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For the prairie-forest ecotone of central North America, research of the effects of climate and fire on the annual growth of nonwoody plant types is currently needed to compliment dendrochronological research used for predicting the stability of this ecotone in the future. Using cores of Quercus stellata Wangenh. and collars of taproots of Asclepias viridis Walter from central Oklahoma, as well as cores from Quercus macrocarpa Michx. and Lespedeza capitata Michx. collars in central Minnesota, we aimed to distinguish the response towards annual precipitation and temperature, as well as fire regime, between these co-existing plant types through patterns in annual ring growth. The effect of spring fire on the annual growth increment was only consistently significant for one of the forbs, with a positive relationship. The strong negative effect of summer temperature was consistent between forbs and Q. stellata, while the positive effect of either growing season precipitation was consistent between plant types. Furthermore, we found stronger patch-specific annual ring patterns in forbs in comparison with trees when patches are separated based on unique fire histories. Overall, such efforts could be used in further studies to better predict growth rates of dominant plant types in landscapes susceptible to significant environmental change. Key words: annual rings, Asclepias viridis, climate, dendrochronology, fire, forbs, herb chronology, Lespedeza capitata, prairie-forest ecotone, Quercus stellata, Quercus macrocarpa. Dans le cas de l'ecotone prairie-foret du centre de l'Amerique du Nord, la recherche concernant les effets du climat et du feu sur la croissance annuelle des types de plantes non ligneuses est actuellement necessaire pour completer la recherche dendrochronologique utilisee pour predire la stabilite future de cet ecotone. A l'aide de carottes de Quercus stellata Wangenh. et de collets racinaires d'Asclepias viridis Walter provenant du centre de l'Oklahoma ainsi que de carottes de Quercus macrocarpa Michx. et de collets racinaires de Lespedeza capitata Michx. provenant du centre du Minnesota, nous avons cherche a distinguer la reaction a la precipitation et a la temperature annuelles ainsi qu'au regime de feu de ces types de plantes coexistantes a l'aide des patrons dans les cernes annuels. L'effet des feux de printemps sur l'accroissement annuel etait constamment significatif pour seulement une des plantes herbacees non graminoides et la relation etait positive. L'effet negatif important de la temperature estivale etait constant chez les plantes herbacees non graminoides et Q. stellata tandis que l'effet positif des precipitations durant chaque saison de croissance etait constant parmi les types de plantes. De plus, nous avons observe des patrons plus nets dans les cernes annuels, specifiques aux Hots de plantes herbacees non graminoides, comparativement aux arbres lorsque les Hots etaient separes sur la base de leur historique de feu particulier. Dans l'ensemble, de tels efforts pourraient etre utilises dans le cadre d'etudes ulterieures pour mieux predire le taux de croissance des types vegetaux dominants dans les paysages sujets a un changement environnemental important. [Traduit par la Redaction] Mots-cles : cernes annuels, Asclepias viridis, climat, dendrochronologie, feu, plantes herbacees non graminoides, dendrochronologie des herbacees, Lespedeza capitata, ecotone prairie-foret, Quercus stellata, Quercus macrocarpa., Introduction The prairie-forest ecotone of central North America is responsive to environmental changes, leading to dramatic shifts of vegetation boundaries (Umbanhowar et al. 2006; Camill et al. 2003). Differential responses [...]

