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Inter-annual variability of precipitation constrains the production response of boreal Pinus sylvestris to nitrogen fertilization Lim, H Oren, R Palmroth, S Tor-ngern, P Mörling, T Näsholm, T Lundmark, T Helmisaari, HS Leppälammi-Kujansuu, J Linder, S 2015-09-24T15:46:27Z 2015-07-05
dc.identifier.issn 0378-1127
dc.description.abstract © 2015 Published by Elsevier B.V.Tree growth resources and the efficiency of resource-use for biomass production determine the productivity of forest ecosystems. In nutrient-limited forests, nitrogen (N)-fertilization increases foliage [N], which may increase photosynthetic rates, leaf area index (L), and thus light interception (I<inf>C</inf>). The product of such changes is a higher gross primary production and higher net primary production (NPP). However, fertilization may also alter carbohydrate partitioning from below- to aboveground, increasing aboveground NPP (ANPP). We analyzed effects of long-term N-fertilization on NPP, and that of long-term carbon storing organs (NPP<inf>S</inf>) in a Pinus sylvestris forest on sandy soil, a wide-ranging forest type in the boreal region. We based our analyses on a combination of destructive harvesting, consecutive mensuration, and optical measurements of canopy openness. After eight-year fertilization with a total of 70gNm<sup>-2</sup>, ANPP was 27±7% higher in the fertilized (F) relative to the reference (R) stand, but although L increased relative to its pre-fertilization values, I<inf>C</inf> was not greater than in R. On the seventh year after the treatment initiation, the increase of ANPP was matched by the decrease of belowground NPP (78 vs. 92gCm<sup>-2</sup>yr<sup>-1</sup>; ~17% of NPP) and, given the similarity of I<inf>C</inf>, suggests that the main effect of N-fertilization was changed carbon partitioning rather than increased canopy photosynthesis. Annual NPP<inf>S</inf> increased linearly with growing season temperature (T) in both treatments, with an upward shift of 70.2gCm<sup>-2</sup>yr<sup>-1</sup> by fertilization, which also caused greater amount of unexplained variation (r<sup>2</sup>=0.53 in R, 0.21 in F). Residuals of the NPP<inf>S</inf>-T relationship of F were related to growing season precipitation (P, r<sup>2</sup>=0.48), indicating that T constrains productivity at this site regardless of fertility, while P is important in determining productivity where N-limitation is alleviated. We estimated that, in a growing season average T (11.5±1.0°C; 33-year-mean), NPP<inf>S</inf> response to N-fertilization will be nullified with P 31mm less than the mean (325±85mm), and would double with P 109mm greater than the mean. These results suggest that inter-annual variation in climate, particularly in P, may help explaining the reported large variability in growth responses to fertilization of pine stands on sandy soils. Furthermore, forest management of long-rotation systems, such as those of boreal and northern temperate forests, must consider the efficiency of fertilization in terms of wood production in the context of changes in climate predicted for the region.
dc.relation.ispartof Forest Ecology and Management
dc.relation.isversionof 10.1016/j.foreco.2015.03.029
dc.title Inter-annual variability of precipitation constrains the production response of boreal Pinus sylvestris to nitrogen fertilization
dc.type Journal article
pubs.begin-page 31
pubs.end-page 45
pubs.organisational-group Civil and Environmental Engineering
pubs.organisational-group Duke
pubs.organisational-group Environmental Sciences and Policy
pubs.organisational-group Nicholas School of the Environment
pubs.organisational-group Pratt School of Engineering
pubs.publication-status Published
pubs.volume 348

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