Responses of soil phosphorus fractions after nitrogen addition in a subtropical forest ecosystem: Insights from decreased Fe and Al oxides and increased plant roots

• Published in: Geoderma Vol. 337; pp. 246 - 255
• Main Authors: Fan, Yuexin, Zhong, Xiaojian, Lin, Fang, Liu, Chenchung, Yang, Liuming, Wang, Minhuang, Chen, Guangshui, Chen, Yuehmin, Yang, Yusheng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2019
• Subjects: aluminum; aluminum oxide; biomass; Castanopsis; Cation exchangeable capacity; China; environmental factors; forest ecosystems; Hedley P; iron; iron oxides; nitrogen; phosphorus; Root biomass; Root length density; roots; soil properties; tropical forests; China; pH; Root biomass; Hedley P; Cation exchangeable capacity; Root length density
• ISSN: 0016-7061
• DOI: 10.1016/j.geoderma.2018.09.028

Elevated nitrogen (N) deposition may exacerbate soil phosphorus (P) limitations in P-deficient subtropical forest ecosystems. However, which abiotic factors predominantly contribute to soil P transformations and how plant roots affect soil P variations after N addition in these ecosystems are unclear. To address these issues, we studied a natural Castanopsis carlesii forest in Fujian, China subjected to 3 years of N addition. Soil P fractions, soil properties, iron (Fe) and aluminum (Al) oxides, root biomass (RB), and root length density (RLD) were investigated. The results showed that N application remarkably increased the concentrations of soil available P but significantly decreased content of soil moderately labile P. The quantities of free Fe and Al (Fed and Ald) and organic-bound Fe and Al (Fep and Alp) decreased after N addition. These changes indicated an important relationship between Fe and Al oxides and P fractions, especially Fep and moderately labile P, suggesting that Fe and Al oxides predominantly influenced soil P fractions in N-enriched plots. Meanwhile, RB and RLD were higher after N addition treatments than control treatment. Positive correlations between RB and RLD and P fractions (available P, labile P, and moderately labile P) indicated that plant roots exert an essential influence on changes in soil P fractions. In conclusion, N addition in subtropical forests significantly influenced soil P fractions, primarily by decreasing Fe and Al oxides and increasing plant root biomass and density. •Simulated N deposition significantly decreased soil moderately labile P and increased available P in forest soil.•N deposition induced a decline of free Fe and Al (Fed and Ald) and organic-bound Fe and Al (Fep and Alp) in forest soil.•Plant root biomass and root length density were increased by nitrogen treatments.