Ecology of Picea Chihuahuana Martinez

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Abstract
Picea chihuahuana probably arrived in North America during Cretaceous or earlier times. The Physiography, climate, and forest geography of its present range in the Sierra Madre Occidental of Mexico are described. The forests are cool montane temperate rather than boreal. In the station examined. P. chihuahuana was distributed only on fresh and moist sites. Growth rates both in height and diameter on moist sites exceeded those on the fresh. The culmination point for diameter growth was at 85 years. The mean specific gravity was .347, and differences due to site were not significant. The moist site soils supporting P. chihuahuana differed from the fresh site soils only in having flower pH, Ca, and K levels. Since the sites were closely associated and the parent materials identical, it is assumed that these differences were due to differences in moisture regime. The foliar nutrient concentration of N, P, and K decreased with increasing needle age except that P and K increased markedly in the oldest needles. Conversely, Ca increased with advancing needle age but decreased in the oldest needles. P. chihuahuana shows a remarkable tolerance for high Ca concentration. The associated vegetation of the P. chihuahuana stand was measured on both fresh and moist sites, and significant differences between the plant assemblages of these sites were found. Its present range and pattern of regeneration indicate that P. chihuahuana may not long escape extinction.

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