Habitat Physiognomy Research Articles

Phytolith Palaeoenvironments at Mumba Rock Shelter

The rock shelter site of Mumba in northern Tanzania plays a pivotal role in the overall study of the late Pleistocene archaeology of East Africa with an emphasis on the Middle to Later Stone Age transition. We used phytolith analysis to reconstruct general plant habitat physiognomy around the site from the onset of the late Pleistocene to recent times, tallying 4246 individual phytoliths from 19 archaeological samples. Statistical analysis explored phytolith richness, diversity, dominance, and evenness, along with principal components to compare phytolith distributions over the site’s sequence with known plant habitats today. Generally, the phytolith record of Mumba signifies paleoenvironments with analogs in the Somalia – Masai bushland and grassland, as well as Zambezian woodlands.

Vulnerability to climate change of a microendemic lizard species from the central Andes

Given the rapid loss of biodiversity as consequence of climate change, greater knowledge of ecophysiological and natural history traits are crucial to determine which environmental factors induce stress and drive the decline of threatened species. Liolaemus montanezi (Liolaemidae), a xeric-adapted lizard occurring only in a small geographic range in west-central Argentina, constitutes an excellent model for studies on the threats of climate change on such microendemic species. We describe field data on activity patterns, use of microhabitat, behavioral thermoregulation, and physiology to produce species distribution models (SDMs) based on climate and ecophysiological data. Liolaemus montanezi inhabits a thermally harsh environment which remarkably impacts their activity and thermoregulation. The species shows a daily bimodal pattern of activity and mostly occupies shaded microenvironments. Although the individuals thermoregulate at body temperatures below their thermal preference they avoid high-temperature microenvironments probably to avoid overheating. The population currently persists because of the important role of the habitat physiognomy and not because of niche tracking, seemingly prevented by major rivers that form boundaries of their geographic range. We found evidence of habitat opportunities in the current range and adjacent areas that will likely remain suitable to the year 2070, reinforcing the relevance of the river floodplain for the species’ avoidance of extinction.

Habitat and soil associations of a fossorial toad in a Sonoran Desert riparian forest

Despite occupying small land areas, riparian systems provision a large number of vertebrates, including amphibians, one of the most threatened vertebrate taxa. We associated capture rates of a fossorial desert anuran (Scaphiopus couchii) to non-native plant invasion and shrub encroachment via soil traits and habitat physiognomy in native, invaded, and shrub-encroached riparian habitats in the Sonoran Desert. We measured habitat and anurans at 18 sites along the San Pedro and Gila Rivers in three stand types based on dominant trees, cottonwood-willow forest (Populus-Salix), mesquite woodland (Prosopis), and non-native saltcedar stands (Tamarix). Dominant tree species were useful descriptors of habitat physiognomy. Spadefoots were associated with xeroriparian habitat at Prosopis sites and nearly absent from Tamarix sites. Soil moisture and texture heavily influenced spadefoot partitioning across forest types. Altering in-stream flow has modified riparian areas by causing xerification, Prosopis expansion, and proliferation of non-native species. The effects of Prosopis encroachment on this fossorial anuran may be less than Tamarix invasion, which could be deleterious to many anurans. We suggest monitoring vulnerable amphibians and conservation measures to preserve native riparian habitat.

Prescribed fire maintains host plants of a rare grassland butterfly

As grassland ecosystems transform globally due to anthropogenic pressures, improvements in our understanding of the effect of management on rare and threatened species in such landscapes has become urgent. Although prescribed fire is a very efficient tool for habitat restoration and endangered species management on fire-adapted ecosystems, the specific mechanisms underlying potential effects of burning on population dynamics of butterfly host plants are poorly understood. We analyzed a 12-year dataset (2004–2015), combining violet abundance, habitat physiognomy and fire history data from a fire-managed system, to determine factors influencing the spatiotemporal distribution and abundance of violets (Viola spp.), the host plants of the threatened eastern regal fritillary (Speyeria idalia idalia) butterfly. Our results demonstrate a critical role for fire in driving both presence and abundance of violets, suggesting management with prescribed fires can effectively promote butterfly host plants. In addition, we determined the character of habitats associated with violet presence and abundance, in particular a strong positive association with biocrusts. These results provide a roadmap for efficient site selection to increase the effectiveness of restoration efforts, including assessment of potential reintroduction sites for regal fritillary and other grassland butterflies and actions to promote the re-establishment of host plants in these sites.

