Geum Rossii Research Articles

Microhabitat requirements of the uncompahgre fritillary butterfly (Boloria improba acrocnema) and climate change implications

The Uncompahgre fritillary butterfly (Boloria improba acrocnema Gall LF, Sperling FAH (1980) A new high altitude species of Boloria from southwestern Colorado (Nyphalidae), with a discussion of phenetics and hierarchical decisions. J Lepidopterists’ Soc 34:230–252 1980) was listed as federally endangered in 1991 and is considered a habitat indicator for alpine ecosystem health. They are found on patches of Salix nivalis in isolated habitats of the San Juan Mountains, Colorado, USA. Here, we estimated historical B. i. acrocnema abundance from annual distance sampling (2003–2020) at seven sub-colonies and sampled current (July 2021) measurements of herbaceous coverage, soil moisture content, and slope, aspect, and elevation at 700 sample sites. We used regression models to test the effects of these microhabitat characteristics on historical abundance. Our results show that increases in slope from 11° to 31°, individual coverage of five alpine plant species (S. nivalis, Geum rossii, Phacelia sericea, Noccaea fendleri, and Lewisia pygmaea), and soil moisture content between 0.09 m3/m3 and 0.38 m3/m3 positively influence butterfly abundance. However, increases in elevation, bare ground coverage, and presence of Salix planifolia, Aster alpinus, Antennaria media, and Androsace chamaejasme were correlated with lower abundance estimates.Implications for insect conservation Effects of climate change which decrease coverage of these alpine plant species, allow encroachment of lower elevation species, or reduce soil moisture will decrease B. i. acrocnema abundance. These results emphasize the extinction risk of B. i. acrocnema due to range limitations and prolonged drought conditions in the Western U.S. By defining additional resource requirements of B. i. acrocnema, we can model climate effects on survivorship and consider nearby microhabitats that may be habitable by this endangered species.

Sampling a pika's pantry: Temporal shifts in nutritional quality and winter preservation of American pika food caches

AbstractClimate change is increasing temperature, decreasing precipitation, and increasing atmospheric CO2 concentrations in many ecosystems. As atmospheric carbon rises, plants may increase carbon‐based defenses, such as phenolics, thereby potentially affecting food quality, foraging habits, and habitat suitability for mammalian herbivores. In alpine habitats, the American pika (Ochotona princeps) is a model species for studying effects of changing plant chemistry on mammals. To survive between growing seasons, pikas cache “haypiles” of plants rich in phenolics. Although they are toxic to pikas, phenolic compounds facilitate retention of plant biomass and nutrition during storage, and they degrade over time. Alpine avens (Geum rossii, Rosales: Rosaceae) is a high‐phenolic plant species that comprises up to 75% of pika haypiles in Colorado. Here, we tested the hypothesis that contemporary climate change has affected the nutritional value of alpine avens to pikas in the last 30 years. Specifically, we compared phenolic activity, nutritional quality, and overwinter preservation of plants collected at Niwot Ridge, Colorado (USA), in 1992 to those collected between 2010 and 2018, spanning nearly three decades of climate change. Phenolic activity increased in alpine avens since 1992, while fiber and nitrogen content decreased. Importantly, overwinter preservation of plant biomass also increased, particularly on windblown slopes without long‐lasting snow cover. Previous studies indicate that pikas at this site still depend on alpine avens for their winter food caches. Higher phenolic content in alpine avens could therefore enhance the preservation of haypiles over winter; however, if pikas must further delay consuming these plants to avoid toxicity or invest extra energy in detoxification, then the nutritional gains from enhanced preservation may not be beneficial. This study provides important insights into how climate‐driven changes in plant chemistry will affect mammalian herbivores in the future.

Four decades of new vascular plant records for Greenland.

