Introduction and discussion

Environmental changes such as those on climate, atmospheric composition, land use and biotic exchanges
are triggering unprecedented ecosystem changes. The need to understand and predict them has given new
stimulus to a long tradition of study of the plant features (traits) that reflect species ecological strategies and
determine how plants respond to environmental factors, affect other trophic levels and influence ecosystem
properties (Kattge et al. 2011). There is mounting evidence that variation in plant traits, and trait syndromes
(i.e. recurrent associations of plant traits), within and among species, is associated with many important
ecological processes at a range of scales. This has resulted in strong demand for standardised ways to
measure ecologically meaningful plant traits. The predecessor of the present handbook (Cornelissen et al.
2003) was written to address that need, by providing standardised, easily implemented trait-measurement
recipes for researchers worldwide. This updated version is an extension of that global collective initiative,
with an even broader scope.

The identification of general plant trait trade-offs associated with strategies and trait syndromes across
floras, taxa and ecosystems has been a long-standing focus in plant ecology, and has attracted increasing
interest in recent decades (e.g. Chapin et al. 1993; Grime et al. 1997; Reich et al. 1997; Cornelissen et al.
1999; Aerts and Chapin 2000; Westoby et al. 2002; Díaz et al. 2004; Wright et al. 2004; Cornwell et al.
2008; Baraloto et al. 2010a; Freschet et al. 2010; Ordóñez et al. 2010; Kattge et al. 2011). Ample evidence
indicates that plant traits and trait syndromes significantly affect ecosystem processes and services (for
overviews, see Lavorel and Garnier 2002; Díaz et al. 2007; Chapin et al. 2008; De Bello et al. 2010;
Cardinale et al. 2012). As a consequence, trait-based approaches are currently also gaining momentum in the
fields of agronomy and forestry (e.g. Brussaard et al. 2010; Garnier and Navas 2012), conservation (e.g.
Mace et al. 2010), archaeobotany (e.g. Jones et al. 2010), and at the interface between the evolution and
ecology in communities and ecosystems (e.g. Edwards et al. 2007; Cavender-Bares et al. 2009; Faith et al.
2010; Srivastava et al. 2012).

The quantification of vegetation changes in the face of modifications in climate at the global scale has
been significantly improved with the use of dynamic global vegetation models (DGVMs) (Cramer et al.
2001; Arneth et al. 2010). However, current-generation DGVMs do not yet incorporate continuous variation
in plant traits among plant species or types (Cornwell et al. 2009). Next-generation models could benefit
from the incorporation of functional traits and syndromes that are simple and general enough to be assessed
at the regional and global scales, and yet informative enough to relate to biogeochemical dynamics, dispersal
and large-scale disturbance (Ollinger et al. 2008; Stich et al. 2008; Doherty et al. 2010; Harrison et al. 2010;
Ma et al. 2010).

As a consequence of this surge of theoretical and practical interest, there has been a rapid expansion of
large regional and global trait databases (e.g. Díaz et al. 2004; Wright et al. 2004; Kleyer et al. 2008;
Cornwell et al. 2008; Chave et al. 2009; Paula et al. 2009; Baraloto et al. 2010a; Zanne et al. 2010; Fortunel
et al. 2012; Patiño et al. 2012). The TRY Initiative (Kattge et al. 2011; see Box 1) is compiling a communal
worldwide database of plant traits, an unprecedented step in improving the capacity of the scientific
community to access and utilise plant-trait information. In this context, standardisation of protocols
applicable under a wide range of situations and geographical contexts becomes even more important.

In this manual, we consider plant functional traits to be any morphological, physiological or phenological
feature, measurable for individual plants, at the cell to the whole-organism level, which potentially affects its
fitness (cf. McGill et al. 2006; Lavorel et al. 2007; Violle et al. 2007) or its environment (Lavorel and
Garnier 2002). As proposed by Lavorel et al. (2007), we will call the particular value or modality taken by
the trait at any place and time an ‘attribute’. Functional traits addressed in the present handbook range from
simple indicators of plant function (e.g. leaf nutrient concentrations as an indicator of both potential rates of
metabolism and of quality as food for herbivores) to plant functions themselves (e.g. palatability,
decomposability, capacity to resprout after a fire), always measured at the species level. The traits contained
in the handbook represent a set of functional traits of vascular plants that (1) can together represent key plant
responses to the environment as well as key plant effects on ecosystem processes and services at various
scales from local plots to landscapes to biomes, (2) can help answer questions of ecological and evolutionary
theory as well as practical ones related to nature conservation and land management (see Box 2 for a
Discussion) and (3) are in most cases candidates for relatively easy, inexpensive and standardised
measurement in many biomes and regions.

This is a recipe book to be used in the field and in the laboratory, and contains comprehensive, detailed,
step-by-step recipes for direct and, as far as possible, unambiguous use in any terrestrial biome. To that end,
we have had to make hard choices. We did not intend to provide a comprehensive list of all traits that could
potentially be measured nor a thorough description of the theory behind each trait. Rather, the present
handbook contains consensus traits and methods that researchers have identified as being useful, reliable and
feasible to be applied in large-scale comparative efforts. Some of them are well known and widely used,
whereas for others, relatively novel methods are described. Particular emphasis is given to recipes
appropriate for areas with high species richness, incompletely known floras and modest research budgets. We
give only brief ecological background for each trait, with a short list of references with further details on
significance, methodology and existing large datasets. The main section of each recipe contains a brief,
standardised protocol, and under the heading Special cases or extras, we give pointers to interesting
additional methods and parameters. Readers can find complementary methods and additional discussions and
comments in specific associated web pages (see Box 1). Specific citations have not been included in the
recipe descriptions. We hope that the authors of relevant publications (most of them cited at the end of each
recipe) will understand this choice, made for clarity and brevity, and in full recognition of the important
contribution that each of them and many additional studies have made to the theory and measurement
procedure for each trait.

This new handbook both updates theory, methods and databases covered by its predecessor (Cornelissen
et al. 2003), and provides protocols for several additional plant functional traits, especially for organs other
than the leaf. It has better coverage of (1) measurements important in less studied biomes and ecosystems,
(2) floras with special adaptations and (3) plant functions related to carbon and nutrient cycling, herbivory,
water dynamics and fire. We hope that the focus on practical techniques and streamlined trait recipes will
help this handbook become a useful reference in laboratories and in the field for studies around the world.
We strongly invite users to share their experiences with us about both general issues and specific details of
these protocols (see Box 1), so that the next edition will be an even better bed-side table companion.