E. Barry Moser

FIRE EFFECTS ON RESPROUTING OF SHRUBS IN HEADWATERS OF SOUTHEASTERN LONGLEAF PINE SAVANNAS

Woody plants in fire-frequented ecosystems commonly resprout from underground organs after fires. Responses to variation in characteristics of fire regimes may be a function of plant physiological status or fire intensity. Although these hypotheses have been explored for trees in southeastern longleaf pine (Pinus palustris) savannas, responses of other life forms and stages have not been studied. We examined effects of fire season and frequency, geography, habitat, and underground organ morphology on resprouting of shrubs. In 1994, we located replicated sites, each containing two habitats, upslope savannas and downslope seepages, in Louisiana and Florida. Each site, which contained quadrats located along transects within a 30 × 60 m plot, was burned either during the dormant or growing season and then reburned similarly two years later. Maximum fire temperatures were measured, and densities of shrub stems were censused in quadrats before and after fires. Shrubs collectively resprouted more following dorma...

Spatial variability of soil nutrients in disturbed riverine mangrove forests at different stages of regeneration in the San Juan River estuary, Venezuela

Geostatistical analysis of selected soil properties were performed in two mangrove sites (B7 and B9) dominated by the mangrove speciesRhizophora mangle along the San Juan River, Venezuela, to evaluate the effect of forest disturbance on nutrient spatial distributions. Plots within area B7 were clear-cut in 1972–1973 and in area B9 in 1982–1983. Four plots within each area were systematically selected and represented natural (2) and regenerated (2) forests. Individual plots were 1.5 ha in B7 and 1.25 ha in B9 and sampled at a resolution of 25 m. Soil samples were obtained at the intersection of an aligned grid with 90 points in B7 and 78 points in B9. Measured soil properties included salinity, total nitrogen, total carbon, total phosphorus, osmolality, and pore water cation concentrations (potassium, calcium, magnesium, and sodium). Sites were sampled in May 1996 and 1997, although spatial analysis was performed only for the data obtained in May 1997. Geostatistical analysis showed that most of the variables tested were spatially auto-correlated within each area and that there were no differences between regenerated and natural plots. Structural variance as a proportion of sample variance ranged from 55–99% for most of the properties. The significant spatial dependence observed for most of the variables in natural and regenerated plots, despite management schedules, indicates that clear-cutting did not have an effect on modifying the distribution of nutrient concentrations. These results suggest that after 15 and 25 yr following forest disturbance nutrient distributions were reestablished either there was not a net effect on patterns of element loss or tidal input was stronger than plant modifications of soils.

Community structure along elevation gradients in headwater regions of longleaf pine savannas

Savanna community structure has been described mostly at the regionallevel worldwide. Quantitative descriptions of vegetation patterns andrelationships with substrate characteristics at more localized scales havereceived less attention. Our primary objective was to examine the distributionsof herbs and shrubs/trees along local topographic gradients in headwaterregions of longleaf pine savannas in the southeastern United States. We alsoexamined whether herb patterns were structurally similar to those ofshrubs/trees along the same topographic gradients and whether patterns werecorrelated with edaphic factors. Abundance data were collected within quadratsplaced along transects from upslope savannas through mid-slope seepage bogsintolower-slope shrub/tree zones within Louisiana and Florida. β-flexiblecluster analysis and nonmetric multidimensional scaling were used to delineateherbaceous species communities. Ordination was performed separately onshrub/tree abundance data. The herb-based classifications were also used todelineate shrub/tree communities, providing an indirect means of comparingherb to shrub/tree distributions. In Louisiana, three herbaceouscommunitieswere sharply delineated along elevation gradients of several meters and werestrongly correleated with soil moisture. In Florida, three similar herbaceouscommunities were less discrete along elevation gradients of <1 meter.In both regions, shrub/tree distributions were much broader and appearedless sensitive than herbs to changes in environmental gradients. Coefficientsofvariation indicated that, in general, herbaceous species were more narrowlydistributed than shrubs/trees along localized elevation gradients in bothLouisiana and Florida. Alterations of fire regimes (fire suppression,dormant-season fires) may have resulted in expanded distributions ofshrubs/trees, but not herbs.

