Methodological issues

Cropland remaining cropland

Cropland category includes all annual and perennial crops including orchards and poplar plantations; the change in biomass growth has been estimated only for perennial crops, since, for annual crops, the increase in biomass stocks in a single year is assumed equal to biomass losses from harvest and mortality in that same year. Activity data for cropland remaining cropland have been subdivided into annual and perennial crops.

The CSC in Cropland remaining Croplands have been estimated for the following pools;

Biomass growth of perennial crops including Poplar plantations,

Biomass gain/loss for conversions between annual and perennial croplands, CSC in mineral soils for conversions between annual and perennial croplands, Emissions from organic soils in croplands.

A combination of Tier 1 and 2 has been applied to calculate biomass increase for perennial croplands with Gain-Loss method. The areas of perennial woody cropland were multiplied by a net estimate of biomass accumulation from growth and subtract losses associated with harvest or gathering or disturbance (according to Equation 2.7 in Chapter 2 in IPCC).

A Tier 2 approach was used for the conversions between perennial and annual croplands. Tier 2 methods were used for CSC in organic and mineral soils (spatially explicit classification of these lands).

Concerning woody crops, estimates of carbon stocks changes in living biomass were applied to aboveground biomass (belowground was estimated just for poplars), according to the GPG (IPCC, 2003), as there is not sufficient information to estimate carbon stocks change in dead organic matter pools. To assess change in carbon in cropland biomass, the combination of Tier 1 and Tier 2 based on disaggregated aerial data for climate and soil types has been used; therefore a combination of default and country specific factors have been applied.

Biomass accumulation and harvesting

The gain-loss method of GPG 2003 was used (Eq 3.1.1). Biomass accumulation rate for perennial crops on Cropland remaining croplands have been taken as 1 tonnes C ha-1yr-1 based on values used by Italy inventory. The biomass accumulation rate we used in the last submission was the default 2.1 C ha-1yr-1 but based on expert discussions we decided to use the values used by neighboring countries for comparability reasons. Therefore biomass accumulation rate has been assumed to be 1 tonnes C ha-1_yr-1 with a rotation period of 20 years and we also assume 10 years growth and 10 years stable (pruning and slow down of growth) periods similar to the mentioned inventory (NIR 2013 Italy, page 209).

For the estimation of CSC in polar plantations we used a database that covers the period 2003-2010. These values were extrapolated to 2011 and to the period before 2003. The poplar plantations were disaggregated for soil and default IPCC climate types.

The properties that were used to calculate CSC in poplars were a follows;

7.23. Properties of poplar species planted in Turkey (Gülbaba, 2010, Birler, 2010, Zabek and Prescott, 2006). Tree BWD (g/cm3₎ Plantation Pattern # of trees per ha Volume increment (m3/ha-yr) Rotation period (years) BEF R Common poplar species average (P. tremula, P. nigra) 0,40 5x6 333 28 12 1,24 0,21

BWD: Basic wood density, BEF: Biomass expansion factor, R: Root to shoot ratio.

In the calculation procedure we assumed that 12 percent of the poplar plantations are harvested every year considering the rotation period as 12 years.

Conversions between perennial and annual croplands

We used spatially explicit data to calculate conversions between perennial and annual croplands (Table 7.25).

7.25. Conversions between annual and perennial crops within cropland category for soil and climate types.

Annual to perennial Perennial to annual

(Ha) 1990 2000 2006 1990 2000 2006 HAC W-D 17.661,76 9.8952,79 51.135,00 69.373,00 24.767,68 51.006,00 W-W 606,35 11.374,78 5.040,40 8.136,99 851,78 5.137,20 C-D 221,27 3.274,87 1.478,60 2.301,12 303,30 1.478,50 C-W 52,47 72,85 60,90 51,00 74,96 60,90 LAC W-D 667,37 2.625,85 1.473,80 1.838,30 901,69 1.452,60 W-W 248,18 6.144,22 2.676,00 4.399,80 354,54 2.734,10 C-D 1,38 0,00 0,80 0,00 1,98 0,80 C-W 0,00 0,68 0,30 0,48 0,00 0,30 SANDY W-D 366,78 2.901,40 1.410,40 2.045,47 531,45 1.422,00 W-W 0,00 0,00 0,00 0,00 0,00 0,00 C-D 0,00 0,15 0,10 0,00 0,00 0,00 C-W 0,00 0,00 0,00 0,00 0,00 0,00 WET W-D 45,33 77,00 58,40 53,91 64,76 58,40 W-W 0,00 0,00 0,00 0,00 0,00 0,00 C-D 0,00 0,00 0,00 0,00 0,00 0,00 C-W 0,00 0,00 0,00 0,00 0,00 0,00

For the estimation of C stocks in biomass of perennial crops we had used country specific age and aerial distribution values in the last submission which resulted in very large C pools in aboveground biomass. The aboveground C stock of a perennial land was assumed to be 81.2 Mg C/ha in the last submission. This value has been considered as an overestimation by the group of experts and we used the value of 10 C ha-1yr-1 also used by Italy (NIR 2013 Italy, page 209).

2013 submission

38,7 * 2,1 = 81,2 Mg C/ha (IPCC GPG default is 30 years age and 63 MgC/ha)

2014 submission

20/2 * 1 = 10 Mg C/ha (20 years rotation period. 10 years growth 10 years stable)

The conversions between annual and perennial products and vice versa were calculated based on these CSC values.

We used IPCC GPG default EFs to estimate CSC in mineral and organic soils (GPG Table 3.3.5). In case of emissions from organic soils we assumed that all croplands are managed (conservative approach).

Land converted to cropland

Grassland converted to cropland

CSC in biomass and soil pools have been calculated in this category. CSC estimations for

Grasslands converted to Perennial croplands Grasslands converted to Annual croplands

were estimated. We used gain-loss method of GPG 2003 (Eq 3.1.1).

The default C stock value of 5 Mg C/ha in aboveground biomass were used for annual crops while 10 Mg C/ha was taken for perennial crops.

The aboveground C stock for grasslands have been taken as 0,735 Mg C/ha, and belowground 2,94 Mg C/ha (Aydın and Uzun, 2005; Fırıncıoğlu et al., 2009; Sinoga et al., 2012).

In case of emissions from organic soils we assumed that all grasslands are managed (conservative approach).