Amount Of Woody Vegetation Research Articles

High‐, medium‐, and low‐dispersal animal taxa communities in fragmented urban grasslands

AbstractUrbanized areas are rapidly expanding into a variety of habitats. Urbanization and suburbanization are often associated with changes in biodiversity, which are naturally influenced by biotic interactions and abiotic habitat characteristics. The main cause of changes caused by suburbanization is fragmentation. Its impacts vary between animals with different dispersal abilities. We focused on studying the responses of three taxa with different dispersal abilities: birds as a relatively high‐dispersal taxon, medium‐dispersal butterflies, and low‐dispersal land snails. We studied how biotic factors as well as habitat structural and fragmentation characteristics explain the community composition of the three study taxa in urban grasslands in the city of Pardubice (Czech Republic). Birds were the most species‐rich taxon followed by butterflies. Land snails had species‐poor grassland communities. Species composition analysis indicated species overlap among the studied taxa. Bird species composition covaried with butterfly species richness and reciprocally. Both taxa were significantly influenced by the amount of woody vegetation within the grassland. Bird community composition was also influenced by fragmentation characteristics, namely the distance to the nearest built‐up area. Urban growth most likely leads to changes in the characteristics of animal communities associated with former lowland natural grasslands, deteriorating the communities of low‐dispersal land snails while allowing birds that have generally higher dispersal abilities to thrive. Our results show that in assessing the impact of urbanization on biodiversity, attention should also be paid to low‐dispersal animal taxa.

The conversion of natural riparian forests into agricultural land affects ecological processes in Atlantic forest streams

Agricultural practices affect the integrity of riparian areas of small streams. In this study we tested the hypothesis that the increase of agricultural activities influences negatively the functional conditions of the low order streams in the Atlantic forest of southern Brazil. Litter bags with leaves of Nectandra megapotamica (Spreng.) Mez were located in eight streams with different amounts of woody vegetation and agriculture land uses in their riparian zones. After 7, 15 and 30 days, the litter bags were removed for identification of associated invertebrates and determination of decomposition rate. Decomposition rates were negatively influenced by agriculture in the riparian zone while primary production was positively influenced. On the other hand, the decomposition mediated by microorganisms did not vary along the degradation gradient. The abundance of collectors increased in streams adjacent to agricultural land while the abundance of shredders was decreased. Our results showed that algae biomass and leaf decomposition were sensitive to the replacement of native vegetation by agricultural use. However, the trophic structure of invertebrates was moderately sensitive to agricultural land use.

Habitat-Dependency of Transect Walk and Pan Trap Methods for Bee Sampling in Farmlands

Abstract Bees are the most important group of flower visitors providing an essential ecosystem service, namely pollination. Due to the worldwide decline of bees, there should be standardized sampling methods in place to ensure consistent and comparable results between studies. We compared the two commonly used sampling methods of yellow pan traps and transect walk to determine (i) which habitat variables affect the species composition, abundance and species richness of sampled bee communities, (ii) which method potentially contains sampling bias towards some individuals or groups of bees and (iii) the efficiency of sampling in various habitats. We conducted fieldwork in different agricultural habitats distributed along landscape heterogeneity and topography gradients. Our results showed that the height of vegetation, the average number of flowers and the amount of woody vegetation had the greatest influence on the sampling efficiency. Our survey also demonstrated that sampling by transect walk captured less bees in general, especially in stubble, maize, and cereal fields. We found that Apis mellifera and Bombus spp. were well represented in samples collected by the transect walk method, while the abundance of other genera, especially Dasypoda, Hylaeus and Panurgus was higher in pan traps. Based on the results, we suggest (i) the transect walk method to compare samples of flower-visiting wild bee communities from various habitats of different vegetation and flower characteristics, (ii) application of the transect walk or pan traps to compare similar habitats and (iii) adoption of a comprehensive method which would incorporate both sampling techniques to gain a more complex insight into wild bee species composition.

