Dominance by Spartina densiflora slows salt marsh litter decomposition

DALEO, PEDRO; MONTEMAYOR, DIANA I; FANJUL, EUGENIA; ALBERTI, JUAN; BRUSCHETTI, MARTIN; MARTINETTO, PAULINA; PASCUAL, JESUS; IRIBARNE, OSCAR

JOURNAL OF VEGETATION SCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2020

1100-9233

 Due to their efficiency sequestering and storing atmospheric CO2, coastal vegetated systems are known to play a fundamental role in climate change mitigation. While most of the work evaluating carbon sequestration capacity has focused on global change factors that can affect carbon release from plant litter decomposition through changes in (large-scale) environmental conditions, less is known about the possible effects of the loss (or replacement) of dominant species. We hypothesized that dominant marsh plants can influence decomposition not only through changes in liter quality but also through changes in (micro-scale) soil environmental conditions such as humidity, soil temperature or solar radiation. ?Location?: We performed a field manipulative experiment in a South Western (SW) Atlantic salt marsh, in Argentina?Methods?: We simulate a selective disturbance (i.e. removal of the dominant grass species Spartina densiflora) thus allowing removal plots to develop an alternative plant community. To evaluate the effect of the dominant grass species on litter decomposition, we performed a litterbag approach experiment three years after the establishment of the removal plots. ?Results?: Results showed that the presence of S. densiflora significantly decreased litter decomposition directly by producing less labile litter, but also by effects that seem to be related to its structure as standing dominant vegetation. The experimental removal of S. densiflora led to an alternative plant community, formed by otherwise subordinate species, which is less densely packed, allowing higher soil radiation incidence and elevated midday soil temperature.?Conclusions?: Our results suggest that salt marsh litter decomposition, and thus C sequestration, is determined in part by the identity of the dominant plant, not only because of the quality of produced litter but also as a consequence of the structure of vegetation. Changes in species diversity, above all the dominant species in these coastal systems, could have large impacts on carbon turnover and mitigation capacity of these ecosystems.