自然保护与休闲部保护·守护·共享
自然保护与休闲部
Due to the expected impact of the winter storm, all Virginia State Park overnight facilities will be closed from Friday, Jan. 23 through Tuesday, Jan. 27. This decision is based on the forecast for unsafe conditions and potential power outages. For updates click here.
目录山地干旱和干旱中生石灰质森林
该组主要覆盖山地混合硬木森林，其中橡树占很大一部分，出现在石灰岩、白云岩上，较少出现在最钙质的页岩、粉砂岩和砂岩上。该群落栖息于地势多样、土壤肥沃的半湿润至相当干旱的山坡和山顶。分类的群落类型沿着地理、土壤湿度、土壤深度和坡向的交叉梯度分离，大致可分为“干旱”和“干旱中生”群落。
Dry calcareous forests occur on subxeric to xeric, fertile habitats over carbonate formations of limestone and dolostone, or very rarely highly calcareous siltstone or shale. Habitats are steep, usually rocky, south- to west-facing slopes at elevations from < 300 to 900 m (< 1,000 to 2,900 ft). Soils vary from circumneutral to moderately alkaline and have high calcium levels. Confined in Virginia to the mountains, these communities are most frequent and extensive in the Ridge and Valley, but occur locally in both the Blue Ridge and Cumberland Mountains. Tree canopies vary from nearly closed to quite open and woodland-like. Overstory mixtures of chinquapin oak (Quercus muehlenbergii), sugar maple (Acer saccharum), black maple (Acer nigrum), northern red oak (Quercus rubra), white oak (Quercus alba), Shumard oak (Quercus shumardii), white ash (Fraxinus americana) and blue ash (Fraxinus quadrangulata, extreme southwest Virginia only) are typical. These forests and woodlands share many understory and herbaceous plants with the Piedmont / Mountain Basic Woodlands group and are similarly species-rich. A few of the taxa that are confined to or most important in the limestone and dolostone communities include Carolina buckthorn (Frangula caroliniana), round-leaved ragwort (Packera obovata), robin's-plantain (Erigeron pulchellus var. pulchellus), American beakgrain (Diarrhena americana), slender muhly (Muhlenbergia tenuiflora), black-seed ricegrass (Patis racemosa), limestone purple sedge (Carex purpurifera, in extreme southwestern Virginia only), hairy sunflower (Helianthus hirsutus), small-headed sunflower (Helianthus microcephalus), northern leatherflower (Clematis viorna), and white death-camas (Anticlea glauca). Logging and fire exclusion are probably the biggest threats to dry calcareous forests.
Dry-mesic calcareous forests occur in deeper soils of valley sideslopes, lower mountain slopes, gentle crests, and ravines up to about 1,150 m (3,800 ft) elevation. Forests of this group are widely distributed in the Ridge and Valley province, more local in the Cumberland Mountains, and rare in the northern Piedmont Triassic Basin. Mixtures of sugar maple (Acer saccharum), black maple (Acer nigrum) , chinquapin oak (Quercus muehlenbergii), white oak (Quercus alba), northern red oak (Quercus rubra), black oak (Quercus velutina), white ash (Fraxinus americana), and hickories (Carya spp.) are typical. A distinctive variant is co-dominated by eastern white-cedar (Thuja occidentalis), usually in association with eastern white pine (Pinus strobus), eastern hemlock (Tsuga canadensis), and hardwoods. Tulip-tree (Liriodendron tulipifera) is most abundant as an invader of logged stands. Understory and herbaceous vegetation varies from sparse to lush (especially on limestone sites), but is generally dominated by species characteristic of submesic soil moisture conditions, such as white snakeroot (Ageratina altissima var. altissima), hog-peanut (Amphicarpaea bracteata), common eastern bromegrass (Bromus pubescens), sharp-lobed hepatica (Hepatica acutiloba), and common black cohosh (Actaea racemosa).
干燥中生石灰质森林很容易与富饶的山谷和斜坡森林或基本中生森林区分开来，因为它们出现在保护较少的地区，并且没有突出的中生草本植物，例如蓝升麻（ Caulophyllum thalictroides ）、阔叶水叶（ Hydrophyllum canadense ）或木荨麻（ Laportea canadensis ）。许多干旱中生石灰质森林因农业用途而被大量砍伐或破坏。在某些情况下，这些林分似乎是由于中生树种（尤其是糖枫）入侵橡树山核桃林而形成的，这可能是由于长期防火所致。白蜡树是干旱和干旱中生石灰质森林中一种非常常见的伴生树种，目前由于翡翠灰螟的爆发，白蜡树正在经历大量死亡。
参考文献：Fleming ( 1999 )、Fleming 和 Coulling ( 2001 )、Fleming 和 Moorhead ( 1996 )、Fleming 和 Moorhead ( 2000 )、Rawinski 等人 ( 1996 )。
© DCR-DNH，加里·P·弗莱明。
102定量地块样本支持七种群落类型（图1 ）。大多数单位的分类相当可靠，但仅在坎伯兰山脉和南部山脊与山谷中发现的三种类型的完整分布和状态尚不清楚，需要额外的清查。单击下面任何突出显示的 CEGL 代码即可查看NatureServe Explorer 提供的全球 USNVC 描述。
下载下面列出的每个社区类型的组成汇总统计电子表格。
