scholarly journals Interobserver error in grassland vegetation surveys: sources and implications

2020 ◽  
Vol 13 (5) ◽  
pp. 641-648
Author(s):  
Lloyd W Morrison ◽  
Sherry A Leis ◽  
Michael D DeBacker
Keyword(s):  
Species Composition ◽  
Spatial Scale ◽  
Tallgrass Prairie ◽  
Estimation Error ◽  
Observer Error ◽  
Plot Size ◽  
Interobserver Error ◽  
Vegetation Surveys ◽  
Actual Change ◽  
National Preserve

Abstract Aims Observer error is an unavoidable aspect of vegetation surveys involving human observers. We quantified four components of interobserver error associated with long-term monitoring of prairie vegetation: overlooking error, misidentification error, cautious error and estimation error. We also evaluated the association of plot size with pseudoturnover due to observer error, and how documented pseudochanges in species composition and abundance compared with recorded changes in the vegetation over a 4-year interval. Methods This study was conducted at Tallgrass Prairie National Preserve, Kansas. Monitoring sites contained 10 plots; each plot consisted of a series of four nested frames (0.01, 0.1, 1 and 10 m2). The herbaceous species present were recorded in each of the nested frames, and foliar cover was visually estimated within seven cover categories at the 10 m2 spatial scale only. Three hundred total plots (30 sites) were surveyed, and 28 plots selected at random were resurveyed to assess observer error. Four surveyors worked in teams of two. Important Findings At the 10 m2 spatial scale, pseudoturnover resulting from overlooking error averaged 18.6%, compared with 1.4% resulting from misidentification error and 0.6% resulting from cautious error. Pseudoturnover resulting from overlooking error increased as plot size decreased, although relocation error likely played a role. Recorded change in species composition over a 4-year interval (excluding potential misidentification error and cautious error) was 30.7%, which encompassed both pseudoturnover due to overlooking error and actual change. Given a documented overlooking error rate of 18.6%, this suggests the actual change for the 4-year period was only 12.1%. For estimation error, 26.2% of the time a different cover class was recorded. Over the 4-year interval, 46.9% of all records revealed different cover classes, suggesting that 56% of the records of change in cover between the two time periods were due to observer error.

Seasonal Occurrence of Adult Carabid Beetles (Coleoptera: Carabidae) in West-Central Illinois

2020 ◽  
Vol 55 (3) ◽  
pp. 329-343
Author(s):  
Kenneth W. McCravy ◽  
Jason E. Willand
Keyword(s):  
Species Richness ◽  
Species Composition ◽  
Tallgrass Prairie ◽  
Activity Patterns ◽  
Species Abundance ◽  
Abundant Species ◽  
Early Summer ◽  
Carabid Beetles ◽  
West Central ◽  
Central Illinois

Abstract The Carabidae is a diverse family of beetles with many species of interest in conservation and biological control. Carabid beetle adult seasonal activity patterns were studied in a west-central Illinois forest/reconstructed tallgrass prairie matrix over a 2-yr period using pitfall traps. We found a threefold or greater difference in carabid abundance between years. Despite lower abundance, a second year of sampling yielded seven previously undetected species. Abundance and species richness were greatest in May–July and lower in August–October. Relative abundance and species richness were consistent among months between years. Shannon diversity and effective number of species were lowest in June and July. Cyclotrachelus sodalis (LeConte) and Chlaenius platyderus Chaudoir were the two most abundant species, comprising 54.3% of total captures. These species were most abundant in July and June, respectively. Most species showed greatest abundance in spring or early summer, and declined thereafter. Collections of several species were suggestive of bimodal seasonal patterns. Carabid species composition differed significantly among months, but not between years. Our results document seasonal variation in carabid abundance and species composition, and show that sampling throughout the growing season, and multiple sampling years, provide substantial benefits for assessments of carabid diversity in this region.

scholarly journals Plant community diversity and composition provide little resistance to Juniperus encroachment

Botany ◽  
2008 ◽  
Vol 86 (12) ◽  
pp. 1416-1426 ◽  
Author(s):  
Amy C. Ganguli ◽  
David M. Engle ◽  
Paul M. Mayer ◽  
Eric C. Hellgren
Keyword(s):  
Species Richness ◽  
Species Diversity ◽  
Species Composition ◽  
Plant Species ◽  
Plant Community ◽  
Tallgrass Prairie ◽  
Abiotic Factors ◽  
Community Diversity ◽  
Oak Forest ◽  
Old Field

Widespread encroachment of the fire-intolerant species Juniperus virginiana  L. into North American grasslands and savannahs where fire has largely been removed has prompted the need to identify mechanisms driving J. virginiana encroachment. We tested whether encroachment success of J. virginiana is related to plant species diversity and composition across three plant communities. We predicted J. virginiana encroachment success would (i) decrease with increasing diversity, and (ii) J. virginiana encroachment success would be unrelated to species composition. We simulated encroachment by planting J. virginiana seedlings in tallgrass prairie, old-field grassland, and upland oak forest. We used J. virginiana survival and growth as an index of encroachment success and evaluated success as a function of plant community traits (i.e., species richness, species diversity, and species composition). Our results indicated that J. virginiana encroachment success increased with increasing plant richness and diversity. Moreover, growth and survival of J. virginiana seedlings was associated with plant species composition only in the old-field grassland and upland oak forest. These results suggest that greater plant species richness and diversity provide little resistance to J. virginiana encroachment, and the results suggest resource availability and other biotic or abiotic factors are determinants of J. virginiana encroachment success.

