WebSVN - public iLand - Diff - Rev 522 and 523

 Snag::Snag()
+{
     mRU = 0;
     CNPool::setCFraction(biomassCFraction);
-    Snag::setupThresholds(mDBHLower, mDBHHigher);
+    Snag::setupThresholds(20., 60.);
+}
 void Snag::setup( const ResourceUnit *ru)
+{
     mRU = ru;
+{
     // list columns
     // for three pools
     QList<QVariant> list;
-    list << mTotalSnagCarbon;
+    // totals
+    list << mTotalSnagCarbon << mTotalIn.C << mTotalToAtm.C << mSWDtoSoil.C << mSWDtoSoil.N;
     // fluxes to labile soil pool and to refractory soil pool
     list << mLabileFlux.C << mLabileFlux.N << mRefractoryFlux.C << mRefractoryFlux.N << mSWDtoSoil.C << mSWDtoSoil.N;
     for (int i=0;i<3;i++) {
         // pools "swdx_c", "swdx_n", "swdx_count", "swdx_tsd", "toswdx_c", "toswdx_n"
     double rel_wc;
     double ft, fw;
     double f_sum = 0.;
     for (const ClimateDay *day=mRU->climate()->begin(); day!=mRU->climate()->end(); ++day)
+    {
-        rel_wc = mRU->waterCycle()->relContent(day->day); // relative water content (0..1) of the day
+        rel_wc = mRU->waterCycle()->relContent(day->day)*100.; // relative water content in per cent of the day
         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)
         fw = pow(1.-exp(-0.2*rel_wc),5.); //  #  see Standcarb for the 'stable soil' pool
         f_sum += ft*fw;
+    }
     // the climate factor is defined as the arithmentic annual mean value
     if (isEmpty()) // nothing to do
         return;
     // process branches: every year one of the five baskets is emptied and transfered to the refractory soil pool
     mRefractoryFlux+=mBranches[mBranchCounter];
+    mSWDtoSoil += mBranches[mBranchCounter];
     mBranches[mBranchCounter].clear();
     mBranchCounter= (mBranchCounter+1) % 5; // increase index, roll over to 0.
     // process standing snags.
     // the input of the current year is in the mToSWD-Pools
+        }
         if (mSWD[i].C > 0) {
             // reduce the Carbon (note: the N stays, thus the CN ratio changes)
             // use the decay rate that is derived as a weighted average of all standing woody debris
-            mSWD[i].C *= exp(-mKSW[i] *climate_factor_re * 1. ); // 1: timestep
+            double survive_rate = exp(-mKSW[i] *climate_factor_re * 1. ); // 1: timestep
+            mTotalToAtm.C += mSWD[i].C * (1. - survive_rate);
+            mSWD[i].C *= survive_rate;
             // transition to downed woody debris
             // update: use negative exponential decay, species parameter: half-life
             // modified for the climatic effect on decomposition, i.e. if decomp is slower, snags stand longer and vice versa
             // this is loosely oriented on Standcarb2 (http://andrewsforest.oregonstate.edu/pubs/webdocs/models/standcarb2.htm),
             // higher decay rate for the class with smallest diameters
             if (i==0)
                 rate*=2.;
-            double transfer = exp(rate);
+            double transfer = 1. - exp(rate);
             // calculate flow to soil pool...
             mSWDtoSoil += mSWD[i] * transfer;
             mRefractoryFlux += mSWD[i] * transfer;
             mSWD[i] *= (1.-transfer); // reduce pool
             // calculate the stem number of remaining snags
             mNumberOfSnags[i] = mNumberOfSnags[i] * (1. - transfer);
+            mTimeSinceDeath[i] += 1.;
             // if stems<0.5, empty the whole cohort into DWD, i.e. release the last bit of C and N and clear the stats
             // also, if the Carbon of an average snag is less than 10% of the original average tree
             // (derived from allometries for the three diameter classes), the whole cohort is emptied out to DWD
             if (mNumberOfSnags[i] < 0.5 || mSWD[i].C / mNumberOfSnags[i] < mCarbonThreshold[i]) {
                 // clear the pool: add the rest to the soil, clear statistics of the pool
     // branches are equally distributed over five years:
     double biomass_branch = tree->biomassBranch() * 0.2;
     for (int i=0;i<5; i++)
         mBranches[i].addBiomass(biomass_branch, soil_params.cnWood);
+    // just for book-keeping: keep track of all inputs into branches / swd
+    mTotalIn.addBiomass(tree->biomassBranch() + tree->biomassStem(), soil_params.cnWood);
     // stem biomass is transferred to the standing woody debris pool (SWD), increase stem number of pool
     int pi = poolIndex(tree->dbh()); // get right transfer pool
-    CNPool &swd = mToSWD[pi];
-    swd.addBiomass(tree->biomassStem(), soil_params.cnWood);
     // update statistics - stemnumber-weighted averages
     // note: here the calculations are repeated for every died trees (i.e. consecutive weighting ... but delivers the same results)
     double p_old = mNumberOfSnags[pi] / (mNumberOfSnags[pi] + 1); // weighting factor for state vars (based on stem numbers)
     double p_new = 1. / (mNumberOfSnags[pi] + 1); // weighting factor for added tree (p_old + p_new = 1).
         throw IException("Snag::addMortality: tree without stem biomass!!");
     p_old = mToSWD[pi].C / (mToSWD[pi].C + tree->biomassStem()* biomassCFraction);
     p_new =tree->biomassStem()* biomassCFraction / (mToSWD[pi].C + tree->biomassStem()* biomassCFraction);
     mCurrentKSW[pi] = mCurrentKSW[pi]*p_old + soil_params.ksw * p_new;
     mNumberOfSnags[pi]++;
+    // finally add the biomass
+    CNPool &swd = mToSWD[pi];
+    swd.addBiomass(tree->biomassStem(), soil_params.cnWood);
+}
 /// add residual biomass of 'tree' after harvesting.
 /// remove_{stem, branch, foliage}_fraction: percentage of biomass compartment that is *removed* by the harvest operation (i.e.: not to stay in the system)
 /// the harvested biomass is collected.
     mLabileFlux.addBiomass(tree->biomassFineRoot(), soil_params.cnFineroot);
     mRefractoryFlux.addBiomass(tree->biomassCoarseRoot(), soil_params.cnWood);
     // residual branches are equally distributed over five years:
     for (int i=0;i<5; i++)
-        mBranches[i].addBiomass(tree->biomassBranch() * remove_branch_fraction * 0.2, soil_params.cnWood);
+        mBranches[i].addBiomass(tree->biomassBranch() * (1. - remove_branch_fraction) * 0.2, soil_params.cnWood);
+    mTotalToExtern.addBiomass(tree->biomassBranch()*remove_branch_fraction + tree->biomassStem()*remove_stem_fraction, soil_params.cnWood);
     // stem biomass is transferred to the standing woody debris pool (SWD), increase stem number of pool
     // TODO: what to do with harvest and stems??? I think harvested stems (that are not removed) should
     // go directly to the DWD??
     CNPool &swd = mToSWD[poolIndex(tree->dbh())]; // get right transfer pool
     swd.addBiomass(tree->biomassStem() * remove_stem_fraction, soil_params.cnWood);

Subversion Repositories public iLand

(root)/src/core/snag.cpp @ 1222 - Rev 522 → 523