Does Slope Aspect Affect the Aboveground Tree Shape and Volume Allometry of European Beech (Fagus sylvatica L.) Trees?

Abstract

In mountainous or hilly areas, the slope aspect affects the amount of solar radiation, with direct consequences on species distribution and tree growth. However, little is known on how the tree shape and volume allometry may be affected by contrasting environmental conditions driven by the slope aspect. This study aims to investigate whether the slope aspect affects the aboveground tree shape and volume allometry of European beech (Fagus sylvatica L.) trees. We used the data of scanned trees from two plots located on south- and respectively north-facing slopes and, additionally, an inventory dataset containing measurements of diameter at breast height (D) and tree height (H). To investigate the differences in tree shape, we used analysis of covariance. However, to assess the differences in volume allometry, we first predicted the volume of each individual tree within the inventory dataset using either the south- or the north-facing slope volume model, and then performed a paired t-test on the plot estimates based on the two volume models. Since the uncertainty originating from allometric volume model predictions was likely to affect the results of the paired t-test, we performed a Monte-Carlo simulation to assess the rate of null hypothesis acceptance with the paired t-test. The results showed that trees growing on the north-facing slope were significantly thinner (p < 0.001), with a significantly longer branching system (p < 0.001) compared to those on the south-facing slope. Correspondingly, the volume estimates per unit of forest area based on the south- vs. north-facing slope allometric volume models were significantly different (p < 0.001). The estimates of total aboveground volume per unit of forest area based on the north-facing slope allometric models were significantly larger compared to those based on the south-facing slope volume models, a difference driven by the significantly larger branch and stem volume for the north-facing slope. These differences in estimates per unit of forest area were larger when based on allometric models that only used D as a predictor of aboveground tree volume. The rates of null hypothesis acceptance within the paired t-test were generally low. For total aboveground volume estimated by D and H, the acceptance rate was 1.79%. Nevertheless, only using D to predict tree volume, the rates of null hypothesis acceptance were lower (i.e., 0.1%), suggesting that addition of H as a predictor of tree volume partly explains the differences caused by the slope aspect on volume allometry, but not enough to offset the differences entirely. In conclusion, slope aspect has significantly affected the tree shape and volume allometry of European beech trees.

Growth characteristics of Cunninghamia lanceolata in China

“…The R 2 value (R 2 = 0.9833, p < 0.05) for our national-scale two-variable volume equation was similar to other local scale volume equations reported by Li 21 (R 2 = 0.9820), Zeng et al 23 (R 2 = 0.9994), and Xia et al 24 (R 2 = 0.9868). Models that incorporate DBH and height usually give good-fits 43 – 46 . Although the best-fit model to estimate stem wood volume was a two-variable volume equation (Table 3 ), in some cases, this two-variable model is not practical because the measurements of these variables are difficult to carry out with high accuracy, particularly in closed forests 47 .…”

Impact of Transhumant Livestock Grazing Abandonment on Pseudo-Alpine Grasslands in Greece in the Context of Climatic Change

“…Lundbäck and coauthors [105] estimate that 82% of the world's forests grow on slopes <15 • . The amount of solar radiation in mountainous or hilly environments is impacted by the slope aspect, which has an immediate impact on species distribution and tree growth [106]. At mid-latitudes in the Northern Hemisphere, south-facing slopes receive significantly more direct solar radiation than comparable northern slopes [107].…”