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56 | 56 | ||
57 | Snag::Snag() |
57 | Snag::Snag() |
58 | {
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58 | {
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59 | mRU = 0; |
59 | mRU = 0; |
60 | CNPool::setCFraction(biomassCFraction); |
60 | CNPool::setCFraction(biomassCFraction); |
61 | Snag::setupThresholds( |
61 | Snag::setupThresholds(20., 60.); |
62 | }
|
62 | }
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63 | 63 | ||
64 | void Snag::setup( const ResourceUnit *ru) |
64 | void Snag::setup( const ResourceUnit *ru) |
65 | {
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65 | {
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66 | mRU = ru; |
66 | mRU = ru; |
Line 84... | Line 84... | ||
84 | {
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84 | {
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85 | // list columns
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85 | // list columns
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86 | // for three pools
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86 | // for three pools
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87 | QList<QVariant> list; |
87 | QList<QVariant> list; |
88 | 88 | ||
89 |
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89 | // totals
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- | 90 | list << mTotalSnagCarbon << mTotalIn.C << mTotalToAtm.C << mSWDtoSoil.C << mSWDtoSoil.N; |
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90 | // fluxes to labile soil pool and to refractory soil pool
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91 | // fluxes to labile soil pool and to refractory soil pool
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91 | list << mLabileFlux.C << mLabileFlux.N << mRefractoryFlux.C << mRefractoryFlux.N << mSWDtoSoil.C << mSWDtoSoil.N; |
92 | list << mLabileFlux.C << mLabileFlux.N << mRefractoryFlux.C << mRefractoryFlux.N << mSWDtoSoil.C << mSWDtoSoil.N; |
92 | 93 | ||
93 | for (int i=0;i<3;i++) { |
94 | for (int i=0;i<3;i++) { |
94 | // pools "swdx_c", "swdx_n", "swdx_count", "swdx_tsd", "toswdx_c", "toswdx_n"
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95 | // pools "swdx_c", "swdx_n", "swdx_count", "swdx_tsd", "toswdx_c", "toswdx_n"
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Line 125... | Line 126... | ||
125 | double rel_wc; |
126 | double rel_wc; |
126 | double ft, fw; |
127 | double ft, fw; |
127 | double f_sum = 0.; |
128 | double f_sum = 0.; |
128 | for (const ClimateDay *day=mRU->climate()->begin(); day!=mRU->climate()->end(); ++day) |
129 | for (const ClimateDay *day=mRU->climate()->begin(); day!=mRU->climate()->end(); ++day) |
129 | {
|
130 | {
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130 | rel_wc = mRU->waterCycle()->relContent(day->day); // relative water content |
131 | rel_wc = mRU->waterCycle()->relContent(day->day)*100.; // relative water content in per cent of the day |
131 | ft = exp(308.56*(1./56.02-1./((273.+day->temperature)-227.13))); // empirical variable Q10 model of Lloyd and Taylor (1994), see also Adair et al. (2008) |
132 | ft = exp(308.56*(1./56.02-1./((273.+day->temperature)-227.13))); // empirical variable Q10 model of Lloyd and Taylor (1994), see also Adair et al. (2008) |
132 | fw = pow(1.-exp(-0.2*rel_wc),5.); // # see Standcarb for the 'stable soil' pool |
133 | fw = pow(1.-exp(-0.2*rel_wc),5.); // # see Standcarb for the 'stable soil' pool |
133 | f_sum += ft*fw; |
134 | f_sum += ft*fw; |
134 | }
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135 | }
|
135 | // the climate factor is defined as the arithmentic annual mean value
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136 | // the climate factor is defined as the arithmentic annual mean value
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Line 145... | Line 146... | ||
145 | if (isEmpty()) // nothing to do |
146 | if (isEmpty()) // nothing to do |
146 | return; |
147 | return; |
147 | 148 | ||
148 | // process branches: every year one of the five baskets is emptied and transfered to the refractory soil pool
|
149 | // process branches: every year one of the five baskets is emptied and transfered to the refractory soil pool
|
149 | mRefractoryFlux+=mBranches[mBranchCounter]; |
150 | mRefractoryFlux+=mBranches[mBranchCounter]; |
- | 151 | mSWDtoSoil += mBranches[mBranchCounter]; |
|
150 | mBranches[mBranchCounter].clear(); |
152 | mBranches[mBranchCounter].clear(); |
151 | mBranchCounter= (mBranchCounter+1) % 5; // increase index, roll over to 0. |
153 | mBranchCounter= (mBranchCounter+1) % 5; // increase index, roll over to 0. |
152 | 154 | ||
153 | // process standing snags.
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155 | // process standing snags.
