The changes of nitrogen(N)content and its storage in soils under diferent land 118e8 in the Sanjiang Plain were analyzed to explore the eharaeteristie of the evolution ofN storage.The results showed that the total nitrogen(TN)content and its storage in wetland soil were hig}l—el"than those in fire wetland and desertion cropland soils.The reclamation depleted soll N content,and the TN content and its storage in soils showed a decreasing trend as the increase of eultivatiOil years,which accorded with first—order exponential deeay model(P<0.O1).The se—quential fire for 5 years induced the TN content and its storage in soils to be decreased significantly。while the desertion under’’Grain for Green” Projeet for 7 years induced the vslue$increased,but the inerease was very limited,which indieated that the soll N pool,orlee depleted,was hard to restore. nle TN content in soil was found to be positively related to organie matter(P<0.O1),suggesting that the decrease of organic matter due to reclamation rnight be the main eallse of the decrease in N fertility of the soils.So that,inereasing soil organie matter is propitious to the maintenance and increase of soil N fertility.The moderate anthropogenie N(such as agricultural drainage)was advised to be imported into the fire wetland。which could restrain the sustaining loss of N in soil and prevent the degradation ofwetland vegetations.In addition.the adverse effeets caused by agriculture drainage that imported into rivers direetly also could be avoided.
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