Seedling Mortality in Regeneration of Aleppo Pine Following Fire and Attack by the Scale Insect Matsucoccus josephi

Abstract

Mortality of Pinus halepensis seedlings was investigated in Israel during the first years of natural regeneration after fire, with special emphasis on the role of Matsucoccus josephi, drought and competition. The investigations were conducted in the native natural forest on Mt. Carmel, and in a plantation severely damaged by the scale insect at Horeshim in Samaria. M josephi was the dominant mortality agent during the first five years after regeneration, killing almost 73 % and 54% of the seedlings at Mt. Carmel and Horeshim, respectively. Neither injury nor mortality due to the scale insect was recorded during the first year after regeneration, but subsequently mortality occurred during the third and the fourth years. About 23% of the seedlings died due to drought, interspecific and intraspecific competition. Mortality due to other biotic agents, i.e., Hylastes linearis and Pityophthorus pubescens was practically nil. It is shown that resistance of regenerating population of native P. halepensis on Mt. Carmel to the scale did not differ significantly from that of regeneration of a planted Aleppo pine forest of unknown seed sources at Horeshim, despite differences in the level of injury to the adult trees on each site. Five years after natural seeding seedling density in scale-infested plots is high enough to ensure stand development. This second growth possibly displays lower susceptibility to M. josephi than the present adult population.

Responses of forest trees to single and multiple environmental stresses from seedlings to mature plants: Past stress history, stress interactions, tolerance and acclimation

“…Tree water stress resistance also increases with increasing tree size, accompanying greater fractional investment of plant biomass in roots in larger plants Tomlinson and Anderson, 1998). In fact, large trees can tolerate sustained drought periods extending over the entire growing season and even across multiple growing seasons , while such severe drought periods can lead to mortality of seedlings and saplings (for seedling physiological responses see Mendel et al, 1997;Mueller et al, 2005;Lopez and Kursar, 2007). The presence of large carbon reserves in mature plants can also allow for new shoot formation and resprouting (in resprouting species) following catastrophic events such as fire (Koskela, 2000;Langley et al, 2002) and breakage of branches or entire stem (Génard et al, 1998;Verdaguer and Ojeda, 2002;van Bloem et al, 2003;Wong et al, 2005;Vargas, 2009;Vargas et al, 2009).…”

Effects of silviculture treatments on vegetation after fire in Pinus halepensis Mill. woodlands (SE Spain)

“…In this sense, several studies carried out in the Mediterranean Basin have shown that P. halepensis seedlings and saplings increase growth if both intra-and interspecific competition are reduced [27,29]. Scrubbing, which is focused on the seedlings survival [7] is another silviculture treatment carried out in early stages of pine stands (no more than 2 years old).…”

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“…The pattern of higher mortality of smaller trees in CM was consistent with the recent die off event of Pinus edulis between 2002 and 2004 Arizona, New Mexico, Colorado, and Utah, although Mueller et al (2005) observed the opposite pattern during the 1996 and 2002 acute droughts in piñon-juniper woodlands of northern Arizona. My results in the CM were consistent with the trend of high seedling and sapling mortality under drought relative to larger trees that, with their deeper root systems and larger carbon stores, were able to survive those same drought events (Mendel et al, 1997;Mueller et al, 2005;Lopez andKursar, 2007, Ganey andVojta 2011). The lack of evidence of bark beetle infestation in trees that died over the sampling interval also suggests that the high mortality of small-diameter trees was not related to insect attack.…”