Aims The subalpine coniferous forests in eastern Qinghai-Tibet Plateau provide a natural laboratory for studying effects of climate warming on terrestrial ecosystems. Research on differences between tree species in their responses to experimental warming can provide insights into their regeneration behavior and community composition under a future warmer climate.
Methods We used open-top chamber (OTC) to determine short-term effects of two levels of air temperature (ambient and warmed) and light (full light and ca. 10% of full light regimes) on the early growth and physiology of Betula albo-sinensis and Abies faxoniana seedlings.
Important findings The OTC manipulation increased mean air temperature and soil surface temperature by 0.51 ℃ and 0.33 ℃, respectively, under the 60-year plantation and 0.69 ℃ and 0.41 ℃, respectively, under the forest opening. Warming generally increased the growth, biomass accumulation and advanced physiological processes for seedlings of both species. In response to warming, both species allocated relatively more biomass to foliage and had significantly decreased root/shoot ratios (R/S), which might provide tree species an adaptive advantage when other environmental factors are not limiting. Warming may enhance photosynthesis in the two seedlings by increasing efficiency of PSⅡ in terms of increase in Fv/Fm, photosynthetic pigment concentrations and apparent quantum yield (Φ). However, the effects of warming on seedling growth and physiological performance varied by light conditions and species. For B. albo-sinensis seedlings, the effects of warming were pronounced only under full-light conditions, while the growth and physiological responses of A. faxoniana seedlings to warming were found only under low-light conditions. Competitive and adaptive relationships between the two species may be altered as a result of response differences to warming manipulation. The short-term beneficial impact of warming on the early growth and development of the two species suggests that global warming may lead to changes in regeneration dynamics and species composition in subalpine coniferous forest ecosystems.