Is the age of forest habitats affecting the reproductive rate of generalist predatory ground beetle species?

Ziesche, T. and Roth, M. (2007) Is the age of forest habitats affecting the reproductive rate of generalist predatory ground beetle species? Community Ecology, 8 (2). pp. 183-194. ISSN 1585-8553

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Abstract

This study aimed at the effects of habitat age on the reproductive rate of three ground beetle species that are common and widely distributed in forest ecosystems of Europe ( Abax parallelepipedus (Pill. & Mitt.), Pterostichus oblongopunctatus (F.), Pterostichus burmeisteri (Heer.)). The study sites comprised comparable age classes, i.e., young stands, mature stands, and mature forests with upcoming and established natural regeneration of four different forest types, namely pure stands of spruce and Douglas fir, and mixed stands of spruce-beech and oak-beech. As an indicator for the reproductive rate of female beetles, the number of ripe eggs in the ovaries and the duration of the reproduction period were investigated from captures of pitfall trapping (n = 8 per site). The dissection of a total of 1236 females uncovered 1704 eggs. A broad spectrum of environmental factors including microclimate (temperature, humidity, precipitation), soil parameters (moisture, pH, thickness and coverage of litter layer) and vegetation characteristics (coverage of moss, herb, grass, shrub and natural regeneration, degree of canopy closure) was assessed to reveal the relevant factors influencing the reproductive success.Within the forest types, the egg-load of the ground beetle species showed statistically significant relations to the age of the stand type. For A. parallelepipedus , a quite uniform reaction pattern was evident with significantly higher egg-loads in the mature forests compared to the young stands. This was accompanied by a longer duration of the reproduction period. A stronger influence of the forest type was obvious for the egg-load of Pt. oblongopunctatus and Pt. burmeisteri . The reproductive rate was generally increasing with temperature aspects in forest sites and was significantly influenced by moisture parameters. The mean maximum temperature of the habitat cared for most of the variation in A. parallelepipedus (61.4%), while the mean minimum temperature explained 60.7% of the reproductive potential in Pt. oblongopunctatus . The variation of Pt. burmeisteri was best explained by the humidity of the air (49.4%). Thus, the results of our study emphasize the role of abiotic parameters on the reproductive rate of ground beetles.

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