For soil dry treatments, the main reason was nonstomatal limitation, but for air-dry-soil-wet treatment, stomatal limitation at first but nonstomatal limitation later.

• 短期干旱使气干土干、气湿土干处理净光合速率下降的主要原因是非气孔限制，而气干土湿处理前期光合速率下降主要是由于气孔限制，后期则为非气孔限制。