Avaliação do potencial de produção do pinheiro manso na região de Mirandela, Trás-os-Montes, Portugal

Abstract

The areas wooded with stone pine (Pinus pinea L.) have increased in recent years due to the yield of the pine nut. So, it is necessary to carry out studies to characterize the crop to apply adequate management and maximize its productivity. This work aims to evaluate the productive potential of stone pine from the perspective of multifunctional forestry in Terra Quente Transmontana. In this context, the production in volume, biomass, and =carbon was evaluated, as well as the production of pine cones and pine nuts and other complementary products of the farm such as mushrooms. The work was carried out in an area of 40 hectares of stone pine with about 25 years old. 5 permanent monitoring plots with 2,500 m² each were installed, 2 plots in conditions without thinning, and 3 plots in conditions with thinning. A forest inventory was carried out with 20 sampling plots of 500 m² each to assist in the characterization of the stone pines production. The dendrometric characterization of the stand was carried out and the other products were quantified (volume of wood, biomass, C storage, pine cones, pine nuts, and mushrooms). Regarding the production of pine cones, the number of cones present in each sampled tree was quantified and 4 cones per tree were sampled for laboratory analysis. Pine cones/ nuts were evaluated by weight, biometric characteristics, and health. Regarding the mushrooms, were considered 3 plots 2,500 m2 in which 2 of them are in a condition without thinning and 1 with thinning. For each plot 3 transects of 50 m² were installed. The number of mushrooms and green weight per species where quantified. The results show a stone pine production in volume of 50.66 m³ha-1 in the no-thinning situation and 24.28 m³ ha-1 in thinning stand. For the total biomass, it was obtained on average 61,239.90 kg ha-1 and 31,229.19 kg ha-1, respectively, in the condition without and with thinning. Regarding total C storage, mean values 30.62 t C ha-1 and 15.61 t C ha-1were obtained, respectively, in the condition without and with thinning. In the monitoring areas, an average green weight per cone of 277.71 g and 2.53% of insect attack and 219,17 g and 2.45% of insect attack was obtained for the 2018/2019 and 2019/2020 harvest, respectively. For the forest inventory plots that cover the entire stand, 237.32 g was obtained in the 2019/2020 harvest. In the monitoring plots, a yield of 2.21% in the white kernel or pine nut was obtained for the 2018/2019 harvest and 2.07% for the 2019/2020 harvest. In turn, the forest inventory plots yielded a kernel yield of 2,09% for the 2019/2020 harvest. In the monitoring plots, in the 2018/2019 harvest, it was necessary, on average, about 3.6 cones to obtain 1 kg of cones having increased to 4.8 cones per kilo in the 2019/2020 harvest. Based on information from the forest inventory plots, approximately 3.57 cones were needed to obtain 1 kg of cones in the 2019/2020 harvest. Regarding mushrooms, five edible species were observed in the monitoring plots without thinning: Lactarius Deliciosus, Russula cyanoxantha, Cantharellus lutescens, Tricholoma sp. and Suillus granulatus. In the thinned area, 3 edible species were observed: Lactarius Deliciosus, Russula cyanoxantha and Cantharellus lutescens. As it is a young stand initially installed for wood production and converted after 20 years to pine production, with a significant reduction in densities due to thinning, its production is not yet maximized due to the short period of reopens to light to induce its formation. The production potential based on the models taken from the reference bibliography shows a high potential for this culture in the Mirandela region.