Records of new species of vascular plants in Greenland from the last four decades are presented and new phytogeographical data leading to extension of the known distribution limits in Greenland are discussed. Since the publication of the latest edition of the Flora of Greenland in 1978 (Böcher et al. 1978) fieldwork by Greenland Botanical Survey and other expeditions have taken place especially in West and East Greenland and in many remote areas in North and Northeast Greenland. This paper serves as an update of the Flora of Greenland. Twenty species, one subspecies and one new forma have been added to the flora of Greenland: Carex membranacea Hook., Carex miliaris Michx., Carex rhomalea (Fernald) Mack., Equisetum hyemale L., Festuca edlundiae S. Aiken, Consaul and Lefkovich, Festuca groenlandica (Schol.) Frederiksen, Festuca saximontana Rydb., Galium verum L., Geum rossii (R. Br.) Ser., Papaver cornwallisense D. Löve, Papaver dahlianum Nordh., Papaver labradoricum (Fedde) Solstad and Elven, Papaver lapponicum (Tolm.) Nordh., Pedicularis sudetica Willd. ssp. albolabiata Hult., Poa flexuosa Sm., Puccinellia bruggemanni Th. Sør., Ranunculus subrigidus W.B. Drew., Silene vulgaris (Moench) Garcke, Trientalis europaea L. and Veronica officinalis L. in addition to one subspecies Phippsia algida (Sol.) R. Br. ssp. algidiformis (H. Sm.) Löve and Löve. The viviparous form of Poa hartzii f. prolifera has been reported for the first time in Greenland. Presently, the total number of vascular plant species in Greenland is 532. 89 new northern and 28 new southern distribution limits are presented and 26 species are new to the flora province East Greenland, whereas 15 species are new to West Greenland. The numbers of new species to flora provinces North and South Greenland are 14 and one, respectively.

Snowmelt Timing Regulates Community Composition, Phenology, and Physiological Performance of Alpine Plants.

The spatial patterning of alpine plant communities is strongly influenced by the variation in physical factors such as temperature and moisture, which are strongly affected by snow depth and snowmelt patterns. Earlier snowmelt timing and greater soil-moisture limitations may favor wide-ranging species adapted to a broader set of ecohydrological conditions than alpine-restricted species. We asked how plant community composition, phenology, plant water relations, and photosynthetic gas exchange of alpine-restricted and wide-ranging species differ in their responses to a ca. 40-day snowmelt gradient in the Colorado Rocky Mountains (Lewisia pygmaea, Sibbaldia procumbens, and Hymenoxys grandiflora were alpine-restricted and Artemisia scopulorum, Carex rupestris, and Geum rossii were wide-ranging species). As hypothesized, species richness and foliar cover increased with earlier snowmelt, due to a greater abundance of wide-ranging species present in earlier melting plots. Flowering initiation occurred earlier with earlier snowmelt for 12 out of 19 species analyzed, while flowering duration was shortened with later snowmelt for six species (all but one were wide-ranging species). We observed >50% declines in net photosynthesis from July to September as soil moisture and plant water potentials declined. Early-season stomatal conductance was higher in wide-ranging species, indicating a more competitive strategy for water acquisition when soil moisture is high. Even so, there were no associated differences in photosynthesis or transpiration, suggesting no strong differences between these groups in physiology. Our findings reveal that plant species with different ranges (alpine-restricted vs. wide-ranging) could have differential phenological and physiological responses to snowmelt timing and associated soil moisture dry-down, and that alpine-restricted species’ performance is more sensitive to snowmelt. As a result, alpine-restricted species may serve as better indicator species than their wide-ranging heterospecifics. Overall, alpine community composition and peak % cover are strongly structured by spatio-temporal patterns in snowmelt timing. Thus, near-term, community-wide changes (or variation) in phenology and physiology in response to shifts in snowmelt timing or rates of soil dry down are likely to be contingent on the legacy of past climate on community structure.

Assembly of root-associated bacteria communities: interactions between abiotic and biotic factors.

Nitrogen (N) deposition in many areas of the world is over an order of magnitude greater than it would be in absence of human activity. We ask how abiotic (N)and biotic (plant host and neighborhood) effects interact to influence root-associated bacterial (RAB)community assembly. Using 454 pyrosequencing, we examined RAB communities from two dominantal pine tundra plants, Geum rossii and Deschampsia cespitosa, under control, N addition and D. cespitosa removal treatments, implemented in a factorial design. We hypothesized that host would have the strongest effect on RAB assembly, followed by N,then neighbor effects.The most dominant phyla were Proteobacteria (mostly Gammaproteobacteria), Actinobacteria,Bacteroidetes and Acidobacteria. We found RAB communities were host specific, with only 17% overlap in operational taxonomic units. Host effects on composition were over twice as strong as Neffects. D. cespitosa RAB diversity declined with N, while G. rossii RAB did not. D. cespitosa removal did not influence G. rossii RAB community composition, but G. rossii RAB diversity declined with N only when D. cespitosa was absent. We conclude that RAB of both hosts are sensitive to N enrichment, and RAB response to N is influenced by host identity and plant neighborhood.

