DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 1-2/2000 str. 34 <-- 34 --> PDF |
J. Oomac: PROJEKT FACE: PROMATRANJE UTJECAJA OBOGAĆIVANJA ATMOSFERE S CO, U GUSTOM ... Šumarski list br. I 2. CXXIV(2000), 27-32 a basal area of 34 nrVha, and it is in a linear growth phase. It offers the opportunity for rigorous tests of hypotheses that address the essential features of a forest stand and how they could influence the responces to C02. These features include: the closed canopy, which constrains growth responses; full occupancy of the soil by the root system, which constrains the nutrient cycle; the larger scale of the trees compared to saplings in open-top chambers, which changes the functional relationships of carbon cycling; and the longer time scale that can be addressed, permitting studies of forest regeneration and soil carbon changes. Different tasks are organized around an interconnected set of hypotheses. The objectives of these tasks are: characterize aboveground tree growth and leaf area in relation to C02 concentration and interannual variation in other environmental factors; determine the relationships between stand dynamics, photosynthesis, respiration, and tissue chemistry; establish the importance ofstomatal conductance, boundary layer conductance, and canopy conductance as factors regulating whole-plant transpiration response to elevated C02; measure stem respiration response in sweetgum to C02 and partition observed responses into growth and maintenance respiration; quantify fine root density and turnover; determine the trajectory of response to C02 in leaf litter chemistry, and begin long-term measurement of litter decomposition; quantify the critical components of the nitrogen cycle and their response to C02 enrichment; identify sources and dynamics of soil organic matter and their response to C02 enrichment; construct an intra-annual carbon budget for the stands to determine the impact of elevated C02 on net ecosystem production; use a mechanistic, process-based soil-plant ecosystem model to develop and refine hypotheses of ecosystem response to elevated C02. The C02 enrichment treatment (560 ppm) began in April, 1998, after a full year of pre-treatment site characterization and tree growth monitoring. Although significant results has been already achieved, all described responses must be considered preliminary because the trees had been growing in ambient CO 2 for 10 years prior to the start of fumigation and their responses to the sudden increase in C02 are likely to be different from what would occur had they always been in high C02. This is why there are no results published so far. Data presented in paper were collected and photos taken during authors visit ORNL in September 1999 as a participant oflEA Bioenergy International Workshop. Additional information were collected from Dr Richard Norby and Dr Gregg Mar land (Oak Ridge National Laboratory). For global changes like C02 increase and associate climate changes would affect Croatia as well as every other part of the world, it could be interesting to learn about current trends and recent experiments on that field. K ey w o rds : C02, FA CE facility, sweetgum stand 32 |