Plant Ecological Strategies: Some Leading Dimensions of Variation Between Species

Abstract

An important aim of plant ecology is to identify leading dimensions of ecological variation among species and to understand the basis for them. Dimensions that can readily be measured would be especially useful, because they might offer a path towards improved worldwide synthesis across the thousands of field experiments and ecophysiological studies that use just a few species each. Four dimensions are reviewed here. The leaf mass per area-leaf lifespan (LMA-LL) dimension expresses slow turnover of plant parts (at high LMA and long LL), long nutrient residence times, and slow response to favorable growth conditions. The seed mass-seed output (SM-SO) dimension is an important predictor of dispersal to establishment opportunities (seed output) and of establishment success in the face of hazards (seed mass). The LMA-LL and SM-SO dimensions are each underpinned by a single, comprehensible tradeoff, and their consequences are fairly well understood. The leaf size-twig size (LS-TS) spectrum has obvious consequences for the texture of canopies, but the costs and benefits of large versus small leaf and twig size are poorly understood. The height dimension has universally been seen as ecologically important and included in ecological strategy schemes. Nevertheless, height includes several tradeoffs and adaptive elements, which ideally should be treated separately. Each of these four dimensions varies at the scales of climate zones and of site types within landscapes. This variation can be interpreted as adaptation to the physical environment. Each dimension also varies widely among coexisting species. Most likely this within-site variation arises because the ecological opportunities for each species depend strongly on which other species are present, in other words, because the set of species at a site is a stable mixture of strategies.

Plant functional traits have globally consistent effects on competition

“…No benefit of dissimilarity was detected for specific leaf area or wood density, and only a weak benefit for maximum height. Our traitbased approach to modelling competition makes generalization possible across the forest ecosystems of the world and their highly diverse species composition.Phenotypic traits are considered fundamental drivers of community assembly and thus species diversity 1,6 . The effects of traits on individual plant physiologies and functions are increasingly understood, and have been shown to be underpinned by well-known and globally consistent trade-offs 1-3 .…”

“…Phenotypic traits and their associated trade-offs have been shown to have globally consistent effects on individual plant physiological functions [1][2][3] , but how these effects scale up to influence competition, a key driver of community assembly in terrestrial vegetation, has remained unclear 4 . Here we use growth data from more than 3 million trees in over 140,000 plots across the world to show how three key functional traits-wood density, specific leaf area and maximum height-consistently influence competitive interactions.…”

Nearly 200 years of sustained selection have not overcome the leaf area–stem size relationship in the poinsettia

“…The leaf area–stem size relation is nearly pervasive, being found across virtually all species that have been studied (Ackerly, 1996; Ackerly & Donoghue, 1998; Leslie et al., 2014; Sun et al., 2006; Westoby et al., 2002; White, 1983a,b; Wright et al., 2006). The only exceptions seem to be certain plants in warm drylands, which have greatly reduced leaf area for a given stem size (Eggli, 2002).…”

“…This pattern, known as Corner's rules, is pervasive, having been documented across virtually all flowering plant lineages, on multiple continents, in vastly differing vegetation types and climates (Ackerly, 1996; Ackerly & Donoghue, 1998; White, 1983a). Corner's rules state that plants with large leaves have thick twigs and branch sparingly; plants with small leaves have thin twigs that branch intricately (Leslie, Beaulieu, Crane, & Donoghue, 2014; Sun, Jin, & Shi, 2006; Westoby, Falster, Moles, Vesk, & Wright, 2002; White, 1983b; Wright, Falster, Pickup, & Westoby, 2006). What causes Corner's rules is actively being elucidated (Smith, Sperry, & Adler, 2017), and documenting how plants fill leaf area–stem size space is essential in this effort.…”

The role of breeding system in community dynamics: Growth and mortality in forests of different successional stages

“…In terms of understanding the multiple traits driving successional differences, seed mass, leaf mass per area, woody density, and maximum height of trees received a great deal of attention (Westoby et al. 2002, Westoby & Wright 2006; Poorter et al., 2008; Chave et al. 2009; Norden, Letcher, Boukili, Swenson, & Chazdon, 2012; Buzzard, Hulshof, Birt, Violle, & Enquist, 2016).…”