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Slope, aspect, and slope position as factors controlling grassland communities in the coulees of the Oldman River, Alberta
Abstract
Vegetation and environmental variables were examined in some coulees of the Oldman River near Lethbridge, Alta. Principal components analysis of environmental variables indicated that solar energy, aspect, soil Mg2+, , and moisture were related to the first axis of variation. Slope position, soil , moisture, K+, , and amount of bare ground were related to a second axis of variation. There was a large range in species diversity among plots; most diverse plots were on north-facing slopes. Direct ordination of vegetation data indicated that slope position and aspect were most important in describing distribution of species. Koeleria macrantha, Bouteloua gracilis, Stipa comata, and Artemisia frigida were found on most coulee positions. Hymenoxys richardsonii, Machaeranthera grindeloides, Astragalus spatulatus, and Eriogonum flavum were mostly restricted to summit and upper slope positions. Anemone patens, Geum triflorum, Thermopsis rhombifolia, and others were most abundant on north- and east-facing slopes. Fewer species (e.g., the C4Aristida longiseta and the cactus Coryphantha vivipara) were mostly confined to south-facing positions.
... Topography has a well-known and widely studied influence upon the distribution of plant communities (Perring 1959;Tisdale & Bramble-Brodahl 1983;Lieffers & Larkin-Lieffers 1987;Gong et al. 2008;Rodhouse et al. 2014). Within grasslands, topographical variation can create differences in plant communities and associations that are related to elevation, slope and aspect (Perring 1959;Tisdale & Bramble-Brodahl 1983;Lieffers & Larkin-Lieffers 1987;Bennie et al. 2006;Gong et al. 2008). ...
... Topography has a well-known and widely studied influence upon the distribution of plant communities (Perring 1959;Tisdale & Bramble-Brodahl 1983;Lieffers & Larkin-Lieffers 1987;Gong et al. 2008;Rodhouse et al. 2014). Within grasslands, topographical variation can create differences in plant communities and associations that are related to elevation, slope and aspect (Perring 1959;Tisdale & Bramble-Brodahl 1983;Lieffers & Larkin-Lieffers 1987;Bennie et al. 2006;Gong et al. 2008). Where grasslands occur within steep canyons and mountains, such as the coulees of Alberta (Canada), Northern Galilee Mountains (Israel), Basque Country (Spain), Patagonian grasslands (Argentina) and British chalk grasslands (United Kingdom) there is particular interest in how topography interacts with disturbances to influence long-term vegetation change (Lieffers & Larkin-Lieffers 1987;Defosse et al. 1997;Carmel & Kadmon 1999;Amezaga et al. 2004;Bennie et al. 2006). ...
... Within grasslands, topographical variation can create differences in plant communities and associations that are related to elevation, slope and aspect (Perring 1959;Tisdale & Bramble-Brodahl 1983;Lieffers & Larkin-Lieffers 1987;Bennie et al. 2006;Gong et al. 2008). Where grasslands occur within steep canyons and mountains, such as the coulees of Alberta (Canada), Northern Galilee Mountains (Israel), Basque Country (Spain), Patagonian grasslands (Argentina) and British chalk grasslands (United Kingdom) there is particular interest in how topography interacts with disturbances to influence long-term vegetation change (Lieffers & Larkin-Lieffers 1987;Defosse et al. 1997;Carmel & Kadmon 1999;Amezaga et al. 2004;Bennie et al. 2006). The relationships between disturbance and topography can also be related to edaphic factors (Defosse et al. 1997;Amezaga et al. 2004;Wellstein et al. 2007; Gong et al. 2008), changes in nutrient deposition (Amezaga et al. 2004;Wellstein et al. 2007;Gong et al. 2008) and livestock distribution and use of the landscape (Defosse et al. 1997;Carmel & Kadmon 1999;Amezaga et al. 2004). ...
Question
Some of the last remaining grassland communities of the Pacific Northwest Bunchgrass Region (PNWBR) in North America are found in canyon grasslands, primarily because the rugged topography has left many of these associations untouched by agricultural development. However, there have been no prior examinations into how canyon grassland communities change over the long term or how topography relates to these changes. In this study, we examined how successional stages changed over a 33‐yr time period and which topographical variables were most related to these long‐term outcomes (elevation, aspect or slope). We predicted that areas with more gentle slopes (<20%) would have changed the most because they have seen a higher concentration of historical land uses (e.g. livestock grazing, wildlife herbivory, and cultivation).
Location
Canyon grasslands of Hells Canyon National Recreation Area, northwest USA.
Methods
We looked at how the canyon grasslands have changed over the long term by repeating a vegetation survey of plant species cover and frequency that was completed in 1981 and comparing the results after a 33‐yr time period.
Results
We found that 58% of our plots stayed in the same seral stage or transitioned into later ones. As predicted, the plots that remained in early seral condition or transitioned from later to early seral stages were found on more shallow slopes. In addition, drier aspects within all plant associations appeared to be less resistant and resilient to change, particularly invasion by exotic species.
Conclusions
The results of this resurvey suggest that topographic patterns may not only be related to the distribution of plant associations across the canyon grasslands, but may also influence which sites change most over time. Our findings are consistent with other studies of the relationships between topography and land uses through time in other grasslands, and are highly relevant to conservation management where unique vegetation communities develop within heterogeneous topographic areas.
... A number of studies have examined the effect of slope aspect on various vegetation properties (Mendez-Toribio et al. 2016;Sharma et al. 2010;Singh 2018;Yang et al. 2020) and edaphic factors (Elnaker and Zaleski 2021;Geroy et al. 2011;Kutiel and Lavee 1999;Lieffers and Lieffers 1987;Varga and Csiszer 2020;Xue et al. 2018) but most of these studies are confined to forest vegetation in arid and semi-arid regions. Studies that examine the effect of slope aspect on vegetation attributes and soil characteristics in grassland communities of the Kumaun Himalaya are still lacking. ...
... The SA receives more sunlight and has a remarkably low moisture content than NA, and these conditions are not conducive to plant growth which lowers the biomass in SA. The differences in the incoming solar radiation influence the consequent effects of slope aspect on temperature and moisture and are considered the prime source of vegetation growth and development (Lieffers and Larkin-Lieffers 1987). However, biomass allocation which is simply the ratio of belowground biomass to aboveground biomass was higher for the SA. ...
A floristic and structural survey of a natural temperate grassland community was conducted in the Nainital district of Kumaun Himalaya, India, to examine the effect of slope aspect as one of the topographical factors on the vegetation composition and soil characteristics. Structural data was collected by sampling the vegetation from three slope aspects viz. North aspect (NA), East aspect (EA) and South aspect (SA). Three permanent plots of 20 m × 20 m were established at each aspect and within each of these plots 10 quadrats of 1 m × 1 m were placed randomly, and various ecological parameters were determined. Soil samples were collected from 2 depths i.e. 0–15 cm (surface layer) and 15–30 cm (subsurface layer) and soil characteristics were determined. A total of 22 species were recorded out of which NA had 16 species belonging to 8 families, EA had 14 species belonging to 9 families and SA had 7 species belonging to 5 families. Density, total basal area, diversity, evenness, and biomass showed significant effects of slope aspect. Significant positive relationships between ecological parameters (density, total basal area, diversity, species richness, and biomass) with soil characteristics (moisture, temperature and water holding capacity) suggested strong influence of edaphic variables on ecological parameters. NA contained more moisture, had a higher water holding capacity and lower soil temperature as compared to SA which encourages the herbaceous vegetation and facilitates the growth of species.
