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:: The use of aerial photography for assessing soil disturbance caused by logging. J. G. Firth

Document type:: Multivolume work

Structure type:: Chapter

Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 441 The use of aerial photography for assessing soil disturbance caused by logging J.G.Firth Forest Research Institute, Rotorua, New Zealand ABSTRACT: When harvesting takes place in forest plantations, it is common for logging machinery such as skidders and crawler tractors to traverse 50% or more of the area. The damage caused to the soil through compaction and soil removal ranges from slight to severe and may lead to slower growth of the subsequent tree crop and an increased probability of erosion. A technique is described for classifying and mapping this disturbance using small-format colour aerial photographs. Also mentioned are some aspects of the role of aerial photography in harvest planning and in determining the effect of soil disturbance on tree growth. 1 INTRODUCTION Each year throughout the world millions of hectares of forest are logged using skidders and crawler tractors. In New Zealand alone, the area logged by these machines amounts to about 15 000 ha annually. As the logs and logging machines pass over the forest floor, it is not uncommon for 50% or more of the total forest area to be disturbed by compaction and removal of the various soil horizons (Murphy 1984). The soil's airspace is reduced, its bulk density increased, and its moisture regime altered (Steinbrenner and Gessel 1955). With more and more forests in New Zealand moving into their second and subsequent rotations, attention is being focused on the growth losses which may occur in the new crop through the disturbance done to the soil during thinning and harvesting the old crop. If the area disturbed is large, the effect long term, and the reduction in tree growth significant, the potential exists for a very serious and expensive problem. Some years ago, the New Zealand Forest Research Institute (FRI) decided to investigate harvesting- related soil disturbance and its effect on tree growth. The research was divided into four phases. 1. Classifying the disturbance. 2. Mapping the disturbance. 3. Investigating the relationship between soil disturbance and tree growth. 4. Finding ways to reduce soil damage and improve the soil. It was soon found that aerial photography had a significant part to play in this research and some aspects of its role are outlined below. 2 CLASSIFYING AND MAPPING SOIL DISTURBANCE A brief walk through a thinned or logged forest soon reveals that the disturbance caused by logging machinery may range from nil (soil is completely undisturbed) to severe (the litter and top soil have been completely removed and the subsoil compacted into an impervious rock-hard mass). Murphy (1982) has divided this disturbance into five visual damage classes or strata: 0 - Machines have not travelled over the area. 1 - Machines have travelled over the area but have not broken through the litter layer. 2 - Machines have broken through the litter layer and started to compact the topsoil. 3 - Most of the topsoil is puddled, and subsoil compaction has begun. 4 - Subsoil is puddled and compacted. Murphy (1984) has successfully used his classification to assess 18 logging sites around New Zealand using a line transect method similar to that tried by Dyrness (1965). However, walking to and fro over logging slash can be very arduous. In addition, the transect’ method, while providing good overall disturbance proportions, is not suitable for producing maps showing the pattern of the disturbance. It was thought that by using aerial photography to bring the logged area into the office, the assessment of soil disturbance could be done easily and more effectively. The specifications for the photography were: Camera - Hasselblad Format - 55 x 55 mm Film - Colour negative - Colour transparency Negative scales - Between 1:5000 and 1:15000 Three people were asked to interpret the aerial photographs using Murphy's classification and then to check their efforts in the field. The results were disappointing with differences of up to 59% being obtained. It was therefore decided to modify Murphy's classification so that the strata more closely reflected how soil disturbances appear on the aerial photographs. Furthermore, objective elements of interpretation were introduced where possible. The system shown in Table 1 was devised. Its main components are: 1. the existence and importance of the skid trails, and 2. the colour difference between the top soil and the subsoil. This new classification was tested by several people using various sets of aerial photographs of different logged areas. Consistent results were obtained between interpreters and there was good agreement with the ground truth, differences being under 10%. Subsequent experience with the method showed that the photographs should be taken as soon after logging as possible before weed growth obscurs valuable detail. It was also found that large negative scales (> 1:10000) are not as useful as smaller ones (1:10000-1:20000) because the large scales emphasised irrelevant detail.

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