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991.
992.
广东省坡耕地面积66.79万hm2,占耕地总面积的23.48%.是广东省旱粮、油、糖、烟、热带亚热带果树以及热作等的生产基地,在农业生产上具有举足轻重的地位.但由于大部分坡耕地是顺坡开垦,重用轻养,耕作粗放,少施肥等,以致存在土壤有机质偏低,氮、磷、钾养分贫乏,土壤酸度大,耕层浅薄,砂化严重,干旱,农作物产量低等问题。然而,坡耕地土层深厚,环境条件优越,水热充足,生产潜力大。针对坡耕地的这些状况,提出:搞好农地整治,变“三跑地”为“三保地”;用养结合,以地养地;因地制宜,合理利用;增施化学肥料,调节土壤养分等对策。 相似文献
993.
994.
针对LIFAC法脱硫效率低的问题,从吸收剂的涡流循环喷钙装置、增强吸收剂的活性、抑制脱硫产物硫酸钙的高温分解等几个方面进行了剖析,并自制LIFAC法廉价喷钙剂,在佛山华丰纸业有限公司进行中试,取得了脱硫率平均90%以上的效果,最后,作者对该技术的优越性进行了评估。 相似文献
995.
Incorporating Collateral Data in Conservation Biology 总被引:1,自引:0,他引:1
NICHOLAS A. LINACRE§ ALLAN STEWART-OATEN† MARK A. BURGMAN PETER K. ADES‡ 《Conservation biology》2004,18(3):768-774
Abstract: Conservation biologists often need to set ecological modeling assumptions or estimate parameters from sparse data. In some cases this problem can be addressed by incorporating data from closely related species or from the same species at different sites (i.e., collateral data). Currently no structured methods exist for incorporating such information. An analogous problem in Actuarial science is to set premium rates in situations with little direct data on claim frequency or size. The rates are estimated using actuarial credibility theory, which incorporates collateral data with the direct data. actuarial credibility theory combined with the actuarial control cycle financial management process also provides an adaptive mechanism for updating assumptions. This theory may have some utility for ecologists wanting to incorporate collateral data in an adaptive management framework, a companion to approaches such as Bayesian updating. We describe the historical development of actuarial credibility theory from early ad hoc methods to empirical Bayes approaches. We explore some of the theory's strengths, such as relative simple formulae for incorporation collateral data, and we explore some of the theory's weaknesses, such as the use of the best linear approximation to the Bayes estimate. We illustrate potential applications of the theory using an example on the mortality rate of the Powerful Owl ( Ninox strenua ). 相似文献
996.
鹅掌楸和女贞同化CO2和释O2能力的比较 总被引:2,自引:0,他引:2
采用LI-6400红外气体分析仪,分别在生长初期、盛期、末期测定鹅掌楸和女贞净光合速率,用重量法测定叶面积。得到女贞的净光合速率、叶面积指数和同化CO2及释O2的能力均大于鹅掌楸的结论,可为城市绿化树种的选择提供依据。 相似文献
997.
Exploring Population Dynamics Patterns in a Rare Fish, Zingel asper, through Capture-Mark-Recapture Methods 总被引:1,自引:0,他引:1
Abstract: We performed a capture-mark-recapture study on one of the last populations of Zingel asper , an endemic percid species of the Rhône River basin in France. The distribution of Z. asper has decreased dramatically during the last century. We sampled three sites in suitable habitats in the Beaume River. No impact of individual tagging on survival was found. The demography of the population was analyzed using capture-recapture methods that allow the estimation of survival, recruitment, and demographic growth rates. Annual survival rates were low (0.35–0.50). The level of transience was high (5% to 25%), suggesting that a significant number of individuals were highly mobile or shifted to suboptimal habitats. Seniority rates suggested random highly variable recruitment between years. The three sites had similar variation patterns in all demographic parameters, indicating broad spatial covariation in population dynamics. We found some local differences in demographic parameters, which could be linked to local habitat quality. Individual tagging allowed for the estimation of demographic parameters that improved our understanding of Z. asper population dynamics and revealed mechanisms that may affect population persistence, such as stochastic recruitment, low survival, and frequent dispersal. The fragmentation of habitat through river damming inhibits dispersal and represents a threat to the persistence of Z. asper in the Rhône basin. Our results offer evidence of the importance of dispersal in nonmigratory fishes and confirm the usefulness of individual tagging methods in rare fish demography. 相似文献
998.
