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标题：Dasylirion cedrosanum Trelease (Nolinaceae) Density Varies Depending on Elevation and Slope in the Northeast of Zacateacas, Mexico
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作者：Alfredo Robles-Esparza ; Hermes Robles-Berumen ; Fidel Blanco-Macias 等
期刊名称：Ekoloji
印刷版ISSN：1300-1361
出版年度：2012
期号：85
DOI：10.5053/ekoloji.2012.852
出版社：Çevre Koruma ve Araştırma Vakfı
摘要：There is little or no specific and concise information on the ecological conditions which constrain distribution, abundance, and density of Dasylirion cedrosanum Trelease keeping in mind that such knowledge is indispensable to promote and support plantations and reforestation programs in order to confront the consequences of a possible depletion of natural populations. Therefore, the aim of this study was to evaluate D. cedrosanum density as related to ecological factors such as latitude, longitude, altitude, slope, soil texture fractions, pH, electric conductivity, available nitrogen and phosphorus contents, and organic matter content on a xerophytic scrub in the northeast of the Mexico’s state of Zacatecas. Data from 41 square–shaped sampling units of 1.000 m² each from an area of 2.422.2 ha where altitude varies from 2.000 to 2.356 masl, and slope inclination changes from moderate (5.5%) to steep (44.2%) was analyzed through linear relationships, quadratic functions, and principal components analysis. Results provide compelling evidence about D. cedrosanum density depends on elevation, inclination, and soil silt and sand contents. A triangular-shaped dispersion of observations when density is plotted against each soil, silt or sand, contents was appreciated. A significant humped trend suggest that sites having slopes around 20%, although it could be in the 10 to 30% slope range, provides a better habitat for this species. D. cedrosanum plants are scarcer, that is, present at low and minimum densities (< 259 plants ha^-1) in the sampled units characterized by high slopes and elevations, and more sandy soils.
关键词：Chihuahuan desert scrub; ecological factors; Humped trend; triangular-shaped distribution; soil texture.