西鄂尔多斯天然荒漠灌丛光合生态适应性

Photosynthetic characteristics and ecological adaptability of desert shrubs in western Ordos

为了探究西鄂尔多斯地区荒漠灌丛的光合生态适应性,以4种天然荒漠灌丛半日花(Helianthemum songaricum)、红砂(Reaumuria songarica)、沙冬青(Ammopiptanthus mongolicus)、霸王(Sarcozygium xanthoxylon)为研究材料,利用Li-6400便携式光合测定仪野外原位测定荒漠灌丛日光合动态和季节动态规律。结果表明:①不同季节灌丛光合作用适宜的温度存在差异,高温环境使灌丛净光合速率最适温度升高,低温环境使其降低。②不同季节4种灌丛的净光合速率、蒸腾速率、水分利用效率和气孔导度日变化曲线趋势为"双峰形",胞间CO2浓度日变化曲线趋势为"W形",但不同季节各指标平均日变化趋势表现各异。③不同季节灌丛净光合能力表现为:沙冬青>霸王>红砂>半日花,说明沙冬青具有较强的生态适应性。④净光合速率和蒸腾速率日变化趋势几乎保持同步状态,表明4种灌丛叶片气孔对外界环境变化反应敏感。⑤水分是限制荒漠灌丛生长发育的关键因素。为了保证荒漠植物的群落稳定性和生物多样性,在夏、秋季需对沙冬青、半日花、红砂和霸王进行水分管理。

To explore the ecological adaptability of desert shrubs in Western Ordos,four shrub species growing in this region were selected as test materials: Helianthemum songaricum,Reaumuria songarica,Ammopiptanthus mongolicus,and Sarcozygium xanthoxylum.Their photosynthetic physiological indices were measured using the Li-6400 photosynthesis system during diurnal and seasonal variations.Optimum temperature for photosynthesis varied across seasons;optimum temperature for net photosynthetic rate in desert shrubs increased in summer and decreased in winter.Diurnal variation curves for net photosynthetic rate,transpiration rate,water use efficiency,stomatal conductance,and intercellular CO2 concentration of the four dominant desert shrubs in the three seasons were "bimodal"and assumed the shape of "W";however,average diurnal variation trends of each index varied across seasons.Net photosynthetic rate of the four shrubs varied across seasons and followed the order of A.mongolicus > C.xanthoxylum > R.songarica > H.songaricum;thus,A.mongolicus showed the greatest ecological adaptability.Diurnal trends of net photosynthetic and transpiration rates were almost synchronous,indicating that stomata of these four dominant shrubs were sensitive to environmental changes.Water is a key factor limiting the growth and development of the four desert shrubs studied.To ensure the stability and diversity of desert plant communities,water management was conducted in summer and autumn for the four tested shrubs.