Interspecific differences in seedling growth of three main afforestation tree species in response to simulated N deposition
The enhanced atmospheric N deposition in recent years has brought the increases in N availability and N/P ratio in forest soils,which would impact the growth and productivity of plants.Pinus massoniana,Cunninghamia lanceolata and Schima superba are the main afforestation tree species with different growth and biological characteristics in southern China.Taking seedlings of the three tree species as test materials,a pot experiment was conducted to simulate low P soil conditions in combination with two N deposition levels,to study interspecific differences in growth and adaptation mechanism to low P stress under N addition.The results showed that:1) The aboveground part growth of P.massoniana and S.superba was promoted by simulated N deposition,but their root growth and root biomass accumulation were inhibited.The whole plant biomass of P.massoniana and S.superba were not significantly changed under simulated N deposition.The aboveground part and root growth of C.lanceolata were severely inhibited by simulated N deposition,so its whole plant biomass was significantly decreased;2) The degree of low P stress of the three tree species seedlings was increased by simulated N deposition,which led to the increase of root secreted APase activity and organic acids.The increased degrees of total amount of root secretion of P.massoniana and S.superba were greater than that of C.lanceolata;3) Simulated N deposition increased leaf N contents of the three tree species,but decreased their leaf P contents,thus increased their leaf N/P ratios.The increased degree of leaf N/P of C.lanceolata was the maximum,and that of P.massoniana was the minimum.The rapid increase of leaf N/P ratio of C.lanceolata resulted in the relative scarcity of its leaf P content and imbalance of leaf N and P nutrients,finally influenced C.lanceolata leaf photosynthesis.The increased degree of leaf N/P ratios of P.massoniana and S.superba were relatively small.The increase of leaf N contents of P.massoniana and S.superba promoted their leaf net photosynthetic rates;4) Under simulated N deposition,the acidification of surface soil of P.massoniana and S.superba was greater than that of C.lanceolata,while soil hydrolytic N contents of P.massoniana and C.lanceolata were increased as compared to S.superba due to greater N absorption and N leaching of surface soil of S.superba,and stronger surface soil N leaching of P.massoniana compared to C.lanceolata.In addition,soil available P contents of the three species were all decreased,and they were higher in the topsoil than in the subsoil under simulated N deposition.
Pinus massonianaCunninghamia lanceolataSchima superbalow P stresssimulated N deposition
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维普
