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.

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Plant Ecological Strategies: Some Leading Dimensions of Variation Between Species

Wood performs several essential functions in plants, including mechanically supporting aboveground tissue, storing water and other resources, and transporting sap. Woody tissues are likely to face physiological, structural and defensive trade-offs. How a plant optimizes among these competing functions can have major ecological implications, which have been under-appreciated by ecologists compared to the focus they have given to leaf function. To draw together our current understanding of wood function, we identify and collate data on the major wood functional traits, including the largest wood density database to date (8412 taxa), mechanical strength measures and anatomical features, as well as clade-specific features such as secondary chemistry. We then show how wood traits are related to one another, highlighting functional trade-offs, and to ecological and demographic plant features (growth form, growth rate, latitude, ecological setting). We suggest that, similar to the manifold that tree species leaf traits cluster around the 'leaf economics spectrum', a similar 'wood economics spectrum' may be defined. We then discuss the biogeography, evolution and biogeochemistry of the spectrum, and conclude by pointing out the major gaps in our current knowledge of wood functional traits.

Towards a worldwide wood economics spectrum

Summary 1. The leaf economics spectrum (LES) provides a useful framework for examining species strategies as shaped by their evolutionary history. However, that spectrum, as originally described, involved only two key resources (carbon and nutrients) and one of three economically important plant organs. Herein, I evaluate whether the economics spectrum idea can be broadly extended to water – the third key resource –stems, roots and entire plants and to individual, community and ecosystem scales. My overarching hypothesis is that strong selection along trait trade-off axes, in tandem with biophysical constraints, results in convergence for any taxon on a uniformly fast, medium or slow strategy (i.e. rates of resource acquisition and processing) for all organs and all resources. 2. Evidence for economic trait spectra exists for stems and roots as well as leaves, and for traits related to water as well as carbon and nutrients. These apply generally within and across scales (within and across communities, climate zones, biomes and lineages). 3. There are linkages across organs and coupling among resources, resulting in an integrated whole-plant economics spectrum. Species capable of moving water rapidly have low tissue density, short tissue life span and high rates of resource acquisition and flux at organ and individual scales. The reverse is true for species with the slow strategy. Different traits may be important in different conditions, but as being fast in one respect generally requires being fast in others, being fast or slow is a general feature of species. 4. Economic traits influence performance and fitness consistent with trait-based theory about underlying adaptive mechanisms. Traits help explain differences in growth and survival across resource gradients and thus help explain the distribution of species and the assembly of communities across light, water and nutrient gradients. Traits scale up – fast traits are associated with faster rates of ecosystem processes such as decomposition or primary productivity, and slow traits with slow process rates. 5. Synthesis. Traits matter. A single ‘fast–slow’ plant economics spectrum that integrates across leaves, stems and roots is a key feature of the plant universe and helps to explain individual ecological strategies, community assembly processes and the functioning of ecosystems.

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The world‐wide ‘fast–slow’ plant economics spectrum: a traits manifesto

Early flowering plants are thought to have been woody species restricted to warm habitats 1–3 . This lineage has since radiated into almost every climate, with manifold growth forms 4 . As angiosperms spread and climate changed, they evolved mechanisms to cope with episodic freezing. To explore the evolution of traits underpinning the ability to persist in freezing conditions, we assembled a large species-level database of growth habit (woody or herbaceous; 49,064 species), as well as leaf phenology (evergreen or deciduous), diameter of hydraulic conduits (that is, xylem vessels and tracheids) and climate occupancies (exposure to freezing). To model the evolution of species’ traits and climate occupancies, we combined these data with an unparalleled dated molecular phylogeny (32,223 species) for land plants. Here we show that woody clades successfully move di nto freezingprone environments by either possessing transport networks of small

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Three keys to the radiation of angiosperms into freezing environments

The tissue traits and architectures of plant species are important for land-plant ecology in two ways. First, they control ecosystem processes and define habitat and resources for other taxa; thus, they are a high priority for understanding the ecosystem at a site. Second, knowledge of trait costs and benefits offers the most promising path to understanding how vegetation properties change along physical geography gradients. There exists an informal shortlist of plant traits that are thought to be most informative. Here, we summarize recent research on correlations and tradeoffs surrounding some traits that are prospects for the shortlist. By extending the list and by developing better models for how traits influence species distributions and interactions, a strong foundation of basic ecology can be established, with many practical applications.

