Freezing and Heating Tolerance of Pinus nigra Seedlings from Three South to North Balkan Provenances

Abstract

To meet the restoration and reforestation goals in the changing environment, the translocation of genotypes and species northward and upward need to be considered to a great extent. Pinus nigra is a genetically diverse, drought sensitive species, with cold hardiness comparable to other tree species under the same climatic conditions. This study tested frost hardiness (whole plant freezing test—WPFT, and electric conductivity—EC test), and heat tolerance (heat tolerance test) of P. nigra seedlings from two southern Greek provenances (Kalamata and Grevena) and one northern Serbian provenance (Šargan) to better understand the potential of seed transfer from the south to the north of the species distribution in the Balkan peninsula. The results showed that, that for all studied provenances, the damage was great; the index of injury (Ii) at −18 °C was ranged from 49 to 54.5 (measured by the EC method) and the percentage of injured tissues ranged from 80–90% (measured by visual observation). For all studied provenances, a sharp increase in damages was observed with the fall of temperature from −5 and −18 °C and the time after exposure. The WPFT results showed that the highest tolerance to freezing (−18 °C) was presented by seedlings from the northern (Šargan) provenance; however, no significant differences were statistically detected among the studied provenances. The heat and drought-treated seedlings, from both provenances, presented significantly highler foliar damages than only drought-treated ones. For seedlings from both contrasting provenances (Grevena and Šargan), exposure to moderate heat (45 °C) and short drought did present damages but without significant difference between them. Considering freezing and heating tolerance, Greek provenances of P. nigra (i.e., Grevena region) can be successfully used in Serbian forestation and restoration programs. The present study makes a contribution towards P. nigra reforestation with practical implications for abiotic stress (frost, heat drought) tolerance among southern and northern provenances and could be valuable to determine the suitable provenances for reforestation programs and assisted population migration under climatic change scenarios.

Evaluation of Different Geographic Provenances of Silver Fir (Abies alba) as Seed Sources, Based on Seed Traits and Germination

“…Several studies have demonstrated that using sulfuric acid was more effective than other treatments for different forest species [47,57,65]. To break the seed dormancy, the tegument must be deteriorated; in natural conditions, this 'damage' occurs as a result of the action of many elements on the seed tegument, such as low temperatures (frosts), high temperatures (fires), and so on [45,46]. The scarification of the silver fir seeds failed to produce a high percentage of germination in our experimental conditions, but, in contrast, Atonik, a biostimulator used to stimulate both seed germination and seedling rooting [50], significantly improved the germination for all the silver fir provenances.…”

“…To break seed dormancy, different physical or chemical stimuli act on the seeds, or the seed integument must be damaged; in natural conditions, this damage occurs due to the action of different factors, such as low temperatures (frosts), high temperatures (fires) [45,46]. Currently, different methods are used to scarify the seeds, the mechanical scarification method being one of the most used [47][48][49].…”