Low-elevation Plants Research Articles

An investigation into the potential for upward range expansion in high-montane species on the roof of the world.

Climate warming is occurring in high-mountain areas at a faster rate than the global average. To escape the increasing temperatures, alpine species may shift in distribution upwards, threatening cold-adapted nival plant specialists. However, little is known about the success of seedling emergence and establishment at high altitudes outside the current range, particularly in the highest mountain areas of the Himalayas. We selected four native alpine species occurring around 4000 m a.s.l. and sowed seeds at the natural growing site (GS), at a high elevation site (HS; 5000 m a.s.l.) and at high elevation with soil from the growing site (HS-S) in the Khumbu Valley, north-eastern Nepal. We monitored seedling emergence and establishment for two consecutive years. Seedling emergence and establishment varied between species. Emergence was similar between GS and HS and improved at HS-S. Establishment was low at high elevations with all but one species having high mortality after winter. Seedling emergence of low elevation plants is possible at high elevations in the Everest region, indicating species may be able to shift their distribution range upwards. However, successful establishment may be limited by the soil and high winter mortality at high elevations, although not in all species. Climate warming will potentially lead to upward migration of some Himalayan plant species, leading to altered community composition in high-mountain areas.

Effects of elevation on growth, photosynthetic and Ni-accumulation responses in Bornmuellera emarginata (Brassicaeae)

Bornmuellera emarginata is a Balkan Ni-hyperaccumulator indicated as a promising candidate for agromining practices. Here, two elevation-contrasting accessions (250 m, Low Elevation plants LE, and at 1600 m, High Elevation plants, HE) were compared in terms of growth, photosynthetic activity, and Ni accumulation in controlled conditions to assess possible differences exploitable in practical applications. After two months of pot cultivation on garden and serpentine soil, plant biomass, gas exchanges and Ni concentrations were evaluated. A hydroponic trial with increasing NiSO4 concentration was performed to evaluate Ni tolerance and accumulation.Plants grown on serpentine soil showed reduced biomass as compared to those from garden soil, without any difference between LE and HE. In both accessions, growth in serpentine soil resulted in photochemical/biochemical limitations and reduction in stomatal conductance, especially in LE. HE showed low stomatal conductance in all the conditions, despite a greater stomatal density. Shoot Ni accumulation was higher in HE (∼1600 µg Ni g−1 d.w. and 1200 µg Ni g−1 d.w. in HE and LE respectively), thus resulting in a significantly higher metal content per plant in respect to LE (∼120 and ∼85 µg plant−1 in HE and LE respectively). In hydroponics, HE possessed higher Ni tolerance and accumulation in respect to LE.In conclusion underlying the higher shoot metal amount of HE, Ni tolerance seemed to play a pivotal role, overtaking possible negative effects of reduced transpiration rates compared to LE. Our results point to the opportunity of exploring and exploiting the variation in accumulation level among B. emarginata accessions for the implementation of environmental restoration and metal cropping practices.

Drivers of strong isolation and small effective population size at a leading range edge of a widespread plant

Climate change has influenced species distributions worldwide with upward elevational shifts observed in many systems. Leading range edge populations, like those at upper elevation limits, are crucial for climate change responses but can exhibit low genetic diversity due to founder effects, isolation, or limited outbreeding. These factors can hamper local adaptation at range limits. Using the widespread herb, Argentina anserina, we measured ecological attributes (population density on the landscape, area of population occupancy, and plant and flower density) spanning a 1000 m elevation gradient, with high elevation populations at the range limit. We measured vegetative clonal potential in the greenhouse for populations spanning the gradient. We combined these data with a ddRAD-seq dataset to test the hypotheses that high elevation populations would exhibit ecological and genomic signatures of leading range edge populations. We found that population density on the landscape declined towards the high elevation limit, as is expected towards range edges. However, plant density was elevated within edge populations. In the greenhouse, high elevation plants exhibited stronger clonal potential than low elevation plants, likely explaining increased plant density in the field. Phylogeographic analysis supported more recent colonization of high elevation populations which were also more genetically isolated, had more extreme heterozygote excess and had smaller effective population size than low. Results support that colonization of high elevations was likely accompanied by increased asexuality, contributing to a decline in effective population size. Despite high plant density in leading edge populations, their small effective size, isolation and clonality could constrain adaptive potential.

