Small‐scale Farming and Grazing Reduce Regeneration of Polylepis tomentella (Rosaceae) in the Semiarid Andes of Bolivia

Abstract

In the Andean highlands, Polylepis woodlands are a rare and unique ecosystem of the treeline. Although human activities have caused the loss of extensive forested areas and decreased woodland regeneration, few systematic and quantitative assessments have been carried out in Polylepis forests. This study compares differences in habitat characteristics, population structure, and reproductive output in populations of Polylepis tomentella subject to different levels of human disturbance in the south-central Andes of Bolivia. We selected P. tomentella because the species still covers large extensions in the form of fragmented forest patches. Results show that human activities affected all the studied populations. Moderately disturbed populations exhibited a lower percentage of farmed area (0.6%) and browsed plants (4%) than strongly disturbed populations (5% and 12%, respectively). All populations exhibited similar proportion of plants with logging scars. Potassium content and canopy closure were 1.5 and 2.5 higher, respectively, in strongly disturbed populations. The density of saplings and seedlings were 75 percent and 80 percent lower in strongly disturbed populations than in moderately disturbed population, even though reproductive individuals produced twice more flowers and fruits. Our results suggest that fruit production does not limit regeneration of P. tomentella and post-dispersal mechanisms may decrease seed germination and increase seedling mortality. Overall, strongly disturbed populations will be less likely to regenerate, leading to population decline. Conservation programs should facilitate forest recovery by promoting seedling establishment, reducing overharvesting and over-browsing, and protecting remaining adult plants.Abstract in Spanish is available in the online version of this article.

Evaluating the fitness effects of seed size and maternal tree size onPolylepis tomentella(Rosaceae) seed germination and seedling performance

“…Studied P. tomentella woodlands were found on rocky hills with relatively steep slopes, at a similar elevational range (3100-3400 m asl). Local people actively use forest stands for collecting firewood, small-scale farming and grazing areas for domestic livestock (sheep, goats and cattle) (Domic et al 2014).…”

“…In this study, we conducted greenhouse experiments to evaluate the functional influence of seed size on germination and offspring performance in the wind-dispersed highland tropical tree Polylepis tomentella Weddell (Rosaceae). We selected P. tomentella because this species is adapted to semiarid high-altitude conditions and is known to experience low rates of seedling recruitment, partially associated with low production of viable seeds (Arrazóla et al 2012, Domic et al 2014, 2017. It is unclear how these effects are a consequence of evolutionary tradeoffs related to high-elevation adaptation or to increasing population decline (Cierjacks et al 2007, Renison et al 2004Velez et al 1998).…”

Influencia del micrositio y el ambiente en la instalación de Polylepis tarapacana en los Altos Andes

“…Sin embargo, en el presente trabajo los renovales fueron encontrados casi exclusivamente en Borde de roca (BR) y Suelo bajo protección de roca (SBR), coincidiendo con los resultados obtenidos por Saavedra [59] en donde el 75% de la regeneración se encuentra protegida por piedras, lo que indica que es probable que la germinación no sea un factor limitante y que las condiciones para la supervivencia y el crecimiento de las plantas sean restrictivas [11,69]. En poblaciones de P. tomentella, el reclutamiento de plántulas constituye un cuello de botella en la regeneración de poblaciones fuertemente perturbadas [70]. En estas poblaciones, las plantas reproductivas pueden producir grandes cantidades de frutos, pero un mayor rendimiento reproductivo no se traduce en mayores tasas de reclutamiento de plántulas.…”

Phylogenetic placement of Leptosphaeria polylepidis, a pathogen of Andean endemic Polylepis tarapacana, and its newly discovered mycoparasite Sajamaea mycophila gen. et sp. nov.

“…Polylepis woodlands are characterized by being dominated either mostly or exclusively by representatives of this genus and by being found in areas of difficult access, including rocky outcrops and mountain slopes (Fjeldså and Kessler 1996;Kessler 2006). These woodlands are important habitats for plant and animal species, including several endangered habitat-specialist bird species (Fjeldså and Kessler 1996) and constitute important sources of firewood, fodder, and medicinal plants for local indigenous communities (Fjeldså and Kessler 1996;Domic et al 2014;Hurtado et al 2018).…”