The relatively new field of herbaceous root chronology ('herb chronology') uses the annual rings of secondary xylem in roots of perennial forbs to analyze belowground secondary growth as a function of annual growth environment. By using three tallgrass forb species from long-term experiments within Konza prairie of northeastern Kansas (USA), we aimed to find the effects of fertilization, growing season temperature, and precipitation on annual secondary growth. For two of the three species, we found annual rings were significantly larger among plots that were fertilized annually with phosphorus or nitrogen + phosphorus in contrast to unfertilized control plots. Rings also had significant variation with climatic variables. We found a consistent negative correlation with early season temperature for each species. However, early growing season precipitation proved to be far less consistent, with positive correlations only found in a few cases between species. Overall, we conclude that annual rings in these select tallgrass prairie species may not carry reliable climatic signatures; rather site-specific ecological factors, such as aboveground competition with neighbors, may be more important for annual ring patterns. In our discussion we propose a framework to help better disentangle the effects of site or climatic factors that may affect herbaceous annual ring variation. Keywords: annual rings, herb chronology, grasslands, interannual climatic variability, fertilization, supplemental water. Le champ d'etude relativement nouveau qu'est la dendrochronologie appliquee aux herbacees utilise les anneaux annuels du xyleme secondaire des racines d'herbes non gramineennes vivaces afin d'analyser la croissance secondaire souterraine en fonction de l'environnement de croissance annuel. Les auteurs avaient pour objectif d'examiner les effets de la fertilisation, de la temperature de la saison de croissance et des precipitations sur la croissance annuelle secondaire de trois especes d'herbes non gramineennes de prairies hautes, lors d'experiences a long terme realisees dans la ' Konza Prairie ' dans le nord-est du Kansas, Etats-Unis. Chez deux des trois especes, les auteurs ont trouve que les anneaux de croissance etaient significativement plus larges entre les lots fertilises annuellement au phosphore ou a l'azote + phosphore comparativement aux lots controles non fertilises. Les anneaux presentaient aussi des variations significatives en fonction des variables climatiques. Les auteurs ont trouve une correlation negative constante en fonction de la temperature du debut de la saison chez chaque espece. Cependant, les precipitations en debut de saison de croissance se sont montrees beaucoup moins constantes, des correlations positives n'etant observees dans quelques cas seulement entre les especes. Dans l'ensemble, les auteurs concluent que les anneaux de croissance de ces especes des prairies hautes ne constitueraient pas des signatures climatiques fiables; par ailleurs, des facteurs ecologiques specifiques du site, comme la competition en surface avec des voisins, pourraient etre plus importants dans l'etablissement des patrons des anneaux de croissance. Dans leur discussion, ils proposent un cadre aidant a mieux degager les effets du site ou des facteurs climatiques qui peuvent affecter la variation des anneaux annuels chez les herbacees. [Traduit par la Redaction] Mots-cles : anneaux annuels, dendrochronologie appliquee aux herbacees, variabilite climatique interannuelle, fertilisation, supplement d'eau., Introduction Annual growth rings in the secondary xylem of plants may be useful for linking past environmental conditions with annual growth. In the field of dendrochronology, annual ring widths from [...]

Recent empirical work in numerous systems has demonstrated the interdependence of spatial and temporal accumulation of species in the species--time--area relationship (STAR). The purpose of this study was to develop a process-based stochastic model for the STAR that assumes species neutrality and to compare the model's expectations to data collected on plant species in a tallgrass prairie. We varied two important aspects of the neutral species assemblage: evenness in the species pool and individual replacement rate (R). When R is larger than ~0.5 and evenness is intermediate to high, the neutral STAR generates patterns qualitatively similar to the empirical STAR. Our model also indicates that space and time were not symmetrical in their effects on species accumulation, except in the special case of R = 1.0. We observed both positive and negative time-by-area interactions in the sampling model, which indicates that nonzero interactions are not necessarily evidence of ecological processes. Furthermore, as accumulated richness approaches the size of the species pool, the time-by-area interaction becomes increasingly negative in our model. This suggests that negative time-by-area interactions should be expected a priori in empirical systems if rates of species accumulation decrease due to increasing rarity of unique species. Given the wide range of STARs that the sampling model generated, the difficulty in estimating key parameters, and the complexity of assessing the relative abundance distribution and scale of the species pool, we cannot refute the sampling effect, and we suggest caution in accepting ecologically oriented explanations of empirical STARs. Key words: biodiversity; grassland; rarefaction effect; sampling effect; scale dependence; scaling; species richness; species--time--area relationship (STAR); species turnover.

Despite the common geographic occurrence of inland (athalassic) saline habitats, their biota has not been extensively studied. Diatoms have been estimated to contribute as much as 25% to the earth's primary production (Werner, 1977). However, in hypersaline systems the proportion of in situ carbon fixation by diatoms is likely to be higher. We used substrate samples taken from the Salt Plains National Wildlife Refuge, an athalassic hypersaline ecosystem, to investigate the relationship between diatom genus diversity, composition and salinity. These samples range in salinity from 14 to 306 ppt and contain 21 genera. Six genera (Cymbella, Mastogloia, Psammodictyon, Amphora, Navicula and Nitzschia) comprise 97% of the diatoms counted in all samples. Diatom genus diversity shows an inverse relationship with salinity, while genus richness shows no clear relationship with salinity. Hence, loss in diversity is the result of dominance by fewer taxa at higher salinities. The relative abundance of the genus Navicula is positively correlated with salinity, with it dominating the highest salinity sites. We used a canonical correspondence analysis (CCA) to explore the relationship between salinity and relative abundance of diatom genera. The primary variables influencing diatom genus composition at the Salt Plains were found to be the variability of salinity within a site and the overall magnitude of salinity.