Using Mental Imagery to Enhance Gifted Elementary Students' Creative Writing.

ABSTRACT The purpose of the present research was to examine the effects of mental imagery instruction on gifted elementary students’ creative writing and development of imagery vividness. Thirty‐seven fourth‐and fifth‐grade students were assigned to either a treatment or a control group and then participated in four group lessons over a two‐week period. Treatment subjects received instruction and practice in imagery usage through researcher‐developed passages that embedded highly imaginal sensory descriptions. Control subjects listened and responded to childrens stories. Following each lesson, both groups completed creative writing assignments. To assess the effects of the treatment, two pretest‐posttest tasks were given, a creative writing sample and a survey of imagery vividness. On the creative writing task, treatment subjects significantly outperformed control subjects on originality and use of sensory descriptions but not on writing length. In addition, both groups significantly improved on the vivi...

Worm holes and their space-time continuum: Spatial and temporal variability of macroinfaunal annelids in a Northern New England salt marsh

Coastal systems serve many human uses and as a result are susceptible to anthropogenic activities such as nutrient loading and overfishing. In soft sediments, infauna frequently serve as key indicators of such activities. To use infauna effectively as bioindicators, it is important to understand how infaunal abundances and community patterns vary naturally within ecosystems. We examined the spatial and temporal dynamics of infaunal annelids in four tidal creeks of the Plum Island Estuary, Massachusetts, USA, from June to October 2003, sampling along a tidal inundation gradient that crossed five distinct habitats from creek bottoms to the vegetated high marsh platform. Annelids comprised 97% of the total number of macroinfauna. Highest densities were found in creek wall habitats (33,418–65,535 individuals m−2), and lowest densities (2,421–10,668 individuals m−2) were found inSpartina patens habitats. Five numerically abundant species comprised 87% of the annelid assemblage and three species,Manayunkia aestuarina (Polychaeta),Paranais litoralis (Oligochaeta), andCernosvitoviella immota (Oligochaeta), were broadly distributed across the marsh landscape.Streblospio benedicti (Polychaeta) andFabricia sabella (Polychaeta) were abundant only in mudflat and creek wall habitats, respectively.P. litoralis experienced a summer decline in all habitats, whereasM. aestuarina abundance increased 4–5 fold, in October relative to June in creek wall and tall-formSpartina alterniflora habitats. Hierarchical spatial, analysis revealed that >90% of the variability in annelid abundances was found at the mesospatial scale (<50 m). Variation among the four creeks, (>1 km) was relatively small.

Effects of backpack and implanted radiotransmitters on captive blue-winged teal

Radiotelemetry is frequently used for research on waterfowl, but some transmitter designs alter reproductive effort, behavior, and mass of birds. Quantitative comparisons of transmitter effects are needed so rescarchers can use instruments least likely to generate biased results. We compared body mass and behavior of captive blue-winged teal (Auds discors) females fitted with either a backpack-harness transmitter, abdominally implanted device or no racho over a 12-week period. Females with implants lost mass during the first week following surgery, while backpack-marked and control birds gained mass (P = 0.02). Mass of implanted birds recovered by the second week after surgery, and never differed among treatment groups over the subsequent 11 weeks (P ≥ 0.51) Females with backpack transmitters spent more time on comfort movements (P 0.18), feeding (P ≥ 0.10). or on locomotion (P ≥ 0.18). except that backpack-marked females spent less time engaged in locomotion than did implanted females (P = 0.03). Out results corroborate previous studics showing effects of backpack-harness transmitters on behavior. We demonstrated that implants do not affect behavior, but are associated with a temporary post-surgical loss of mass The alteration of behavior eaused by backpack tranmitters did not diminish with time, so researchers should not assume that an adjustment period is sufficient to climinate transmitter effects.

