Decoupling of soil development and plant succession along a 60000 years chronosequence in Llaima Volcano, Chile Desacoplamiento del desarrollo del suelo y la sucesión vegetal a lo largo de una cronosecuencia de 60 mil a os en el volcán Llaima, Chile

Few studies have investigated the long-term evolution of nutrient limitation in ecosystems developed on volcanic soils. To approach the problem, we used "space for time substitution" to compare sites with the same state factors, except for the time elapsed since disturbance. Forests of Conguillio National Park in southern of Chile occur on volcanic soils that developed from lava flows and ash deposits of different ages originated from the activity of Llaima volcano. In this study we evaluate the patterns of change in carbon, nitrogen and phosphorus in soils and leaves, as well as changes in tree diversity and basal area along a chronosequence of volcanic substrates from 50 to 60,000 years AP (eight sites). We assessed the evolution of N and P limitation in plants by comparing foliar N/P ratios and the efficiency in the use of nutrients through foliar C/P and C/N ratios. Values of total C, N and P in surface soils were low in the first 250 years of succession, increasing up to a maximum concentration at intermediate stages of succession (300-700 yr), to decline in later successional stages, a pattern also observed in a volcanic chronosequence from Hawaii. We found a decrease in basal area and an increase in diversity of woody species in advanced stages of the chronosequence. Foliar N and P concentrations slightly increased through the chronosequence in both evergreen and deciduous tree species. The foliar N/P ratio did not change along the chronosequence in both deciduous and evergreen species, but differed between evergreen and deciduous trees. The successional increase in tree diversity is explicated by a greater proportion of evergreen angiosperms with efficient P use. Despite the retrogression phase documented by more the decrease in the total contents of N and P in soils, we did not detect a similar decline in the foliar contents of N and P, which suggests that plant and soil nutrient contents are decoupled. Existen pocos estudios que describan la evolución de nutrientes en ecosistemas desarrollados sobre suelos volcánicos. Una forma de abordar este problema es a través del método de "sustitución de espacio por tiempo", en donde los sitios poseen los mismos factores de estado, excepto el tiempo transcurrido desde la perturbación. El bosque del Parque Nacional Conguillío en el sur de Chile se distribuye sobre suelos desarrollados a partir de lavas y cenizas de diferentes edades originadas por actividad del volcán Llaima. En este estudio se evaluaron los patrones de cambio en las concentraciones de carbono, nitrógeno y fósforo en suelos y hojas, junto