Ultimately, does knowledge of these factors of change provide clues to the contemporary distribution and abundance patterns of Ashe and Redberry juniper?ĭuring the Pleistocene (ice ages last 2,000,000 years), there were several glacial-interglacial cycles where ice sheets expanded and receded over major portions of Canada, the northern United States and high evaluations of mountainous regions (Butzer 1976). Information presented will be skewed in favor of the Edwards Plateau since 1) it is the region with the greatest amount of available information and 2) it is the region of greatest familiarity to the authors. With the above qualifications an attempt will be made to piece together what we know or suspect has happened in this region from about 10,000 years ago to the present. In spite of these qualifications, when consistent patterns arise from different sources of information reasonable interpretations can be accomplished. Hence caution is required when conducting any sort of historical assessment. when written records become available they are highly influenced by the technical competence, experience, time of observation, motivation and objectives of the observer.the location within an ecoregion from which information is available constrains interpretations since most records are site or local terrain specific and do not necessarily represent the entire region,.the further back in time the less complete and accurate the record,.Some issues that must be kept in mind when interpreting historical changes are: interaction of all of the above individual factors rarely operate in isolation in the real world but rather are telescoped upon one another and interact in multifarious ways.Ī major problem when interpreting historical changes is that the record is woefully incomplete and unbalanced.natural or man-caused alterations in soil conditions that increase surface heterogeneity of the soil,.introduction of domestic livestock and ultimately widespread overstocking of the ranges,.alteration in the distributions, numbers and kinds of wild animal populations,.influence of Native Americans (last 12,000? years),.recent changes in weather and climate including droughts, wet periods, and perhaps temperature change due to increased greenhouse gases in the atmosphere, etc.,.long-term (Holocene: last 10,000 yrs) changes and fluctuations of the climate,. Many factors influence contemporary vegetation composition and structure. This will be followed by a review of known and speculated changes that have occurred since settlement and up to the present time (ca. A brief assessment of pre-European settlement history (Holocene and Native American period) will be presented to set the stage. This chapter will address historical changes that have influenced the environment, the vegetation and ultimately man’s use of the land in the Edwards Plateau and Rolling Plains and specifically address the status of Ashe and Redberry juniper. Juniper species in particular have extended their geographic ranges, as well as increased their abundance (Miller and Wigand 1994, Ansley et al. Across rangeland regions of North America woody vegetation has generally increased in abundance relative to grasslands during the past 150 years (Smeins 1984, Archer 1994). The focus of this symposium is on two species of juniper (cedar), Ashe ( Juniperus ashei) and Redberry ( Juniperus pinchotii), that are important vegetation components of the Edwards Plateau, the Rolling Plains and portions of adjacent ecoregions of Texas (Figures 1 and 2)(Hatch et al. Fred Smeins, Sam Fuhlendorf and Charles Taylor, Jr.
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