Emily A. Holt

Defining a Successional Metric for Lichen Communities in the Arctic Tundra

Abstract We provide an index of successional status for arctic macrolichen communities based on a synthesis of literature reports. We amassed research from the past 50 years that studied lichen communities following disturbance, such as fire or grazing. Species scores were derived from these reports depending on when a particular macrolichen species appeared following disturbance. Weighted averaging of these data with a community matrix can create a successional score for each sample unit of interest. These scores can be used as a surrogate for community age estimates that are otherwise difficult to obtain from tundra environments above treeline. We test this approach using an example data set of macrolichen communities collected from the Bering Land Bridge National Preserve, Alaska. We found that our successional scores represented roughly 17 and 19% of the community variation, depending on whether the community data set was binary or quantitative. Abundance data tended to yield successional scores that were slightly higher (older) than those derived from a presence-absence data set. We recommend use of our successional metric for lichen communities throughout the arctic tundra to infer successional status of an area.

Macrolichen communities in relation to soils and vegetation in the Noatak National Preserve, Alaska

Macrolichen community structure and its relation to environment in the Noatak National Preserve, Alaska, is de- scribed using a two-way stratified random sample. We found 201 macrolichen taxa. Two primary gradients in lichen spe- cies composition were related to substrate pH and vegetation physiognomy, grading from forests to high alpine communities. Site characteristics associated with the first community gradient are soil moisture and exposure. Both ends of this gradient, including protected forests and densely shrubby sites at one end and exposed, high elevation alpine sites at the other end, are relatively dry and well-drained. The mid-region of this gradient consists of mesic, lowland tundra hab- itats. The second gradient, related to substrate pH, is driven by the presence of Sphagnum moss contrasting with calcareous soils and bedrock. Combining these two gradients of lichen community composition, we found six groups of plots using two-way cluster analysis. Further, division of macrolichen species occurring in five or more plots yielded seven species groups, based on a combination of environmental factors and species distribution characteristics. This snapshot of macroli- chen communities in Arctic Alaska serves as an important baseline for future comparisons to environments altered by changing climate and land use.

Spatial scale of GIS-derived categorical variables affects their ability to separate sites by community composition

ABSTRACT Questions: How well do GIS-derived categorical variables (e.g., vegetation, soils, geology, elevation, geography, and physiography) separate plots based on community composition? How does the ability to distinguish plots by community composition vary with spatial scale, specifically number of patch types, patch size and spatial correlation? Both these questions bear on the effective use of stratifying variables in landscape ecology. Location: Arctic tundra; Bering Land Bridge National Preserve, northwestern Alaska, USA. Methods: We evaluated the strength of numerous alternative stratifying variables using the multi-response permutation procedure (MRPP). We also created groups based on lichen community composition, using cluster analyses, and evaluated the relationship between these groups and groupings within categorical variables using Mantel tests. Each test represents different measures of community separation, which were then evaluated with respect to each variables spatial characteristics. Results: We found each categorical variable derived from GIS separated lichen communities to some degree. Separation success ranged from strong (Alaska Subsections) to weak (Watersheds and Reindeer Ownership). Lichen community groups derived from cluster analysis demonstrated statistically significant relationships with 13 of the 17 categorical variables. Partialling out effects of spatial distance had little effect on these relationships. Conclusions: Greater number of patch types and larger average patch sizes contribute to optimal success in separating lichen communities; geographic distance did not appear to significantly alter separation success. Group distinctiveness or strength increased with more patch types or groups. Alternatively, congruence between lichen community types derived from cluster analysis and the 17 categorical variables was inversely related to patch size and spatial correlation.

The Greatest Learning Return on Your Pedagogical Investment: Alignment, Assessment or In-Class Instruction?

