Determining Abiotic and Biotic Factors that Limit Transplanted Nothofagus pumilio Seedling Success in Abandoned Beaver Meadows in Tierra del Fuego

Abstract

As ecosystem engineers, North American beavers (Castor canadensis) change many environmental conditions in watersheds, felling trees, damming streams, and flooding riparian zones. In Tierra del Fuego, where beavers were introduced in 1946, these alterations have produced meadows that appear to be long-term alternate stable states, lacking signs of resilience and natural forest regeneration. The aim of this work was to determine the abiotic and biotic factors that affect native tree seedling success in abandoned beaver meadows in Nothofagus pumilio forests. Environmental conditions including light, soil moisture, herbaceous plant community composition, and reinvasion potential were measured in areas impacted by beavers and in unimpacted old-growth forests. Additionally, we monitored the survival and success of N. pumilio seedlings transplanted in plots where meadow vegetation was cleared. Tree seedlings showed little growth, and survival varied by type of beaver impact. While survival was high and similar to unimpacted sites in zones cut but not flooded by beavers, it was significantly lower in meadow zones that were previously flooded and cut, compared to old-growth forests. We found that the reinvasion of herbaceous plants into transplantation study plots was negatively related to tree seedling survival, and herbaceous (monocot) plant cover itself was related to beaver-created gradients in soil moisture and light availability. Overall, these abiotic changes modified the meadow's plant community and enhanced herbaceous vegetation cover, particularly monocots and exotics, thus hindering transplanted seedling survival.

Influencia del micrositio y la exposición en la regeneración de bosques de Nothofagus pumilio afectados por Castor canadensis en Tierra del Fuego: un análisis exploratorio

“…Esta modificación en estructura puede provocar, además, un aumento en la radiación solar, la temperatura del suelo y la velocidad del viento respecto al bosque original (Promis et al 2010). También influye sobre la acumulación de sedimentos en áreas inundadas, retención de nutrientes y profundidad de la napa freática (Henn et al 2014), el cambio de la composición de especies (e.g. rápida colonización de especies intolerantes formando una pradera luego del drenaje) y la dinámica de la regeneración (Martínez Pastur et al 2006, Henn et al 2014.…”

Long-term socio-ecological research in Southern Patagonia: Interdisciplinary strategies to achieve natural resource conservation by sustainable management under scenarios of global change

“…Martínez Pastur et al 2013); (iv) las especies invasoras y la restauración (e.g. Anderson et al 2011;Henn et al 2014); (v) los impactos del manejo (e.g. Peri et al 2013a;Soler et al 2015); y (vi) nuevas estrategias de manejo (e.g.…”

“…Por un lado, llama a restaurar los bosques a su estado natural, pero los estudios han dejado en evidencia que la recuperación de los ecosistemas alterados no ocurre naturalmente en el mediano plazo y es necesaria una intervención que facilite la regeneración del bosque nativo (Martínez Pastur et al 2006;Wallem et al 2010). Por este motivo, actualmente se inició una nueva serie de estudios y monitoreo de varios años sobre la restauración activa en castoreras abandonadas, a partir de trasplantes de ejemplares jóvenes de Nothofagus pumilio (lenga) y N. antarctica (ñire) desde el bosque no impactado (Henn et al 2014). También, debido a este proceso, llegó a ser evidente para los investigadores forestales y biológicos que la factibilidad técnica de erradicar el castor y restaurar los ecosistemas tiene que considerar a la dimensión humana.…”

“…Tres Marías, Cancha Carrera, Nibepo Aike); (vi) estudios ecofisiológicos; y (vii) producción de hojarasca, ciclos de nutrientes y cambios en las propiedades del suelo (e.g. Martínez Pastur et al 2001;2007;2010;Peri et al 2002;Simanonok et al 2011;Henn et al 2014;Lencinas et al 2014;Bahamonde et al 2012;.…”

Suitable conditions for natural regeneration in variable retention harvesting of southern Patagonian Nothofagus pumilio forests

“…The canopy opening determines a significant increase of the effective rainfall that reaches to the soil, increasing the moisture levels that can limit the seedling performance (Promis et al 2010;Martínez Pastur et al 2011b;Dreiss and Volin 2013). Both factors (moisture and light availability) can explain most of the establishment, growth, and eco-physiological performance of the seedlings (Rey et al 2004;Lencinas et al 2007;Martínez Pastur et al 2007aPeri et al 2009;Soler et al 2011;Henn et al 2014). However, negative synergies have been observed in some microenvironments, where large canopy openings can produce drying effects, acting as a limiting factor for regeneration (McIntire et al 2016;Toro Manríquez et al 2018), as well as higher radiation levels that can increase the evaporation rates (Martínez Pastur et al 2011a, 2011b.…”