Altitudinal differentiation in the leaf wax-mediated flowering bud protection against frost in a perennial Arabidopsis.

An altitudinal gradient of leaf water repellency is often observed between and within species. In a previous study of Arabidopsis halleri, cauline leaves (stem leaves that wrap flowering buds) showed higher water repellency in exposed semi-alpine plants than in understory low-elevation plants. Here, we examined altitudinal variations in the cuticular wax content of the leaf surface and experimentally evaluated the role of high water repellency of cauline leaves. Leaf cuticular wax was analysed using comprehensive two-dimensional gas chromatography (GC)-mass spectrometry and a GC-flame ionisation detector. Young flowering buds wrapped by cauline leaves were exposed to freezing temperatures with or without water, and frost damage to the flowering buds was compared between plants from semi-alpine and low-elevation habitats. Higher amounts of C29, C31, and C33 alkanes were observed in the cauline leaves of semi-alpine plants than in those of low-elevation plants. In the freezing experiment, water application increased damage to the flowering buds of low-elevation plants, and the extent of damage to the flowering buds was lower in semi-alpine plants than in low-elevation plants when water was applied to the plant surface. Genetic variations in the amounts of alkanes on the leaf surface depending on the altitude occurred specifically in cauline leaves. Our results indicate that the water repellency of cauline leaves presumably minimises frost damage to flowering buds at high altitudes.

Growth and reproductive responses of Polygonum hydropiper populations to elevational difference associated with flooding

Elevation can greatly affect both intensity and duration of flooding in riparian areas, and may thus affect the performance of plants distributed therein. However, few studies have examined the performance of riparian plants over elevation difference.This study compared growth and reproductive traits of populations of the riparian species Polygonum hydropiper distributed at low and high elevations of 10 different riparian locations in the hydro-fluctuation belt of the Three Gorges Reservoir Region, China.Both the location and the interaction between location and elevation had significant effects on almost all growth and reproduction traits of P. hydropiper, suggesting that the effects of elevation varied greatly among different locations. Across all locations, high-elevation plants had significantly higher total biomass, stem biomass, root biomass, and plant height than low-elevation plants. Correspondingly, high-elevation plants also had significantly higher stem starch concentrations. In comparison, low-elevation plants had significantly lower biomass, shorter height, and thinner leaves; while they had significantly higher reproductive allocation, as well as faster germination and higher germination rate at a number of locations. Therefore, low energy consumption and high reproductive capacity could be a survival adaption of low-elevation plants to frequent and deep flooding.Local conditions and/or flooding might impose strong selection pressure on P. hydropiper, thus resulting in intra-specific differentiation. Across all locations, low- and high-elevation populations exhibit different growth and reproduction responses to different flooding regimes.

Do soil biota influence the outcome of novel interactions between plant competitors?

1. Species are shifting their ranges, for example to higher elevations, in response to climate change. Different plant species and soil microbiota will likely shift their ranges at different rates, giving rise to novel communities of plants and soil organisms. However, the ecological consequences of such novel plant-soil interactions are poorly understood. We experimentally simulated scenarios for novel interactions arising between high- and low elevation plants and soil biota following asynchronous climate change range shifts, asking to what extent the ability of plants to coexist depends on the origin of the soil biota. 2. In a greenhouse experiment, we grew pairs of low- (Poa trivialis and Plantago lanceolata) and high- (Poa alpina and Plantago alpina) elevation plant species alone and against a density gradient of con- or heterospecific neighbours. Plants grew on sterilized field soil that was inoculated with a soil community sampled from either low- or high elevation in the western Swiss Alps. We used the experiment to parameterize competition models, from which we predicted the population-level outcomes of competition in the presence of the different soil biota. 3. In the absence of neighbours, three of the four species produced more biomass with the low elevation soil biota. As a result of generally similar responses across plant species, soil biota tended not to affect plant interaction outcomes, with the low elevation species generally predicted to competitively exclude high elevation species irrespective of the soil biota origin. However, the low elevation grass Poa trivialis was only able to invade communities of Poa alpina in the presence of a low elevation soil biota. This suggests that, at least in some cases, the outcome of novel competitive interactions between plants following climate change will depend on whether shifts in the distribution of plant and soil organisms are asynchronous. 4. Synthesis. Our results indicate that the changing soil communities that plants encounter during range expansion can influence plant performance. However, this is only likely to alter expectations for the ability of plants to coexist following climate change if plant species respond differently to the change in the soil community.

