Scales of heterogeneity in prairie and forest

1999 ◽  
Vol 77 (3) ◽  
pp. 370-376 ◽  
Author(s):  
Heather R Kleb ◽  
Scott D Wilson
Keyword(s):  
Species Composition ◽  
Small Scale ◽  
Light Penetration ◽  
Pocket Gopher ◽  
Available N ◽  
Litter Mass ◽  
Thomomys Talpoides ◽  
Mixed Grass ◽  
Below Ground ◽  
Aspen Forest

Few studies have compared scales of heterogeneity among plant communities. We predicted that differences in the sizes of dominant species should allow us to detect small-scale (<256 cm) heterogeneity in mixed-grass prairie but not in adjacent aspen forest. We examined light penetration, soil moisture, available N, elevation, species composition, and plant mass at 10 locations in prairie and forest in both spring and summer. Variables were measured in 1-cm2 plots arranged in pairs separated by 0-256 cm. Several variables in prairie (elevation, litter mass, light penetration, and species composition) showed significant evidence for scale within the range examined. In contrast, only one variable in forest (light penetration in summer) showed evidence for scale in the same range. The scale of heterogeneity in prairie was consistent with the scale of two possible causes, species composition and elevation variability due to northern pocket gopher (Thomomys talpoides Richardson) activity, both of which varied significantly in prairie but not in forest. Whereas some aboveground factors (light and litter mass) varied within the range examined, belowground factors (water and N) did not, suggesting that the scale of heterogeneity differs between above- and below-ground factors. In total, the results suggest that differences in the scale of heterogeneity between prairie and forest reflect the relative sizes of the dominant plants.Key words: aspen, forest, heterogeneity, light, nitrogen, prairie, scale, soil, water.

Effects of sediment nutrients and depth on small-scale spatial heterogeneity of submersed macrophyte communities in Lake Pleasant, Pennsylvania

2004 ◽  
Vol 61 (8) ◽  
pp. 1493-1502 ◽  
Author(s):  
R K Johnson ◽  
M L Ostrofsky
Keyword(s):  
Organic Matter ◽  
Community Structure ◽  
Spatial Heterogeneity ◽  
Environmental Gradients ◽  
Small Scale ◽  
Sediment Characteristics ◽  
Available Nitrogen ◽  
Total N ◽  
Available N ◽  
Prevailing Paradigm

Sediment concentrations of total and available nitrogen (N), phosphorus (P), and potassium (K) and organic matter from the littoral zone of Lake Pleasant, Pennsylvania, were highly variable. Only organic matter and total N were correlated with depth, however. This result suggests the existence of more complex environmental gradients than the prevailing paradigm of monotonic changes in sediment characteristics with increasing depth. The spatial heterogeneity of submersed aquatic plant communities was significantly correlated with depth, and available N and P. Canonical correspondence analysis demonstrated that these three factors explained 38% of the variance in community structure. Other sediment characteristics (available K, organic matter, and total N, P and K) were not significant by themselves, but all variables combined explained 63% of community-structure variance. Cluster analysis identified species or groups of species typical of endpoints on the depth versus nutrient axes. Myriophyllum exalbescens was typical of deep sites with relatively nutrient-rich sediments, whereas deep nutrient-poor sites were dominated by Vallisneria americana and Megalodonta beckii. Shallow nutrient-rich sites were dominated by several species of Potamogeton and Elodea canadensis, and shallow nutrient-poor sites were dominated by Heteranthera dubia and Najas flexilis. These results demonstrate the importance of sediment characteristics in determining macrophytes' community structure within lakes.

scholarly journals Characteristics of Pocket Gopher Populations in Relation to Selected Environmental Factors in Pelican Valley, Yellowstone National Park

1979 ◽  
Vol 3 ◽  
pp. 133-137
Author(s):  
C. Youmans ◽  
R. Moore
Keyword(s):  
Environmental Factors ◽  
Yellowstone National Park ◽  
National Park ◽  
Ursus Arctos ◽  
Water Levels ◽  
Specific Information ◽  
Pocket Gopher ◽  
Pocket Gophers ◽  
Thomomys Talpoides ◽  
Ursus Arctos Horribilis

Several important environmental factors which affect the dynamics of pocket gopher populations have been identified: water content at peak snowpack and depth of snow in spring (Hansen and Ward, 1966; Reid, 1973); weather and Its influence on annual food supplies and cover (Howard and Childs, 1959); production of annual and perennial forbs (Keith et al., 1959; Tietjen et al., 1967); and ground water levels and snow depths (Ingles, 1949; Hansen, 1962). A need for specific information on pocket gophers in Pelican Valley, Yellowstone National Park arose from interest in interactions between grizzly bears (Ursus arctos horribilis) and northern pocket gophers (Thomomys talpoides). Mealey (1975) and Graham (1978) suggested that pocket gophers and their caches may serve as seasonally important food items for grizzlies in Yellowstone National Park.

