2026-09-23T05:16:34Zhttps://api.repository.cam.ac.uk/server/oai/request

oai:www.repository.cam.ac.uk:1810/2976592021-04-21T20:15:13Zcom_1810_183634com_1810_256064col_1810_214795

Remote sensing characterisation of the forest-tundra ecotone 10.17863/CAM.44713 guo, wenkai Rees, Gareth The transition zone between the boreal forest and Arctic tundra, the Forest-tundra ecotone (FTE), is an area of high ecological and climatological significance. Satellite remote sensing has the potential to enable accurate circumarctic mapping and characterisation of both latitudinal and altitudinal FTEs. This study aims at a multi-platform, multi-scale characterisation of the FTE phenomenon and an evaluation of the response of the interface to climate change. This involves three main steps: FTE delineation, FTE categorisation based on the spatial characteristics of the interface, and the investigation of the relationship between FTE dynamics and spatial configuration in the circumarctic region. FTE delineation is conducted using an image texture-based classification scheme developed to statistically exploit the spatial patterns of the interface. Image texture statistics for tree cover density are derived from the grey-level co-occurrence matrix (GLCM), and the Landsat Vegetation Continuous Fields (VCF) product is used as the primary data source. The outcome offers advantages, both visually and statistically, over traditional image classification methods and can be applied to different parts of the circumarctic region. Several globally occurring primary spatial ‘forms’ are recognised for altitudinal FTEs which are found to have linkages to the sensitivity of the interface to shift with climate change. A technique is developed to categorise the FTEs into these spatial forms by the degree of fragmentation of the interface. The technique involves a texture extraction algorithm named FOurier-based Textural Ordination (FOTO) and supervised classification. Normalised Difference Vegetation Index (NDVI) calculated from Sentinel-2 imagery is used for FTE derivation and categorisation. Finally, the relationship between the response of circumarctic latitudinal FTE to climate change and its spatial characteristics is investigated at MODIS (MOderate Resolution Image Spectroradiometer) resolution utilising the data availability and computing powers of the Google Earth Engine (GEE) platform. Building on the theory of treeline ‘forms’, a continuous measurement of fragmentation is developed based on window spectral analysis to represent the spatial characteristics of the FTE. Statistical relationship between FTE fragmentation, dynamics and continentality is analysed. This provides insight into how FTE spatial configuration links to interactions between the interface position and outside forcing, which can potentially contribute to the optimisation of future climate modelling as well as the modelling of vegetation reactions to climate change. University of Cambridge 2019-10-26 Thesis Doctoral Doctor of Philosophy (PhD) en the cambridge trust, trinity college, china scholarship council https://www.repository.cam.ac.uk/handle/1810/297659 https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/726edd3c-d460-4db9-b9a9-8d2bca388c30/download 87eda9de84448d1f82354d60eee3eb5f https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/7abab1b7-7685-4996-a316-14aa4d224964/download 96eab7146765449cb5c93936a7e8270a https://www.rioxx.net/licenses/all-rights-reserved/ remote sensing forest-tundra ecotone vegetation continuous fields texture analysis image classification google earth engine