We studied the effects of grazing by Black Brant (Branta bernicla nigricans) geese (hereafter Brant) on plant community zonation and gosling growth between 1987 and 2000 at a nesting colony in southwestern Alaska. The preferred forage of Brant, Carex subspathacea, is only found as a grazing lawn. An alternate forage species, C. ramenskii, exists primarily as meadow but also forms grazing lawns when heavily grazed. We mowed plots of ungrazed C. ramenskii meadows to create swards that Brant could select and maintain as grazing lawns. Fecal counts were higher on mowed plots than on control plots in the year after plots were mowed. Both nutritional quality and aboveground biomass of C. ramenskii in mowed plots were similar to that of C. subspathacea grazing lawns. The areal extent of grazing lawns depends in part on the population size of Brant. High Brant populations can increase the areal extent of grazing lawns, which favors the growth of goslings. Grazing lawns increased from 3% to 8% of surface area as the areal extent of C. ramenskii meadows declined between 1991 and 1999. Gosling mass was lower early in this time period due to density dependent effects. As the goose population stabilized, and area of grazing lawns increased, gosling mass increased between 1993 and 1999. Because larger goslings have increased survival, higher probability of breeding, and higher fecundity, herbivore-mediated changes in the distribution grazing lawn extent may result in a numerical increase of the population within the next two decades.

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ABSTRACT. Four caribou (Rangifer tarandus grantii) herds calve on the North Slope of Alaska, three of which have been exposed to little or no resource development. We present 15 years of baseline data on the distribution and movements of 72 satellite-collared and 10 GPS-collared caribou from the Teshekpuk caribou herd (TCH) that have had little to no exposure to oil and gas activities. Fixed-kernel home range analyses of collared caribou revealed that calving grounds were concentrated (i.e., 50% kernel utilization distribution) along the northeastern, eastern, and southeastern shores of Teshekpuk Lake. During the postcalving period, 51% and 35% of caribou moved through two constricted zones to the east and west of Teshekpuk Lake, respectively, and accessed insect-relief habitat along the Beaufort Sea coast. During late summer and early fall, TCH caribou were concentrated to the southeast and southwest of Teshekpuk Lake. Although 65% of the Teshekpuk caribou wintered in two areas on the central coastal plain around the village of Atqasuk and south of Teshekpuk Lake, other TCH animals wintered in a great variety of places, including the Seward Peninsula, the eastern and southern Brooks Range, and the Arctic National Wildlife Refuge. We detected an apparent emigration rate of 6.9%. One male and five female TCH caribou joined the breeding populations of the Western Arctic and Central Arctic herds. TCH caribou traveled an average distance of 2348 ± 190 km annually. Movement rates were at a maximum in midsummer, lowest in winter, and intermediate during spring and fall migrations. Restrictions on oil and gas leasing and surface occupancy have been in place to protect calving, migratory corridors, and insect-relief habitat for the TCH, but these protections are likely to be removed. These data will provide a good baseline that can be used to compare predevelopment distribution and movement patterns of TCH caribou to distribution and movement patterns during and after petroleum development.Key words: Rangifer, satellite-collar, GPS, subsistence, emigration, Alaska, North Slope, National Petroleum Reserve-Alaska RÉSUMÉ. Quatre hardes de caribous (Rangifer tarandus grantii) vêlent sur la côte nord de l'Alaska, dont trois de ces hardes ont été exposées à peu ou pas d'aménagement des ressources. Nous présentons des données de base échelonnées sur 15 ans relativement à la répartition et aux déplacements de 72 caribous dotés d'un collier émetteur par satellite et de 10 caribous munis d'un collier émetteur GPS de la harde de caribous de Teshekpuk (HCT), caribous qui ont été peu ou pas du tout frottés aux activités pétrolières et gazières. L'analyse du noyau fixe des domaines vitaux des caribous à collier a révélé que les lieux de vêlage étaient concentrés (c'est-à-dire 50 % de la répartition de l'utilisation du noyau) le long des côtes nord-est, est et sud-est du lac Teshekpuk. Après la période de vêlage, 51 pour cent et 35 pour cent des caribous se déplaçaient au sein de deux zones de constriction à l'est et à l'ouest du lac ...

Summary 0We investigated the e}ects of grazing by black brant geese on Carex subspathacea lawns on the Yukon!Kuskokwim delta\ Alaska[ 1 We compared variation in growth and forage quality in both grazed and temporarily exclosed sites to determine responses of C[ subspathacea to grazing at landscape scales within two nesting colonies that had experienced di}erent population dynamics over recent decades[ 2 Landscapes di}ered in forage quality\ grazing patterns\ and in the e}ect grazing had on C[ subspathacea forage characteristics[ We found no e}ect of grazing on net above!ground primary productivity "NAPP# over a wide range of natural grazing intensities at the landscape scale[ 3 No di}erences in forage quality\ NAPP\ or response of C[ subspathacea growth rates to grazing pressures could be detected between colonies[ This suggests that goose grazing does not have deleterious e}ects on C[ subspathacea in this ecosystem[ 4 It has been suggested that gosling growth rates are sensitive to seasonal declines in forage availability and quality[ Spatial variation in forage quality and availability per sampled area exceeded seasonal variation in these characteristics and is likely to have dramatic e}ects on gosling growth and recruitment rates[ Keywords] graminoids\ grazing lawns\ plantÐanimal interactions\ salt marsh\ subarctic Journal of Ecology "0887# 75\ 132Ð148

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