Cercocarpus Research Articles

Cutting Propagation of ‘Coy’ Alder-leaf Mountain Mahogany

‘Coy’ alder-leaf mountain mahogany (Cercocarpus montanus) is a new cultivar developed from a species native to the western United States with potential for use in xeriscaping, rock gardens, and water-efficient landscaping. However, efficient propagation methods are not well developed for it. In this study, cutting propagation of ‘Coy’ alder-leaf mountain mahogany was investigated over 3 years to evaluate the effects of wounding method, rooting hormone, type of cuttings collected, and time for cutting collection on rooting. In May, Jul, and Sep 2020, 2021, and 2022, nondormant hardwood subterminal cuttings and/or semihardwood terminal cuttings were collected for wounding studies. Before the treatment with 3000 mg·L−1 indole-3-butyric acid (IBA) in powder, cuttings were wounded either by scraping one side (scrape) or by perpendicular cuts around the base (cut), and cuttings without additional wounding were used as the control. Similarly, subterminal and terminal cuttings of ‘Coy’ alder-leaf mountain mahogany were collected during the same time and were used for hormone treatments. Cuttings were treated with 1000 or 3000 mg·L−1 IBA in powder or 1000/500 or 3000/1500 mg·L−1 IBA/NAA (1-naphthaleneacetic acid) in solution. Wounding by cut or scrape increased the rooting percentage. In addition, most cuttings wounded by the scrape method had better rooting than those wounded with cuts. On the basis of hierarchical cluster analyses, cuttings treated with 3000 mg·L−1 IBA in powder had greater rooting than those treated with other hormones. Therefore, our research showed that successful rooting of subterminal or terminal stem cuttings of ‘Coy’ alder-leaf mountain mahogany can be achieved through wounding using scrape method and by treatment with 3000 mg·L−1 IBA in powder.

Growth, Morphological, and Biochemical Responses of Four Native Species to Salinity Stress

Native plants are of great value in landscape maintenance. Despite their importance in the landscape, the salt tolerance of most native plants has received little attention. The present research was designed to assess morphological, physiological, and biochemical responses of four Utah-native plants [Arctostaphylos uva-ursi (kinnikinnick), Cercocarpus ledifolius (curl-leaf mountain mahogany), Cercocarpus montanus ‘Coy’ (alder-leaf mountain mahogany), and Shepherdia ×utahensis ‘Torrey’ (hybrid buffaloberry)] at different salinity levels. Each species was irrigated with a nutrient solution at an electrical conductivity (EC) of 1.2 dS·m−1 (control) or saline solutions at ECs of 5.0 or 10.0 dS·m−1 for 8 weeks. The experiment was a randomized complete block design with 10 replications. At 8 weeks after the initiation of the experiment, A. uva-ursi and C. montanus ‘Coy’ had slight foliar salt damage with an average visual score of 3.7 (0 = dead, 5 = excellent with no sign of foliar salt damage) when irrigated with saline solution at an EC of 5.0 dS·m−1 and were dead at an EC of 10.0 dS·m−1. Similarly, C. ledifolius had an average visual score of 3.2 when irrigated with saline solution at an EC of 10.0 dS·m−1. However, almost no foliar salt damage was observed on S. ×utahensis ‘Torrey’ during the experimental period. In addition, the shoot dry weight of all species was reduced with elevated salinity levels in the irrigation water. Salinity stress also reduced gas exchange rates of plants and affected their mineral content. Proline accumulated in the leaves of native plants but was species-dependent. In conclusion, S. ×utahensis ‘Torrey’ was tolerant to salinity stress followed by C. ledifolius; A. uva-ursi and C. montanus ‘Coy’ were sensitive to salinity stress.

Age-Dependent Search Behavior in the Colorado Checkered Whiptail (Aspidoscelis neotesselatus)

We compared movement and space use patterns of foraging adult and juvenile Colorado checkered whiptails (Aspidoscelis neotesselatus) in pinyon pine–juniper woodland. Through focal observations, we characterized (1) movement paths as a series of step lengths and turn angles at 30-s intervals, and (2) habitat use reflected by the proportion of time spent in different vegetation types and in the open. Adults and juveniles differed in both movement and habitat use. Adults spent more time in the open and in association with mountain mahogany (Cercocarpus montanus), while juveniles were more frequently found in association with dead wood, grass, and juniper (Juniperus monosperma). Adults also moved greater distances than juveniles and made use of larger areas. Movement patterns differed between age classes, with adults having longer step lengths. Adults and juveniles also engaged in different step length–turn angle sequences. For both classes, movement characteristics differed with habitat type.