... Grasslands are distributed globally across various topographies. In non-flat grasslands, aspect (i.e. the compass direction that a slope faces), characterised primarily by differences in radiation and consequent effects on temperature and soil moisture, becomes an important driver of plant growth and soil properties (Gong et al., 2008;Horvath et al., 1984;Lieffers & Larkin-Lieffers, 1987). While this is an obvious feature of hilly and mountainous areas, aspect is often an important feature of more modest topographies (Bennie et al., 2008) such as those described as plateau (Liu et al., 2006), steppe (Gong et al., 2008) and prairie (Lieffers & Larkin-Lieffers, 1987). ...
... In non-flat grasslands, aspect (i.e. the compass direction that a slope faces), characterised primarily by differences in radiation and consequent effects on temperature and soil moisture, becomes an important driver of plant growth and soil properties (Gong et al., 2008;Horvath et al., 1984;Lieffers & Larkin-Lieffers, 1987). While this is an obvious feature of hilly and mountainous areas, aspect is often an important feature of more modest topographies (Bennie et al., 2008) such as those described as plateau (Liu et al., 2006), steppe (Gong et al., 2008) and prairie (Lieffers & Larkin-Lieffers, 1987). ...
Grasslands are distributed globally across various topographies. In non-flat grasslands, aspect (the direction that a slope faces) influences the amounts of radiation and consequent effects on temperature and soil moisture, all of which are important drivers of plant growth. Aspect is important not only in hill and mountain areas but also in more moderate topographies such as plateaux, steppes and prairies. Here, we tested the aboveground growth response to an important driver of climate change – elevated carbon dioxide (eCO2) – of two temperate grass species grown under simulated north (unshaded) and south (shaded) aspects. We used trellis-like structures to create the appropriate radiation regimes; irrigation ensured that only radiation and hence soil temperatures were different. We utilised the long-running New Zealand Free-Air Carbon Dioxide Enrichment (FACE) experiment and established turves of Lolium perenne L. and Agrostis capillaris L. The aboveground dry matter (DM) was regularly harvested over 10 months. For the main effects, there was no overall response to CO2 but Agrostis produced about 50% more DM than Lolium while the north aspect produced about 15% more DM than the south. There was an interaction between CO2 level and aspect: for both species production was about 20% greater under eCO2 on the north aspect but had no effect on the south aspect. Given that a large proportion of the world’s grasslands is on slopes, this aspect × CO2 interaction causes us to reconsider the up-scaling of CO2 responses from FACE experiments that have been universally carried out on flat terrain.
... On rangelands, topography and grazing create landscape-scale differences (i.e., landform elements) in exposure to solar radiation (Buffo et al. 1972), soil water (Ellis 1938;Ayyad and Dix 1964;Lieffers and Larkin-Lieffers 1987) and plant community structure and function (Pantel et al. 2010). Defoliation by grazing alters GHG flux patterns directly through feces and urine input (Schnabel et al. 2001) and indirectly by removing aboveground biomass and trampling (LeCain et al. 2000), which in turn affects soil microbial environment such as soil temperature (Ruz-Jerez et al. 1994), and soil water (Thurow 1991) and therefore GHG flux (Liebig et al. 2010). ...
... Upland was dominated by H. curtiseta and Elymus lanceolatus which are typical for the Mixed Grassland Ecoregion (see Acton et al. 1998), and depressions was dominated by Poa pratensis and Polygonum amphibium. These are likely due to differences in microenvironments, including soil water, soil temperature, and soil N (Ayyad and Dix 1964;Lieffers and Larkin-Lieffers 1987). Even though mowing and landform did not affect species richness and Shannon-Wiener Diversity Index (H 0 ), south-facing convex had a consistently greater H 0 than north-facing concave. ...
Much of the remaining native rangelands in Canada are topographically complex. The flux of greenhouse gases (GHGs) in rangelands of hummocky terrain has not been adequately studied, leaving a gap in the national GHG sources and sinks budget. The objectives of this study were to determine the effects of topography and mowing on carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) flux and to correlate these fluxes to abiotic and biotic factors. GHG flux was studied on six landform elements, including north-facing concave and, south-facing concave and convex, upland and depressions, in the Northern Mixedgrass Prairie of Canada over 2 years with mowing being imposed in early spring. GHG fluxes showed strong temporal variations, ranging from 3.0 to 40.4 kg CO2–C ha−1 d−1, 0.1 to 2.6 g N2O–N ha−1 d−1, and −0.25 to −0.01 g CH4–C ha−1 d−1. GHG fluxes responded to changes in soil water and soil temperature across the landscape. The largest production of CO2 was recorded in depression mainly due to its more favourable soil water conditions. Mowing enhanced CO2 flux more than CH4 and N2O fluxes. Dominant plant species varied among the six landform elements, but using plant community type as the direct indicator for GHG emissions in grasslands may not always be reliable when precipitation is low. The net emissions of GHGs from Saskatchewan rangeland was relatively low, but the potential to increase emissions through changes in land management could be high. Our results suggest that in the Mixedgrass Prairie, best management practices for maintaining grassland health such as moderate grazing may also reduce GHG emissions.
... In mountainous areas, topography influences soil moisture availability, resulting in higher soil moisture on the downslope than on the upslope [61,133,134]. The topographic impact on soil moisture comes as a result of slope position and slope shape, which causes water discharge from upslope and accumulation on downslopes [133][134][135]. However, soil depth and texture, which affect soil water retention capacity in the downslope, have a substantial impact on soil moisture availability [106,134,136,137]. ...
Mountainous rangelands provide key ecosystem goods and services, particularly for human benefit. In spite of these benefits, mountain grasslands are undergoing extensive land-cover change as a result of woody plant encroachment. However, the influence of topographic and soil factors on woody plant encroachment is complex and has not yet been studied comprehensively. The aim of this review was to establish current knowledge on the influence of topographic and soil factors on woody plant encroachment in mountainous rangelands. To find relevant literature for our study on the impact of topographic and soil factors on woody plant encroachment in mountain rangelands, we conducted a thorough search on ScienceDirect and Google Scholar using various search terms. Initially, we found 27,745 papers. We narrowed down the search to include only 66 papers published in English that directly addressed the research area. The effect of slope aspect and slope position on woody plant encroachment is complex and dynamic, with no universal consensus on their impact. Some studies found higher woody plant encroachment on the cooler slopes, while others found increased woody plant encroachment on the warmer slopes. Slope gradient has a significant impact on woody plant encroachment, with steeper slopes tending to have more woody plant encroachment than gentle slopes. Soil texture and depth are important soil factors affecting woody plant encroachment. Coarse-textured soils promote the growth of woody plants, while fine-textured soils limit it. The effect of soil depth on woody plant encroachment remain unclear and requires further research. Soil moisture availability, soil nutrient content and soil microbial community are influenced by topography, which in turn affect the woody plant growth and distribution. In conclusion, the spread of woody plants in mountainous rangelands is a complex and dynamic process influenced by a range of factors. Further research is needed to fully understand the mechanisms behind these interactions and to develop effective strategies for managing woody plant encroachment in mountainous rangelands.
... In addition, the increase in height allows the formation of cold-resistant species and the distribution of vegetation. (Barrio, et al. 1997; Barnes et al., 1982;Host and Pregitzer, 1992;Tagil 2006;Lieffers and Larkin-Lieffers 1987;Allen and Peet 1990). ...
Within the zoning boundaries, as in other plan legends, green areas are a parameter value. The cadastral
bottom of green areas can belong to a real or legal person. Especially in a zoning plan, the green areas
belonging to the municipalities were determined and the formation of points that could serve the citizens
as a buffet in certain plot-based places were examined. As a methodology, it is stated how the kiosks
should be processed in the parcels and how the allocation documents should be based on the land
registry. In this study, it has been tried to show how the square meter areas, which are technically less
than the total number of the zoning plans, should be created and processed in the light of which
parameters and their application to the land on site.
... In addition, the increase in height allows the formation of cold-resistant species and the distribution of vegetation. (Barrio, et al. 1997; Barnes et al., 1982;Host and Pregitzer, 1992;Tagil 2006;Lieffers and Larkin-Lieffers 1987;Allen and Peet 1990). ...
