Vegetation Site Relationships Research Articles

Wet meadows of the alliance Molinion and their environmental gradients in Slovenia

The main objective of this study was to examine the relationships between wet meadow plant communities of Molinon alliance and their environmental conditions in Slovenia. The ecology of these communities was analysed in detail. The study provides the data on the vegetation and environmental parameters, the significance of parameters for the plant species composition, most important environmental gradients and differences between plant communities. In all plots the vegetation was recorded and soil parameters were analysed (pH, plant-available P and K, Nt, organic C, C/N ratio, exchangeable Ca2+, Mg2+, K+, Na+, H+, electrical conductivity, base saturation). Other conditions were also considered (e.g., mean annual temperature and precipitation, humidity index, mean Ellenberg moisture and nutrient value) to test possible correlations as well. Vegetation was classified by means of multivariate cluster analysis, while vegetation-site relationships were examined with direct gradient analysis (CCA). Six associations from the Molinon alliance (Selino-Molinietum, Plantagini altissimae-Molinietum, Carici davallianae-Molinietum, Gentiano-Molinietum litoralis, Junco conglomerati-Betonicetum and Sanguisorbo-Festucetum commutatae) were identified and analysed. Soil reaction was identified as most significant environmental parameter explaining the variation of the studied vegetation. There are several statistically significant differences in site conditions between the communities (pH, moisture, nutrient status, Ca2+). The studied associations represent clearly defined ecological units.

Spatial patterns and vegetation–site relationships of the presettlement forests in western New York, USA

AbstractAim The purposes of this study were to develop a Geographic Information System and spatial analytical methodology to reconstruct and represent the presettlement vegetation in a spatially continuous manner over large areas and to investigate vegetation–site relationships before widespread changes of the vegetation had taken place.Location The study area was the Holland Land Company Purchase in western New York, a 14,400 km2 area extending across the physiographic provinces of the Erie–Ontario Lowlands and the Appalachian Uplands.Methods Bearing‐tree records from the Holland Land Company township surveys of western New York in c. 1800 were collected and analysed. The geostatistical method of indicator kriging was used to map spatially continuous representations of individual tree species. Rule‐based and statistically clustered approaches were used to analyse and classify the reconstructed tree species distributions in order to obtain the vegetation association distribution. Contingency table analysis was conducted to quantify species relationships with soil conditions.Results The presettlement vegetation at both the tree species and the vegetation association levels were easier to interpret and visually more effective as a spatially continuous representation than as a discontinuous distribution of symbols. The results for tree species were probability occurrences of species distribution, showing spatial patterns that were not apparent in discrete maps of points or in summary tables of species frequencies. Analysis of the 8792 bearing trees suggested the dominance of American beech (Fagus grandifolia) and sugar maple (Acer saccharum) in the forest composition 200 years ago. Both soil drainage and texture were important site determinants of the vegetation in western New York. The rule‐based and statistically clustered approaches had the advantage of summarizing vegetation compositional patterns in a single image, thus avoiding the need to delineate manually and subjectively the location of boundaries between adjacent vegetation associations.Main conclusions The study offers more insights into the spatial pattern of presettlement forests in western New York than do prior studies. The spatially continuous representation could also enable the comparison of vegetation distribution from data sources that have different sampling schemes, for example the comparison of presettlement vegetation from the presettlement land survey records with current vegetation from modern forest inventories. The results are of value, providing a useful benchmark against which to examine vegetation change and the impacts of human land use.

The effects of three regeneration harvest methods on plant diversity and soil characteristics in the southern Appalachians