Nitrogen deposition alters plant–fungal relationships: linking belowground dynamics to aboveground vegetation change

Nitrogen (N) deposition rates are increasing globally due to anthropogenic activities. Plant community responses to N are often attributed to altered competitive interactions between plants, but may also be a result of microbial responses to N, particularly root-associated fungi (RAF), which are known to affect plant fitness. In response to N, Deschampsia cespitosa, a codominant plant in the alpine tundra at Niwot Ridge (CO), increases in abundance, while Geum rossii, its principal competitor, declines. Importantly, G.rossii declines with N even in the absence of its competitor. We examined whether contrasting host responses to N are associated with altered plant-fungal symbioses, and whether the effects of N are distinct from effects of altered plant competition on RAF, using 454 pyrosequencing. Host RAF communities were distinct (only 9.4% of OTUs overlapped). N increased RAF diversity in G.rossii, but decreased it in D.cespitosa. D.cespitosa RAF communities were more responsive to N than G.rossii RAF communities, perhaps indicating a flexible microbial community aids host adaptation to nutrient enrichment. Effects of removing D.cespitosa were distinct from effects of N on G.rossii RAF, and D.cespitosa presence reversed RAF diversity response to N. The most dominant G.rossii RAF order, Helotiales, was the most affected by N, declining from 83% to 60% of sequences, perhaps indicating a loss of mutualists under N enrichment. These results highlight the potential importance of belowground microbial dynamics in plant responses to N deposition.

Nitrogen deposition, plant carbon allocation, and soil microbes: Changing interactions due to enrichment

Nitrogen (N) inputs to the terrestrial environment have doubled worldwide during the past century. N negatively impacts plant diversity, but it is unknown why some species are more susceptible than others. While it is often assumed that competition drives species decline, N enrichment also strongly affects soil microbial communities. Can these changes affect plant-microbe interactions in ways that differentially influence success of plant species? Furthermore, can altered plant-microbe interactions lead to carbon (C) limitation in plants? We focused on a species that increases (Deschampsia cespitosa) and one that decreases (Geum rossii) in abundance in N-fertilized plots in alpine tundra. We measured soil microbes using phospholipid fatty acids, and C limitation and transfer using a (13)C tracer experiment, C:N ratios, nonstructural carbohydrates, and leaf preformation. While N profoundly influenced microbial communities, this change occurred similarly in association with both plant species. N addition did not alter total C allocation to microbes in either species, but it changed patterns of microbial C acquisition more in Geum, specifically in gram-negative bacteria. Geum showed evidence of C limitation: it allocated less C to storage organs, had lower C:N and carbohydrate stores, and fewer preformed leaves in N plots. Carbon limitation may explain why some species decline with N enrichment, and the decline may be due to physiological responses of plants to N rather than to altered plant-microbe interactions. Global change will alter many processes important in structuring plant communities; noncompetitive mechanisms of species decline may be more widespread than previously thought.

