Abstract
Plant functional traits capture important variation in plant strategy and function. Recent literature has revealed that within-species variation in traits is greater than previously supposed. However, we still have a poor understanding of how intraspecific variation is coordinated among different traits, and how it is driven by environment. We quantified intraspecific variation in wood density and five leaf traits underpinning the leaf economics spectrum (leaf dry matter content, leaf mass per unit area, size, thickness and density) within and among four widespread Nothofagus tree species in southern New Zealand. We tested whether intraspecific relationships between wood density and leaf traits followed widely reported interspecific relationships, and whether variation in these traits was coordinated through shared responses to environmental factors. Sample sites varied widely in environmental variables, including soil fertility (25–900 mg kg–1 total P), precipitation (668–4875 mm yr–1), temperature (5.2–12.4 °C mean annual temperature) and latitude (41–46 °S). Leaf traits were strongly correlated with one another within species, but not with wood density. There was some evidence for a positive relationship between wood density and leaf tissue density and dry matter content, but no evidence that leaf mass or leaf size were correlated with wood density; this highlights that leaf mass per unit area cannot be used as a surrogate for component leaf traits such as tissue density. Trait variation was predicted by environmental factors, but not consistently among different traits; e.g., only leaf thickness and leaf density responded to the same environmental cues as wood density. We conclude that although intraspecific variation in wood density and leaf traits is strongly driven by environmental factors, these responses are not strongly coordinated among functional traits even across co-occurring, closely-related plant species.
Highlights
Consistent correlations among plant traits, and between plant traits and environment, are the basis for defining and interpreting plant strategies [1,2,3]
Leaf size did not decrease with increasing wood density within any of the four species, despite this being the most consistently reported pattern of interspecific covariation between wood density and a leaf trait (Table 1; Fig. 2)
There was weak intraspecific evidence that leaf dry matter content (LDMC) and leaf density both increased with wood density, pointing to coordinated investment in dry matter allocation to both leaves and wood within species
Summary
Consistent correlations among plant traits, and between plant traits and environment, are the basis for defining and interpreting plant strategies [1,2,3]. There is clear evidence for consistent trait correlations and trait syndromes among species, these have not been rigorously tested within species. Recent studies have revealed that intraspecific variation is a major component of trait variation, both within and among communities, more so than previously supposed [7,8,9,10,11,12]. As different mechanisms may constrain trait–trait combinations within species to those widely observed among species [16,17], studies of both inter- and intraspecific variation are valuable for gaining a comprehensive view of the drivers of trait variation
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