We evaluated the effects of three regeneration harvest methods on plant diversity and soil resource availability in mixed-hardwood ecosystems. The study area is in the Wine Spring Creek watershed on the Nantahala National Forest of the Southern Appalachian Mountains in western North Carolina. The regeneration treatments were: an irregular, two-aged shelterwood cut (2A), with 5.0 m 2/ha residual basal area; a shelterwood cut (SW), with 9.0 m 2/ha residual basal area; a group selection cut (GS), with 0.10–0.20 ha openings and 25% overstory removal on area basis at first entry; fourth, the control, consisted of two uncut sites (UC). Each harvest treatment was replicated three times across the landscape in similar plant community types. Within each treatment area, permanent plots were marked and inventoried for overstory, midstory, and herbaceous layer plants. In each permanent plot, we collected soil samples in winter (December–March) to reduce temporal variation due to vegetation phenological stage and rainfall events. We analyzed soil samples for extractable calcium (Ca), magnesium (Mg), potassium (K), cation exchange capacity (CEC), pH, bulk density, A-horizon depth, total carbon (C), and nitrogen (N). Species diversity of overstory, understory, and herbaceous layer species was evaluated using species richness ( S), Shannon–Wiener's index of diversity ( H′), and Pielou's evenness index ( E). We used direct gradient analysis (non-metric multidimensional scaling, NMS) to explore the changes in vegetation–site relationships among herbaceous layer abundance, and soil characteristics and overstory basal area between pre-harvest (1994) and post-harvest (2000). Twelve minor overstory species were cut from the 2A treatments and nine species were cut from the SW treatments. Thus, it is not surprising that S and H′ were reduced in the overstory on the heavily cut sites. However, most of these species sprouted from cut stumps and were substantially more abundant in the midstory layer after harvest than before. For the midstory, we found higher S and H′ on the harvested treatments than the control; however, H′ did not differ significantly among the harvest treatments. We measured an increase in herbaceous layer H′ on the more heavily cut treatments (2A and SW) after harvest. We found an increase in average distance in the NMS ordination among sites in 2000 compared to 1994, which suggests greater herbaceous species diversity after harvest. However, we did not see a clear separation among harvest treatments in the NMS ordination.

Relationships between the vegetation and soil conditions in beech and beech-oak forests of northern Germany

In this study we examine the relationships between the vegetation of beech and beech-oak forest communities (Hordelymo-Fagetum, Galio-Fagetum, Deschampsio-Fagetum, Betulo-Quercetum) and their soil conditions in the lowlands of northern Germany, based on 84 sample plots. In all plots the vegetation was recorded and soil parameters were analysed (thickness of the O- and the A-horizons, pH, S-value, base saturation, C/N, mean Ellenberg moisture indicator value). The vegetation classification according to the traditional Braun-Blanquet approach was compared with the result of a multivariate cluster analysis. Vegetation-site relationships were analysed by means of an indirect gradient analysis (DCA).

Vegetation–site relationships of roadside plant communities in West Virginia, USA

Summary In mountainous regions, road construction is accompanied by large‐scale physical disturbance associated with cut and fill operations that drastically alter the landscape. Cut operations remove soil and rock from the hillside above the proposed road, while soil and rock are deposited on the down‐slope area in fill operations. The resultant roadsides are highly disturbed habitats characterized by plant communities maintained at an early successional stage. They are often planted with non‐native species and frequently provide vectors for the introduction and spread of invasive species. Public transportation managers need to balance the rapid revegetation of roadsides with the goal of maximizing use of native species and minimizing the introduction of non‐native species. This study examined vegetation–site relationships along 13 major four‐lane highways in West Virginia, USA, using analysis of variance, multiresponse permutation procedures and indicator species analysis. Mean soil nutrient values showed some differences with respect to highway, but fewer when highway positions were compared. Similarly, when highway position was considered, there were no significant differences in mean plant species richness, evenness or diversity. Results of multiresponse permutation procedures suggested that different highways may be characterized by distinct vegetation assemblages. This hypothesis was supported by indicator species analysis: 54 species showed a statistically significant (P < 0·05) affinity to one highway over all others. More than half of these were classified as non‐native and exotic invasive species. When highway position was considered, no significant differences in community composition were found, and indicator species analysis found only 25 species that exhibited a significant affinity to one type of position. Of these, only eight were exotic. Of the 33 most abundant herbaceous species, 11 showed a significant relationship between cover and distance from pavement. For all but one, average cover declined in a linear fashion with increasing distance. Synthesis and applications. Despite extensive topographic disturbance associated with highway construction, the resultant vegetative communities do not differ with respect to type of construction or resultant landform. This suggests that highway agencies can manage roadside vegetation using similar, standard techniques. Roadsides are optimal growing sites for exotic invasive species that out‐compete native vegetation. Management goals should therefore include techniques for limiting the establishment of these species, and substitution of non‐native species planted for erosion control with suitable native species.