http://bio.mq.edu.au/~iwright/pdfs/westoby06tree.pdf

Land-plant ecology on the basis of functional traits

Pieter Baas – Leiden, The Netherlands Nadezhda Blokhina – Vladivostok, Russia Tomoyuki Fujii – Ibaraki, Japan Peter Gasson – Kew, UK Dietger Grosser – Munich, Germany Immo Heinz – Munich, Germany Jugo Ilic – South Clayton, Australia Jiang Xiaomei – Beijing, China Regis Miller – Madison, WI, USA Lee Ann Newsom – University Park, PA, USA Shuichi Noshiro – Ibaraki, Japan Hans Georg Richter – Hamburg, Germany Mitsuo Suzuki – Sendai, Japan Teresa Terrazas – Montecillo, Mexico Elisabeth Wheeler – Raleigh, NC, USA Alex Wiedenhoeft – Madison, WI, USA

IAWA list of microscopic features for softwood identification

IAWA list of microscopic features for hardwood identification : with an appendix on non-anatomical information

Inside Wood is an Internet-accessible wood anatomy reference, research, and teaching tool. The InsideWood database has coded wood anatomical descriptions based on the IAWA List of Microscopic Features for Hardwood Identification and is accompanied by a collection of photomicrographs. As of November 2010 there were over 5,800 descriptions and 36,000 images of modern woods, and over 1,600 descriptions and 2,000 images of fossil woods. CITES-listed timber species and other endangered woody plants are included in this digital collection hosted by North Carolina State University’s library. This web site has value in helping with wood identification because it has a multiple entry key that allows searching by presence or absence of IAWA features and it serves as a virtual reference collection whereby descriptions and images can be retrieved by searching by scientific or common name or other keywords.

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Inside Wood – A Web resource for hardwood anatomy

Data on fossil dicotyledonous wood were assembled in order to 1) test the Baileyan model for trends of specialisation in dicotyledonous wood anatomy by addressing the question - were 'primitive' wood anatomieal features (as defined by the Baileyan model) more common in the geologie past than at present?, 2) infer, on a broad geographie scale, past climatie regimes, and long term climatic change, and 3) assess the extent of knowledge of fossil dicotyledonous woods The resulting database has information on 91 anatomieal features for over 1200 fossil dicotyledonous woods The incidence of selected anatomical features was plotted through time (by geologie epoch) for the world and for two regional groupings (roughly corresponding to the Laurasian and Gondwanan supercontinents) For comparison to the fossil wood record, the incidence of wood anatomie al features in the Recent flora was obtained from the 5260 record OPCN database for extant dicotyledonous woods

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A Survey of the Fossil Record for Dicotiledonous Wood and its Significance for Evolutionary and Ecological Wood Anatomy

Publisher Summary This chapter summarizes the evolution of wood anatomical traits in woody angiosperms and the recognition of ecological preferences from past geological records for a number of arbitrarily defined wood functional types. Xylem evolution can be viewed in the context of a “trade-off” triangle, with different adaptive solutions to the structure/function problems depending on environmental demands as well as phylogenetic constraints (taxonomic history). Evolution of xylem physiology is complicated by the fact that, ever since the early evolution of land plants, xylem has simultaneously performed multiple functions. Regression analysis of various physiological and anatomical characters is used in the chapter to look for trends and possible “trade-offs” between various extant species. The temporal and spatial distribution of the wood types is largely explained by the “tradeoffs” between xylem conductive efficiency and vulnerability to embolism. The two major causes of embolism in plants appear to be freezing and water stress, but the mechanism for embolism formation differs in these two cases. Regression analysis results provide a basis for understanding the variations in the incidences of vessel diameters as related to freezing and drought. However, additional studies are needed to elucidate the physiological significance of variations in vessel wall thickness, vessel perforation type, wood density and parenchyma distribution. The chapter concludes with a discussion on the ecological patterns in xylem anatomy in terms of their functional significance.

Elisabeth A. Wheeler

Papers

IAWA list of microscopic features for softwood identification

IAWA list of microscopic features for hardwood identification : with an appendix on non-anatomical information

Inside Wood – A Web resource for hardwood anatomy

A Survey of the Fossil Record for Dicotiledonous Wood and its Significance for Evolutionary and Ecological Wood Anatomy

Evolution of xylem physiology