The parcels formed in the zoned areas, regardless of the status of the parcels, cadastral or zoning, that
is, regardless of the pole size, are registered in the land registry as a basis. In this way, the title deed of
the land is formed. However, having the title deed does not mean that the relevant parcel will have the
necessary permission for the construction permit for the parcel dimensions. For this reason, it is tried to
provide minimum front and depth ratios in parcels where such parcel dimensions are not provided. The
parcel size is tried to be solved by zoning practices called segregation or merging, in some places as a
shared parcel and in some places as a single parcel. The study is based on island images in 1/1000
application plans. Here, it has been tried to show how the dimensioning can be achieved with geometric
approaches in the parcels whose dimensions cannot be provided, with various parcel examples, and it is
tried to be explained that the situation where a construction permit can be obtained with a self-sufficient
size.
... where B is angle of incidence of beam solar; D is solar declination; L is latitude; S is slope; A is surface azimuth (0 is due south, east is positive, west is negative); and H is hour (Lieffers, 1987). In southern Mexico, Méndez-Toribio et al (2016) studied the effect of slope aspect and topographic position on soil properties. ...
Pomace, olive solid waste, obtained after olive oil production and should not be applied directly to the soil due to having environmental problems. Composting is one of the methods used for the recovery of agricultural wastes for many years, and many studies have been conducted out on vermicomposting recently. In this study, organic matter, ash, C/N ratio and total Zn contents of composted and vermicomposted materials obtained from the mixture of pomace with farmyard manure at different ratios were compared. Pomace was mixed with farmyard manure on a dry weight basis of 0%, 25%, 50% and 75% rates. These mixtures were composted and
vermicomposted using Eisenia fetida worm species for eight weeks. The organic C contents varied between 43.43% and 50.66% in compost and 22.70% and 35.36% in vermicompost. The total N values varied between 1.32% and 1.73% in the compost material and between 1.49% and 1.95% in
the vermicompost. While the C/N ratios of compost materials varied between 27.67 and 38.51, C/N ratios of vermicompost materials varied between 11.92 and 23.81. While composting and vermicomposting processes slowed down with increasing the rate of pomace added into manure, the organic matter contents increased, and the ash contents decreased in the composted and the
vermicomposted materials. Therefore, the total Zn contents of the materials decreased from 345.56 mg/kg to 117.33 mg/kg in the vermicomposting process and from 317.5 mg/kg to 186.59 mg/kg in the composting process due to decreasing ash contents. While the highest total Zn content was obtained in vermicompost obtained with farmyard manure, the lowest total Zn content was obtained in the mixture ratio of 75% pomace:25% farmyard manure. The total Zn contents of vermicomposted materials with pomace were found to be lower compared to the composted materials with pomace.
... where B is angle of incidence of beam solar; D is solar declination; L is latitude; S is slope; A is surface azimuth (0 is due south, east is positive, west is negative); and H is hour (Lieffers, 1987). In southern Mexico, Méndez-Toribio et al (2016) studied the effect of slope aspect and topographic position on soil properties. ...
Soil is seen as a natural body whose characteristics are defined by the materials
from which it was created and the environment in which it has been exposed.
Soils are formed through the interaction of five major factors, topography is well
known as one of these factors, it has a great impact on microclimatic and
meteorological characteristics, which affect soil hydrology and temperature
regimes. Soil temperature and moisture play a decisive role in plant
communities. Soil temperature depends on the amount of radiation from the
sun which reaches the soil surface (insolation). The radiation amount is directly
proportional to the soil temperature. yet the general statement can be made
that, insolation has more importance than air temperature. The temperature
of the soil is influenced by a number of factors, including meteorological
conditions (air temperature and insolation), topography (slope aspect and
gradient), and soil water content. Soil moisture is an important component of
the earth system, it affects atmospheric, geomorphic, hydrologic, and biologic
processes. Soil moisture is also an essential variable in regional and
microclimatic assessments, landscape denudation, runoff generation,
partitioning, mass wasting, and sediment movement due to its dispersive and
cohesive properties. The slope aspect is one of the quantitative topographic
characteristic factors responsible for the redistribution of water in the
landscape, it also has an effect on the pattern and trend of vegetation in
mountainous regions. In the northern hemisphere, north-facing slopes receive
less direct sunlight (insolation) than south-facing slopes. Sloping lands towards
the equator receive a greater amount of solar energy over a longer period of
time. Thus, the soil temperature is usually higher on south-facing slopes than on
north-facing slopes, and as the temperature of the soil increases the water
content decrease so the soil on the north-facing slopes was generally moister
than the soil on the south-facing slopes.
... shifts have occurred at north-facing plots, which is consistent with the idea of encroachment by woody species on sites with relatively high soil moisture. Greater soil moisture has previously been shown to aid in tree seedling establishment and growth (Gatherum et al. 1963), and in Alberta, soils on north-facing slopes tend to have higher levels of soil moisture (Lieffers and Larkin-Lieffers 1987). This would enable tree species to expand more easily on north-facing slopes, driving plot-level composition away from more open communities seen in the original surveys. ...
Plant communities are changing in response to natural and anthropogenic drivers. However, we know little about how different drivers have affected Rocky Mountain plant communities over the past few decades. In 2017, a wildfire burned 50% of the vegetation at Waterton Lakes National Park, located in Canada’s southern Rocky Mountains. Using re-surveys of vegetation plots established in the 1990s, I quantified changes in plant community diversity and composition over the past two decades. I found that fire severity interacted with human disturbance to affect species richness and community composition. I also found that burned and unburned plots are experiencing diverging trajectories. Herbaceous and short-lived species have become more prominent in burned plots, whereas unburned plots are becoming increasingly characterized by woody species. Ecologists should continue conducting legacy studies as they have the potential to expand our theoretical understanding of community assembly and inform management decisions.
... Eğimi, bakısı, yükseltisi ve pürüzlülüğü gibi birçok özelliği ile bir yamaç, bir yerdeki hayvan ve bitki varlığı üzerinde etkilere sahiptir (Lieffers ve Larkin-Lieffers 1987). Bu etki, jeomorfometrenin değişik mikro iklimlerin ortaya çıkmasında belirleyici olmasının bir sonucudur. ...
... In forested landscapes with dissected topography, such aspect/moisture gradients are correlated with understory species composition (Allen & Peet 1990;Hix & Pearcy 1997) and diversity (Glenn-Lewin 1975;Huebner & Randolf 1995;Pausas & Carreras 1995). Indices of soil moisture based on combinations of site variables have also been correlated with variations in site productivity (McNab 1993;Fralish 1994) and overall plant species composition (Lieffers & Larkin-Lieffers 1987;Allen & Peet 1990;Lloyd et al. 1994). In addition to their putative effect on species composition, such topographically-generated soil moisture and radiant energy gradients have been related to other ecosystem attributes and processes, including soil morphology and development (Finney et al. 1962;Pregitzer et al. 1983), nutrient cycling rates (Plymale et al. 1987;Morris & Boerner 1998), leaf litter decomposition rates (Boerner 1984a, Mudrick et al. 1994), mycorrhizal infection intensity (DeMars & Boerner 1995), soil enzyme activity (Decker et al., in press) and foliar nutrient dynamics (Boerner 1984b;Kost & Boerner 1985;Garten 1993). ...
... For example, when we look for the ideal place of a vineyard or a orchard, we search areas, which aspect is south or south-east and the slope is also an ideal value, not too steep but neither too plain. The slope and aspect are also very important in the ecological research like [1], [2], [3], [4], [5]. ...
The slope and the aspect are an important property of the terrain in the agriculture related geospatial analysis. The distribution of this values in a determined area can be demonstrated by different tools. This paper describes a diagram and its generating method, that can show the slope and aspect in a geomtrically correct layout, which use a polar coordinate system.
