Riparian plant species offer a range of organic resources to stream invertebrate communities through varied leaf breakdown rates

ABSTRACT

Riparian plants provide an important source of energy for freshwater food webs through inputs of leaf litter. Planting riparian buffers with mixed species could enhance the detrital resource supply for invertebrates through varied leaf breakdown rates. To quantify leaf breakdown rates and invertebrate colonisation, we used leaves from eleven grass, shrub and tree species common along agricultural waterways in New Zealand. Breakdown of leaves immersed in a spring-fed stream differed significantly among species, being fastest for pasture grass (k = 0.0458 day⁻¹) followed by broadleaf, pittosporum, willow, toetoe, poplar, gorse, Carex, eucalyptus, flax, and slowest for cabbage tree leaves (k = 0.0099 day⁻¹). Invertebrate community composition did not differ between leaf species, but consumers were extremely abundant on some leaves (e.g. 51–83 Potamopyrgus snails g⁻¹ pasture grass), indicating coarse detrital resources were in high demand for food or habitat. These breakdown rates could inform selection of riparian plant combinations that will enhance food availability for stream communities, especially continuity of supply, thereby contributing to waterway restoration.

KEYWORDS:

• Leaf breakdown
• riparian plants
• detrital resources
• invertebrate colonisation
• microbial respiration
• agricultural waterways

Acknowledgements

We thank Richard and Jill Simpson for providing access to the waterway and for their on-going support of our research. Thanks to Linda Morris for providing technical support and to Hilary Jacomb and Alex Rose for processing invertebrate samples. We also thank two anonymous reviewers for their time and helpful comments that improved this paper. This research was funded by the Mackenzie Charitable Foundation as part of the Canterbury Waterway Rehabilitation Experiment (CAREX; www.carex.org.nz). Funding provided by NIWA to KLH to support the final stages of manuscript preparation was appreciated.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Mackenzie Charitable Foundation.