Code for: Assessing the role of foliar habit on nutrient losses in a sub-Antarctic forest

Résumé fourni par la source

The input of litter into soil is critical for ecosystem functioning and nutrient cycling. Deciduous species are expected to undergo higher nutrient leaf losses via litter than evergreens. This premise, which explains the common leaf-habit geographic segregation between deciduous broadleaved and evergreen conifer species, has not been evaluated in co-occurring deciduous and evergreen broadleaved tree species. We conducted a high-frequency monitoring study of nutrient losses in congeneric and sympatric broadleaved tree species with contrasting leaf habits. We collected litter periodically for three years from 979 co-occurring trees of the deciduous Nothofagus pumilio and N. antarctica and the evergreen N. dombeyi in a sub-Antarctic forest of southern Chile. We estimated and compared foliar habits’ litterfall biomass (senescent and green leaves and fruits), nutrient return through litterfall’s nitrogen (N) and phosphorus (P) contents, and synchronization between litterfall mass and nutrient concentrations for each species. Annual litter biomass was higher in the two deciduous species (2.01 t ha–1) than in the evergreen species (1.63 t ha–1), with senescent leaves representing >90% of litter in the three species. The fraction of litter represented by green foliage was 1.5 times higher in the evergreen species, reaching up to 12% of all litter in the evergreen versus 7% in the deciduous species, respectively. Litter N and P concentrations were significantly lower in the evergreen species. Thus, deciduous species had significantly higher N (15.82 k ha–1) and P (1.55 k ha–1) annual returns than the evergreen species (N: 8.20 k ha–1, P: 0.83 k ha–1) through litter of senescent leaves. A synchronization between maximum litterfall production and minimum litter concentrations for N but not for P was found in both leaf habits, although more consistently for deciduous than for evergreen. Higher nutrient losses through litter in deciduous than in co-occurring evergreen species suggest that differences in nutrient turnover might not necessarily lead to geographical segregation, as it is implicated in the prevailing theory. This study deepens our understanding of plant nutrient strategies associated with leaf habit and underscores the importance of diverse mechanisms of nutrient loss when evaluating forest nutrient dynamics.

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