I want to be… a tree!

In trying to encourage my students to consider the structure–function issues in being a land plant, I often joke that all plants really want to be trees when they grow up, to command resources, shade-out competition, etc. And you can – almost – believe it is true; after all, ferns aspire to be trees, monocots crave arborescence, cycads are wannabe giant redwoods, and even the grasses contain bamboos. And why not? This life form is the ultimate demonstration of the lofty heights that can be scaled by self-supporting biological structures using the most basic of ‘ingredients’ (tallest extant tree – allegedly – is a coast redwood, Sequoia sempervirens, at 115.56 m). And, arguably, trees represent the longest-lived living thing on the planet – 9554 years for a Norway spruce in Sweden. And it’s no accident that the whole of creation is envisaged as branches on the TREE of life. Well, another boost to aspiration of the lifestyle ligneous – if it were needed – is provided by Stagoll et al., who underline the importance of large trees as ‘keystone structures’ in urban parks in providing ‘crucial habitat resources for wildlife’, especially birds. Keystone structures are ‘distinct spatial structures providing resources, shelter or “goods and services” crucial for other species’, and are distinct from the more familiar concept of keystone species. This research emphasises the ecosystem services’ role of trees and extends a previous study by three of the present paper’s co-authors on the keystone role of trees in less urban – but equally human-managed – environments. Viewing trees in this way also makes the important point that even a dead structure can play an important role in ecology; what better legacy for a life? Which leads on to your end-of-year Botany Exam question: ‘Trees contribute more in death than when alive. Discuss’. [I’m so glad that Mr P. Cuttings resisted the temptation to ask: ‘What did Mack Sennett call a small group of trees? Answer: A keystone copse’ – Ed.)