Beneficial influence of plant neighbours on tree growth in drained forested peatlands: a case study

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Date: Sept. 2006
From: Canadian Journal of Forest Research(Vol. 36, Issue 9)
Publisher: NRC Research Press
Document Type: Article
Length: 7,036 words
Lexile Measure: 1520L

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Abstract: In boreal forest, drainage can be successfully used to lower the water-table level of postharvest forested peatland stands suffering from watering-up. The later vegetation revival and growth is suspected to gradually create a water-table drawdown described in this study as biological drainage. Its effect on the annual stump diameter increment of planted eastern larch (Larix laricina (Du Roi) K. Koch) and naturally regenerated black spruce (Picea mariana (Mill.) BSP) was studied on a postharvested and drained forested peatland located in eastern part of the Canadian boreal forest. A factor describing the neighbourhood occupancy of every subject tree was used to illustrate biological drainage in a retrospective growth analysis. Results showed the dual effect of the neighbourhood occupancy factor: competing situations close to the ditch and growth-favouring situations farther from it. In the latter case, the studied trees demonstrated better growth with moderately increasing neighbourhood occupancy. This was interpreted as evidence of the beneficial effect of biological drainage on tree growth. The presence of speckled alder (Alnus incana subsp. rugosa (Du Roi) J. Clausen) in the neighbourhood of selected trees corresponded to improved growth for both studied species.

Resume : En foret boreale, le drainage permet de rabattre efficacement la nappe phreatique des tourbieres forestieres recemment recoltees affectes par une nappe haute. La croissance subsequente de la vegetation forestiere sur ces sites est susceptible de creer un rabattement de la nappe phreatique, appele ici drainage biologique. Son effet sur l'accroissement annuel en diametre a la souche de plants de meleze laricin (Larix laricina (Du Roi) K. Koch) et de semis naturels d'epinette noire (Picea mariana (Mill.) BSP) a ete etudie sur une tourbiere forestiere recoltee et drainee. Un facteur decrivant l'occupation du voisinage des arbres etudies a ete utilise afin de decrire le drainage biologique dans une analyse de croissance retrospective. Les resultats ont demontre les deux effets opposes de l'occupation du voisinage sur l'accroissement en diametre : des situations de competition a proximite des fosses et des situations favorables a la croissance forestiere plus loin. Dans ce dernier cas, les arbres etudies ont demontres une meilleure croissance avec une augmentation moderee de l'occupation du voisinage. Ceci a ete interprete comme une demonstration de l'effet benefique du drainage biologique sur la croissance forestiere. La presence d'aulne rugueux (Alnus incana subsp. rugosa (Du Roi) J. Clausen) dans le voisinage des arbres etudies correspondait a une croissance accrue des deux essences etudiees.

Introduction

Boreal forested peatland sites are susceptible to watering-up after canopy removal (Heikurainen and Paivanen 1970; Dube et al. 1995; Roy et al. 1997). This rise of the water-table level is principally caused by the abrupt change in evapotranspiration resulting from the removal of the higher vegetation cover. The reduction of interception and transpiration were each responsible for about 50% the watering-up (Dube and Plamondon 1995).

High water-table level results in anoxic conditions within the rooting zone (Ponnamperuma 1972; Campbell 1980), cold soil temperature (Lieffers 1988), and diminished soil volume available for rooting and nutrient uptake (Lieffers and Rothwell 1987;...

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Gale Document Number: GALE|A154395024