Human disturbance affects enzyme activity, microbial biomass and organic carbon in tropical dry sub-humid pasture and forest soils

ABSTRACT

The Brazilian dry forest occupies an area of about 1 million km² approximately 46% of which has been deforested. Many studies have been done on the effects of this on productivity and soil chemical attributes. However, little is known about soil enzymatic activity, which is sensitive to environmental changes. The objective of this study was to evaluate the effects of deforestation using different levels of human disturbance on soil enzyme activities, organic carbon content, microbial biomass, and microbial community. We studied areas covered with forest (TDF), old grass (OG), or new grass (NG). Soils from NG had increased microorganisms, which restored important processes related to carbon, sulfur, and nitrogen cycling, so that they resembled those in the forested area. The results of this study showed that the conversion of forest to pasture with a high level of human disturbance could decrease the activities of β-glucosidase, urease, alkaline phosphatase, and fluorescein diacetate in the soil by up to 87%, 66%, 62%, and 58%, respectively. These findings suggest that human disturbance can cause substantial changes in the enzymatic activity and microbial community in the soil. We suggest that maintaining grass pasture with low human disturbance should have fewer impacts on soil quality.

KEYWORDS:

• Microbial activity
• carbon cycling
• low-disturbance pasture
• microbial diversity
• fatty acids profiles

Highlights

• Forest conversion to levels of human disturbance pasture decreased soil enzyme activities.

• The soil horizon influenced more enzymes and C sequestration than the human disturbance level.

• Grass cultivated with low disturbance increased the number of metabolically active microorganisms of the soil.

• Gram-positive bacteria and acid phosphatase highlighted the role of this microbial group in the surface of pasture soils.

Acknowledgments

This work was supported by the CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico under Grant number 306401/2015-0; 313174/2018-0; 426497/2018-0; 465764/2014-2; 307335/2017-8; 441305/2017-2; 441305/2017-2); CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil under Finance Code 001); FACEPE (Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco under Grant number APQ-0223-5.01/15; APQ-0419-5.01/15, APQ-0498-3.07/17) and National Observatory of Water and Carbon Dynamics in the Caatinga Biome (NOWCDCB) network, as well as the owner of “Riacho do Papagaio” Farm for allowing us to conduct the research in his property.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Department of Social Sciences, Oxford Brookes University.