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O. Ferreira1, 2 *, M. P. Hurtado2, M. Rondón3 and I. M. Rao2

                     1   Centro Internacional de Agricultura...
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Poster56: Greenhouse gas fluxes, global warming potential and emergy evaluation of Quesungual slash-and mulch agroforesty system

Poster for CIAT 2009 Knowledge Sharing Week

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Poster56: Greenhouse gas fluxes, global warming potential and emergy evaluation of Quesungual slash-and mulch agroforesty system

  1. 1. O. Ferreira1, 2 *, M. P. Hurtado2, M. Rondón3 and I. M. Rao2 1 Centro Internacional de Agricultura Tropical (CIAT), Cali, Colombia; 2 Escuela Nacional de Ciencias Forestales (ESNACIFOR), Siguatepeque, Honduras; 3 International Development Research Center (IRDC), Ottawa, Canadá. * Corresponding author: oifc.001@ 1. INTRODUCTION Agroforestry systems have the potential to reduce net emissions of greenhouse gases (GHG): nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2); and offset the emissions associated with deforestation and land use change from forest to agriculture (Dixon, 2004). However, data on GHG fluxes between soil and atmosphere, in tropical agroforestry systems are limited (Rondón, 2000). Quesungual Slash-and-Mulch Agroforestry System (QSMAS) is an indigenous system practiced in southern Lempira, Honduras, and it is considered a viable alternative to traditional slash-and-burn system. QSMAS include management technologies of soil, crops and cover and has four basic principles: (1) no slash and burn, (2) permanent soil cover, (3) minimal disturbance of soil, and (4) efficient use of fertilizer (Wélchez et al., 2006). 2. OBJECTIVES 3. MATERIALS AND METHODS The main objectives of this study were (i) to assess GHG fluxes and its annual accumulation, in 5 land uses: QSMAS with three different 3.1 Location: This study was conducted in eight farms (14 º 05 'N, 88 º 30' ages (young, medium and mature), slash-and-burn traditional W) in Candelaria and Gualcinse districts, southern Lempira, Honduras agriculture (SB) and secondary forest (SF), (ii) to quantify global (Figure 2). This site is a tropical dry forest ecosystem (Holdridge warming potential (GWP) of these land uses and (iii) to conduct an classification), with an annual average temperature of 25oC, annual rainfall of emergy evaluation to quantify resources use and sustainability, in 1400 mm (rainy season from May to October), slopes between 5 and 50%, southern Lempira, Honduras (Figure 1 a, b, c). and elevations between 200 and 900 masl. Soils are stony and are classified as Entisols (Lithic Ustorthent, USDA classification) related to intrusive and Hon dura s igneous rocks from Tertiary (Hellin et al., 1999). Fig. 2 3.2 Protocol for GHG determination : For  monitoring  GHG  fluxes  between  soil  and  atmosphere,  we  used  the  closed  chamber  technique, described by Rondón, 2000 (Figure 3). Annual accumulated fluxes for each land use were calculated using GHG fluxes. Fig. 1 b Secondary Forest (SF) a. GHG sampling: At the beginning of the study, 4 PVC rings (height 8 cm, ø = 25 cm) were located in the 15 plots of 200 m² (5 land  uses: SB, QSMAS <2, QSMAS 5‐7, QSMAS >10 years and SF, with 3 replicates for each land use). In every closed chamber (60 in total ‐15  plots and 4 chambers per plot‐) and at each sampling date (16 dates), 4 air samples were taken (at 0, 10, 20 and 30 minutes, after installing  the chamber ‐height 10 cm, ø = 25 cm‐ over the PVC ring). Air samples were extracted from the closed chamber using a syringe with an  adapted valve and then introduced into glass containers (pre‐ vacuumed vials by freeze drying). Fig. 1 a Fig. 1 c b. GHG determination: N2O and CH4 concentrations were determined in the laboratory, using a Shimadzu GC‐14A gas chromatograph,  Quesungual Slash-and-Mulch Agroforestry System equipped  with  FID  (flame  ionization  detector)  and  ECD  (electron  capture  detector)  for  CH4 and  N2O  detection,  respectively.  For  CO2 Slash-and-Burn (SB) (QSMAS) concentration, we used a Qubit Systems S151 gas analyzer, with infrared technology. 3.3 GWP calculation: To calculate GWP of the different land uses, we used CH4 and N2O fluxes between soil and atmosphere, and C  stock  from  soil  and  tree  biomass.  In  traditional  system  of  SB,  we  also  included  direct  emissions  of  CO2,  CH4 and  N2O,  from  the  biomass  burning. GHG fluxes of each land use were multiplied by the global warming potential value, corresponding to the GHG and time horizon  used (CO2=1, CH4=72 and N2O=289, in a 20 years time horizon, IPCC, 2001). 3.4 Emergy evaluation: The emergy is a measure of the total energy used in the past to make a product or service. Diagrams were  elaborated using data from the 15 plots and transformities reported by other authors. Different emergy indices were calculated using the  methodology used by Diemont et al., 2006. The ecological footprint index was derived by dividing the total emergy yielded by a system  by  the  total  renewable  emergy flows  supporting  the  same  system.  