PLANT AND MICROBE CONTRIBUTION TO COMMUNITY RESILIENCE IN A DIRECTIONALLY CHANGING ENVIRONMENT

To understand the role biota play in resilience or vulnerability to environmental change, we investigated soil, plant, and microbial responses to a widespread environmental change, increased nitrogen (N). Our aim was to test the plant–soil threshold hypothesis: that changed biotic structure influences resilience to accumulated changes in N. For six years, we removed one of two codominant species, Geum rossii and Deschampsia caespitosa, in moist-meadow alpine tundra in Colorado, USA. We also manipulated nutrient availability by adding carbon (C) or N, separately and in combination with the species removals. Consistent with our hypothesis, Geum was associated with soil feedbacks that slowed rates of N cycling and Deschampsia with feedbacks that increased rates of N cycling. After a four-year initial resilience period, Geum dramatically declined (by almost 70%) due to increasing N availability. In contrast, Deschampsia abundance did not respond to changes in N supply; it only responded to the removal of Geum. Forbs and graminoids responded more positively to Deschampsia removal than to Geum removal, indicating stronger competitive effects by Deschampsia. The changed biotic interactions appear to have community-level consequences: after six years of Geum (but not Deschampsia) removal, evenness of the community declined by over 35%. Increased N affected the soil–microbial feedbacks, particularly in association with Geum. Microbial biomass N declined at higher N, as did the activities of two C-acquiring and one N-acquiring extracellular microbial enzymes. In the presence of Geum, N fertilization slowed the activity of phenol oxidase, a tannin-degrading enzyme, suggesting that microbes shift from degrading Geum-derived compounds. In the absence of Geum, acid phosphatase activity increased, suggesting increased phosphorus limitation in association with Deschampsia. With continued N deposition forecast for this system, these results suggest that initial resilience of Geum to increased N will be overwhelmed through elimination of microbial feedbacks. Once Geum declines, the loss will indirectly facilitate Deschampsia via competitive release. Because Deschampsia exerts strong competitive effects on subordinate species, increased Deschampsia abundance may be accompanied by a community-wide drop in diversity. We conclude that plant–soil feedbacks through the microbial community can influence vulnerability to exogenous changes in N and contribute to threshold dynamics.

Restoration of an Alpine Disturbance: Differential Success of Species in Turf Transplants, Colorado, U.S.A.

Evaluating techniques for restoring alpine environments is important due to increasing human impacts on Colorado mountains. We studied restoration success after 1 yr on an alpine area disturbed by trampling at 3700 m a.s.l., Humboldt Peak, Sangre de Cristo Mountains, Colorado. This area was revegetated in summer 1997 by transplanting pieces of turf cut from a new trail. For both transplants and controls, 100 points were sampled in seventeen 70 × 70 cm plots. Vascular plant species richness did not differ between transplant and control plots. Thirty-one species showed absolute covers not significantly different between transplant and control plots, and twelve species had higher covers in control plots or showed a strong trend in that direction. Sums of covers of all species declined by 35% in transplant plots. Transplant and control plots had differential relative success of some important species as measured by relative cover although almost all differences were small. Grasses increased moderately and forbs declined by 9%. Relative cover of the dominant, Geum rossii, as well as two common graminoids, Carex phaeocephala and Trisetum spicatum, decreased in transplant plots. The forbs Polygonum bistortoides and Potentilla subjuga increased in relative cover in transplant plots; one of the dominant species, Carex elynoides, and many secondary species, were not different between treatments. Success in total cover and of almost all species after 1 yr indicates turf-transplants work well in this community and should be employed to restore other damaged alpine areas when feasible.

Restoration of an Alpine Disturbance: Differential Success of Species in Turf Transplants, Colorado, U.S.A.

Evaluating techniques for restoring alpine environments is important due to increasing human impacts on Colorado mountains. We studied restoration success after 1 yr on an alpine area disturbed by trampling at 3700 m a.s.l., Humboldt Peak, Sangre de Cristo Mountains, Colorado. This area was revegetated in summer 1997 by transplanting pieces of turf cut from a new trail. For both transplants and controls, 100 points were sampled in seventeen 70 × 70 cm plots. Vascular plant species richness did not differ between transplant and control plots. Thirty-one species showed absolute covers not significantly different between transplant and control plots, and twelve species had higher covers in control plots or showed a strong trend in that direction. Sums of covers of all species declined by 35% in transplant plots. Transplant and control plots had differential relative success of some important species as measured by relative cover although almost all differences were small. Grasses increased moderately and forbs declined by 9%. Relative cover of the dominant, Geum rossii, as well as two common graminoids, Carex phaeocephala and Trisetum spicatum, decreased in transplant plots. The forbs Polygonum bistortoides and Potentilla subjuga increased in relative cover in transplant plots; one of the dominant species, Carex elynoides, and many secondary species, were not different between treatments. Success in total cover and of almost all species after 1 yr indicates turf-transplants work well in this community and should be employed to restore other damaged alpine areas when feasible.

