Pinus species show remarkable ontogenetic differences in needle morphology (heterophylly) between... more Pinus species show remarkable ontogenetic differences in needle morphology (heterophylly) between juvenile and adult vegetative phases. This developmental shift may play an adaptative role in their success under diverse habitats. As a first step to know the functional differences between each vegetative phase, we compared water loss through the cuticles of juvenile and adult needles of 21-month-old nursery-grown seedlings of nine hard pine species. Cuticular transpiration (CT), calculated after complete stomatal closure, was obtained by leaf-drying curves, and was related to leaf, ontogenetic and climatic parameters. The rate of cuticular transpiration (RCT) between juvenile and adult needles differed across pine species, and in particular segregated the Mediterranean species Pinus canariensis and P. halepensis, from the Eurasian P. uncinata and introduced species P. radiata. For these species, RCT was always higher in juvenile needles. The different leaf and ontogenic parameters studied were correlated with the variation in RCT among the nine pine species. We discuss this relationship in the light of the species ecology. Besides their possible adaptive interpretation, these results suggest an underlying need to consider the ontogenetic heterophylly when assessing functional traits in hard pine seedlings, in particular those traits that govern water relations.
Natural regeneration of stone pine (Pinus pinea L.) stands in the Central Range of Spain can be d... more Natural regeneration of stone pine (Pinus pinea L.) stands in the Central Range of Spain can be difficult to attain. The success of this regeneration is affected by factors such as the total amount of seed available, the short dispersal ability of the pinyon, the conditions required for germination, specific problems associated with the establishment, early survival of the seedlings due to severe summer heat and drought, competition for water and mineral resources and grazing damage. This study focuses on seed availability. The amount of available seeds depends on the number and size of the cones and the number of viable pinyons within the cones. In stone pine stands, both variables show great year to year variability. Both cone and seed production, for a given year, are also conditioned by the vigour and health of the tree, its size, the condition and attributes of the stand and the loss of seed through pests or predation. In this study, the main factors which influence cone and pinyon production are identified and a multivariate model to predict annual cone and viable seed production is developed. To consider the correlation among observations coming from the same tree, stand or year, random components are included in the model. The multivariate random structure allows for future calibration of the model for a given year from a small additional sample of observations. It is important to know the total amount of viable seed produced in a stand for a given year since regeneration cuttings for Stone pine should be concentrated in high crop years.
Quantifying the carbon balance in forests is one of the main challenges if carbon fixation is to ... more Quantifying the carbon balance in forests is one of the main challenges if carbon fixation is to be considered amongst the objectives of forest management (Montera et al., 2005). Carbon is accumulated in forests through an increment in biomass, dead organic matter and soil carbon, and is released through respiration and decomposition. In the Mediterranean area, forest fires are also an important way of releasing CO2 to the atmosphere. Due to the complexity of making a global evaluation of all these processes, studies of sub-processes are necessary to better understand the processes involved. In this chapter, estimates of carbon sequestration in Mediterranean pine forests from a number of studies and areas are presented along with associated information on how forest management influences this process. The estimates come from a number of sources including carbon stock estimates under different management plans using a chronosequence trial, under different thinning regimes or age structures using growth models, and from a model for estimating coarse woody debris.
Pinus species show remarkable ontogenetic differences in needle morphology (heterophylly) between... more Pinus species show remarkable ontogenetic differences in needle morphology (heterophylly) between juvenile and adult vegetative phases. This developmental shift may play an adaptative role in their success under diverse habitats. As a first step to know the functional differences between each vegetative phase, we compared water loss through the cuticles of juvenile and adult needles of 21-month-old nursery-grown seedlings of nine hard pine species. Cuticular transpiration (CT), calculated after complete stomatal closure, was obtained by leaf-drying curves, and was related to leaf, ontogenetic and climatic parameters. The rate of cuticular transpiration (RCT) between juvenile and adult needles differed across pine species, and in particular segregated the Mediterranean species Pinus canariensis and P. halepensis, from the Eurasian P. uncinata and introduced species P. radiata. For these species, RCT was always higher in juvenile needles. The different leaf and ontogenic parameters studied were correlated with the variation in RCT among the nine pine species. We discuss this relationship in the light of the species ecology. Besides their possible adaptive interpretation, these results suggest an underlying need to consider the ontogenetic heterophylly when assessing functional traits in hard pine seedlings, in particular those traits that govern water relations.
Natural regeneration of stone pine (Pinus pinea L.) stands in the Central Range of Spain can be d... more Natural regeneration of stone pine (Pinus pinea L.) stands in the Central Range of Spain can be difficult to attain. The success of this regeneration is affected by factors such as the total amount of seed available, the short dispersal ability of the pinyon, the conditions required for germination, specific problems associated with the establishment, early survival of the seedlings due to severe summer heat and drought, competition for water and mineral resources and grazing damage. This study focuses on seed availability. The amount of available seeds depends on the number and size of the cones and the number of viable pinyons within the cones. In stone pine stands, both variables show great year to year variability. Both cone and seed production, for a given year, are also conditioned by the vigour and health of the tree, its size, the condition and attributes of the stand and the loss of seed through pests or predation. In this study, the main factors which influence cone and pinyon production are identified and a multivariate model to predict annual cone and viable seed production is developed. To consider the correlation among observations coming from the same tree, stand or year, random components are included in the model. The multivariate random structure allows for future calibration of the model for a given year from a small additional sample of observations. It is important to know the total amount of viable seed produced in a stand for a given year since regeneration cuttings for Stone pine should be concentrated in high crop years.
Quantifying the carbon balance in forests is one of the main challenges if carbon fixation is to ... more Quantifying the carbon balance in forests is one of the main challenges if carbon fixation is to be considered amongst the objectives of forest management (Montera et al., 2005). Carbon is accumulated in forests through an increment in biomass, dead organic matter and soil carbon, and is released through respiration and decomposition. In the Mediterranean area, forest fires are also an important way of releasing CO2 to the atmosphere. Due to the complexity of making a global evaluation of all these processes, studies of sub-processes are necessary to better understand the processes involved. In this chapter, estimates of carbon sequestration in Mediterranean pine forests from a number of studies and areas are presented along with associated information on how forest management influences this process. The estimates come from a number of sources including carbon stock estimates under different management plans using a chronosequence trial, under different thinning regimes or age structures using growth models, and from a model for estimating coarse woody debris.
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