A Comparison of Moisture Scalars and Water Budget Methods to Assess Vegetation-Site Relationships

Quantification of vegetation-site relationships is often required in biogeographic research. Methods linking species to particular sites typically assess evaporative demand and soil moisture availability at the site, though methods differ in how these factors are assessed. This study compares three approaches—a water-budget approach, and field-based and map-based moisture scalars—in their ability to predict the occurrence of a single species, American beech (Fagus grandifolia), observed in 102, 0.04 ha plots in SE Ohio. Actual evapotranspiration and deficit provided results superior to field-based and map-based scalars. Map-based techniques are potentially limited at fine spatial scales, due to the large discrepancy between observed topographic variables, and those modeled with 7.5-minute elevation grids. The study concludes that a water budget approach is applicable to a wide range of studies exploring vegetation-site linkages. It has advantages of being objective in its computation, and applicable at a wide range of spatial scales. Perhaps most importantly with regard to global change research is the dynamic nature of the method: a site's classification will change concurrently with changes in climate.

Using witness trees to assess forest change in southeastern Ohio

In 1787, the U.S. Congress authorized the sale of the "Ohio Company Purchase", ca. 5000 km2 in Appalachian Ohio. The land was surveyed using a township and range system shortly thereafter. Data on >5600 witness trees were transcribed from the survey records, and witness tree locations were plotted on a digital map. This information was used to evaluate presettlement forest composition and structure and to investigate vegetation-site relationships before widespread alteration of the forests had taken place. Presettlement conditions were compared with present conditions using forest inventory and analysis (FIA) data. Two hundred years ago, the forests of southeastern Ohio were dominated by large individuals of Quercus alba L., Carya Nutt. spp., Quercus velutina Lam., and Fagus grandifolia Ehrh. These four taxa accounted for 74% of all witness trees. Although almost 70% of the region is forested today, the second-growth forest has witnessed a decrease in Quercus and Carya and an increase in Acer saccharum Marsh., Acer rubrum L., and many early successional species in smaller size classes. Despite the significant shift in forest composition and structure, species in general seem to be occupying similar positions in the present-day landscape compared with the presettlement forest; topographic variables most strongly control species occurrence in this landscape.

Long-Term Patterns in Vegetation-Site Relationships in a Southern Appalachian Forest

depth, soil clay content, depth of A-horizon, potential solar radiation, and mean temperature during the growing season. Fifty percent of the variation in the vegetation distribution was explained by the site variables used in the canonical correspondence analysis. Soil organic matter, terrain shape, and elevation were the variables most strongly related to vegetation distribution. Species associated with convex terrain (upper slopes and ridges), such as Pinus rigida, Quercus coccinea, and Quercus velutina, decreased in abundance from the 1970s to the 1990s; species associated with soils having high organic matter content and deep A-horizons, such as Liriodendron tulipifera, Rhododendron maximum, and Tsuga canadensis increased in abundance. Individual species responded differently to site gradients. For example, Acer rubrum, Quercus prinus, Oxydendrum arboreum, and Nyssa sylvatica were located in the center of the ordination space (i.e., their occurrence was not related to any of the site variables), which suggests that these species are habitat generalists.

A permanent plot study of vegetation and vegetation-site factors fifty-three years following disturbance in centralNew England, U.S.A.

Permanent plots, established at the Harvard Forest, Petersham, Massachusetts, U.S.A. in 1940 following the 1938 New England Hurricane, were resampled in order to examine the response of forest understory species to disturbance and to compare responses of overstory trees and understory species. The relationship between species composition and environmental and historical factors was also evaluated. Ordination of plots based on overstory trees and understory species exhibited similar patterns of temporal change following the hurricane. Following complete loss of the canopy, the forest was a mixture of newly colonizing pioneer species (e.g., Prunus pensylvanica, Comptonia peregrina, Fragaria spp., and Hedyotis caerulea), and residual woodland species (e.g., Pinus strobus, Quercus spp., Chimaphila spp., Clintonia borealis, Medeola virginiana and Mitchella repens). Over time, pioneer species declined or disappeared, and woodland species increased. As a result, the modern forest, in terms of both tree and understory species composition, regained some resemblance to the pre-hurricane for-est; however, there was a small group of understory species that did not recover pre-hurricane frequencies (e.g., Cornus canadensis, Mitella diphylla, Polygala paucifolia, Pyrola elliptica, Pyrola rotundifolia, and Tiarella cordifolia). There was evidence that variation in composition and abundance of overstory trees and composition of understory species was related to physical site factors in the pre-hurricane forest and in the older post-hurricane forest (1991), but not in the early regenerating forest. Thus, the hurricane and subsequent salvage operations appeared to relax vegetation-site relationships, but only temporarily.

