Microbial control of soil carbon accumulation in turfgrass systems

Abstract

Turfgrass is a major component of urban and suburban landscapes. It appears that large amounts of carbon (C) can be sequestered in turfgrass systems, making them, potentially, important contributors to CO 2 mitigation efforts. The chronosequences in the present study and those published by others indicate that soil organic matter (SOM) accumulation beneath turfgrasses isnon-linear, progressively moving towards stability over time, which is a pattern typical of restored ecological systems. With this hyperbolic accumulation, SOM and C accumulation rates steadily decline as turfgrass systems age, and rates approach minima after 25–40 years. Because turfgrass growth and generation of C generally do not decline over time, decreasing accumulation rates must result from increased SOM degradation by soil microbes. The size of soil microbial population and its activity increase with the accumulation of SOM; the highest activity being near the soil surface. Examinations of microbial diversity using fatty acid methyl ester and community-level physiological profi ling have shown that a diverse community is present soon after turfgrass systems are established and the community is sustained, with little change, for periods of up to 100 years. Little impact from continual use of fertilizers and pesticides can be detected. Soil enzymes are abundant in turfgrass systems. Hydrolytic and oxidative enzyme activities contribute to the microbial degradation process.