Short‐term responses of phenology, shoot growth and leaf traits of four alpine shrubs in a timberline ecotone to simulated global warming, Eastern Tibetan Plateau, China

Abstract

The short-term effects of artificial warming on phenology, growth and leaf traits were investigated in four alpine shrubs using the open-top chamber (OTC) method in a timberline ecotone (3240 m a.s.l.) on the Eastern Tibetan Plateau. The OTC enhanced the mean air temperature by 2.9°C throughout the growing season. In contrast, only a slight difference (0.4°C) in the mean soil temperature was observed in the OTC compared with the control plots (CP). Spiraea mongolica, Potentilla fruticosa, Conicera hispida (deciduous shrubs) and Daphne retusa (evergreen shrub) showed earlier bud break, flowering and fruit coloring as well as longer flower longevity in the OTC than in the CP. All deciduous shrubs in the OTC had a longer leaf lifespan. Daphne retusa had higher leaf survival rates in the OTC. No significant differences in the total number of flowers and fruits were noticed for most species between the two treatments. Warming stimulated the shoot and leaf growth for most species. The specific leaf area tended to increase for many species in the OTC. However, the leaf nitrogen concentration tended to decrease in P. fruticosa and S. mongolica. The results obtained in the present study indicate that warming conditions can have strong impacts on alpine shrubs in a timberline ecotone.

Short-term responses of Picea asperata seedlings of different ages grown in two contrasting forest ecosystems to experimental warming

“…Additionally, warming pronouncedly increased the current shoot length regardless of seedling ages or experimental sites. Our results were consistent with those from other warming experiments (Wada et al, 2002;Llorens et al, 2004;Xu et al, 2009). The increased current shoot length and SLA in the warmed plots suggest that warming treatment leaded to an increase in cell number or size, or both.…”

“…On the other hand, the number of days with daily mean air temperature above 10 • C was greater in the OTCs than in the control plots, also implying a longer growing season in the OTCs. The phenological responses noted in this study were in good agreement with many other similar studies (Arft et al, 1999;Wada et al, 2002;Norby et al, 2003;Xu et al, 2009). The phenological differences caused by warming could benefit gross photosynthesis and plant growth (Norby et al, 2003;Wan et al, 2005).…”

“…Additionally, temperature is a key factor that regulates ontogenetic development rate (Morison and Lawlor, 1999). Previous studies have reported that experimental warming accelerated organ initiation and expansion rates (Wada et al, 2002;Llorens et al, 2004;Xu et al, 2009). In the present case, artificial warming stimulated the growth of 2-and 8-year-old seedlings regardless of experimental sites, judged from the increased plant height, basal diameter, current shoot length and biomass in the OTCs.…”

Nonlinear flowering responses to climate: are species approaching their limits of phenological change?

“…The timing of peak and end of flowering are susceptible to effects of floral longevity, whereas flowering onset is not. Floral longevity is often temperature-dependent, generally with shorter floral longevity as temperatures warm [55][56][57][58]. Pollination may also influence flower longevity, with some species delaying senescence if they are not pollinated [57,59,60].…”

Initial responses of soil CO2 efflux and C, N pools to experimental warming in two contrasting forest ecosystems, Eastern Tibetan Plateau, China

“…Currently, there are over 1 million ha dragon spruce plantation in southwestern China, accounting for approximately 50% of the forest area in this region. To date, artificial warming studies in this region have focused more on aboveground components, with less focus on soils and belowground ecosystem processes (Yin et al 2008;Zhang et al 2008;Zhao and Liu 2009;Han et al 2009;Xu et al 2009). …”