR characteristics dependent and fertilizers placement. 相似文献
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57.
试验分析了铜纤维的施加比例对木材纤维/铜纤维复合中密度纤维板物理力学性能和电磁屏蔽效能的影响。结果表明,铜纤维的施加比例对复合中密度纤维板的力学性能影响显著,在木材纤维/铜纤维混合原料中施加一定量的异氰酸酯胶,可显著改善复合中密度纤维板的胶合性能,其胶合强度可以达到国家标准的要求。铜纤维施加比例对复合中密度纤维板的电磁屏蔽效能影响显著,铜纤维在中密度纤维板中的复合位置对电磁屏蔽效能影响较显著,当中密度纤维板双表面复合铜纤维且施加比例为3时其电磁屏蔽效能可达到60dB以上。 相似文献
58.
随着科技水平的提高,人工影响天气作业作为防灾减灾的科学手段,其效果和效益越来越受人们关注。采用高炮或火箭向对流云或层状云中播撒碘化银,对云层中的水滴或冰粒子实施人工干预,进行静力催化和动力催化,促进和加速水滴或冰粒增长并下落,达到人工增雨抗旱的目的,其直接效益已得到一致公认。对2012年3月21日聊城市一次人工增雨抗旱作业的直接增雨效果进行了分析,初步得出在初春层状云中实施人工影响天气作业的效果十分明显。 相似文献
59.
蜡蚧轮枝菌和缨小蜂对假眼小绿叶蝉的协同控制作用 总被引:1,自引:0,他引:1
研究了假眼小绿叶蝉(Empoasca vitis)的寄生蜂缨小蜂(Schizophragma parvulas)和寄生真菌蜡蚧轮枝菌(Lecanicilliam lecanii)单独使用和联合使用时对假眼小绿叶蝉种群的控制作用.结果表明,在单独进行控制时(在一个世代内按每株放雌蜂3头的密度释放缨小蜂,或按5×107孢子/mL施菌2次),对假眼小绿叶蝉种群的控制效果分别达到52.7%和50.9%,但下一代假眼小绿叶蝉种群增长趋势指数仍然高于1,表明单独使用寄生蜂缨小和寄生真菌蜡蚧轮枝菌不能有效控制假眼小绿叶蝉种群的增长;缨小蜂和蜡蚧轮枝菌联合使用,对假眼小绿叶蝉种群的控制效果分别达82.9%和90.8%,且下一代假眼小绿叶蝉种群增长趋势指数低于1,表明下一代假眼小绿叶蝉种群数得到有效控制. 相似文献
60.