RESUME L'objectifde cette etude est de determiner Ie potentiel des images de teledetection satellitaire comme mesure previsionnelle de la complexite de la structure de laforet et de l'dge des peuplements. Des relations empiriques entre les parametres structurels de laforet et les donnees Landsat Thematic Mapper ont ete analysees pour un echantillon de cedres et pruches. et des peuplements d'epinettes d'Engelmann et de sapins de l'Ouest, pres de Revelstoke. en Colomhie hritannique. Les methodes utilisees pour mesurer la structure des peuplements forestiers sont presentees suivi d'une discussion sur l'analyse de correlation entre les variables de terrain et la creation d'un indice de complexite structurelle (SCIstructural complexity index) derive d'une analyse en composantes principales de plusieurs variahles individuelles liees au peuplement. Les valeurs d'humidite TM derivees de la transformation « tasseled cap» ont ete correlees fortement avec l'dge du peuplement et avec la complexite structurelle dans Ie cas des peuplements matures et ages. On demontre que la distrihution spatiale des valeurs d'humidite TM est reliee ala composition de la vegetation et ala structure des communautes de climax a l'interieur de deux sous-zones biogeoclimatiques majeures qui occupent la region. Les relations empiriques entre les valeurs d'humidite TM et Ie stade de succession recent ou avance de la structure des peuplements se sont averees variables. La composition heterogene des especes dans ces communautes peut expliquer les relations statistiques plus faibles. Les resultats demontrent l'utilite de l'application de la composante humidite de TM pour la classification de la structure forestiere pour les peuplements forestiers matures et ages et pour la cartographie des habitats a l'interieur de cette zone d'etude. SUMMARY The goal of this study is to determine the potential (~l satellite remote sensing image data as a predictive measure offorest structural complexity and stand age. Empirical relationships between forest structural parameters and Landsat Thematic Mapper data were analyzed for a sample of cedar/hemlock. Engelmann spruce/suhalpine fir stands. near Revelstoke, British Columbia. The methods used to measure forest stand structure are outlined. followed by a discussion of the correlation analysis between field variables, and the creation of a structural complexity index (SCI) derived from a principal components analysis of several individual stand variables. TM Tasseled Cap wetness values were highly correlated to stand age and structural complexity for mature and old growth stands. The spatial distribution of TM Wetness values was shown to he related to the vegetation composition and structure of climax communities within two major biogeoclimatic subzones that occupy the region. Empirical relations hetween TM Wetness and seral and late seral stand structure were variable. A heterogeneous species composition ofthese communities may explain the weaker statistical relationships. The results support the application ofthe TM ...
Bjømstad, O. N., Iversen, A. & Hansen, M. 1995. The spatial structure of the gene pool of a viviparous population of Poa alpina— environmental controls and spatial constraints. — Nord. J. Bot. 15: 347–354. Copenhagen. ISSN 0107–055X. Because both the genetic make‐up and the environmental conditions of a population are spatially autocorrelated, it is difficult to infer processes of selection or drift for population genetic mappings. We propose a methodology based on partial Mantel techniques and partial autocorrelation techniques to separate the action of these processes. The method is applied to data on Poa alpina to indicate that isolation‐by‐distance (drift) is the main process inducing positive autocorrelation at the scale of diaspore dispersal (< 100m). The pattern at larger distances is more consistent with selection.
Satellite remote sensing data and methods can be used to develop maps of large areas at different times in order to assess changes in forest ecosystem patterns and processes. Such maps are useful in understanding wildlife populations and habitat, forest biodiversity, and forest productivity. They may be important in ecological monitoring programs at multiple spatial and temporal scales, and could include assessment of structural aspects of the landscape, such as forest or habitat fragmentation. Quantification and measurement of landscape structure depend on the definition of landscape classes or patches, defined on the basis of more or less homogeneous elements, which differ in some measurable way from neighbouring patches. In this paper, we review some of the issues, and provide examples using satellite remote sensing data, in the quantification of landscape structure in two Canadian forests. The link between landscape structure and biodiversity is provided through the emergence of ecological understanding of species richness, species-habitat or niches, and metapopulation dynamics.Key words: forest disturbance, landscape metrics, satellite remote sensing, forest fragmentation, monitoring, biodiversity, change detection Les donnCes et les mCthodes issues de la tClCdCtection par satellite peuvent &tre utilisCes pour Claborer des cartes couvrant de grandes superficies ii diffkrentes pCriodes de f a~o n B Cvaluer les changements dans les patrons et les processus des Bcosystttmes forestiers. De telles cartes permettent de mieux saisir les habitats et les populations fauniques, la biodiversitk forestittre, et la productivitC des for& Elles peuvent ttre importantes dans le cas des programmes de surveillance Ccologique effectuke h BiffCrentes Cchelles spatiales et temporelles, et pourraient comprendre 1'Cvaluation des aspects structuraux du paysage, comme la fragmentation des f o r b ou des habitats. La quantification et la mesure des structures du paysage dCpendent de la dkfinition des classes du paysage ouparcelles, qui sont dCfinies selon plus ou moins dlCICments homogttnes, qui different d'une quelconque f a~o n mesurable des parcelles adjacentes. Dans cet article, nous rivisons certaines de ces questions, et nous apportons des exemples tires des donnCes de tClCdCtection par satellite sur la quantification de la structure du paysage dans le cas de deux for& canadiennes. Le lien entre la structure du paysage et la biodiversitC est Ctabli par 1'Cmergence de la reconnaissance de la richesse en terme d'espttces, de l'habitat pour chaque espttce ou des niches, et des dynamiques des metapopulations.
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