Matthies Diethart, Egli Philipp
Institut für Umweltwissenschaften, Universität Zürich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland e-mail: matthies@ uwinst.unizh.ch, Tel.: +41-1-6354806, Fax: +41-1-6355711, , , , , , CH.
Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft (WSL), CH-8903 Birmensdorf, Switzerland, , , , , , CH.
Oecologia. 1999 Jul;120(1):156-161. doi: 10.1007/s004420050844.
Although elevated CO may affect various forms of ecological interactions, the effect of elevated CO on interactions between parasitic plants and their hosts has received little attention. We examined the effect of elevated CO (590 μl l) at two nutrient (NPK) levels on the interactions of the facultative root hemiparasite Rhinanthus alectorolophus with two of its hosts, the grass Lolium perenne and the legume Medicago sativa. To study possible effects on parasite mediation of competition between hosts, the parasite was grown with each host separately and with both hosts simultaneously. In addition, all combinations of hosts were grown without the parasite. Both the parasite and the host plants responded to elevated CO with increased growth, but only at high nutrient levels. The CO response of the hemiparasite was stronger than that of the hosts, but depended on the host species available. With L. perenne and M. sativa simultaneously available as hosts, the biomass of the parasite grown at elevated CO was 5.7 times that of parasites grown at ambient CO. Nitrogen concentration in the parasites was not influenced by the treatments and was not related to parasite biomass. The presence of the parasite strongly reduced both the biomass of the hosts and total productivity of the system. This effect was much stronger at low than at high nutrient levels, but was not influenced by CO level. Elevated CO did not influence the competitive balance between the two different hosts grown in mixture. The results of this study support the hypothesis that hemiparasites may influence community structure and suggest that these effects are robust to changes in CO concentration.
虽然二氧化碳浓度升高可能会影响各种形式的生态相互作用，但二氧化碳浓度升高对寄生植物与其寄主之间相互作用的影响却很少受到关注。我们研究了在两种养分（氮磷钾）水平下，二氧化碳浓度升高（590 μl/l）对兼性根半寄生植物高鼻花与两种寄主——黑麦草和紫花苜蓿之间相互作用的影响。为了研究对寄主间竞争的寄生介导可能产生的影响，将寄生植物分别与每种寄主一起培养，以及与两种寄主同时培养。此外，所有寄主组合都在没有寄生植物的情况下培养。寄生植物和寄主植物均对二氧化碳浓度升高作出反应，生长加快，但仅在高养分水平下如此。半寄生植物对二氧化碳的反应比寄主更强，但这取决于可利用的寄主物种。当黑麦草和紫花苜蓿同时作为寄主时，在二氧化碳浓度升高条件下生长的寄生植物生物量是在环境二氧化碳浓度下生长的寄生植物的5.7倍。寄生植物中的氮浓度不受处理影响，且与寄生植物生物量无关。寄生植物的存在强烈降低了寄主的生物量和系统的总生产力。这种影响在低养分水平时比在高养分水平时更强，但不受二氧化碳水平影响。二氧化碳浓度升高并未影响混合种植的两种不同寄主之间的竞争平衡。本研究结果支持半寄生植物可能影响群落结构这一假说，并表明这些影响对二氧化碳浓度变化具有较强抗性。