We investigated variation of fish assemblages in response to environmental factors using Long Term Resource Monitoring Program data. Data were collected from 1993 to 2000 from five physical habitats in the unimpounded upper Mississippi River. We captured 89 species composing 18 families. Of these, 26% were fluvial specialists, 25% were fluvial dependent and 49% were generalists. The numerically dominant component of the adult fish assemblage (species accounting for >10% of total catch) accounted for 50% of the assemblage and was comprised of only three species: gizzard shad (Dorosoma cepedianum: 25%), common carp (Cyprinus carpio; 15%) and channel catfish (Ictalurus punctatus; 10%). The dominant component of the YOY fish assemblage was comprised of only two species, which accounted for 76% of the total catch: freshwater drum (Aplodinotus grunniens; 39%) and gizzard shad (37%). We used a cross-validation multivariate approach to explore how adult and young-of-the-year (YOY) assemblages varied with respect to physical habitat and environmental gradients. Furthermore, we were interested how the fish assemblages changed over time. Partial canonical correspondence analyses (pCCA) demonstrated significant effects of physical habitats. Such effects differed between young-of-the-year and adult fishes. The four main environmental gradients influencing overall assemblage structure for both age groups were river elevation, water velocity, conductivity and depth of gear deployment. Morisita's index revealed similar adult assemblage structure over time. However, the YOY assemblage present in 1995 was dissimilar from assemblages present during the other years. We speculate this is a lag effect from the backwater spawning episodes (floodpulse) that occurred with the 500-y flood in 1993. Shannon-Weiner diversity and Camargo's evenness indices were low, but stable across years for the adult assemblage, but wafted across years for the YOY assemblage.

Government agencies, private organizations, educational institutions, and the general public are increasingly interested in the preservation, restoration, and use of biodiversity (Harris 1984, Levin 1992, McNeely 1990, Norse et al. [...]

A study of the relationship between plant species richness and spatial scale components in the Oosting Natural Area in Duke Forest, NC, shows that increasing grain size greatly increases species richness, increasing extent of coverage has a positive interactive effect along with grain, and increasing disaggregation increases species richness at a constant rate. A larger grain size and a greater coverage also increase patchiness. The study collected data from 256 one-meter square units, and since it could not vary each of the three factors studied independently of the others, statistical testing of these results was not possible.

The effect of the fractal dimension of a landscape on the coexistence and richness of species is evaluated using simulations of species dynamics. Interactions as affected by the geometrical configuration of the environment are also considered. The effect of landscape variability on coexistence is influenced by species interdependence. Decreasing the spatial dependence allows more organisms to inhabit the landscape. However, very high fractal values result in low species diversity. Diversity and breadth of the habitat are shown to be functions of fractal dimension. These patterns are explained by habitat effects and natural processes affecting the habitat.

We provide algebraic simplifications for the redundancy analysis (RDA) eigenvalue and the canonical correspondence analysis (CCA) eigenvalue in the special case of permanent plots sampled twice. The indices for RDA and CCA are interrelated and are intuitively interpretable. These simplifications also apply to simple split-plot designs and to a balanced design with two independent samples. Key words: canonical correspondence analysis; monitoring; ordination eigenvalues: permanent plots; redundancy analysis; split-plot design.

PCR-denaturing gradient gel analysis was used to evaluate the effects of environmental exposures typically associated with asthma protection or risk on the microbial community structure of household dust. The findings indicated that specific bacterial populations within the bacterial community structure are associated with either risk or protection from asthma.

Ecological Scale: Theory and Applications. David L. Peterson and V. Thomas Parker, eds. Columbia University Press, New York, 1998. 632 pp., illus. $35.00 (ISBN 0-231-10503-7 paper). Although scale has been [...]