Do novel ecosystems provide habitat value for wildlife? Revisiting the physiognomy vs. floristics debate

AbstractAlthough novel ecosystems are increasing globally, their utility for biodiversity conservation is poorly understood. Native fauna are predicted to use novel ecosystems when those ecosystems provide structure and resources similar to the native habitat. We modified existing terminology on wildlife functional groups to develop a conceptual model that illustrates fundamental differences in how native wildlife respond to novel ecosystems: novel ecosystem avoiders, novel ecosystem utilizers, and novel ecosystem flourishers. We postulate that species membership in these functional groups is related to the relative importance habitat physiognomy and floristics play in habitat selection cues. An excellent opportunity to test this conceptual model exists with birds in historic and novel ecosystems. A long‐standing, equivocal literature investigating relative contribution of physiognomy vs. floristics to avian abundance and community diversity in native ecosystems exists. Using data from grassland and woodland biomes in western North America (Oregon, USA) and Western Australia, respectively, we evaluated use of habitats by indigenous bird species in relation to physiognomy and floristics. Our two case studies represent two extremes on the novelty spectrum: (1) urban gardens in the metropolitan region of Perth, Western Australia, which are designed ecosystems that vary in the percentage of native plantings; and (2) the Zumwalt Prairie in northeastern Oregon where native grassland plants still dominate the ecosystem but non‐native plants are present and available for use as breeding sites. Using an information‐theoretic perspective, we asked whether habitat use based on occurrence (Perth gardens) or breeding success (Oregon grassland) was best explained by physiognomy, floristics, or both. Using these two case studies, our evidence shows that species or guilds within a community will not respond equally to novelty as predicted. We found strong evidence for only one taxon showing sensitivity to floristics and two to physiognomy. All taxa considered were either grouped as novel ecosystem avoiders or utilizers; no flourishers were identified. These results suggest novel ecosystems providing appropriate physiognomy can provision suitable habitat for some taxa.

Invasive woody plants affect the composition of native lizard and small mammal communities in riparian woodlands

AbstractNonnative Tamarix spp. (saltcedar) is among the most invasive and common trees along riparian habitats in the western U S, impacting native plant communities and habitat quality. Tamarix dominance causes a reduction in habitat physiognomic heterogeneity in riparian habitats. Animal abundance, diversity and habitat associations in monotypic stands of saltcedar remain largely unexplored for non‐avian communities. We sampled small vertebrate and ground arthropod communities in monotypic Tamarix stands and in mixed stands of Tamarix and native (Populus, Salix, and Prosopis spp.) trees in riparian habitats along the Virgin River in the Mojave Desert. Our survey of faunal communities suggests that many species of arthropods, reptiles and small mammals utilize both Tamarix‐dominated and mixed habitats along the Virgin River. Small mammal and lizard communities were dominated by generalist species. Mixed stands had greater arthropod abundance, lizard abundance and small mammal diversity; whereas, monotypic and mixed stands had similar lizard diversity. The habitat of mixed sites was characterized by ‘nativeness’ (areas with native riparian trees) and less ‘shady exotic thickets’ (areas with Tamarix and high overstory cover) compared to Tamarix‐dominated stands. There were species‐specific responses to habitat physiognomy. Peromyscus maniculatus (deer mouse) was associated with shady exotic thickets. Sceloporus magister (desert spiny lizard) and Neotoma lepida (desert woodrat) were associated with native trees and woody debris. Seven rodent and lizard species’ abundances were explained by habitat physiognomy variables. Rare and specialist species were more impacted by nonnative vegetation. These results contribute to the body of research on animal utilization of nonnative habitats and relation to habitat physiognomy. Management of nonnative plants should consider how control activities could impact habitat physiognomy and native animal communities in riparian habitat.

Habitat preference studies of some species of the genus Isophya Brunner von Wattenwyl, 1878 (Orthoptera: Phaneropteridae) in the western part of the Carpathian Basin

Species of the tettigoniid genus Isophya are indicators of biogeographical history and also measures of the state of nature conservation in the Carpathian Basin and in Europe. We surveyed the occurrence and habitat preference of five species (I. camptoxypha, I. costata, I. kraussii, I. modesta, I. modestior) living in the Transdanubian region (the western part of the Pannonian biogeographical region) to determine the potential for the preservation of the insects and their habitats. Statistical analysis shows the optimal habitats of I. camptoxypha are patches of herbaceous plants and lower shrub layers within natural forests dominated by tall or medium-height broad-leafed (mainly dicotyledonous) mesophytic forest species. For I. camptoxypha smaller clearings, and the forest ecotones containing the aforementioned plant species are suboptimal, and populations of the insect species occur there at a significantly lower density. Present-day I. costata find optimal conditions in highly natural, loess grasslands or mesophytic hayfields and steppe grassland–hayfield transitions rich in plant species. This same Isophya species at a lower density can be found in grasslands having suboptimal conditions, but with a similar habitat physiognomy, adjoining the abovementioned grasslands or developing through their slight degradation. Based on a critical literature review and our own sampling, we also comment on the habitat choice of a further three species (I. kraussii, I. modesta, I. modestior).

