Changes in tree species richness, stand structure and soil properties in a successional chronosequence in northern Chiloé Island, Chile

Abstract

Changes in tree species richness, stand structure and soil properties in a successional chronosequence in northern Chiloé Island, ChileCambios en la riqueza de especies arbóreas, estructura de rodales y propiedades del suelo en una cronosecuencia sucesional en el norte de la Isla de Chiloé, Chile ABSTRACTWe studied a chronosequence of forest fragments in northern Chiloé Island, southern Chile, with the aim of assessing ecosystem recovery patterns following anthropogenic disturbance. Hypotheses regarding successional trends in tree species richness, the replacement of shade-intolerant by shade-tolerant species, and the impact of disturbance on soil properties were evaluated in nine forest stands. The chronosequence encompassed two early (minimum stand age <15 years), three mid-successional (30-60 years), three late-successional (129-134 years), and one old-growth stand (ca. 200 years). Stand ages were estimated by coring a minimum of 30 canopy trees in each stand. Early and mid-successional stands showed evidence of human disturbance by fire of moderate intensity, with few scattered old trees surviving the fire. We determined densities and basal areas of all trees in a 50 x 20 m plot, and densities of saplings and seedlings in subsamples of each plot. Soil pH, total carbon (C) and nitrogen (N) contents, available N, and bulk density were used to characterize soil processes across the chronosequence. In contrast to the hypothesis that predicts a decline in tree species richness during the course of succession due to competitive exclusion of pioneers, species richness of canopy trees increased from 3 to 13 through the chronosequence. This trend was accompanied by a more even distribution of species importance values in late succession. Changes in richness were unrelated to stem densities, which were highest in mid-successional forests. The number of species of woody seedlings and saplings did not change with stand age. Most tree species, both shade tolerant and intolerants, were present as seedlings in all the stands, but canopy dominance shifted from shade-intolerants in early and mid-successional forests to shade-tolerant species in late-successional and old-growth stands. We did not observe a complete replacement of these two groups of species, as shade-intolerant trees were still present in the canopy and/or understory of older stands. The successional trend fits Egler's Initial Floristic Composition Model, whereby differences in life history attributes among tree species account for major changes in dominance through succession. Soil properties were generally similar across the chronosequence of stands, suggesting that both ecosystem processes and tree regeneration were fairly resilient to moderate-intensity fire. We conclude that because of the relatively short history of human impact in the area, largely limited to the 20 th century, and the carry over of structural elements such as snags, logs, and large living trees in disturbed stands, lowland forest patches in northern Chiloé show resilience to human di...

Non-Symbiotic Nitrogen Fixation, Net Nitrogen Mineralization and Denitrification in Evergreen Forests of Chiloé Island, Chile: A Comparison With Other Temperate Forests

“…Lowland temperate rain forests in southern Chile have undergone extensive reduction in cover, due to disturbance by fire and logging. The present landscape is comprised by a mosaic of fragmented second-growth forests of different ages, within a matrix of pastures, cropfields and wetlands (Wilson & Armesto 1996, Aravena et al 2002. The montane temperate forests studied were located at 600 m elevation in National Park Chiloé (Pérez et al 1998).…”

Effect of canopy openness on growth, specific leaf area, and survival of tree seedlings in a temperate rainforest of Chiloé Island, Chile

“…This finding is important because in many forests, regeneration depends largely on the establishment of seedling banks (Nava & del Amo 1985;Armesto & Fuentes 1988). D. winteri usually forms seedling banks in advanced successional stages (Aravena et al 2002). Results also suggest that D. winteri presents higher phenotypic plasticity than G. avellana.…”

“…Each sample was placed in a drying oven at 75°C for 72 h after the fresh weight had been obtained to the nearest 0.1 mg, and re-weighed following this period. Finally, the amount of total inorganic nitrogen (nitrate plus ammonium) was determined at the beginning of the experiment and for winter samples (6 months later) by means of fractionated micro distillation, extracted with a 1% KAl(SO 4 ) 2 solution (Aravena et al 2002). Winter samples were used for this analysis because this period was the mid point of the experiment and the data covered the six previous months.…”

The Ecological Classification of Coastal Wet Longleaf Pine (Pinus palustris) of Florida from Reference Conditions

“…Patches previous grouped by the three age-tree size classes were further stratified using the specific ages of the cohorts they contained into five distinct time intervals (6 -10, 17 -34, 36 -52, 60 -71, 86 -110). This allowed us to analyze changes in forest structure and plant species composition from one time interval to the next [58,59].…”