AGGREGATION AND THE PEARSON CHI-SQUARE STATISTIC FOR HOMOGENEOUS PROPORTIONS AND DISTRIBUTIONS IN ECOLOGY'

The null hypothesis that the proportions or relative abundance among j mutually exclusive categories (e.g., species or sizes) is the same for two or more populations (e.g., locations or sexes, respectively) is often tested with the Pearson chi-square goodness- of-fit statistic. The chi-square statistic is derived under the assumption that the objects counted are independently and identically distributed. Count data from samples of clusters or groups of objects, for example, with transects, grabs, trawls, and quadrats usually fail to meet these assumptions. Many articles appear in the ecological literature that fail to realize the implications of violating the assumptions implicit in the use of the chi-square distribution test of homogeneity of proportions. Species aggregation, alone and in com- bination with increased mean abundance, and a large number of categories are shown to increase Type I error rates. Pooling several samples to get a representative sample does not solve the problem for <14 replicate samples for ecologically plausible levels of ag- gregation. An easily implemented solution is suggested.

Effects of weather and tides on feeding and flock positions of wintering redheads in the Chandeleur Sound, Louisiana

We studied the effects of weather and tides on percent feeding and flock positions of wintering redheads (Aythya americana Eyton) in the Chandeleur Sound, Louisiana, USA. Flock scans (n = 750) were made on 55 flocks from November through March of 1988–1989. The percent of the flock that was feeding was negatively correlated with time of day, temperature, water level, and distance of the flock from shore, and was positively correlated with wind velocity, flock size, fetch, and wave height; birds also fed more in early winter and during northerly winds. Flocks were closer to land earlier in the winter on cloudy, rainy, and windy days when waves were high, and those flocks were smaller than flocks farther from shore. Conditions associated with reduced fetch by flocks included later time of day, smaller waves, warmer air temperatures, northerly wind shifts, stronger winds, increasing cloud cover, and rain. Redheads minimized energy expenditure by foraging during low tides and in shallow water closer to shore; they increased feeding and reduced fetch during times of high thermoregulatory demands.

Diurnal time-activity budgets of redheads ( Aythya americana ) wintering in seagrass beds and coastal ponds in Louisiana and Texas

Diurnal time-activity budgets were determined for wintering redheads (Aythya americana) from estuarine seagrass beds in Louisiana (Chandeleur Sound) and Texas (Laguna Madre) and from ponds adjacent to the Laguna Madre. Activities differed (p<0.0001) by location, month, and diurnal time period. Resting and feeding were the most frequent activities of redheads at the two estuarine sites, whereas drinking was almost nonexistent. Birds on ponds in Texas engaged most frequently in resting and drinking, but feeding was very infrequent. Redheads from the Louisiana estuarine site rested less than birds in Texas at either the Laguna Madre or freshwater ponds. Redheads in Louisiana fed more than birds in Texas; this was partially because of weather differences (colder temperatures in Louisiana), but the location effect was still significant even when we adjusted the model for weather effects. Redheads in Louisiana showed increased resting and decreased feeding as winter progressed, but redheads in Texas did not exhibit a seasonal pattern in either resting or feeding. In Louisiana, birds maintained a high level of feeding activity during the early morning throughout the winter, whereas afternoon feeding tapered off in mid- to late-winter. Texas birds showed a shift from morning feeding in early winter to afternoon feeding in late winter. Males and females at both Chandeleur Sound and Laguna Madre showed differences in their activities, but because the absolute difference seldom exceeded 2%, biological significance is questionable. Diurnal time-activity budgets of redheads on the wintering grounds are influenced by water salinities and the use of dietary fresh water, as well as by weather conditions, tides, and perhaps vegetation differences between sites. The opportunity to osmoregulate via dietary freshwater, vs. via nasal salt glands, may have a significant effect on behavioral allocations.

A Note on the Updating of Regression Estimates

Abstract We present a general approach to the derivation of changes in regression coefficient estimates and their covariance matrix due to addition or deletion of independent or correlated observations, re weighing of observations, and general changes in the covariance structure of the model. These results are useful in the area of regression diagnostics and the updating of regression estimates.