The  sustainability  index is  an  aggregate  measure  of  yield  and  sustainability that assumes that the objective function for sustainability is to obtain the highest yield ratio at the lowest environmental  Fig. 3 load. 4. RESULTS GWP (kg CO 2 Equivalents ha-1 yr-1 ) Fig. 4a Fig. 7 Global Warming Potential 5 0 00 0 Fig. 6a Maximum  value  of  GWP  was  founf with  SB  (40940  4 0 00 0 kg  Equiv.  CO2),  followed  by  QSMAS  (10530  kg  Equiv.  3 0 00 0 CO2)  and  SF (1130 kg Equiv. CO2).  This  high  value  of  GWP  showed  by  SB  is  related  to  higher  GHG  2 0 00 0 emissions  and  indicates  that  this  SB  traditional  1 0 00 0 system is markedly contributing to global  warming  than  QSMAS  and  SF  systems,  which  showed  lower  0 Fig. 4b S sh n -B rn la -a d u Q MS SA S n a F re eco d ry o st values  of  GWP,  indicating  less  disturbed  systems  (Figure 7). Fig. 6b Fig. 8 2.0 5. CONCLUSIONS Ecological Footprint Index •GHG  fluxes  showed  a  seasonal  behavior,  with  1.5 higher emissions during the rainy season.  1.0 •Quesungual (QSMAS)  and  secondary  forest  (SF)  Fig. 4c systems  were  net  methane  sinks.  On  the  other  0.5 hand,  slash  and  burn  (SB)  system  was  the  net  source  of  methane;  methane  emission  being  a  0.0 good parameter to evaluate appropriate soil and  Slash-and-Burn QSMAS Secondary Forest cover management. Fig. 6c Fig. 9 •QSMAS  has  a  small  value  of  GWP,  compared  to  4500 SB, and its behavior is comparable to SF.  Sustainability Index •The  region  of  Southern  Lempira  in  Honduras  is  Fig. 5 3000 not  affecting  regional  balances  of  GHG,  due  to  current  use  of  more  environmentally  friendly  1500 systems, such as SF and QSMAS. •QSMAS  is  a  sustainable  system,  broadly  favoring  0 the  use  of  renewable  and  local  resources,  while  Slash-and-B urn QSM A S S ec ondary Forest SB  traditional  system  is  affecting  the  resources  Annual accumulated GHG fluxes Emergy Evaluation and presenting a low value of sustainability index . GHG fluxes QSMAS  <2,  QSMAS  5‐7,  QSMAS  >  10  and  SF  were  all  An  emergy evaluation  was  conducted  to  quantify  •In  general,  QSMAS  showed  more  environmental  CH4 fluxes showed a range from 147 mg CH4 m‐2 h‐1 net  sinks  of  CH4,  only  SB  was  the  only  net  source  of  the  use  of  resources  and  to  determine  the  benefits  and  advantages  than  SB  traditional  in SF to ‐113 µg CH4 m‐2 h‐1 in QSMAS <2, showing a  CH4.  Range  varied  from  177  mg  CH4 m‐2 yr‐1 for  SB  sustainability  of  the  systems. SB  showed  higher  system. large  temporal  variability  during  the  study  period.  fertilized  to  ‐180  mg  CH4 m‐2 yr‐1 in  QSMAS  <10  value  of  Ecological  Footprint  Index,  followed  by  CO2 fluxes  ranged  from  937  mg  CO2 m‐2 h‐1 in  fertilized. All land uses were net sources of CO2, with a  QSMAS  and  SF,  related  with  the  use  of  local  QSMAS <2 to ‐471.60 mg CO2 m‐2 h‐1 in SB; and N2O  range between 2.27 kg CO2 m‐2 yr‐1 in QSMAS <10 not  resources  (Figure  8).  Emergy Sustainability  Index  fluxes ranged from 288 µg N2O m‐2 h‐1 in QSMAS <2  fertilized  and  0.64  kg  CO2 m‐2 yr‐1 in  SF.  QSMAS  5‐7  of SB was 35, QSMAS 136 and SF 4124, with higher  6. ACKNOWLEDGMENTS to ‐70 µg N2O m‐2 h‐1, also in QSMAS <2 (Figure 4 a,  showed largest emission of N2O, followed by SB; lower  value  of  sustainability  observed  with  QSMAS  and  This  study  was  part  of  the  project  quot;PN15:  b, c), related with dry and rainy periods (Figure 5). emissions  of  N2O  were  observed  in  QSMAS  <2  and  SF  SF,  indicating  that  these  systems  support  the  use  Quesungual Slash  and  Mulch  Agroforestry (Figure 6 a, b, c). of renewable and local resources (Figure 9). System  (QSMAS):  Improving  crop  water  productivity, food security and resource quality in  the  sub‐humid  tropics'  funded  by  the  Challenge  7. REFERENCES CITED Program  on  Water  and  Food  (CPWF)  of  CGIAR  • Diemont S., Martin J., Levy S. 2006. Emergy evaluation of Lacandon Maya indigenous swidden agroforestry in Chiapas, Mexico. Agroforestry Systems 66. pp. 23-42 and  executed  by  the  Consortium  for  the  • Hellin J., Welchez L., Cherrett I. 1999. The Quesungual system: an indigenous agroforestry system from western Honduras. Agroforestry Systems 46. pp. 229-237 Integrated  Management  of  Soils  (MIS)  and  the  • IPCC. 2001. The scientific basis. Intergovernmental Panel on Climate Change. Cambridge University Press. pp. 881 • Rondón. M. 2000. Land use and balances of greenhouse gases in Colombian Tropical Savannas. Ph.D. Thesis. Cornell University. USA. pp. 211 International  Center  for  Tropical  Agriculture  • Wélchez L., Ayarza M., Amézquita E., Barrios E., Rondón M., Rao I. 2006. Unraveling the mysteries of the Quesungual slash and mulch agroforestry. Proceedings of18th (CIAT). World Congress of Soil Science, Philadelphia