Ecosystem – service provision by the biofuel feedstock plant, Miscanthus x giganteus

Abstract

Dairy expansion on the Canterbuty Plains has led to a gross simplification of the agricultural landscape, particularly in the form of shelterbelt removal to allow for the implementation of pivot irrigators. This decline in landscape structure can be seen in multiple agroecosystems worldwide and has been linked to decreases in key ecosytem services such as the biological control of insects. This trial evaluated selected ecological effects surrounding the improvement of landscape complexity through the inclusion of the biofuel feedstock plant Miscanthus x giganteus as a shelterbelt on a Canterbury dairy farm. This information was collected through four separate experiments: 1. The use of tracking tunnels to identify potential ecosystem disservices provided by M. x giganteus in the form of harbouring rodent populations. This was compared with standard Canterbury post-and-wire fence lines in addition to Cortaderia selloana shelterbelts 2. The use of ‘bumblebee motels’ to identify any differences in nesting rates by bumblebees between M. x giganteus shelter and a standard Canterbury dairy farm fence line 3. Invertebrate monitoring to identify any potential differences in natural enemy and pest populations between M. x giganteus shelter and a standard Canterbury dairy farm fence line 4. A glasshouse experiment measuring the growth effects of various strain mixtures of the beneficial fungus Trichoderma atroviride on the performance of M. x giganteus seedlings

Results from tracking tunnel analysis indicated no sginificant differences in rodent populations between M. x giganteus, C. selloana and unimproved fence lines. This was, however, thought be due to relatively few experimental replicates. Trends indicating C. selloana harbouring higher rodent numbers than M. x giganteus were identified. Bumblebee motel monitoring yielded no information concerning bumblebee nesting preference due to the timing in which the Honours project was undertaken. Motels were instead used as another measure of rodent populations, indicating a significant difference in these populations between M. giganteus shelter and unimproved fence lines. Invertebrate population monitoring revealed a significant increase in natural enemy populations (2.8 times higher) between M. x giganteus shelter and unimproved fence lines. This has potential to increase potential biological control of pasture pest species, a key ecosystem service. Three out of five T. atroviride strain mixtures significantly increased the performance of M. x giganteus plants compared to a control. Mixture PR6 was identified as forming the most beneficial symbiosis, increasing plant height by 28%, shoot numbers by 39% and chlorophyll content by 15%.