Winter Soil Respiration of 5 Forest Types in the Karst Areas of Central Guizhou Province

LI-6400 portable photosynthesis measurement system and its soil respiration fitting 6400-09 are employed to measure and analyze the soil respiration rate of the Cupressus funebris forests,shrubs,mixed broadleaf,mixed conifer and broadleaf,and Pinus massoniana forests in the karst areas of central Guizhou in winter.Results indicate that there are differences in the diurnal change range among the different forest types and different months.The diurnal change range of shrubs in February is the highest,from1.65 to 2.37 μmol/(m2·s),and that of the Cupressus funebris forests in December is the lowest,from 0.41 to 0.53 μmol/(m2·s).The maximum soil respiration rate is 1.2 to 1.5 times as much as the minimum respiration rate of most of the forest types in different months.The general features of soil respiration of the 5 forest types are that the soil respiration rate of the 5 forest types is the smallest in January,the middle in December,and the biggest in February;the maximum soil respiration rate is 1.46 to 2.85 times as much as the minimum respiration rate;and there is a great difference in soil respiration rate among different months of the same forest type and among different forest types in the same month.There are significant positive exponential correlations between soil respiration rate and the soil temperature at the 5,10,and 15 cm depths.Relations between soil respiration rate and soil volumetric moisture at different soil depths for all the forest types are considerably complex.The contribution percentages of litter to the total soil respiration rate are from 6% to 36%,with that of January being the smallest,February,the middle,and December,the biggest.