Critical thinking is often considered an essential learning outcome of institutions in higher education. Previous work has proposed three pedagogical strategies to address this goal: more active, student-centered in-class instruction, assessments which contain higher-order cognitive questions, and greater alignment within a classroom (i.e., high agreement of the cognitive level of learning objectives, assessments, and in-class instruction). Our goals were to determine which of these factors, individually or the interactions therein, contributed most to improvements in university students’ critical thinking. We assessed students’ higher-order cognitive skills in introductory non-majors biology courses the first and last week of instruction. For each of the fifteen sections observed, we also measured the cognitive level of assessments and learning objectives, evaluated the learner-centeredness of each classroom, and calculated an alignment score for each class. The best model to explain improvements in students’ high-order cognitive skills contained the measure of learner-centeredness of the class and pre-quiz scores as a covariate. The cognitive level of assessments, learning objectives, nor alignment explained improvements in students’ critical thinking. In accordance with much of the current literature, our findings support that more student-centered classes had greater improvements in student learning. However, more research is needed to clarify the role of assessment and alignment in student learning.

Seeing the Forest and the Trees: Research on Plant Science Teaching and Learning

In this editorial we link the articles published in this Special Focus section with the practical utility of using plants in education to transform and transcend traditional botany classes. We suggest current and future implications of research in this area.

Macrolichen substrate selection: Patterns among aspen, non-aspen hardwood, and conifer-dominated forests in the Wasatch Mountains, Utah

Abstract Lichens in montane, forested ecosystems of the Intermountain West and central Rocky Mountains tend to be understudied. Focusing on forested ecosystems in Utah, specifically Santaquin and Payson Canyons, we describe lichen community diversity and composition and their relation to percent aspen cover, and contrast lichens in aspen, non-aspen hardwood and coniferous environments. We collected 351 macrolichens, a total of 34 species and 15 genera, from 22 circular plots with a 34.7 m radius. We found three major gradients in lichen community composition in our study area. First, many species of Xanthomendoza had strong positive correlations with increasing aspen cover, while several Melanohalea species declined with greater aspen cover. Xanthomendoza galericulata was a significant indicator for aspen forests, but this lichen was not limited to aspen as it colonizes various barks flexibly. Second, corticolous and saxicolous taxa positively associated with a trend in lichen species richness, while terricolous lichens associated with the opposite end of this gradient. The third and weakest gradient was related to the cover of non-aspen hardwoods and the presence of fruticose species. Both lichen community composition and species richness differed significantly among aspen, non-aspen hardwood and conifer-dominated forests. In agreement with previous work in other regions, the non-aspen hardwood forests we sampled supported the most diverse and prolific lichen communities. Lichens of our aspen forests are as diverse as those in conifer-dominated forests, which contrasts with some current literature suggesting that aspen woodlands represent hotspots of diversity for many types of flora and fauna. Our finding that aspen-dwelling lichens markedly contrast with lichens on other substrates, including other hardwoods, contributes to our understanding of lichen community composition in arid, montane forests of the central Rocky Mountains.

Online Plagiarism Training Falls Short in Biology Classrooms

This study compared three plagiarism-avoidance training formats (i.e., no training, online tutorial, or homework assignment) in several undergraduate ecology courses. The authors found that students trained with the homework assignment more successfully identified plagiarism or the lack thereof than did untrained students or students trained with the online tutorial.

Vegetation Patterns Associated With Abiotic Factors and Human Impacts At the Capitol Reef Field Station

Abstract The purpose of this study is to describe plant community structure within Capitol Reef National Park and identify possible effects of disturbance. We used Capitol Reef Field Station (Capitol Reef FS) as a proxy for current and historic disturbance. We collected data using two, 100-m transects located at differing proximities to Capitol Reef FS in each of four community types: pinyon-juniper, sagebrush, riparian, and grassland. Species frequency and percent cover were recorded within each transect using 20, 4-m2 plots. We used ordinations to describe gradients in community structure as they relate to the environment and disturbance. We compared community structure and environmental factors by vegetation type, proximity to Capitol Reef FS, and through time. We found that the two main gradients in community structure were represented by a soil nutrient and texture gradient and an annual species and phosphorus gradient. Specifically, the concentrations of many soil nutrients were inversely related to soil texture size, while the amount of available phosphorus was positively associated with litter cover and the prevalence of annual species. Surface cover attributes, along with percent of annual and introduced species, differed among the vegetation types. Although we found that species composition is associated with proximity to Capitol Reef FS, no environmental factors differed by distance to the field station except for litter cover. Additional data are needed to separate the legacy effects of historical disturbance from current use of the field station.