Shrub Form Research Articles

Aboveground biomass allocation, leaf growth, and photosynthesis patterns in tundra plant forms in arctic Alaska.

Tundra plant growth forms can generally be characterized as consisting predominantly of low-growing perennial grasses and sedges, perennial herbaceous forbs, dwarf deciduous shrubs, and dwarf evergreen shrubs. Gross aboveground carbon allocation, leaf growth, and photosynthesis pattern studies were initiated to develop a quantitative understanding of the functional importance of these particular tundra growth forms. Photosynthetic capacities of 13 species were determined under standardized exposure conditions using a14CO2 field system and ranged between 5 and 47 mg CO2·g dry wt-1·h-1. These results, in conjunction with detailed leaf growth determinations, support the generalization that species with an evergreen growth form have lower photosynthetic capacities than species with a perennial graminoid, forb, or deciduous shrub growth form. However, these low photosynthetic capacities in evergreen shrubs are associated with relatively extended leaf longevities. Conversely, deciduous shrub forms exhibited high photosynthetic capacities, but were offset by relatively short leaf longevity periods. The perennial grasses, sedges, and forbs showed patterns intermediate to these. As a result, it appears that among tundra species of different growth form, photosynthetic capacity is inversely related to leaf longevity.

The pregnane glycosides of the climbing form of Sarcostemma viminale (L.) R

AbstractThe dried twigs and stems of Sarcostemma viminale (the climbing shrub form from South Rhodesia) contain about 1% phenolic and a similar amount of glycosidic compounds derived from 2‐deoxysugars; only traces of cardenolides are present. After mild acidic hydrolysis 5 sugars could be detected and subsequently isolated in pure form. Three of them (d‐cymarose, d‐digitoxose and lilacinobiose) were obtained crystalline, the two others (d‐oleandrose and viminose) in amorphous form. Viminose is a new sugar, a disaccharide which contains d‐thevetose, and d‐Digitoxose at the reducing end [30 b].The mixture of aglycones, obtained after mild acidic hydrolysis, contained mainly five components (F, G, H. J and K), all of which could be isolated in pure form. F, G and J were crystalline. F was identified as metaplexigenin (1), J as mono‐O‐acetyl‐mono‐O‐benzoyl‐sarcostin (5) and K as 12,20‐di‐O‐benzoyl‐sarcostin (6). G and H are new compounds whose structures (G = 12‐O‐benzoyl‐deacetyl‐metaplexigenin (2), H = di‐O‐benzoyl‐viminolone (3)) are deduced in the following paper. After alkaline hydrolysis of the aglycone mixture, sarcostin, deacetylmetaplexigenin and small amounts of lineolon could be dedected by paper‐ and thinlayerchromatography.The two pregnane derivatives EA‐42 and EA‐43 described by Abisch et al. [21] could be identified with 3, 20‐di‐O‐benzoyl‐utendin and 3, 20‐di‐O‐benzoyl‐sarcostin, respectively.In the NMR.‐spectra of sarcostin and of many (not all) of its derivatives a strong signal (mostly a singlet corresponding to ca. 3 protons at ca. δ = 2 ppm) is present, which cannot be explained with the suggested structures. The cause of this extra signal could not be elucidated.

The Carnivores and Ungulates of the Aransas National Wildlife Refuge, Texas

A brief history and status of the carnivores and ungulates of the Aransas National Wildlife Refuge, Texas is presented. Coyotes, raccoons, striped skunks, bobcats, feral hogs, javelinas, and white-tailed deer are common to abundant. Red wolves and gray fox are uncommon. Ringtailed cat, badgers, and spotted skunks are rare. Introduced fallow deer have been eliminated and introduced mule deer never became established. The Aransas National Wildlife Refuge in the coastal bend area of Texas is renowned as the wintering ground of the Whooping Crane (Grus americana), and as a source of thousands of white-tailed deer (Odocoileus virginianus) which have been transplanted elsewhere (Glazener, 1948). Much unpublished information has been accumu- lated on the ungulates and carnivores of this refuge. It is the purpose of this paper to summarize this information as a contribution to the ecology of one of America's most important wildlife refuges. Gabrielson (1943) has told of the establishment of the area, which is managed by the Bureau of Sport Fisheries and Wildlife, U. S. Fish and Wildlife Service, Department of the Interior. The author has made periodic field trips to the area between 1955 and 1960 to work on mammals and their management. Specimen records from the U. S. Biological Survey Collection, Washington, D.C. have kindly been supplied by Viola S. Schantz. Similar records from the Texas Cooperative Wildlife Collection at College Station, Texas, have been made available by Dr. William B. Davis, who also reviewed the manuscript. Refuge files have been consulted. The records of for- mer Refuge Manager James O. Stevenson have been particularly valu- able. Refuge Manager Huyson J. Johnson and his staff were most helpful. The Aransas Refuge was established December 31, 1937, on the Texas coast in parts of Aransas, Refugio, and Calhoun counties. It occupies 47,261 acres of the Blackjack or St. Charles Peninsula. Much of the area is covered by live oak (Quercus virginiana) in both the tree and the shrub or shinnery form. The peninsula was named after the blackjack oak (Q. marilandica) which occurs in scattered inland stands. The rich flora of the refuge includes representatives from both