DAVID B. CLARK [1,3] MICHAEL W. PALMER [2] DEBORAH A. CLARK [1] (1.) Department of Biology, University of Missouri, 8001 Natural Bridge Road, St. Louis, Missouri 63121 USA (2.) Department [...]

1 Multivariate analysis of complex data sets is plagued by problems of subjectivity and of finding statistically valid ways to test a large number of plausible hypotheses. We show how patterns in the data can be identified (data diving) as well as rigorously tested statistically by subdividing the data set. 2 We analysed data on weed biomass and environmental variables from more than 2000 plots in cereal and oil-seed crops in Sweden during 1970-94. Half the data set was used in an exploratory phase while the other half was used in a subsequent confirmatory phase. 3 The exploratory analyses included multivariate statistics [detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA)] with various options and combinations of variables, and led to the formation of hypotheses that were then tested. 4 We tested the hypotheses in a sequential analysis with CCA and Monte Carlo permutation tests: after establishing the influence of one set of environmental variables, this set was covaried out in subsequent analyses. In this way the influence of (i) season of sowing of the crop; (ii) geographical region; (iii) soil type; (iv) crop species; and (v) temporal trends was tested. The four latter were tested separately for spring- and autumn-sown crops. 5 The sowing season of the crop had an overwhelming influence on the weed flora, and many weed species, both annual and perennial, showed strong associations with either autumn or spring. There were significant differences in weed flora composition between the geographical regions and soil types as well as between crop species. There were significant temporal trends only in the weed flora of autumn-sown crops. 6 This study provides a protocol that combines exploratory `data diving' with strict hypothesis testing using direct gradient analysis methods such as CCA. Such two-phase analysis should improve the way complex data are analysed and patterns are interpreted. Key-words: cross-validation, hypothesis testing, multivariate analysis, Sweden, variation partitioning Journal of Ecology (1999) 87, 1037-1051

We present data that were collected as part of a monitoring project on vascular plant composition at the Tallgrass Prairie Preserve in Osage County, Oklahoma, USA. The purpose of these data are to promote the study of multi-scale patterns of species composition for both theoretical and applied questions. Furthermore, these data will provide a reference point for tallgrass prairie restoration projects in the Flint Hills. Over the course of the 12-year period, we sampled 20 permanent plots annually. The permanent plots were selected semi-randomly from a UTM grid using the criteria that they contain less than 20% of woody cover, standing water, or exposed rock. Plant species presence was recorded at five spatial scales: 0.01, 0.1, 1.0, 10, and 100 [m.sup.2] in each of the four corners of a 100-[m.sup.2] square quadrat. Plant species were assigned to a percent cover class at the 100-[m.sup.2] grain. In addition to information on plant composition, we provide data on topography, soil variables, monthly total rainfall, monthly average temperature, and management records related to fire and grazing history. We hope this data set will stimulate further research into the scaling of biodiversity and insight into the functioning and conservation of tallgrass prairie plant communities. Key words: bison; Flint Hills; restoration: spatial scale; species-time-area relationship; tallgrass prairie; vascular plants; vegetation monitoring.

We present a data set collected in 1989 of vascular plant occurrences in overlapping grids of nested plots in the Oosting Natural Area of the Duke Forest, Orange County, North Carolina, USA. The purpose of these data is to allow the study of vascular plant biodiversity at multiple spatial scales, in terms of both grain and extent. There are eight distinct plot sizes (grains), with size four times that of the next smallest, from 0.015625 [m.sup.2] to 256 [m.sup.2]. Larger grains are possible by aggregating adjacent plots. Extents (linear distances between plots) range from 1 m to 362 m. In addition, trees were mapped over the entire 256 m x 256 m study site in 1990, and again in 1998 to assess the effects of Hurricane Fran in September 1996. Tree species, diameters, and damage descriptors (1998 only) were also recorded. Soils were gathered from the entire grid in 1990 and analyzed for nutrients, pH, and organic matter. These data have already been used to assess scale dependence of plant diversity, to evaluate new methods for the study of spatial scale, and to study the importance of spatial scale on the interpretation of hurricane damage to forests. They are presented as a case study for future scale research. Key words: distance decay; hurricane; North Carolina; soil nutrients; spatial scale; species--area relationships; tree mapping; vascular plants.

Bailey and Gatrell have produced a solid introduction to the field of spatial data analysis. The book focuses on description of pattern, tests of hypotheses, and interpolation, and the authors [...]