Lizard species distributions and habitat occupation along an urban gradient in Tucson, Arizona, USA

Despite expanding human populations in metropolitan areas world-wide, habitat relationships of lizards have seldom been examined along urban gradients. We tested three hypotheses addressing lizard species distributions, site occupation, and assemblage organization along the urban gradient in Tucson, Arizona, USA. One hundred twenty-nine random sampling plots were distributed from undisturbed-natural land beyond the boundary of development to highly developed land within the city. We recorded lizard species abundances and 19 variables describing habitat physiognomy, floristics, and spatial relationships of native remnant and developed land parcels in each plot. We ordinated lizard species and habitat data in a canonical correspondence analysis, and tested significance of relationships in a Monte Carlo randomization test. We then tested effects of individual habitat features on site occupation by lizards using a presence–absence transformation of lizard abundance data and multiple logistic regression. Both species distributions and site occupation were influenced by factors describing habitat physiognomy, floristics, and landscape spatial relationships. Finally, we examined total abundance, number of species, and evenness across five categories describing increasing residential density. All three measures of assemblage organization peaked at low–moderate levels of development, and declined markedly as residential density increased beyond moderate levels. Distinct attributes of urban development influence lizard species distributions, site occupation, and assemblage organization. Attention to these attributes will allow land developers to mitigate the effects of future urban development on lizard populations.

RELATIONSHIPS AMONG BREEDING BIRDS, HABITAT, AND RESIDENTIAL DEVELOPMENT IN GREATER TUCSON, ARIZONA

Bird abundance trends have been correlated with habitat changes in urban developed areas but have seldom been associated with specific patterns of urban-related habitat changes. We examined breeding bird–habitat relationships in 334 random plots ranging from undisturbed natural to highly developed land in Tucson, Arizona. In each plot we quantified 19 variables describing three land cover patterns (habitat physiognomy, floristics, and spatial relationships of native habitat fragments) and correlated them with abundances of 21 bird species. Abundances of 17 bird species were associated with variables describing land cover pattern. In addition, we correlated abundance, species richness, and evenness for three bird guilds (non-natives, natives, and a native indicator guild) with land cover variables. Housing density best explained the variation in species richness for both the non-native (r2 = 0.79) and the indicator guilds (r2 = −0.69), whereas area of Upland Sonoran vegetative cover (r2 = 0.56) and distance from undisturbed washes (r2 = −0.56) correlated most strongly with the native-bird group. Finally, we developed and tested regression models predicting species richness for each bird guild. The following variables loaded into the predictive models: house density; percentage cover of paved areas; exotic, Upland Sonoran, and undisturbed riparian vegetation; and distance from undisturbed washes. The models explained 71% of the variation in non-native bird species richness, 56% of the variation in native bird species richness, and 60% of the variation in species richness for the indicator guild of birds. The correlations and regression models can be used to predict species richness responses to future residential development in the Tucson area.

Spatial and temporal patterns of granivorous ant seed predation in patchy cereal crop areas of central Spain.

Patterns of granivorous ant seed predation in extensive cereal croplands of central Spain were investigated by measuring seed removal rates on artificial seed patches. Sampling was designed to cope with the seasonal and daily foraging cycle of ant colonies. Simultaneously with removal rates, I measured seed availability, habitat physiognomy at two spatial scales (landscape and microhabitat), weather variables (temperature and rainfall), and distance to the nearest ant nest. Ant seed predation was concentrated on shrublands, and associated with places with high covers of shrubs, chamaephytes and stones. These results were in close agreement with those obtained by analyzing the spatial distribution of granivorous ant nests (Díaz 1991). Moreover, there was a close relationship between seed removal rates and distance to the nearest ant nest, that fitted the predictions of the optimal foraging model developed by Reyes-López (1987). Seasonal and daily patterns of ant foraging activity seemed to depend more on endogenous factors than on environmental variation. I conclude that ants were not able to track the spatial and temporal variation of their food resources in these man-modified habitats, so that their potential to interact with other members of the granivore system is greatly reduced by human activities.