Plant performance predicted by genetic variation and environmental distance in important restoration shrub species Cercocarpus montanus

Seed transfer guidelines are used to guide the human‐mediated movement of plant propagules from collection to recipient sites and are designed to minimize the risk of introducing maladapted genotypes. The spatial scale of adaptation, however, is unknown for most species, making it difficult to assess the potential negative impacts of seed transfer. In this study, we generated seed transfer guidelines for an ecologically important shrub, alder‐leaf mountain mahogany (Cercocarpus montanus). We plant material from 24 populations of C. montanus along a latitudinal transect from the southern Rocky Mountains of New Mexico, Colorado, and Wyoming. Seeds and seedlings were sown and planted separately in common garden experimental sites representing dissimilar environments. We measured plant germination, survival, growth, and leaf morphology for three growing seasons, and found significant variation among populations. Environmental and genetic distance were useful predictors of population performance in our common garden trials, which we use to recommend broad‐scale seed transfer guidelines to minimize risk of maladaptation to restoration sites.

Paleoecological and Archaeological Investigation of the ROMO 9 Ice Patch, Rocky Mountain National Park, Colorado, USA

Rocky Mountain National Park contains a dense record of prehistoric Native American archaeological locales and biological resources, but questions remain about the past use of the Park’s ice patches by ancient humans and animals. Our survey of 30 locations in the Park revealed that the majority of ice patches are small in size and contain limited evidence of past visitation by mobile peoples, but moderate use by game. In this paper, we present new radiocarbon dates for materials documented in the recently melted forefield of the ROMO 9 ice patch, a mid-sized ice body located in alpine tundra along the Continental Divide. Dated materials include timber-sized pine trees, keratin and bone collagen from large game (bighorn sheep, elk), and a possible wooden artifact made from Mountain mahogany. Results suggest most finds date to several periods of known neoglaciation, during the mid-Holocene (c. 4150 cal BP) and the Little Ice Age (c. 115 cal BP). Our results corroborate past findings on mid-Holocene timberline in the Colorado Front Range, as well as the paucity of archaeological evidence from small ice patches in Colorado.

Lichen Checklist for the Jarbidge Wilderness Area and Adjacent Forest Service Lands in Northeastern Nevada, USA

Based on field collections made during the summers of 1987, 1988, and 1989, we report 159 species of lichens in 69 genera for the Jarbidge Wilderness Area (JWA) and adjacent Forest Service lands, located in the northern Great Basin, USA. Specimens were collected at 25 sites, distributed across the JWA along with two additional sites north of the wilderness boundary on Forest Service land. Collections were made from all available substrates, including rocks, bark, lignum, mosses, soil, and from the thalli of various saxicolous lichens. All basic growth forms were found, especially crustose and foliose species. Umbilicate species (Dermatocarpon spp., Rhizoplaca spp., and Umbilicaria spp.) were commonly found on rocks, while a limited number of fruticose species (Letharia spp. and Bryoria spp.) were found on bark and lignum substrates. A single, fruticose species was found on rocks (Pseudephebe minuscula). Saxicolous substrates supported the richest lichen communities, followed by corticolous and lignicolous substrates. Specifically, cottonwood spp., various conifer species, and curled leaf mountain mahogany were important bark and lignum substrates. Other taxa occurred on soil/bryophyte/detritus substrates with one species commonly collected on the thalli of various saxicolous lichens (i.e., Caloplaca epithallina). The JWA lichen flora is richer than other Nevada wilderness areas so far surveyed, with 33 putative new species records for the state of Nevada. Species richness and abundance in the JWA is likely due in part to the more mesic conditions found in the wilderness as well as its proximity to the more abundant and diverse lichen communities found in the Northern Rocky Mountains and the Pacific Northwest. Samples of two sensitive indicator species (Rhizoplaca melanophthalma and Letharia lupina) were analyzed to determine thallus concentrations of three potential air pollutants (sulfur, copper, and lead). All pollutant element concentrations were within background levels except for percent sulfur in two samples of Letharia lupina from Hummingbird Ridge (0.226%) and Emerald Lake (0.215%). Both sites are upper elevation (> 2700 m ASL) suggesting possible accumulation due to long-range transport of sulfur species from large urban areas in the Pacific Northwest.

Implications of genetic heterogeneity for plant translocation during ecological restoration.