... A more likely explanation of underlying causes points to differences in slope and aspect e FE on N-facing slopes, and BB on flat to S-facing slopes e as the primary drivers of the main plant community patterns. Slope gradient and aspect are known to exert strong controls on plant community development at temperate latitudes in semi-arid climates (Lieffers and Larkin-Lieffers, 1987;Letts et al., 2010). This occurs through the variation of incident solar radiation and its effects on soil water content, soil temperature and evapotranspiration (Letts et al., 2010). ...
... The production potential of plants varies among aspects and topographic positions in the Northern Mixed Prairie because plant community composition, the microenvironment, and resource availability differ with slope aspect and landforms (Ayyad and Dix 1964;Redmann 1975;Lieffers and Larkin-Lieffers 1987). That plants also respond differently to grazing in different topographic positions (Archer and Tieszen 1986;Milchunas et al. 1989) may be related to plant community composition, resource availability, and the microenvironment. ...
Pantel, A., Romo, J. T. and Bai, Y. 2011. Above-ground net primary production of plains rough fescue [Festuca hallii (Vasey) Piper] after a single defoliation on five landform elements. Can. J. Plant Sci. 91: 689-696. Above-ground net primary production (ANPP) was determined for plains rough fescue [Festuca hallii (Vasey) Piper] following a single defoliation to 7.5 cm stubble height on five landform elements in the Northern Mixed Prairie. The landform elements included north aspect-concave slopes, north aspect-convex slopes, south aspect-concave slopes, south aspect-convex slopes, and level uplands. Above-ground net primary production was determined for 2 yr after defoliating plants in May through November. Above-ground net primary production after defoliation was not dependent on landform elements in the first (P=0.23) and second years (P=0.22) after defoliation. In the first year after June through September defoliation, ANPP was reduced 29 to 41% (P<0.01), whereas May, October, or November defoliation had no significant effect on ANPP. Above-ground net primary production did not vary significantly (P=0.61) among months of defoliation in the second year after defoliation. Less ANPP in the first year after June through September defoliation indicates the need for >= 1 yr of deferred use to allow plants to regain their production potential. Unaffected ANPP after May, October, or November defoliation suggests plains rough fescue can be grazed annually. Recuperation of ANPP after defoliation depends on the month of the year in which plains rough fescue is defoliated, but not on landform elements in the Northern Mixed Prairie.
... Potential solar radiation, topographic position, and exposure strongly influence soil moisture regimes through water infiltration, runoff and evapotranspiration (Loucks, 1962; Whittaker, 1967; Jenny, 1980; Lieffers & Larkin-Lieffers, 1987 ). These components were used to construct a composite topographic moisture index (range 1-7) using the following expression: ...
Vegetation samples collected near Taos, New Mexico, Wet Mountain Valley, Colorado, and Rocky Mountain National Park, Colorado, were used to analyse latitudinal variation. Dominant compositional gradients at the 3 localities were related to elevation, site moisture status, and potential solar radiation. Average elevation of floristically similar stands declined with increasing latitude between Taos and Wet Mountain Valley (-46.5 m per degree latitude), and between Wet Mountain Valley and Rocky Mountain National Park (-106.6 m per degree latitude). Elevation shifts between localities varied with the reference stand's position along the elevation and moisture gradients. Smaller elevation shifts between localities were found for widespread species. Species were, in general, most widely distributed along the elevation gradient at Rocky Mountain National Park and along the moisture gradient at Taos. High-elevation Picea engelmannii/Abies lasiocarpa forests were comparatively similar in the 3 regions, although the number of recognizable communities per region increased with latitude. There was considerable latitudinal change in the composition of low-elevation forests. Although species richness is generally considered to decline with increasing latitude, highest species richness was found at Wet Mountain Valley. Relative species richness patterns along the elevation and moisture gradients were similar for all three localities. -from Authors
... While much is known about the effect of incline in terrestrial systems (e.g. Bazzaz, 1975;Lieffers and Larkin-Lieffers, 1987), little is known about the effect of substratum incline on community structure and functioning on natural rocky shores despite rocky shores being very variable in their topography. Of the few studies that have been carried out, the majority have investigated incline on emergent rock and not in Table 3 PERMANOVA test results for effects of location (Penmon and Porth Dinllaen), tidal height (low and mid), pool depth (shallow (<10 cm), medium (10e20 cm), deep (>20 cm)) and substratum incline (horizontal, sloping, vertical) on community composition. ...
... In short-statured ecosystems, complex terrain results in spatially variable incident solar radiation (K;), so that soil moisture, near-surface T a , and atmospheric demand vary not only seasonally, but also with slope aspect (Zou et al. 2007; Bennie et al. 2008 ). In grasslands , microclimatic differences produce complex vegetation patterns, but certain grasses and shrubs are found on both north-and south-facing slopes (Lieffers and Larkin-Lieffers 1987). Opposing hillslopes can, thus, be used as treatments, to examine the physiological acclimation of individual species to a wide range of abiotic conditions in a given year. ...
... Numerous studies have indicated that the spatial variation of soil properties is significantly influenced by environmental factors such as parent materials, topographic positions, topographic-aspect-induced variations in microclimate and vegetation communities (c.f. Chen et al., 1997;Fu et al., 2004;Hanna et al., 1982;Johnson et al., 2000;Lieffers and Larkin-Lieffers, 1986;McKenzie and Ryan, 1999;Ollinger et al., 2002;Sharma et al., 1998;Venterea et al., 2003). Yimer et al. (2006) evaluated some soil property variations in relation to topographic aspects and vegetation communities in the south-eastern highlands of Ethiopia and showed that soil properties exhibited significant differences according to their associated vegetation communities and topographic aspects. ...
Topography has an important influence on the distribution of soils and their properties, especially in hilly lands, and related data are easily available, measurable and recognizable from digital elevation models (DEMs). To our knowledge, little attention has previously been paid to the effect of DEM attributes on the distribution of soils, using ordination methods. The objective of this study was to analyze relationships between topographical properties derived from DEM and soil distribution and to discuss their applicability in Digital Soil Mapping (DSM). The study was carried out in the Borujen area of central Zagros, Iran. A total of 13 plots (each one of 6.75ha) were set up to calculate the percentages of the dominant soil series. Fifteen DEM attributes, including slope, aspect, curvature, maximum and minimum curvature, planform curvature, profile curvature, tangent curvature, wetness index, power index, sediment index, area solar radiation, direct radiation, diffuse radiation and direct duration were also computed. Canonical Correspondence Analysis (CCA) was used to summarize the data set and to evaluate the expected relationships. The results obtained show that there was a relatively strong correspondence between soils' series distribution and topographical properties. The DEM attributes that best related to the first axis were maximum curvature, slope and sediment index, all of which significantly positive correlated, and wetness index, direct duration and minimum curvature, all of which were negatively related. The second axis showed a negative trend with wetness index, direct duration and aspect, and a positive trend with sediment index and slope. These gradients were closely related to the first three canonical axes and explained 71.8% of the total variance of the soil series. The residual variance (28.2% of the total variance) was related to other soil forming factors, like parent material and vegetation cover, which were not investigated in this study. Considering that DEMs are still the most important source of environmental information, understanding the role of topographical factors in a region should help us to identify soils and their properties better and enable us to apply these derivates as input data in DSM.
... In short-statured ecosystems, complex terrain results in spatially variable incident solar radiation (K;), so that soil moisture, near-surface T a , and atmospheric demand vary not only seasonally, but also with slope aspect (Zou et al. 2007; Bennie et al. 2008 ). In grasslands , microclimatic differences produce complex vegetation patterns, but certain grasses and shrubs are found on both north-and south-facing slopes (Lieffers and Larkin-Lieffers 1987). Opposing hillslopes can, thus, be used as treatments, to examine the physiological acclimation of individual species to a wide range of abiotic conditions in a given year. ...
