Overcoming the Barriers to Teaching Teamwork to Undergraduates in STEM.

There is widespread recognition that undergraduate students in the life sciences must learn how to work in teams. However, instructors who wish to incorporate teamwork into their classrooms rarely have formal training in how to teach teamwork. This is further complicated by the application of synonymous and often ambiguous terminology regarding teamwork that is found in literature spread among many different disciplines. There are significant barriers for instructors wishing to identify and implement best practices. We synthesize key concepts in teamwork by considering the knowledge, skills, and attitudes (KSAs) necessary for success, the pedagogies and curricula for teaching those KSAs, and the instruments available for evaluating and assessing success. There are only a limited number of studies on teamwork in higher education that present an intervention with a control group and a formal evaluation or assessment. Moreover, these studies are almost exclusively outside STEM disciplines, raising questions about their extensibility. We conclude by considering how to build an evidence base for instruction that will empower students with the KSAs necessary for participating in a lifetime of equitable and inclusive teamwork.

Biological invasions and climate change amplify each other's effects on dryland degradation.

Climate models predict that, in the coming decades, many arid regions will experience increasingly hot conditions and will be affected more frequently by drought. These regions are also experiencing rapid vegetation change, notably invasion by exotic grasses. Invasive grasses spread rapidly into native desert ecosystems due, in particular, to interannual variability in precipitation and periodic fires. The resultant destruction of non-fire-adapted native shrub and grass communities and of the inherent soil resource heterogeneity can yield invader-dominated grasslands. Moreover, recurrent droughts are expected to cause widespread physiological stress and mortality of both invasive and native plants, as well as the loss of soil resources. However, the magnitude of these effects may differ between invasive and native grasses, especially under warmer conditions, rendering the trajectory of vegetated communities uncertain. Using the Biosphere 2 facility in the Sonoran Desert, we evaluated the viability of these hypothesized relationships by simulating combinations of drought and elevated temperature (+5°C) and assessing the ecophysiological and mortality responses of both a dominant invasive grass (Pennisetum ciliare or buffelgrass) and a dominant native grass (Heteropogan contortus or tanglehead). While both grasses survived protracted drought at ambient temperatures by inducing dormancy, drought under warmed conditions exceeded the tolerance limits of the native species, resulting in greater and more rapid mortality than exhibited by the invasive. Thus, two major drivers of global environmental change, biological invasion and climate change, can be expected to synergistically accelerate ecosystem degradation unless large-scale interventions are enacted.

Tree species fine-root demography parallels habitat specialization across a sandhill soil resource gradient.

Single species can substantially alter belowground processes in ecosystems via differential root production and death. However, information on species differences in fine-root demography is virtually absent for natural communities. In this field study, we recorded species-specific fine-root (<2 mm in diameter) demography in adults of four tree species (Pinus palustris, Quercus laevis, Q. incana, and Q. margaretta) that are distributed differentially along soil resource gradients in the fall-line sandhills of the southeastern United States. At a subxeric habitat where all four species co-occur, roots of individual trees of each species were isolated in rhizotrons and tracked individually for three years. Quercus species had similar fine-root morphology but differed substantially for fine-root demography and architecture. Quercus laevis and Q. incana, the species from xeric habitats, showed lower fine-root production, death, percentage mortality, turnover rates, and risk of death, and greater life span and mean root segment length (MRSL) than Q. margaretta, the species from subxeric habitats. Fine roots of P. palustris (a generalist) showed high production and intermediate mortality, turnover rate, longevity, and MRSL. Fine-root survival increased with root order (first to fourth in centripetal order), but the degree of change was species specific. Q. margaretta showed greater increases in survival with order, but all species had similar demography of third- and fourth-order roots. Mycorrhizal roots had greater longevity than non-mycorrhizal roots only in Q. laevis. Species differences were also seasonal. Although these Quercus species are leaf deciduous, some growth of fine roots occurred in Q. margaretta during the "leaf-dormant" season. In our narrow-scale species comparison, species differences in ecological distribution were consistent with the observed variation in fine-root demography and architecture with greater resolution than leaf characters or other root traits such as morphology. Our results also show that narrow-scale variation in fine-root demography (including intra-generic differences) can be as large as broad-scale variation across biomes and vegetation types. Hence, small shifts in community composition have the potential to produce substantial changes below ground.

Responses of citrus fine roots to localized soil drying: a comparison of seedlings with adult fruiting trees.

We studied the responses of citrus (Citrus volkameriana Tan. & Pasq.) roots to 15 weeks of soil drying. A comparison was made between the fine roots of 1-year-old seedling root systems (seedling) and the fine roots of woody laterals of 6-year-old grafted trees (adult). Each seedling and woody lateral root system was established in a pair of vertically separated and independently irrigated soil compartments located in field root chambers excavated adjacent to the trees to which the woody laterals were attached. Root + soil respiration and fine root survival of seedlings and adults were similar for the first 5 weeks. However, eight weeks after termination of irrigation to the upper soil compartments, mortality of fine roots was high in adults but not seedlings. Fine roots of adults exposed to dry soil for 5, 8 and 15 weeks exhibited 2, 26 and 33% mortality, respectively, whereas the corresponding values for fine roots of seedlings were 2, 6 and 8%. Although root + soil respiration rates of adults and seedlings were similar before the soil drying treatment, rates for adults were only 25% of those for seedlings after 15 weeks of soil drying. We conclude that, although fine roots of adults and seedlings are similar in form, they respond differently to soil drying.