High-elevation plants have reduced plasticity in flowering time in response to warming compared to low-elevation congeners

Global warming has caused shifts in the flowering time of many plant species. In alpine regions the temperature rise has been especially pronounced and together with decreasing winter precipitation has led to earlier snowmelt. The close association between time of snowmelt and plant growth at high elevations makes climate change for alpine plants particularly threatening. Here we transplanted eleven congeneric pairs of high- and low-elevation herbaceous species to common gardens differing c. 800m in elevation, and c. 4°C in mean growing season temperature to test whether reproductive phenologies of high- and low-elevation plants differ in their respective responses to temperature. Results indicate that high-elevation plants were less plastic in response to transplantation than their low-elevation congeners as the onsets of phenophases on average shifted 7days less than in low-elevation plants. Plasticity of phenophase durations was overall weaker than that of phenophase onsets, and slightly stronger in high-elevation species compared to low-elevation congeners. We suggest that weaker plasticity in the onsets of early stages of reproductive phenology of high-elevation plants is related to spring frost, which constitutes a strong selective agent against early loss of winter hardiness. Some of the plastic responses of both low- and high-elevation species might potentially be adaptive under predicted climate change. However, the observed plasticity can be largely explained as a passive response to temperature and not as the result of natural selection in heterogeneous environments. The strong temperature-sensitivity of low-elevation species might promote their upward range expansion, but only to a certain threshold after which it becomes limited by the short growing season.

Species specific and environment induced variation of δ(13)C and δ(15)N in alpine plants.

Stable carbon and nitrogen isotope signals in plant tissues integrate plant-environment interactions over long periods. In this study, we hypothesized that humid alpine life conditions are narrowing the scope for significant deviations from common carbon, water and nitrogen relations as captured by stable isotope signals. We explored the variation in δ13C and δ15N in 32 plant species from tissue type to ecosystem scale across a suite of locations at c. Two thousand five hundred meter elevation in the Swiss Alps. Foliar δ13C and δ15N varied among species by about 3–4‰ and 7–8‰ respectively. However, there was no overall difference in means of δ13C and δ15N for species sampled in different plant communities or when bulk plant dry matter harvests of different plant communities were compared. δ13C was found to be highly species specific, so that the ranking among species was mostly maintained across 11 habitats. However, δ15N varied significantly from place to place in all species (a range of 2.7‰) except in Fabaceae (Trifolium alpinum) and Juncaceae (Luzula lutea). There was also a substantial variation among individuals of the same species collected next to each other. No difference was found in foliar δ15N of non-legumes, which were either collected next to or away from the most common legume, T. alpinum. δ15N data place Cyperaceae and Juncaceae, just like Fabaceae, in a low discrimination category, well separated from other families. Soil δ15N was higher than in plants and increased with soil depth. The results indicate a high functional diversity in alpine plants that is similar to that reported for low elevation plants. We conclude that the surprisingly high variation in δ13C and δ15N signals in the studied high elevation plants is largely species specific (genetic) and insensitive to obvious environmental cues.

Plant population differentiation and climate change: responses of grassland species along an elevational gradient

Mountain ecosystems are particularly susceptible to climate change. Characterizing intraspecific variation of alpine plants along elevational gradients is crucial for estimating their vulnerability to predicted changes. Environmental conditions vary with elevation, which might influence plastic responses and affect selection pressures that lead to local adaptation. Thus, local adaptation and phenotypic plasticity among low and high elevation plant populations in response to climate, soil and other factors associated with elevational gradients might underlie different responses of these populations to climate warming. Using a transplant experiment along an elevational gradient, we investigated reproductive phenology, growth and reproduction of the nutrient-poor grassland species Ranunculus bulbosus, Trifolium montanum and Briza media. Seeds were collected from low and high elevation source populations across the Swiss Alps and grown in nine common gardens at three different elevations with two different soil depths. Despite genetic differentiation in some traits, the results revealed no indication of local adaptation to the elevation of population origin. Reproductive phenology was advanced at lower elevation in low and high elevation populations of all three species. Growth and reproduction of T. montanum and B. media were hardly affected by garden elevation and soil depth. In R. bulbosus, however, growth decreased and reproductive investment increased at higher elevation. Furthermore, soil depth influenced growth and reproduction of low elevation R. bulbosus populations. We found no evidence for local adaptation to elevation of origin and hardly any differences in the responses of low and high elevation populations. However, the consistent advanced reproductive phenology observed in all three species shows that they have the potential to plastically respond to environmental variation. We conclude that populations might not be forced to migrate to higher elevations as a consequence of climate warming, as plasticity will buffer the detrimental effects of climate change in the three investigated nutrient-poor grassland species.

