Visions of treescapes and services from trees

It is increasingly the case that we seek to understand better what ecosystem services are delivered by trees, and indeed, how they do this. In some cases this means that we require a better or more precise understanding of the parameters which constitute a “tree” such as leaf area. The paper by Madalena Vaz Monteiro and colleagues (Monteiro, Doick, Lawrence, & Wilson, 2018) looks at the application of hemispherical photography to estimate total leaf canopy for mature trees in urban environments. The approach has long since been used by woodland ecologists, although some of us go back far enough to recall the actual figures being derived from manually produced hemispherical graph-paper! In the urban context, the methods seemed to give a good estimate in comparison with other approaches though the variance increased with tree size. Research such as this helps develop a more complete and rounded assessment of the structure and functions of urban trees.

Also considering tree functions, Slater’s study on natural tree bracing and bark included junctions (Slater, 2018) is reported here as part of a series of papers on this and related themes by Slater and colleagues. Duncan notes that a factor influencing the mechanical loading of a junction is the presence of “crossing or touching limbs” situated above a junction and acting as a “natural brace”. These structures straddle the join and so restrict the natural movement of both junction and associated limbs. The outputs of these long-term programmes of research demonstrate direct relevance of meticulous, focused studies to tree practitioners in the field.

Formerly of English Nature and then Natural England, Keith Kirby has been involved with and even leading policy developments in relation to many aspects of UK trees and woods over many years. In this paper (Kirby, 2018), Keith challenges some perceptions and assumptions of nature conservation. He addresses issues of trees and treescapes, and argues that conservation approaches have not always evolved to take into account new information and thinking around landscape ecology, and past influences of humans on the countryside. He notes that climate change, emerging tree diseases and new forms of public discussion via social media, all influence the emerging priorities. Furthermore, he suggests that Britain leaving the European Union may provide an opportunity to bring some of these new ideas into conservation policy and through this to influence evolving support mechanisms for practical delivery of work on the ground.

Finally, Sjöman, Hirons, and Bassuk (2018) examine the drought tolerance of magnolias in urban situations. The genus Magnolia includes 224 species with both deciduous and evergreen trees and shrubs. The larger shrubs and smaller trees are increasingly important in urban landscapes but there may be issues of drought-related impacts for species whose natural environment is relatively humid. This paper is an important contribution to discussions on the suitability of various Magnolia species for drier, urban situations.

Ian D. Rotherham
Editor, Arboricultural Journal
[email protected]