Dahurian larch (Larix gmelinii Rupr.), the dominant tree species in Eurasian boreal forests, is important for studies on global change and regional carbon balance. However, few studies have focused on changes in the seasonal dynamics of its leaf phenology and photosynthetic capacity in response to environmental changes. It is unclear whether these responses are driven by genetic adaptation or by phenotypic acclimation. We examined the seasonal dynamics of leaf phenology (April to October) and photosynthetic capacity (May to September) of 32-year-old Dahurian larch trees for three years (2009-2011). The larch trees were from six provenances and were growing at the Maoershan Forest Ecosystem Research Station (45°24'N, 127°40'E). The six provenances originated from areas spanning approximately 4° in latitude (48-52°N) and an approximately 5 ℃ gradient of mean annual temperature (-2.3-2.6 ℃), arranged from north to south as follows: Tahe (TH), Genhe (GH), Sanzhan (SZ), Zhongyangzhan (ZYZ), Wuyiling (WYL), and Hebei (HB). To access the top canopy of the sampled trees, we constructed 15-m-high wooden scaffolds at the site. We selected three representative trees from each provenance for analyses. We examined 5-10 representative branches per tree twice a week from early April to mid-May to evaluate bud development and leaf unfolding, and from early September to mid-October to evaluate leaf shedding. To measure gas exchange for phenology observations, we analyzed three fully expanded sunlit fascicles on young short shoots at the top of the canopy of each tree in situ. There were no significant differences in leaf unfolding and shedding dates among the provenances. For trees from all provenances, leaf unfolding began in late April and leaf shedding began in late September, resulting in a mean growing season length of 150-153 days, 145-147 days, and 148-151 days in 2009, 2010, and 2011, respectively. The starting date of leaf unfolding was significantly and negatively correlated with the accumulated temperature above 0 SymbolpB@C before leaf unfolding in spring (from 1 March to 4 May). The starting date of leaf shedding was significantly and positively correlated with the mean temperature in the fall (from 1 August to 30 September) (P < 0.05). These results suggested that there is phenotypic acclimation of leaf phenology to environmental changes. The seasonal dynamics of the light-saturated net photosynthetic rate (P_max) differed among the provenances. Compared with the annual mean P_max value, the P_max values of trees from the higher-latitude provenances (i.e., TH, GH, and ZYZ) were lower in the early growing season and higher in the other growing seasons. In contrast, the P_max values of trees from the lower-latitude provenances (i.e., HB and WYL) were higher than the annual mean value only in the middle of the growing season. Across the whole growing season, the P_max values for all six provenances were positively correlated with the mean seasonal temperature (P < 0.01). In terms of P_max values, trees from the higher-latitude provenances were more temperature-sensitive than were trees from the lower-latitude provenances, except for those from the TH provenance. In any given growing season, P_max differed significantly among the six provenances (P < 0.05). Among all the provenances, the trees from the ZYZ provenance had the highest P_max across the whole growing season. The lowest P_max values in the early, mid, and late growing season were in trees from the GH, TH, and WYL provenances, respectively. These variations in the seasonal dynamics of P_max among the six provenances provide evidence for the genetic adaptation of larch trees to the climatic conditions in their region of origin. These findings suggest that the phenological plasticity and photosynthetic adaptability of L. gmelinii play crucial roles in its survival and reproduction in extensive and diverse habitats.