Cloud immersion: an important water source for spruce and fir saplings in the southern Appalachian Mountains

Cloud immersion can provide a potentially important moisture subsidy to plants in areas of frequent fog including the threatened spruce-fir communities of the southern Appalachian Mountains (USA). These mountaintop communities grow only above ~1,500 m elevation, harbor the endemic Abies fraseri, and have been proposed to exist because of frequent cloud immersion. While several studies have demonstrated the importance of cloud immersion to plant water balance, no study has evaluated the proportion of plant water derived from cloud moisture in this ecosystem. Using the isotopic mixing model, IsoSource, we analyzed the isotopic composition of hydrogen and oxygen for water extracted from ground water, deep soil, shallow soil, fog, and plant xylem at the upper and lower elevational limits both in May (beginning of the growing season) and October (end of the growing season). Cloud-immersion water contributed up to 31% of plant water at the upper elevation sites in May. High-elevation plants of both species also experienced greater cloud immersion and had greater cloud water absorption (14-31%) compared to low-elevation plants (4-17%). Greater cloud water uptake occurred in May compared to October, despite similar rainfall and cloud-immersion frequencies. These results demonstrate the important water subsidy that cloud-immersion water can provide. With a warming climate leading potentially to increases in the ceiling of the cloud base and, thus, less frequent cloud immersion, persistence of these relic mountaintop forests may depend on the magnitude of these changes and the compensating capabilities of other water sources.

Herbivory prevents positive responses of lowland plants to warmer and more fertile conditions at high altitudes

Summary Warm‐adapted low elevation plants are expected to exhibit considerable range shifts to higher altitudes and latitudes as a result of climate warming and increased nutrient loads. However, empirical studies show that the magnitude and direction of plant responses are highly species‐ and site‐specific, suggesting that several additional drivers interact with warmer climate. We experimentally tested the interactive effects of climate warming, mammalian herbivory and soil fertility on low elevation plants. Seedlings of three warm‐adapted lowland forbs (Epilobium angustifolium, Silene dioica and Solidago virgaurea) were transplanted to an open tundra site with native mountain tundra vegetation, and the effects of full factorial combinations of herbivore exclosures, warming and fertilization on transplant survival, growth and flowering were studied for two growing seasons. We also investigated the response of native vegetation biomass to the same treatments and compared it with the responses of transplanted lowland forbs. Effects of both warming and fertilization on the transplanted lowland forbs strongly hinged on herbivore exclusion, resulting in 2–13‐fold increase in biomass in warmed and fertilized plots without herbivores compared with warmed and fertilized plots with herbivores present, the magnitude depending on the species. While warm‐adapted transplants benefited from warming, the native tundra plant community biomass did not respond to warming treatment. Our results show that grazing limits the growth of transplants under warmer and more productive conditions, indicating that the expansion of lowland plant species to higher altitudes with warming may be hampered by mammalian herbivory. Furthermore, our results also suggest that migration of warm‐adapted species into lightly grazed high‐altitude tundra ecosystems might transform these communities to be more responsive to warmer climate and nutrient loads. Studies that do not consider species' upward shifts from lower altitudes might thus have underestimated vegetation responses to global warming, as well as the potential of herbivory to influence these responses.

Shifts in species richness, herbivore specialization, and plant resistance along elevation gradients

Environmental gradients have been postulated to generate patterns of diversity and diet specialization, in which more stable environments, such as tropical regions, should promote higher diversity and specialization. Using field sampling and phylogenetic analyses of butterfly fauna over an entire alpine region, we show that butterfly specialization (measured as the mean phylogenetic distance between utilized host plants) decreases at higher elevations, alongside a decreasing gradient of plant diversity. Consistent with current hypotheses on the relationship between biodiversity and the strength of species interactions, we experimentally show that a higher level of generalization at high elevations is associated with lower levels of plant resistance: across 16 pairs of plant species, low-elevation plants were more resistant vis-à-vis their congeneric alpine relatives. Thus, the links between diversity, herbivore diet specialization, and plant resistance along an elevation gradient suggest a causal relationship analogous to that hypothesized along latitudinal gradients.