Responses of Snowbed Plant Species to Changes in Growing‐Season Length

We assessed the role of growing—season length in regulating absolute and relative cover of six coexisting dominant plant species in an alpine snowbed habitat. To help explain disparity in species—specific responses to growing—season length, we examined the developmental phenology and distribution of each species in relation to natural snow depth variation. Season length varies from °50 d on early—melting edges of the snowbed to 35 d in the late—melting center, 100 m away. By experimentally altering snowpack, we uncoupled the relationship between spatial location and snowmelt schedule in three consecutive years, imposing the same early dates of snow release in a "long growing—season" treatment and the same late dates of snow release in a "short growing—season" treatment near the edge and center of the snowbed. Over the course of the experiment, growing—season length had significant effects on absolute and relative cover of the species studied (P < 0.025 and P < 0.005, respectively), and these effects were similar near both the edge and center of the snowbed. Yet, only for the snowbed specialist, Sibbaldia procumbens, were changes in absolute and relative cover under early and late snowmelt schedules predictable from the species' distribution along the historical snow depth gradient. S. procumbens increased in cover under a long growing—season and was more common in historically early—melting portions of the snowbed. Other species (e.g., Ranunculus adoneus, Artemisia scopulorum) were equally common in historically early— and late—melting locations within the snowbed, but showed discordant responses to experimentally imposed changes in snowmelt schedule. That the cover of many species under long—vs. short growing seasons was not predictable from their current distributional affinities in relation to snowmelt pattern likely reflects the disparity between the rates of processes exerting long—term control on species' abundances (colonization, soil development) and more immediate effects of growing—season length on plant growth. Consistent with this view, differences in developmental phenology better predicted species—specific responses to snowmelt schedule than distributional affinities. Species having leaf expansion schedules that are poorly synchronized with snowmelt typically had similar cover under early vs. late schedules of snow release (Geum rossii, Trifolium parryi, and Poa alpina). In contrast, species in which leaf expansion schedules are synchronized with snowmelt responded positively to early snow release (Ranunculus adoneus and Sibbaldia procumbens). We hypothesize that maintaining metabolic "readiness" under snowcover provides a mechanism for monopolizing nutrient flushes and competitor free intervals at snowmelt, and exploiting occasional long intervals for growth in years of little snow accumulation, but incurs a respiratory cost that is manifest as reduced growth and vegetative cover when snowmelt is delayed. Our results suggest that interspecific differences in growth phenology of coexisting species will promote shifts in snowbed plant communities with climate change within generations.

Taxa of vascular plants new to the flora of Greenland

The vascular plant flora of Greenland has been increased by four new species, Puccinellia bruggemanni, Pedicularis sudetica ssp. albolabiata, Geum rossii, and Trientalis europaea, and one subspecies, Phippsia algida ssp. algidiformis. In addition, the viviparous form of Poa hartzii f. prolifera has been found for the first time in Greenland. For each taxa a description of the habitat, the known distribution in Greenland, and the total distribution are given. The possible immigration routes and relative age of the species in the Greenland flora are discussed. Totally, the number of vascular plant species in Greenland has been increased by eleven since the publication of the Flora of Greenland in 1978 giving 513.

A phytogeographical study of the vascular plants of northern Greenland - north of 74° northern latitude

The phytogeography, flora, and vegetation of northern Greenland, north of 74°N have been investigated. The study area comprises the northern part of high arctic Greenland. The distribution of the 218 taxa of vascular plants has been mapped and classified into 14 distribution types with 16 subtypes. Based on the larger plant material obtained during the intensive botanical exploration of the area in the last decade the delimitation of the phytogeographical units as defined by Seidenfaden and Sørensen (1937) and Bacher et al. (1959) has been tested.
 The delimitation of the floristic province North Greenland, north of 79°30'N, has been confirmed, now divided, however, into a coastal and an inland district based on the distribution of selected species which in North Greenland are restricted to the interior. The coastal district is considered the polar desert zone in high arctic Greenland.
 The delimitation of the districts in the floristic province Northwest Greenland has been accepted, whereas the delimitation of the originally proposed districts in the floristic province Northeast Greenland has been altered. Here the border between the continental and the oceanic floristic province has been moved in an eastward direction. Further, the northern district in the continental province is divided into two districts based .m a marked floristic limit by Bessel Fjord (76°N), where several low arctic species have their northern limit, thus giving a total of four districts in continental Northeast Greenland. No evidence for maintaining the subdivision of the oceanic floristic province in Northeast Greenland at Wollaston Farland has been found. This limit is expected to be found south of the study area.
 Four taxa new to the flora of Greenland have been recognized or found: Puccinellia bruggemanni Th. Sør., Phippsia algida (Sol.) R. Br. ssp. algidiformis (H. Sm.) L. & L., Geum rossii (R. Br.) Ser., and Pedicularis sudetica Willd. ssp. albolabiata Hult. giving a total of 121 taxa known from North Greenland north of 79°30'N. The total number of taxa in Northwest and Northeast Greenland north of 74°N is 161 and 194, respectively. Five different types of high arctic distribution are recognized in Greenland.
 A classification of the vegetation based on detailed description of the vegetation and few analyses in Northwest, North, and Northeast Greenland is given. Two vegetation maps (scale c. 1:2.380.000) based on NOAA-satellite images showing the degree of plant cover in eastern North Greenland and Northeast Greenland, north of 75°N lat., are presented.

