Some papers state that Indiana was 90% forest & only 10% open wetlands & prairie & barrens/savanna in 1800. However, land surveys indicate that it was more like 67% forest & 33% open wetlands & prairie & barrens/savanna in 1800. Granted, there were dense forests of massive +300-year old trees, but there was consirable open woods & space caused by grazing animals & Native American burning.
The densest, most impressive forests in the state were located in southeastern Indiana & southwestern Indiana where density, height & tree girth was equal or exceeds current old-growth, virgin rainforest in central & South America. Record tree heights & girth for the Midwest were recorded. However, all forest areas of the state had +100' & massive trees from the hills of south-central Indiana to the forests of parts of the Tipton Till Plain in central Indiana to the great forests of the upper Wabash & then the Black Swamp of eastern Allen County.
A limestone plain riddled like swiss cheese with sinkholes was formerly prairie & barrens from northeastern Orange County, Indiana to northern & central Harrison County, Indiana. This limy plain of barrens & prairie then extended through south-central Kentucky to as far south as Clarksville, Tennessee & Fort Campbell. In Indiana it is known as the Mitchell Karst Plain, "The Barrens", in Kentucky "The Pennyroyal" or "Big Barrens" & also the "Green River Plains" & in northern Tennessee, "The Barrens".
Once a fire started on this plain, it could burn until rain returned. It is flat to gently rolling & lacks surface streams. All of the drainage is subterranean or the water seeps through like swiss cheese into caves. Thus, it is well-drained & dries very quickly. There are & were instances, however, of sinkholes (limestone underneath the soil collapses due to naturally-acidic rainwater dissolving the limestone) reaching the water table underneath or the sinkhole becoming clogged by debri & thus becoming a wetland. Sometimes, shallow ponds would even develop. There are instances of ponds & wetlands disappearing overnight as a sinkhole becomes unclogged & the water drains.
Note the swiss cheese landscape of sinkholes on the plain as seen here in northeastern Orange County:
More swiss cheese or honeycombs of the karst plain in Indiana with sinkholes & area where the water table is closer to the surface highly-visible in aerials:
Plugged sinkhole pond in Washington County, Indiana:
Sinkhole in eastern Orange County, Indiana on the edge of Orleans, Indiana:
Sinkhole image, courtesy of Indiana University, showing one sinkhole in a pasture field near Mitchell, Indiana (Hasenmueller and Powell, 2005):
So....why a grassy plain with a scattered trees & shrubs? Animals & Native American-produced fire on firebreak-less plain were the reasons.
Burning of last remnants of original barrens on the plain below.........
According to the U.S. Army:
Marty Wilson, a forester with the U.S. Army Corps of Engineers, creates a fire break along the roadside March 22 at Training Area 48 to assist with a controlled burn. Fort Campbell’s Directorate of Public Works partners with the U.S. Army Corps of Engineers to complete the live burns. (Ethan Steinquest).
Fort Campbell has the largest piece of the original Karst Plain barrens & prairies left.
In Indiana, it is confined to a few patches in pioneer cemeteries, along roadsides, along railroads, fencerows, in pockets in pastures or power-line right-of-ways that aren't farmed.
Harrison County barrens remnant:
South central Kentucky barrens remnant:
Here, the Wildcat, Little Pine & other creeks & their deep ravines were natural firebreaks to prairie & barrens fires in our area. This lead to such a mosaic of forest types, forest in general mixed with prairie, savanna, barrens & groves in our area. The flat, naturally streamless areas of Benton, northwestern Warren, Newton & Jasper to western White counties saw the most prairie in our area. Also, the flat streamless plain due to steady & NOT disconintuous glacial ice melt from Attica to near Tipton led to a belt of solid prairie there.
In this area of Kentucky & over south-central Indiana were several salt licks for large grazers. Great herds would be attracted to the salty licks of salty groundwater in sinkholes or springs or "lost streams" (random trickles or areas of water that appear, then disappear in the cracks in topsoil & limestone). This Mississippian age limestone was part of an inland shallow tropical sea around 350 million years ago & is rich in minerals & still has salty deposits from that ocean. The soils are good for crop production due to their high mineral content (especially phosphorus) & higher pH compared to surrounding areas. Expensive tile drainage for row crop production is not needed due to the subterranean drainage & mineral content & pH decreases fertilizer & lime usage. Thus, the plain is good for pasturage with cool-season grasses & corn to soybean production.