Demographic, developmental and life-history variation across altitude in Erysimum capitatum

1. Natural variation in life history provides the opportunity to examine its correlated population performance. Alpine systems are considered to be vulnerable to climate change as high-altitude conditions are predicted to become more similar to those at low altitude. Comparing natural populations that exhibit variation in life history across altitude can provide information on how life history may influence the demography of alpine plants under a range of altitudinally or climatically variable conditions. 2. We compared the abundance, demography, life history and morphological development of Erysimum capitatum populations in alpine and lower-altitude habitats in the Colorado Rocky Mountains. 3. Mortality of all life stages was higher at lower elevation than in alpine sites, and low-elevation plants reproduced more quickly and expressed a semelparous life history more frequently than did alpine plants. Significant variation in post-reproductive survival, i.e. the opportunity for iteroparity, was also found across regions. 4. Several life stages contributed comparably to projected population growth in high-altitude, iteroparous populations, whereas low-elevation semelparous populations depended primarily on seedling recruitment and rapid reproductive maturation for population maintenance. Populations with intermediate levels of iteroparity differed from each other in their demography, suggesting that transitional states between iteroparity and semelparity are unpredictable. 5. Morphological development also differed between iteroparous and semelparous plants, with iteroparous plants producing more vegetative rosettes and maintaining those rosettes in a vegetative state more frequently than semelparous plants. Sites with lower soil water content were more semelparous. 6. Synthesis. These combined results suggest that changes in developmental rates and morphology may promote changes in fundamental life history. Altitudinal variation in morphology and parity is strongly associated with demographic variation across altitude, indicating that plastic or evolutionary changes in these traits would influence population performance across altitudinally or climatically variable conditions.

Lower selfing rate at higher altitudes in the alpine plant Eritrichium nanum (Boraginaceae)

A general hypothesis on mating patterns in alpine plants states that self-fertilization should increase with increasing altitude as a result of pollinator limitation at higher altitudes. However, realized selfing rates under natural conditions, as based on genetic progeny analysis, have not yet been determined for any alpine species across altitude. We therefore assessed the realized selfing rates in about 100 open-pollinated families of the high-alpine cushion plant Eritrichium nanum, sampled along an altitudinal gradient in the Swiss Alps, by using progeny analysis based on six microsatellites. In marked contrast to the general hypothesis, realized selfing rates in E. nanum significantly decreased with increasing altitude, and only progenies from low altitudes were predominantly selfed. However, the higher selfing rates of individuals at lower altitudes could have been caused by unfavorable weather conditions during early growing season when low-elevation plants flowered. In summary, our results on selfing rates in an alpine plant across altitude as well as the results of other studies using experimental hand-pollinations and/or population genetic methods generally do not support the expectation of higher selfing rates at higher altitudes. We therefore ask for further critical examination of realized mating systems in alpine plants.

Environmental v. genetically driven variation in ecophysiological traits of Nothofagus pumilio from contrasting elevations

Nothofagus pumilio (Poepp. et Endl.) Krasser is a broadleaved deciduous tree that dominates high-elevation forests in the southern Andes. We evaluated the degree to which differences in stomatal density and physiological traits (net assimilation, conductance and water use efficiency) were related to environmental and genetic influences with elevation by comparing plants growing under field and common garden conditions. Low-elevation leaves under field conditions had fewer stomata, although this pattern was not maintained in the common garden. Assimilation rates were >40% higher for high-elevation plants in the field, and 18% higher in the common garden, than those for low-elevation plants. In addition, under field conditions high-elevation plants tended to have higher stomatal conductance and lower instantaneous water use efficiency than did low-elevation plants; however, these differences were not significant in the common garden. Thus, assimilation seems to be under genetic control whereas ecophysiological traits related to the use of water appear to be more responsive to environmental cues. Our results suggest that plants growing along elevational gradients may show complex ecophysiological patterns. These patterns may be acquired by genetically driven responses to conditions that are fixed throughout the life span of individuals, such as soil nutrients. Also plastic adjustments may favour opportunistic use of available water during the dry season, particularly under Mediterranean-type climate regimes with summer drought.

