Responses of global plant diversity capacity to changes in carbon dioxide concentration and climate.

We model plant species diversity globally by country to show that future plant diversity capacity has a strong dependence on changing climate and carbon dioxide concentration. CO2 increase, through its impact on net primary production and warming is predicted to increase regional diversity capacity, while warming with constant CO2 leads to decreases in diversity capacity. Increased CO2 concentrations are unlikely to counter projected extinctions of endemic species, shown in earlier studies to be more strongly dependent on changing land use patterns than climate per se. Model predictions were tested against (1) contemporary observations of tree species diversity in different biomes, (2) an independent global map of contemporary species diversity and (3) time sequences of plant naturalisation for different locations. Good agreements between model, observations and naturalisation patterns support the suggestion that future diversity capacity increases are likely to be filled from a 'cosmopolitan weed pool' for which migration appears to be an insignificant barrier.

Seed mass, habitat conditions and taxonomic relatedness: a re-analysis of Salisbury (1974).

Re-analysis of data from Salisbury (1974) shows no significant relationship between seed size and habitat conditions, a relationship for which this paper is frequently cited as support. The discrepancy between the results reported here and those found in the original paper is due to Salisbury's 'evidence' being a table of congeneric pairs collected specifically because they possessed the target relationship. This paper emphasizes particularly the need for an unbiased sampling of species pairs in comparisons attempting to define ecological relationships. The analysis presented here represents the fourth such instance in which previously assumed robust examples of the relationship between seed size and habitat type are shown not to be so when the appropriate methods are used to account for relatedness among species.

Seed size and establishment conditions in tropical trees : On the use of taxonomic relatedness in determining ecological patterns.

Within a multi-species study, species do not necessarily represent independent data points. The data set used by Foster and Janson (1985) to look at the relationship between seed size and establishment conditions for naturally occurring tropical trees was re-analyzed, to take into account the effect of relatedness among species. The re-analysis showed that 1) this data set does not support the hypothesis that large-seeded species are more likely to establish in small gaps or shade than are small-seeded species, and 2) more than 1/3 (16 of 39) of the data points were extraneous to the test of the hypothesis. It is recommended that all ecologists, and not just those interested in evolutionary questions, consider species relatedness prior to inception of any multi-species study.

Cervical discography: clinical implications from 12 years of experience.

STUDY DESIGN: Positive pain responses provoked in an inclusive series of cervical discograms performed over a 12-year period were categorized by level and reviewed. OBJECTIVES: To report the prevalence of cervical pathology over an entire series of patients, to determine whether a reproducible pattern of concordant pain could be associated with each symptomatic level identified, and to calculate the rate of complications. SUMMARY OF BACKGROUND DATA: Cloward wrote the first articles explaining the technique of cervical discography and reported on the pain responses induced. Currently, the technique is viewed as an invaluable diagnostic tool, but it also is criticized for failing to contribute unique information beyond that available from imaging studies despite the inherent risks. METHODS: A series of 173 cervical discograms performed over 12 years was examined. Pain responses provoked and recorded during discography were grouped by disc level and examined for recurring patterns. The prevalence of disc pathology was calculated. RESULTS: In all, 807 discs were injected, and 404 concordant pain responses (50%) were elicited. Three or more abnormal disc levels were identified in more than half of the patients. Complications developed in four patients (2.3%). No further complications were reported. Surgical treatment was indicated as viable in only 35 studies. CONCLUSIONS: Discography is a safe and valuable diagnostic procedure showing characteristic pain patterns that may have clinical significance. In more than half of the studies, three or more levels were identified as pain generators, suggesting that treatment decisions based on information from fewer discs injected during discography may be tenuous.

Normative data on the Missouri Children's Picture Series and the Missouri Children's Behavior Checklist with Southern black children.

