Species‐specific tree growth responses to 9 years of CO2 enrichment at the alpine treeline

摘要: 1. Using experimental atmospheric CO(2) enrichment, we tested for tree growth stimulation at the high-elevation treeline, where there is overwhelming evidence that low temperature inhibits despite an adequate carbon supply. We exposed Larix decidua (European larch) and Pin us mugo ssp. uncinata (mountain pine) to 9 years of free-air enrichment (FACE) in situ experiment treeline Swiss Alps (2180 m a.s.l.). 2. Accounting pre-treatment vigour individual trees, ring increments throughout period were larger growing under elevated but not Pinus. The magnitude response width varied over time, with a significant occurring treatment 3-7 (marginal year 6). 3. After treatment, leaf canopy cover, stem basal area total new shoot production overall greater trees CO(2), whereas Pinus showed no such cumulative response. could have caused effect on size even if further occurred, so it remains unclear responsiveness was sustained longer term. 4. stimulated more by relatively high spring temperatures early snowmelt date, suggesting less limiting these benefit gained from extra assimilated CO(2). also after solar radiation preceding season, perhaps reflecting gains due reserves. 5. Synthesis. Contrasting above-ground responses two species concentrations suggest will competitive advantage responsive species, as co-occurring Pinus, future concentrations. Stimulation growt might be especially pronounced warmer climate.