Báo cáo lâm nghiệp: "doubling atmospheric CO concentration on 2 matter distribution and CO exchange of 2 yr growth, dry 2 old sweet chestnut trees (Castanea sativa Mill.)"

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Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: doubling atmospheric CO concentration on 2 matter distribution and CO exchange of 2 yr growth, dry 2 old sweet chestnut trees (Castanea sativa Mill.)...

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Nội dung Text: Báo cáo lâm nghiệp: "doubling atmospheric CO concentration on 2 matter distribution and CO exchange of 2 yr growth, dry 2 old sweet chestnut trees (Castanea sativa Mill.)"

Effect of doubling atmospheric CO concentration on 2 matter distribution and CO exchange of 2 yr growth, dry 2 old sweet chestnut trees (Castanea sativa Mill.) 1 Mousseau H.Z. Enoch 2 M. 1 Ecoloqie Végétale. Bat. 362, Université Paris-Sud 91405 Orsay Gsdex, France, and Ecologie Végétale, 2 Department Agricultural Meteorology, Agricultural Research Organisafion, The Volcani Center, of Bet Dagan, Israel concentration (a50 ppm), the other set at twice Introduction that C0 concentration. C0 enrichment was 2 2 maintained from 15 April to November. The amount of C0 in the global atmo- 2 The plants were grown in 2 permanently ven- tilated daylit growth chambers in a field at the sphere has increased about 25% during University Campus in Orsay, France (48°N, 2°E). the last century. A doubling of the preindus- Atmospheric bulk air was blown into the en- trial C0 level and an increase of the global 2 closures from air-intakes placed 4 m above the surface temperature of at least 2°C is ground. Pure C02 was supplied to the C0 - 2 expected in the next century (Clark, 1982). enriched chamber by a steel tank containing 300 kg of compressed C0 (Carboxique Française). 2 The gas exchange and carbon storage The growth chambers had a ground area of 2 capacity of forest trees may play an impor- , 2 m were 1 m high, made out of transparent tant role in regulating the global atmo- polypropylene glued to aluminum frames. The spheric C0 concentration. It is therefore 2 aboveground part could be lifted off a base which was buried in the ground. The chambers’ important to describe and understand the air throughflow was 4 M3.min-1. Plants were behavior of tree species with regard to watered daily and nutrient granules were added elevated atmospheric C0 . 2 on the ist of June (0.75 g of N, 0.60 g of P 3 0 2 and 1.1 g of K per pot). 0 2 At the end of October, 8 matched pairs were harvested and their biomass distributions re- Materials and Methods corded. Two yr old sweet chestnut seedlings, obtained from a forest nursery, were potted in galvanized Results steel containers (25 cm in diameter, 50 cm deep) with 24 1 of surface soil from a nearby chestnut forest. The plants were sorted ac- Leaf characteristics (Table I) cording to size: 24 matched pairs were made from plants of similar heights and growth pat- Prolonged Coenrichment slightly 2 re- terns. One set of plants was grown in the control duced final leaf size, but enhanced growth chamber at ambiant C0 atmospheric 2 mean
leaf thickness. In the C0 chest- through the vegetative development per- -enriched 2 iod showed a tendancy towards fewer nut plants, stomatal density and stomatal index were not significantly different from leaves and lower leaf area per plant after June in the C0 plants. Further- the control. -enriched 2 more, the branch elongation (main branch + side shoots) was, during that period, Growth pattern (Table 11) 30% lower in the C0 plants. -enriched 2 The C0 enrichment seemed to shorten 2 Dry matter partitioning (Table III) the time period over which the main branches grew. After the end of July, 62% Table III shows that the root biomass of of the enriched plants ceased growth as C0 plants was 69% heavier -enriched 2 compared with 37% of the controls. than roots of the control plants. The The early onset of yellowing and the increase was statistically significant stopped terminal bud growth indicates The shoot was 22% lighter (P>95%). earlier of the -enriched 2 C0 senescence Consequently, the shoot/root (P>80%). plants. ratio was changed from 0.49 in the control The final leaf area per plant, at the end to 0.23 in the C0 plants and total -treated 2 of the growth period, was reduced by dry matter increased by 43% in the C0- 2 C0 enrichment. The pattern of growth 2 enriched plot.
Discussion and Conclusion 2 C0 exchange measurements Towards the end of the first growth season Tree species may react differently to ele- vated levels of atmospheric C0 In chest- (4 Sept.), 2 plants grown at 350 ppm were . 2 transferred into an airtight assimilation nut trees, CO fertilization was accompa- :2 nied by a decrease in leaf area and a chamber where environmental conditions reduction in shoot growth, which is very were controlled (22/15°C day-night, 15 h photoperiod, 50% RH). Whole plant photo- unusual and may have resulted from the synthesis at 250 jlmol-m- PPFD and 1 s- ’ 2 timing of the nutrient application. The accumulation of the carbon surplus was dark respiration were measured after a 2 wk adaptation period as the slope of C0 restricted to the root system. 2 concentration over time in the whole These changes could have far reaching chamber (Gaudillere and Mousseau, ecological consequences for tree growth 1989). During the two 1 st 2 wk, the C02 of Castanea species under future elevated concentration in the chamber was main- C0 levels. 2 tained at 330 ppm. It was then increased to 660 ppm for another 2 wk period. C0 2 enrichment increased net C0 uptake by 2 References about 20% during the day and decreased dark respiration so that the diurnal C02 balance was 28% greater for the C0 - 2 Clark W.C. (198!2) In: Carbon Dioxide Review. enriched plants (results not shown). Clarendon Press Press-Oxford University Press, New York. increase in daily carbon The 28% Gaudill6re J.P. & Mousseau M. (1989) Short in approximate agreement exchange was term effect of C0 enrichment on leaf develop- 2 with the 43% increase in total dry matter ment and gas exchange of young poplars of C0 chestnut plants observed -enriched 2 (Populus euramericana cv. 1 214). Oecol. in the growth measurements. Plant. 10, 95-10.’i