Effects of historical browsing by introduced ungulates on litter decomposition via changes in leaf traits and soil properties

TAPELLA, M. PAZ; BARRIOS-GARCIA, M. NOELIA; RODRIGUEZ-CABAL, MARIANO A.; SASAL, YAMILA; QUINTERO, CAROLINA

Buenos Aires

Congreso; VII Congress of the Latin American Association of Chemical Ecology; 2023

ALAEQ

Ungulates are important agents of natural selection in different ecosystems. As herbivory can alter the chemistry and structure of remaining plant tissues, subsequent effects on litter decomposition are expected. Yet, previous studies have shown results in both directions, either accelerating or decelerating decomposition, and not many have assessed the mechanisms behind. Our aim was to explore the effect of historical browsing by introduced ungulates on litter decomposition and its potential mechanisms, using an abundant palatable native plant from Patagonian temperate forests, Aristotelia chilensis (Elaeocarpaceae). We selected sites with ungulates present and absent and performed a reciprocal incubation experiment using the litterbag method, allowing us to assess the effects of ungulates via changes in litter quality and in soil properties separately. We quantified soil variables (moisture, temperature, respiration), carbon and nitrogen content from leaf litter, and phenols, flavonoids, carbon, and nitrogen content from green leaves. We evaluated litter quality and soil variables in response to presence/absence of ungulates, and the percentage of mass remaining in response to litter origin and incubation site, both factors with two levels (ungulates present/absent).We did not find any significant effect of ungulates on decomposition nor in the litter quality and soil variables considered. However, we found a trend of higher mass remaining on litterbags decomposing on sites with ungulates. Mechanistically, we also found a trend of higher C:N ratio, phenols, and flavonoids content in plant material from sites without ungulates as well as a higher soil respiration from sites without ungulates. These results suggest that ungulates are potentially decelerating soil processes. Altogether, this implies that plants exposed to ungulates might be allocating more resources to grow (tolerate) or other defensive traits (i.e., alkaloids or leaf toughness) than to carbon-based compounds (phenols and flavonoids); which are now in the process of being evaluated.