Biology ETDs

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Leaf tissue production was studied to determine possible successional trends. The study area was in the spruce-fir zone of the southern Rocky Mountains 15 kilometers northeast of Santa Fe, New Mexico. In this area quaking aspen (Populus tremuloides) is a successional species that is slowly replaced by Engelmann spruce (Picea engelmannii) and corkbark fir (Abies lasiocarpa var. arizonica) as succession proceeds towards the classical spruce-fir climax. Five study plots were subjectively selected to represent a successional sequence of forest stands with similar physical characteristics. The plots were arranged in a successional series by using the increase in coniferous basal area at DBH as an indicator of later stages of succession. Overstory leaf production was measured by determining the DBH of every tree greater than 2.54 cm DBH and then applying regression equations to calculate leaf biomass. Aspen leaf production was assumed to be equal to aspen leaf biomass. For spruce and fir 25% of the leaf biomass was used for leaf production. Herbaceous leaf production was collected throughout the growing season whereas shrubs were collected once at the end of the growing season. Understory leaf production decreased with succession from 71.06 g/m -year to 9.07 g/m -year. Vaccinimn scoparimn dominated four of the five plots in terms of understory leaf production (no lower than 71%), but Thermopsis pinetorum reached the highest value in the earliest successional site (33%). Shrubs contributed only a minor portion of the total leaf production with the exception of aspen which produced 82 g/m -year in one site. In this site aspen was the canopy species, but did not qualify as overstory be definition (>2 .54 cm DBH). Leaf production of aspen increased through time in the first two plots and then decreased to zero in late succession. Spruce leaf production increased from 4.86 g/m -year in early succession to 503 g/m -year in late succession. Fir leaf production was not present in the first two plots, but increased to a maximum of 253 g/m2-year before the latest successional stage was reached. Overall leaf production increased from 160 g/m2 -year to 619 g/m2-year. Several successional trends were noted and discussed. It appears that leaf production may not yet have leveled off. More studies are suggested.



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Degree Name


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Department Name

UNM Biology Department

First Committee Member (Chair)

James R. Gosz

Second Committee Member

Loren D. Potter

Third Committee Member

Rex G. Cates

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Biology Commons