A glance on the native colombian magnoliaceae

Se estima que en Colombia existen entre 35.000 y 50.000 especies de plantas, muchas de ellas aún desconocidas para la Ciencia. La transformación acelerada de ecosistemas, el crecimiento de las zonas urbanas, la expansión de la frontera agropecuaria y el uso inadecuado de los recursos naturales, han llevado a un gran número de especies a la extinción, incluso antes de ser descubiertas. Recientemente se hallaron dos nuevas especies de la familia Magnoliaceae, incrementando el número total de especies colombianas a33, todas ellas con algún riesgo de extinción. Este artículo presenta una reflexión sobre la familia Magnoliaceae con relación a su importancia ecológica y medicinal, y la necesidad urgente de tomar medidas para su conservación. Palabras clave: Magnoliaceae, Magnolia, Colombia, especies amenazadas, extinción.An estimation of the number of plant species in Colombia is between 35.000 and 50.000 and many of themare still unknown to Science. The accelerated transformation of ecosystems coupled to the urban expansion, the increase of agricultural and livestock frontiers and the inadequate use of natural resources have led many species to extinction even before been discovered. Recently two new species of the Magnoliaceae family were found, increasing the total number of Colombian species to 33, all of them with some risk of extinction.In this article a reflection about the Magnoliaceae family is presented from the point of their ecologic and medicinal importance and the urgent need to take actions for its conservation. Keywords: Magnoliaceae, Magnolia, Colombia, endangered species, extinctio

Forest biomass density across large climate gradients in northern South America is related to water availability but not with temperature

Understanding and predicting the likely response of ecosystems to climate change are crucial challenges for ecology and for conservation biology. Nowhere is this challenge greater than in the tropics as these forests store more than half the total atmospheric carbon stock in their biomass. Biomass is determined by the balance between biomass inputs (i.e., growth) and outputs (mortality). We can expect therefore that conditions that favor high growth rates, such as abundant water supply, warmth, and nutrient-rich soils will tend to correlate with high biomass stocks. Our main objective is to describe the patterns of above ground biomass (AGB) stocks across major tropical forests across climatic gradients in Northwestern South America. We gathered data from 200 plots across the region, at elevations ranging between 0 to 3400 m. We estimated AGB based on allometric equations and values for stem density, basal area, and wood density weighted by basal area at the plotlevel. We used two groups of climatic variables, namely mean annual temperature and actual evapotranspiration as surrogates of environmental energy, and annual precipitation, precipitation seasonality, and water availability as surrogates of water availability. We found that AGB is more closely related to water availability variables than to energy variables. In northwest South America, water availability influences carbon stocks principally by determining stand structure, i.e. basal area. When water deficits increase in tropical forests we can expect negative impact on biomass and hence carbon storage

Mycorrhizae: a key interaction for conservation of two endangered Magnolias from Andean forests

Background and aims – Magnolia species are highly endangered in neotropical forests where they are highly endemic and often very rare. However, little is known about their nutritional and soil conditions in natural forests. In this study, we focused on two endangered Magnolia species that cohabit in the Colombian Andean cloud forests in order to identify their conservation and nutritional status. We hypothesize that these species might exhibit mycorrhizal colonization that enhance nutrients uptake in poor and disturbed soils. Methods – Individuals of Magnolia jardinensis and M. yarumalensis were assessed in 11 000 m2 of Andean forests remnants from Jardín municipality (Antioquia, Colombia). Foliar and soil samples were analysed in the lab. Through a Principal Component Analysis (PCA) we identified the relationship between soil conditions and foliar nutrition. Root fragments and rhizosphere samples from seedlings and juveniles up to 3 m tall were collected to verify mycorrhizal colonization and presence of other microorganisms. Adults were excluded of the sampling due to the difficulties to differentiate their roots among the rest of the species in the forest fragments. Key results – The surveys show that the M. yarumalensis population has an inverted J-shaped diametric distribution suggesting a potential recovering population while the smaller overall distribution of M. jardinensis in all diametric categories suggests that this species is likely to become extinct. Both species grow in acidic, infertile soils, although foliar nutrient concentrations did not correlate with soil-nutrient availability. Such a discrepancy and the high colonization levels of mycorrhizae (60–70%) and dark septate endophytes (40–45%), suggest that plant-microorganisms may facilitate nutrition and enhance survival of Magnolia species in stressed environments. Other fungi and bacteria were also found in their rhizosphere, but their role with respect to Magnolia species remains unclear. Conclusions - Mycorrhizal colonization of endangered Magnolia species seems to play a key role to their performance in natural disturbed Andean forests. Aspects related to soil and rhizosphere ecology should be included in conservation projects for endangered and endemic plants. Key words – Rhizosphere, Andean cloud forests, Magnolia jardinensis, Magnolia yarumalensis, soil fertility, tree nutrition, conservation, mycorrhizae

Efecto del roble (Quercus humboldtii) sobre los ensamblajes de plantas de los robledales de Colombia

Spa: Generalmente se asume que las especies dominantes de un ecosistema están bien adaptadas a su entorno y tienen altas capacidades competitivas. Por otra parte, la teoría neutral ha propuesto que por procesos de deriva ecológica, ciertas especies tienden a dominar en un área determinada por efecto solamente de su capacidad de dispersión. Quisimos evaluar estas hipótesis, enfocándonos en el Roble (Quercus humboldtii), el cual es un especie dominante en algunos bosques en los Andes colombianos y de la cual se reportan efectos alelopáticos sobre otras especies, aunque las evidencias empíricas son escazas. En este trabajo evaluamos el efecto de la presencia de roble sobre el crecimiento y la densidad de la madera, dos rasgos funcionales relacionados, de las especies que lo acompañan usando 20 parcelas donde se tienen datos de crecimiento de 114 especies incluyendo el roble. Una prueba de T-pareada indica que las tasas de crecimiento del 70% de las especies disminuye en presencia del roble (T=50.28, p<0.001). Luego, mediante un ANOVA encontramos que las especies con tasas de crecimiento no afectadas por el roble tienen una densidad de la madera significativamente mayor que las afectadas (F=5.21, p<0.05). Estos resultados sugieren que el Roble tiene ventajas competitivas sobre un gran número de especies y ayudan a entender su a dominancia en muchas regiones de los andes. Adicionalmente, ya que la especie está siendo utilizada ampliamente en programas de recuperación de áreas degradadas los resultados puede ser una guía para diseñar modelos de restauración más eficientes. Palabras clave: Quercus Humboldtii; Tasa de crecimiento; Robledal; Competencia