Premium
Below‐ground responses of silver birch trees exposed to elevated CO 2 and O 3 levels during three growing seasons
Author(s) -
Kasurinen Anne,
Keinänen Minna M.,
Kaipainen Saara,
Nilsson LarsOla,
Vapaavuori Elina,
Kontro Merja H.,
Holopainen Toini
Publication year - 2005
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 - 10.1111/j.1365-2486.2005.00970.x
Subject(s) - betula pendula , biology , orange (colour) , growing season , fumigation , botany , horticulture , microbial population biology , zoology , bacteria , genetics
Field‐growing silver birch ( Betula pendula Roth) clones (clone 4 and 80) were exposed to elevated CO 2 and O 3 in open‐top chambers for three consecutive growing seasons (1999–2001). At the beginning of the OTC experiment, all trees were 7 years old. We studied the single and interaction effects of CO 2 and O 3 on silver birch below‐ground carbon pools (i.e. effects on fine roots and mycorrhizas, soil microbial communities and sporocarp production) and also assessed whether there are any clonal differences in these below‐ground CO 2 and O 3 responses. The total mycorrhizal infection level of both clones was stimulated by elevated CO 2 alone and elevated O 3 alone, but not when elevated CO 2 was used in fumigation in combination with elevated O 3 . In both clones, elevated CO 2 affected negatively light brown/orange mycorrhizas, while its effect on other mycorrhizal morphotypes was negligible. Elevated O 3 , instead, clearly decreased the proportions of black and liver‐brown mycorrhizas and increased that of light brown/orange mycorrhizas. Elevated O 3 had a tendency to decrease standing fine root mass and sporocarp production as well, both of these O 3 effects mainly manifesting in clone 4 trees. CO 2 and O 3 treatment effects on soil microbial community composition (PLFA, 2‐ and 3‐OH‐FA profiles) were negligible, but quantitative PLFA data showed that in 2001 the PLFA fungi : bacteria‐ratio of clone 80 trees was marginally increased because of elevated CO 2 treatments. This study shows that O 3 effects were most clearly visible at the mycorrhizal root level and that some clonal differences in CO 2 and O 3 responses were observable in the below‐ground carbon pools. In conclusion, the present data suggests that CO 2 effects were minor, whereas increasing tropospheric O 3 levels can be an important stress factor in northern birch forests, as they might alter mycorrhizal morphotype assemblages, mycorrhizal infection rates and sporocarp production.