Difference of ecological strategies of coniferous tree species in Canadian and European boreal forests: simulation modelling analysis O. Chertov, J. Bhatti, A. Komarov, M. Apps, A. Mikhailov, S. Bykhovets
Introduction A significant differences in the allocation of NPP of carbon between functionally important tree components, first of all foliage and fine roots can reflect the different ecological strategies of European and Canadian coniferous species. The investigation of the NPP allocation between the plant organs is not often carried out at the terrestrial ecosystems simulation. The application of EFIMOD for European and Canadian boreal forests revealed that there are a significant differences of ecological parameters (silvics) of Canadian jack pine (Pinus banksiana) and black spruce (Picea mariana) of Canadian boreal forest and of European Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) correspondingly. A simulation experiment was performed to investigate influence of the NPP allocation patterns on components of carbon balance and tree productivity in Canadian and European forest ecosystems with the EFIMOD model
Model EFIMOD Full PAR Available PAR after shadowing αmax Initial tree biomass Tree biomass increment due to light, Ipe Annual tree biomass increment Ip = min { Ipe, Ipn } Leaf Biomass Tree biomass increment due to soil Nitrogen, Ipn Fine root biomass Reallocation of increment by tree organs nt Portion of available Nitrogen for the tree Tree (leaf, branch and root) litter Soil available Nitrogen SOIL Tree biomass, D, H, stem volume at the end of time step
Model EFIMOD Full PAR Available PAR after shadowing αmax Initial tree biomass Tree biomass increment due to light, Ipe Annual tree biomass increment Ip = min { Ipe, Ipn } Leaf Biomass Tree biomass increment due to soil Nitrogen, Ipn Fine root biomass nt Portion of available Nitrogen for the tree Reallocation of increment by tree organs kil ki1l ki3l Li - Undecomposed litter on soil surface Li Tree biomass, Aboveground D, H,fall stem litter volume Tree (leaf, branch and root) litter F.i - complex of humus substances with undecomposed debris (humified organic layer) at the end of Soil surface time step K j1s K js Soil available Nitrogen K j4s K j4l K j5s SOIL Lju Belowground litter fall Lju undecomposed litter in mineral topsoil K j3s F ju - complex of humus substances with undecomposed debris in mineral topsoil ( labil humus ) H - humus bonded with clay minerals K j5s K6
Model EFIMOD Full PAR Available PAR after shadowing αmax Initial tree biomass Tree biomass increment due to light, Ipe Annual tree biomass increment Ip = min { Ipe, Ipn } Leaf Biomass Reallocation of increment by tree organs Tree biomass increment due to soil Nitrogen, Ipn Fine root biomass ki3l nt Portion of available Nitrogen for the tree kil ki1l Li - Undecomposed litter on soil surface Li Tree biomass, Aboveground D, H,fall stem litter PAR volume Climate at the end of Soil surface Tree (leaf, branch and root) litter time step K jinitialisation S K j1s Soil available Nitrogen SOIL T 1 Available PAR for trees, ground j Lju vegetationland natural regeneration u - R F.i - complex of humus substances with undecomposed debris (humified organic layer) E 3 Belowground litter E fall S n undecomposed litter in mineral topsoil Ground vegetation K j3s F ju - complex of humus substances with undecomposed debris in mineral topsoil ( labil humus ) Natural regeneration Redistribution of soil available nitrogen Model of soil organic matter ROMUL Forest manager Data viewer 3D visualisation Graph interface EFIMOD flow-chart K j4s K j4l H - humus bonded with clay minerals K j5s K j5s K6
Additional ecosystem parameters: Allocation pattern index, AP Turnover capacity, TC An allocation pattern index is AP= LP/FP, where LP is a proportion of NPP for leaves synthesis; FP is the proportion of NPP going for fine root growth. Jack pine AP for young and mean-aged trees is.7...75, and for Scots pine it is 1.. Black spruce has AP.13..., and Norway spruce -.96..1.17 Additionally to NEE (net ecosystem exchange) we introduced a parameter of ecosystem processes strength turnover capacity, TC = NPP+Rh+ DIST annually, where NPP is net primary productivity, Rh is soil respiration rate, DL is C losses with disturbances (harvested wood and fires)
Correspondence of turnover capacity, TC with NPP, Rh, disturbance losses, DL and NEE A case of clear cutting with at 7th year.5 Processes, kg C m- ye 1.5 1.5 6 7 8 9 1 11 -.5 NPP -1 Rh TC -1.5 NEE - Simulation steps, years TC = NPP + (Rh + DL) NEE = NPP (Rh +DL) TS reflects a power of all ecosystem s biota functioning and other carbon losses 1
