Land use effects on biodiversity and ecosystem services.

Type of content
Theses / Dissertations
Publisher's DOI/URI
Thesis discipline
Ecology
Degree name
Doctor of Philosophy
Publisher
University of Canterbury
Journal Title
Journal ISSN
Volume Title
Language
English
Date
2020
Authors
Rossignaud, Laureline
Abstract

Since human arrival, New Zealand biodiversity has suffered from habitat destruction through land use change and the introduction of exotic plants and animals, leading to declines and extinctions of numerous native and endemic species. Such biodiversity loss can worsen ecosystem processes and services (e.g., water quality, pollination) which affect human well-being. My main objective was to study the effects of land use at several scales (land use on-site and adjacent land cover) on biodiversity and ecosystem services in Canterbury, New Zealand.

I examined native forest biotic resistance to exotic plant invasions by assessing the native-exotic plant richness relationship across spatial scales. I considered species competitive interactions, climate heterogeneity and environmental factors using a subset of the National Vegetation Survey, the Land Cover Database and climate data. The results showed that native tree diversity increased the resistance of forest to exotic plant invasions. Exotic grassland adjacent to forest plots led to an increase in exotic plant richness across all scales. Species competitive interactions affected the native-exotic richness relationship at small spatial scales while climate heterogeneity affected it at larger scales, consistent with hypotheses and the results of previous studies.

I assessed land use effects on insect pest control services, particularly through predation by birds. I exposed artificial caterpillars made from plasticine to predators within three land uses (exotic grassland, exotic forest and native forest), measured the proportion of each adjacent land cover type, and performed repeated 5-minute bird counts. I found no significant effect of local land use or bird relative abundance on predation rates by birds despite adjacent woody vegetation influencing bird community structure. However, bird predation rates on caterpillars were lower than in overseas studies for unknown reasons.

I examined land use effects on bird pollination service to harakeke (New Zealand flax, Phormium tenax). I compared fruit production between hand-pollinated and naturally pollinated flowers at sites with three different adjacent land uses and related this to bird abundance. I found that greater abundance of bird pollinators and lower proportion of adjacent exotic forest were correlated with higher fruit set, but I found little evidence for harakeke pollen limitation. Harakeke’s ability to self-pollinate may maintain a sufficient level of pollination when pollinator abundance is limited.

Finally, I analysed the long-term population trends of forest bird species and changes in the bird community structure at Craigieburn Forest Park in response to intermittent control programmes of stoat (Mustela erminea) an important introduced predator of birds. I compared 5-min bird count data from 1978-82 and 1999-2004 with my own data collected in 2019-20. Although bird population trends varied between species, bellbird, rifleman and tomtit appeared to have benefited from stoat control. However, the recent arrival of ship rats might bring new threats to local bird populations.

My research provides complementary new information on the influence of land use and adjacent land cover types on several ecosystem services. My findings highlight the importance of forest patches for maintaining bird biodiversity and the ecosystem services provided by birds. These results can assist decision making by land managers to enhance on native biodiversity and ecosystem services.

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Ngā upoko tukutuku/Māori subject headings
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