Macro-element composition of tall-tussocks (Chionochloa) in the South Island, New Zealand, and their relationship with soil chemical properties

Abstract

Concentrations in sheaths, green blades, and dead tips, and weights per shoot, of P, N, S, K, Mg, Na, and Ca are reported for seven species of Chionochloa from sites throughout the South Island. Species means for C. flavescens, C. macra, C. rigida, and C. rubra are comparable with those obtained in previous studies from eastern South Island. C. pallens has concentrations of P and N comparable with most species, but higher than C. rubra and C. juncea. C. pallens has the highest Mg concentrations in green blades (1.08 mg/g) and C. crassiuscula the lowest Ca concentrations (0.56 mg/g). There are wide inter-specific differences in Na: C. crassiuscula (1.23 mg/g), C. pallens, C. rubra > C. juncea, C. flavescens, C. rigida, C. macra (0.10 mg/g); and S: C. crassiuscula (1.40 mg/g), C. juncea > C. pallens, C. rubra, C. flavescens, C. macra, C. rigida (0.71 mg/g). There are substantial and significant inter-specific differences at sympatric sites for most elements, but inter-specific relationships differ from site to site.

Correlations between the weight of P in shoots of each species with soil inorganic P fractions reflect the degree of weathering and leaching at the sites they are gener.ally associated with, and, in some cases, their responses to fertilisers shown by previous workers. C. flavescens and C. pallens, both found characteristically on young soils, are correlated with Ca-P (HCl fraction) and C. pallens with Al-P (NH.F fraction); C. rigida is correlated with Fe-P (1st NaOH fraction) and Al-P; C macra with Al-P only. These correlations are compared with correlations between soluble-phosphorus extracting agents (Truog, Bray No. 1, Olsen) and shoot properties, which reflect the P fraction each extracts. Results are discussed in relation to species responses to soil nutnents. C. pallens, for example, despite having a marked capacity for shoot growth, has high P concentrations even on the youngest soils, possibly as a means of conserving P within the tussocks.

Within-species variation of K, and Ca, but not Mg, frequently correlates with soil Quick test levels for pH, and K, and Ca on a soil concentration and horizon-weight basis.

Many inter-element correlations of shoot concentrations are significant, e.g., K and Na are negatively correlated. Shoot S is correlated only with soil S in C. rigida and C. macra, species of the drier zones. Some taxa, particularly C. crassiuscula, may have evolved to use cyclic Na and S as an adaptation to the high precipitation and nutrient-leached nature of their insular environment.