Vast herds of bison are known to have been attracted to the licks & the grasses of the plain & for tens of thousands of years, large mammoths & other such mega-fauna would be attracted to the licks. As late as the early 1800s, each year, vast herds of thge bison would migrate from the "barrens" to the prairies of southwestern Indiana & into Illinois via the Buffalo Trace (Native Americans called the trace "Lananzokimiwi"). So many bison would migrate on the trace that it was said by early settlers that two wagons could easily pass in opposite direction unheeded on the path.
Multiple massive bison wallows still are seen (bison would wallow in the mud to cover their fur & skin to prevent insect bites). Wallows can still be found just southwest of Odon, Indiana (Daviess County) on the former Round Prairie & in the "Buffalo Wallow" 2 miles southwest of Raglesville, Indiana (Daviess County) in an area of forest just 0.5 mile southeast of where the original Round Prairie & Clark's Prairie began. Other wallows on the Buffalo Trace include a wetland area 5 miles north-northeast of Jasper, Indiana (Dubois County), which was a heavily wooded area back in 1800, but that particular area was an open open & marsh, continually distrubed & dug out by bison migration & "wallowing" each year. Other wallows are found in the state, but they are concentrated on the Trace & in the former prairie & barrens areas of the state.
Most early accounts from surveyors & settlers described the area in south-central Indiana as a prairie with typical tallgrass prairie species with "scattered plum, haw & crabapple thickets" & some scattered to small patches of oaks & hickories "not tall enough to hide a man on horseback". Some large areas were completely void of any scrubby tree or thicket growth & had just your typical tallgrass prairie, while others had the prairie vegetation but thickets & even small groves of oaks & hickories on the plain. Most were said to be small & fire-impacted resulting in "poor timber" or "poorly-timbered barrens" or be "scrub oak".
Certainly, the fire regime would have determined how each region of the plain varied in grass, forbs & any shrub/small tree growth over each year or decade. Native Americans continually burned the area to attract the large grazers & the Ice Age grazers were likely attracted to the licks as well with ceremonial burning taking place in autumn & occasionally early spring. The great attraction of Native Americans to the plain for hunting is still found in the caves of the region today. 4,000-year old sandals made of the fibrous prairie plant Rattlesnake Master have been found, in addition to other plant artifacts, as well as cave art depicting bison hunts. Tree ring analysis off old oaks in the Indiana-Kentucky-Tennessee area on this plain indicate fire intervals of 2-5 years.
The warm, dry period known as the "Prairie Period" 5000-8000 years ago (great prairie expansion eastward), the Roman Period (250 BC to 400 AD with booming Native populations & massive burning & prairie expansion) & the Medieval Optimum (warm-dry period 600-900 AD with booming Native populations & massive burning & prairie expansion) also helped to allow prairie & barrens plain to establish there with the burning as native prairie plants left in grassy patches on the surrounding steep hill glades colonized the plain. The dry weather associated with the Ice Age made for a wind-swept, steppe-type climate south of the ice sheet in this area. Pockets of tallgrass prairie & Plains plants migrated as burning commenced & the warm, dry climate periods occurred.
So, it is the topography, past warm, dry periods, Native American burning & populations that led to this seemingly out-of-place prairie & barrens plain amidst a wetter region of the U.S. surrounded by forests & this treeless to area of scattered trees extended to northeastern Orange County, Indiana.
Today, much of the area is farmed or pasture & areas that were barrens or prairie in the early 1800s have grown up into trees. Remnant barrens trees are occasionally found here & there with pockets of haw, crab & plum, some isolated old-growth hickories, Post, Black, Chinkapin, White & Blackjack Oaks with Blue Ash.
It is important to note that the plain become much hillier with increasing streams with northward progression. The area Mitchell, Indiana to Bloomington & Spencer, Indiana was heavily-wooded in 1800, not barrens. Spring Mill State Park would be the northernmost extent of any evidence of the barrens. Several prairie plants are found on the entrace to Donaldson Cave (including the rare Hoary Puccoon) & the rest of the park is timber with a piece of it as original, virgin timber in Donaldson Woods. Donaldson Woods was formerly an oak-hickory forest, but has been trending to Beech-Maple over the past 80 years due to lack of any fire & a wetter climate now compared to the past overall.
Locations of the original barrens:
In typically heavily-wooded south-central Indiana, this plain is an anomaly with scenes more typical of the Illinois Till Plain of southwestern Indiana & the Tipton Till Plain of central Indiana.
Western & Southwestern Washington County, Indiana:
Northeastern Orange County:
The plain & the much hillier, wooded areas in the distance (Karst Plain of west-central Harrison County in former barrens looking west toward Crawford Upland & Shawnee Hills region of south-central Indiana: