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|Objectives of a County Flora||Location of Madison County||Geology|
|Species Endemic to Texas||Invasive Non-Native Species||Summary of Results|
|Background Information||Amanda K. Neill||Botany at Texas A&M University (Botany 301 site)|
click here to see images of the Madison County flora
(Generates an automatic query for "Madison" on the TAMU Vascular Plants Image Gallery)
1. To collect,
and preserve specimens of all vascular plants occuring in a county
2. To generate a species list for the county and delineate patterns of plant communities by habitat preference
3. To analyze the flora for notable range extensions, recent invaders, and endemic or rare taxa
County floras play an important role in preserving information about the species composition of a known area at a particular time. The true geographic range of many species in the United States is unknown. The distribution of species changes as environments change, and if no one is appointed to focus their attention on these changes, we will have an incomplete understanding of the natural world as it affects us and is affected by us. Not only must the members of endangered plant communities be recorded before they are disturbed or obliterated, but botanists are responsible for alerting the public to the movement of invasive non-native species. Unfortunately, the county flora is a labor-intensive and time-consuming project, and many counties in Texas (and other states) lack a concentrated floristic study. I encourage students of botany to find such a county nearby, and dedicate yourselves to this under-publicized method of becoming a better botanist while producing an important record of your research.
The geology of this part of eastern Texas is the product of alluvium washed southward by rivers and deposited in layers by the advancing and retreating coastal waters during the Eocene Epoch (58-37 mya) of the Tertiary Period. The Eocene layers deposited in Madison County are members of the Claiborne Group and are composed of clays, claystones, shales, siltstones, sandstones, and lignite. Along the larger creeks and rivers, Pleistocene (2 mya-10,000 ya) fluvial terraces of distantly-derived sands, clays, and gravel were deposited during high-moisture periods of the last ice age. Recent, more locally-derived Holocene (10,000 ya-present) alluvium covers modern floodplains in the county. (See soils map below)
In the map above, the pink, orange, medium blue, and purple soils are terraces deposited by the rivers bordering the county. The green soils are alluvium deposited by the smaller tributaries. The light blue, dark blue-grey, yellow, and tan soils are older soils directly derived from the underlying geology of the county. Generally, these are clays and sandy clays.
Map from Neitsch, C.L. 1994. Soil survey of Madison County, Texas. U.S.D.A., Soil Conservation Service, Wash., D.C.
The above map represents historical vegetation patterns in Madison County, which supports three of the ten vegetation types found in the state of Texas. The Blackland Prairies are true prairies with fertile calcareous soil and dominant grasses such as Little Bluestem and Indian Grass. Tree species found along waterways include a variety of oaks, hickories, and elms. No intact, undisturbed prairies are preserved in Madison County, but patches of prairie-like habitats exist along some roadsides and in other areas protected from overgrazing. The Post Oak Savannah is a zone of deciduous hardwoods, namely Post Oak, Blackjack Oak, and Winged Elm, interspersed with open grassy areas. Common understory shrubs are Yaupon Holly and American Beautyberry. The majority of upland Post Oak Savannah in Madison County had been cleared in the past for farming, but the county has become more heavily wooded in the last 50 years. The Pineywoods of east Texas represent the highest rainfall area in the state, and are characterized by forests of Loblolly Pine, Sweetgum, oaks, and hickories. Farkleberry and Sassafras are common understory species.
Map adapted from Gould, F.W., G.O. Hoffman, and C.A. Rechenthin. 1960. Vegetational areas of Texas. Texas Agric. Exp. Sta. Bulletin 1070.
|Cucurbita pepo var. texana||Krigia gracilis||Lechea san-sabeana|
|Liatris cymosa||Lupinus subcarnosus||Lupinus texensis|
|Palafoxia rosea var. rosea||Senecio ampullaceus||Spiranthes parksii|
Ten species in the flora are endemic (restricted)to Texas. Liatris cymosa (Branched Gayfeather) is restricted to approximately six counties in southeast Texas. Although its restricted range places it in danger of extinction, this species is not under review for federal listing. Spiranthes parksii (Navasota Ladies'-tresses Orchid) was listed as federally rare and endangered in 1982, and is restricted to approximately eight counties in southeast Texas. For more information about species endemic to Texas, see the Flora of Texas Consortium's Vascular Plants Endemic to Texas website.
148 non-Texas-native taxa
found in the county, or almost 14% of the total taxa in Madison
The majority of these are roadside and pasture weeds, favored by
and occasionally introduced for forage. There are some crop waifs
that are found along roadsides, as well as horticultural introductions
persisting at old home sites. A number of species were found in
county that are either well-known invaders, or new arrivals (marked
*) that appear to be future threats. A selection of these is
below. Grass species are the worst invaders and displacers of
species, but are usually introduced purposefully. These are too
to list, but the worst offenders are Bermuda Grass (Cynodon dactylon)
and species of Paspalum.
|Ailanthus altissima-- Tree of Heaven*||Albizia julibrissin-- Mimosa|
|Alternanthera philoxeroides-- Alligator-weed*||Ligustrum sinense-- Chinese Privet|
|Lonicera japonica-- Japanese Honeysuckle||Lygodium japonicum-- Japanese Climbing Fern*|
|Melia azedarach-- Chinaberry||Petrorhagia dubia-- Childling Pink*|
|Rosa multiflora-- Japanese Rose||Sapium sebiferum-- Tallow-tree|
|Vicia lutea-- Yellow Vetch*|
Links to great sites focusing on invaders:
for Aquatic and Invasive Plants
Weeds Gone Wild
The Nature Conservancy Wildland Invasive Species Program
Vascular plants were collected in Madison County from 1996-2000, resulting in a total of 2,254 specimens. The flora totals 1,071 taxa (including subspecies and varieties) in 994 species, with 469 genera and 121 families. One species, Vicia lutea (Yellow Vetch), was found to be new to Texas.
The five largest plant families in the flora are Poaceae (grasses) (134 species), Asteraceae (composites) (130 sp.), Fabaceae (beans in the strict sense) (74 sp.), Cyperaceae (sedges) (63 sp.), and Euphorbiaceae (spurges) (32 sp.). These families comprise approximately 44% of the species found in Madison County.
Partial funding for this project was supplied by the Department of Biology and the Office of Graduate Studies at Texas A&M University. Many thanks to the landowners and leaseholders of Madison County for your participation in this research!
The interested reader is referred to the author's thesis, which should be available in both the Sterling C. Evans Library on the A&M campus and the Madisonville Public Library by early 2001.
Questions should be addressed to the author, or to the curator of the TAMU Herbarium, Dr. Hugh Wilson.
Last revised by Amanda
K. Neill, 18 June 2000.
resurrected 1-31-07 10:27