Perennial Trees Associating with Nitrogen-Fixing Symbionts Differ in Leaf After-Life Nitrogen and Carbon Release

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.

Adaptive Management Lessons for Serianthes nelsonii Conservation

“…Nutrient availability beneath the S. nelsonii tree was characterized through the analysis of leaf litter decomposition rates. Rapid litter decomposition was predicted for S. nelsonii leaf litter because of low lignin concentrations of only 148 mg•g −1 (dry weight) and a carbon/nitrogen quotient of only 23 [5]. These predictions were verified during the use of litterbag techniques to reveal a loss of about 80% of the initial litter carbon and nitrogen after only three months of incubation.…”

“…The influence of Fabaceae trees on localized soil nutrients increases neighborhood biodiversity [42]. These results [5,41] illuminated how S. nelsonii trees increase ecosystem health by adding newly fixed nitrogen for the soil food web and providing spatial heterogeneity of the soil chemical and biological traits.…”

“…The green to white calyx and corolla are not showy, but the numerous stamens are striking with red to maroon filaments capped by yellow anthers [1,4]. As a legume tree that associates with nitrogenfixing endosymbionts [5], its presence infuses the biosphere's nitrogen into the terrestrial food web.…”

Nitrogen and Carbon Mineralization from Green and Senesced Leaf Litter Differ between Cycad and Angiosperm Trees

“…For chemical analyses, the soils were thawed to ambient temperature, then N and C components of the soil samples were determined as previously described [ 16 ]. Total N and total C were determined by dry combustion [ 17 ], and organic C was determined by dichromate consumption using the modified Walkley–Black protocol [ 18 ].…”

Aulacaspis yasumatsui Delivers a Blow to International Cycad Horticulture

“…Cycas micronesica associates with nitrogen-fixing endosymbionts and improves ecosystem health by introducing nitrogen into the soil food web and increasing heterogeneity in biogeochemistry [81]. One of the unique traits of the tree is slow leaf-litter decomposition compared to other sympatric tree species [82]. However, the litter quality of C. micronesica leaves was altered by A. yasumatsui herbivory such that nitrogen and potassium concentrations increased, changes that predicted an increase in the decomposition speed of the C. micronesica leaf litter [83].…”