Rodent seed predation in cereal crop areas of central Spain: effects of physiognomy, food availability, and predation risk

Patterns of rodent seed predation in extensive cereal croplands of central Spain were investigated by measuring rodent predation rates on artificial seed patches, together with seed availability, rodent abundance and habitat physiognomy Sampling was designed to cope with the spatial and temporal variability of factors potentially affecting rodent activity (natural and man‐made habitat features, season and moonlight) Rodent predation was unpredictably distributed in summer In winter, rodents foraged on average in the patches least used by man. moonlight, however, did alter this pattern, so that rodent predation was closely associated with shrubs in the bright nights and evenly distributed in the dark ones I conclude that the need of stable underground refuges and predation risk in the winter period seemed to be the mam factors constraining rodent foraging activity in the man‐made ecosystem studied

Spatial patterns of granivorous ant nest abundance and nest site selection in agricultural landscapes of Central Spain

Patterns of abundance and site selection of granivorous ant nests were investigated in extensive cereal croplands of Central Spain. Nest densities and distributions were measured in two consecutive summers (1988 and 1989), together with habitat physiognomy and seed availability. Nest site selection patterns were analysed at two spatial scales (landscape and microhabitat) with respect to habitat physiognomy. Results indicate a very constant and predictable pattern of both nest abundance and nest site selection. Granivorous ant nests were most abundant in shrublands, and shrubby microsites were selected for nest placement. Croplands, and microsites with high covers of bare ground and litter, were avoided. These patterns were consistent between years despite a 1.7-fold increase in shrubland nest densities, that was attributed to the exceptionally dry winter between nest censuses. I suggest that winter survivorship of ant nests in the unploughed landscape units, and periodic ploughing in croplands, may be the main factors constraining granivorous ant densities in the landscape studied.

Nest-Site Selection of American Oystercatchers (Haematopus palliatus) in Salt Marshes

Nest-Site Selection of American Oystercatchers (Haematopus palliatus) in Salt Marshes

The Role of Habitat Complexity and Heterogeneity in Structuring Tropical Mammal Communities

The relationship between mammal community structure and vertical variation in habitat physiognomy (complexity) and horizontal variation in habitat form (heterogeneity) was examined on five study areas in the llanos of Venezuela. Data on the small mammal (<1 kg) of the study sites were obtained through a mark—recapture trapping program of >38 000 trap nights from 1976—1978. Data on the distribution of large, nonvolant mammals were obtained during 24 mo of field observation. Measures of habitat complexity and habitat heterogeneity were derived using principal components analysis. There was little association between habitat structure and the richness, diversity, abundance, and biomass of small mammals. Abiotic factors, such as the degree of wet—season flooding, probably play an important role in patterns of small mammal distribution and abundance. The total number of mammal species was positively correlated with habitat complexity but not correlated with habitat heterogeneity. Increasing species richness across the complexity gradient was probably accommodated by increasing potential food resources. New species were added to complex communities primarily through guild expansion rather than guild addition.

Habitat Associations and Community Structure of Birds in Shrubsteppe Environments

We studied the relations between bird distribution and abundance and habitat characteristics at a regional scale of investigation, using surveys conducted over three consecutive years on 14 plots at nine locations in the shrubsteppe of the northwestern Great Basin of North America. Bivariate and multivariate analyses revealed no large suites of bird species that were correlated in their distribution and abundance, and few associations existed between pairs of species, suggesting that bird populations in this system vary largely independently of one another. Both bivariate and multivariate correlational analyses between birds and habitat physiognomy indicated that the bird species that were widely distributed in this shrubsteppe system had few significant associations with habitat features, while species with more localized distributions did exhibit habitat affinities, most notably with a suite of characters associated with the occurrence of rocky outcrops. Bird species whose primary distributions and habitat affinities lie in grassland regions to the east demonstrated the greatest degree of correlation with features of habitat physiognomy in this shrubsteppe region, increasing in abundance as vegetation coverage and stature increased and horizontal heterogeneity of habitats decreased. Some bird species, however, exhibited no correlations with the habitat features we measured, and multivariate analyses comparing variation in the bird abundances with variation in features of habitat physiognomy accounted for &lt;17% of the overall variation in the bird abundance matrix. Consideration of coverages of different species of shrubs, however, generally produced more significant correlations with variations in bird abundances, especially for the widespread shrubsteppe species. Attributes of avian community structure varied among the locations surveyed. Variations in the abundance of Brewer's Sparrows, the most abundant species at most sites, accounted for 86% of the variation in total avian density. Species diversity was negatively correlated with total density (presumably because of the overwhelming influence of one species on density) but positively correlated with species richness. Richness variations, in turn, were a consequence of variations in the abundances of several locally distributed shrubsteppe species or grassland species. Richness decreased with increasing horizontal habitat heterogeneity and general vegetation sparseness, but increased with increasing structural diversity of the habitat. Variations in avian community biomass were largely a function of abundances of the widespread or peripheral species; none of the local shrubsteppe forms that contributed so much to species richness was correlated with total biomass variations. We compare the findings of these regional—scale analyses with those of a continental—scale study that included a habitat spectrum ranging from shrubsteppe through tallgrass prairies. Bird species exhibited different patterns of habitat correlations on the two spatial scales. In particular, the characteristic shrubsteppe species showed strong correlations with features of habitat physiognomy in the continental analysis, but in the regional study such associations were generally lacking and these birds instead were correlated with the coverages of various shrub species. This suggests that at a large scale, between—habitat level of analysis these birds may respond to some elements of general habitat configuration, but their within—habitat responses may be more strongly associated with details of habitat floristics. These results complicate studies of avian community/habitat relationships: complete understanding of ecological patterns apparently requires knowledge of vegetational floristics as well as physiognomy; the response of birds to habitat characteristics, and the habitat features that are important, may differ at different scales of spatial resolution. At both spatial scales, however, a substantial portion of the variation in avian abundance remains unexplained after consideration of habitat features. Relatively few significant correlations thus emerge, increasing the probability that those that are revealed may well be spurious, and reinforcing the view that biotic interactions such as competition probably play a minor role in structuring these communities.