Ecological restoration often requires translocating plant material from distant sites. Importing suitable plant material is important for successful establishment and persistence. Yet, published guidelines for seed transfer are available for very few species. Accurately predicting how transferred plants will perform requires multiyear and multi‐environment field trials and comprehensive follow‐up work, and is therefore infeasible given the number of species used in restoration programs. Alternative methods to predict the outcomes of seed transfer are valuable for species without published guidelines. In this study, we analyzed the genetic structure of an important shrub used in ecological restoration in the Southern Rocky Mountains called alder‐leaf mountain mahogany (Cercocarpus montanus). We sequenced DNA from 1,440 plants in 48 populations across a broad geographic range. We found that genetic heterogeneity among populations reflected the complex climate and topography across which the species is distributed. We identified temperature and precipitation variables that were useful predictors of genetic differentiation and can be used to generate seed transfer recommendations. These results will be valuable for defining management and restoration practices for mountain mahogany.

Rain‐shadow forest margins resilient to low‐severity fire and climate change but not high‐severity fire

AbstractAt semi‐arid forest margins, increasing climatic stress combined with disturbances like wildfire threatens to cause widespread forest loss. However, forest resilience is likely to vary over gradients of topoclimate and vegetation characteristics, and the influences of local climate and tree species on tree regeneration remain key uncertainties in assessing forest recovery from wildfire. We surveyed tree regeneration 9–15 yr post‐fire at 397 gridded field plots across four sites at a lower montane forest‐steppe ecotone in the eastern Sierra Nevada, California, USA, and then used statistical modeling to characterize how the probability of tree regeneration presence for different species varied along gradients of fire severity, topoclimate, and post‐fire vegetation structure and composition. Tree regeneration was absent in half the field plots, and only 19% of plots contained >250 seedlings and saplings per ha, suggesting potential for regeneration failure and forest loss. Tree regeneration composition was consistent with shifts away from Jeffrey pine (Pinus jeffreyi) and toward drought‐tolerant pinyon pine (P. monophylla) and mountain mahogany (Cercocarpus ledifolius). Tree regeneration was strongly associated with trees that survived fire indicating tree cover is crucial to buffer establishment against climatic stress. Based on projected future water balance, the likelihood of tree regeneration at these sites does not decline substantially by the end of the century. Consequently, these forests appear to be resilient to climate change under a low‐severity fire regime, but large patches of high‐severity fire are likely to shift vegetation away from forest. Our results highlight the importance of facilitation and future water balance in maintaining semi‐arid forest margins that burn at low severity while high‐severity fire threatens to convert forest to steppe or invasive grasslands.

Relative habitat- and browse-use of native desert mule deer and exotic oryx in the greater San Andres Mountains, New Mexico

Introduced oryx (Oryx gazella gazella) have expanded into the San Andres Mountains of south-central New Mexico, but little is known of concurrent habitat used by oryx and desert mule deer (Odocoileus hemionus crooki); the latter in New Mexico is a species of special concern that has declined signifi cantly since the introduction of oryx. We used fecal-pellet and browse surveys in combination with presence modeling to identify differences in relative use of habitat types, distribution, and browsing of highly palatable, highly preferred (hereafter, key) plant species during 2004 to 2006 to assess the potential for direct competition in use of resources in the San Andres Mountains. Numbers of pellet groups per transect (hereafter referred to as relative use) of oryx was greatest in sandsage (Artemisia fi lifolia) shrublands and alkali sacaton (Sporobolus airoides) grasslands, whereas mule deer-use was greatest in oak- (Quercus spp.) mountain mahogany (Cercocarpus montanus) shrublands, and pinyon- (Pinus edulis) juniper (Juniperus spp.) woodlands. Use of key mule deer browse species was low (<4.0% of current annual growth browsed) in all habitat types. Relative use of oryx accounted for 42% of the variation in browse percentages in pinyon-juniper woodlands and 58% of the variation in mesquite (Prosopis glandulosa) shrublands, whereas mule deer-use accounted for 79% of the variation in oak-mountain mahogany shrublands and 27% in pinyon-juniper woodlands. Presence models similarly indicated that deer distribution was most positively associated with oak-mountain mahogany shrublands and pinyon-juniper woodlands, while oryx distribution was most positively associated with alkali sacaton grasslands, mixed lowland scrub, and sandsage shrublands. Presence models also indicated that areas closer to roads were positively associated with presence of mule deer and oryx, as were southern aspects for oryx and higher elevations for mule deer. Relationships with roads were likely driven by other attributes (e.g., water sources, arroyos, and canyons) associated with these areas in the San Andres Mountains. Current management strategies aimed at limiting oryx numbers in woodland and shrubland habitat types located in mountainous areas of the San Andres Mountains that show highest use by mule deer should continue to aide in recovery of mule deer populations.