Variability in organic matter lost by combustion in a boreal bog during the 2001 Chisholm fire

2003 ◽  
Vol 33 (12) ◽  
pp. 2509-2513 ◽  
Author(s):  
Brian W Benscoter ◽  
R Kelman Wieder
Keyword(s):  
Organic Matter ◽  
Species Composition ◽  
Spatial Variability ◽  
Spatial Variation ◽  
Fire Severity ◽  
Small Scale ◽  
Western Canada ◽  
Direct Combustion ◽  
Site Variation

Fire directly releases carbon (C) to the atmosphere through combustion of biomass. An estimated 1470 ± 59 km2 of peatland burns annually in boreal, western Canada, releasing 4.7 ± 0.6 Tg C to the atmosphere via direct combustion. We quantified within-site variation in organic matter lost via combustion in a bog peatland in association with the 116 000-ha Chisholm, Alberta, fire in 2001. We hypothesized that for peatlands with considerable small-scale microtopography (bogs and treed fens), hummocks will burn less than hollows. We found that hollows exhibit more combustion than hummocks, releasing nearly twice as much C to the atmosphere. Our results suggest that spatial variability in species composition and site hydrology within a landform and across a landscape could contribute to considerable spatial variation in the amounts of C released via combustion during peatland fire, although the magnitude of this variation may be dependent on fire severity.

Nitrogen losses and the utilization of ammonium nitrogen by herbage from spread slurry produced by pigs offered diets formulated to reduce nitrogen excretion

1996 ◽  
Vol 1996 ◽  
pp. 150-150
Author(s):  
T.H. Misselbrook ◽  
B.F. Pain ◽  
R.M. Kay ◽  
P.A. Lee
Keyword(s):  
Crude Protein ◽  
Ammonia Volatilization ◽  
Ammonium Nitrogen ◽  
Nitrogen Excretion ◽  
Nitrogen Losses ◽  
Small Scale ◽  
Pig Slurry ◽  
Crude Protein Content ◽  
Available N ◽  
Reduced Crude Protein

Nitrogen losses following application of pig slurry to grassland represent not only a loss of available N for plant growth, but also a source of air and water pollution by ammonia volatilization, denitrification and nitrate leaching. Previous small scale experiments showed that by reducing the crude protein content of the pigs diet, the slurry nitrogen content was also reduced (Hobbs et al., in press). The aim of this study was to investigate the nitrogen uptake by herbage and losses to the environment following application to grassland of slurry from pigs fed a reduced crude protein diet.

On the Characters of the Pocket Gopher Thomomys talpoides couchi Goldman

The Murrelet ◽  
1939 ◽  
Vol 20 (2) ◽  
pp. 38
Author(s):  
E. Raymond Hall ◽  
Walter W. Dalquest
Keyword(s):  
Pocket Gopher ◽  
Thomomys Talpoides

scholarly journals A Comparison of Abundance and Diversity of Epiphytic Microalgal Assemblages on the Leaves of the SeagrassesPosidonia oceanica(L.) andCymodocea nodosa(Ucria) Asch in Eastern Tunisia

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Lotfi Mabrouk ◽  
Mounir Ben Brahim ◽  
Asma Hamza ◽  
Mabrouka Mahfoudhi ◽  
Med Najmeddine Bradai
Keyword(s):  
Growth Rate ◽  
Species Composition ◽  
Posidonia Oceanica ◽  
Cymodocea Nodosa ◽  
Seagrass Species ◽  
Light Penetration ◽  
Grazing Effect ◽  
Abundance And Diversity ◽  
Fast Growing Species ◽  
Host Characteristics

We studied spatial patterns in assemblages of epiphytic microalgae on the leaves of two seagrass species with different morphologies and longevity,Cymodocea nodosaandPosidonia oceanica, which cooccur in Chebba in Eastern Tunisia. Epiphyte assemblages were described for each species in summer. Epiphyte microalgal assemblages were more abundant on the leaves ofC. nodosabut more diversified on the leaves ofP. oceanica. We suggest that the differences in species composition and abundance between those seagrass species may reflect an interaction of timescales of seagrass longevity with timescales of algal reproductive biology. Short-livedC. nodosawas dominated by fast growing species such as the cyanobacteria speciesOscillatoriasp., whileP. oceanicaleaves were colonized by more mature and diversified species such as Prorocentrales. Local environmental conditions (hydrodynamics, light penetration), host characteristics (meadow type, shapes forms of leaves, life span, and growth rate), and grazing effect seem also to be responsible for these dissimilarities in epiphytic microalgae communities.

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