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Needle Respiration and Nitrogen Concentration in Scots Pine Populations from a Broad Latitudinal Range: A Common Garden Test with Field-Grown Trees
P. B. Reich, J. Oleksyn and M. G. Tjoelker
Vol. 10, No. 6 (Dec., 1996), pp. 768-776
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/2390512
Page Count: 9
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1. Models of tree function and forest ecosystem carbon budgets often assume that potential global changes in temperature and/or other factors may alter tissue nitrogen (N) and dark respiration rates (Rd). However, little is known of patterns of co-variation in tissue N and Rd among intraspecific populations originating along climatic gradients, and of whether an N-based model of Rd can like these two variables. To address these issues, we studied N and Rd in fully expanded needles of 10-year-old trees of 14 Scots Pine (Pinus sylvestris) populations of wide-ranging origin (43⚬ to 60⚬N), grown under common garden conditions. 2. For 11 lowland populations (elevation <200 m) from the continguous part of the species range (48⚬ to 60⚬N) grown at a field site in Kornik, western Poland (52⚬N), there were greater needle %N in populations from increasing latitude of origin or decreasing mean annual temperature
$(r \geq 0.93, P < 0.01)$. Similar %N and latitude of origin correlations were observed in another year at this site and in retrospective analyses of published data for diferent sets of Scots Pine populations grown in common gardens at 48⚬, 52⚬C and 62⚬N latitudes. Needle Rd rates of the 11 lowland populations growing at Kornik and measured at a common temperature (20⚬C) were greater, by as much as 50%, for more northerly than southerly populations. Mean Rd rates were positively correlated to latitude of origin and to mean annual temperature ( $P < 0.05, r = 0.7$ to 0.8). Rd and needle %N wre positively correlated ( $P < 0.01, r = 0.75$), with one relationship fitting all data. Across the entire range from 1.15. to 1.55 needle %N, Rd increased from 4.5 to 6.9 nmol g-1s-1. 3. Mean needle %N and Rd values for two montane southern populations (43⚬ and 44⚬N, elevation ≥ 885m) growing in the same common garden at Kornik were consistent with the relationships between mean annual temperature, needle %N and Rd observed for the more northerly populations but did not fit the latitudinal patterns. This suggests that temperature and/or associated climate variables are likely the driving force for observed genetic variation in Scots Pine needle %N and Rd across latitudinal and altitudinal gradients. 4. Results of these common garden studies support the idea of a general relationship between needle dark respiration and N concentration, and indicate that there is intraspecific genetic variation in physiology that is selected by climate that persists in a comoon environment, resulting in higher needle %N and respiration in plants originating from colder habitats. Such patterns need to be better understood and quantified, and merit consideration in modelling of current and potential global change effects on plant function and global carbon cycles.
Functional Ecology © 1996 British Ecological Society