Bryophytes and bryology in The Big Thicket National Preserve

The “big thicket” is an entity that is often as difficult to define as it is to delimit.  Throughout the recent history of southeast Texas, the big thicket as a region has taken on several configurations.  The boundaries of these configurations, determined by the needs of the user, differ significantly in their final spatial delineation. 

MacRoberts and MacRoberts (2009) summarize five general delineations of the big thicket compiled from various sources.  These five concepts include: 1) broadest conception (Diggs et al. 2006), 2) biological survey (Parks et al. 1938), 3) ecological area (McLeod 1971), 4) traditional or hunter’s thicket (Diggs et al. 2006), and 5) artificial delineation (Diggs et al. 2006).  Although not included as one of the concepts in the MacRoberts’ list, the National Park Service’s, Big Thicket National Preserve (BITH) is clearly located within the actual, or theoretical, boundaries of each of these definitions. 

The BITH is undoubtedly one of the more familiar concepts recognized by the general public, and is the only definition with discrete boundaries, albeit political in nature.  As pointed out by numerous authors (Gunter 1993; Abbott et al. 1997; Watson 2006) the big thicket has long been referred to as a biological crossroads, where the flora and fauna of several differing ecoregions converge.  It is this unique biodiversity that was the impetus for many decades of efforts to protect and conserve what remains of the original big thicket, however it is defined.  Originally set aside in October of 1974 the BITH was designated the nation’s first preserve (Owens 1978), as opposed to a national park or monument, with the expressed purpose “to preserve the area of rich biological diversity where the eastern hardwood forests, the southern coastal wetlands, the western prairies, and the arid southwest converge” (National Park Service 2013).  As such, the sites selected for inclusion in the original BITH were chosen to be representative of the different habitats found in the broader region rather than one contiguous ecosystem (Owens 1978; Peacock 1994; Diggs et al. 2006).

The Big Thicket National Preserve is located in the extreme southeast corner of Texas and is composed of nine land units interconnected by a series of six river or creek water units. The land units, ranging from 10,000 to 222 hectares, are contiguous tracts of land spread out across seven counties in the region.  The water units are perennial creek, bayou, or river corridors that connect all but three of the units into a widespread, but more or less continuous, network of preserved lands.  The Loblolly, Hickory Creek Savannah, and Beech Creek Units are not currently interconnected within this network.  At present the BITH as a preserve is 40,468 hectares and is located in the east Texas Pineywoods ecoregion and within the West Gulf Coastal Plain of the United States.  The dominant vegetation in the region is mixed pine-hardwood forests on the uplands and mixed hardwood forests in the bottomlands.  In the southern portions of the region, near the Beaumont Unit, the typical coastal plain prairies become more evident.  Annual precipitation in the region is between 122 and 142 cm; mean annual temperatures are between 19 and 21 degrees celsius (Hatch et al. 1990; Diggs et al. 2006).  Additional details of BITH soils and geology can be found in Deshotels (1978) and Aronow (1981). 

Floristic Bryology in the Big Thicket Region

The earliest interest in the biodiversity of the big thicket region was undoubtedly from a utilitarian perspective, largely by Native Americans and early Spanish explorers.  Unfortunately, neither left written records of their observations or perspectives in the region (Gunter 1993).  Post-Spanish exploration in the region was also the focus of the timber and oil industries which continues to the present day.  Early recorded accounts of the region’s biodiversity focused on rather broad descriptions of the current land use, economic resources, principal vegetation, and topography.  Several authors (Planck 1892; Gow 1904; Harper 1920) included various listings of the floral and faunal components observed in the region, although these were brief and woefully incomplete.  Parks et al. (1938) and Parks (1938) assembled what could be the first inclusive listing of plant and animal species in the region.  Contemporary research into the vascular flora is well presented in a series of reports focusing on a unit by unit inventory of the BITH (MacRoberts et al. 2002; Brown et al. 2005, 2006a, 2006b, 2008a, 2008b, 2009, 2010; Haile & Hatch 2013).  However, one common theme in all previous reports is a complete lack of focus on the non-vascular plants (specifically bryophytes) found within the region. 

Although Gow (1904), Harper (1920), and Planck (1892) make passing mention of the mosses or Sphagnum bogs each observed, and Parks et al. (1938) and Parks (1938) stress the need for inclusion of these groups, none provide any listing of bryophytes found in the region.  A number of national and regional publications have lengthy lists of bryophytes, many of which are found in Texas although most of these only provide distribution data to the state or county level (McAllister et al. 1932; Frye & Clark 1937, 1943, 1945, 1946, 1947; Grout 1928-1940; Whitehouse 1954; Whitehouse & McAllister 1954; Flora of North America Editorial Committee 1993+).  In more recent decades reports of bryophytes for the region and the BITH are few and consist of occasional reports of species as new to the state or region (Ellison 1963, 1964, 1964a, 1967; Mueller & Magill 1979).  The first relatively comprehensive inventory of bryophytes in the BITH was initiated shortly after the establishment of the preserve.  Mueller (undated) conducted a preliminary inventory of bryophytes as part of a non-flowering plant survey in 1976 and early 1977.  In this survey, 70 species of bryophytes were identified within the preserve.  Following this initial report, additional authors supplemented the known bryophyte flora of the BITH (Stoneburner & Wyatt 1979; Bazan 1980; Lodwick & Snider 1980; Wyatt et al. 1980). 

Despite these published works, there has not been a comprehensive inventory of the bryophyte flora in the BITH since its establishment nearly 40 years ago.  The potential for utilization of vascular plant diversity as a surrogate for non-vascular plant diversity has been examined by several authors (McCune & Antos 1981; Fensham & Streimann 1997; Pharo et al. 1999, 2000; Soderstrom 1981).  However, the results have generally been inconclusive.  This inventory of the bryophyte flora adds an additional layer of investigation into the overall diversity of the BITH.

Results

A list of bryophytes reported in the BITH was compiled from literature references [Stoneburner and Wyatt (1979), Bazan (1980), Lodwick and Snider (1980), Wyatt et al. (1980)].  After removing species which were determined to be incorrectly identified the total number of species reported prior to the current inventory was 98.  This historical list contains 3 hornworts, 43 mosses, and 52 liverworts.  Following the completion of the current inventory, a total of 166 species are documented in the BITH based on extant collections and literature references.  This new total represents an increase of 68 species (41%) over the historical list and contains 4 hornworts, 95 mosses, and 67 liverworts. The largest increases in species within a family/genus are the Fissidentaceae (Fissidens) with an increase of eight species. The Leskeaceae increased by five species (four of which are in the genus Leskea), and the Amblystegiaceae, Pottiaceae, Ricciaceae, and Sphagnaceae, each with four new species. Additional increases in families and genera within the Bryaceae, Ephemeraceae, Fabroniaceae, and Lekeaceae, are noted since none of these families/genera were reported on the historical list.