Behaviour, habitat associations, and intrasexual differences of female Stone’s sheep

Stone’s sheep ( Ovis dalli stonei Allen, 1897) in northern British Columbia segregate sexually during most of the year, and intrasexually between maternal and nonmaternal females during spring and early summer. Our objective was to quantify intrasexual habitat use of female Stone’s sheep relative to maternal status using measures of behaviour and habitat use. We reviewed three hypotheses of intersexual segregation (predation-risk, forage-selection, and activity-budget hypotheses) to determine if they also explained intrasexual segregation of female Stone’s sheep. Female Stone’s sheep spent the majority of their active time foraging. Nursery groups spent shorter durations of time active, more time active in solid rock escape features, and less time active in shrub habitat than nonmaternal groups. The best predictive model describing intrasexual differences incorporated distance to nearest escape feature and size of nearest escape feature. Regardless of maternal status, female Stone’s sheep used low-elevation plant communities early in the growing season that were characterized by more shrub species and increased cover. As the growing season progressed, they tracked a phenological stage, moving up in elevation and associating with communities that contained increasing amounts of moss and lichen cover. The patterns in behaviour, habitat use, and vegetation associations between intrasexual groups of Stone’s sheep were best characterized by the predation-risk hypothesis.

A global survey of carbon isotope discrimination in plants from high altitude

Carbon 13/12 isotope ratios have been determined from leaves of a hundred C3 plant species (or ecotypes) from all major mountain ranges of the globe, avoiding drought stressed areas. A general increase in 13C content was found with increasing altitude, i.e. overall discrimination against the heavy isotope is reduced at high elevation. The steepest decline of discrimination is observed in taxa typically ranging to highest elevations (e.g. the genus Ranunculus). Mean δ 13C for all samples collected between 2500 and 5600 m altitude is-26.15‰ compared to the lowland average of-28.80‰ (P<0.001). Forbs from highest elevations reach-24‰. According to theory of 13C discrimination this indicates decreasing relative limitation of carbon uptake by carboxylation. In other words, we estimate that the ratio of internal to external partial pressure of CO2 (p i /p a )in leaves of high elevation plants is lower than in leaves of low altitude. These results confirm recent gas exchange analyses in high and low elevation plants.

Spatial patterns of atmospheric pollen transport in a montane region

Annual pollen deposition (pollen cm −2 yr −1) was sampled for 6 yr in the southern Sierra Nevada, the Owens Valley, and the Inyo Mountains of central California. Spatial pollen distributions were examined for anemophilous plants which are limited to growth sites (1) at high elevations on one or both mountain ranges, (2) on lower mountain slopes, and (3) on the Owens Valley floor, Pollen deposition values for high- and low-elevation plants changed by a factor of 5 to 10 between adjacent sample sites which straddle boundaries of the plant communities in which the source plants grow. Pollen deposition values were high and variable within communities in which the species grew. Pollen deposition beyond source populations was low and uniform despite great differences in distance of sites from pollen sources. The step function that seems to characterize pollen distribution patterns implies that pollen from distant populations may be of little value in interpreting vegetation stability and change reflected by fossil pollen stratigraphy. The physical isolation of pollen embedded in the local mountain-valley wind system from that in the prevailing westerlies may explain part of the spatial distribution of the pollen.

