Differential responses and mechanistic controls of soil phosphorus transformation in Eucalyptus plantations with N fertilization and introduced N2-fixing tree species

Eucalyptus is one of the most extensively planted commercial plantation timber genera in tropics and subtropics. Introducing N₂-fixing tree species into Eucalyptus plantations has been widely considered as one of optimal silvicultural practices to balance N losses due to timber harvesting and reduce the demand for N fertilizer. However, N enrichment may exacerbate phosphorus (P) limitation as Eucalyptus is extensively planted in P-poor tropical and subtropical soils.

Professor DENG Qi and his colleagues conducted a field experiment in a pure plantation of E. urophylla × E. grandis to investigate the impacts of N fertilization and introduced an N-fixer of Dalbergia odorifera on soil P transformation. Results showed that N fertilization significantly enhanced soil occluded P pool and reduced the other P pools due to acidification-induced pH-sensitive geochemical processes, lowering Eucalyptus leaf P concentration with higher N:P ratio. In contrast, introduced NFTS did not change soil pH, labile inorganic P pool and Eucalyptus leaf N:P ratio, even enhanced organic P pools and reduced occluded P pool probably due to altering microbial community composition particularly stimulating arbuscular mycorrhiza fungal abundance. These results revealed differential responses and mechanistic controls of soil P transformation in Eucalyptus plantations with N fertilization and introduced NFTS. The dissolution of occluded P pool along with organic P accumulation observed in the mixed plantations may represent a promising future to better manage soil P availability.

The paper entitled "Differential responses and mechanistic controls of soil phosphorus transformation in Eucalyptus plantations with N fertilization and introduced N₂-fixing tree species" was recently published in the New Phytologist. Dr. Xianyu Yao is the first author of the paper, and Prof. Qi Deng is the corresponding author. Link to the article: doi: 10.1111/nph.18673).

Fig. A conceptual framework of how N fertilization (a) and D. odorifera (b) help Eucalyptus for increasing demand for phosphorus through microbial PLFA and ACP activity.