Vegetation–site relationships of witness trees (1780–1856) in the presettlement forests of eastern West Virginia

Witness tree data from 1780–1856 for the Monongahela National Forest in eastern West Virginia were analyzed with respect to physiographic unit (Ridge and Valley versus Allegheny Mountains) and landform, and compared with present-day forest composition. Contingency table analysis and standardized residuals were used to quantify the preference or avoidance of common tree species with various landforms. Pre-European settlement forests in the Ridge and Valley were dominated by mixed oak (Quercusalba L., Quercusprinus L., Quercusvelutina Lam. and Quercusrubra L.), Pinus spp., Castaneadentata (Marsh.) Borkh., and Carya on ridge sites and Q. alba, Acersaccharum Marsh., Pinus, Tiliaamericana L., and Tsugacanadensis (L.) Carr. on valley floors. The original forests in the Allegheny Mountains were dominated by Fagusgrandifolia Ehrh., T. canadensis, A. saccharum, Acerrubrum L., Betula spp., and Pinus, with predominantly Fagus–Tsuga–Pinus forests on mountain tops and Tsuga–Acer–Betula forests on valley floors. Compared with the presettlement era, present-day forests on both physiographic units lack overstory C. dentata and have decreased Pinus and (or) Q. alba. Species that have increased substantially following Euro-American settlement include Q. prinus, Q. rubra, Quercuscoccinea Muenchh., and A. rubrum in the Ridge and Valley and Prunusserotina Ehrh., A. rubrum, and Betula spp. in the Allegheny Mountains. These dramatic changes in forest composition were attributed to the chestnut blight (caused by Endothiaparasitica (Murrill) P.J. Anderson & H.W. Anderson), widespread logging, intensive wildfires, and more recently, fire exclusion.

Relation of plant species to substrate, landscape position, and aspect in north central Massachusetts

Vegetation–site relationships in the region about the Harvard Forest in north central Massachusetts were explored by means of contingency table and cluster analyses of presence–absence data. Most of the arboreal species, the shrubs, and the ferns were strongly associated with segments of a microclimate – soil moisture gradient determined by landscape position and substrate. Cluster analysis of the species suggested the existence of a fertility gradient, with the more nutrient demanding white ash (Fraxinusamericana L.), sugar maple (Acersaccharum L.) and basswood (Tiliaamericana L.) on one end of the gradient and pitch pine (Pinusrigida Mill.), scrub oak (Quercusilicifolia Wangenh.), and aspen (Populus sp.) on the more impoverished sites. An analysis of the feasibility of determining vegetation–site relationships in an area with a long history of human disturbances concludes the report.

Vegetation-Site Relationships in the Presettlement Forests of Northeastern Ohio

The presettlement forest of northeastern Ohio was dominated by two major forest types. The complex surficial geology and topography of the area created a variety of habitats favoring forests composed of beech and maple on some sites and oak and hickory on others. Binary discriminant analysis was applied to data from the early land survey records of Wayne, Ashland, and Holmes Counties to determine the environmental factors defining the two forest types. Beech (Fagus grandifolia) was largely confined to imperfectly drained soils derived from a relatively fine-textured till. White oak (Quercus alba) occupied the coarser-textured tills and residual soils. A two-dimensional gradient depicting, on one axis, the supply of moisture to the soil-water system by runoff and, on the other axis, the removal of moisture by internal drainage provides a framework for interpreting many of the more important species-environment relationships.

An Integrated Multivariate Analysis of Forest Communities of the Central Great Smoky Mountains