Plant functional groups with contrasting growth strategies co-occur in semiarid ecosystems. In the northern Great Plains, woody shrubs and grasses interact competitively, with shrubs prevalent on mesic hillslopes. To understand topographic influences on physiological drought acclimation, we measured seasonal photosynthetic water use in C3 shrubs (Artemisia cana Pursh and Rhus trilobata Nutt.) and grasses (Agropyron cristatum (L.) Gaertn. and Stipa viridula Trin.) on north- and south-facing slopes. Relationships between abiotic controls and photosynthesis were similar on both aspects, indicating an absence of long-term photosynthetic acclimation to xeric, south-facing conditions. Acclimatory differences were observed between functional groups. Soil moisture depletion lowered intercellular:atmospheric CO2 ratio (Ci/Ca) and increased intrinsic water-use efficiency (WUEi = Amax/gs) in shrubs, but not grasses. Consequently, between-slope differences in net photosynthesis (Amax) and stomatal conductance (gs) occurred only in shrubs, with lower values on the south-facing slope. Shrubs also exhibited between-slope differences in the photochemical reflectance index, suggesting drought-related photoprotection. The deuterium:hydrogen ratios of stem water showed that deep water use facilitated late summer growth in shrubs. Consistent with plant distribution, cumulative water use and photosynthesis were higher in shrubs than in grasses on the north-facing slope, but higher in grasses than in shrubs on the south-facing slope. This shows that topographic effects on leaf photosynthetic gas exchange are mediated by physiological acclimation strategy and water source use.
... Production potential varies among range sites (Abouguendia 1990), aspects (Ayyad and Dix 1964;Redmann 1975), and topographic position (Klemmendson 1964;Redmann 1975). Similarly, plant community composition, the microenvironment, and resource availability differ with slope degree, slope aspect, and landform element (Ayyad and Dix 1964;Baines 1973;Lieffers and Larkin-Lieffers 1987;Pennock et al. 1987). Variable characteristics among slope aspects, slope degree, and landform elements may influence the rate at which plants recover their production following grazing. ...
Resting plants after grazing is central to sustaining potential plant production. Growth of graminoids and forbs was determined for 3 yr after a single defoliation to 7.5 cm in May, June, July, August, September, October, November, or April on five different landform elements in the Northern Mixed Prairie.
Green standing crop and cumulative green standing crop of forbs, graminoids, and their total varied with months of defoliation, landform elements, and years after defoliation. Green standing crop and cumulative green standing crop of forbs, graminoids, and their total was less than the control (P50.05) on at least one of five landform elements until the second year after defoliation. This pattern of growth suggests the need to defer grazing for at least 1 yr after use to allow plants to regain their production potential. Plants defoliated early in the growing season recovered their production sooner or at the same time as those defoliated later in the growing season or when dormant. Generalizations that spring or early summer defoliation of native range reduces production and late summer or dormant season grazing has no effect on production warrants reconsideration where adequate rest is provided following a short period of grazing.
... Landscapes in the Northern Mixed Prairie are composed of many landform elements with species composition and production potential of plants varying among aspects (Ayyad and Dix 1964; Redmann 1975; Butler and Goetz 1986) and topographic positions (Klemmendson 1964; Redmann 1975). Plant community composition, the microenvironment, and resource availability also differ with slope degree, slope aspect, and landform element (Ayyad and Dix 1964; Baines 1973; Lieffers and Larkin-Lieffers 1987; Pennock et al. 1987; Braun 2005). Variable characteristics in the physical environment among slope aspects, slope degree, and landform elements can influence the rate at which plants recover their production following defoliation. ...
Above-ground net primary production (ANPP) of northern wheatgrass (Elymus lanceolatus [Scribn. & J. G. Sm.] Gould) and western porcupine grass (Hesperostipa curtiseta [Hitchc.] Barkworth) was determined after defoliation to a 7.5 cm stubble height on five landform elements in the Northern Mixed Prairie that had been ungrazed for . 25 yr. Landform elements included north aspect–concave slopes, north aspect–convex slopes, south aspect–concave slopes, south aspect–convex slopes, and level uplands. ANPP was determined for 2 yr after defoliating plots once in May, June, July, August, September, October, November, or April. Northern wheatgrass and western porcupine grass ANPP varied among landform elements (P , 0.01), but not with the month of defoliation 3 landform element interaction (P 0.69), but that of western porcupine grass was reduced by August and September defoliations (P , 0.01). ANPP of both grasses was insensitive to landform element in terms of defoliation responses. Northern wheatgrass ANPP was not responsive to temporal aspects of a single defoliation. With the exception of August and September defoliations, western porcupine grass also was insensitive to a single defoliation in different months. Land managers should consider rest (1 yr nongrazing) following grazing of western porcupine grass in August or September, whereas responses to defoliation in different months suggest northern wheatgrass can be grazed annually.
... The spatial variation of soil properties is significantly influenced by some environmental factors such as topographic aspect induced microclimate differences, topographic [landscape] positions, parent materials, and vegetation communities (Chen et al., 1997; Sharma et al., 1998; McKenzie and Ryan, 1999; Johnson et al., 2000; Ollinger et al., 2002). Studies indicate some variations in soil properties related to topographic positions (Hanna et al., 1982; Lieffers and Larkin- Lieffers, 1986; Chen et al., 1997; King et al., 1999; Venterea et al., 2003; Fu et al., 2004). Milne (1935) ...
Study of soil property variations resulting from topographic aspect and vegetation changes will have implication on the proper management of marginal and environmentally sensitive areas. This study addressed the effects of topographic aspect and vegetation community types on soil physical and chemical properties in the Bale Mountains, south-eastern highlands of Ethiopia. At each stratified vegetation community; Schefflera–Hagenia, Hypericum–Erica–Schefflera, and Erica arborea (shrub size), and in each of the four topographic aspects, four representative soil profiles giving a total of 3 × 4 × 4 = 48 were opened and described. Soil texture, bulk density, soil pH, plant available phosphorus, CEC, exchangeable base cations, and percent base saturations were analyzed and interpreted. Except in few cases, all considered soil properties showed significant differences among vegetation communities and topographic aspects. The differences may be attributed to leaching and differences in organic matter (carbon) contents within the soil profiles due to topographic aspect-induced microclimatic differences, reflecting the response of vegetation communities to the conditions. Soil textural fractions, mainly silt and clay, bulk density, pH, plant available phosphorus, percent base saturation, CEC, and exchangeable base cations generally increased in the Schefflera–Hagenia vegetation community zone. Further studies might be required to fully understand and clarify the influence of aspect, topography and vegetation types on soil properties for site-specific soil resource management practices in this mountainous area.
... The ubiquitous association between vegetation shifts and microclimate transitions across slope aspects is one of the most extensively described dynamics in plant community ecology (Turesson, 1914;Cottle, 1932;Boyko, 1947;Oosting & Billings, 1951;Cantlon, 1953;Pook & Moore, 1966;Smith, 1977;Hicks & Frank, 1984;Lieffers & Larkin-Lieffers, 1987;Bale & Charley, 1994;Olivero & Hix, 1998;Sternberg & Shoshany, 2001;Holst et al., 2005;Boerner, 2006;Chmura, 2008;Albrecht & McCarthy, 2009). Equatorial slopes (south-facing in the northern hemisphere) receive far more solar irradiation than nonequatorial slopes, and this creates striking gradients in irradiation, temperature and moisture availability (Radcliffe & Lefever, 1981;Parker, 1991;Galicia et al., 1999;Geiger et al., 2003;Searcy et al., 2003). ...
