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991.
992.
对马尾松水土保持林的截水与持水功能进行了计量研究.结果表明:林冠的截水量与冠层枝叶生物量呈正相关;林分的截雨量和降雨量的关系可用Richards函数较好地拟合;灌木的截水能力与其叶质叶形有关,林分枯落物不仅具有较强的特水能力,还能明显改善土壤结构;土壤的非毛管孔隙度受植被因素的显著影响.并提出了各植被因子的持水模型和土壤孔隙度预测模型. 相似文献
993.
We characterized the adventitious rooting response of Eucalyptus globulus Labill. to various concentrations of calcium, nitrogen, phosphorus, iron, manganese, zinc, boron and copper. The parameters analyzed were percent rooting, root number, root length and mean rooting time. Root number and root length were significantly affected by mineral nutrition, whereas mean rooting time and rooting percentage seemed to be closely related to auxin availability. Root number was affected by calcium, nitrogen source and zinc, whereas root length was influenced by concentrations of phosphorus, iron and manganese, and by nitrogen source. Based on these results, we evaluated various combinations of several concentrations of these minerals in each rooting phase. Cuttings that were rooted in an optimized mineral nutrient medium and acclimatized to ex-vitro conditions for two months showed significantly higher survival after transplanting and drought stress than cuttings rooted in basal medium and treated in the same way. 相似文献
994.
Xiao Y 《Tree physiology》2003,23(7):463-471
Needle longevity of conifer species is known to increase with latitude, but little is known about intraspecific variation and associated factors within a location. Chinese pine (Pinus tabulaeformis Carr.) forests were investigated to identify patterns of needle longevity at seven sites with distinctive climatic conditions along a latitudinal gradient (33-38 degrees N) in Shaanxi province, northwest China. A demographic approach was used to quantify needle longevity as an index of entire foliage population adjusted to needle-age-specific mortality rates. There were significant differences in needle longevity of Chinese pine stands across sites and across sample plots within a site. Individual tree needle longevity ranged from 0.62 to 3.75 years for 276 samples across sites. Needle longevity increased with latitude (R2 = 0.40, P < 0.0001), but decreased with mean January temperature (R2 = 0.63, P < 0.0001). Foliage retention of Chinese pine stands at the regional level was generally associated with climatic variability, indicating that variation in needle longevity was primarily an environmental acclimation to low temperature in winter. Stand characteristics were closely associated with needle longevity at three sites located within the same climatic zone. Needle longevity was positively correlated with tree age (R2 = 0.48, P < 0.0001) and stand density (R2 = 0.26, P = 0.0015) at Huanglong and Huangling, respectively, whereas it was negatively associated with total tree height at Zhidan (R2 = 0.50, P < 0.0001). It is concluded that, at the stand and individual tree level, intraspecific variation in needle longevity is most likely a result of adaptation to patchy microsite environments. 相似文献
995.
996.
997.
在实验室条件下,以没食子酸和甘油为原料合成了1-没食子酸甘油酯(GG),做为油脂或油脂食品的抗氧化剂,保护油脂不因氧化腐败,延长贮存时间。合成途径是在日本高砂光正等人工作基础上进行了若干改进,使得率由45.7%提高到72.9%。以菜子油和豆油做底物,丙酯(PG)和2,6-二特丁基对甲酚(BHT)做对比抗氧化剂,用增重法评价其抗氧化性能,柠檬酸和酒石酸做增效剂,评价其增效作用,研究了浓度和分散度对诱导期的影响,探讨了结构因素对性能的影响。实验室结果表明:在本实验条件下,活性次序是GG>PG>BHT,随着浓度的增加,活性增大顺序是GG>PG>BHT。酒石酸对GG有增效作用,柠檬酸无效。溶解度对诱导期没有影响,说明了性能差异产生的原因。通过研究为简化合成途径,进行工业化生产提供了依据,并在此基础上为合成新型抗氧化剂找到一种可行方法。 相似文献
998.
北京市居住区植物造景初探 总被引:6,自引:0,他引:6
居住区是人居环境最直接的空间,其环境的建设应以改善和维护小区生态平衡为宗旨,以人与自然共存为目标。通过分析北京市回龙观风雅园小区、塞纳维拉小区、亚运新新家园等6个住宅区绿化现状、景观现状、功能要求、人文环境,提出了住宅区的植物配置模式。 相似文献
999.
1000.