For determination of mangrove soil C, we collected soil cores
(4 cm in diameter and 100 cmdeep; three per site) with a soil auger
and PVC tubes. It was difficult to draw soil cores out using large
tubes.We tested three sizes of PVC tubes (3, 4, and 6 cm) and found
4 cm was the best one. We separated each 10-cm layer for the top
70 cm (seven layers), while the 70e100 cm depth was sampled as
one layer because of its relatively constant C concentration