Soil respiration patterns and controls in limestone cedar glades

Abstract

Aims: Drivers of soil respiration (Rs) in rock outcrop ecosystems remain poorly understood. We investigated these drivers in limestone cedar glades, known for their concentrations of endemic plant species and for seasonal hydrologic extremes (xeric and saturated conditions), and compared our findings to those in temperate grasslands and semi-arid ecosystems. Methods: We measured Rs, soil temperature (Ts), volumetric soil water content (SWC), soil organic matter (SOM), soil depth, and vegetation cover monthly over 16 mo and analyzed effects of these variables on Rs. Results: Seasonally, Rs primarily tracked Ts (r2 = 0.77; P < 0.01), however Rs was depressed during a summer drought. SOM was highly variable spatially, and incorporating SOM effects into the Rs model dramatically improved model performance. Both shallow soil and sparse vegetation cover were also associated with lower Rs. Conclusions: Soil depth, SOM, and vegetation cover were important drivers of Rs in limestone cedar glades. Seasonal Rs patterns reflected those for mesic temperate grasslands more than for semi-arid ecosystems, in that Rs primarily tracked temperature for most of the year.