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In 1994 grazing by large herbivores ceased with the erection of a perimeter deer fence and the removal of red deer and sheep. Past grazing management practices such as muirburn also ceased and natural woodland regeneration was encouraged. However, some of the Tireragan woodland is quite old, with little sign of internal regeneration, perhaps reflecting the consequences of previous grazing. We want to investigate how the woodland flora and fauna will repsond to the experimental clearance of some mature trees. Because most changes are likely to be quite slow we have decided to establish some permanent quadrats that can be monitoried over a long period of time.
Four experimental sites were identified on the northern, western and southern slopes of Torr Fada. This is the first hill that is encountered on entering the estate. These locations were selected because of the quality and accessibility of the woodlands. All are close to reasonably good paths and access to them does not present any significant threat to health and safety. Although there is excellent woodland on the eastern side of Torr Fada much of this is close to a large cliff and was therefore excluded. Similarly, there are other significant areas of woodland elsewhere on the estate, for example on the northern slopes of Aird Mor, that were not used because we considered that current and future access (as scrub and woodland regeneration continues) would present unnecessary risks to health and safety.
At each site permanent quadrats were established and marked to allow continuous recording over a number of years. Details of the marking procedure are available on a separate page. The positions of the quadrats were largely determined by logistic constraints. For example, there had to be sufficient space to position a 1 m by 1 m recording frame and the soil had to be of sufficient depth to allow bolts to be set in concrete. Secondly the quadrats had to be sufficiently spaced so that the removal of some trees would have a minimal impact on control quadrats.
The only recodings taken during the first year were measurements of surrounding trees and detailed photographs of the vegetation in the permanent quadrats. It was decided not record invertebrates and birds during this establishment phase because of disturbance caused while setting up the experiment. In each of the four sites there are control and experimental quadrats. Experimental quadrats will experience a significant increase in light intensity following the selective coppicing of neighbouring trees. Experimental trees were coppiced in September 2003.
It is important to remember that this is a long term experiment. We do not expect many immediate changes, but we are hopeful that changes will become more obvious during the next 3 to 4 years.
We do have some data on the invertebrate fauna within the hazel woodland. These data are available from the page with the addtional datasets.
It is important that the locations of the quadrats can be identified on subsequent visits. Experience from earlier tests suggests that this is not always easy! We have recorded the quadrat locations using a hand held GPS and tests indicate that we can achieve a spatial accuracy of ±4 m. Although this sounds impressive, and does enable the general area to be located, there is still sufficient error to cause some confusion on the ground. Consquently, one of the concrete marker bolts for each quadrat is labelled with the quadrat number. Details of the spatial accuracy tests are available on a separate page. Similarly, the location of each quadrat is also available on a separate page.
Each quadrat was photographed using an Olympus 730UZ digital camera mounted a specially constructed tripod. The tripod allowed the camera to be positioned over the center of the quadrt at a sufficient height to allow the whole quadrat to be included in the field of view. The camera was set to minimum zoom with automatic exposure. Images were recorded in a TIFF format (1600 x 1200 pixels) to ensure no loss of detail. The image resolution equates to an approximate scale of 1 mm per pixel, thus ensuring that considerable detail is retained in the photographs. Images are available in an unprocessed format. This means that there is some skewing of the quadrats and some 'fish-eye' lens distortion.
In addition to the photography, the presence of plant species was recorded, in the field, within the 64 10 cm by 10 cm sub-quadrats.
The distances to, and characteristics of, the five nearest trees to each quadrat were recorded. Each of these trees was marked with a permanent tree tag (a small metal numbered tag) to enable the futire recording of unambiguous data. Obviously some trees were nearest to more than one quadrat. The height of each tree was recorded using a professional tree height pole (a graduated telescopic pole). The circumference, at breast height, was recorded if the tree was a birch or rowan. This method was inappropriate for hazels because they were multi-stemmed and some stems were not vertical (see image below).
In the case of hazels the number of live stems, plus the larget circumference, was recorded. In total 63 trees were recorded.
On September 25th 2003, five trees (tag numbers 0, 10, 31, 33 & 46) were felled at sites A, B and D. It was not possible to fell any trees at site C because of time constraints. We hope to complete the experimental treatment at site C in early 2004. As stems were removed from a tree their compass orientations were recorded on the stem and sections of the coppiced stems were retained and photographed to record their lichen cover. Sections of the coppiced stems were also smoothed and polished to enable their ages and growth patterns to be determined. Photographs of these sections are available in the results section. The coppicing was undertaken by Alan Fielding and Paul Haworth with the assistance of Phil Whitfield and Dave McLeod.
The photographs below show trees 31 and 33 (Site A) before and after felling.
During 2006 and 2007 it has become clear that red deer have re-entered the estate, almost certainly coming across Traighgael beach at low tide (footprints). It is also clear that there has been considerable deer activity above one of the 'birch' sites and within the hazel site. There is strong evidence that the hazel regrowth has been grazed.
The first photograph shows grazed regrowth on tree number 49.
The second photograph shows clear evidence of considerable deer activity above site C.
There is additional evidence that deer are still having an impact. Tree number 56 was one of the original coppiced trees but it shows no sign of regeneration. Indeed, the few signs of regrowth have been grazed by deer. Additional evidence of the presence of deer is the presence of footprints in quadrat D1.
Tree number 0 was also coppiced but has now almost achieved the orginal canopy height. Previously the regrowth on this tree had been grazed.
