Long-term effects on and adaptations of the carbon physiology of long-lived trees exposed to increasing atmospheric levels of CO2 are unknown. We compared two indigenous Quercus species, Q. ilex and ...Q. pubescens, growing in a natural CO2 spring located in central Italy and at a nearby control site. In May, 1995 photosynthetic rate at least doubled when measured with supplemental CO2 in both species and sites. Dark respiration was much higher at the CO2 spring site in both species. Foliar sugar and starch concentrations in Q. ilex exhibited significant site and diurnal differences (May and September). In July, 1995 there was little difference in the water potential values of the measured trees at the different sites over the diurnal period. Photosynthetic rate was higher for both species in the CO2 spring, particularly in the early morning and late afternoon. Mid-day stomatal closure reduced photosynthesis to similar levels. In the morning leaf conductance and transpiration were generally lower in the CO2 spring trees, contributing to higher instantaneous water use efficiency for both species. Isoprene emission rates were higher in Q. pubescens trees growing in the CO2 spring. The maximum difference between control and CO2 spring trees occurred in late afternoon. In contrast, Q. ilex exhibited isoprene emission near background level. Foliage and branch carbon and nitrogen status showed increased concentrations of starch and tannins in Q. ilex and of soluble sugars in Q. pubescens in the elevated CO2 environment, while nitrogen concentration decreased in both species. Wood gravity increased 6 and 3% in Q. ilex and Q. pubescens, respectively, growing in the CO2 spring. Q. ilex exhibited afternoon recovery of water potential compared to Q. pubescens which had better night-time recovery. Q. ilex and Q. pubescens exposed to elevated CO2 for prolonged periods exhibit different mechanisms for dealing with additional reduced carbon and do maintain an altered carbon physiology, even in midst of the region's characteristic summer drought.
Impacts of naturally elevated soil CO2 concentrations on communities of soil archaea and bacteria ibanc, Nataa; Alex J. DumbrellauthorSchool of Biological Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, United Kingdom; Ines Mandi-MulecauthorBiotechnical Faculty, Department of Food Science and Technology, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia ...
2015
Journal Article
Rising atmospheric CO2 concentration is a key driver of enhanced global greening, thought to account for up to 70% of increased global vegetation in recent decades. CO2 fertilization effects have ...further profound implications for ecosystems, food security and biosphere‐atmosphere feedbacks. However, it is also possible that current trends will not continue, due to ecosystem level constraints and as plants acclimate to future CO2 concentrations. Future predictions of plant response to rising CO2 are often validated using single‐generation short‐term FACE (Free Air CO2 Enrichment) experiments but whether this accurately represents vegetation response over decades is unclear. The role of transgenerational plasticity and adaptation in the multigenerational response has yet to be elucidated. Here, we propose that naturally occurring high CO2 springs provide a proxy to quantify the multigenerational and long‐term impacts of rising CO2 in herbaceous and woody species respectively, such that plasticity, transgenerational effects and genetic adaptation can be quantified together in these systems. In this first meta‐analysis of responses to elevated CO2 at natural CO2 springs, we show that the magnitude and direction of change in eight of nine functional plant traits are consistent between spring and FACE experiments. We found increased photosynthesis (49.8% in spring experiments, comparable to 32.1% in FACE experiments) and leaf starch (58.6% spring, 84.3% FACE), decreased stomatal conductance (gs, 27.2% spring, 21.1% FACE), leaf nitrogen content (6.3% spring, 13.3% FACE) and Specific Leaf Area (SLA, 9.7% spring, 6.0% FACE). These findings not only validate the use of these sites for studying multigenerational plant response to elevated CO2, but additionally suggest that long‐term positive photosynthetic response to rising CO2 are likely to continue as predicted by single‐generation exposure FACE experiments.
Plant responses to future, elevated atmospheric CO2 from single‐generation FACE experiments were compared with those observed in naturally high carbon dioxide springs, following multi‐generation exposure. Responses for a panel of traits, including enhanced photosynthesis and reduced stomatal conductance, were broadly conserved suggesting that FACE experiments are a good proxy for long‐term, multi‐generational responses to this facet of the changing climate. These findings have implications for enhanced global greening, since our data suggest that vegetation will not acclimate to elevated, CO2 growth stimulation is likely to persist. Similarly, the data are relevant for future plant breeding and conservation strategies.
Two Italian CO2 springs allowed us to study the long‐term effect of a 350–2600 μmol mol–1 increase in CO2 concentrations on the surface structures of leaves of Quercus ilex L. Carbon dioxide ...increased the quantity of cuticular waxes, above an apparent threshold of 750 μmol mol–1 CO2. Leaf wettability was not modified by CO2 concentrations. Reduction in stomatal frequency was observable up to 750 μmol mol–1 CO2, the slope being almost the same as that estimated for the increase in CO2 concentration from pre‐industrial times to the present. At higher concentrations, CO2 seemed to exert no more impact on stomatal frequency.
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