Glomalin Production and Microbial Activity in Soils Impacted by Gypsum Mining in a Brazilian Semiarid Area

Abstract

Problem statement: Mining activities involve the removal of the veget al cover and the soil organic layer, causing a severe environmental impac t. In Northeast Brazil, 40% of the world's crude gypsum is found in a semiarid area, making this reg ion responsible for 95% of the gypsum demand in the national market. Although economically important, this activity is harmful to the environment. Studies of soil microbiological and biochemical att ributes can help in the identification of the limitations of impacted ecosystems, providing data to define strategies for sustainability of such environments. Approach: To evaluate and compare the biological state of pr eserved and mining degraded semiarid soils, a native preserved area an d areas impacted by gypsum mining were selected at the Araripina Experimental Station, located in t he semiarid region of Pernambuco State, Northeast Brazil. The four sampling areas included: (1) A nat ive, preserved caatinga area with spine bearing trees and shrubs and some characteristic xerophytic plants (AN); (2) An area surrounding the mine, presenting the same type of vegetation although alr eady degraded (AM); (3) A waste deposit area (AR); (4) Interface area between the waste deposit and a mining degraded area (AI). Samples were taken in each area (1000 m 2 ) during two periods: wet (December/2003, Rainfall = 28.7 mm) and dry (September/2004, Rainfall = 1.3 mm). Results: Fluorescein diacetate hydrolysis values, microbial biomass C and basal respiration were higher in the preserved caatinga than in the impacted areas. The gypsum mining activity reduced the concentration of easily extractable glomalin in relation to the native caatinga area in both sampling periods. Hi gher deposits of total glomalin also occurred in th e native area, however, mainly during the wet period. Conclusion: The mining activity produced a negative impact on the soil microbiota, reducing th e total enzymatic activity. The microbial biomass was significantly lower in the waste deposit area t han in the native and interface areas. The results indicated that the mining activity is harmful to th e soil microbiota in this area and that glomalin ca n be a useful indicator of soil disturbance.