Dataset associated with ‘Carbon emissions from dryland shifting cultivation: a case study of Mexican tropical dry forest’

This dataset includes the carbon stocks and estimation of fluxes under different maize production scenarios in a Mexican Tropical Dry Forest. This dataset was obtained from two rural communities (Tonaya and El Temazcal) with Tropical Dry Forest in Jalisco state (19°42´N, 103°54´W), western Mexico, at approximately 990 m a.s.l. Calculations were based on the area needed to produce 1 Mg maize in two agricultural systems; 3.33 for permanent agriculture (PA) and 3.6 for shifting cultivation (SC) (0.6 ha for cultivation and 3 for fallow). Average maize yields used in calculation were 1.684 Mg ha–1 for SC and 3.768 Mg ha–1 for PA. The regular SC cycle was considered to be 2 years of cultivation phase followed by 10 years in fallow phase (with three different phases). Field based forest carbon measurements were performed for both agricultural systems and this carbon stock were used in all the calculations. Carbon emissions in each scenario were evaluated through comparison between the different SC production regimes and areas untouched by production (remaining areas), which was defined as baseline state. Carbon stock for cultivation phase was 62.72 Mg ha-1, 47.12 Mg ha-1 for phase one of fallow, 61.21 Mg ha-1 for phase two of fallow, 67.99 Mg ha-1 for phase three of fallow and 70.63 Mg ha-1 for untouched areas. The carbon stocks and fluxes estimation were evaluated under three scenarios: A) comparison of carbon stocks and emissions of SC versus PA over a regular SC cycle, B) estimating carbon impacts of changing lengths of fallow of SC and C) evaluate the effect land pressure on carbon stocks and emissions in a SC system. In case A, annualized emissions from PA and SC per Mg of maize produced by year were obtained. PA only included soil carbon. Carbon stock include in SC were the weighted values of those of the cultivation phase and the different fallow phases. For case B, three lengths of SC were used: 1) 6 year cycle, 2) 12 year cycle and 3) 24 year cycle. In this case yields of maize remain constant at the different cycle lengths modeled. Emissions per Mg of maize produced by year were obtained. For 1 and 2, there is an area untouched by production and retain their baseline state. Carbon stock include in SC were also the weighted values of those of the cultivation phase and the different fallow phases. The final scenario C considers what would happen if under land pressure, peasant needs to produce more food from the same area. In this case, 4 Mg of maize are produced in the same area instead of 1, in a 6 year CS cycle. There is no areas untouched by production. Carbon stock include in SC cycle were those of the cultivation phase and first fallow phase, this last because SC cycle length included just this fallow phase. Carbon stocks and carbon emissions per Mg of maize produced by year are presented for this case. Area needed to produce 1 Mg maize in this case was 7.2 ha.

该数据集包含墨西哥热带干旱森林（Tropical Dry Forest）中不同玉米生产情景下的碳储量及通量估算。数据集来源于墨西哥西部哈利斯科州（北纬19°42′，西经103°54′）的两个农村社区（Tonaya和El Temazcal），地处热带干旱森林区域，海拔约990米（a.s.l.，即above sea level）。计算基于两种农业系统生产1吨（Mg，megagram）玉米所需的面积：永久农业（PA，Permanent Agriculture）为3.33公顷，轮垦农业（SC，Shifting Cultivation）为3.6公顷（含0.6公顷耕作区与3公顷休耕区）。计算采用的平均玉米产量为：轮垦农业（SC）1.684吨/公顷，永久农业（PA）3.768吨/公顷。常规轮垦农业（SC）周期设定为2年耕作期加10年休耕期（含三个阶段）。对两种农业系统均开展实地森林碳储量测量，所得数据用于所有计算。各情景碳排放通过比较不同轮垦农业（SC）生产模式与未受生产影响区域（剩余区域，定义为基准状态）评估。耕作期碳储量为62.72吨/公顷，休耕一期47.12吨/公顷，休耕二期61.21吨/公顷，休耕三期67.99吨/公顷，未受影响区域70.63吨/公顷。碳储量及通量估算涵盖三种情景：A）常规SC周期内SC与PA的碳储量及排放对比；B）SC休耕期长度变化的碳影响估算；C）SC系统中土地压力对碳储量及排放的效应评估。情景A中，得出PA与SC每生产1吨玉米的年度化排放量（PA仅含土壤碳，SC碳储量为耕作期与各休耕期加权值）。情景B采用三种SC周期长度（6/12/24年），不同周期下玉米产量恒定，得出每年每生产1吨玉米的排放量；情景1/2存在未受影响区域且保留基准状态，SC碳储量为耕作期与各休耕期加权值。情景C考虑土地压力下农民需在同一区域增产的情况：6年SC周期内同一区域生产4吨玉米，无未受影响区域，SC碳储量为耕作期与休耕一期之和（周期仅含此休耕阶段），提供每年每生产1吨玉米的碳储量及排放数据，生产1吨玉米需7.2公顷。