Differential influence of land use/cover change on topsoil carbon and microbial activity in low-latitude temperate forests

Land use/cover change (LUCC) is one of the main factors that control the terrestrial carbon (C) cycle. We examined the effect of LUCC on topsoil C, microbial biomass C (MBC) and microbes mediated processes related to C circulation and their relationship with other soil properties in low-latitude mountain temperate forests. We selected three sites in the northwest of Cofre de Perote volcano (Mexico) in an altitudinal gradient (piedmont, lower mountain slope and mid slope). At each site we selected three land use/cover units as a chronosequence: (1) reference forest, (2) agriculture, and (3) regeneration/reforestation. At each of the nine land use/cover units we collected five soil samples (0–10 cm) for determination of total soil C (CT), MBC, basal soil respiration, metabolic quotient and enzymatic activity (β-glucosidase and dehydrogenase activities, and fluorescein diacetate hydrolysis). Forest conversion to agriculture diminished the CT concentration in the three sites (72%, 20% and 61% on piedmont and lower and mid slopes, respectively); however, CT content only decreased at piedmont soils. The vulnerability of piedmont soils to C loss due to this LUCC is higher than in mountain slope Andosols. Furthermore, this LUCC differentially affected absolute MBC (i.e. on dry soil base) and specific MBC (i.e. on CT base). Specific site environmental conditions and MBC reference levels seem to determine the sensitivity of MBC to LUCC. Forest recovery after agricultural use only caused an increase of CT concentration (55%) in piedmont soils. There are different controls of soil C storage and circulation in the altitudinal gradient studied. At piedmont and mid mountain slope soils MBC, its activity, nutrient availability and physical soil properties play an important role; meanwhile, at lower mountain slope Andosols mineralogical properties, specifically the Al–humus complexes exerts the main control.

► Forest conversion to agriculture diminishes 20–72% total soil C concentration.
► The sensitivity of microbial biomass C (MBC) to LUCC depends on MBC initial levels.
► Forest recovery increases total soil C concentration only in piedmont Cambisols.
► Controls of soil C storage and dynamics vary along the altitudinal gradient.