*The ubiquitous transition of plant communities across slope aspects is a well-described, but rarely tested, ecological dynamic. Aspect position is often used as a proxy for microclimate changes in moisture, light and temperature, but these abiotic drivers are seldom decoupled and very rarely manipulated across slope aspects. *To investigate the mechanisms and demographic stages driving the observed distribution patterns of two woodland herbs in the southeastern USA, seeds and adults were transplanted across north- and south-facing slopes, and moisture and light were experimentally manipulated. *Stage- and species-specific abiotic responses resulted in similar landscape-level patterning for Hexastylis arifolia and Hepatica nobilis, but the underlying abiotic drivers were unique. Adult rather than seed survival best explained the natural distributions across slope aspects, and Hexastylis arifolia was limited by higher temperature, whereas Hepatica nobilis was limited by lower soil moisture. *The stage- and species-specific responses indicated that the use of slope aspect to explain plant distributions not only obfuscates explanatory mechanisms, but probably undermines the portability of results. As abiotic drivers, not topographical proxies, are projected to shift with global climate change, distribution research requires direct abiotic data in association with key demographic stages rather than topographical proxies.
The aim of the present study was to investigatethe relationship between the spatial distribution of termitaria and topographic features in part ofthe Kruger National Park. The location of the study area corresponds to the Lowveld, which isdrained by the Letaba and Olifants rivers. This part of the Kruger National Park was chosen asthe study area because it has the largest termite population. The main objective of the study wasto investigate the relationship between topographic features and termites to determine howtermites in the study area affect both the savanna ecosystem and the structure and function of thetermite biome. The material of the study consists of data from 8200 different training pointsobtained from high resolution satellite imagery. Topographic features are explained using thedataset obtained from processed DEM (Digital Elevation Model) data with a spatial resolution of12.5 m. Thematic maps of the study were prepared using ArcGIS/ArcMap 10.8 software.Descriptive, clustering and comparative statistical methods were used in the study. Statisticalanalyzes were conducted using IBM SPSS Statistics 22 software. The results suggest that certaintopographic features are more effective than others for termite distribution. Accordingly, thequantitative results of the different topographic features were revealed. Moreover, the factorsaffecting the spatial distribution of termitaria were ranked from most important to leastimportant: degree of ruggedness, relative soil moisture, slope shape, aspect, slope and elevation.In the study area, termites were found densely distributed in moist and less fissured sections,where shallow slope form predominated on south-facing plateau areas with an average elevationof 394 m (2-5%). Given the relationship between termites and land cover, evaluation of theirmutual interactions provided new results for governments and scientists to further investigate thenatural cycle in protected areas such as the Kruger National Park.
Keywords: Termites, Remote Sensing, Kruger National Park, GIS, South Africa.
We investigated the effects of pipeline construction and environmental factors on the occurrence and characteristics of the endangered plant Halimolobos virgata (Nutt.) O.E. Schultz. The plants were surveyed from 2007 to 2016 at three sites along the Keystone Pipeline in southern Alberta, Canada. Plant height, number of flowers and siliques, as well as microhabitat and climate data were collected up to 300 m away from the pipeline. Pipeline construction and distance had no effect on plant numbers or physical characteristics, with occurrences increasing markedly over time. Greater litter cover and depth and spring precipitation were associated with plant height and number of flowers and siliques. Vegetation cover was negatively correlated with H. virgata cover; however, plant height and number of flowers and seed pods were positively influenced by graminoid cover. The highest occurrences of H. virgata coincided with the driest and wettest years, and higher winter and spring temperatures. Some of this pattern can be attributed to the plant’s annual, biennial, and short perennial life forms, which may overlap and create a temporary exponential growth rate for an annual plant under ideal conditions. This research highlights the importance of understanding a species’ life history for the development of effective conservation and recovery strategies.
A study was carried out on a wild herb Hypericum sinaicum (Family: Hypericaceae) in Saint Katherine Protectorate, South Sinai, Egypt to increase the understanding about some applications of Geographical Information Systems (GIS) in analysis, management and making suitable decisions in plant conservation strategies. Also to detect the effect of environmental factors (Topography) on the distribution of Hypericum sinaicum as well as geographical attributes. The results showed that it was found that H. sinaicum has a narrow range of distribution between 1515 and 2036 m. It was shown that the highest presence for H. sinaicum was in elevation between 1800-2000m (42.7%) and the lowest presence detected was at elevation between 1400-1600m (0.8%). Extracted data came from 3d analysis by GIS found that H. sinaicum communities strongly affected by aspect and this shiny appears in the species distribution within special aspects. H. sinaicum was recorded at North East (44%), North (15.5%), East (15.5%), North West (13.8%), West (7.7%), South (1.7%), South East (0.8%) and Flat (0.8%), there was no records for the plant at the South West aspect. The slope degree of the populated sites was very high, as the species was found in slope aspect between 89.98 and 90 degree. Results showed that topography (elevation, aspect and slope) influences on physical and chemical properties of soil, plant morphology and plant community structure.
We examined the influence of topography, canopy structure and gap light environmental variables on the patterns of vascular ground flora (vascular plants less than 1 m in height excluding tree seedlings) in a subtropical broadleaved forest in S China, using field data obtained from a 4-ha permanent plot. Both topographic and canopy environmental conditions had a significant effect on community composition, species diversity and distribution of the vascular ground flora. However, topographic factors, especially slope position and aspect, had a greater influence as compared with canopy and understory light conditions. Both number of individuals and number of individuals per species of the ground flora varied significantly with different slope position, aspect, slope steepness and transmitted direct radiation, while species richness varied significantly under different slope position and canopy leaf area index (LAI) The effects of topographic and canopy environmental conditions on ground-flora composition and structure was further confirmed by Canonical Correspondence Analysis (CCA). Multi-response Permutation Procedures (MRPP) showed significant differences in the ground-flora species composition based on all the topographic, canopy structure and gap light variables. Species indicative of topographic, canopy structure and gap light regimes were identified with a significant indicator value (IV >= 35%) by Indicator Species Analysis (ISA), which indicated that certain species have their ecological preference for a particular environmental gradient.
The objectives of the study are to determine the role of geomorphometric factors as abiotic environmental factors in the organization of landcover across the landscape in Kazdağ National Park. The hypothesis is that geomorphometric factors play an important role in community distribution in the landscape. Methodological importance of this study is that Geographical Information Systems (GIS) play an important role to identify physical features of habitats. Elevation, slope, aspect, topographical humanity index, curvature, temperature, and precipitation factors were used to link landcover to environmental variables. GIS techniques were used to create maps for environmental variables and to analyze them. The analysis of correlation between landcover types and landform characteristics was performed using Zonal Statistics. Thus the geomorphometric factors had to be transferred into nominal data; therefore classes were used instead of raw values. Analyses show relationship between landcover, also vegetation distribution, and environmental factors due to the relief
The effect of different grid sizes of digital elevation models (DEMs) on the relationship between soil properties and terrain attributes was examined by comparing six DEMs (4, 6, 8, 10, 20 and 30m). The study site was representative of a broad region of hilly landscapes in the southwestern China. The results showed that elevation, topographic wetness index (TWI), slope and natural logarithm of specific catchment area (SCA) varied with DEM grid size in a relatively clear direction except aspect and plan curvature. Different soil–landscape relationships were found across various DEM resolutions. The observations from this study indicate that the most accurate predict model is not always produced by the highest resolution DEM. The knowledge of which DEM resolution produces an appropriate model for a particular landscape can be used as a guideline for optimizing field sample strategies.
