Development of Crown Ratio and Height to Crown Base Models for Masson Pine in Southern China

Abstract

Crown ratio (CR) and height to crown base (HCB) are important crown characteristics influencing the behavior of forest canopy fires. However, the labor-intensive and costly measurement of CR and HCB have hindered their wide application to forest fire management. Here, we use 301 sample trees collected in 11 provinces in China to produce predictive models of CR and HCB for Masson pine forests (Pinus massoniana Lamb.), which are vulnerable to forest canopy fires. We first identified the best basic model that used only diameter at breast height (DBH) and height (H) as independent variables to predict CR and HCB, respectively, from 11 of the most used potential candidate models. Second, we introduced other covariates into the best basic model of CR and HCB and developed the final CR and HCB predictive models after evaluating the model performance of different combinations of covariates. The results showed that the Richards form of the candidate models performed best in predicting CR and HCB. The final CR model included DBH, H, DBH0.5 and height-to-diameter ratio (HDR), while the final HCB model was the best basic model (i.e., it did not contain any other covariates). We hope that our CR and HCB predictive models contribute to the forest crown fire management of Masson pine forests.

Detecting Individual Tree Attributes and Multispectral Indices Using Unmanned Aerial Vehicles: Applications in a Pine Clonal Orchard

“…Usually, these conjugated variables are essential for the subsequent estimation of volume, biomass, and carbon stocks, so that their proper measurement has a direct impact on the quantification of inventories and thus on decision making [10]. On the other hand, measurements of tree-crown dimensions are important because the tree crown is where trees interact with their surrounding environment, including via diverse physiological processes such as photosynthesis and respiration; consequently, its accurate quantification is crucial to designing strategies of cultural labors on the individual-tree level [11].…”

Height to Crown Base Modelling for the Main Tree Species in an Even-Aged Pedunculate Oak Forest

“…The variability of hcb has been evaluated through three groups of variables: (1) tree size metrics referred to as treelevel variables, (2) variables of the size and vigour of the plot or stand denominated as plot-level variables, and (3) variables of the site quality and distance-independent competition indexes. For instance, the dominant height is usually used to describe the site quality and the stand development age, since it is strongly correlated with the growth condition of the dominant trees (Fu et al 2017, Li et al 2020, Pan et al 2020, and the total basal area of all trees with a diameter larger than the target tree is usually used to assess competition effects (Fu et al 2017). These variables have been used combined or separately in many studies (Rijal et al 2012, Fu et al 2017, Pan et al 2020.…”

“…As final variables, tree size measures and the spacing index were selected. Li et al (2020) worked with Pinus massoniana in Southern China, obtaining an 88.03% R 2 adj by applying logistic equations in hcb modelling with ht and dbh as predictive variables.…”

“…Therefore, these metrics are critically important for informing forest management (Li et al 2020). However, crown measurements require an appropriate abstraction of crown size and shape; however, direct measurement of the crown shape or profile is difficult (Cameron et al 12(1): early view 2020).…”

Live Crown Ratio Models for Loblolly Pine (Pinus taeda) with Beta Regression

“…For example, the height to base of a live crown, a variable algebraically related to LCR, is a critical factor in modeling fire behavior, as it relates to the rate of spread of a crown fire. Additionally, smaller heights to the base of live crowns (i.e., larger crown ratios) are associated with an increased risk of crown fires developing from surface fires [13].…”