Live oak is the single most significant plant species influencing the 

 dynamics of upland wildlife populations. It achieves such importance by 

 virtue of its community dominance and its dependable supply of nutritious and 

 preferred food. As a community dominant, live oak satisfies the diverse cover 

 requirements of many species. Its dependable annual seed crop forms the 

 seasonal nucleus of many consumer food webs. 



Brazoria and San Bernard National Wildlife Refuges 



The Brazoria and San Bernard NWR represent the two most recent additions 

 to the NWR system in Texas. The Brazoria NWR was established in 1966, and the 

 San Bernard NWR in 1968. Both refuges were treated as a single unit for the 

 following reasons: (1) a shortage of baseline and historical data exists for 

 each refuge individually; (2) the refuges are in close proximity; (3) the 

 refuges have many similar ecological characteristics; and (4) both refuges are 

 currently administered as one management unit. Throughout this discussion, 

 important differences will be noted when necessary. 



Location . Both the Brazoria and the San Bernard NWR lie in Brazoria County, 

 Texas. The 4,041-ha (9,978-acre) Brazoria Refuge is located in the south central 

 portion of the county approximately 27 km (17 mi) southeast of Angleton. Its 

 boundary on the east and south are formed by Bastrop, Christmas, and Drum Bays; 

 its northern boundary is Bastrop Bayou. The 7,850-ha (19,382-acre) San Bernard 

 Refuge, located 16 km (10 mi) southwest of Freeport, is bound by the San Bernard 

 River on the east; by Cedar Lake Creek, which is also the Matagorda County line, 

 on the west; and by the Gulf of Mexico on the south. Both refuges lie within 

 easy driving distance of Houston, Galveston, Freeport, and Texas City. 



Geology . The development of the Quaternary geology in the vicinity of 

 the San Bernard Refuge is the basis for understanding oil and gas potential, 

 substrate characteristics, and ground fluids characteristics. The geology 

 around the San Bernard Refuge was to a great extent affected by the relative 

 position of sea level between the stages of glaciation. However, another 

 important parameter was the activity of the ancestral Brazos and Colorado 

 Rivers in combining to fill their sizable estuary between 3,000 and 1,500 yr 

 ago, after the present sea level had been established. This coastal sedimen- 

 tation has resulted in the unique characteristic on the Texas coast of a well- 

 developed mainland-type shoreline without an offshore barrier island. 



The modern Brazos River (the mouth of which was relocated in 1929) drains 

 an area of more than 11,600 Km (44,600 mi ), making it one of the largest river 

 systems in the Gulf of Mexico basin, and therefore one of the major sources of 

 sediment. The coastal delta lobe of this system has developed a cuspate shape 

 representing the opposing levels of the energy involved in supplying sediment, 

 basin subsidence, and the reworking of the sediment. Within the broad area 

 defined by the cuspate delta, there are, of course, several subdeltaic features: 

 natural levees, abandoned mud-filled channels, overbank flood basin silts and 

 clays, and marshes, swamps, and lakes. The area of the San Bernard NWR is an 

 interdistributary area between the Brazos and San Bernard fluvial systems. It 



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