Normative data are presented for Southern black children on two objective personality inventories for children: the Missouri Children's Picture Series (MCPS), a child picture-sorting task, and the Missouri Children's Behavior Checklist (MBCL), a parent rating scale. The MCPS was administered to 615 black children attending public schools in a low socioeconomic area of the southeast United States. Parents returned the MBCL on 437 of the children. Means and standard deviations on eight MCPS personality scales and six MCBL behavior rating scales are presented for black males and females at ages 5 through 16, and effects of age, sex, and various scale intercorrelations are discussed. Results suggest systematic age and sex differences on the various scales for black children that are quite atypical when compared with the MCPS in other samples. Various empirical questions regarding the validity of these instruments when used with Southern black children are raised.

Seed size and seedling growth: differential response of Australian and British Fabaceae to nutrient limitation.

Seed size is widely held to exert an important influence over plant establishment, but while large seeds are often assumed to be at an advantage in nutrient-limited conditions, there is in fact, little consistent evidence to support this hypothesis. Here, we examined the interspecific relationship between seedling growth and seed size for Australian and British Fabaceae species in nutrient solutions deficient in nitrogen, phosphorus, potassium or all nutrients combined (distilled water). The British species showed no consistent link between mean seed mass and seedling growth in nutrient-limited conditions. By contrast, all four nutrient-deficient treatments yielded a significant relationship for the Australian species. Linear regression showed that growth under balanced nutrient conditions was positively associated with growth without nutrients, although in fewer cases for the British species. We suggest that habitat-specific differences in regeneration conditions and/or evolutionary history may influence the role that seed size plays in dictating how seedlings of different species respond to nutrient shortage. We recommend caution in attempts to link traits like seed size to wider patterns of plant community ecology.

Resource choice in Cuscuta europaea.

Individual stems with growing tips of dodder (Cuscuta europaea) were transplanted onto host plants (hawthorn) of varying nutritional status. The parasite was more likely to coil on ("accept") hosts of high nutritional status and grow away from ("reject") hosts of poor quality. Dodder exhibits this acceptance/rejection response before taking up any food from the host, so it is possible to dissociate active choice from the passive effects of growth and mortality. Probability of acceptance is gauged to expected reward.

The interspecific mass-density relationship and plant geometry.

We present an a priori theoretical framework for the interspecific allometric relationship between stand mass and plant population density. Our model predicts a slope of -1/3 between the logarithm of stand mass and the logarithm of stand density, thus conflicting with a previously assumed slope of -1/2. Our model rests on a heuristic separation of resource-limited living mass and structural mass in the plant body. We point out that because of similar resource requirements among plants of different sizes, a nonzero plant mass-density slope is primarily defined by structural mass. Specifically, the slope is a result of (i) the physical size-dependent relationship between stem width and height, (ii) foliage-dependent demands of conductance, and (iii) the cumulative nature of structural mass. The data support our model, both when the potential sampling bias of taxonomic relatedness is accounted for and when it is not. Independent contrasts analyses show that observed relationships among variables are not significantly different from the assumptions made to build the model or from its a priori predictions. We note that the dependence of the plant mass-density slope on the functions of structural mass provides a cause for the difference from the zero slope found in the animal population mass-density relationship; for the most part, animals do not have a comparable cumulative tissue type.

Species richness and resource availability: a phylogenetic analysis of insects associated with trees.

The data on the number of species of insects associated with various trees in Britain have been reanalyzed to factor out possible bias from phylogenetic effects. It was found that tree availability (range and abundance) continues to provide a good predictor (r = 0. 852) of insect-species richness, slightly better than straightforward cross-species analyses. Of the two components of tree availability, tree abundance gives a much better prediction than tree range. The species richness on trees of major taxa with similar trophic habits (Lepidoptera and Hymenoptera/Symphyta and the two suborders of the Homoptera-Auchenorrhyncha and Sternorrhyncha) shows positive correlations; there is thus no evidence of competitive exclusion at this taxonomic level.

Acquisition order and resource value in Cuscuta attenuata.

Field observations showed that in its native Texas grasslands, dodder (Cuscuta attenuata) grows more vigorously in patches of mixed host species than in monospecific host patches. Field experiments with naturally occurring host individuals demonstrated that the parasite achieved greater volume when simultaneously infesting two hosts of differing species rather than two hosts of the same species, and that this effect depends on the order in which the parasite encounters those hosts. Sodium, acting as an osmoticum, is implicated as the factor responsible for experimentally produced as well as observed field patterns.