Patterns of growth and reproduction in a perennial tundra forb (Geum rossii): effects of clone area and neighborhood

The relationships of clone area and neighborhood to ramet size, reproductive effort, and spatial distribution within Geum rossii clones were studied in an alpine ecosystem on the Beartooth Plateau, Montana. Clones growing on an early seral site in relative isolation were compared to clones on a late seral site within dense, heterogeneous neighborhoods. Individual clones of G. rossii required a minimum clone area of about 200 cm2 before maximum ramet size and reproductive effort were achieved. Mean ramet size and reproductive effort were fairly constant among clones larger than 200 cm2 on both the early and later seral sites. Within clones the size and reproductive effort of ramets were positively related. Pattern analysis revealed that ramets became more widely and irregularly spaced as clone area increased on the early seral site. This may have been a geometric function of an increase in the space required as clones aged and became larger. On the late seral site, clones were characterized by ramets that were widely and erratically spaced, that had low leaf numbers and mass, and that had low reproductive effort. For clones of comparable area on the early seral site, ramets were more closely and uniformly spaced, and leaf number, mass, and reproduction per ramet were higher. Conservative patterns of growth and reproduction make G. rossii well suited to dominate in dense, heterogeneous neighborhoods of late seral sites and to colonize mineral soils of early seral sites. Similar to other clonal species, site characteristics and the type of neighborhood determine the trade-off between the physical occupation of space and the allocation to ramet growth and reproduction in G. rossii. Key words: Geum rossii, alpine, reproductive effort, growth, clone area, pattern analysis, succession, neighborhood.

Alpine Seedling Establishment: The Influence of Disturbance Type

The effects of disturbance type on seedling environment and establishment of alpine species with different physiological and life history traits were examined during a 2—yr study on the Beartooth Plateau in southwestern Montana, USA. We compared soil temperatures, water potentials, and nutrients on mineral soils of a gravel borrow area with those on highly organic soils of a Geum turf area. Seedling emergence, growth, and survival of six seeded species (Geum rossii, Artemisia scopulorum, Potentilla diversifolia, Sibbaldia procumbens, Deschampsia cespitosa, and Festuca idahoensis) and emergence and survival of five unseeded species (Draba crassifolia, Draba incerta, Cerastium arvense, Arenaria rubella, and Androsace septentrionalis) were evaluated on both areas. The effects of N and P nutrient addition and surface organic mulch on the soil environment and seedling establishment were evaluated on the borrow area, while differences between uncleared turf and turf cleared of vegetation were compared on the Geum turf area. Plots cleared of vegetation on the Geum turf area had higher levels of soil N (NO3—) and P than uncleared turf and both higher levels of N (NO3— + NH4+) and P and higher soil temperatures (surface, 5, and 15 cm depths) than fertilized or not—fertilized borrow area treatments. Fertilization increased N and P on borrow area soils, but after 2 yr N had decreased significantly. Soil water potentials (5 and 15 cm depths) did not differ between cleared plots on the Geum turf area or any of the borrow area treatments and were never low enough to cause plant stress. Vegetated Geum turf had significantly lower water potentials than cleared plots, especially late in the growing season. Mulch had no effect on soil water potential or nutrients on the borrow area and increased soil temperatures only on clear days during the first growing season. Wind removed or redistributed the mulch over time, thus decreasing potential effects. Seedling emergence was highly dependent on soil surface stabilization and reflected species life history traits. Growth of seedlings was slow, and varied among species and treatments: 0.005—0.04 and 0.02—0.20 g total mass after the first and second growing seasons, respectively. Significantly higher total seedling mass was observed on cleared Geum turf plots than on any of the borrow area treatments, and on fertilized than on not—fertilized plots on the borrow area. Seedling mortality of most species was much lower than previously found for alpine ecosystems, rarely exceeding 50% even after 2 yr. On the borrow area mulch increased survival, probably through microenvironmental amelioration. The nutrient pulse from fertilization mortality of several species, presumably by creating plant nutrient demands in excess of availability during year 2. Both disturbance characteristics and species life history and physiological traits affected seddling establishment. Pretreatment soil properties of the two disturbance types had the greatest effects on soil temperatures and nutrients and, consequently, on seedling growth and survival. Soil surface characteristics had the largest effects on seedling emergence; surface stabilization was essential for holding both soil and seed in place. Single species responses varied in magnitude but were similar on both disturbance types. In general, there were larger differences among species in emergence and growth than in survival. Thus, successful seedling establishment on different alpine disturbance types may depend more on obtaining the necessary conditions for seedling emergence and on species interactions than on the ability of seedlings to survive different environmental conditions.

