Hot Spots Of Soil Respiration In A Seasonally Dry Tropical Forest In Southern Vietnam: A Brief Study Of Spatial Distribution

Abstract

Many studies report asymmetrical spatial distribution of soil respiration caused by presence of areas with significantly higher emission rates (so-called hot spots). For seasonally dry tropical forest soil respiration was measured on 1 ha plot with 20m, 5m and 1 m scale in the first half of dry season. 457 measurements made in 9 series at 54 sampling points. The results suggest that lognormal spatial distribution model appears to be much more supported rather than the normal one. A statistical method proposed for estimation the mean value and its confidence interval of lognormally distributed data. The mean emission rate E(RS) for the lognormal distribution amounted to 4.28 µmol m-2 s-1, the 95% confidence interval is 3.93 to 4.76 µmol m-2 s-1. However, the standard sample mean can be used as an estimator of the mean of lognormally distributed values of soil respiration if their coefficient of variance remains approximately the same as in our study (CV=0.35). Based on the data obtained and literature sources, recommendations are given on the number of sampling points for estimating the spatial average value with a given accuracy.

Keywords

• soil respiration
• carbon emission
• hot spots
• tropical forest
• spatial variability
• sample size