Does prescribed fire mean a threat to the rare fagi? Larval-habitat preferences give the answer

Verena Möllenbeck1*, Gabriel Hermann2 & Thomas Fartmann1 1Institute of Landscape Ecology, University of Münster, Germany 2Working Group for Ecology and Planning, Filderstadt, Germany

Introduction Study species Methods

Within the vineyards of the Kaiser- Hipparchia fagi (Fig. 2) is a xero- Information on microhabitat use stuhl area, small slopes of traditional thermophilous satyrine species with gained by i) searching for adult vineyard terraces as well as large a Ponto-Mediterranean distribution. larvae in spring and ii) observation of slopes of land consolidation areas The Kaiserstuhl is the last remaining egg-laying females is compared to comprise a variety of habitats inclu- breeding area in Germany and the the spectrum of available micro- ding dry and semi-dry grasslands species’ northern range limit. habitats. The obtained larval habitat (Fig. 1) of high nature conservation Hibernating as larva in grasslands, preferences are used to estimate the relevance. Formerly used for hay- the species was assumed to be impact of winter burning on popu- making, these slopes suffer from vulnerable to winter burning. lation viability of H. fagi. invasion of woody species and peren- nial herbs today. To maintain an Results open meadow-vegetation structure, The important parameters for larval habitat choice of H. fagi are: prescribed fire management in late winter has been reintroduced. ƒ Microclimate – Larval habitats are hot due to their south to south-western The Kaiserstuhl area, a volcanic aspect and the absence of shading shrubs. mountain remain situated in the ƒ Vegetation structure – Sites with 100 *** southern Upper Rhine Valley, is sparse plant coverage are preferred characterised by exceptional warm by females for egg deposition (Fig. 3, 80 and dry climatic conditions due to its 4) and as habitat by larvae. Larval 60 geographical position (rain shadow habitats are characterised by a high 40 and foehn wind from the Vosges, proportion of stones or open soil. adjacency to the Belfort Gap). Fig. 3: A typical larval habitat of H. fagi in 20

Herb layer coverage [%] coverage layer Herb random sites Kaiserstuhl vineyard slopes. (V. Möllenbeck 08.05.2005) oviposition sites 0 Fig. 4: Herb layer coverage at egg deposition n = eggs 52 31 sites and random sites. (Mann-Whitney-U-Test *** P < 0.001)

ƒ Host plant structure – Sturdy grass 25 - 30 larvae sites (n = 49) random sites (n = 100) ** tufts with high amounts of litter are 20 - 25 ** preferred by larvae (Fig. 5), the 15 - 20 ** same has been documented for 10 - 15 **

ovipositing females. height [cm] 5 - 10 *

0 - 5 n.s. Fig. 1: Vineyard slopes comprising dry grasslands Fig. 5: Vegetation coverage in different heights 0 20406080100 (brownish; in parts larval habitats of H. fagi) and at larvae sites and at random sites. (Mann-Whitney-U-Test ** P < 0.01, * P < 0.05, n.s. not significant) Vegetation coverage [%] perennial herbs (greenish). (V. Möllenbeck 30.07.2005) Larval habitat parameters determine the combustibility:

** n.s. *** ** ƒ Combustibility – Structural com- 100 structural bustibility of larval habitats is low combustibility 80 due to sparse vegetation cover. Sites OS = oviposition sites used as larval habitat are mostly 60 RS = random sites not / no legally protected grasslands exclu- 40 moderately / - sites [%] sites well / yes (a) (b) ded from fire management (Fig. 6). Fig. 2: H. fagi, (a) an adult larva retrieved in a 20 Fig. 6: Structural combustibility and legal pro- legal B. erectus-tuft during daytime, (b) rare observa- tection of oviposition sites and random sites. protection tion of a female sucking on flowers (here on Ori- 0 (Mann-Whitney-U-Test *** P < 0.001, ** P < 0.01, * P < 0.05, n.s. not OS RS OS RS ganum vulgare). (V. Möllenbeck 02.05.2007, 09.08.2005) significant) Discussion and Conclusions

The open vegetation structure enhances the warm microclimate that is crucial for egg and larval development. The distinct tuft-growth of the host plant provides a suitable habitat for the larvae during hibernation and acts as a secure hide against predation and extreme temperatures during daytime in summer. Vegetation structure also determines combustibility of larval habitats: As larval habitat sites were sparsely vegetated with little available fuel, fire management is not applicable. Thus, burning in winter is not affecting H. fagi-populations within the vineyard slopes.

Related paper – Möllenbeck et al (2008) International Symposium J Conserv DOI 10.1007/s10841-007-9128-z Future of in Europe II E-mail - [email protected] April 2008 – Wageningen, Netherlands