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Elevated CO 2 influences the responses of two birch species to soil moisture: implications for forest community structure
Author(s) -
Catovsky S.,
Bazzaz F. A.
Publication year - 1999
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1046/j.1365-2486.1999.00247.x
Subject(s) - yellow birch , seedling , water content , moisture , competition (biology) , environmental science , soil water , betulaceae , horticulture , agronomy , botany , chemistry , biology , ecology , soil science , maple , geotechnical engineering , organic chemistry , engineering
Increased levels of atmospheric CO 2 may alter the structure and composition of plant communities by affecting how species respond to their physical and biological environment. We investigated how elevated CO 2 influenced the response of paper birch ( Betula papyrifera Marsh.) and yellow birch ( Betula alleghaniensis Britt.) seedlings to variation in soil moisture. Seedlings were grown for four months on a soil moisture gradient, individually and in mixed species stands, in controlled environment facilities at ambient (375 μL L –1 ) and elevated (700 μL L –1 ) atmospheric CO 2 . For both individually and competitively grown paper birch seedlings, there was a greater CO 2 growth enhancement for seedlings watered less frequently than for well‐watered seedlings. This differential change in CO 2 responsiveness across the moisture gradient reduced the difference in seedling growth between high and low water levels and effectively broadened the regeneration niche of paper birch. In contrast, for yellow birch seedlings, elevated CO 2 only produced a significant growth enhancement at the wet end of the soil moisture gradient, and increased the size difference between seedlings at the two ends of the gradient. Gas exchange measurements showed that paper birch seedlings were more sensitive than yellow birch seedlings to declines in soil moisture, and that elevated CO 2 reduced this sensitivity. Additionally, elevated CO 2 improved survival of yellow birch seedlings growing in competition with paper birch in dry stands. Thus, elevated CO 2 may influence regeneration patterns of paper birch and yellow birch on sites of differing soil moisture. In the future, as atmospheric CO 2 levels rise, growth of paper birch seedlings and survival of yellow birch seedlings may be enhanced on xeric sites, while yellow birch may show improved growth on mesic sites.