Two sets of simulation scenarios Jack pine Scots pine Black spruce Norway spruce Canadian trees were simulated with native AP and European AP European trees were simulated vice versa in the same way Canadian AP European AP Jack pine Scots pine CANADA Black spruce Norway spruce RUSSIA
First set of runs: Combination of allocation rules 1 1 Jack pine 1 Scots pine Tree C, kg m- 8 6 4 8 6 4 4 6 8 1 Stand age, years 4 6 8 1 Stand age, years 1 3 Black spruce 5 Norway spruce 8 Tree C, kg m- Tree C, kg m- Tree C, kg m- 1 15 1 6 4 5 4 6 8 Stand age, years 1 4 6 Stand age, years Upper lines European APs, lower ones Canadian APs 8 1
Second set of runs: criss-cross simulation 1 1 Canada Canada 8 Jack pine Scots pine 8 Tree C, kg m Tree C, kg m 1 6 4 6 4 5 1 15 1 15 Simulation time, years Simulation time, years 1 1 Russia Black spruce Russia Norway spruce 8 Tree C, kg m 1 Tree C, kg m 5 8 6 4 6 4 5 1 Simulation time, years 15 5 1 Simulation time, years 15
Stand productivity vs TC with Canadian and European AP PINES 4 Growing stock, m3 h Canandian allocation 3 European allocation Regressions Canadian y = -13. + 4.x r=.96; r=.9785; s=17.4 1. Pines..4 TC, kg C m- year-1.6.8 European y = -1.57 + 549.7x r=.98; r=.995; s=1.1 where y is growing stock (m3 ha-1), and x is a mean turnover capacity, TC (kg[c] m- year-1) over 15 year simulation at the end of second 7-year rotation
Stand productivity vs TC with Canadian and European AP SPRUCES 5 Canadian allocation Growing stock, m3 h 4 European allocation 3 Regressions Canadian y = -7.3 + 56.x r =.87; r =.933; s = 19. 1 Spruces...4.6 TC, kg C m- year-1.8 1. European y = -13.1 + 46.1x r =.97; r =.9838; s =.
Discussion and conlusions We propose the allocation pattern index AP = LPE/FPE (leaves production efficiency divided by fine root production efficiency) as an indicator of the ecological adaptation of tree species to edaphic and climatic conditions. The allocation pattern clearly reflects the plant s evolutionary and ecological strategy. The significant difference in the allocation of organic carbon between functionally important tree components reflects the difference of life strategies of European and Canadian coniferous species. In the relatively mild climate of European boreal forests, the allocation of carbon to fine root production is lower than the same for Canadian species in the extra continental climate of Central Canada, where the allocation of carbon to fine root production is dominating. Forest ecosystem with rather high NPP and high turnover capacity TC can have various levels of wood productivity in dependence of allocation pattern AP. Landsberg (3) accentuated a lack of attention to this aspect in forest ecology in contrast with agricultural science. Norway spruce will not reach the presented above simulated values in Canadian boreal forest because it is sensitive to late spring frosts and summer drought. It also can suffer from these stresses in combination with poorer efficiency of small fine roots biomass that can not consume all nutrients from the cold slowly mineralizing SOM. These stress reactions are not directly reflected in the EFIMOD structure. There is a challenge for future experimental study of the NPP allocation patterns in wide range of tree species and limits of AP ontogenetic changes in more detail with a special reference to fine roots dynamics, carbon budget and wood productivity.
Discussion and conlusions These results reflect the adaptation of Canadian coniferous species to severe soil climatic conditions that are very cold in the north and very dry in the south part of central Canadian boreal forests. The dominance of root increment in these conditions seems to be a mechanism of tree adaptation. The lower production of Canadian coniferous forests is an ecological payment for trees and ecosystem stability in severe continental climate of Central Canada. The AP is proposed to be a measure of tree stress tolerance and adaptation to severe climatic conditions. The levels of growing stock clearly show that merchantable wood production is strongly dependent on allocation pattern AP at the same values of carbon turnover capacity of the ecosystem TC.
Acknowledgements Funding for this study was provided, in part, by Federal Panel on Energy Research and Development (PERD), Canada
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