Structure and species composition of tree stands on verges and slopes along a major highway in Hong Kong

Arboricultural research focusing on transport land use was lacking in Hong Kong.Some highway slopes were registered in the Systematic Identification of Maintenance Responsibility of Slopes in the Territory(SIMAR),abbreviated as SIMAR slopes.We aimed to analyze patterns in the structure and species composition of the tree stock along a highway in Hong Kong and examined how a slope registration system could help explain the characteristics of urban forests.The 53 slopes and 52 verges along San Tin Highway,Hong Kong were randomly selected.The trees on each slope and verge were collectively sampled as a tree stand.Six variables,namely tree abundance,species richness,maximum tree height,Shannon-Wiener diversity,Simpson's dominance,and Pielou's evenness were measured for each stand.In addition,a limited visual tree risk assessment was performed.The 7,209 trees in 23 species were recorded.Species richness was low,ranging from one to eight species per stand.SIMAR and non-SIMAR slopes were compared.SIMAR slopes had significantly higher species richness,diversity,evenness but lower dominance,with mean difference of 1.41 species,0.17,0.17 and-0.28respectively.SIMAR slopes were associated with lower tree risk rating.When training regression models,boosting as an ensemble method arbitrarily raised the explanatory power and the predictive accuracy of some models.Slope height,length,angle and area could be significant predictors of the biodiversity-related variables.Future research can sample more habitat characteristics related to the structure and species composition of slopes and verges which were important components of urban forestry.

Geophysical and orbital environments of asteroid 4692192016 HO3

Asteroid 469219 Kamo'oalewa,also named 2016 HO3,is a small-size fast-rotating near-Earth asteroid,which is a potential target for future explorations.Owing to its weak gravity and fast spin rate,the dynamics on the surface or in the vicinity of 2016 HO3 are significantly different from those of planets or other small bodies explored in previous missions.In this study,the geophysical and orbital environments of 2016 HO3 were investigated to facilitate a potential mission design.First,the geormnetric and geopotential topographies of 2016 HO3 were examined using difterent shape models.The liftoff and escape conditions on its fast-rotating surface were investigated.Then,the periodic orbits around 2016 HO3 were studied in the asteroid-fixed frame and the Sun-asteroid frame considering the solar radiation pressure.The stable regions of the terminator orbits were discussed using different parameters.Finally,the influence of the nonspherical shape on the terminator orbits was examined.The precise terminator orbits around a real shape model of 2016 HO3 were obtained and verified in the high-fidelity model.This study shows that the polar region of 2016 HO3 is the primary region for landing or sampling,and the terminator orbits are well suited for global mapping and measurements of 2016 HO3.The analysis and methods can also serve as references for the exploration of other small fast-rotating bodies.