Hypothesis-testing methods for multivariate data are needed to make rigorous probability statements about the effects of factors and their interactions in experiments. Analysis of variance is particularly powerful for the analysis of univariate data. The traditional multivariate analogues, however, are too stringent in their assumptions for most ecological multivariate data sets. Non-parametric methods, based on permutation tests, are preferable. This paper describes a new non-parametric method for multivariate analysis of variance, after McArdle and Anderson (in press). It is given here, with several applications in ecology, to provide an alternative and perhaps more intuitive formulation for ANOVA (based on sums of squared distances) to complement the description pro- vided by McArdle and Anderson (in press) for the analysis of any linear model. It is an improvement on previous non-parametric methods because it allows a direct additive partitioning of variation for complex models. It does this while maintaining the flexibility and lack of formal assumptions of other non-parametric methods. The test- statistic is a multivariate analogue to Fisher's F-ratio and is calculated directly from any symmetric distance or dissimilarity matrix. P-values are then obtained using permutations. Some examples of the method are given for tests involving several factors, including factorial and hierarchical (nested) designs and tests of interactions.

/pdf/a-new-method-for-non-parametric-multivariate-analysis-of-2zyb4px7ty.pdf

A new method for non-parametric multivariate analysis of variance

Nutrient limitation (mostly N or P) is a driving force in ecosystem development. Current techniques to determine the nature of nutrient limitation use laborious fertilization experiments. It was hypothesized that the N:P ratio of'the vegetation directly indicates the nature of nutrient limitation on a community level (N vs. P limitation). This hypothesis was tested by reviewing data on fertilization studies in a variety of European freshwater wetland ecosystems (bogs, fens, wet heathlands, dune slacks, wet grasslands). In a subset of the data (dune slacks) between-site intraspecific variation and within-site interspecific variation in nutrient content and N:P ratio was studied in five plant species. A review of 40 fertilization studies reveals that an N:P ratio >16 indicates P limitation on a community level, while an N:P ratio < 14 is indicative of N limitation. At N:P ratios between 14 and 16, either N or P can be limiting or plant growth is colimited by N and P together. In only one out of 40 fertilization studies, the N:P ratio gave a false indication of the nature of nutrient limitation. Measuring the N:P ratio of the vegetation is a simple and cheap alternative to fertilization studies. The method can only be used under conditions where either N or P controls plant growth. The dataset contains a large variety of vegetation types and plant species, and 11 I of the 40 sites were near-monocultures. This suggests that interspecific differences in critical N:P ratios among species may be insignificant. However, a rigorous test of this hypothesis is required. A survey in 18 dune slacks showed large within-site variation in N:P ratio among five species (Calamagrostis epigejos, Phragmites australis, Lycopus europaeus, Mentha aquatica and Eupatorium cannabinum). The N:P ratios of the five species suggested that within plant communities species can be differentially limited by N or P. Moreover, species with an N:P ratio that suggested P-limitation were found at sites where N controlled community biomass production, and vice versa. Between-site intraspecific variation in N and P contents and N:P ratios was also large, and about equal for the five species. This illustrates the plasticity of plant species with respect to N and P contents, probably in response to differences in N and P supply ratios. The vegetation N:P ratio is of diagnostic value and its use may increase our understanding of numerous facets of physiological, population, community and ecosystem ecology.

The vegetation N:P ratio: a new tool to detect the nature of nutrient limitation

Although it is generally acknowledged that invasions by exotic plant species represent a major threat to biodiversity and ecosystem stability, little attention has been paid to the potential impacts of these invasions on nutrient cycling processes in the soil. The literature on plant–soil interactions strongly suggests that the introduction of a new plant species, such as an invasive exotic, has the potential to change many components of the carbon (C), nitrogen (N), water, and other cycles of an ecosystem. I have reviewed studies that compare pool sizes and flux rates of the major nutrient cycles in invaded and noninvaded systems for invasions of 56 species. The available data suggest that invasive plant species frequently increase biomass and net primary production, increase N availability, alter N fixation rates, and produce litter with higher decomposition rates than co-occurring natives. However, the opposite patterns also occur, and patterns of difference between exotics and native species show no trends in some other components of nutrient cycles (for example, the size of soil pools of C and N). In some cases, a given species has different effects at different sites, suggesting that the composition of the invaded community and/or environmental factors such as soil type may determine the direction and magnitude of ecosystem-level impacts. Exotic plants alter soil nutrient dynamics by differing from native species in biomass and productivity, tissue chemistry, plant morphology, and phenology. Future research is needed to (a) experimentally test the patterns suggested by this data set; (b) examine fluxes and pools for which few data are available, including whole-site budgets; and (c) determine the magnitude of the difference in plant characteristics and in plant dominance within a community that is needed to alter ecosystem processes. Such research should be an integral component of the evaluation of the impacts of invasive species.

