Geology topics

Nicole Pietrasiak

Publications and source records attributed to Nicole Pietrasiak.

3 recordsLinked to original sources

USGS2025

Evaluation of the gap intercept method to measure rangeland connectivity

Characterizing the connectivity of materials, organisms, and energy on rangelands is critical to understanding and managing ecosystem response to disturbances. For over twenty years, scientists and rangeland managers have used the gap intercept method to monitor connectivity. However, using gap intercept measurements to infer ecosystem processes or inform management actions and conservation practices on rangelands has been limited because there are few tools and syntheses to help managers pragmatically interpret gap measurements. In this synthesis, we review the different ways the gap intercept method is conducted and highlight considerations when collecting and using gap intercept data. We discuss what is known about how gap intercept data can be used to assess wind and water erosion, biocrust abundance and composition, soil fertility, plant community dynamics, wildlife habitat characteristics, and fuel connectivity and fire behavior. Finally, we identify emerging opportunities regarding the collection and use of gap intercept data to assess rangeland connectivity, ecosystem function, and ecological processes. Through this synthesis we demonstrate the value of the gap intercept method, particularly “all-plant” (i.e., whole-community) canopy gap, in supporting assessments of rangeland condition and vulnerability, and in planning future management actions.

Rangeland Ecology & Management↗

USGS2019

Passive restoration of vegetation and biological soil crusts following 80 years of exclusion from grazing across the Great Basin

Restoration targets for biological soil crusts are largely unknown. We surveyed seven 80‐year‐old grazing exclosures across northern Nevada for biocrusts to quantify reference conditions at relatively undisturbed sites. Exclosures were associated with the following plant communities: Wyoming big sagebrush, black sagebrush, and areas co‐dominated by winterfat and Wyoming big sagebrush. Cover of biocrusts and shrubs were generally higher than other plant groups at these sites, regardless of being inside or outside of the exclosures, suggesting these groups make up most of the native flora across the region. Important in forming soil structure, cyanobacteria of the order Oscillatoriales were less abundant and diverse in black sagebrush communities. Grazing had a negative effect on the abundance of Oscillatoriales but not the number of algal taxa, including cyanobacteria. Abundance of light algal crusts were not influenced by plant community or grazing. Dark algal crusts were generally less abundant on grazed sites. Influences of plant community and grazing were most apparent when accounting for reproductive rates of lichens and mosses based on establishment mechanisms. Abundance of shrubs, perennial grasses, Oscillatoriales, fast reproducing biocrusts and the number of algal and cyanobacterial taxa, varied by plant community, suggesting that restoration should be plant community specific. We demonstrate the affinity of rapidly reproducing biocrusts for winterfat‐Wyoming big sagebrush co‐dominated plant communities, regardless of grazing pressure. Across sites, the effects of grazing were most evident on the abundance of Oscillatoriales and slowly reproducing biocrusts following 80 years of cessation from grazing.

Great Basin↗

USGS2016

Controls on distribution patterns of biological soil crusts at micro- to global scales

Biocrusts are heterogeneously distributed in space. The drivers of their distribution patterns vary depending on the spatial scale of observation. Globally, there are about 1337 cyanobacteria, algae, bryophyte, and lichen species reported as components of biocrusts. At the broadest biogeographical scales, the degree and age of isolation of land masses may dictate distribution of these species and the similarities of the floras of different continents. At intra-continental and smaller scales, climate strongly influences abundance and community composition of biocrusts. Within drylands, biocrusts become more abundant as precipitation increases. The seasonality of rainfall is about equally important, with regions receiving most precipitation as winter rain and snow exhibiting the highest abundance and greatest relative cover of bryophyte and lichens vs. cyanobacteria. Temperature gradients may dictate the dominant cyanobacterium present in the community. At eco-regional and smaller scales, edaphic gradients determined by either soil parent materials or geomorphology or both become particularly influential. Globally, the most significant soil properties influencing the eco-regional scale cover and richness of biocrusts in dryland environments are soil texture, pH, and soil CaCO3 content. Sandier soils tend to favour development of cyanobacterial biocrusts, whereas mosses and lichens tend to be more abundant on finer textured soils. The alkalinity and CaCO3 content of soils are associated with greater bioocrust abundance in some regions, and dictates the species composition in the bryophyte and lichen component. Globally, gypsiferous soils are often associated with distinct floras and high abdundances of biocrusts, especially lichens. At local to micro-scales, biocrusts often are better developed in habitats with lower radiation loads such as polar-oriented slopes, or shaded habitats. Also at small scales, vascular plant canopies buffer microclimate for biocrusts, but also exert negative influences such as burial by litter. While our knowledge of biocrust distribution has advanced rapidly, there are considerable geographic and taxonomic gaps in our knowledge and a pronounced lack of truly global studies.

Book chapter↗