Response of understory species to changes in ponderosa pine stocking levels in the Black Hills

The objective of this study was to test the hypothesis that there are no differences in understory production, by species, due to stocking levels of Pinus ponderosa (ponderosa pine). Understory production was estimated, by species, on 3 replicates each of 8 growing stock levels, ranging from clearcuts to unthinned stands, in both sapling- and pole-sized pine stands (48 plots) over 3 nonconsecutive years. All stands were approximately 70 yr old when thinning treatments were applied. Production of many herbaceous species, especially Agropyron spp. (wheatgrasses) and Carex spp. (sedges), declined as growing stock levels (measured in terms of basal area) of ponderosa pine increased. While trends in total production were similar, there were specific differences between sapling and pole stands. Sedges and Oryzopsis asperfolia (roughleaf ricegrass) produced more in sapling stands, whereas Danthonia intermedia (timber oatgrass) was more abundant in pole stands. Shrub production, dominated by Acrtostaphylos uva-ursi (bearberry), was relatively consistent across all stocking levels except unthinned. Although the total number of species declined as pine basal area increased, a few species, such as Linnaea borealis (twinflower) and Shepherdia canadensis (buffaloberry), were found only under relatively dense pine canopies. While floristic species richness was greater at lower stocking levels of ponderosa pine, the total number of species would be greater if all stocking levels were present.     

Association of black-tailed prairie dog colonies with cattle point attractants in the Northern Great Plains

In October 1991 we recorded all black-tailed prairie dog ( Cynomys ludovicianus ) colonies and cattle points in a 1248-km 2 study area in southwest North Dakota and southeast Montana. Cattle point attractants were defined as fabricated water tanks and long-term supplemental feed sites. We found that a signivicant number of prairie dog colonies encompassed or adjoined cattle point attractants ( p < .001). Prairie dog colonies associated with cattle point attractants were a mean distance of 1.0 km from the next nearest town. The existence of cattle point attractants may encourage prairie dog colonization. Conversely, refraining from using long-term cattle point attractants can discourage prairie dog colonization.     

Indicators of red squirrel (Tamiasciurus hudsonicus) abundance in the whitebark pine zone

We investigated occupied squirrel middens and squirrel sightings and vocalizations as indicators of red squirrel ( Tamiasciurus hudsonicus ) abundance in high-elevation whitebark pine ( Pinus albicaulis ) zone. Data were collected 1984-1989 from line transects located on 2 study sites in the Yellowstone ecosystem. We evaluated the performance of each measure on the basis of precision and biological considerations. We concluded that, of the 3 measures, active middens were the best indicator of red squirrel abundance. We also observed that the density of active middens dropped by 48%-66% between 1987 and 1989, following a severe drought and extensive wildfires that burned one of the study sites during 1988.     

Redox enzyme models from polymerized aminoacyladenylates

Résumé Des modèles d'enzymes d'oxydoréduction ont été préparés par polymérisation des 20 aminoacyladénylates en présence de flavine mononucléotide, d'hème et de chlorophylle. L'addition du cofacteur flavinique au cours de la polymérisation modifie la composition en acides aminés du polymère obtenu. L'article offre une discussion sur les taux de réaction, les absorptions optiques et de dispersion rotatoire et les propriétés générales des modèles d'enzymes d'oxydoréduction.

---

---

The support from a National Science Foundation Development Program grant to the University of Texas is gratefully acknowledged as is the assistance ofDirk Schenkkan and Mrs.Sandra Smith.     

Arylsulfatase B synthesis and clearance in inbred mouse strains

Arylsulfatase B activity levels were approximately 2-3-fold higher in adult C57BL/6J liver and kidney compared to corresponding tissues from A/J inbred mice. In vivo incorporation of tritiated leucine into C57BL/6J hepatic arylsulfatase B reached a maximum approximately 15 h after injection. The label was cleared from C57BL/6J arylsulfatase B with an apparent half-life of 36 h. The relative rates of synthesis of C57BL/6J and A/J arylsulfatase B were similar; however, the A/J enzyme was cleared more rapidly from liver tissue. C57BL/6J kidney arylsulfatase B appeared to be synthesized at a 2-3-fold higher rate than the corresponding A/J enzyme. These trends suggest genetic regulation of arylsulfatase B is effected through different means in liver and kidney from adult mice of these two inbred strains.     

Experimental study in rats to reduce carbon monoxide in the blood induced by cigarette smoke, by inhaling oxygen at atmospheric pressure]

When animals are exposed to cigarette smoke, the concentration of carbon monoxide in blood is rapidly increased, so that intensive inhalation tests cannot be carried out. A simple apparatus is described to expose Rats alternatively to cigarette smoke and to oxygen in order to reduce the concentration of carbon monoxide in the blood. This method makes it possible to increase the daily administration of smoke considerably; nevertheless, under such conditions, lung tumors were not observed.