Combined effects of altitude, fire and biotic interactions on the regeneration of subtropical mountain forest species in Central Argentina
Final Report Abstract
Our project investigated how environmental stress and disturbance affect post-fire regeneration of mountain tree and scrub species. We specifically focused on native woody species in subtropical Central Argentina (e.g., Polylepis australis) across elevational gradients, and how their responses to environmental stress and disturbance are mediated by biotic interactions and local adaptation. Since regeneration of Polylepis australis forests needs sucessful seedling establishment in the first place, it was particularly important to understand which factors may hamper regeneration success of this early life stage. We used an exceptionally massive in situ sowing approach for a field experiment that comprehensively integrated several spatial scales and analysed multiple early life components of our study species. We quantified how early-life performance of endangered mountain trees reacts to co-occurring natural and anthropogenic stress. Key results of this field experiment indicated that microsite effects play a fundamental role for tree establishment but are modulated by complex interactions with elevation (and associated climatic conditions) and livestock. In addition, we found apparent seed-seedling conflicts with a view on the net-outcome of competitive vs. facilitative interactions complicating regeneration niche assessment. We particularly focused on variation in seed-seedling stress resistance among various Polylepis australis populations which provided first empirical support for phenotypic differentiation of stress responses between populations of different elevational origins. This contributed to our understanding of the critical role of local adaptation as a mechanism for coping with natural and anthropogenic stress. We also conducted a systematic review of articles studying post-fire regeneration of subtropical woody plant species. This review confirmed that the dynamics of fire and grazing are widely underrepresented in the available literature. In addition, a reciprocal translocation experiment with seeds and saplings from various provenances across a broad elevational gradient contributed to the understanding of local adaptation. We also performed greenhouse experiments that simulated contrasting environmental stress conditions on performance of Maytenus boaria populations and germination experiments that evaluated variation in the optimum germination temperatures among Vachellia caven. Our findings have practical outcomes in terms of restoration projects as all these species are the most common in the mountains of central Argentina. Moreover, our work adds to the scarce information on inter- and intraspecific variation in key functional traits for mountain forest trees, particularly with a view on early-life stages. We emphasize that this remains a compelling research gap for future studies impairing our understanding on plant functioning in mountain ecosystems and their responses under climate change. Our multi-tiered approaches yielded novel insights on challenges when studying diverse seed and seedling traits for predictive and applied ecology in mountain forests. We emphasize the need to understand the link between vulnerability and among-population variation in seed-seedling key traits across climate gradients, considering climate sensitivity and adaptive capacity at the population level.
Publications
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2017. Influence of altitude on local adaptation in upland tree species from central Argentina. Plant Biology 19, 123-131
Marcora, P. I., Tecco, P. A., Zeballos, S. R., Hensen, I.
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2018. Ecología y conservación de los bosques y arbustales de Polylepis: ¿Qué sabemos y qué ignoramos? Ecología Austral 28:163-174
Renison, D., Morales, L., Cuyckens, E, Sevillano, C.S., Cabrera Amaya, D.M.
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2018. Efecto del fuego y la ganadería en bosques de Polylepis australis (Rosaceae) a lo largo de un gradiente altitudinal en las montañas del centro de la Argentina. Bosque 39: 145-150
Argibay, D.S., Renison, D.
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2019. Effects of altitude, land use and microsites on early life performance of a high mountain tree: Insights from an in situ sowing experiment. Diversity and Distributions 25: 1537-1550
Cáceres, Y., Schrieber, K., Lachmuth, S., Auge, H., Argibay, D., Renison, D., Hensen, I.
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2019. Progeny performance and pathogen attack relative to elevation in a Neotropical tree. CERNE 25: 1-7
Renison, D., Bergero, H., Soteras, F., Herrero, M.L., Rodríguez, J.M., Torres, R.C., Cingolani, A.M., Hensen I.
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2020. Elevational differentiation in metabolic cold stress responses of an endemic mountain tree. Environmental and Experimental Botany 171: 103918
Schrieber, K., Cáceres, Y., Engelmann, A., Marcora, P., Renison, D., Hensen, I., Müller, C.
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2020. Wind protection rather than soil water availability contributes to the restriction of high-mountain forest to ravines. New Forests 51: 101-117
Sparacino, J., Renison, D., Devegili, A., Suarez, R.