An integrated sequence of multivariate techniques was applied to vegetation and site data from 244 stands in the central Great Smoky Mountains National Park. The analyses included cluster analysis, stepwise multiple discriminant analysis with both species and site variables, reciprocal averaging, canonical analysis and canonical correlation. Taken together, they provided a system of successive refinement and cumulative evidence for analysis of vegetation and vegetation-site relationships. Nineteen forest community types were identified and examined. At the broad level, the vegetation pattern was most directly related to elevation, topography and stand history. However, some soil variables were important, specifically soil/?H and clay content of the ? horizon. The most useful measures of topographic effects were topographic position and total annual potential solar irradiation (a function of slope angle and aspect). Number of dead Castanea dentata remains provided a measure of past disturbance which was related to the vegetation pattern. Introduction The Great Smoky Mountains National Park, located in eastern Tennessee and western North Carolina (approximately 83? 30' W longitude, 35? 45' ? latitude), contains large areas of undisturbed and little-disturbed temperate forests. General descriptions of the physiography, climate, flora, general vegetation and land use history are available elsewhere (Cain, 1930, 1931, 1945; Whittaker, 1956, 1966; King and Stupka, 1950; Hoffman, 1964; Frome, 1966; Golden, 1974). Whittaker's (1956) monograph is the most comprehensive treatment of the general vegetation pattern. He provided a direct gradient analysis which related species populations and subjectively defined community types to elevation and to a qualitative moisture complex-gradient based on topographic characteristics. He did not obtain any data on soils. His scope was the entire national park and involved data from locations scattered throughout it. The study reported here was designed to supplement previous studies. It employs an integration of several multivariate techniques which have recently become widely used. The scope is the middle elevation forests of the central portion of the park. This was defined as forest stands at 750-1600 m elevation in an area ca. 20,000 ha, roughly centered on Mt. LeConte. Field observation indicated that the vegetation pattern of this area varied significantly in certain details from the general pattern reported by Whittaker (1956). For example, the high elevation Quercus alba communities he reported are absent here, and Tsuga canadensis is more prominent than in the remainder of the park. This paper has two primary purposes: (1) to more clearly define the forest vegetation pattern and forest vegetation-site relationships in the central Great Smoky Mountains, and (2) to illustrate the integrated use of a combination of multivariate techniques for defining and describing such vegetation attributes. Methods and Results data Data from 244 forest stands were used in the analyses and descriptions. Each stand was sampled using a 0.08 ha circular plot in which trees > 12.7 cm dbh were tallied by species in 5-cm dbh classes. Sample locations were selected primarily from topographic maps with the objective of obtaining a reasonable distribution among topographic situations in the elevation range 750-1600 m. Species importance percentages for each stand were computed as one-half the sum of relative density and relative basal area. 37 This content downloaded from 157.55.39.162 on Thu, 11 Aug 2016 04:52:52 UTC All use subject to http://about.jstor.org/terms 38 The American Midland Naturalist 106(1) Only tree species present in at least three stands (30 species) were used in the analyses. Taxonomic nomenclature follows Little (1953). Topographic measurements taken included elevation, slope angle, slope direction and slope position (as percent distance from ridge to cove or valley bottom). The potential annual solar irradiation (in langleys) was estimated for each site from the tables of Frank and Lee (1966). Soil profile descriptions and samples were taken from a soil pit near the center of each plot. Soil p?i and texture for each horizon were determined in the laboratory. numerical analyses An integrated sequence of multivariate procedures, involving both classification and ordination, was used to explore the vegetative and environmental relationships among the communities. The sequencing and integration of the procedures are illustrated in Figure 1. Cluster analysis and similarity sorting. ?Minimum within-group dispersion using standard distance (Orloci, 1967), a polythetic agglomerative clustering algorithm, was used to provide a basis for defining stand groups which represent community types. The data were species importance values. A dendrogram was constructed using output

Forest Vegetation of the Lower Alabama Piedmont

Forest community types were distinguished for the lower Alabama Piedmont using a combination of two agglomerative clustering algorithms with a similarity sorting technique. All stands classified in 8 of the resulting 10 community types has within—type similarity values of at least 45%. Ordination by reciprocal averaging using the tree basal areas indicated that community types can be segregated into three topographically defined groups: streambottom communities (Sweetgum—Water Oak—Red Maple and Small Steambottoms), mesic upland communities (White Oak, Chestnut Oak, Pine—Hardwoods, Mixed Oak—Hickory, and Loblolly Pine), and xeric upland communities (Oak—Pine, Blackjack Oak—Pine, and Longleaf Pine). A reciprocal averaging ordination using understory plants successfully separated most of the same community types. The combined clustering—similarity sorting procedure identified "core " stands that provide a clearer representation of definable forest community types than would have resulted from inclusion of atypical or transitional stands. The combination of classification for description of vegetation and ordination for definition of vegetation—site relationships proved complementary and useful. The highest tree species diversities were in mesic upland hardwood and pine—hardwood communities; the lowest were in pine communities. Diameter size class distributions revealed general underrepresentation in the seedling/sapling size classes for all important canopy species, even the climax Quercus and Carya. Underrepresentation was most severe in wet—to—mesic stands. Natural succession from pine toward hardwood dominance is more rapid on bottomlands, stream terraces, and other moist sites than on drier, more fire—prone uplands. Forest cutting practices of many nonindustrial owners accelerate the trend toward dominance of hardwoods, even on uplands.