Search

In the last five years, sharp increases in the price of natural resins, accompanied by technological advances directed toward mechanization, have made resin tapping a strategic activity for rural development and forest conservation. The resin industry demands more efficient tapping methods and forest management plans as a way to increase competitiveness in a global market. Understanding the effects of environmental conditions on resin yield, especially under the current scenario of climate change, is key to improving techniques and plans in the resin industry. This study aims to evaluate the intra- and inter-annual effects of climate conditions and soil water availability on resin yield in tapped Pinus pinaster stands. The individual resin yield of 26 tapped trees growing at two locations with different stand densities and soil characteristics was measured fortnightly during the tapping season (June to October) for four years. The study was complemented with an analysis of changes in xylem anatomy over the four years, with a focus on axial resin canal traits, including 12 non-tapped trees as controls. Intra-annual variation in resin yield was strongly correlated with temperature, solar radiation, potential evapotranspiration and water deficit. Inter-annual variation in resin yield and resin canal abundance were correlated with temperature and water deficit in spring, but above a certain threshold of cumulated water deficit in summer rainfall favored resin yield. Under adverse climate scenarios where resource optimization is desirable, a reduced tapping season during the warmest months (June–September) would be advisable, assuming a very small production loss. Similarly, in years with a rainy summer and/or dry spring, a slightly longer tapping season could be suggested, as resin yield increases after these events. [ABSTRACT FROM AUTHOR]

• Resin yield was highly variable among provenance regions. • Narrow-sense heritability of resin yield was high. • Genetic correlation between pine growth and resin yield was not significant. • Across phenotypes and provenance regions, resin yield and growth were correlated. • Selection and breeding programs will help to increase resin yield. The potential of pine resin as a renewable non-timber product is furthering the socioeconomic relevance of the resin industry in Europe, where maritime pine (Pinus pinaster Ait.) is the main tapped species. Characterizing maritime pine genetic resources in terms of resin yield potential and its covariation with tree growth is crucial to implement efficient tree breeding programs aiming to maximize resin yield without negatively impact tree growth. We explored genetic variation in resin yield and tree growth among provenance regions, populations within regions, and families of maritime pine. We used a progeny trial located at Central Spain to estimate additive genetic variation and heritability of resin yield, and a common garden located at Northwest Spain to explore variation among provenance regions and populations within regions. Resin yield was assessed in both trials with and without sulphuric-based stimulant paste. Association between growth and resin yield at different levels (phenotypes, families, populations and provenance regions) was also explored. Growth and resin yield were highly variable within populations, with narrow-sense heritability estimates being particularly high for resin yield (h i 2 = 0.49). Growth varied significantly across provenance regions and populations within regions, while resin yield was only variable among provenance regions. Genetic variation in resin yield was similar in trees with and without stimulant paste. We did not find evidence of genetic correlations between growth and resin yield. However, at the phenotype level resin yield and growth were significantly correlated, although the sign of such association switched between trials. Across provenance regions, growth and resin yield where negatively correlated. Altogether, the high narrow-sense heritability estimate, the highly consistent genetic variation and the lack of negative genetic correlation with growth evidence the opportunity for implementing breeding programs to increase resin yield in maritime pine forests. [ABSTRACT FROM AUTHOR]

• Results suggest a high resin tapping potential of Atlantic maritime pine forests. • Tree age strongly influences resin yield. Only stands older than 30 yrs should be tapped. • Under Oceanic conditions resin tapping should be a seasonal activity. • Frequency of grooves could be higher than previously thought. • Microtapping emerges as a reliable tool to predict resin yield potential. Pine resin is a highly valuable and sought-after non-timber forest product with multiple uses in many industrial sectors. Maritime pine (Pinus pinaster Ait.) is the main tapped species in Europe, where resin tapping activities are concentrated in only a few specific Mediterranean regions. Although maritime pine also occupies vast extensions under Atlantic climates, the resin tapping potential of these forests remains unexplored. The objectives of this study were to determine the main factors driving resin yield under Atlantic conditions and to adapt extraction practices to these regions. Resin yield was assessed in two naturally regenerated maritime pine forests in NW Spain. The effects of tree age, inter-tree competition, dendrometry, seasonality and wounding time on resin production were tested. The feasibility of a simple and rapid microtapping procedure to predict resin yield was also assessed. Tree age was identified as the main factor driving resin production, which increased considerably with tree age. Tree slenderness, tree size and inter-tree competition also significantly influenced resin production, although the effects were lower and likely mediated by age variation. Resin yield followed marked seasonal patterns, with maximum production in late summer and minimum production in winter. Resin flow decreased rapidly with time after wounding. More than 95 % of resin yield flowed in the first week after trees were wounded. The proposed microtapping procedure, which estimates resin flow from small wounds in just a few days, was shown to be a useful and reliable tool both for phenotyping and to predict resin yield in new stands. The results confirm the high potential for resin tapping in Atlantic maritime pine forests, although tapping should be restricted to stands older than 30 years and a season should be delimited for this activity in the region studied. Additionally, the periodicity of grooves (typically fortnightly) may need to be increased. [ABSTRACT FROM AUTHOR]