Rowcliffe J Marcus, Watkinson Andrew R, Sutherland William J
Schools of Biological and Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK email: a.
Oecologia. 1998 Apr;114(3):417-426. doi: 10.1007/s004420050465.
The aggregative responses and habitat preferences of a generalist herbivore, the dark-bellied brent goose Branta bernicla bernicla, feeding on salt marshes are examined in relation to vegetation community characteristics and the abundances of individual plant species. In the autumn, feeding was strongly concentrated on the low marsh, which had the highest biomass of the preferred food plant, Salicornia europaea. There was a strong aggregative response of the geese to the abundance of S. europaea. A decline in the availability of S. europaea led to an increase in the pattern of aggregation in relation to the two other major food plants on the low marsh, Aster tripolium and Puccinellia maritima. The availability of these food plants, however, reached critically low levels in mid-winter and the geese abandoned the low marsh for the high marsh. Within the high marsh, the plant communities selected tended to be dominated by the inedible species Limonium vulgare. The food plants selected were P. maritima in the winter and P. maritima and Triglochinmaritimum in the spring. On the high marsh, aggregative responses were shown to both P. maritima and T. maritimum, but in both cases, aggregation increased up to a critical level of biomass, and then declined. The prevention of grazing with exclosures for 3 years led to an increase in the abundance of P. maritima on both high and low marshes. This change was slight on high marsh but pronounced on low marsh, where S. europaea showed a decrease in abundance in the exclosures over this time. The implications of the aggregative responses for the population dynamics of P. maritima and S. europaea are discussed.
本文研究了以盐沼为食的广食性食草动物——黑腹白额雁（Branta bernicla bernicla）的聚集反应和栖息地偏好，以及它们与植被群落特征和个别植物物种丰度之间的关系。秋季时，觅食活动主要集中在低沼地，这里是首选食物植物欧洲海蓬子（Salicornia europaea）生物量最高的地方。黑腹白额雁对欧洲海蓬子的丰度有强烈的聚集反应。欧洲海蓬子可获取量的下降导致与低沼地其他两种主要食物植物——海紫苑（Aster tripolium）和碱茅（Puccinellia maritima）相关的聚集模式增加。然而，这些食物植物的可获取量在冬季中期降至极低水平，黑腹白额雁于是离开低沼地前往高沼地。在高沼地内，所选的植物群落往往以不可食用的物种——补血草（Limonium vulgare）为主导。所选的食物植物在冬季是碱茅，春季是碱茅和海三棱藨草（Triglochin maritimum）。在高沼地，黑腹白额雁对碱茅和海三棱藨草都表现出聚集反应，但在这两种情况下，聚集程度都随着生物量达到临界水平而增加，然后下降。用围栏阻止放牧3年导致高沼地和低沼地的碱茅丰度都有所增加。这种变化在高沼地很轻微，但在低沼地很明显，在此期间，围栏内的欧洲海蓬子丰度有所下降。本文还讨论了聚集反应对碱茅和欧洲海蓬子种群动态的影响。
