There is growing recognition that classifying terrestrial plant species on the basis of their function (into 'functional types') rather than their higher taxonomic identity, is a promising way forward for tackling important ecological questions at the scale of ecosystems, landscapes or biomes. These questions include those on vegetation responses to and vegetation effects on, environmental changes (e.g. changes in climate, atmospheric chemistry, land use or other disturbances). There is also growing consensus about a shortlist of plant traits that should underlie such functional plant classifications, because they have strong predictive power of important ecosystem responses to environmental change and/or they themselves have strong impacts on ecosystem processes. The most favoured traits are those that are also relatively easy and inexpensive to measure for large numbers of plant species. Large international research efforts, promoted by the IGBP–GCTE Programme, are underway to screen predominant plant species in various ecosystems and biomes worldwide for such traits. This paper provides an international methodological protocol aimed at standardising this research effort, based on consensus among a broad group of scientists in this field. It features a practical handbook with step-by-step recipes, with relatively brief information about the ecological context, for 28 functional traits recognised as critical for tackling large-scale ecological questions.

/pdf/a-handbook-of-protocols-for-standardised-and-easy-2uo4112zhh.pdf

A handbook of protocols for standardised and easy measurement of plant functional traits worldwide

Publisher Summary In this chapter, the advances that have been made in understanding the ecology of the mineral nutrition of wild plants from terrestrial ecosystems have been reviewed. This chapter is organized along three lines. First, the issues of nutrient-limited plant growth and nutrient uptake, with special emphasis on the importance of the uptake of nutrients in organic form—both by mycorrhizal and by non-mycorrhizal plants—and the importance of symbiotic nitrogen fixation is treated. In addition, the influence of allocation patterns on mineral nutrient uptake is described. Next, a few of the nutritional aspects of leaf functioning and how nutrients are used for biomass production by the plant are explored. That is done by studying the nutrient use efficiency (NUE) of plants and the various components of NUE. Finally, the feedback of plant species to soil nutrient availability by reviewing patterns in litter decomposition and nutrient mineralization is investigated. The chapter concludes with a synthesis of the various aspects of the mineral nutrition of wild plants. The chapter ends with a conceptual description of plant strategies with respect to mineral nutrition.

The Mineral Nutrition of Wild Plants Revisited: A Re-evaluation of Processes and Patterns

Publisher Summary This chapter discusses a search for physiological causes and ecological consequence in reference with the variation in growth rate between higher plants. When grown under optimum conditions, plant species from fertile, productive habitats tend to have inherently higher relative growth rates (RGR) than species from less favorable environments. Under these conditions, fast-growing species produce relatively more leaf area and less root mass, which greatly contributes to their larger carbon gain per unit plant weight. Fast-growing species also have higher respiration rates per unit organ weight, due to demands of a higher RGR and higher rate of nutrient uptake. Fast-growing species have a greater capacity to acquire nutrients, which is likely to be a consequence, rather than the cause, of their higher RGR. This chapter analyses variations in morphological, physiological, chemical, and allocation characteristics underlying variation in RGR, to arrive at an appraisal of its ecological significance. The lower specific leaf area (SLA) of slow-growing species is because of the relatively high concentration of cell-wall material and quantitative secondary compounds, which may protect against detrimental abiotic and biotic factors. This chapter concludes that it is likely that there are trade-offs between growth potential and performance under adverse conditions, however, the current ecophysiological information explaining variation in RGR is too limited to support this contention quantitatively.

/pdf/inherent-variation-in-growth-rate-between-higher-plants-a-26yywnhi7b.pdf

Inherent Variation in Growth Rate Between Higher Plants: A Search for Physiological Causes and Ecological Consequences

Geneticists and breeders are positioned to breed plants with root traits that improve productivity under drought. However, a better understanding of root functional traits and how traits are related to whole plant strategies to increase crop productivity under different drought conditions is needed. Root traits associated with maintaining plant productivity under drought include small fine root diameters, long specific root length, and considerable root length density, especially at depths in soil with available water. In environments with late season water deficits, small xylem diameters in targeted seminal roots save soil water deep in the soil profile for use during crop maturation and result in improved yields. Capacity for deep root growth and large xylem diameters in deep roots may also improve root acquisition of water when ample water at depth is available. Xylem pit anatomy that makes xylem less "leaky" and prone to cavitation warrants further exploration holding promise that such traits may improve plant productivity in water-limited environments without negatively impacting yield under adequate water conditions. Rapid resumption of root growth following soil rewetting may improve plant productivity under episodic drought. Genetic control of many of these traits through breeding appears feasible. Several recent reviews have covered methods for screening root traits but an appreciation for the complexity of root systems (e.g., functional differences between fine and coarse roots) needs to be paired with these methods to successfully identify relevant traits for crop improvement. Screening of root traits at early stages in plant development can proxy traits at mature stages but verification is needed on a case by case basis that traits are linked to increased crop productivity under drought. Examples in lesquerella (Physaria) and rice (Oryza) show approaches to phenotyping of root traits and current understanding of root trait genetics for breeding.

/pdf/root-traits-contributing-to-plant-productivity-under-drought-3jg834tnub.pdf

Root traits contributing to plant productivity under drought.

Triffids were, admittedly, a bit weird—but that was, after all, just because they were novelties. People had felt the same about novelties of other days—about kangaroos, giant lizards, black swans. And, when you came to think of it, were triffids all that much queerer than mudfish, ostriches, tadpoles, and a hundred other things? The bat was an animal that had learned to fly: well, here was a plant that had learned to walk—what of that? (from John Wyndham, The Day of the Triffids, 1951)

Foraging in Plants: the Role of Morphological Plasticity in Resource Acquisition

This paper discusses interspecific differences and phenotypic responses to nitrogen supply in various root parameters of five perennial grasses from contrasting habitats. The following root parameters were studied: root:shoot ratio, specific root length, specific root area, mean root diameter, frequency of fine roots, and the length and density of root hairs. Significant between-species variation was found in all of these features. Species from fertile sites had higher root:shoot ratios at high nitrogen supply than species from infertile habitats. All species growing at low nitrogen supply showed a significant increase in root:shoot ratio. Specific root length, specific root area, mean root diameter and frequency of fine roots were not affected significantly by nitrogen supply. Species from infertile sites responded to low nitrogen supply by a significant increase in root hair length and root hair density.

Manon Mensink

Papers

Size and morphology of root systems of perennial grasses from contrasting habitats as affected by nitrogen supply