PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Compensatory growth of defoliated silver birch seedlings under changing climate and varying nitrogen availability.
Huttunen, Liisa *,1, Niemelä, Pekka 1, Peltola, Heli 1, Rousi, Matti 2, Kellomäki, Seppo 1, 1 University of Joensuu, Faculty of Forestry, Joesuu, Finland2 Finnish Forest Research Institute, Punkaharju research station, Punkaharju, Finland
ABSTRACT- We investigated the compensatory growth of defoliated silver birch seedlings (Betula pendula Roth) under elevated atmospheric temperature and CO2 concentration at varying levels of nitrogen nutrition. The seedlings grew in climate-controlled closed chambers under the four climatic treatments consisting of ambient and elevated temperature and CO2 concentration, and their combination. The birch seedlings were divided between three N fertiliser treatments (0 kg, 130 kg and 270 kg N ha-1) and each group further into three levels of damage in leaves of plants (0%, 25% and 50% of total leaf area). The ability of a plant to tolerate damage and compensate the lost foliage was analysed by measuring the efficiency of CO2 exchange and seasonal growth (shoot height and plant dry mass) throughout the summer 2002. We found that damage in leaves enhanced the efficiency of photosynthesis, as well as the average seasonal growth in mass and height, most in the plants growing under elevated atmospheric CO2 and temperature. The height of plants was nearly 32% greater than in undamaged plants grown with similar conditions. Elevation in atmospheric CO2 and increase in nitrogen availability caused also as much as 50% greater height growth in defoliated plants compared to the similarly treated (fertilised and defoliated) plants under ambient climatic conditions. Our conclusion is that defoliated plants allocate resources vigorously to the growth under favourable conditions, i.e. under elevated temperature, as well as under unlimited carbon and nitrogen availability.
Key words: climate, birch, defoliation, compensation