Remote sensing for resources development and environmental management: Remote sensing for resources development and environmental management

Damen, M. C. J.

Bibliographic data

Multivolume work

Persistent identifier:: 856342815

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856342815

Language:: English

Additional Notes:: Volume 1-3 erschienen von 1986-1988

Editor:: Damen, M. C. J.

Document type:: Multivolume work

Volume

Persistent identifier:: 856343064

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Scope:: XV, 547 Seiten

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856343064

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(26,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: Damen, M. C. J.

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: 4 Renewable resources in rural areas: Vegetation, forestry, agriculture, soil survey, land and water use. Chairman: J. Besenicar, Liaisons: M. Molenaar, Th. A. de Boer

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: Photo-interpretation of wetland vegetation in the Lesser Antilles. B. Rollet

Document type:: Multivolume work

Structure type:: Chapter

Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 499 Photo-interpretation of wetland vegetation in the Lesser Antilles B.Rollet Office National des Forêts, Basse-Terre, Guadeloupe, France ABSTRACT: The wetlands of Guadeloupe are typified through photo interpretation on panchromatic 1:20000 flown in 1984 and earlier. Examples of interpreted photos are given and discussed. Geomorphology is a useful approach. Field observations for checking and collecting additional data especially on soils are indispensable before producing an ecological map. RESUME: Les terres basses de Guadeloupe sont classées en types de végétation par interprétation de photos aériennes panchromatiques au 1:20000 prises en 1984 et antérieurement. On donne des exemples de photos inter prétées et commentées. La géomorphologie est une approche utile mais des observations de terrain sont indis pensables pour vérifier avant extrapolation et pour prendre d'autres données, en particulier sur les sols afin d'établir une carte écologique. 1 INTRODUCTION Wetland vegetation is understood in a broad sense i.e. a vegetation under the influence of periodic inundation (fresh or seawater) or with poor drainage.; this includes mangroves, Pterocarpus and open swamps with 0 to 10 ? salinity submitted to tides or perma nent inundation during 6 to 8 months a year. Inun- dable pasture lands are discarded. 2 WETLAND VEGETATION TYPES The following is distinguishable on 1:20000 panchro matic : - Mangrove as a whole and its subtypes - Pterocarpus swamp forest - Dry deciduous or semi evergreen forest on karst Chrysobalanus thicket, sedge and fern swamps - Mudflat with algal cover, saltflats. Minor types, essentially woodlands or thickets are not readily recognizable : Hibiscus tiliaceus, Thespesia populnea, Conocarpus erectus, Annona glabra, Symphonia globulifera ; Dalbergia monetaria, Montrichardia along rivers. 3 PHOTO INTERPRETATION In Guadeloupe available airphotos are 1:20000 pan chromatic flown by IGN in 1962-63, 1968-69, 1982, 1984, also 1:50000 in 1950; and on limited areas 1:10000 colour taken by ORSTOM. The same applies to Martinique except that false colour 1:20000 was flown is 1975 (chanteur et al, 1980). The scale 1:50000 is indadequate to map distinct forest types within mangroves but mature monospe cific stands on large areas are recognizable (young stages much less so). Rules of generalization are necessary to map the innumerable mixtures of age- classes and species in a readable way. The identi fication of small areas e.g. 5 mm diameter of thickets woodlands and forests will not be possible generally for all the species enumerated above. Detailed field checks are always necessary. Cyperaceae (Cladium, Eleocharis, Rhynchospora) and fern swamps (Acrostichum, Nephrolepis) are well recognized as a whole but the species are difficult to separate even with the help of ecological consi derations. Unless there is a need for agriculture (disease detection, yield prediction), it is unli kely that special photography will be used for forestry only. Concerning the main vegetation types the situation is much brighter. Pterocarpus forests are easy to delimitate in general ; they show a dark velvety tone when crowns are fused ; emergents, irregularly open stands, transition zones, food crops beneath the forest introduce differences in the normal pattern. Large patches are quasi monospecific but quite often there is an assemblage with scattered rainforest species (Ficus, Symphonia, Cassipourea, Maytenus guianensis), and sometimes with Rhizophora (northern bank of the lower course of Grande Rivière à Goyaves or Laguncularia (west of Rivière Salée), in all cases undetectable. Mangroves can be subdivided fairly easily when stands are pure and mature : Rhizophora mangle is almost black, Avicennia germinans is salt and pepper (white with grey dots), Laguncularia racemosa is darker than Avicennia. Young stages of the three species are indistinct, pale grey, getting progres sively darker for Rhizophora when stands grow older. False colour is available in Martinique (not in Guadeloupe). Chanteur et al (1980) mention that Rhizophora and Laguncularia come out red, Avicennia blue, Conocarpus blue grey. Young stages are not distinguishable. These results confirm the findings in Mexico (Rollet, 1974) except that on 1:10000 Conocarpus was rather purple grey. On colour photos 1:10000 Avicennia is pale green, more yellowish than the two other species, not very distinct. On mature stands Rhizophora is bottle green, Avicennia yellow green, Laguncularia grey green easily mistaken for Rhizophora in mixtures. Mudflats come out white or mauve. The use of colour is questionable because of the extra cost for a limited additional information. False colour is an obvious breakthrough for spot ting Avicennia pure or in mixtures. Another device is needed to separate Laguncularia from Rhizophora. Undergrowths are not seen in most cases so that succession escape interpretation. Ill or decaying trees turn blue in false colour, in particular Rhizophora (Rollet, 1974), a source of misinterpre tation. Other mistakes will be avoided with some care : water bodies may be black or white in pan chromatic according to sun reflection and should not be taken for saltflats or mudflats. Film proces

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