Bird-Habitat Relationships in Restored Meadows in Southeastern Pennsylvania

Understanding the relationships of bird abundance to vegetation and the surrounding landscape would help to guide meadow restoration for wildlife habitat. I examined the relationship between bird abundance and vegetation structure and the composition of the surrounding landscape in southeastern Pennsylvania in 2011 and 2012 by using regression models. The relationship between abundance and habitat characteristics varied among species. Common yellowthroats and red-winged blackbirds were more abundant in meadows with tall, dense grasses, while eastern meadowlarks were more abundant in shorter, sparser meadows. Field sparrow abundance was positively related to the amount of woody vegetation in a meadow. The habitat surrounding a survey point also explained bird abundances, with bobolinks and meadowlarks more common in meadows surrounded by grasslands and common yellowthroats more abundant in meadows surrounded by forest. Restoration of meadows in landscapes containing a high proportion of grassland habitats should target eastern meadowlarks and bobolinks by restoring shorter, sparser vegetation. Meadow restorations in forested areas should target other species such as field sparrows or common yellowthroats. Strategic planning of meadow restoration based on the surrounding landscape composition and species-specific vegetation structure requirements should be used to increase the probability of a successful habitat restoration.

Influence of Woody Vegetation on Grassland Birds Within Reclaimed Surface Mines

Abstract We examined the influence of woody vegetation on reclaimed surface mines on relative abundance of Grasshopper Sparrows (Ammodramus savannarum), Henslow's Sparrows (A. henslowii), Eastern Meadowlarks (Sturnella magna), Savannah Sparrows (Passerculus sandwichensis), Bobolinks (Dolichonyx oryzivorus), and Dickcissels (Spiza americana) as well as nest-site selection and nesting success of Grasshopper and Henslow's sparrows and Eastern Meadowlarks. Grasshopper and Henslow's sparrows were the most abundant grassland species on reclaimed mines. Numbers of Grasshopper, Henslow's, and Savannah sparrows, and Bobolinks were negatively associated with percent cover of woody vegetation within 100 m of survey locations. Only Grasshopper Sparrows responded to woody vegetation at nest-patch scales, as random locations had >2.5 times as much woody cover as nest locations. Daily nest survival (DNS) was negatively associated with amount of woody vegetation within 100 m of Grasshopper (DNS 0.76 ± 0.001 SE) and Hensl...

Influence of woody vegetation on pollinator densities in oilseed Brassica fields in an Australian temperate landscape

