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Premise: Climate change may lead to C stress (negative C balance) in trees. Because nonstructural carbohydrates (NSC) are required during metabolic reactivation in the spring, C stress might delay budbreak timing. This effect is expected to be greater in shade‐intolerant than in shade‐tolerant species, owing to the faster C economy in the shade‐intolerant. Methods: We experimentally induced C stress in saplings of six temperate tree species that differed in their light requirements by exposing them to either full light or shade from summer to spring, then recorded the date of first budbreak for the individuals. Because the levels of C reserves that represent effective C stress may differ among species, we estimated the degree of C stress by recording survival during the experiment and measuring whole‐sapling NSC concentrations after budbreak. Results: Shade reduced NSC concentrations and increased the sugar fraction in the NSC in all species. In the shade, shade‐intolerant species had higher mortality and generally lower NSC concentrations than the shade‐tolerant species, indicating a trend for more severe C stress in species with faster C economy. In shade‐intolerant species, budbreak started earlier and proceeded faster in full light than in shade, but in shade‐tolerant species budbreak was delayed in full light. The effects of the light environments on budbreak were not greater in shade‐intolerant than in shade‐tolerant species. Conclusions: Our study reveals a correspondence between budbreak responses to light and the light requirements of the species. This finding confirms that C metabolism has a significant role in triggering budbreak and demonstrates that whether C stress accelerates or delays budbreak depends on the species' light requirements. [ABSTRACT FROM AUTHOR]

Premise of the Study: It is unclear to what extent the co‐occurrence of angiosperm and gymnosperm species in some marginal ecosystems is explained by reduced growth in angiosperms due to carbon (C) limitation and by high stress tolerance in gymnosperms associated with lack of vessels and resource conservation. Methods: We examined growth patterns and traits associated with C balance in four evergreen angiosperm species (including one vesselless species, Drimys winteri) and three gymnosperm tree species of a cold‐temperate rainforest in southern Chile. We measured the mean basal area increment for the first 50 (BAI50) and the last 10 years (BAI10), wood density, leaf lifespan, and nonstructural carbohydrate (NSC) concentrations in different organs. Key Results: BAI50 was 6‐fold higher in angiosperms than in gymnosperms and ca. 4‐fold higher in Drimys than in the fastest‐growing gymnosperm. BAI10 and aboveground NSC concentrations were significantly higher and leaf lifespan lower in angiosperms than in gymnosperms; these differences, however, were largely driven by the slow growth and low NSC concentrations of the Cupressaceae species (Pilgerodendron uviferum), while the two Podocarpaceae had BAI10 and NSC concentrations similar to angiosperms. In angiosperms, NSC and starch concentrations were generally higher in species with lower BAI10, indicating no severe C limitation. Conclusions: The co‐occurrence of angiosperms and gymnosperms in cold‐temperate rainforests of southern Chile is not explained by growth disadvantages and C limitation in angiosperms. Long leaf longevity, but not lack of vessels, appeared to favor resource conservation and C balance in some gymnosperms (Podocarpaceae). [ABSTRACT FROM AUTHOR]