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Albornoz F.E.,University of Santiago de Chile | Albornoz F.E.,Institute Ecologia and Biodiversidad IEB | Albornoz F.E.,University of Western Australia | Gaxiola A.,University of Santiago de Chile | And 6 more authors.
Plant Ecology | Year: 2013

Nucleation is a successional process in which extant vegetation facilitates seed dispersal and recruitment of other individuals and species around focal points in the landscape, leading to ecosystem recovery. This is an important process in disturbed sites where regeneration is limited by abiotic conditions or restrictive seed dispersal. We investigated forest recovery in a large burned area of evergreen temperate rainforest in southern Chile subjected to seasonal soil waterlogging, and assessed the relevance of nucleation processes in overcoming biotic and physical barriers for tree species regeneration. We measured richness and abundance of woody species in relation to patch size, as well as abiotic factors such as light and soil moisture within and outside patches. We found higher tree regeneration in existing patches than in open areas. We recorded an increase of patch size over time, associated with the increase in number of individuals and tree species. Soils in open areas were waterlogged, especially in winter, while patches were not. Trees in patches also acted as perches, enhancing bird-mediated seed rain. Seeds of fleshy-fruited tree species arrived first at patches and seedlings were more frequent in smaller, younger patches, while the number of seedlings of trees with wind-dispersed seeds increased in larger, older patches. Our study shows that woody species seem incapable of recruiting in open and waterlogged soils and depend strongly on extant vegetation patches to establish. In this fire-disturbed evergreen temperate forest regeneration occurs via nucleation, where new individuals contribute to a centrifugal kind of patch growth. © 2013 Springer Science+Business Media Dordrecht.

Gallardo M.B.,University of Santiago de Chile | Gallardo M.B.,Institute Ecologia and Biodiversidad IEB | Perez C.,University of Santiago de Chile | Perez C.,Institute Ecologia and Biodiversidad IEB | And 4 more authors.
Revista Chilena de Historia Natural | Year: 2012

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 Conguillío National Park in southern of Chile occur on volcanic soils that developed from lava fl ows 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 effi ciency 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 fi rst 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 effi cient 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. © Sociedad de Biología de Chile.

Seaman B.J.,University of Santiago de Chile | Seaman B.J.,Institute Ecologia and Biodiversidad IEB | Albornoz F.E.,University of Western Australia | Armesto J.J.,University of Santiago de Chile | And 5 more authors.
Austral Ecology | Year: 2015

Nitrogen and phosphorus are the main elements limiting net primary production in terrestrial ecosystems. When growing in nutrient-poor soils, plants develop physiological mechanisms to conserve nutrients, such as reabsorbing elements from senescing foliage (i.e. nutrient retranslocation). We investigated the changes in soil N and P in post-fire succession in temperate rainforests of southern Chile. In this area, forest recovery often leads to spatially scattered, discrete regeneration with patches varying in age, area, species richness and tree cover, representing different degrees of recovery from disturbance. We hypothesized that soil nutrient concentrations should differ among tree regenerating patches depending on the progress of forest regeneration and that nutrient resorption should increase over time as colonizing trees respond to limited soil nutrients. To evaluate these hypotheses, we sampled 40 regeneration patches in an area of 5ha, spanning a broad range of vegetation complexity, and collected soil, tree foliage and litter samples to determine N and P concentrations. Nutrient concentrations in leaf litter were interpreted as nutrient resorption proficiency. We found that soil P was negatively correlated with all the indicators of successional progress, whereas total soil N was independent of the successional progress. Foliar N and P were unrelated to soil nutrient concentrations; however, litter N was negatively related to soil N, and litter P was positively related with soil P. Finally, foliar N:P ratios ranged from 16 to 25, which suggests that P limitation can hamper post-fire regeneration. We provide evidence that after human-induced fires, succession in temperate forests of Chile can become nutrient limited and that high nutrient retranslocation is a key nutrient conservation strategy for regenerating tree communities. © 2015 Ecological Society of Australia.

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