Effects of sand burial and overstory tree age on seedling establishment in coastal Pinus thunbergii forests in the northern Shandong Peninsula, China

Abstract

Coastal Pinus thunbergii (Japanese black pine) forests in the northern Shandong Peninsula of China recently experienced widespread natural regeneration failure. This study identifies critical factors that affect natural regeneration of P. thunbergii. Seeds from trees of various ages (13-32 years) were used to investigate the effects of age and burial depth in sand on germination and seedling establishment. Results show that seed density in 2-5 cm soil decreased with increased distance from the shoreline. Sand burial decreased seed germination but did not affect the relative growth rate of seedlings at depths from 0.5 to 3 cm. Germination, leaf mass ratio, and relative growth rates were higher with seedlings originating from older trees, all of which enhanced seedling resistance to sand burial. Tree age and seed burial were found to be determining factors for natural regeneration of the coastal P. thunbergii forest. Silvicultural treatments that promote quality of seed sources and mitigation of sand burial can be used in the future to improve the regeneration of these coastal forests.Keywords: coastal forest, seed germination, biomass allocation, relative growth rate, seedling establishment RÉSUMÉ Les forêts côtières de Pinus thunbergii (pin noir du Japon) situées dans la péninsule septentrionale de du Shandong ont affiché été victimes dernièrementrécemment d'importants échecs de la régénération naturelle. Cette étude identifie les facteurs déterminants les plus importants qui affectent de la régénération naturelle du P. thunbergii. On a utilisé desLes semences provenant d'arbres de différents âges (13-32 ans) ont été utilisées dans le but de dpour ' étudier les effets de l'âge et de la profondeur de l' ensevelissement l' enfouissement dans le sable sur la germination et l' établissement des semis. Les résultats indiquent que la densité de semences par dans 2 à 5 5 cm de sol diminuait avec l'accroissement une augmentation de la distance par rapport au du rivage. L' ensevelissement dans le sable a réduit le taux de germination, mais n'a pas eu d' effet sur le taux relatif de croissance des semis retrouvés entre 0,5 et 3 3 cm. La germination, le ratio de masse foliairefeuillage/masse et les taux relatifs de croissance ont été plus élevés dans le cas des semis provenant d'arbres plus âgés, tous contribuant à accroître la résistance des semis à l' ensevelissement l' enfouissement dans le sable. Il s' est avéré que lL'âge des arbres et l' ensevelissement l' enfouissement des semences avaient une influence déterminante sur ont été identifiés comme étant les facteurs déterminants de la régénération naturelle des forêts de P. thunbergii. Les traitements sylvicoles qui favorisent la qualité des sources de semences et l'atténuation de l' enfouisevelissement dans le sable pourront être utilisés à l'avenir peuvent être utilisés dans l'avenir pour améliorer la régénération de ces forêts côtières.

Effects of Seed Size and Sand Burial on Germination and Early Growth of Seedlings for Coastal Pinus thunbergii Parl. in the Northern Shandong Peninsula, China

“…Much research has been conducted on natural regeneration of the P. thunbergii protection forests. In particular, the effects of seed tree age and salt stress [7], water stress [8], and sand burial [9] on seed germination have been systematically studied. One of the important findings from these studies is that seed tree age played an important role in the seed germination of P. thunbergii.…”

“…Baraloto et al [16] showed that seed size influenced performance within and among eight neotropical tree species. A short germination time can cause P. thunbergii seedlings to have a longer growth time and larger individuals, which is vital for seedling establishment in the natural environment [9]. Larger seeds have more nutrients, which can improve the germination and seedling tolerance of Caragana microphylla Lam.…”

“…Sand burial depth has an obvious effect on seed germination rate and germination time [9,17]. Burial at an appropriate depth stimulates seed germination more so than if seeds were placed on the soil surface [18,[21][22][23] due to the moist environment [24].…”

Sandy Habitats Play an Important Role in Shrub Encroachment in Grasslands

“…The bare land outside the shrub area is subjected to wind erosion, while the shrub area is frequently partially or completely buried by sand (Figure 5d). Some studies have shown that moderate burial improved seed germination, seedling survival and the growth of herbaceous plants, such as Psammochloa villosa [35], Leymus secalinus [15], as well as of desert shrubs, such as Nitraria sphaerocarpa and Haloxylon ammodendron [7], while others also found that seed germination of Eremosparton songoricum [14] and Pinus thunbergii [36] decreased after shallow partial burial treatment. We found that the seed germination and seedling biomass of Caragana reached the highest level at a sand burial depth of 1-2 cm.…”