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

We 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-tolera...

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Autores principales:	ARAVENA,JUAN C., CARMONA,MARTÍN R., PÉREZ,CECILIA A., ARMESTO,JUAN J.
Lenguaje:	English
Publicado:	Sociedad de Biología de Chile 2002
Materias:	forest succession fire disturbance biodiversity shade tolerance forest dynamics
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-078X2002000200007
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spelling	oai:scielo:S0716-078X20020002000072003-05-12Changes in tree species richness, stand structure and soil properties in a successional chronosequence in northern Chiloé Island, ChileARAVENA,JUAN C.CARMONA,MARTÍN R.PÉREZ,CECILIA A.ARMESTO,JUAN J. forest succession fire disturbance biodiversity shade tolerance forest dynamics We 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 20th 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 disturbance. However, as forests in the area become increasingly isolated, affected by recurrent fire, and other forms of human impact, their ability to recover their original structure and biodiversity will probably be impaired. Threshold levels of deforestation, at the landscape scale, that would impinge on successional trends at the patch scale remain an important open question for land managersinfo:eu-repo/semantics/openAccessSociedad de Biología de ChileRevista chilena de historia natural v.75 n.2 20022002-06-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-078X2002000200007en10.4067/S0716-078X2002000200007
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	forest succession fire disturbance biodiversity shade tolerance forest dynamics
spellingShingle	forest succession fire disturbance biodiversity shade tolerance forest dynamics ARAVENA,JUAN C. CARMONA,MARTÍN R. PÉREZ,CECILIA A. ARMESTO,JUAN J. Changes in tree species richness, stand structure and soil properties in a successional chronosequence in northern Chiloé Island, Chile
description	We 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 20th 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 disturbance. However, as forests in the area become increasingly isolated, affected by recurrent fire, and other forms of human impact, their ability to recover their original structure and biodiversity will probably be impaired. Threshold levels of deforestation, at the landscape scale, that would impinge on successional trends at the patch scale remain an important open question for land managers
author	ARAVENA,JUAN C. CARMONA,MARTÍN R. PÉREZ,CECILIA A. ARMESTO,JUAN J.
author_facet	ARAVENA,JUAN C. CARMONA,MARTÍN R. PÉREZ,CECILIA A. ARMESTO,JUAN J.
author_sort	ARAVENA,JUAN C.
title	Changes in tree species richness, stand structure and soil properties in a successional chronosequence in northern Chiloé Island, Chile
title_short	Changes in tree species richness, stand structure and soil properties in a successional chronosequence in northern Chiloé Island, Chile
title_full	Changes in tree species richness, stand structure and soil properties in a successional chronosequence in northern Chiloé Island, Chile
title_fullStr	Changes in tree species richness, stand structure and soil properties in a successional chronosequence in northern Chiloé Island, Chile
title_full_unstemmed	Changes in tree species richness, stand structure and soil properties in a successional chronosequence in northern Chiloé Island, Chile
title_sort	changes in tree species richness, stand structure and soil properties in a successional chronosequence in northern chiloé island, chile
publisher	Sociedad de Biología de Chile
publishDate	2002
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-078X2002000200007
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Changes in tree species richness, stand structure and soil properties in a successional chronosequence in northern Chiloé Island, Chile

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