光生物反应器培养紫球藻及藻粉降血脂的研究 总被引:4,自引:0,他引:4
研究了搅拌式光生物反应器中搅拌速度、通气量对紫球藻生长、胞外多糖和藻细胞超微结构的影响.实验结果表明:在特定光照(1000μmolm^-2s^-1)和培养温度(25℃)条件下,当搅拌转速为200r/min、通气量为0.71vvm时,藻生长速度和胞外多糖含量最高;增加通气量有利于藻细胞胞外多糖及生物量的提高.对藻细胞超微结构的观察发现,与摇床培养相比,搅拌式光生物反应器使藻细胞淀粉颗粒明显增多,粘质鞘层变薄,光合片层增多.动物实验表明,紫球藻能明显降低摄食高脂饲料SD大鼠血脂TC、TG、LDL-C水平,并提高HDL-C含量.实验结果预示,紫球藻对预防动脉粥样硬化和冠心病的发生有一定的意义.图2表3参26 相似文献
999.
S.L. Liu Y.M. Luo Z.H. Cao L.H. Wu K.Q. Ding P. Christie 《Environmental geochemistry and health》2004,26(2):285-293
Mycorrhizal and non-mycorrhizal alfalfa (Medicago sativa) was grown in pots containing soil artificially contaminated with various levels of benzo[a]pyrene (B[a]P)(0, 1, 10 and 100 mg kg–1). Soil and plants were sampled after 30, 40, 50, 60 and 90 days and compared with unlanted pots. The percentage of mycorrhizal root length colonized by Glomus caledoniun was not significantly affected by the addition of B[a]P up to 10 mg kg–1 but was significantly lower at 100 mg kg–1B[a]P compared with low concentrations (p < 0.05). There was no difference in soil polyphenol oxidase and dehydrogenase activity among the controls and applications of 1 and 10 mg kg–1 of B[a]P. However, enzyme activities were significantly higher at 100 mg kg–1B[a]P compared with the other three treatments, and there was no mycorrhizal effect. Over a period of 90 days the concentration of B[a]P in soil in which alfalfa was grown was significantly lower than in unplanted soil (p < 0.05). Degradation rates of B[a]P added at 1, 10 and 100 mg kg–1 without G. caledonium were 76, 78 and 53%, and with mycorrhizal inoculation were 86, 87 and 57%. The degradation rate in unplanted soil was significantly lower than in planted soil, and was significantly higher in medium- and low-B[a]P treatments than in the high B[a]P concentration tested. There is a possibility of enhancement phytoremediation of PAHs in rhizosphere soil with arbuscular mycorrhizal fungi. 相似文献
1000.
Dynamics of Turbulence in Low-Speed Oscillating Bottom-Boundary Layers of Stratified Basins 总被引:1,自引:0,他引:1
Lorke Andreas Umlauf Lars Jonas Tobias Wüest Alfred 《Environmental Fluid Mechanics》2002,2(4):291-313
This paper focuses on the impact of an oscillating low-speed current on the structure and dynamics of the bottom-boundary layer (BBL) in a small stratified basin. A set of high-resolution current profile measurements in combination with temperature-microstructure measurements were collected during a complete cycle of the internal oscillation (`seiching') in the BBL of Lake Alpnach, Switzerland. It was found that even a relatively long seiching period of 24 hours significantly changed the form of the near-bottom current profiles as well as the dynamics of the turbulent dissipation rate compared to the steady-state law-of-the-wall. A logarithmic fit to the measured current profiles starting at a distance of 0.5 m above the sediment led to inconsistent estimates of both friction velocity and roughness length. Moreover, a phase lag between the current and the turbulent dissipation of 1.5 hours and a persistent maximum in the current profile at a height of 2.5 to 3 m above the sediment were observed. The experimental findings were compared to the results of a k- turbulence model and showed good agreement in general. Specifically, the inconsistent logarithmic fitting results and the observed phase lag were reproduced well by the model. 相似文献