Theme 23: Biodiversity

Description

In the hill country of New Zealand, the soil-sward relationship on hill microrelief was studied. Three categories of slope or microsites were distinguished: low, medium and high. The hypothesis was that soil variables of neighbouring microsites differ, and because of this, there is a segregation of species or functional groups of species between the microsites. Soil features, botanical composition and total annual yield were measured in the slope categories in two similar paddocks; one of which had received long-term phosphorus fertilisation and a non-fertilised paddock. ANOVA, cluster analysis and canonical variate analysis were performed on the data. Unsaturated hydraulic conductivity, slope, bulk density, volumetric soil moisture, soil total nitrogen content, soil phosphorus content and soil compressibility explained most of the variation between microsites. All the measured variables showed that differences amongst microsites were larger than between paddocks. The soil of the low slopes was more developed and fertile than the soil of the other microsites. From the botanical composition, seven functional groups were determined. Low slope microsites yielded significantly greater dry matter than medium and high slopes and were dominated by high fertility grasses and Lolium perenne. Low fertility species and Agrostis capillaris dominated the high slope category. Dicotyledons that colonised high fertility and species with low presence were indifferent to changes in the soil variables. The group of medium fertility species was intermediate between the high and low fertility groups. In conclusion, environmental variables segregated species and functional groups. Species and functional groups differed in ecological strategy. High competitors dominated in environments with high availability of resource. Environments with low resources availability were dominated by stress tolerant species.

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Species Segregation and Functional Groups in the Hill Country of New Zealand

In the hill country of New Zealand, the soil-sward relationship on hill microrelief was studied. Three categories of slope or microsites were distinguished: low, medium and high. The hypothesis was that soil variables of neighbouring microsites differ, and because of this, there is a segregation of species or functional groups of species between the microsites. Soil features, botanical composition and total annual yield were measured in the slope categories in two similar paddocks; one of which had received long-term phosphorus fertilisation and a non-fertilised paddock. ANOVA, cluster analysis and canonical variate analysis were performed on the data. Unsaturated hydraulic conductivity, slope, bulk density, volumetric soil moisture, soil total nitrogen content, soil phosphorus content and soil compressibility explained most of the variation between microsites. All the measured variables showed that differences amongst microsites were larger than between paddocks. The soil of the low slopes was more developed and fertile than the soil of the other microsites. From the botanical composition, seven functional groups were determined. Low slope microsites yielded significantly greater dry matter than medium and high slopes and were dominated by high fertility grasses and Lolium perenne. Low fertility species and Agrostis capillaris dominated the high slope category. Dicotyledons that colonised high fertility and species with low presence were indifferent to changes in the soil variables. The group of medium fertility species was intermediate between the high and low fertility groups. In conclusion, environmental variables segregated species and functional groups. Species and functional groups differed in ecological strategy. High competitors dominated in environments with high availability of resource. Environments with low resources availability were dominated by stress tolerant species.