Vine leaf decomposition: Feeding preferences and effects of physico-chemical traits of litter on life-history traits of the woodlice Armadillidium vulgare Latreille, 1804

Abstract

Litter decomposition is a key ecosystem process which is dependent on the litter characteristics and diversity, the decomposer community and activity, and the environmental conditions. We assessed vine leaf decomposition by Armadillidium vulgare (Latreille, 1804), a terrestrial isopod widely distributed and naturally present in vineyards. We compared the decomposition of three grape varieties (Chardonnay, Pinot Noir and Sauvignon) with regular laboratory food (Tilia tomentosa (Moench, 1785)) for seven consecutive weeks. Seven traits were measured on the four litters tested in order to define their importance concerning (i) litter mass loss by the action of microorganisms and isopods (ii) the trophic traits (consumption and assimilation) and (iii) life-history traits (survival and growth) of A. vulgare. Thus, the chemical and physical traits (C/N ratio, tannin and fiber content, thickness) known to influence litter palatability and digestibility for decomposers were determined by standardized methods. In addition, the copper frequently used in viticulture as a fungicide which is potentially responsible for toxic effects on decomposers was measured by ICP-OES after litter mineralization in nitric acid. Our results showed a higher percentage of decomposability by microorganisms in litter with low cellulose content and C/N ratio. Higher isopod consumption and assimilation was found in the litters which is the poorest in tannin, lignin and copper contents. Variation of consumption according to litter was on average 1.5 to 2.7 lower for grape varieties compared to T. tomentosa litter. Assimilation was significantly lower with Pinot Noir than the other litters. To conclude, after seven weeks of experimentation, this study showed that if the growth and survival of woodlice were not affected by inter-varietal differences in vine leaf quality, their role in the decomposition process may be strongly modulated and reduced, especially after consumption of grape variety litters rich in copper, lignin and tannin.