Effects of Nitrogen and Phosphorus Addition on Soil Water-Stable Aggregates and Organic Carbon Distribution in Moso Bamboo Forests in Subtropical China
[Objective]This study aims to investigate the effects of nitrogen(N)and phosphorus(P)addition on soil water-stable aggregates and soil organic carbon(SOC)distribution in moso bamboo forest in subtropical China,and reveal the response of soil SOC in bamboo forest to N and P addition,providing data support for carbon sequestration and sink enhancement in bamboo forest under N deposition background.[Method]In this study,NH4NO3 was used as N source,NaH2PO4 was used as P source and 4 treatments(CK:0 kg·hm-2a-1N+0 kg·hm-2a-1P,N:120 kg·hm-2a-1N,P:120 kg·hm-2a-1P,NP:120 kg·hm-2a-1N+120 kg·hm-2a-1P)were set.After N and P addition for 3 years,changes of different particle size(>2,0.25-2,0.053-0.25,and<0.053 mm)composition,mean weight diameter(MWD),geometric mean diameter(GMD)and SOC content were investigated.[Result]1)The content of water-stable aggregates in each soil layer was mainly macro-aggregates(>0.25 mm),and the content of macro-aggregates decreased with the increase of soil depth,while the content of micro-aggregates(<0.25 mm)increased with the increase of soil depth.In 0-20 cm soil layer,N treatment significantly increased the content of micro-aggregates,but had no significant effect on the content of macro-aggregates;P treatment had no significant effect on aggregate composition;NP treatment significantly increased the content of micro-aggregates and decreased the content of macro-aggregates;each treatment has no significant effect on MWD and GMD of water-stable aggregates.In 20-40 and 40-60 cm soil layer,the content of macro-aggregate decreased and the content of micro-aggregate increased in each treatment.In 20-40 cm soil layer,P treatment significantly reduced the MWD and GMD of water-stable aggregates,N treatment had no significant effect on MWD and GMD of water-stable aggregates,NP treatment significantly reduced the MWD of water-stable aggregates,and had no significant effect on GMD of water-stable aggregates.In 40-60 cm soil layer,each treatment significantly reduced the MWD and GMD of water-stable aggregates.2)Compared with CK,N,and P treatment significantly reduced SOC content in each soil layer;NP treatment significantly reduced SOC content in 40-60 cm soil layer,but had no significant effect on SOC content in 0-20 and 20-40 cm soil layer.3)N treatment only increased the SOC contribution rate of soil macro-aggregates in 20-40 cm soil layer,decreased the SOC contribution rate of soil micro-aggregates,but had no significant effect on the SOC contribution rate of soil aggregates in 0-20 and 40-60 cm soil layer;NP treatment significantly reduced the SOC contribution rate of macro-aggregates and increased the SOC contribution rate of micro-aggregates in each soil layer;the effect of P treatment on SOC contribution rate of aggregates in 20-40 and 40-60 cm soil layers was consistent with that of NP treatment,but there was no significant effect on 0-20 cm soil layer.[Conclusion]NP addition could mitigate the decrease of SOC content caused by N and P addition to a certain extent.P addition could promote the transfer of SOC from macro-aggregates to micro-aggregates and increase the stability of soil carbon.Therefore,in subtropical forest soils where N is relatively rich and P is limited,P addition can alleviate the decrease of SOC content caused by N deposition and promote the sequestration of SOC to a certain extent.
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