Search

Premise: Understanding edaphic specialization is crucial for conserving rare plants that may need relocation due to habitat loss. Focusing on Eriogonum crosbyae, a rare soil specialist in the Great Basin of the United States, we asked how site-level variation among volcanic soil outcrops affected plant growth and population distribution., Methods: We measured emergence, survival, size, and biomass allocation of E. crosbyae seedlings planted in soils collected from 42 outcrops of actual and potential habitat. We also measured phenotypic variation in the wild, documented abiotic and biotic components of E. crosbyae habitat, re-surveyed Nevada populations, and evaluated occupancy changes over time., Results: Plants responded plastically to edaphic variation, growing larger and allocating relatively more to aboveground tissues in soils with greater nutrient availability and growing smaller in soils higher in copper in the field and the greenhouse. However, the chemical and physical soil properties we measured did not predict site occupancy, nor was plant phenotype in the greenhouse different when plants were grown in soils from sites with different occupation status. We observed occupation status reversals at five locations., Conclusions: Eriogonum crosbyae performed well in soils formed on hydrothermally altered rocks that are inhospitable to many other plants. Extirpation/colonization events observed were consistent with metapopulation dynamics, which may partially explain the patchy distribution of E. crosbyae among outcrops of potential habitat. While soil properties did not predict site occupancy, early life stages showed sensitivity to soil variation, indicating that seedling dynamics may be important to consider for the conservation of this soil specialist., (© 2020 Botanical Society of America.)

Expansion of native pinyon-juniper (Pinus monophylla-Juniperus osteosperma) woodlands can decrease shrub and herbaceous cover in the Intermountain West, U.S., affecting habitat quality and biodiversity. Removing pinyon-juniper woodlands in former sagebrush ecosystems to increase understory cover has a long management history, and short- and long-term monitoring reveal different understory plant community responses. We revisited a 500 mm average precipitation site in the sagebrush steppe of western Nevada, 32 years after three types of tree thinning treatments and seeding had occurred in a mature, closed-canopy woodland. We measured vegetation foliar cover and density within plots arranged in a 3-block randomized design. We found significantly lower cover of P. monophylla in treated plots (average of 2-8%), relative to controls (32%). However, P. monophylla seedlings (<0.5 m tall) were detected throughout all plots (average of 86-160 trees/ha in treated plots, 111 in controls). Cover of perennial graminoids and shrubs was higher in all treatments (600-870% higher grass cover and 470-570% higher shrub cover) than controls. Cover of invasive annual species, primarily Bromus tectorum, was highly variable and not significantly different among plots, but B. tectorum had the highest cover of all species in two of the three woodland removal treatment types. Control plots contained significantly larger perennial canopy gaps compared to all treatments (average of 318 cm vs. 104-133 cm), and had significantly more woody litter cover than clear cut plots (average of 14% vs. 3%). These results suggest tree thinning and removal in tree dominated woodlands can increase shrub and perennial grass cover and reduce litter and canopy gaps, especially in conjunction with seeding, but that tree recolonization over the long-term is inevitable. Perennial forbs did not respond well to treatments (<1% average foliar cover in all plots), and seeding or other treatments may be needed to improve their response. Further, if tree seedlings survive, these plots will likely return to tree dominance without additional treatments., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Unlabelled: •, Premise of the Study: The ability to respond to environmental change via phenotypic plasticity may be important for plants experiencing disturbances such as climate change and plant invasion. Responding to belowground competition through root plasticity may allow native plants to persist in highly invaded systems such as the cold deserts of the Intermountain West, USA.•, Methods: We investigated whether Poa secunda, a native bunchgrass, could alter root morphology in response to nutrient availability and the presence of a competitive annual grass. Seeds from 20 families were grown with high and low nutrients and harvested after 50 d, and seeds from 48 families, grown with and without Bromus tectorum, were harvested after ∼2 or 6 mo. We measured total biomass, root mass fraction, specific root length (SRL), root tips, allocation to roots of varying diameter, and plasticity in allocation.•, Key Results: Plants had many parallel responses to low nutrients and competition, including increased root tip production, a trait associated with tolerance to reduced resources, though families differed in almost every trait and correlations among trait changes varied among experiments, indicating flexibility in plant responses. Seedlings actively increased SRL and fine root allocation under competition, while older seedlings also increased coarse root allocation, a trait associated with increased tolerance, and increased root mass fraction.•, Conclusions: The high degree of genetic variation for root plasticity within natural populations could aid in the long-term persistence of P. secunda because phenotypic plasticity may allow native species to persist in invaded and fluctuating resource environments., (© 2015 Botanical Society of America, Inc.)

Cheatgrass (Bromus tectorum) is an invasive weed in western North America found primarily growing at elevations less than 2200 m. We asked whether cheatgrass is capable of becoming adapted to a marginal habitat, by investigating a population at a high elevation invasion edge. We used a combination of methods, including reciprocal field transplants, controlled environment studies and molecular analysis. High levels of SSR gene diversity (0.50 vs. 0.43) and comparable variation in phenotypic traits were observed at both the invasion edge and a low elevation, high-density population. Three heterozygotes were observed in the edge population, which is unusual in this predominantly self-pollinating plant. Plants from high elevations germinated more slowly in a growth chamber and had slower seedling growth rates. Survivorship was low at the edge (13%), compared with the low elevation site (55%), but surviving plants were of similar size and had equivalent reproductive output. Seed size positively affected survival and plant performance in the field and this trait was inherited. Emergence timing affected survival at the low elevation site and germination timing was also inherited. Local adaptation was seen in the low, rather than in the high elevation site, because of differential survival. While there was no evidence for local adaptation to the high elevation site observed in the field, family level and genotype-level differences in traits that affected field performance, high genetic diversity at the invasion edge, and evidence of outcrossing in this highly selfing species indicates that the potential for adaptation to a marginal habitat exists within this population.