温度和CO2浓度升高对荒漠藻结皮光合作用的影响

2007年,对腾格里沙漠东南缘沙坡头地区1956年(51龄)和1981年(26龄)人工植被区及自然植被区的藻结皮净光合速率(P_n)变化,及其与结皮含水量(>100%、40%～60%和<20%)、大气CO₂浓度(360和700 mg·L^-1)和温度(13 ℃、24 ℃ 和28 ℃)的关系进行研究.结果表明：51龄、26龄人工植被区和自然植被区的藻结皮P_n分别为3.4、4.4和3.2 μmol·m^-2·s^-1，且51龄人工植被区藻结皮的P_n显著高于26龄人工植被区和自然植被区；藻结皮含水量对其P_n影响显著，且中等含水量(40%～60%)藻结皮的P_n显著高于低含水量(<20%)和高含水量(>100%)；CO₂倍增(700 mg·L^-1)后，中等和高含水量藻结皮的P_n增加了1.8～3.3倍，而低含水量时，藻结皮的P_n变化不明显；高含水量和中等含水量处理时，24 ℃和28 ℃条件下藻结皮的P_n较13 ℃时提高27%～66%，而在低含水量时，不同温度的藻结皮P_n值无显著差异.

Effects of elevated temperature and CO2 on desert algal crust photosynthesis.

Taking the 26-and 51-year-old artificial vegetation areas and the natural vegetation area in Shapotou region of southeast Tengger Desert as study sites, this paper measured the net photosynthetic rate (P_n) of algal crusts, and analyzed its relationships with crust water content (>100%, 40%-60%, and <20%), atmospheric CO₂ concentration (360 and 700 mg·L^-1), and air temperature (13 ℃, 24 ℃, and 28 ℃). The P_n of the crusts in the 26-and 51-year-old artificial vegetation areas and natural vegetation area was 3.4, 4.4, and 3.2 μmol·m^-2·s^-1, respectively, and the P_n in 51-year-old other two areas. Crust water content had significant effects on the P_n, which was significantly higher at medium water content (40%-60%) than at low (<20%) and high (>100%) water content. When the CO₂ concentration doubled (700 mg·L^-1), the P_n increased by 1.8-3.3 times at medium and high crustwater content but had less change at low crust water content, compared with that under ambient CO₂ concentration (360 mg·L^-1). At medium and high crust water content, the P_n at 24 ℃ and 28 ℃ was 27%-66% higher than that at 13 ℃ (P<0.05), but at low crust water content, no significant difference was observed at the three temperatures.