Resource selection by cougars: Influence of behavioral state and season

ABSTRACTAn understanding of how a predator uses the landscape can assist in developing management plans. We modeled resource selection by cougars (Puma concolor) during 2 behavioral states (moving and killing) and 2 seasons (summer and winter) with respect to landscape characteristics using locations from global positioning system (GPS)‐collared cougars in the Pryor Mountains, Montana and Wyoming, USA. Furthermore, we examined predation‐specific resource selection at 2 scales (fine and coarse). When possible, we backtracked from cache sites to kill sites and used a fine‐scale analysis to examine landscape characteristics of confirmed kills. At this fine scale, kill sites had less horizontal visibility, were more likely to be in juniper (Juniperus spp.)‐mountain mahogany (Cercocarpus ledifolius), and were less likely to be in grassland vegetation. For the coarse‐scale analysis of predation risk, we used the entire dataset of kills by buffering each cache site by 94.9 m, which was the 95% upper cut‐off point of the known distances dragged from kill sites to cache sites, thereby creating buffered cache sites that had a high probability of containing the kill site. We modeled seasonal cougar predation site selection by constructing resource selection functions for these buffered cache sites. The top model for summer predation risk consisted of vegetation class, distance to water, and slope. The top model for winter predation risk included vegetation class and elevation. These predation risk models were similar to but simpler than the resource selection models developed from the moving locations. Essentially, the behavioral state (i.e., killing vs. moving) of the cougar had little influence on resource selection, indicating that cougars are generally in hunting mode while moving through their landscape. To potentially reduce cougar predation on mule deer (Odocoileus hemionus) and bighorn sheep (Ovis canadensis) in our study area, managers can intersect the cougar predation‐risk resource selection functions with deer and sheep habitat to guide habitat modification efforts aimed at increasing horizontal visibility in risky vegetation classes. © 2016 The Wildlife Society.

Phytostabilization of mine tailings using compost-assisted direct planting: Translating greenhouse results to the field

Standard practice in reclamation of mine tailings is the emplacement of a 15 to 90cm soil/gravel/rock cap which is then hydro-seeded. In this study we investigate compost-assisted direct planting phytostabilization technology as an alternative to standard cap and plant practices. In phytostabilization the goal is to establish a vegetative cap using native plants that stabilize metals in the root zone with little to no shoot accumulation. The study site is a barren 62-hectare tailings pile characterized by extremely acidic pH as well as lead, arsenic, and zinc each exceeding 2000mgkg−1. The study objective is to evaluate whether successful greenhouse phytostabilization results are scalable to the field. In May 2010, a 0.27ha study area was established on the Iron King Mine and Humboldt Smelter Superfund (IKMHSS) site with six irrigated treatments; tailings amended with 10, 15, or 20% (w/w) compost seeded with a mix of native plants (buffalo grass, arizona fescue, quailbush, mountain mahogany, mesquite, and catclaw acacia) and controls including composted (15 and 20%) unseeded treatments and an uncomposted unseeded treatment. Canopy cover ranging from 21 to 61% developed after 41 months in the compost-amended planted treatments, a canopy cover similar to that found in the surrounding region. No plants grew on unamended tailings. Neutrophilic heterotrophic bacterial counts were 1.5 to 4 orders of magnitude higher after 41months in planted versus unamended control plots. Shoot tissue accumulation of various metal(loids) was at or below Domestic Animal Toxicity Limits, with some plant specific exceptions in treatments receiving less compost. Parameters including % canopy cover, neutrophilic heterotrophic bacteria counts, and shoot uptake of metal(loids) are promising criteria to use in evaluating reclamation success. In summary, compost amendment and seeding, guided by preliminary greenhouse studies, allowed plant establishment and sustained growth over 4years demonstrating feasibility for this phytostabilization technology.