Is breaking up hard to do? Breakage, growth, and survival in the parasitic clonal plant Cuscuta corymbosa (Convolvulaceae).

In a tripartite exploration of the effects of traumatic breakage in the parasitic clonal plant Cuscuta corymbosa, experimental breakage had significant negative effects upon stem extension of ramets distal to a break and the level of that effect depended upon the number of ramets in the severed fragment. Regular monitoring of clonal individuals transplanted onto naturally occurring, native host species revealed that breakage in individuals growing under natural conditions ranged from 2 to 66% of all interramet connections and significantly affected distance between ramets and stolon generation in ramets associated with a break. Simulations revealed that these responses to breakage would significantly change the "shape" of a clonal individual in a manner capable of affecting probabilities of encounter with patchily distributed resources. Nonetheless, the observed levels of breakage had no discernible effect on biomass accumulation, although individuals that survived into the dry season and thus gained the potential to reproduce in additional seasons had a significantly lower rate of breakage than those that did not. We suggest that the lack of a relationship between breakage and within-season biomass accumulation is an indication that parasite response to breakage is gauged to expected levels of breakage for the habitat. We note that the capacity of ramets to survive disconnection significantly decreased the loss of tissue that would occur if subunits did not possess the potential to function independently.

Global climate and the distribution of plant biomes.

Biomes are areas of vegetation that are characterized by the same life-form. Traditional definitions of biomes have also included either geographical or climatic descriptors. This approach describes a wide range of biomes that can be correlated with characteristic climatic conditions, or climatic envelopes. The application of remote sensing technology to the frequent observation of biomes has led to a move away from the often subjective definition of biomes to one that is objective. Carefully characterized observations of life-form, by satellite, have been used to reconsider biome classification and their climatic envelopes. Five major tree biomes can be recognized by satellites based on leaf longevity and morphology: needleleaf evergreen, broadleaf evergreen, needleleaf deciduous, broadleaf cold deciduous and broadleaf drought deciduous. Observations indicate that broadleaf drought deciduous vegetation grades substantially into broadleaf evergreen vegetation. The needleleaf deciduous biome occurs in the world's coldest climates, where summer drought and therefore a drought deciduous biome are absent. Traditional biome definitions are quite static, implying no change in their life-form composition with time, within their particular climatic envelopes. However, this is not the case where there has been global ingress of grasslands and croplands into forested vegetation. The global spread of grasses, a new super-biome, was probably initiated 30-45 Myr ago by an increase in global aridity, and was driven by the natural spread of the disturbances of fire and animal grazing. These disturbances have been further extended over the Holocene era by human activities that have increased the land areas available for domestic animal grazing and for growing crops. The current situation is that grasses now occur in most, if not all biomes, and in many areas they dominate and define the biome. Croplands are also increasing, defining a new and relatively recent component to the grassland super-biome. In the case of both grassland and croplands, various forms of disturbance, particularly frequent disturbance, lead to continued range extensions of the biomes.

Rehabits: a common language of functional assessment.

Probabilistic measurement models offered by Rasch and others can be used to link different functional assessment instruments into a single measurement system. This study assessed 54 subjects (diagnoses: 8 brain injuries, 7 neuromuscular, 22 musculoskeletal, 7 spinal cord, 10 stroke) admitted to a free-standing rehabilitation hospital at admission and discharge using both the Functional Independence Measure (FIM) and the Patient Evaluation and Conference System (PECS). Thirteen FIM and 22 PECS motor skills items were scaled together into a 35-item instrument, providing scale values for all items in the same unit of measurement. Separate FIM and PECS measures produced for each subject correlate .94 and .91 (p < .0001), respectively, with the cocalibration measures, and 0.91 (p < .0001) with each other. Either instrument's ratings are easily and quickly converted into the other's using the common unit of measurement, the rehabit (rehabilitation measuring unit). This article argues that the stability of the PECS and FIM item difficulty estimates over thousands of subjects, dozens of hospitals, hundreds of raters, and years of assessment is convincing evidence in support of the widespread use of their cocalibrated, common scale values as a functionometric ruler.