The effects of a regeneration felling on photosynthetic photon flux density and regeneration growth in a Nothofagus pumilio forest

Abstract

Photosynthetic photon Xux density (PPFD) during the growing season and regeneration growth (height and base stem diameter) were investigated in two natural stands in the Patagonian region of Chile, one without silvicultural management and another with a regenerative felling under a shelterwood system. PPFD was measured by means of Wfteen sensors (quantum Li-190SA) installed in each stand and distributed within three canopy openness grades. Four regeneration plots (1 m 2 ) were established around each sensor. In each of the plots, the height and base diameter of ten labelled plants within the upper regeneration layer were measured in the growing seasons 2001-2002 and 2002-2003. In the stand with regeneration felling total PPFD in the growing season was 2.5-2.9 times higher than in the stand without intervention. In both stands, total PPFD in the growing season increased by about 420 mmol/m 2 when the relative canopy, which was in the range between 30 and 70%, was reduced by 10%. An identical behaviour was observed for the height and base stem diameter increases reXecting a clear eVect of intervention and canopy coverage on the magnitude of PPFD received by the regeneration and its development.

Site quality influence over understory plant diversity in old-growth and harvested Nothofagus pumilio forests

“…Nothofagus pumilio forest management by shelterwood cuts, mainly applied to meet timber objectives, homogenizes canopy structure (Martínez Pastur et al, 2000) and microclimatic conditions (Caldentey et al, 2009), reduces microenvironments, and gradually since harvesting increase similarity among understory of different site quality stands. This was observed in the NMS ordination (Fig.…”

“…Shelterwood emulates natural forest dynamics through the opening of the canopy at large scale and leaving seed trees, using a set of cuttings to stimulate natural regeneration such as one or tow preparation cuts, plus regeneration cut and overstory removal. Shelterwood cuts in Nothofagus forests also produce changes in microclimatic conditions at understory level (e.g., soil moisture, light and temperature) (Caldentey et al, 2005(Caldentey et al, , 2009) and in litter fluxes and decomposition processes in the forest floor (Caldentey et al, 2001). Under timber production objectives, this harvesting system can lead to N. pumilio forest homogenization, producing loss of different habitats commonly observed inside primary forests (Martínez Pastur et al, 2002).…”

Microclima en el interior de un bosque de Nothofagus pumilio y el efecto de una corta de regeneración

“…El sistema silvicultural que ha resultado más adecuado para intervenir los bosques de lenga con potencial comercial es el de cortas sucesivas con cortas de regeneración natural bajo dosel de protección o también llamado cortas de protección (Schmidt et al 2003). En bosques vírgenes maduros el sistema se inicia con cortas de regeneración que disminuyen la cobertura del dosel arbóreo entre el 40 y el 60 %, con ello aumentan los montos de luminosidad, favoreciendo el establecimiento de la regeneración y su crecimiento en altura (Schmidt et al 2003, Rosenfeld et al 2006, Caldentey et al 2009.…”

“…Respecto a cambios microclimáticos en estos bosques debido a la aplicación de cortas de regeneración, solamente se han delineado tendencias generales a partir de un tiempo reducido de observaciones (Caldentey et al 1999(Caldentey et al , 2000, registrándose además aumentos en el flujo de fotones fotosintéticos (Caldentey et al 2009). En este estudio el objetivo es analizar el comportamiento de variables microclimáticas a lo largo de siete años de registros continuos, en un bosque de N. pumilio no intervenido, en un bosque sometido a una corta de regeneración y en un sector desarbolado.…”

Seed production and recruitment in primary and harvested Nothofagus pumilio forests: Influence of regional climate and years after cuttings

“…Retention levels are directly related with the microclimatic conditions generated into the forests that were harvested (Chen et al, 1993(Chen et al, , 1995, e.g. amount of rainfall that reaches to the forest ground, available radiation under the canopy, wind exposure and temperature (Richter & Frangi, 1992;Caldentey et al, 2005Caldentey et al, , 2009. These factors had the biggest influences…”