Potential Factors behind the Decline of Pinus pinea Nut Production in Mediterranean Pine Forests

Yara El Khoury,Charbel Al Khoury,Nabil Nemer,Elise Noujeim,Eustachio Tarasco,Giovanni Bubici

doi:10.3390/f12091167

Abstract

Mediterranean stone pine nut is appreciated for its high economic and nutritional value. Starting in 2012, Pinus pinea nut production declined throughout the Mediterranean area. The dry cone syndrome associated with this decline and the introduction of Leptoglossus occidentalis occurred simultaneously. This study aims to evaluate potential reasons behind the decline in pine nut production in Lebanon, considering climatic factors and the invasion of L. occidentalis. Correlation analysis was used to examine a potential relationship between cone yield and the percentage of damaged seeds per cone. Climatic variables were also tested. Two time periods were considered for analysis: before and after 2012. Cone production and the percentage of damaged seeds were negatively correlated (r = −0.42). From 2012 to 2017, cone production declined by 50% and the percentage of damaged seeds increased on average from 3% in 2012 up to 60% in 2017. Correlations were detected between cone production and the temperature of the hottest three months of the year of harvesting, and between cone production and average temperatures during the year of cone initiation. A conjunction of factors that include L. occidentalis and climatic factors might have affected the pine nut production in Lebanon.

Highlights

Distributed around the Mediterranean basin and coastal Portugal, stone pine (Pinus pinea L.) occupies a wide range of climatic and soil conditions
Pine nuts are a high-value product in the region, with current retail prices exceeding 100 EUR/kg in Europe [4] and ranging between 35 and 55 EUR/kg in Lebanon [5]
Summary of Pearson correlation between pine cone production climatic variables t—year of harvesting; t-1—one year before the year of harvesting; t-2—two years before harvesting; t-1—one year before the year of harvesting; t-2—two years before the year of harvesting; CM—coldest months the year of harvesting; CM—coldest months in the year of harvesting; CM-1—coldest months one in the year of harvesting; CM-1—coldest year before the year of harvesting; CM-2—coldest months two years year beforemonths the yearone of harvesting; CM-2—coldest months two years before the year of harvesting; before the year of harvesting; HM—hottest months in the year of harvesting; HM-1—hottest months one year before the HM—hottest months in the year of harvesting; HM-1—hottest months one year before the year of harvesting; HM-2—hottest months two years before the year of harvesting

Summary

Introduction

Distributed around the Mediterranean basin and coastal Portugal, stone pine (Pinus pinea L.) occupies a wide range of climatic and soil conditions. Since the Paleolithic era, its edible seeds have been the most economically important non-wood forest product (NWFP) obtained from. Pine nuts are a high-value product in the region, with current retail prices exceeding 100 EUR/kg in Europe [4] and ranging between 35 and 55 EUR/kg (retail price) in Lebanon [5]. In some rain-fed areas (i.e., Mediterranean areas), harvesting pine nuts provides a much higher income in the short term than harvesting wood after long rotations [6,7]. Mediterranean pine forests are threatened by a drought-prone environment, difficult socioeconomic conditions and overexploitation, all of which affect

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Conclusion