荒漠植物沙拐枣群体光合作用及土壤呼吸研究

Canopy photosynthesis and soil respiration of desert plant Calligonum potanini.

为了探讨荒漠植物群体光合作用和干旱荒漠区碳源汇特征,联合利用改进同化箱和LI-8100土壤CO2通量自动测量系统,选择高温强光和适宜环境期,连续2年进行了观测研究。结果表明:沙拐枣群体光合速率(CAP)在不同年份、不同月份差异较大,土壤水分改善可显著提高群体光合能力,高温强光期和适宜环境期日平均(08:00—18:00)CAP分别为1.82和2.89μmol/(m2·s);用同化枝水平光合速率(Pn)计算群体水平光合速率时,高温强光期和适宜环境期分别用公式CAP=0.12Pn+0.39(r=0.86,P<0.0001)和CAP=0.18Pn+0.28(r=0.92,P<0.0001)。沙拐枣生长期植冠下土壤CO2释放速率平均为0.29μmol/(m2·s),荒漠裸地为0.15μmol/(m2·s)。沙拐枣群体生长期固定碳为3.82g/(m2·a);相应时期植冠下土壤释放碳为1.03g/(m2·a),荒漠裸地为0.53g/(m2·a)。研究表明:在水分短缺的荒漠地区,荒漠植物沙拐枣群体光合速率提高幅度超过根系主要分布层土壤水分提高幅度,适宜环境期可提高近1倍。荒漠生态系统土壤呼吸速率较低,荒漠裸地土壤呼吸速率约为植冠下的50%。荒漠植物沙拐枣种群区为弱碳源。

In order to explore canopy photosynthesis of desert plant Calligonum potanini, and characteristics of carbon source and carbon sink in arid desert area, the canopy apparent photosynthesis and soil CO2 efflux rate were measured in high temperature and irradiation and suitable environment periods by the modified assimilation chamber and LI-8100 automated soil CO2 flux system in two years. The results showed that the difference of canopy apparent photosynthetic rate （CAP） of C. potanini in different years and months was significant, the canopy photosynthesis was enhanced significantly with improving soil water, the average CAP （08：00-18：00） was 1.82 Ixmol/（m2＂s） in high temperature and irradiation period and 2.89 Ixmol/（ m2＂ s） in suitable environment period, respectively. The calculated formula of CAP by photosynthetic rate of assimilating shoots （Pn） was CAP = 0. 12Po ＋ 0.39 （ r = 0. 86, P 〈 0. 000 1 ） in high temperature and irradiation period and CAP = 0. 18Pn ＋ 0.28 （ r = 0.92, P 〈 0. 000 1 ） in suitable environment period. The soil CO2 efflux rate under plant canopy was 0.29 μmol/（m2. s） in growth period, and it was 0. 15 μmol/（m2.s） in desert bare land. The fixed carbon of C. potanini canopy in growth period was 3.82 g/（m2 -a） , the released carbon under plant canopy was 1.03 and 0.53 g/（ m2. a） in desert bare land in the same period. These results indicated that the increasing in canopy apparent photosynthetic rate of desert plant C. potanini exceeded the increasing range of soil water in the layers of root mainly distributed in the water shortage desert area; it doubled in suitable environment period. The soil respiration rate of desert ecosystem was lower and that in desert bare land was about 50% of thatunder plant canopy. The zone of desert plant C. potanini population was a weak carbon source.