Regeneration Of Pinus Sylvestris Research Articles

UAV Capability to Detect and Interpret Solar Radiation as a Potential Replacement Method to Hemispherical Photography

Solar radiation is one of the most significant environmental factors that regulates the rate of photosynthesis, and consequently, growth. Light intensity in the forest can vary both spatially and temporally, so precise assessment of canopy and potential solar radiation can significantly influence the success of forest management actions, for example, the establishment of natural regeneration. In this case study, we investigated the possibilities and perspectives of close-range photogrammetric approaches for modeling the amount of potential direct and diffuse solar radiation during the growing seasons (spring–summer), by comparing the performance of low-cost Unmanned Aerial Vehicle (UAV) RGB imagery vs. Hemispherical Photography (HP). Characterization of the solar environment based on hemispherical photography has already been widely used in botany and ecology for a few decades, while the UAV method is relatively new. Also, we compared the importance of several components of potential solar irradiation and their impact on the regeneration of Pinus sylvestris L. For this purpose, a circular fisheye objective was used to obtain hemispherical images to assess sky openness and direct/diffuse photosynthetically active flux density under canopy average for the growing season. Concerning the UAV, a Canopy Height Model (CHM) was constructed based on Structure from Motion (SfM) algorithms using Photoscan professional. Different layers such as potential direct and diffuse radiation, direct duration, etc., were extracted from CHM using ArcGIS 10.3.1 (Esri: California, CA, USA). A zonal statistics tool was used in order to extract the digital data in tree positions and, subsequently, the correlation between potential solar radiation layers and the number of seedlings was evaluated. The results of this study showed that there is a high relation between the two used approaches (HP and UAV) with R2 = 0.74. Finally, potential diffuse solar radiation derived from both methods had the highest significant relation (−8.06% bias) and highest impact in the modeling of pine regeneration.

Optimum timing of soil scarification for the natural regeneration of Pinus sylvestris in Central Sweden

In an attempt to identify the optimal time for soil scarification to promote the natural regeneration of Pinus sylvestris L. (Scots pine), scarification was applied at various times in two pine shelterwood stands, from autumn 2005 to spring 2006 in one and from autumn 2006 to spring 2008 in the other. Each year, seed fall was monitored from April to July and numbers of emerged seedlings were counted at the end of the vegetation period. The number of emerged seedlings was closely related to the proportion of unshed seeds remaining in the cones at the time of each scarification event. A significant difference was observed in seedling establishment between scarification in the autumn and the following late spring, but not between scarification in autumn and early spring. Both the level of seed production and the timing of scarification in relation to seed fall proved to be important determinants of seedling densities, but during 2008 a promising seed fall did not result in good seedling establishment (regardless of scarification timing) because of drought. We conclude that the optimum timing of soil scarification for regenerating Scots pine in central Sweden is before the seed fall begins, from autumn through to mid-April (early spring).

Regeneration of Pinus sylvestris in a natural pinewood in NE Scotland following reduction in grazing by Cervus elaphus

The occurrence of Scots pine ( Pinus sylvestris L.) seedlings and saplings (<2.0 m in height and suppressed by grazing) and ground characteristics were recorded in a 300 ha block of natural pine forest in 1993. The density of red deer ( Cervus elaphus L.) was then reduced by exclosure to approximately 3–4 deer km −2, which is below the threshold at which pine regeneration should occur. Numbers and performance of pine seedlings and saplings were further monitored 2 and 4 years after exclosure. Numbers of young pine increased over time. In the three years with observations 97–99% of pine seedlings and saplings were recorded within 20 m of a seed source. Stepwise multiple regression was used to explore the relationships of pine establishment with plot characteristics for (a) all observation plots ( n = 178) and (b) plots within 20 m of a seed source ( n = 154). The factors most closely related to the number of pine seedlings and saplings in 1997 were, for (a), seed–source distance, vegetation height, blaeberry cover, slope and deer pellet-group density in 1993, all but the last having negative effects. For (b), vegetation height, blaeberry cover and slope were again selected predictors, and again had negative effects. Possible mechanisms by which the selected main effects may influence pine regeneration are discussed, the positive relationship to deer density being considered to reflect the creation of gaps in the sward suitable for germination. However, the amounts of variation explained in the models were low, being 16% for (a) and 13% for (b), reflecting the patchy nature and diverse age of the regeneration.