Resumo

PAJARES-MORENO, Silvia; GALLARDO-LANCHO, Juan F.  e  ETCHEVERS-BARRA, Jorge D.. Biochemical indicators in soils from an altitudinal transect at the mexican neovolcanic belt. Agrociencia [online]. 2010, vol.44, n.3, pp.261-274. ISSN 2521-9766.

The biochemical aspects of the tepetates (hardened volcanic layers) and soils coming from volcanic materials have been little studied. The flow of CO₂ (FC) and the biochemical properties of volcanic soils representative of México were evaluated in this work. Five soils were chosen in a transect of the Tláloc volcano with different uses: cuminal grassland (PC), pine-oak (PE), reforested pine (PR), bare tepetate (TD), and halophytic formations of the former Lake of Texcoco (LT), located at 2950, 3010, 2700, 2650, and 2220 m altitude. The soils of the transect correspond to the sequence: Phaeozems (PC), Luvisols (PE and PR), tepetates (TD) and Solonchacks (LT). In each zone soil samples were taken (0-15 cm deep) and FC and soil moisture (HS) were periodically measured in situ from August 2005 to July 2006. The variables determined were: soil organic C (SOC), total N (Nt), microbial biomass C and N, basal respiration (RS), ammonification of arginine, and enzyme activities (dehydrogenase, β-glucosidase, phosphatase, urease and protease). The most degraded areas (TD and LT) recorded lower values in all variables, whereas the best preserved (PE and PC) showed higher values (especially in SOC, Nt, microbial biomass and enzyme activities). The RS and FC were low in TD (8.1 ug C-CO₂ g^-1 d^-1 and 0.05-0.07 g m^-2ha^-1 ), since this is a hardened substrate without a plant cover and low content of SOC and Nt (0.8 mg C g^-1 and 0.13 mg N g^-1). The higher content of SOC in PE and PC (55.2 and 32.7 mg C g^-1) and HS during the rainfall period promote soil microbial activity and thus FC (1.22 and 1.05 g m^-2 ha^-1 in August). The biochemical variables selected, of easy measurement and interpretation, are suitable indicators to assess the quality of Mexican volcanic soils under different environmental conditions.

Palavras-chave : enzymatic activity; microbial biomass; soil organic C; CO₂ flux; volcanic soils; tepetate.

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