Temperature and its variability in oak forests in the southeastern Missouri Ozarks

This paper examines air and soil temperature, their variabilities, and their relationships with decomposition and ground flora diversity within an oak Quercus forest in the southeastern Missouri Ozarks (USA). We conducted 3 experiments with 9 mobile weather stations at Missouri Ozark Forest Ecosystem Project (MOFEP) study sites from September 1994 to August 1995. We used the cotton strip assay technique to quantify decomposition rate and Simpson's diversity index to evaluate the diversity of the ground flora. We found that air temperature at each site differed significantly from every other site (p c 0.001) based on a temporal scale of 20 min; thls was also the case for soil temperature (p < 0.001). The spatial variation of soil temperature was consistently greater than that of air temperature. The spatial variation of air temperature increased with increasing spatial scale. Spatial variation of soil temperature increased rapidly from the 0 to ca 40 m scale, then decreased slowly before it began to increase again at a spatial scale of ca 700 m. Temperature was not highly correlated to decomposition rate in the study area (correlation coefficients were 0.51 and 0.64 for air and soil temperature, respectively). The spatial variation of temperature was inversely related to the species diversity of the ground flora (R2 was 0.87, 0.93, and 0.76 for air, soil surface, and soil temperature, respectively, at the 400 m scale). These results suggest that temperature variation can be quite significant. even at the stand level, and can impact some ecological patterns and processes at the same scale.