Low Carbon in Pekarangan

Pekarangan, a traditional biodiversity-low carbon system in Indonesia to establish green procurement, promote greening, and set green guidelines, species diversity, or biodiversity plays an important role in sustaining the ecosystem at present and in the future (Arifin and Nakagoshi 2011). Pekarangan is a common smallholder agrofor­estry system in Indonesia and throughout the tropics, from the rural to the urban areas (Arifin 1998). These species-rich, tree-based systems produce non-wood and wood products for both home use and market sale. High biodiversity is an intrinsic property of the home gardens (Kumar 2006), which presumably favors greater net primary productivity (NPP) and higher C sequestration potential than monospecific production systems. Projections by Roshetko et al. (2002) revealed that, depending

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I-2

 

Low Carbon in Pekarangan

0 20 40 60 80 100

M-1

 

0 20 40 60 80 100

M-2

 

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Individual Number (%)

 

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Low Carbon in Pekarangan

Fig. 8.1 Percentage of individual plant number in each stratum by urbanization level in 1996 (above) and in 2006 (bottom). L-I, the least urbanized area; I-1, I-2, I-3, intermediate urbanized areas; M-1, M-2, the most urbanized area); 1st strata, 0-1 m; 2nd strata, 1-2 m; 3rd strata, 2-5 m; 4th strata, 5-10 m; 5th strata, >10 m

 

Low Carbon in PekaranganLow Carbon in PekaranganLow Carbon in Pekarangan

on management options, the time-averaged above-ground C stocks of pekarangan systems could vary from 30 to 123 Mg C ha-1. These projected time-averaged above-ground C stocks of pekarangans are substantially higher than those of Imperata-cassava systems (2.2 Mg C ha-1), which is an extensive vegetation type in the Lampung study area. Pekarangan research showed these systems simulta­neously offer potential for C storage because of their high biomass. Although small size limits the amount of C stored by individual smallholder agroforestry systems, on a per area basis these systems can store as much C as some secondary forests. In aggregate, smallholder pekarangan agroforestry systems can contribute signifi­cantly to a regional C budget while simultaneously enhancing smallholder liveli­hoods. A field study in other areas outside Java Island, that is, Lampung, Indonesia indicates that pekarangans with an average age of 13 years store 35.3 Mg C ha-1 in their above-ground biomass, which is on par with the C stocks reported for similar- aged secondary forests in the same area (Roshetko et al. 2002).

Some experimental evidence also suggests that plant diversity and composition influence the enhancement of biomass and C acquisition in ecosystems subjected to elevated atmospheric CO2 concentrations (Kumar 2006). Reich et al. (2001) reported that biomass accumulation was greater in species-rich than in species- poor experimental populations under conditions of CO2 and N fertilization. By extension, home gardens, which are inherently species rich, may trap progressively greater quantities of atmospheric CO2 under rising levels of this gas.

If pekarangan systems and other smallholder tree-based systems were to expand in currently degraded and underutilized lands, such as Imperata grasslands, the C seques­tration potential would be about 80 Mg C ha-1, with considerable variation depending on species composition and management practices. Clearly, opportunity exists to induce management that leads to higher C stocks at the systems level. However, incentive mechanisms are needed that assure smallholders will benefit from selecting management practices that favor higher C stocks (Arifin and Nakagoshi 2011).

8.3 Summary

Published articles and a dissertation (Arifin 1998) such as those on pekarangan defined that Indonesian home gardens are generally regarded as a complex, species – rich agroforestry system, a diverse mixture of perennial and annual plant species arranged in a multilayered vertical structure, often in combination with raising livestock managed in a sustainable manner over decades or even centuries. A wide spectrum of multiple-use products can be generated with relatively low labor, cash, or other external inputs. In many densely populated tropical regions, pekarangan appear to be the last forest-like islands surrounded by increasingly extended, uniform staple crop fields. Some research sponsored by the Core University Research Program JSPS Japan/DGHE Indonesia, and STORMA Germany (1998­2007), concluded that with their multilayered vegetation structure, pekarangan serves as an important habitat for included wild flora and fauna.

Pekarangan fulfils not only important ecological but also many social and cultural functions (Arifin et al. 1998; Arifin et al. 2001). However, the major purposes of pekarangan are subsistence production and income generation, partic­ularly in rural areas (Kehlenbeck et al. 2007). At forest margins, high production levels in pekarangan might help to reduce deforestation. Furthermore, pekarangan should be considered as a model for sustainable agroforestry systems, integrating both economic and ecological benefits.

Acknowledgments The authors express our gratitude to the Directorate General of Higher Education (DGHE/DIKTI), Republic of Indonesia for its support of our research through a competency grant (Hibah Kompetensi) for 2008-2010 and Graduate Team Research Grant (Hibah Penelitian Tim Pascasarjana – HPTP) for 2006-2008; and thanks to Rural Development Institute—Seattle US for pekarangan research on Java during 2006-2008. Finally, thanks to the Global Environmental Leaders (GELs) Education Program for Designing a Low Carbon Society (LCS) of Hiroshima University, Japan for research collaboration for 2009-2013.