Wild pollinators may benefit Brassica oilseed production in temperate Australia, yet it is not known how the density of potential pollinators varies in these landscapes. In this study we assessed whether the density of feral honeybees, hoverflies (probably 2 species) and native bees (multiple species) in temperate Australian Brassica oilseed crops was related to the composition of the landscape. The density of pollinators was measured at multiple points in six different Brassica oilseed paddocks (20–80 ha) at least 1.75 km apart. Landscape composition at multiple scales (radii 100–2000 m) was determined from GIS layers of Brassica paddocks, woody vegetation and non-woody vegetation, and a derived layer expected to reflect the condition of woody vegetation remnants (the ‘Link’ score). Densities of feral honeybees were higher near the edges of Brassica fields than towards the middle. Densities of feral honeybees were strongly positively associated with the summed ‘Link’ score within 300 m and with the amount of woody vegetation. Densities of native bees and hoverflies were not strongly associated with woody vegetation or with woody vegetation with a high ‘Link’ score. Our results suggest that maximising feral honeybee abundance within paddocks in these landscapes may require smaller paddocks than those typically used, interspersed with habitat beneficial to feral honeybees such as woody vegetation in good condition. Wildlebende Bestäuber könnten von der Brassica -Ölsamenproduktion im gemäßigten Australien profitieren, dennoch ist nicht bekannt, wie die Dichte der potenziellen Bestäuber in diesen Landschaften variiert. In dieser Untersuchung schätzten wir ab, ob die Dichte wildlebender Honigbienen, Schwebfliegen (vermutlich 2 Arten) und einheimischer Bienen (zahlreiche Arten) im gemäßigten australischen Brassica -Ölsamenanbau mit der Zusammensetzung der Landschaft in Beziehung stand. Die Dichte der Bestäuber wurde an zahlreichen Punkten in sechs verschiedenen Brassica -Ölsamen-Anbauflächen (20–80 ha) gemessen, die mindestens 1.75 km voneinander entfernt waren. Die Zusammensetzung der Landschaft wurde mithilfe von GIS Überlagerung von Brassica -Anbauflächen, waldähnlicher Vegetation und nicht-waldähnlicher Vegetation auf unterschiedlichen Skalen (100–2000 m) bestimmt sowie durch eine abgeleitete Darstellung, von der wir erwarteten, dass sie den Zustand von Überbleibsel der waldähnlichen Vegetation widerspiegelt (den Link-Wert). Die Dichten der wildlebenden Honigbienen waren nahe der Ränder der Brassica -Felder höher als in den zentralen Bereichen. Die Dichten der wildlebenden Honigbienen war sehr stark positiv mit dem summierten Link-Wert innerhalb von 300 m und dem Anteil der waldähnlichen Vegetation korreliert. Die Dichten der einheimischen Bienen und Schwebfliegen waren nicht sehr stark mit der waldähnlichen Vegetation oder der waldähnlichen Vegetation mit einem hohen Link-Wert verbunden. Unsere Ergebnisse lassen vermuten, dass, um die Abundanz der wildlebenden Honigbienen zu maximieren, kleinere Anbauflächen als die typischerweise verwendeten notwendig sind, in die Habitate eingestreut sind, die sich fördernd auf die wildlebenden Honigbienen auswirken, wie waldähnliche Vegetation in einem guten Zustand.

Secondary Invasions: Implications of Riparian Restoration for In‐Stream Invasion by an Aquatic Grass

Abstract The complex nature of ecosystems with multiple invaders requires whole‐system approaches to ecosystem management. Undesirable, unintended secondary effects may occur if interspecific interactions are ignored. Although degraded riparian zones urgently need effective restoration, broad‐scale removal of introduced tree species (e.g., willows [Salix spp.]) and fencing of riparian zones to exclude livestock may facilitate spread of the invasive aquatic grass Glyceria maxima in southeastern Australia. We recorded occurrence of the grass at riparian sites with different amounts of woody vegetation, including willows, and monitored spread for 2 years in locations with and without livestock. Glyceria maxima occurred more frequently at sites with little or no woody riparian vegetation. Larger, older patches fenced from livestock spread fastest. Analyses of costs of controlling G. maxima with herbicide showed that it is more cost‐effective to eradicate small patches than large patches if locations are known. However, the cost per m2 reduction in patch size is cheaper for larger patches. We recommend that small, young patches should be eradicated as soon as detected and show that spread of large source patches can be controlled effectively with continued spraying over several years. If restoration of waterways is to succeed, riparian management strategies must recognize connectivity between riparian and freshwater habitats.

Woody vegetation expansion in a desert grassland: Prehistoric human impact?

Woody plant encroachment into grasslands and savannas is a global phenomenon with undisputed environmental and economic consequences. In central Arizona, the location of our study, it is well known that mesquite, juniper, and cacti account for the majority of the woody plant expansion into arid grasslands. Using aerial photographs (1940 and 2001), we quantified an increase in woody vegetation in this area. We estimated that from 1940 to 2001, the amount of woody vegetation at our study site increased from 559.7 ha (6.1% of the area) to 1326.6 ha (14.4%); an increase of 766.9 ha (8.3%). A GIS model which included two soil types (Rock Land and Springerville (fine montmorillonitic, thermic typic chromusterts)) with an elevation range from 1142 to 1183 m and slopes from 0° to 6° is able to account for 30.3% (234 ha) of the increase in woody vegetation at our study site between 1940 to 2001. We also examined the locations of woody vegetation in relation to archaeological sites (pueblos with over 40 rooms) and determined that human activities roughly 600 year ago continue to impact the distribution of woody plants on the modern day landscape.

