ROE DEER IMPACT DURING FOREST CONVERSION
FOREST HABITAT MANAGEMENT, POPULATION DYNAMICS OF ROE DEER, AND BROWSING IMPACT: RESULTS OF A LONG-TERM STUDY ON
FOREST-CONVERSION IN THE HIESBERG AREA OF LOWER AUSTRIA
Ernst Partl, Johanna Schweiger-Adler, Friedrich Reimoser
Research Institute of Wildlife Ecology, Veterinary University, Savoyenstrasse 1 A-1160 Vienna, Austria
Extended Abstract
Following forest conversion the short- and long-term effects and consequences of habitat changes were investigated in the Hiesberg area of Lower Austria near Melk. The study comprises a forest area of about 600 ha. From 1984 to 1994 data on forest structure, habitat quality, browsing impact, population dynamics, distribution and huntability of roe deer (Capreolus capreolus) were collected and analysed. The main research objective is to assess the effect of forest-structure changes on browsing impact, habitat suitability, roe-deer population, huntability of roe deer, and changes in forest’s predisposition to browsing damage. As a result of forest conversion in the study area, the key habitat factors for roe deer were expected to change in a decrease of food supply connected with a simultaneous increase of cover and shelter. The assumption to be proved was derived from the expert system “game ecology-forest regeneration” - the theoretical base of this long-term study (Reimoser & Zandl 1993; Reimoser 1994). The effects of habitat changes were investigated following large-scale afforestation of pioneer-species and shrub-forest areas with conifers and broad-leaved trees. The results of the study show the change in habitat conditions, the reaction of the roe-deer population, the development of browsing impact, and the change in huntability of roe deer caused by forest conversion. In addition a monitoring of roe deer’s health status (parasitic infestation, blood parameters), stress, body condition, burden of environmental pollutants, feeding selection, metabolism of minerals and trace elements was carried out.
The following hypotheses were to be tested in this case study:
(i) The proportion of regeneration stands would decrease, because further regeneration measures are rare and the existing regeneration areas become thickets;
(ii) Thermal and hiding cover would increase with the development of the young forest; (iii) The available food supply would decrease as a result of reduced light on the forest
floor;
(iv) Time to observe a roe deer would increase, because hiding cover increases and/or the roe deer population decreases;
(v) Sex-ratio would change in favour of male roe deer, because the food supply decreases; (vi) Fawn rate observed (fawns per female) would diminish, because the food supply
decreases;
(vii) Intensity of culling (roe deer killed per roe deer observed) would increase, because selective culling becomes more difficult (hunting strategies, i.e. number to be culled, was set during the period at 140 head of deer per km² to keep this factor constant); (viii) The browsing impact on forest regeneration would increase, because the
predisposition of forest to game damage increases;
With the exception of (vi) all the underlying null hypothesis had to be rejected at significance level α=0,05. But the tendencies for (iii) and (v) were found to be contrary to the expected. When forest conversion is carried out in roe-deer habitats, it is meaningful to take roe-deer habitat factors into account. These include settling attractiveness, predisposition of forest to game damage, and possibilities for hunting in closed forests (a favourable deer distribution and suitable ratio of available food supply and settling factors). Consequences for forest and wildlife management are highlighted.
The Hiesberg-area case study confirmed that the theory behind the “game ecology — forest regeneration“ expert system (Reimoser & Zandl 1993) is valid for many factors. The fact that some hypotheses could not be confirmed (e.g. decreasing food supply, sex ratio) is explainable in terms of the storm damage in 1990, which reduced the canopy density of pole and timber stands significantly (increased light transmission to the ground). Thus, food dependent indicators reacted consistently in the opposite direction to that assumed.
Keywords: forest habitat management, forest conversion, expert system, roe deer, wildlife management
Literatur:
Reimoser, F (1994). Expert system ‘game ecology - forest regeneration’. In Status Diagnosis and Rehabilitation Concepts for Impacted Forest Sites in the Bohemian Massif. Forstliche Schriftenreihe, 7: pp 237-255. Universität für Bodenkultur Wien.