Grasshopper (Insecta: Orthoptera: Acrididae) assemblages of tallgrass prairie: influences of fire frequency, topography, and vegetation

1988 ◽  
Vol 66 (7) ◽  
pp. 1495-1501 ◽  
Author(s):  
Edward W. Evans
Keyword(s):  
Species Richness ◽  
Species Composition ◽  
Relative Abundance ◽  
Tallgrass Prairie ◽  
Detrended Correspondence Analysis ◽  
Fire Frequency ◽  
Local Species Richness ◽  
Principal Axes ◽  
Local Plant ◽  
Local Species

Grasshopper assemblages were sampled by sweep net in native tallgrass prairie at Konza Prairie, Kansas, in 1982 – 1986 to assess the influences of fire, topography, and vegetation on local species composition. Species composition at 38 sites was analysed by ordination (detrended correspondence analysis). Frequency of fire and topographic location were reflected along the first two principal axes, respectively. Grass-feeding grasshoppers were more numerous than forb- and mixed-feeding grasshoppers throughout the prairie, but forb and mixed feeders became relatively more frequent as fire frequency decreased. Local species richness of grasshoppers was greater on sites burned infrequently than on sites burned annually or biennially, and on upland than on lowland sites. Local species richness was positively correlated with local plant species richness and diversity, reflecting in part that local relative abundance of forb-feeding grasshoppers was positively correlated with local relative abundance of forbs. Collectively these results are consistent in suggesting that through their effects on local plant communities, fire frequency and topography are major factors influencing the composition of local grasshopper assemblages in tallgrass prairie.

scholarly journals Livestock grazing-induced large-scale biotic homogenization in arid Mediterranean steppe rangelands

2021 ◽  
Author(s):  
Merdas Saifi ◽  
Yacine Kouba ◽  
Tewfik Mostephaoui ◽  
Yassine Farhi ◽  
Haroun Chenchouni
Keyword(s):  
Species Composition ◽  
Spatial Scale ◽  
Plant Communities ◽  
Beta Diversity ◽  
Large Scale ◽  
Management Practices ◽  
Species Turnover ◽  
Livestock Grazing ◽  
Biotic Homogenization ◽  
Arid Steppe

Despite many studies explored the effect of livestock grazing on plant communities, the response of species composition and diversity to livestock grazing in arid rangelands remain ambiguous. This study examined the effects of livestock grazing on plant communities in arid steppe rangelands of North Africa. Plant diversity of annual species, perennial species and all species combined was measured and compared between grazed and grazing-excluded areas. We also examined the relative importance of species turnover and community nestedness. Moreover, the effects of livestock grazing on beta diversity at local among transects and landscape among sites scales were examined using the multiplicative diversity partitioning. Results revealed that livestock grazing significantly decreased the alpha diversity of all species combined and the diversity of annual plants. Livestock grazing induced a shift in plant community composition where most of species composition variation (~74%) was due to infrequent species replacement ‘turnover’ between the two management types rather than nestedness (~26%). Results revealed also that among transects, beta diversity was higher in grazed steppes than in grazing-excluded steppes. Whereas, among sites, beta diversity was lower in grazed steppes compared to grazing-excluded steppes. These findings suggest that livestock grazing in arid steppe rangelands increases the variation in plant species composition at a local spatial scale and engenders vegetation homogeneity at landscape spatial scale. Therefore, the implementation of appropriate management practices such as short-term grazing exclusion is mandatory to prevent these ecosystems from large scale biotic homogenization.

Are trout populations affected by reach-scale stream slope?

2000 ◽  
Vol 57 (2) ◽  
pp. 468-477 ◽  
Author(s):  
Daniel J Isaak ◽  
Wayne A Hubert
Keyword(s):  
Species Composition ◽  
Spatial Scale ◽  
Relative Abundance ◽  
Cross Sections ◽  
Fish Habitat ◽  
Rocky Mountain ◽  
Mountain Streams ◽  
Habitat Models ◽  
High Slope ◽  
Rocky Mountain Streams

Reach-scale stream slope and the structure of associated physical habitats are thought to affect trout populations, yet previous studies confound the effect of stream slope with other factors that influence trout populations. We isolated the effect of stream slope on trout populations by sampling reaches immediately upstream and downstream of 23 marked changes in stream slope on 18 streams across Wyoming and Idaho. No effect of stream slope on areal trout density was observed, but when trout density was expressed volumetrically to control for differences in channel cross sections among reaches in different slope classes, the highest densities of trout occurred in medium-slope reaches, intermediate densities occurred in high-slope reaches, and the lowest densities occurred in low-slope reaches. The relative abundance of large trout was reciprocal to the pattern in volumetric trout density. Trout biomass and species composition were not affected by stream slope. Our results suggest that an assumption made by many fish-habitat models, that populations are affected by the structure of physical habitats, is at times untenable for trout populations in Rocky Mountain streams and is contingent upon the spatial scale of investigation and the population metric(s) used to describe populations.

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