Effects of subsistence farming system on soil surface CO 2 –C ﬂux on Cofre de Perote volcano slopes, Veracruz (Mexico) Adolfo Campos C. * Instituto de Ecologia, A.C. Apartado Postal 63, C.P. 91000 Xalapa, Veracruz, Mexico Received 24 September 2003; received in revised form 2 December 2003; accepted 16 May 2004 Abstract Mountainous parts of the eastern slope of the Mexican Cofre de Perote volcano have suffered great ecological disturbance due to the conversion of forest to subsistence corn (Zea mays) cropland. This research was conducted in order to evaluate the response of surface soil CO 2 –C ﬂux to land use modiﬁcation, speciﬁcally the adoption of subsistence farming in this mountainous forest–cropland setting. The treatments consisted of a corn plot (CP), recently abandoned cropland (RA), old abandoned cropland (OA), and coniferous (Pinus species) forestland (CF). For an 8-month period (August 1999–June 2000), CO 2 –C ﬂux concentration was measured monthly using the static chamber method. CO 2 –C ﬂux ranged from 1.80 to 5.22 g C m 2 /day in the CF treatment, 2.76–8.45 g C m 2 /day in the CP treatment, 3.24–7.48 g C m 2 /day in the RA treatment, to 2.99–8.84 g C m 2 /day in the OA treatment. Results showed that the conversion of coniferous forest to corn cropland leads to a signiﬁcant increase in CO 2 –C ﬂux concentration from the soil surface to the atmosphere. There were few differences between current and former agricultural plots, demonstrating that crop abandonment did not lower CO 2 –C ﬂux from the soil’s surface. Soil temperature and moisture content were poorly correlated with CO 2 –C ﬂux; however, soil moisture data did show greater scattering. This indicates that soil temperature had a major effect on CO 2 –C ﬂux concentration. To offset some of the organic carbon depletion from soil caused by land use change, it is recommended that the subsistence farming system subject corn crop residue to a composting process. This can improve short-term soil fertility and increase corn crop yield, playing a central role in converting abandoned cropland into permanent cultures that facilitate forest conservation. # 2004 Elsevier B.V. All rights reserved. Keywords: CO 2 –C ﬂux; Corn; Forest; Subsistence farming; Abandoned cropland; Mountain landscape 1. Introduction Soil processes are an important part of the global carbon cycle, not only because of atmospheric CO 2 –C sequestration but also their contribution to annual greenhouse effect gas ﬂux (Bajracharya et al., 2000; Torbert et al., 2000). CO 2 –C ﬂux from the soil surface to the atmosphere is the result of root respiration and the decomposition of organic products by microorgan- isms and invertebrates. CO 2 –C ﬂux is direct evidence of carbon loss and nutrient recycling (Mielnick and Dugas, 2000; Rustad et al., 2000; Marschner and Kalbitz, 2003). It is estimated that the CO 2 –C ﬂux produced by soil respiration processes varies from 75 to 80 Gt/year and is equivalent to 10% of the atmo- sphere’s CO 2 –C (Raich and Schlesinger, 1992; Raich and Potter, 1995; Raich and Tufekcioglu, 2000; Raich et al., 2002; Schlesinger and Andrews, 2000). Agro- forestry activities that affect CO 2 –C release to the Forest Ecology and Management 199 (2004) 273–282 * Tel.: þ52 228 842 1832; fax: þ52 228 818 7809. E-mail address: camposad@ecologia.edu.mx (A. Campos C.). 0378-1127/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2004.05.045