Mapping tree canopies in urban environments using airborne laser scanning (ALS):a Vancouver case study

Background: The distribution of forest vegetation within urban environments is critically important as it influences urban environmental conditions and the energy exchange through the absorption of solar radiation and modulation of evapotranspiration. It also plays an important role filtering urban water systems and reducing storm water runoff.Methods: We investigate the capacity of ALS data to individually detect, map and characterize large(taller than15 m) trees within the City of Vancouver. Large trees are critical for the function and character of Vancouver’s urban forest. We used an object-based approach for individual tree detection and segmentation to determine tree locations(position of the stem), to delineate the shape of the crowns and to categorize the latter either as coniferous or deciduous.Results: Results indicate a detection rate of 76.6% for trees > 15 m with a positioning error of 2.11 m(stem location). Extracted tree heights possessed a RMSE of 2.60 m and a bias of-1.87 m, whereas crown diameter was derived with a RMSE of 3.85 m and a bias of-2.06 m. Missed trees are principally a result of undetected treetops occurring in dense, overlapping canopies with more accurate detection and delineation of trees in open areas.Conclusion: By identifying key structural trees across Vancouver’s urban forests, we can better understand their role in providing ecosystem goods and services for city residents.

Synergistic effects of tropical cyclones on forest ecosystems:a global synthesis

Tropical cyclones are large-scale strong wind disturbance events that occur frequently in tropical and subtropical coastal regions and often bring catastrophic physical destruction to ecosystems and economic disruption to societies along their paths. Major tropical cyclones can infrequently move into the midaltitudes and inland areas. Ecologically, tropical cyclones have profound impacts on diversity, structure, succession and function of forest ecosystems. The ecological effects are both dramatic and subtle. The dramatic effects can be visible, noticeable and to some extent predictable over the short-term and relatively well documented in the literature. However, the subtle effects are often invisible, complex and at smaller scale relatively unpredictable in the long-term. Many factors, meteorologic, topographic and biologic, simultaneously interact to influence the complexity of patterns of damage and dynamics of recovery. I present a global synthesis on the effects of tropical cyclones on forest ecosystems and the complexity of forest responses, with particular attention on the response to large hurricanes in the neotropics and the temperate North America, and strong typhoons on the subtropical and temperate forests in the East and Southeast Asia. Four major aspects provide on organizational framework for this synthesis：（1） consistent damage patterns,（2） factors that influence response patterns and predict damage risks,（3） complexity of forest responses and recovery, and（4） the long-term effects. This review reveals highly variable and complex effects of tropical cyclones on forest ecosystems. A deep understanding of the synergistic effects of tropical cyclones is essential for effective forest management and biodiversity conservation.

Stand structure and species diversity regulate biomass carbon stock under major Central Himalayan forest types of India

Background:Data on the impact of species diversity on biomass in the Central Himalayas,along with stand structural attributes is sparse and inconsistent.Moreover,few studies in the region have related population structure and the influence of large trees on biomass.Such data is crucial for maintaining Himalayan biodiversity and carbon stock.Therefore,we investigated these relationships in major Central Himalayan forest types using nondestructive methodologies to determine key factors and underlying mechanisms.Results:Tropical Shorea robusta dominant forest has the highest total biomass density(1280.79 Mg ha^(−1))and total carbon density(577.77 Mg C ha^(−1))along with the highest total species richness(21 species).The stem density ranged between 153 and 457 trees ha^(−1) with large trees(>70 cm diameter)contributing 0–22%.Conifer dominant forest types had higher median diameter and Cedrus deodara forest had the highest growing stock(718.87 m^(3) ha^(−1));furthermore,C.deodara contributed maximally toward total carbon density(14.6%)among all the 53 species combined.Quercus semecarpifolia–Rhododendron arboreum association forest had the highest total basal area(94.75 m^(2) ha^(−1)).We found large trees to contribute up to 65%of the growing stock.Nine percent of the species contributed more than 50%of the carbon stock.Species dominance regulated the growing stock significantly(R^(2)=0.707,p<0.001).Temperate forest types had heterogeneous biomass distribution within the forest stands.We found total basal area,large tree density,maximum diameter,species richness,and species diversity as the predominant variables with a significant positive influence on biomass carbon stock.Both structural attributes and diversity influenced the ordination of study sites under PCA analysis.Elevation showed no significant correlation with either biomass or species diversity components.Conclusions:The results suggest biomass hyperdominance with both selection effects and niche complementarity to play a complex mechanism in enhancing Central Himalayan biomass carbon stock.Major climax forests are in an alarming state regarding future carbon security.Large trees and selective species act as key regulators of biomass stocks;however,species diversity also has a positive influence and should also reflect under management implications.

Towards more-than-human heritage:arboreal habitats as a challenge for heritage preservation

Trees belong to humanity’s heritage,but they are more than that.Their loss,through catastrophic fires or under business-as-usual,is devastating to many forms of life.Moved by this fact,we begin with an assertion that heritage can have an active role in the design of future places.Written from within the field of architecture,this article focuses on structures that house life.Habitat features of trees and artificial replacement habitats for arboreal wildlife serve as concrete examples.Designs of such habitats need to reflect behaviours,traditions and cultures of birds,bats,and other animals.Our narrative highlights the nonhuman aspect of heritage,seeking to understand how nonhuman stakeholders can act as users and consumers of heritage and not only as its constituents.Our working definition states that more-than-human heritage encompasses tangible and intangible outcomes of historical processes that are of value to human as well as nonhuman stakeholders.From this basis,the article asks how the established notions of heritage can extend to include nonhuman concerns,artefacts,behaviours and cultures.As a possible answer to this question,the hypothesis tested here is that digital information can(1)contribute to the preservation of more-than-human heritage;and(2)illuminate its characteristics for future study and use.This article assesses the potential of three imaging technologies and considers the resulting data within the conceptual framework of more-than-human heritage,illuminating some of its concrete aspects and challenges.