In order to assess the impact of policies to encourage extensification in less favoured areas and improve our knowledge of extensive livestock systems, we analyzed relationships between the diversity of grassland vegetation and land use management practices and field characteristics. This study, conducted on a mountainous area in the centre of France, was based on 149 fields, mainly of natural grasslands belonging to 7 farmers. Regression analyses were performed to analyze the relations between the grassland vegetation types (five types established from the list of dominant species), management practices (cutting versus grazing and fertilization) and the topographic (altitude and aspect) and topologic (slope, distance and surface area) characteristics of the fields. The land use management rules used by the farmers were studied by specifying the grazing management rules of the herd (dairy cows), as well as those for conserved forage (mainly hay or silage) and were identified from observations mentioned on the “grazing schedules”, as well as from interviews at the beginning, in the middle and at the end of the study period. The statistical analysis showed that neither the topographic characteristics of the fields nor the distance from the cowshed or surface area were correlated with the grassland vegetation types. It was the management practices used, largely determined by the field slope, which determined the grassland vegetation type. On the other hand, farmers’ statements showed that the grazing and cutting management rules were mostly determined by the slope of the fields and the distance from the cowshed and, to a lesser extent, by the altitude and aspect. These results showed that the farmers take into consideration environmental differences when choosing fields to allocate for grazing and cutting at different seasons, particularly when they are constrained by these features. Nevertheless, when the constraints were minimal, a wide diversity of grassland vegetation types was also observed. This diversity was a result of attributing different functions to the fields which led to different management practices (defoliation methods and fertilization) and, thus, to different grassland vegetation types. Consequently, for farms where animal feed requirements vary according to the time of the year and the type of animal, we suggest that diversity in the grassland vegetation types is a sound component of these livestock systems.
Interrelationships between dominant compositional and environmental gradients were studied using 186 forest stands sampled on the east slope of the Sangre de Cristo Range, Colorado. Detrended correspondence analysis and detrended canonical correspondence analysis were used to analyze indirect and direct gradients, respectively. The dominant compositional gradient was strongly correlated with elevation. Increasing elevation was associated with decreasing soil pH and percent base saturation, and increasing total soil N. Ordination of stands stratified by elevation showed the major compositional gradient within each elevation class was strongly correlated with a topographic moisture index. Most soil variables correlated with this gradient in low and high elevation classes. In mid-elevation forests, a third compositional gradient correlated with soil pH, percent base saturation, and potential solar radiation. In these forests, Pinus contorta and Pseudotsuga menziesii were associated with acidic soils on north-facing slopes, whereas Populus tremuloides and Abies concolor were associated with base-rich soils on south-facing slopes. Ordination axes accounted for least variation in comparatively young mid-elevation forests. A plausible explanation is that the mid-elevation forests represent an unpredictable stage in forest development where competition has not yet had sufficient time to sort species along environmental gradients.
Moisture and nutrient gradients consistently explain much of the variation in plant species composition and abundance, but these gradients are not spatially explicit and only reveal species responses to resource levels. This study links these abstract gradients to quantitative, spatial models of hill-slope assembly. A gradient analysis in the mixed-wood boreal forest demonstrates that patterns of upland vegetation distribution are correlated to soil moisture and nutrient gradients. Variation in species abundance with time since the last fire is removed from the gradient analysis in order to avoid confounding the physical environment gradients. The physical-environment gradients are related to qualitative positions on the hill slope i.e. crest, mid-slope, bottom-slope. However, hill-slope shape can be quantitatively described and compared by fitting allometric equations to the slope profiles. Using these equations, we show that hill-slope profiles on similar surficial materials have similar parameters, despite coming from widely separated locations. We then quantitatively link the moisture and nutrient gradients to the equations. Moisture and nutrients significantly increase as distance down-slope from the ridgeline increases. Corresponding vegetation composition changes too. These relationships characterize the general pattern of vegetation change down most hill slopes in the area. Since hill slopes are a universal feature of all landscapes, these principles may characterize landscape scale spatial patterns of vegetation in many environments.
Abstract: The study was conducted at four sites in the unglaciated Allegheny Plateau region of southeastern Ohio, each was comprised of an unburned treatment unit, a periodic burn unit (prescribed fires in 1996 & 1999) and an annual burn unit (prescribed fires 1996-1999). The study sites were stratified by an integrated soil moisture index (IMI). Prior to fire treatments (1995), variation in understory species composition was most strongly correlated with topographic variations in predicted soil moisture (IMI), N mineralization rate, nitrification rate, and soil pH. Species richness was positively correlated with N mineralization rate and nitrification rate. Understory vegetation responded similarly on both the periodic and annual burn treatments, among the four study sites, and across the three IMI classes (xeric, intermediate, mesic). Post-burn compositional shifts resulted primarily from shade-intolerant species and summergreen herbs that increased in frequency from seed bank germination and also from tree seedlings that decreased in frequency. Species richness and evenness became significantly greater on burned plots as forb and graminoid richness increased. Prescribed fires also had moderate effects on tree seedling populations. Frequencies of several shade-tolerant species were significantly lower on burned sites. The frequencies of oaks (Quercus) and hickories (Carya) were not affected significantly. In 2002, there was no significant difference in the abundance of shade-tolerant seedlings among the fire treatments. Oak+hickory seedling abundance was highly variable with a small subset burned xeric plots supporting high densities (>1500/ha) of large seedlings. The rare woodland grass Calamagrostis porteri subsp. insperata was also monitored on burned and unburned sites. On annual burn patches, tiller density increased significantly relative to unburned and periodically burned patches, and annual burn patches also exhibited a sharp increase in flowering. Overall, this study indicates that in closed-canopy oak forests even repeated fires may not substantially improve the competitive status of oak seedlings. However, repeated fires can increase the richness and evenness of native plant species without facilitating the invasion of exotic species. This study suggests that continued fire exclusion could negatively affect the long-term maintenance of plant diversity in these forests. Title from first page of PDF file. Document formatted into pages; contains xix, 203 p. : ill. Thesis (Ph. D.)--Ohio State University, 2004. Includes bibliographical references (p. 183-203). Advisor: Ralph E.J. Boerner, Dept. of Evolution, Ecology and Organismal Biology.
The surface pattern of short wave radiation can be estimated from the observations of a single, representative site provided it is possible to distinguish between direct and sky-diffuse radiation totals. The patterns of direct radiation over an area can then be mapped from the observations normally taken on a horizontal surface, and a knowledge of (1) extra terrestrial radiation, (2) the latitude, and (3) the surface geometry of the given area. Sky-diffuse radiation can be mapped by reference to the observations normally taken and the angles of slope over the area. Application of these methods to Barbados with the aid of a computer mapping program shows how varied the seasonal patterns of short-wave radiation income can in fact be in a tropical region of moderately diverse relief, despite the general similarity of recordings on a horizontal surface. The method also brings out the importance of the first three hours of the day to the heating of east facing slopes.
Plant distributions were examined on an N-facing, mixed-grass prairie hillside near Fort Collins, Colorado. Three plants communities were recognised along the hillside. An Agropyron smithii-dominated community was found at the hilltop, while a Poa-Hordeum-dominated community was located at the base of the slope. Midslope areas supported a Bouteloua- Agropyron- dominated community. Each topographic location had different soil moisture regimes and textures. Grasses with the C4 photosynthetic pathway had highest importance values on well-drained sites where soil moisture was lowest and soils coarsest. C3 graminoids predominated on the relatively moist upper and lower portions of the hillside.
(1) The distribution of species of cacti along gradients of aspect and angle of slope is described and compared for a species-rich community in the Sonoran Desert and for a species-poor community in the Mohave Desert. (2) No differences were found between the two sites in the ecological ranges of cactus species along these gradients. (3) In the Sonoran Desert there were larger overlaps in the distribution of species along the aspect-gradient than in the Mohave Desert; however, no differences in overlap were found between the two areas along the gradient of angle of slope. (4) More species of cacti are packed into the Sonoran Desert study area, either by utilizing portions of the environmental gradients unavailable in the Mohave Desert, or by addition of species with different growth-form and maximum size. (5) The cylindropuntias (the group with the largest number of species in the two areas) illustrate the latter effect.