Effects of Exotic Plant Invasions on Soil Nutrient Cycling Processes

B6nassy, C., 1955. R6marques sur deux Aphelinid6s: Aphelinus mytilaspidis Le Baron et Aphytis proclia Walker. Annls l~piphyt. 6: 11-17. Lord, F. T. & MacPhee, A. W., 1953. The influence of spray programs on the fauna of apple orchards in Nova Scotia II. Oyster shell scale. Can. Ent. 79: 196-209. Pickett, A. D., 1946. A progress report on long term spray programs. Rep. Nova Scotia Fruit Grow. Ass. 83 : 27-31. Pickett, A. D., 1967. The influence of spray programs on the fauna of apple orchards in Nova Scotia XIV. Can. Ent. 97: 816-821. Tothill, J. D., 1918. The predacious mite Hemisarcoptes malus Shimer and its relation to the natural control of the oyster shell scale Lepidosaphes ulmi L. Agric. Gaz. Can. 5 : 234-239.

http://link.springer.com/content/pdf/10.1007/BF01976688.pdf

Soil enzymes: Kuprevich, V. F. & Shcherbakova, T. A.: Translated from the Russian edition (1966), published by the Indian National Scientific Documentation Centre, New Delhi 1971. 392 pp., offset printing from type script, paper cover. Obtainable from U.S. Department of Commerce, National Technical Information Service, Springfield, Va. 22151

▪ Abstract In the search to identify factors that make some plant species troublesome invaders, many studies have compared various measures of native and alien invasive plant performance. These comparative studies provide insights into the more general question “Do alien invasive plants usually outperform co-occurring native species, and to what degree does the answer depend on growing conditions?” Based on 79 independent native-invasive plant comparisons, the alien invaders were not statistically more likely to have higher growth rates, competitive ability, or fecundity. Rather, the relative performance of invaders and co-occurring natives often depended on growing conditions. In 94% of 55 comparisons involving more than one growing condition, the native's performance was equal or superior to that of the invader, at least for some key performance measures in some growing conditions. Most commonly, these conditions involved reduced resources (nutrients, light, water) and/or specific disturbance regimes. I...

https://www.jstor.org/stable/pdfplus/30033774.pdf

PERFORMANCE COMPARISONS OF Co-OCCURRING NATIVE AND ALIEN INVASIVE PLANTS: Implications for Conservation and Restoration

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 1 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 1, 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 (MIP) 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.

/pdf/secondary-successional-patterns-in-a-sagebrush-artemisia-2hz8wbwrtd.pdf

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

A soil nitrogen (N) availability gradient was induced on a disturbed sagebrush site in northwestern Colorado by fertilizing with nitrogen (high available N), applying sucrose (low available N), and applying neither nitrogen nor sucrose (control). Species composition was studied for 3 years. At the end of the study, N concentration of aboveground tissue of 3 major species was determined. The rate of species replacement was most rapid on plots receiving the sucrose treatment and was slowest on plots receiving the N treatment. Early-seral dominats had greater tissue N concentrations when availability of the resource was high but lower tissue N concentrations when available soil N became limited. Midseral dominants displayed the opposite pattern. These results suggest that the supply of available soil N, and therefore the dynamics of N incorporation in perennial plant tissue, is a primary mechanism in controlling the rate of secondary succession within this semiarid ecosystem.

Effects of nitrogen limitation on species replacement dynamics during early secondary succession on a semiarid sagebrush site.

Water treatment residuals (WTRs) are a by-product of municipal drinking water treatment plants and can have the capacity to adsorb tremendous amounts of P. Understanding the WTR phosphorus adsorption process is important for discerning the mechanism and tenacity of P retention. We studied P adsorbing mechanism(s) of an aluminum-based [Al 2 (SO 4 ) 3 .14H 2 O] WTR from Englewood, CO. In a laboratory study, we shook mixtures of P-loaded WTR for 1 to 211 d followed by solution pH analysis, and solution Ca, Al, and P analysis via inductively coupled plasma atomic emission spectroscopy. After shaking periods, we also examined the solids fraction by X-ray diffraction (XRD) and electron microprobe analysis using wavelength dispersive spectroscopy (EMPA-WDS). The shaking results indicated an increase in pH from 7.2 to 8.2, an increase in desorbed Ca and Al concentrations, and a decrease in desorbed P concentration. The pH and desorbed Ca concentration increases suggested that CaCO 3 controlled Ca solubility. Increased desorbed Al concentration may have been due to Al(OH) - 4 formation. Decreased P content, in conjunction with the pH increase, was consistent with calcium phosphate formation or precipitation. The system appeared to be undersaturated with respect to dicalcium phosphate (DCP; CaHPO 4 ) and supersaturated with respect to octacalcium phosphate [OCP; Ca 4 H(PO 4 ) 3 . 2.5H 2 O]. The Ca and Al increases, as well as OCP formation, were supported by MINTEQA2 modeling. The XRD and EMPA-WDS results for all shaking times, however, suggested surface P chemisorption as an amorphous Al-P mineral phase.

Phosphorus retention mechanisms of a water treatment residual.

A sagebrush steppe community in northwestern Colorado was disturbed in 1984 and subjected to annual applications of nitrogen and phosphorus, and successional responses were studied over a 5-yr period. Phosphorus was not found to be significant but nitrogen did significantly affect succession for all years except the first. Three seral groups developed on the non-fertilized plots, the first two dominated by annuals and lasting 3 yr, the third transitional and dominated by perennials. The addition of N altered this successional pattern by allowing annuals to remain as site dominants through the 5th yr. Results of this study suggests that dominance of a site by annuals in early stages of secondary succession is related to high nutrient availability.

Edward F. Redente

Papers

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

Effects of nitrogen limitation on species replacement dynamics during early secondary succession on a semiarid sagebrush site.

Phosphorus retention mechanisms of a water treatment residual.

Nitrogen and phosphorus effects on secondary succession dynamics on a semi-arid sagebrush site

Simulation model for the effects of climate change on temperate grassland ecosystems