Pollen morphology of the Rosaceae of western Canada. III. Geum

Pollen grains of eight species of Geum (Rosaceae) from western Canada were studied in the light microscope and the scanning electron microscope. The taxa included Geum aleppicum, Geum calthifolium, Geum glaciale, Geum macrophyllum, Geum rivale, Geum rossii, Geum schofieldii, and Geum triflorum. All taxa produce pollen grains in monads that are isopolar, radially symmetrical, and predominantly tricolporate. Tetracolporate grains occur especially in Geum rossii and Geum calthifolium. Grains are subspheroidal to subprolate with a circular to subtriangular amb. All taxa exhibit a well-developed chambered aperture formed by overarching pore flaps. Flaps extend over the aperture but do not join to form an equatorial bridge. The chamber of Geum schofieldii is distinct and complex, often extending equatorially along a sinuous path to the adjacent aperture. Exine is tectate, microperforate, with a thin nexine. Sculpturing is striate or occasionally rugulate and consists of ridges and valleys with microperforations on valley floors. Ridges and valleys are oriented predominantly parallel to the colpus but occasionally curve or loop near the poles. Sculpturing of Geum schofieldii pollen, is predominantly striate but exhibits a unique verrucate to rugulate pattern along the equator caused by elaboration of the sexine. Polar diameter varies from ca. 20 μm in Geum macrophyllum to 33 μm in Geum schofieldii. The distinctness of Geum schofieldii pollen supports specific status.

Natural Reestablishment of Mycorrhizae in Disturbed Alpine Ecosystems

Vesicular-arbuscular mycorrhizal fungi were surveyed in several successional areas of the Beartooth Mountains in Montana. Roots were examined for percentage of mycorrhizal infection, and spores were counted in rhizosphere soils from undisturbed, - 25-yr-old seral, and 3- and 7-yr-old revegetated areas in 1983 and 1984. The three most abundant grasses of early seral areas, Deschampsia caespitosa, Agropyron trachycaulum, and Poa alpina, showed similar patterns: spore counts and percent infection of these species were generally higher in undisturbed than seral and revegetated areas in 1983, but in 1984 the spore numbers and infection were similar because the values dropped in undisturbed areas and increased in the other areas. Patterns of mycorrhizal infection varied for the other species, and Geum rossii, a late seral dominant, was heavily colonized by an unidentified nonendogonaceous fungus. Plant colonization is slow in the alpine, but once plants are established, mycorrhizal fungi apparently colonize quickly. Even the 3-yr-old revegetated area had infection equal to some of the undisturbed areas. However, only a single mycorrhizal fungal species was obtained from the revegetated areas, in contrast to more than 11 species from older areas.

