Abstract
Plants that enter symbiotic relationships with nitrogen (N)-fixing microbes contribute some of their N to the community through leaf litter decomposition and mineralization processes. The speed of these processes varies greatly among tree species. Mesocosm methods were used to determine the speed of N and carbon (C) release from Cycas micronesica, Intsia bijuga, and Serianthes nelsonii leaf litter. Microcosm methods were used to determine soil respiration traits in soils containing the leaf litter. The speed of leaf litter N and C release during decomposition occurred in the order C. micronesica < I. bijuga < S. nelsonii. Soil carbon dioxide efflux was increased by adding leaf litter to incubation soils, and the increase was greatest for S. nelsonii and least for C. micronesica litter. Ammonium, nitrate, total N, organic C, and total C were increased by adding litter to incubation soils, and the differences among the species converged with incubation duration. The rate of increases in available N and decreases in organic C were greatest for S. nelsonii and least for C. micronesica litter. These findings indicate that S. nelsonii litter released N and C rapidly, C. micronesica litter released N and C slowly, and the leaf economic spectrum accurately predicted the differences.
Highlights
Biological nitrogen (N) fixation is a crucial component of the nitrogen cycle [1,2]
These findings indicate that S. nelsonii litter released N and C rapidly, C. micronesica litter released N
Leaf litter was collected in northern Guam from trees that were growing in coastal karst substrates that were formed in slope alluvium, loess, and residuum overlying limestone (Clayey-skeletal, gibbsitic, nonacid, isohyperthermic Lithic Ustorthents) [29]
Summary
Biological nitrogen (N) fixation is a crucial component of the nitrogen cycle [1,2]. The group of plants known as N-fixers is not capable of N fixation directly [3], but they enter symbiotic relationships with N-fixing microbes in a manner that gives them access to the newly fixed N [4,5]. Cyanobacteria have evolved N-fixing capacity [6], and the ancient group of plants known as cycads develops ageotropic coralloid roots which are colonized by cyanobacteria [7,8]. The decomposition of litterfall has been the primary focus for research on how trees transfer minerals and metals from the living tree to the bulk soil. Litter decomposition is a critical component of the global C cycle [12]. C and N dynamics are often studied in synchrony during the mineralization of elements from organic matter
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