资源环境科技发展态势分析平台

There is substantial evidence that legume-derived nitrogen (N) is transferred to neighboring nonlegumes in herbaceous mixtures and intercropping systems. However, considering that woody species are key sources and major consumers N, information regarding whether N transfer from leguminous to nonleguminous woody species in mixed plantations was detected. To detect N transfer in a Eucalyptus urophylla x Eucalyptus (E.) grandis and Dalbergia odorifera mixed system, two pot experiments were set up, one with N-15 dilution and the other with N-15 leaf labeling of Dalbergia odorifera. Seedlings were fertilized with CO ((NH2)-N-15)(2) urea, and the effects on interspecific N transfer and biological N fixation (BNF) efficiency were observed. Results showed that: (1) The values of competition ratio of Eucalyptus urophylla x E. grandis to Dalbergia odorifera (CRED) greater than one indicate that Eucalyptus urophylla x E. grandis was a stronger competitor and had the absolute advantage over Dalbergia odorifera, N application significantly increased the competition ratio of Eucalyptus urophylla x E. grandis to Dalbergia odorifera. An increase in the thy matter yields of Eucalyptus urophylla x E. grandis was observed in the NB treatment (20.36-33.16%), but the dry matter yields of Dalbergia odorifera decreased by 10.02-19.57%. (2) N was transferred from Dalbergia odorifera to Eucalyptus urophylla x E. grandis at rates of 9.60% and 6.50% in the 3 and 6 g pot(-1) urea treatments with isotope dilution markers, respectively. N transfer rates of 13.66% and 7.88% were observed in the NB and MB treatments with N-15 leaf labeling. (3) Interspecific root interaction increased N use efficiency and increased N2 fixation by Dalbergia odorifera; N fixation increased by 8.51% and 4.34% at the N1 and N2 levels under the NB treatment. The biomass and N use efficiency of Eucalyptus urophylla x E. grandis and Dalbergia odorifera has grown together were effectively improved compared to those of monocultures. The mechanism for our results may depend on interspecific N transfer, i.e., N transfer from Dalbergia odorifera to Eucalyptus urophylla x E. grandis, the stimulation of Dalbergia odorifera BNF and its increased use of atmospheric N sources may improve the exploitation of mixed plantations.