Converging patterns of uptake and hydraulic redistribution of soil water in contrasting woody vegetation types.

We used concurrent measurements of soil water content and soil water potential (Psi(soil)) to assess the effects of Psi(soil) on uptake and hydraulic redistribution (HR) of soil water by roots during seasonal drought cycles at six sites characterized by differences in the types and amounts of woody vegetation and in climate. The six sites included a semi-arid old-growth ponderosa pine (Pinus ponderosa Dougl. ex P. Laws & C. Laws) forest, a moist old-growth Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forest, a 24-year-old Douglas-fir forest and three Brazilian savanna sites differing in tree density. At all of the sites, HR was confined largely to the upper 60 cm of soil. There was a common threshold relationship between the relative magnitude of HR and Psi(soil) among the six study sites. Below a threshold Psi(soil) of about -0.4 MPa, overnight recharge of soil water storage increased sharply, and reached a maximum value of 80-90% over a range of Psi(soil) from ~ -1.2 to -1.5 MPa. Although amounts of water hydraulically redistributed to the upper 60 cm of soil were relatively small (0 to 0.4 mm day(-1)), they greatly reduced the rates of seasonal decline in Psi(soil). The effectiveness of HR in delaying soil drying diminished with increasing sapwood area per ground area. The relationship between soil water utilization and Psi(soil) in the 20-60-cm layer was nearly identical for all six sites. Soil water utilization varied with a surrogate measure of rhizosphere conductance in a similar manner at all six sites. The similarities in relationships between Psi(soil) and HR, soil water utilization and relative rhizosphere conductance among the six sites, suggests that, despite probable differences in maximum rooting depth and density, there was a convergence in biophysical controls on soil water utilization and redistribution in the upper soil layers where the density of finer roots is greatest.

Methods of studying the distribution, diversity and abundance of birds in East Africa—some quantitative approaches

In this paper we compare the use of transect counts with a simpler method of investigating bird diversity and numbers, particularly in terrestrial habitats, both natural and non‐natural. Transect Counts (TCs) have long been widely used, whereas Timed Species Counts (TSCs), which estimate relative abundance, are comparatively untried. We find that TSCs give results which are comparable to those from TCs in most respects, except that they can only be used indirectly for estimating population densities, and they give different measures of diversity. However, TSCs generate data on many more species much faster than do TCs and are therefore more cost‐effective in most situations. In particular, TSCs are useful for community studies. We show, for example, that in natural habitats bird populations are positively correlated with the amount of woody vegetation, but not with rainfall. Diversity too increases with woody vegetation. Because TSCs are simple, more of them can be made for a given input of time, and hence more distributional data are obtained as an additional benefit.

Estimating canopy cover in drylands with Landsat MSS data

The relationship between canopy cover and spectral characteristics of the corresponding areas was studied in a semi-arid savannah environment in Kordofan, The Sudan. The canopy cover was measured in 32 test plots through air photo interpretation. Achieved values were correlated with multitemporal Landsat MSS raw data and manipulated data. The highest correlation coefficients in general were obtained between crown cover and spectral data recorded during the dry season. The inverse relationship between amount of woody vegetation and nIR reflectance (MSS 6, MSS 7) was striking. This implied that other factors than a healthy foliage characterized the spectral responses. Destructive measurements of woody biomass were carried out to establish a relationship between woody wet weight and crown diameter for future biomass studies.