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154 | // the input of the current year is in the mToSWD-Pools
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156 | // the input of the current year is in the mToSWD-Pools
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Line 165... | Line 167... | ||
165 | }
|
167 | }
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166 | 168 | ||
167 | if (mSWD[i].C > 0) { |
169 | if (mSWD[i].C > 0) { |
168 | // reduce the Carbon (note: the N stays, thus the CN ratio changes)
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170 | // reduce the Carbon (note: the N stays, thus the CN ratio changes)
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169 | // use the decay rate that is derived as a weighted average of all standing woody debris
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171 | // use the decay rate that is derived as a weighted average of all standing woody debris
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170 |
|
172 | double survive_rate = exp(-mKSW[i] *climate_factor_re * 1. ); // 1: timestep |
- | 173 | mTotalToAtm.C += mSWD[i].C * (1. - survive_rate); |
|
- | 174 | mSWD[i].C *= survive_rate; |
|
171 | 175 | ||
172 | // transition to downed woody debris
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176 | // transition to downed woody debris
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173 | // update: use negative exponential decay, species parameter: half-life
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177 | // update: use negative exponential decay, species parameter: half-life
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174 | // modified for the climatic effect on decomposition, i.e. if decomp is slower, snags stand longer and vice versa
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178 | // modified for the climatic effect on decomposition, i.e. if decomp is slower, snags stand longer and vice versa
|
175 | // this is loosely oriented on Standcarb2 (http://andrewsforest.oregonstate.edu/pubs/webdocs/models/standcarb2.htm),
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179 | // this is loosely oriented on Standcarb2 (http://andrewsforest.oregonstate.edu/pubs/webdocs/models/standcarb2.htm),
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Line 185... | Line 189... | ||
185 | 189 | ||
186 | // higher decay rate for the class with smallest diameters
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190 | // higher decay rate for the class with smallest diameters
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187 | if (i==0) |
191 | if (i==0) |
188 | rate*=2.; |
192 | rate*=2.; |
189 | 193 | ||
190 | double transfer = exp(rate); |
194 | double transfer = 1. - exp(rate); |
191 | 195 | ||
192 | // calculate flow to soil pool...
|
196 | // calculate flow to soil pool...
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193 | mSWDtoSoil += mSWD[i] * transfer; |
197 | mSWDtoSoil += mSWD[i] * transfer; |
194 | mRefractoryFlux += mSWD[i] * transfer; |
198 | mRefractoryFlux += mSWD[i] * transfer; |
195 | mSWD[i] *= (1.-transfer); // reduce pool |
199 | mSWD[i] *= (1.-transfer); // reduce pool |
196 | // calculate the stem number of remaining snags
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200 | // calculate the stem number of remaining snags
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197 | mNumberOfSnags[i] = mNumberOfSnags[i] * (1. - transfer); |
201 | mNumberOfSnags[i] = mNumberOfSnags[i] * (1. - transfer); |
- | 202 | ||
- | 203 | mTimeSinceDeath[i] += 1.; |
|
198 | // if stems<0.5, empty the whole cohort into DWD, i.e. release the last bit of C and N and clear the stats
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204 | // if stems<0.5, empty the whole cohort into DWD, i.e. release the last bit of C and N and clear the stats
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199 | // also, if the Carbon of an average snag is less than 10% of the original average tree
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205 | // also, if the Carbon of an average snag is less than 10% of the original average tree
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200 | // (derived from allometries for the three diameter classes), the whole cohort is emptied out to DWD
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206 | // (derived from allometries for the three diameter classes), the whole cohort is emptied out to DWD
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201 | if (mNumberOfSnags[i] < 0.5 || mSWD[i].C / mNumberOfSnags[i] < mCarbonThreshold[i]) { |
207 | if (mNumberOfSnags[i] < 0.5 || mSWD[i].C / mNumberOfSnags[i] < mCarbonThreshold[i]) { |
202 | // clear the pool: add the rest to the soil, clear statistics of the pool
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208 | // clear the pool: add the rest to the soil, clear statistics of the pool
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Line 243... | Line 249... | ||
243 | // branches are equally distributed over five years:
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249 | // branches are equally distributed over five years:
|
244 | double biomass_branch = tree->biomassBranch() * 0.2; |
250 | double biomass_branch = tree->biomassBranch() * 0.2; |
245 | for (int i=0;i<5; i++) |
251 | for (int i=0;i<5; i++) |
