Effect of N and P addition on soil organic C potential mineralization in forestsoils in South China
OUYANG Xuejun , ZHOU Guoyi , HUANG Zhongliang , ZHOU Cunyu , LI Jiong , SHI Junhui , ZHANG Deqiang
DOI:
Received October 30, 2007,Revised February 18, 2008, Accepted , Available online
Volume 20,2008,Pages 1082-1089
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Atmospheric nitrogen deposition is at a high level in some forests of South China. The e ects of addition of exogenous N and P
on soil organic carbon mineralization were studied to address: (1) if the atmospheric N deposition promotes soil C storage through
decreasing mineralization; (2) if the soil available P is a limitation to organic carbon mineralization. Soils (0–10 cm) was sampled from
monsoon evergreen broad-leaved forest (MEBF), coniferous and broad-leaved mixed forest (CBMF), and Pinus massoniana forest
(PMF) in Dinghushan Biosphere Reserve (located in Guangdong Province, China). The soils were incubated at 25°C for 45 weeks,
with addition of N (NH4NO3 solution) or P (KH2PO4 solution). CO2-C emission and the inorganic N (NH4
+-N and NO3??-N) of the
soils were determined during the incubation. The results showed that CO2-C emission decreased with the N addition. The addition
of P led to a short-term sharp increase in CO2 emission after P application, and the responses of CO2-C evolution to P addition in
the later period of incubation related to forest types. Strong P inhibition to CO2 emission occurred in both PMF and CBMF soils in
the later incubation. The two-pool kinetic model was fitted well to the data for C turnover in this experiment. The model analysis
demonstrated that the addition of N and P changed the distribution of soil organic C between the labile and recalcitrant pool, as well as
their mineralization rates. In our experiment, soil pH can not completely explain the negative e ect of N addition on CO2-C emission.
The changes of soil inorganic N during incubation seemed to support the hypothesis that the polymerization of added nitrogen with soil
organic compound by abiotic reactions during incubation made the added nitrogen retard the soil organic carbon mineralization. We
conclude that atmospheric N deposition contributes to soil C accretion in the three subtropical forest ecosystems, however, the shortage
of soil available P in CBMF and PMF may also retard soil organic C mineralization.
