Premium
Soil CO 2 efflux of two silver birch clones exposed to elevated CO 2 and O 3 levels during three growing seasons
Author(s) -
Kasurinen Anne,
KokkoGonzales Paula,
Riikonen Johanna,
Vapaavuori Elina,
Holopainen Toini
Publication year - 2004
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.1365-2486.2004.00841.x
Subject(s) - soil respiration , clone (java method) , respiration , efflux , betula pendula , growing season , carbon dioxide , zoology , soil water , horticulture , biology , chemistry , botany , ecology , biochemistry , dna
In the present open‐top chamber experiment, two silver birch clones ( Betula pendula Roth, clone 4 and clone 80) were exposed to elevated levels of carbon dioxide (CO 2 ) and ozone (O 3 ), singly and in combination, and soil CO 2 efflux was measured 14 times during three consecutive growing seasons (1999–2001). In the beginning of the experiment, all experimental trees were 7 years old and during the experiment the trees were growing in sandy field soil and fertilized regularly. In general, elevated O 3 caused soil CO 2 efflux stimulation during most measurement days and this stimulation enhanced towards the end of the experiment. The overall soil respiration response to CO 2 was dependent on the genotype, as the soil CO 2 efflux below clone 80 trees was enhanced and below clone 4 trees was decreased under elevated CO 2 treatments. Like the O 3 impact, this clonal difference in soil respiration response to CO 2 increased as the experiment progressed. Although the O 3 impact did not differ significantly between clones, a significant time × clone × CO 2 × O 3 interaction revealed that the O 3 ‐induced stimulation of soil respiration was counteracted by elevated CO 2 in clone 4 on most measurement days, whereas in clone 80, the effect of elevated CO 2 and O 3 in combination was almost constantly additive during the 3‐year experiment. Altogether, the root or above‐ground biomass results were only partly parallel with the observed soil CO 2 efflux responses. In conclusion, our data show that O 3 impacts may appear first in the below‐ground processes and that relatively long‐term O 3 exposure had a cumulative effect on soil CO 2 efflux. Although the soil respiration response to elevated CO 2 depended on the tree genotype as a result of which the O 3 stress response might vary considerably within a single tree species under elevated CO 2 , the present experiment nonetheless indicates that O 3 stress is a significant factor affecting the carbon cycling in northern forest ecosystems.