Soil Temperature Effects on Root Respiration and the Ecology of Alpine and Subalpine Plants

Root respiration rates of Geum rossii (R. Br.) Ser. of G. triflorum Pursh, and of populations of Achillea millefolium L. from elevations of 2,400-3,220 m were compared at 4, 10, 18, and 25 C to determine whether soil temperature is important in controlling distribution of plants relative to alpine timberlines. Respiration was measured as a function of oxygen uptake by detached roots and was determined with an oxygen electrode. Comparisons of rates of roots and caudex tissue from mature plants collected in the field before and after 3 wk of growth in cold (4-10 C) or warm (15-25 C) soils and again following reversal of conditions showed that the alpine endemic G. rossii maintained higher rates than the subalpine G. triflorum; "alpine" populations of Achillea likewise had higher rates than populations from more subalpine habitats. Aerial conditions for all plants were about the same. Similar results were obtained in comparing respiration rates of 14-day-old Achillea seedlings germinated and grown at 26 C for 20 h and 10 C for 4 h, with a 16-h photoperiod daily. No differences were observed, however, between seedlings of the two Geum species, apparently due to a strong selection for heat-resistant individuals as indicated by the differences in seedling mortality. The results suggest that there are inherent tendencies for alpine plants to have higher root respiration rates than subalpine plants, which could make them more competitive under alpine conditions but could produce a wasteful metabolic rate in the warmer conditions of the subalpine. Estimations of root and shoot growth support our conclusion that soil temperatures could be an important factor in determining plant distribution patterns about alpine timberlines.

Water Potential Components, Stomatal Function, and Liquid Phase Water Transport Resistances of Four Arctic and Alpine Species in Relation to Moisture Stress

AbstractTranspiration measurements of two alpine tundra species, Deschampsia caespitosa and Geum rossii, and two arctic tundra species, Dupontia fischeri and Carex aquatilis, were conducted under varying atmospheric and soil moisture stress regimes to determine if the stomatal response to water stress may play a role in the local distributions of these species. Under low soil moisture stress, stomata of the species restricted typically to wet meadow areas, Deschampsia and Dupontia, did not exhibit closure until leaf water potential declined. However, when soil moisture stress was low and atmospheric stress increased, Geum and particularly Carex exhibited partial stomatal closure before leaf water potential dropped, suggesting a direct response of the stomata to the vapor pressure gradient between the leaf and the atmosphere. Lower liquid phase water transport resistance from the soil to the leaves may also reduce the development of leaf moisture stress in Geum. Furthermore, Geum and possibly Carex appeared to undergo less of a loss of leaf turgor when leaf water potential decreased. This response may serve to maintain leaf cell turgor and to abate the reduction in leaf enlargement.

Water Relations of Selected Plant Species in the Alpine Tundra, Colorado

The purpose of this study was to measure some aspects of the water relations of selected plant species in the alpine tundra, Colarado, in order to assess the possible role of water limitation on primary production. Leaf water potentials were measured in Kobresia myosuroides, Geum rossii, Bistorta bistortoides, Deschampsia caespitosa, and Caltha leptosepela. Leaf resistances to water loss were measured in Bistorta and Caltha. Measurements were made at dawn and midday throughout the season and several times through selected days in plants along a moisture gradient. Leaf resistance was related to leaf water potential, light, and temperature. Leaf water potentials decreased throughout the season and were higher on the wetter site. Minimum water potentials of the species in the order listed above were —40, —23, —17, —31, and —17 bars. Minimum leaf resistances of Bistorta and Caltha were 0.8 and 1.6 s.cm—1, respectively, and were lower on the wetter site. Both Bistorta and Caltha on the wet meadow showed partial midday stomatal closure, but Bistorta on the dry meadow did not At —16 bars leaf resistance increased abruptly in Caltha, but was still low in Bistorta. Leaf resistances were low at incident solar radiation levels of 0.2 ly ° min—1 and at temperatures near 20°C. Leaf resistances increased with temperatures below 15°C. Root resistances for Bistorta were 0.9 x 104 s ° cm—1 ° bar—1 at the dry site and 0.8 x 104 at the wet site, and for Caltha were 0.6 x 104 s ° cm—1 ° bar—1 at the wet site. The changing daily pattern of leaf water potential and leaf resistance is shown to be related to the diurnal environmental pattern, to root resistances, and to the relationships between leaf resistance and leaf water potential and between leaf water potential and leaf relative saturation deficit.