Temporal variation in habitat structure and shrubsteppe bird dynamics.

We investigate the role of temporal variation in habitat physiognomy in influencing the dynamics of shrubsteppe bird populations and communities. During a 3-y (1977-1979) study of 14 sites in the northern Great Basin of North America, annual precipitation varied substantially, with one of the driest years on record followed by one of the wettest. This resulted in significant physiognomic variation (increasing height and coverage of vegetation, decreasing horizontal patchiness), mediated largely by changes in the annual elements of the flora, particularly forbs and grasses. Shrub species coverage values, on the other hand, demonstrated no statistically detectable year-to-year changes, nor were they correlated with any physiognomic variation. Despite large scale physiognomic changes, no bird species' abundance varied in a statistically significant fashion; neither could variation in bird abundances be correlated with variation in either physiognomy or shrub species coverages.Multivariate analyses revealed essentially the same patterns as the univariate analyses: substantial changes in physiognomy, few changes in shrub species coverages or bird species abundances, and little correlation of temporal variation among the three data sets. Calculation of the Euclidean distances that sites "moved" in multivariate physiognomic, bird species, or shrub species hyperspaces yields synthetic gradients of annual "turnover" of sites with respect to those data sets. Sites identified as demonstrating high physiognomic turnover were characterized by high coverage of grass and forbs, while low turnover sites had greater coverage of shrubs and higher shrub species diversity. Relatively high bird turnover sites had greater numbers of Western Meadowlarks and Black-throated Sparrows, while more stable sites had high numbers of Brewer's Sparrows. Physiognomically, high bird turnover sites were grassier and had greater total vegetation coverage, while low bird turnover sites had more bare ground and higher horizontal patchiness. A site's position on the avifauna turnover axis, however, was uncorrelated with its position on the physiognomic turnover axis. Shrub species showed virtually no annual turnover.Reanalysis of a previous Principal Components Analysis (PCA) of these same data sets that was applied without regard to year of sampling revealed that the first physiognomic component (41% of the total physiognomic variability) did in fact have a strong temporal element, and that this element was consistent with the changes in univariate characters noted above. No other physiognomic component could be associated with annual variation, nor could any components of parallel bird abundance or shrub species coverage PCA's.Regional patterns indicate that sites tended to be very consistent from year to year in their relationships to one another as defined by their relative locations in either physiognomic or shrub species hyperspaces, but varied independently of one another with respect to their bird species abundances and composition. Examination of the temporal consistency of site relationships between "bird space" and "vegetation space" reveals that bird communities are to a large degree independent of a site's physiognomic position, but instead are strongly associated with its position in shrub species hyperspace.The overall patterns that emerge from these analyses are consistent with the so-called "checkerboard effect" that results from the apparently random annual redistribution of individual birds, and leads to the conclusion that populations of shrubsteppe birds are not existing at maximum density or "carrying capacity." Such observations are consistent with contentions that these populations lack close biological coupling with coexisting species and that interactions among these species (e.g. competition) are likely to play little if any role in the organization of their communities.