Secondary successional patterns in a sagebrush (Artemisia tridentata) community as they relate to soil disturbance and soil biological activity

Abstract

The relationship between secondary succession, soil disturbance, and soil biological activity were studied on a sagebrush community (Artemisia tridentata) in the Piceance Basin of northwestern Colorado, U.S.A. Four levels of disturbance were imposed. I: the vegetation was mechanically removed and as much topsoil as possible was left; 2: the vegetation was mechanically removed and the topsoil scarified to a depth of 30 cm; 3: topsoil and subsoil were removed to a depth of I m, mixed and replaced; 4: topsoil and subsoil were removed to a depth of 2 m and replaced in a reverse order. Plant species composition, dehydrogenase and phosphatase enzymatic activity, mycorrhizae infection potentials, and percent organic matter were the variables measured.Treatment 4 drastically altered the pattern of vegetation succession. Treatments 2, 3, and 4 started with Salsola iberica as the dominant species but six years later, 3 and to lesser extent 2 changed in the direction of the species composition of l, dominated by perennial grasses and perennial forbs. Treatment 4 developed a shrub dominated community. The rate of succession was not decreased by the increased levels of disturbance. Both dehydrogenase enzyme activity and mycorrhizae infection potential (M1P) increased with the change from Salsola iberica to a vegetation dominated by either perennial grasses and forbs or shrubs. The intensity of disturbance in 2, 3, and 4 reduced drastically dehydrogenase activity and MIP, but in six years they recovered to levels comparable to 1. Phosphatase enzyme activity and organic matter were unrelated to species composition but related to treatment and time elapsed. In both cases a significant decrease was observed throughout the six-year period.

The Lung Tissue Microbiome in Chronic Obstructive Pulmonary Disease

“…TRFLP fingerprints were analyzed for presence-absence and relative abundance of peaks by PC-ORD (MJM Software Design, Gleneden Beach, OR) plus nonmetric multidimensional scaling (31) and a multiresponse permutation procedure (32) measuring T, A, and P values. Pyrotag sequence qvality filtering, binning into operational taxonomic units (OTUs), and taxonomic assignment were conducted (see online supplement).…”

Spatial Variation in Inoculum Potential of Vesicular‐arbuscular Mycorrhizal Fungi Caused by Formation of Gopher Mounds

“…Species composition (Bethlenfalvay, Dakessian & Pacovsky, 1984;Kovacic, St John & Dyer, 1984;Biondini et al, 1985) and plant density (Koske & Halvorson, 1981) have been shown to affect inoculum potential.…”

“…This is because phosphorus transfer (Heap & Newman, 1980;Chiariello, Hickman & Mooney, 1982;Whittingham & Read, 1982), competition (Crush, 1974;Eitter, 1977;Hall, 1978; and phosphorus cycling (Smith, 1980) may all be influenced by mycorrhizal infection. Horizontal variability in inoculum potential may be altered by factors such as disturbance (Miller, 1979;Reeves et al, 1979;Biondini, Bonham & Redente, 1985), sodium content (Kim & Weber, 1985) and moisture content of soils (Rabatin, 1979;.…”

Effects of riparian vegetation on the structure of the marginal aquatic habitat and the associated fish assemblage in a tropical Brazilian reservoir

“…Non-metric Multidimensional Scaling (NMS) of the standardized arcsine-squareroot-transformed data (Bray-Curtis similarity) ( McCune & Grace 2002) was used to evaluate variations in habitat composition between sites and areas (forested and non-forested). The Multi-Response Permutation Procedure (MRPP) (Biondini et al 1985, McCune & Grace 2002) was used to test significance of differences in habitat composition between sites and areas. MRPP is a non-parametric procedure for testing the hypothesis of no difference between two or more groups of entities defined a priori.…”