A Mixed Prairie in the Northern Great Plains (South Dakota, USA) was studied to determine the floristic composition, according to C"3 and C"4 types, of the seasonal contribution to aboveground production. Twenty-seven of the 305 species present in the Ordway Prairia possessed Kranz anatomy and are assumed to be C"4. Thirty-six percent (19) of the grasses were C"4 whereas <2% (4) of dicots were C"4. Dicots were often weedy and fugitive or introduced species. C"3 plants possessed a mean @?^1^3C value of -26.7%, C"4 plants a value of -12.9%. The biomass of lowland and upland communities possessed low @?^1^3C values in spring. These values increased significantly in the upland community in midsummer to -20.0% indicating a shift to C"4 activity. In fall the biomass @?^1^3C values were again low in both communities indicating a return to C"3 activity. These data show a clear seasonal displacement in production activity of C"3 and C"4 grasses in the Mixed Prairie. A general discussion of the evolution and significance of photosynthetic pathways is included.
A relationship between importance values of several tree species and aspect was found in a north-central West Virginia catchment. Corresponding differences in soil chemical properties with aspect were also observed. North and east aspects had larger amounts of manganese and potassium in the A horizon than did south and west slopes. The converse was true for iron and hydrogen ion (acidity). It is proposed that greater quantities of certain elements in the topsoil on north and east aspects relates to more complete litter decomposition and more rapid nutrient cycling on these sites.
Soil-landscape relationships were studied at a site comprised of Dark Brown and related soils of the Weyburn Association in central Saskatchewan. A slope-profiling approach, involving division of slopes according to angular differences between measured lengths along the transects, revealed that while soil distribution varied in terms of slope position, slope length, slope gradient and sequence, the most significant relationship lies between soil distribution and shape of slopes. Slope divisions generally coincided with observable soil divisions, corresponding, respectively, with shallow, deep and gleyed soils. A combination of aerial photos, field examination of soils and an evaluation of slopes and particularly slope changes could be used to recognize and map these broad, landscape-related soil groupings. -Authors Soil association Soil catena Soil series Slope analysis Topography Map units.
The effect of landscape position and slope aspect on soil water recharge under dryland farming was studied in southeast Nebraska. North, south, and east-facing slopes of Wymore silty clay loam (fine, montmorillonitic, mesic Aquic Argiudoll) were selected. Four positions were identified on each slope, namely, summit, shoulder, backslope, and footslope. Water content of the soil from 0 to 150 cm depth in 30 cm increments were measured weekly by neutron probe for 2 years. Daily precipitation was recorded. Soils of the north-facing slope were 10 % less efficient in recharge of available water than soils on south- and east-facing slopes during all recharge periods. Soils on footslopes were 6 to 8 % more efficient than other positions throughout the year. Water storage efficiency of the soil appeared to be higher in fall than in spring. Available water recharge was 9 % more efficient during the fall than during the winter-spring period in all soils regardless of slope aspects and positions. High correlation coefficients (r) existed when soil available water was related to rainfall in either fall or spring recharge period.
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Study of the distinctive pattern of alignment and geographical distribution of more than 250 coulees in the plains of southern Alberta shows that (1) the coulees in question have a mean orientation of N. 70° E., and (2) their spatial distribution is not ubiquitous but rather displays a concentration in the area from Lethbridge west to the Rocky Mountain front. Several possible hypotheses of origin of the aligned coulees are considered, including subsurface structural control, the role of regional slope, the effect of lithologic differences, and wind action. Action of postglacial wind, operating to initiate surface furrows (by wind-driven snow or rain) that were enlarged by running water, accounts for the three outstanding characteristics of the aligned coulees: (1) their preferred orientation of N. 70° E., which approximates the mean direction of the strongest chinook winds in the southern Alberta plains; (2) their geographical distribution, which coincides with that part of the region experiencing the most pronounced chinooks; and (3) their almost exclusive location on windward topographic surfaces. No other hypothesis of origin is known that can satisfactorily explain all of these observed facts.
The spatial distribution of roots of two alien grasses, Bromus tectorum and Poa pratensis, grown singly and in a mixture, was examined using a double-labelling radioisotope technique. Interactions between the root systems of these plants led to a restricted B. tectorum rooting volume in P. pratensis neighborhoods greater than or equal to30-d-old. The roots of B. tectorum failed to develop laterally. The altered B. tectorum root systems may contribute to its inability to persist in established P. pratensis swards.
The objectives of the study were to determine the general phytosociological structure of the native prairies, meadows, and marshes of Nelson County, North Dakota; to establish relationships between this structure and factors of the physical environment; and to evaluate the relationships between the vegetation of Nelson County and the True and Mixed prairies. Frequency values and environmental measurements on soil texture, salinity, pH, and an estimate of the drainage regime were obtained in 100 stands selected to represent the vegetational diversity within the County. The drainage regime proved to be the most important single environmental factor in determining the vegetation. A phytosociological drainage regime gradient was then established by assigning indicator values to selected species, and the behaviors of all species and environmental factors were displayed along this gradient. The vegetational display was then divided into six units: the uplands into high prairie, mid prairie, and low prairie and the lowlands into meadow, marsh, and cultivated depressions. Each vegetational unit is described. Comparisons are made between each unit and the related vegetation in surrounding areas. It is concluded that Nelson County should be considered to be within the geographical area of the True Prairie, although the frequent occurrence of western grassland types and western species suggests that the County is within the tension zone between the True and Mixed prairies.
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In this review we relate the physiological significance of C4 photosynthesis to plant performance in nature. We begin with an examination of the physiological consequences of the C4 pathway on photosynthesis, then discuss the ecophysiological performance of C4 plants in contrasting environments. We then compare the performance of C3 and C4 plants when they occur together in similar habitats, and finally discuss the distribution of C4 photosynthesis with respect to the physical environment, phylogeny, and life form.
Incluye bibliografía e ìndice
Ecology of mixed prairie in Canada A reconsideration of grassland classification in the northern great plains of North America The nature of grassland. In Grassland ecosystems of the world: analysis of grasslands and their uses Vegetation patterns within southern Alberta coulees
- R T Coupland
COUPLAND, R. T. 1950. Ecology of mixed prairie in Canada. Ecol. Monogr. 20: 271 -315. 1961. A reconsideration of grassland classification in the northern great plains of North America. J. Ecol. 49: 135-167. 1979. The nature of grassland. In Grassland ecosystems of the world: analysis of grasslands and their uses. Edited by R. T. Can. J. Bot. Downloaded from www.nrcresearchpress.com by University of Otago on 12/29/14 COXSON, D. S., and LOONEY, J. H. H. 1986. Vegetation patterns within southern Alberta coulees. Can. J. Bot. 64: 2464-2475.
Common coulee plants of southern Alberta
- J Kuijt
KUIJT, J. 1972. Common coulee plants of southern Alberta. Univer-sity of Lethbridge Production Services, Lethbridge, Alta.
Smithsonian meteorological tables The vegetation of the Canadian prairie provinces. 11. The grasslands. Part I. Phytocoenologia
- R L List
- Dc Looman
LIST, R. L. 1949. Smithsonian meteorological tables. Smithsonian Institute Press, Washington, DC. LOOMAN, J. 1980. The vegetation of the Canadian prairie provinces. 11. The grasslands. Part I. Phytocoenologia, 8: 153-190.
Manual of soil sampling and methods of analysis. Canadian Society of Soil Scientists The prairie and associated vegetation of south-western Alberta
- J A Mckeague
- E H Moss
MCKEAGUE, J. A. 1978. Manual of soil sampling and methods of analysis. Canadian Society of Soil Scientists, Ottawa, Canada. Moss, E. H. 1944. The prairie and associated vegetation of south-western Alberta. Can. J. Res. Sect. C, 22: 11 -31.
Downloaded from www.nrcresearchpress.com by University of Otago on 12
- Can J Bot
Can. J. Bot. Downloaded from www.nrcresearchpress.com by University of Otago on 12/29/14 For personal use only.