Gap‐phase dynamics and coexistence of a long‐lived pioneer and shade‐tolerant tree species in the canopy of an old‐growth coastal temperate rain forest of Chiloé Island, Chile

Abstract

Aim A major question with regard to the ecology of temperate rain forests in south-central Chile is how pioneer and shade-tolerant tree species coexist in oldgrowth forests. We explored the correspondence between tree regeneration dynamics and life-history traits to explain the coexistence of these two functional types in stands apparently representing a non-equilibrium mixture.Location This study was conducted in northern Chiloé Island, Chile (41.6°S, 73.9°W) in a temperate coastal rain forest with no evidence of stand disruption by human impact.Methods We assessed stand structure by sampling all stems within two 50 · 20 m and four 5 · 100 m plots. A 600-m long transect, with 20 uniformly spaced sampling points, was used to quantify seedling and sapling densities, obtain increment cores, and randomly select 10 tree-fall gaps. We used tree-ring analysis to assess establishment periods and to relate the influences of disturbances to the regeneration dynamics of the main canopy species.Results Canopy emergent tree species were the long-lived pioneer Eucryphia cordifolia and the shade-tolerant Aextoxicon punctatum. Shade-tolerant species such as Laureliopsis philippiana and several species of Myrtaceae occupied the main canopy. The stem diameter distribution for E. cordifolia was distinctly unimodal, while for A. punctatum it was multi-modal, with all age classes represented. Myrtaceae accounted for most of the small trees. Most tree seedlings and saplings occurred beneath canopy gaps. Based on tree-ring counts, the largest individuals of A. punctatum and E. cordifolia had minimum ages estimated to be > 350 years and > 286 years, respectively. Shade-tolerant Myrtaceae species and L. philippiana had shorter life spans (< 200 years). Most growth releases, regardless of tree species, were moderate and have occurred continuously since 1750.Main conclusions We suggest that this coastal forest has remained largely free of stand-disrupting disturbances for at least 450 years, without substantial changes in canopy composition. Release patterns are consistent with this hypothesis and suggest that the disturbance regime is dominated by individual tree-fall gaps, with sporadic multiple tree falls. Long life spans, maximum height and differences in shade tolerance provide a basis for understanding the longterm coexistence of pioneer and shade-tolerant tree species in this coastal, oldgrowth rain forest, despite the rarity of major disturbances.

Estación Biológica Senda Darwin: Investigación ecológica de largo plazo en la interfase ciencia-sociedad

“…Además el dosel alberga una gran diversidad de pequeños organismos, especialmente invertebrados, musgos y líquenes, muchos desconocidos para la ciencia (Ozzane et al 2003, Benzing 2004, Erwin 2004. Estudios recientes (Díaz 2009) de las copas de árboles emergentes del dosel (25-30 m de altura) en bosques costeros de tipo Valdiviano, con mínima perturbación humana, cercanos a la EBSD (e.g., Gutiérrez et al 2008b) han mostrado que un solo gran árbol emergente alberga un 30 % de todas las especies de epífitas vasculares descritas para la región de bosques templados siempreverdes y un 50 % de las especies chilenas conocidas la familia Himenophyllaceae (helechos película). Es decir, cada gran árbol del dosel constituye una extraordinaria reserva de diversidad.…”

Forest Typification to Characterize the Structure and Composition of Old-growth Evergreen Forests on Chiloe Island, North Patagonia (Chile)

“…The dominance of small-scale disturbances, plus the absence of human disturbance, allows the coexistence of shade-tolerant and shade-intolerant species, and the existence of large, but decreasing, areas of forests in advanced successional stages [11,12]. South of this north-central region of Chiloé Island, the only evergreen forest for which its structure and dynamics has been described is found in the work by Innes [18] in the Taitao Peninsula (46° S).…”

“…In the evergreen forests of north-central Chiloé Island, gap dynamics plays an important role in regeneration of tree species, by being the dominant disturbance regime in old-growth forests [11,12,16,17]. The dominance of small-scale disturbances, plus the absence of human disturbance, allows the coexistence of shade-tolerant and shade-intolerant species, and the existence of large, but decreasing, areas of forests in advanced successional stages [11,12].…”

“…Currently, Chiloé Island (41°48' S-43°27' S) has an approximate area of 550,000 ha covered by the Evergreen forest type in different stages of development and conservation [7]. In the last three decades, a series of studies on the ecology, dynamics and structure of forests in northern and central Chiloé have been published (e.g., [8][9][10][11][12][13][14]). These studies refer to the Evergreen forest type, when oriented to forestry, or to either Valdivian of North-Patagonian temperate rainforests, a phytogeographical division developed by Veblen et al [15] that is usually followed in forest ecology studies.…”

Árboles monumentales: un patrimonio natural no reconocido en Chile

“…Por ejemplo, coihues monumentales tienen área de copas que en promedio alcanzan los 380 m 2 (incluso superan 700 m 2 , datos del autor). Al caer estos árboles abren al menos esta área del dosel lo que potencia la regeneración arbórea (Gutiérrez et al 2008).…”