黄土丘陵区沙棘林几个水分生理生态特征研究

为探讨沙棘对半干旱黄土丘陵区水分条件的适应性,1998年对沙棘的水分生理生态及抗旱性进行了分析研究.试验结果表明(1)沙棘适应半干旱黄土丘陵区生境形成了耐旱、御旱的双重抗旱方式.在旱季,沙棘体内束缚水含量随干旱加剧而上升,束缚水与自由水比值随干旱加剧而增大,叶片维持较高的含水量,蒸腾减弱,叶水势降低,临界饱和亏增大,表现出较强的抗旱性.(2)沙棘光合速率具明显的日变化,10001200出现第1次峰值,1400 1500出现第2次峰值.沙棘光合速率与环境因子(气温、相对湿度和光合有效辐射)间有显著的相关关系,相关系数为0.84660.9351,其中光合有效辐射对光合速率影响最显著,气温次之,相对湿度最小;沙棘光合速率与气孔导度及细胞间CO2浓度间有十分显著的相关关系,相关系数为0.98520.9856.(3)沙棘蒸腾速率与气孔导度具明显的日变化,两者的变化趋势相似,5、7月日变化曲线呈单峰型,6、8、9月日变化曲线呈双峰型.在生长季(5-

Study on Several Hydrological and Ecological Characteristics of Hippophae rhamnoides in the Loess Hilly Region

To analyze the adaptation of Hippophae rhamnoides L. to water condition of the semiarid loess hilly region, water physiological and ecological characteristics of Hippophae rhamnoides L. and drought resistance were studied in 1998. The following results are obtained: (1) Hippophae rhamnoides L. forms the way of drought resistance of dry hardiness and keeping out drought to adapt the habitat of semiarid loess hilly region. In dry season, Hippophae rhamnoides L. shows stronger drought resistance, leaves of Hippophae rhamnoides L. can keep higher relative water content, weak transpiration intensity, low leaf water potential, big critical saturation deficiency, higher bound water content and bigger ratio of bound water to free water. (2) Photosynthetic rate of Hippophae rhamnoides L. has obviously diurnal variation,first peak assumed at 10:00 12:00, the second at 14:00 15:00. Photosynthetic rate has significant correlation with environmental factors (temperature, relative humidity and photosynthetic active radiation), and the coefficient was 0.846 6 0.935 1, of which photosynthetic active radiation has the biggest effect on photosynthetic rate, followed by temperature and relative humidity. Photosynthetic rate has utterly significant correlation with stomatal conductance and intercellular CO² concentration, and the coefficient is 0.985 2 0.985 6.(3)Transpiration rate and stomatal conductance have a similar diurnal variation, both exhibiting a single peak pattern in May and July, and bimodal pattern in June? August and September. In growing season, May through September, the maximum of transpiration occurs in July, lower value in May and September; Transpiration rate in May (0.39 g·g^-1 ·h ^-1) was just 41.93% of that in July (0.93g·g^-1 ·h^-1). The result indicates that precipitation primarily could meet the need of growth of Hippophae rhamnoides L. to the environmental condition of Ansai loess hilly region, Hippophae rhamnoides L. can be selected as pioneer species for planting in this region. These provide scientific basic for drought resistant forestation of Hippophae rhamnoides L., introducing fine variety, breeding and improving management.