Seedlings period growth traits of three exotic alder including Alnus glutino sa, A.cordata, A.nitida and two domestic alder, A.formosana and A.cremastogyne were studied with comparative-method. The growth traits including thousand kernels weight, germination rate and germination potential of seed, relative content of chlorophyll(SPAD), photosynthetic traits, rooting parameters and biomass among the five tre e species were compared, and the affected factors for seedlings growth were studied with principal co...