Soil Nitrogen in Relation to Quality and Decomposability of Plant Litter in the Patagonian Monte,Argentina |
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Authors: | Email author" target="_blank">Carrera?Analía?LorenaEmail author Vargas?Dariana?Noé Campanella?María?Victoria Bertiller?Mónica?Beatriz Sain?Claudia?Leticia Mazzarino?María?Julia |
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Institution: | (1) CENPAT (Centro Nacional Patagónico (CONICET), Boulevard Brown s/n, 9120 Puerto Madryn, Chubut, Argentina;(2) Centro Regional Universitario Bariloche, Universidad Nacional del Comahue–CONICET, Argentina |
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Abstract: | In two consecutive years, we analysed the effect of litter quality, quantity and decomposability on soil N at three characteristic
sites of the Patagonian Monte. We assessed (i) concentrations of N, C, lignin and total phenolics and the C/N ratio in senesced
leaves as indicators of litter quality of three species of each dominant plant life form (evergreen shrubs and perennial grasses),
and (ii) N, and organic-C concentrations, potential N-mineralisation and microbial-N flush in the soil beneath each species.
Rate constants of potential decomposition of senesced leaves and N content in decaying leaves during the incubation period
were assessed in composite samples of the three sites as indicators of litter decomposability. Further, we estimated for each
species leaf-litter production, leaf-litter on soil, and the mass of standing senesced leaves during the senescence period.
Senesced leaves of evergreen shrubs showed higher decomposability than those of perennial grasses. Leaf-litter production,
leaf-litter on soil, and the mass of standing senesced leaves differed significantly among species. The largest variations
in leaf-litter production and leaf-litter on soil were observed in evergreen shrubs. The mass of standing senesced leaves
was larger in perennial grasses than in evergreen shrubs. Nitrogen, organic C and potential N-mineralisation in soil were
higher underneath evergreen shrubs than beneath perennial grasses, while no significant differences were found in microbial-N
flush among life forms. The initial concentrations of C, N and total phenolics of senesced leaves explained together 78% of
the total variance observed in the dry mass loss of decaying leaves. Litter decomposition rates explained 98%, 98%, 73%, and
67% of the total variance of soil N, organic C, net-N mineralisation, and microbial-N flush, respectively. We concluded that
leaf-litter decomposition rates along with leaf-litter production are meaningful indicators of plant local effects on soil
N dynamics in shrublands of the Patagonian Monte, and probably in other similar ecosystem of the world dominated by slow growing
species that accumulate a wide variety of secondary metabolites including phenolics. Indicators such as C/N or lignin concentration
usually used to predict litter decomposability or local plant effects may not be adequate in the case of slow growing species
that accumulate a wide range of secondary metabolites or have long leaf lifespan and low leaf-litter production. |
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Keywords: | Decomposition rate constants Evergreen shrubs Lignin N mineralisation Perennial grasses Phenolic compounds |
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