Soil N fluxes in three contrasting dry tropical forests.
A comparative study of N fluxes in soil among a dry dipterocarp forest (DDF), a dry evergreen forest (DEF), and a hill evergreen forest (HEF) in Thailand was done. N fluxes in soil were estimated using an ion exchange resin core method and a buried bag method. Soil C and N pools were 38 C Mg/ha/30 cm and 2.5 N Mg/ha/30 cm in DDF, 82 C Mg/ha/30 cm and 6.2 N Mg/ha/30 cm in DEF, and 167 C Mg/ha/30 cm and 9.3 N Mg/ha/30 cm in HEF. Low C concentration in the DDF and DEF sites was compensated by high fine soil content. In the highly weathered tropical soil, fine soil content seemed to be important for C accumulation. Temporal and vertical fluctuations of N fluxes were different among the sites. The highest N flux was exhibited at the onset of the wet season in DDF, whereas inorganic N production and estimated uptake of N were relatively stable during the wet season in DEF and HEF. It is suggested that N cycling in soil becomes stable in dry tropical forests to intermediate in temperate forests. N deposition may result in large changes of N cycling in the DDF and DEF due to low accumulations of C and N.
Tokuchi
N
N
Laboratory of Silvicullture, Graduate School of Agriculture, Kyoto University, Japan. tokuchi@kais.kyoto-u.ac.jp
Nakanishi
A
A
Wachirinrat
C
C
Takeda
H
H
D002244:Carbon / Q000032:analysis / Q000378:metabolism; D004190:Disasters; D007475:Ion Exchange Resins; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism*; D012621:Seasons; D012987:Soil / Q000032:analysis*; D013785:Thailand; D014197:Trees / Q000502:physiology*; D014329:Tropical Climate
D007475:Ion Exchange Resins; D012987:Soil; D002244:Carbon; D009584:Nitrogen