|
Grasslands Habitats
草原生態(Chinese)
The grasses in agriculture grasslands
are not native ones; they are species that were brought from northern Europe, where the climate is similar. Like cultivated crops or garden flowers, they have been the object of extensive experimentation on the
part of plant breeders. New varieties, which have particular traits to suit particular situations, are constantly being introduced.
Few flowers appear in a meadow early in the spring, but from late
spring through fall, many wild flowers--both alien and native--grow interspersed with the grasses. These include hawkweeds, milkweeds, Oxeye Daisy, lupines, vetches, and goldenrods.
On an intensively used meadow, the grasses are usually planted along with a legume, either a clover or Alfalfa. This practice has been in effect for centuries (the first documented case occurred in 1613). The legumes enrich the
soil by fixing atmospheric nitrogen into a form that plants can use; they also provide a high protein forage when they are cut and dried. The grasses in a pasture are similar to those in a meadow, but the wildflower component in a
pasture is likely to be different, since most wild flowers get cropped.
When eastern meadows and pastures are deserted, they begin to undergo the process of succession, which is the
changing of species composition and dominance over time. Such abandoned, or old, fields may initially be dominated by any of a number of species--often clone-forming wild flowers such as milkweeds or goldenrods, which
spread by rhizomes and form persistent patches. In the next stage, old fields are generally characterized by grasses.
An old field can also evolve from abandoned cropland--that is, on bare soil. On such sites, "weeds"--annual grasses
and annual or perennial forbs--usually dominate for several years before the perennial grasses become established.
The grasses are inevitably replaced by trees. The invading tree species also vary, but there is nonetheless a predictable zonation of old field invaders from north to south. The length of time necessary for a tree invasion to
take place varies. In the North, trees also appear within a few years, but decades will pass before a full cover is established. As the a hardwood forest grow, the grasses die because of shade and root competition, and the tree
stand is eventually established. When the pioneer trees die or are cut, the conifers take over. Once a conifer forest
is established, it tends to maintain itself unless struck by catastrophic disturbances, such as fire, a wind storm, or insect infestation.
草原生態(Grassland)
最近自然歷史步行導覽活動
最近綠色文化生態旅遊活動
草原與草原溼地內，長滿許多青草(Grass)，燈心草(Rush)
，雖然到處是枯黃的野草，成熟的野草果實與肥後的根部卻是許多野鼠、昆蟲與青蛙的棲息地。他們努力的覓食與儲藏食物以便度冬，在野草地下隨處可見他們的隧道。但隨著野草的枯死，野鼠的行蹤就更難逃過如紅尾鷹、粗腿鷹(Rough-legged Hawk)、白臀鷹(Harrier) 等猛禽類的銳利眼光。偶而可見遊隼(Peregrine Falcon)與灰背隼(Merlin) 來此獵食。堤防邊緣的樹叢與草叢中，可以找到各種麻雀(Sparrow)
、美洲麻鷺(Bittern)、溼地鷦鷯(Wren)、短耳貓頭鷹(Owl)
。
這裡最常見的鳥類包括各種覓食種子的棕頭牛鸝(Cowbird)、紅翅黑鳥(Blackbird)、美洲金雀(Goldfinch)、椋鳥(Starling)、岩鴿
(Dove)、環頸雉(Pheasant)、西部與東部帝王鳥(Kingbird)。金冠雀(Sparrow)、白冠雀、狐雀、歌雀，黑眼燈草雀(Junco)、紅翅黑鳥(Blackbird)、叢山雀(Bushtit)、黑頭山雀(Chickadee)、紅頭家雀(Finch)、松金翅(Siskin)
、棕脅唧雀(Towhee)、鷦鷯(Wren)
、岩鴿(Dove)、撲動鴷(Flicker)、絨毛啄木鳥(Woodpecker)。
還有覓食昆蟲的樹燕、紫綠燕、粗翼燕、崖燕、穀倉燕子(Swallow)、知更鳥(Robin)、蠟翅鳥(Waxwing)
、黃鶯(Warbler)、斑點唧雀(Towhee)
、鷦鷯(Wren)、雨燕(Swift)、蜂鳥(Hummingbird) 、絨毛啄木鳥(Woodpecker)、捕蚊鳥(Flycatcher)、烏鴉(Crow)
、黑頭山雀(Chickadee)、叢山雀(Bushtit)
。還有大藍鷺(Great Blue Heron)在捕捉老鼠。
冬季草地上可見美洲鴛鴦(Wood Duck)、綠頭鴨、尖尾鴨(Pintail)、綠翅鴨、美洲赤頸鴨、環頸雉雞(Pheasant)、雙領濱鳥(Killdeer)、海鷗(Gull)，以及常見的加拿大雁(Canada Geese)覓食穀類與青草。田野上空常見白頭鵰 (Bald Eagle) 、白尾鷹(Harrier)、以及紅尾鷹(Hawk)。
幾種瀕臨絕種，或遭受危害的猛禽鳥類，包括如綠鷺(Green Heron)，白頭鵰 (Bald Eagle)，穀倉貓頭鷹(Barn Owl)，短耳貓頭鷹 (Short Eared Owl)、北方伯勞鳥 (Shrike)、粗腿鷹(Rough-legged Hawk) 、白尾鷹(Harrier)以及紅尾鷹(Hawk)。這�(Coyotes)
、浣熊 (Raccoon)、水瀨 (Beaver)
、貂(Mink)、麝香鼠(Muskrat)。生態學家也曾發現棕色蠑螈 (Salamander)，這是最低海拔的生存記錄。
|
