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为揭示柽柳(Tamarix chinensis)光合能力及耗水特征对地下水矿化度的响应规律,以黄河三角洲建群种——柽柳3年生植株为研究对象,在1.2 m的潜水水位下,模拟设置淡水、微咸水、咸水和盐水4种不同的地下水矿化度,测定柽柳叶片光合-光响应、蒸腾速率和树干液流的日变化。结果表明:地下水矿化度通过影响土壤盐分可显著影响柽柳光合特性及耗水性能。随地下水矿化度升高,柽柳叶片净光合速率(P_n)、最大P_n、蒸腾速率、气孔导度、表观量子效率和暗呼吸速率均先升高后降低,而水分利用效率(WUE)持续降低。淡水、微咸水和盐水处理下,柽柳P_n光响应平均值分别比咸水处理降低44.1%、15.1%和62.6%;微咸水、咸水和盐水处理下,柽柳WUE光响应平均值分别比淡水处理降低25.0%、29.2%和41.7%。随地下水矿化度升高,柽柳叶片光饱和点先升高后降低,而光补偿点持续升高,光照生态幅变窄,光能利用率变低。淡水和盐水处理下,柽柳Pn下降分别是非气孔限制和气孔限制引起的。柽柳树干液流速率随地下水矿化度升高而先升高后降低,咸水处理下树干液流速率日变幅最大,日液流量最高。淡水、微咸水和盐水处理下日液流速率平均值分别比咸水处理降低61.8%、13.1%和41.9%。咸水矿化度下柽柳有较高的光合特性,在蒸腾耗水较严重的情况下可实现高效生理用水,适宜柽柳较好地生长。
In order to reveal the response of Tamarix chinensis photosynthetic capacity and water consumption to the salinity of groundwater, the 3-year-old Tamarix chinensis community, a typical species of Tamarix chinensis in the Yellow River delta, was studied to simulate the fresh water, Brackish water, brackish water, saltwater and saltwater. The diurnal variations of photosynthesis-photosynthesis, transpiration rate and sap flow of Tamarix sargus were determined. The results show that the salinity of groundwater salinity can significantly affect the photosynthetic characteristics and water consumption of Salix psammophila by affecting soil salinity. With the increase of groundwater salinity, the net photosynthetic rate (P_n), maximum P_n, transpiration rate, stomatal conductance, apparent quantum yield and dark respiration rate of Tamarix ramosissima first increased and then decreased, while the water use efficiency (WUE) reduce. Under the condition of fresh water, brackish water and salt water treatment, the mean value of P_n light response of Tamarix chinensis decreased by 44.1%, 15.1% and 62.6% respectively compared with saline water treatment; Fresh water treatment decreased by 25.0%, 29.2% and 41.7%. With the increase of groundwater salinity, the light saturation point of Tamarix ramosissima first increased and then decreased, but the light compensation point continued to increase, the light ecological amplitude narrowed, and the light energy utilization rate became lower. Under freshwater and salt water treatments, the decline of Tamarix ramosissima was caused by non-stomatal limitation and stomatal limitation respectively. Tamarix sap flow rate increases first and then decreases with the increase of groundwater salinity, and the daily variation of sap flow rate under saltwater treatment is the highest with the highest daily flow rate. Fresh water, brackish water and saline daily average flow rate decreased by 61.8%, 13.1% and 41.9% respectively compared with saline treatment. Tamarix chinensis has higher photosynthetic characteristics under salt water salinity, and can achieve high efficient physiological water use under more severe transpiration water consumption, which is suitable for Tamarix growth.