White-Tailed Deer - Influences on Plants:
White-tailed deer populations in Virginia have increased dramatically over the last century; it is estimated that there are almost 36 times the number that were present in the 1930s. These changes are due to land use changes and loss of both predators and hunters. Excessive deer browsing in forests has led to ecological changes by causing a shift in the understory growth. Deer browse is known to prevent the regeneration of important canopy species by depleting tree saplings in the forest understory, this allows unpalatable competitive species to take over as many of the deer preferred species have a hard time recolonizing due to short dispersal distances, long generation times, and resource competition (Goetsch et al., 2011) . This selective deer browsing is responsible for significantly reducing the growth and survival of many native hardwood trees such as oak, hemlock, maple, and dogwood, and also many native wildflower species in the eastern US. Removal of understory vegetation can also increase the spread of invasive species. Deer browse also contributes to the facilitation of invasive species as altered forest floor conditions allow fast growing, shade tolerant invasive to choke out native trees, shrubs, and herbs. Because deer also frequently visit early successional habitats to forage, they also help spread invasives as these habitats are often occupied by high densities of invasive plants which are dispersed to forest edges and interior as the deer travel back and forth (Baiser et al., 2008). |
Photo of a deer exclosure with the deer inaccessible area on the right and the deer accessible area on the left.
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White-Tailed Deer - Influences on Wildlife:
Intense deer browsing also strongly impacts the survival of many forest dwelling wildlife species. Because deer remove forest understory and eat an enormous amount of nuts and fruit, they deplete the resources necessary for many small mammal and mid-story/ground nesting bird species to survive. McShea & Rappole, 2000). |
Fire-Suppression & Smokey the Bear: European colonization brought frequent high-intensity fires to the land as the settlers burned and cleared forests at a high rate. These fires continued into the mid 20th century and because they were so frequent and severe, fire intolerant species like American beech and maple were being restricted to only moist and protected areas (Small & Chamberlain, 2015). Around this time, fire suppression campaigns started in response to concern about the effects of unregulated fires on the landscape and they worked. The fire prevention efforts almost completely eliminated human-caused and natural fires for 100 years, causing a number of changes to the land. In forests, fire-dependent species began to be replaced by fire-sensitive species and forest under-stories became cool and more shaded which allowed for the establishment of more shade-tolerant species (Small & Chamberlain, 2015). Savannahs and grasslands, once formed and maintained by periodic fire, turned into closed canopy forests. |
Fire Suppression & "Mesophication":
Today, we are still feeling the effects of the “Smokey the Bear” era as we are seeing a shift in forest species abundance and diversity due to the effects of fire suppression. Fire sensitive species such as red maple, tulip poplar, and loblolly pine are being regenerated more than oaks and other fire loving species (Vose & Elliot, 2016). This new generation of fire-intolerant species creates a more dense canopy, causing the development of cool and moist under-story conditions; this process is referred to as "mesophication". Mesophication is an issue for forest ecologists as they try to restore the natural fire balance within forests and promote the regeneration of fire-dependent species through prescribed burns because, at this point, some forests are experiencing decreased flammability due to the humid and cool conditions. (Small & Chamberlain, 2015). With forests changing in tree composition, other environmental changes follow; soil, hydrology, and climate reactivity are all affected. |
Dry-mesic oak forests (147-2, 56-1, 8-9, 47-1, and 12-1) at Wildwood Park are currently dominated by tree species such as red oak (Quercus rubra) and eastern redbud (Ceris canadensis). As previously documented, the red oak is the one tree among the rest of these documented species that grows to become largest on the DBH scale. The next most dominant tree species is eastern redbud. This tree's young population is large but do grow into somewhat larger DBH classes for its species. In the future, it is likely that the eastern redbud will remain dominant but also the red cedar (Juniperus virginiana), flowering dogwood (Cornus florida), sugar maple (Acer saccharum), and the american hophornbeam (Ostrya virginiana) will be dominant as well due to being very prevalent in the lower DBH size trees. This means that although these species growth readings are restricted to the lower end of the DBH scale, their population numbers are on the higher end of the chart. With strong numbers among the smaller trees of these other species, we can draw the conclusion that future dominance over this type of forest will rest with them. |