氮负荷增强对闽江口短叶茳芏湿地植物-土壤系统氮累积与分配的影响OA北大核心CHSSCDCSTPCD

The typical Cyperus malaccensis marsh in the Minjiang estuary was selected as the study object.The effects of enhanced nitrogen(N)load on accumulation and allocation of N in plant-soil system were determined by field N load experiment which included four N load levels(NNT,no N treatment,0 g N m-2 a-1;LNT,low N treatment,12.5 g N m-2 a-1;MNT,medium N treatment,25 g N m-2 a-1;and HNT,high N treatment,75 g N m-2 a-1).Results showed that the contents of total nitrogen(TN),NH+4-N and NO-3-N in soils of different N load levels were greatly altered.Compared with the NNT,the contents of TN,NH+4-N and NO-3-N in the LNT and MNT significantly increased and the increase magnitudes were 9.44%,3.57%,11.99%(LNT)and 6.71%,9.37%,46.50%(MNT),respectively.The TN contents in the HNT increased slightly,while the NH+4-N and NO-3-N contents declined greatly and the decrease magnitudes were 9.26%and 40.77%,respectively.The vertical distributions of N contents in soils of different N load levels were also greatly changed.Except for the HNT,the highest contents of TN,NH+4-N and NO-3-N in the LNT and MNT were observed in topsoil.The distributions of TN and NH+4-N contents in the profiles were mainly affected by soil organic matter(SOM),while that of NO-3-N contents was primarily influenced by plant absorption and its vertical leaching.The TN contents in organs of plants generally showed leaf＞stem＞root.Stocks of N in plant-soil systems of different N load levels were much higher in the LNT and MNT,while the lowest value was observed in the HNT.The study found that the C.malaccensis in the LNT and MNT might preferentially allocate more N nutrient to the roots and adapt the N enriched environment by expanding belowground space and elevating belowground biomass,while those in the HNT might adapt the high N load environment through enhancing"self-thinning effect"and expanding aboveground space.