Abundance of Migratory and Wintering Geese in Relation to Vegetation Succession in Man-Made Wetlands: The Effects of Grazing Regimes

[摘要] Theman-madewetlandsinyoungpoldersinTheNetherlandsareimportantstopoverandwinteringsitesforgeese.Westudiedtrendsinvegetationcompositionandgoosedensityintwostudyareas.Onewaslocatedinanaturereservesituatedinapolderreclaimedfromanestuary,theotherinareserveinapolderreclaimedfromafreshwaterlake.Intheformerwecomparedanareaofspontaneousvegetationsuccessionwithasummer-grazedarea.InthelattertheeffectofreedPhragmitesaustraliscoverandheightonfieldselectionofgeesewasstudiedinanareagrazedyear-roundbycattleandhorses.Inbothstudyareastheareaofshortgrassland(reedcoverabout1%,reedheightlt;0.5m)wasfoundtobesignificantlypositivelyrelatedtothegrazingdensityofcattleandhorses.MigratingandwinteringGreylagGeeseAnseranserandBarnacleGeeseBrantaleucopsispreferredtofeedontheseextensiveshortgrasslands.Intheungrazedpartofthestudysiteinthereclaimedestuarinearea,therewasaninverserelationbetweengoosedensityandtheoustingofpioneerspeciesofsalinehabitatsandshortgrassesbytallspeciessuchasCalamagrostisepigejos,Phragmitesaustralis,tallherbsandshrubs.Summergrazingbycattleandhorsesatstockingratesofabout0.4to0.9animals/ha,retardedthevegetationsuccessiontosomeextent,whichresultedinagoosedensitybeinghigherinthesummer-grazedareathanintheungrazedarea.Theimplicationsformanagementarethatthemoredesalinatedtheareabecomesandthehigheritsclaycontent,thehigherthestockingratemustbetoretardthevegetationsuccession.

[学科分类] 动物科学

[关键词] Branta Leucopsis