246 | mBranches[i].addBiomass(biomass_branch, soil_params.cnWood); |
252 | mBranches[i].addBiomass(biomass_branch, soil_params.cnWood); |
247 | 253 | ||
- | 254 | // just for book-keeping: keep track of all inputs into branches / swd
|
|
- | 255 | mTotalIn.addBiomass(tree->biomassBranch() + tree->biomassStem(), soil_params.cnWood); |
|
248 | // stem biomass is transferred to the standing woody debris pool (SWD), increase stem number of pool
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256 | // stem biomass is transferred to the standing woody debris pool (SWD), increase stem number of pool
|
249 | int pi = poolIndex(tree->dbh()); // get right transfer pool |
257 | int pi = poolIndex(tree->dbh()); // get right transfer pool |
250 | CNPool &swd = mToSWD[pi]; |
- | |
251 | swd.addBiomass(tree->biomassStem(), soil_params.cnWood); |
- | |
252 | 258 | ||
253 | // update statistics - stemnumber-weighted averages
|
259 | // update statistics - stemnumber-weighted averages
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254 | // note: here the calculations are repeated for every died trees (i.e. consecutive weighting ... but delivers the same results)
|
260 | // note: here the calculations are repeated for every died trees (i.e. consecutive weighting ... but delivers the same results)
|
255 | double p_old = mNumberOfSnags[pi] / (mNumberOfSnags[pi] + 1); // weighting factor for state vars (based on stem numbers) |
261 | double p_old = mNumberOfSnags[pi] / (mNumberOfSnags[pi] + 1); // weighting factor for state vars (based on stem numbers) |
256 | double p_new = 1. / (mNumberOfSnags[pi] + 1); // weighting factor for added tree (p_old + p_new = 1). |
262 | double p_new = 1. / (mNumberOfSnags[pi] + 1); // weighting factor for added tree (p_old + p_new = 1). |
Line 266... | Line 272... | ||
266 | throw IException("Snag::addMortality: tree without stem biomass!!"); |
272 | throw IException("Snag::addMortality: tree without stem biomass!!"); |
267 | p_old = mToSWD[pi].C / (mToSWD[pi].C + tree->biomassStem()* biomassCFraction); |
273 | p_old = mToSWD[pi].C / (mToSWD[pi].C + tree->biomassStem()* biomassCFraction); |
268 | p_new =tree->biomassStem()* biomassCFraction / (mToSWD[pi].C + tree->biomassStem()* biomassCFraction); |
274 | p_new =tree->biomassStem()* biomassCFraction / (mToSWD[pi].C + tree->biomassStem()* biomassCFraction); |
269 | mCurrentKSW[pi] = mCurrentKSW[pi]*p_old + soil_params.ksw * p_new; |
275 | mCurrentKSW[pi] = mCurrentKSW[pi]*p_old + soil_params.ksw * p_new; |
270 | mNumberOfSnags[pi]++; |
276 | mNumberOfSnags[pi]++; |
- | 277 | ||
- | 278 | // finally add the biomass
|
|
- | 279 | CNPool &swd = mToSWD[pi]; |
|
- | 280 | swd.addBiomass(tree->biomassStem(), soil_params.cnWood); |
|
271 | }
|
281 | }
|
272 | 282 | ||
273 | /// add residual biomass of 'tree' after harvesting.
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283 | /// add residual biomass of 'tree' after harvesting.
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274 | /// remove_{stem, branch, foliage}_fraction: percentage of biomass compartment that is *removed* by the harvest operation (i.e.: not to stay in the system)
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284 | /// remove_{stem, branch, foliage}_fraction: percentage of biomass compartment that is *removed* by the harvest operation (i.e.: not to stay in the system)
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275 | /// the harvested biomass is collected.
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285 | /// the harvested biomass is collected.
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Line 283... | Line 293... | ||
283 | mLabileFlux.addBiomass(tree->biomassFineRoot(), soil_params.cnFineroot); |
293 | mLabileFlux.addBiomass(tree->biomassFineRoot(), soil_params.cnFineroot); |
284 | mRefractoryFlux.addBiomass(tree->biomassCoarseRoot(), soil_params.cnWood); |
294 | mRefractoryFlux.addBiomass(tree->biomassCoarseRoot(), soil_params.cnWood); |
285 | 295 | ||
286 | // residual branches are equally distributed over five years:
|
296 | // residual branches are equally distributed over five years:
|
287 | for (int i=0;i<5; i++) |
297 | for (int i=0;i<5; i++) |
288 | mBranches[i].addBiomass(tree->biomassBranch() * remove_branch_fraction * 0.2, soil_params.cnWood); |
298 | mBranches[i].addBiomass(tree->biomassBranch() * (1. - remove_branch_fraction) * 0.2, soil_params.cnWood); |
289 | 299 | ||
- | 300 | mTotalToExtern.addBiomass(tree->biomassBranch()*remove_branch_fraction + tree->biomassStem()*remove_stem_fraction, soil_params.cnWood); |
|
290 | // stem biomass is transferred to the standing woody debris pool (SWD), increase stem number of pool
|
301 | // stem biomass is transferred to the standing woody debris pool (SWD), increase stem number of pool
|
291 | // TODO: what to do with harvest and stems??? I think harvested stems (that are not removed) should
|
302 | // TODO: what to do with harvest and stems??? I think harvested stems (that are not removed) should
|
292 | // go directly to the DWD??
|
303 | // go directly to the DWD??
|
293 | CNPool &swd = mToSWD[poolIndex(tree->dbh())]; // get right transfer pool |
304 | CNPool &swd = mToSWD[poolIndex(tree->dbh())]; // get right transfer pool |
294 | swd.addBiomass(tree->biomassStem() * remove_stem_fraction, soil_params.cnWood); |
305 | swd.addBiomass(tree->biomassStem() * remove_stem_fraction, soil_params.cnWood); |