Habitat Distribution of Peromyscus leucopus within Prairie Woods

Studies of small mammals in western portions of Kansas and Nebraska have shown the white-footed mouse (Peromyscus leucopus) to be an inhabitant of riparian as well as planted woods (Jones, 1964; Fleharty and Stadel, 1968; Kaufman and Fleharty, 1974). However, little effort has been devoted to analysis of its occurrence in speciFic habitats within these wooded areas. We report here the habitat distribution of P. Ieucopus within a riparian woods and a planted shelterbelt in northcentral Kansas. The RIPARIAN site was the woodland associated with a meandering creek located in a pasture 1 mile E, 21/2 miles S Lucas, Piussell CCounty, Kansas. A 12 X 18 grid (20 m intervals) was placed in the pasture, but only traps occurring within the riparian woods were included in the fo,lowing analysis. The SHELTERBELT site consisted of a half-mile planted shelterbelt bordered by a pasture and a cultivated field 2 miles S, 1 mile W Lucas, Russell County, Kansas. Traps were placed at 18-20 m intervals along two lines 20 m apart which ran the length of the grove. We placed one Sherman live-trap (5.3 X 6.6 X 17.1 cm) at each of 110 RIPARIAN and 96 SHELTERBELT stations. Traps were checked each morning for five days in August 1976 and all Peromyscus removed. Stations were assigned to one of three habitats at each site; habitats were defined according to relative amounts of woody vegetation, canopy and understory. RIPARIAN. Woods/sparse (36 stations). All stations were within 10 meters of the creek and under a canopy formed by elms (Ulmus americana and U. pumila), green ash (Fraxinus pennsylvanica), bur oak (Quercus macrocarpa), cottonwood (Populus sargentii) and willows (Salix sp.). Herbaceous understory was sparse with ground cover less than 50% at most stations. Common forbs included ragweed (Ambrosia psilostachya), sunflower (Helianthus annuus), curly cup gumweed (Grindelia squarrosa), snow-on-the-mountain (Euphorbia marginata) and fireweed (Kochia scoparia). Woodsidense (45 stations) Stations were under or within 10 meters of canopy formed by the same tree species as above. The understory was dense with more than 50% ground cover at all stations and nearly complete cover at many stations. The common forbs were sunflower, curly cup gumweed, snow-on-themountain, ironweed (Vernonia interior) and woolly verbena (Verbena stricta). Hemlock (29 stations). Poison hemlock (Conium maculatum),

Distribution and Dispersal of the Cardinal, Richmondena cardinalis, in Relation to Vegetational Cover and River Systems

Cardinals, Richmondena cardinalis, were studied at four locations of different population density to determine if their presence was correlated with certain environmental features. Distributional data were based on responses to tape-recorded cardinal song, and relationships were analyzed using linear regression techniques. An increase in woody cover, regardless of foliage type, was associated with an increase in cardinal numbers in all regions, but cardinals occupied even very sparse cover in Tennessee. A strong association with river systems noted in peripheral populations was not displayed by cardinals in the center of their range, and largely coniferous vegetation close to these rivers in any region did not appear to deter them. The edge of the cardinal's range in Ontario shows good agreement with snowfall distribution peculiar to the region. It is suggested that most dispersal is effected by young cardinals using rivers as guidelines and thus settling close to them through inertia, and not because they offer the best available habitat. The cardinal's northward spread is likely limited by winter snow cover and concomitant food shortage rather than by unsuitable vegetation. INTRODUCTION The cardinal, Richmondena cardinalis, is characteristic of the avifauna of the Carolinian Zone or Deciduous Forest Biome, and provides perhaps the classic example in North America of the rapid range expansion possible among indigenous birds. The euryoecious distribution of a dense Tennessee population suggests that foliage type and even amount of vegetational cover may be of little importance to cardinals, and need only provide adequate nest-sites (Dow, 1969a,b). Observations of cardinals living in cypress cedar swamps, spruce and pine plantations, or other coniferous situations in various parts of their range, suggest that even relatively homogeneous tracts of boreal forest vegetation might be insufficient to limit their northward expansion. The cardinal first bred in southern Ontario in 1901 (Snyder, 1957), and from that time its history has been well documented. Snyder (1957) and De Vos (1964) have speculated on factors responsible for the rapid spread of the species in Ontario. The present paper examines some factors possibly limiting its distribution, particularly foliage types and amounts of woody vegetation, river systems, and snowfall. METHODS Between 1965 and 1967 I studied populations of cardinals at four locations, one of high density near the town of Dresden in western 1 Present address: Department of Zoology, University of Queensland, St. Lucia, Brisbane, Australia.