THE EFFECTS OF INCREASING CO2 AND TEMPERATURE ON OAK LEAF PALATABILITY AND THE IMPLICATIONS FOR HERBIVOROUS INSECTS

Rising levels of atmospheric CO2 are expected to perturb forest ecosys tems, although the extent to which specific ecological interactions wi ll be modified is unclear. This research evaluates the effects of elev ated CO2 and temperature, alone and in combination, on the leaf nutrit ional quality of Pendunculate oak (Qeurcus robur L.), and the implicat ions for herbiverous insect defoliators are discussed. A 3 degrees C t emperature rise reduced leaf nutritional quality, by reducing foliar n itrogen concentration and increasing condensed tannin content. Doublin g atmospheric CO2 temporarily increased total phenolics, but also redu ced leaf toughness. The nutritional quality of the second leaf flush ( lammas growth) was considerably reduced at elevated CO2. It is conclud ed that larval development of spring-feeding defoliators and hence adu lt fecundity may be adversely affected by increased temperatures.