Effects of Moisture and Temperature on Germination of Idaho Fescue

Germination response to varying temperatures and water stress levels during a 30-day incubation period was observed in 4 eastern Oregon collections of Festuca iduhoensis Elmer. Seeds were selected from the following habitat types: Artemisia tridenta associate professor. Eastern Oregon Agricultural Research Center. Star Rt. I-4.5 I Hwy. 205, Burns. Oregon 97720; and regional forest ecologist, Regional Office. U.S. Forest Service, Fed. Office Building, 324-25th Street, Ogden. Utah 84401. This research was a cooperative effort and jointly supported by the USDA, Agricultural Research Service and Eastern Oregon Agricultural Research Center, Squaw Butte Station, Agricultural Experiment Station. Tech. Paper NO. 7332. Oregon Agricultural Experiment Station. Manuscript accepted December 19, 1984. JOURNAL OF RANGE MANAGEMENT 38(4), July 1985 This research was designtd to evaluate germination response of 4 eastern Oregon seed collections of Idaho fescue to varying conditions of temperature and substrate water stress. Idaho fescue is a cool-season perennial bunchgrass indigenous to communities dominated by big sagebrush (Artemisia tridentata Nutt.) and ponderosa pine (Pinusponderosa Dougl.). Optimum germination temperatures for Idaho fescue have been reported to be between I5 to ’ C (Young et al. 1981, Stocker 1975). Materials and Methods Seed Collection and Processing Idaho fescue seeds were collected from the following habitat types: Artemisia tridentata ssp. wyomingensisl Festuca idahoensis (ARTRW/ FEID) (Doescher 1983), Artemisia tridentata ssp. vaseyana/Festuca idahoensis (ARTRV/ FEID) (Winward 1970) and Pinus ponderosal Festuca idahoensis (PIPO/ FEID) (Franklin and Dyrness 1973). One stand of each habitat type was sampled, except for the ARTRV/ FEID habitat type where seed was collected from both a high and low elevation plant community. The low elevation stand occurred on coarse pumice soils. For purposes of this discussion, this site will be referred to as the ARTRV“L’/ FEID habitat type. All habitat types were chosen in the same general geographic region (Table 1). It was assumed that ARTRW/ FEID habitat type was the most xeric, the PIP0 habitat type the most mesic and the ARTRV“L”/ FElDand ARTRV/ FEID habitat type intermediate in moisture relations. All sites had a dominant understory of Idaho fescue. Seeds of Idaho fescue were collected by hand stripping at various times during the 1980 growing season and cleaned by hand threshing and screening to remove caryopses from chaff. Seeds were stored at room temperatures. In order to standardize seed weight during experimentation, only heavy seeds were used in germination trials. Unfilled and light seeds were removed with a seed blower, with blower settings held constant for each seed lot. Abnormally developed embryos observed on a light table were not included in the germination experiments. Seeds used in experimentation were collected during seed shatter as test of seed viability with tetrazolim chloride indicated better stress germination from seeds collected during this phenological period. Seeds approximately 8 months of age were used in the germination trials. Experimental Procedure Seeds were concurrently germinated in environmental chambers under seven constant temperatures (5,10,15,20,25,30, and 35” C) and six combinations of temperature and water stress ( lS°C/O.O MPA, 15”C/-0.6MPa, 15°C/-0.9MPa,200C/0.0MPa,200C/-0.6

Vegetation on Limestone and Granite in the Mule Mountains, Arizona

Gradient analysis was employed to determine vegetation pattern in relation to environment on limestone and granite in the Mule Mountains, Cochise County, Arizona, USA, using data obtained from 175 0.1—ha (20 x 50 m) quadrats located over ranges of elevation and topographic position. Sequences of major community types from mesic to xeric positions on the mountain slopes were pygmy conifer—oak scrub, open oak woodland, and desert grassland on granite and Cercocarpus breviflorus scrub, mesic phase Chihuahuan desertscrub, and xeric phase Chihuahuan desertscrub on limestone. Calcareous bajadas (alluvial plains) southwest of the Mule Mountains support a disturbed Chihuahuan desertscrub type. An environmental scalar was developed to quantify site position along complex—gradients of elevation and topographic position. The scalar was correlated with indirect ordination axes from reciprocal averaging, principal components analysis, and Wisconsin polar ordination. Over similar ranges of elevation and topographic position, granitic sites have higher species richness, greater importance of herbaceous and arborescent species, and lower importance of shrubby species than limestone sites. Both rock types support vegetation rich in widely distributed southwestern species but the vegetation on limestone has a distinctly Chihuahuan character, while that on granite is Madrean. Investigation of species distributions indicated a modal shift toward more mesic environments on limestone as compared to granite. This shift complemented other observations which suggested more xeric conditions on limestone. The low—elevation plant communities on limestone represent the northwesternmost occurrence of the Chihuahuan Desert formation. This may be due to three factors: (1) limestone habitats are arid (as judged from observations of vegetation); (2) increased aridity favors desert species, but the local climate (particularly cool winter temperatures) selects for Chihuahuan, rather than Sonoran, species; and (3) among desert species the Chihuahuan are better adapted to calcerous soils, which occur widely in the Chihuahuan Desert.