PARENT SESSION
Oral Session #8: Plant Ecology: Nutrient Uptake, Movement, Use.
Presiding: V. Gutschick
Monday, August 5. 8:00 AM to 11:30 AM. Grand Ballroom West, Radisson.

Relationships among leaf and root traits in grasslands of New Zealand and Australia.

Craine, Joseph^*,1, Lee, William¹, Williams, Dick², ¹ Landcare Research, Dunedin, New Zealand² CSIRO, Darwin, Australia

ABSTRACT- Across 30 grassland sites in New Zealand that ranged from native alpine grasslands to low-elevation improved pastures, leaf traits of grasses correlated with fine root traits. Across 118 plants sampled, nitrogen concentration, tissue density, thickness, 13C and 15N of leaves were correlated with the corresponding traits of fine roots. Plants of high altitude sites have low N concentrations in both their leaves and roots, and have thick leaves and roots, yet no differences in tissue density or photosynthetic water use efficiency when compared to plants of low altitude sites. Both the leaves and roots of the high altitude plants were depleted in 15N relative to the low altitude plants, indicating that the low-N set of traits is likely associated with a more closed N cycle at high altitude. Examining 72 plants from 15 sites from C4 northern Australian monsoonal grasslands, the leaves and roots of Australian grasses measured were denser, coarser, lower in nitrogen concentrations and more enriched in 15N than New Zealand grasses. Yet, relationships among the traits of Australian samples were similar to New Zealand. Plants with low leaf N concentrations had low root N concentrations, high tissue density and were more depleted in 15N. This supports the hypothesis that there are tight linkages between the functional traits of roots and leaves and that simple measurements on leaves may be powerful in predicting root traits across broad gradients.

KEY WORDS: grasslands, functional traits, N cycling