CUTTING PROPAGATION OF LITTLE-LEAF MOUNTAIN MAHOGANY©

Superior selections of little-leaf mountain mahogany (Cercocarpus ledifolius var. intricatus) (CLI) have potential for use in water-conserving landscapes in the Intermountain region of the USA. The potential for propagating CLI by cuttings was determined by selecting specimens from a range of sources and growing conditions at different seasons and with different rooting conditions in a series of individual experiments. Exogenous auxin treatments at high (4000/2000 ppm indolebutryic acid/naphthaleneacetic acid as Dip-N-Grow®) and low (2000/1000 ppm of the same material) were also tested. Selection CLI-1 (wild source, Ephraim, Utah, Jan. 2010) rooted at 0, 33, and 42% with zero, low, and high auxin treatments. Selections CLI-2 and CLI-3 (wild source, Mt. Charleston, Nevada, May, 2010) had results of 0, 0, and 8% and 15, 28, and 52% rooting for the respective auxin treatments and selections. Selection CLI-4 (landscape source, Logan, Utah, July, 2010) had 8, 96, and 100% rooting for similar auxin treatments. Finally selections CLI-5 and CLI-6 (landscape source, Logan, Utah) and CLI-3 (container-grown stock plants) stuck in July, 2012 had 6, 2, and 85% rooting with the low rate of auxin, respectively. Overall, two selections had greater than 90% rooting while one had approximately 40% and three others less than 10%. For the three selections that did root, supplemental auxin increased the percentage of rooted cuttings from 0-15% for untreated controls to 42-100% for treated. In contrast, the three selections with poor rooting had little response to exogenous auxin at the levels used. Propagation of CLI by cuttings is feasible, though variable. The variability may be due to accession genetic differences, stock plant growing conditions, or rooting conditions.

Effects of woody vegetation on shallow soil moisture at a semiarid montane catchment

AbstractIn semiarid montane regions, spatial patterns of shallow soil moisture (0–5 cm) are expected to depend on vegetation patterns and topographic attributes. In some cases, the vegetation patterns themselves depend on the topography, which makes the interaction of soil moisture, vegetation and topography especially complex. Such is the case in portions of the Colorado Front Range where many south‐facing and north‐facing slopes are primarily vegetated by mountain mahogany (Cercocarpus montanus) shrubs and ponderosa pine (Pinus ponderosa) trees, respectively. The objectives of this paper are the following: (1) to determine how the presence of a shrub or tree affects the shallow soil moisture on these distinct hillslopes and (2) to understand the main mechanisms through which the vegetation affects the shallow soil moisture. On opposing hillslopes in the Cache la Poudre catchment, soil moisture was monitored for intercanopy, shrub canopy and tree canopy locations. Throughfall, insolation, soil texture and hydrophobicity were also measured to understand the reasons for any soil moisture differences. The results suggest that the shallow soil moisture is more distinct between the canopy and intercanopy locations on the south‐facing slope than the north‐facing slope. On the south‐facing slope, intercanopy locations are less shaded by the nearby canopy because of the shorter stature of the shrubs and the orientation of this hillslope towards the sun. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Occupancy and habitat correlates of javelinas in the southern San Andres Mountains, New Mexico

Javelinas (Pecari tajacu) are expanding their range northward in the southwestern United States, but little is known of habitat relationships in northern populations. We used occupancy modeling and maximum entropy modeling of data collected from a camera-trapping grid to investigate javelina occupancy and identify habitat correlates associated with presence in the southern San Andres Mountains of south-central New Mexico. Corrected for incomplete detection, occupancy increased from 0.036 (SE ¼ 0.035) in 2007 to 0.327 (SE ¼ 0.082) by 2011. Presence of javelinas was most strongly associated with areas in close proximity to permanent water sources; with overstory or high shrub canopies of riparian, oak–mountain mahogany, or pinyon–juniper; and with low (, 6%) slopes. Areas with P . 0.75 for javelina presence comprised only 6.7% of the San Andres landscape. Circadian patterns of behavior indicated that javelinas were primarily diurnal during colder months and nocturnal during warmer months. Expansion of javelina occupancy may be related to a slight trend in increasing minimum winter temperatures, because severe winters were hypothesized to limit the northern distribution of javelinas. Additionally, javelinas appear dependent upon a tree or shrub overstory, ideally associated with riparian corridors, to mitigate heat stress associated with occupancy of Chihuahuan Desert habitats.

Stand Development and Population Dynamics of Curlleaf Mountain Mahogany (Cercocarpus ledifolius Nutt.) Woodlands in Utah's Bear River Mountains

Abstract Curlleaf mountain mahogany (Cercocarpus ledifolius Nutt.) is a little-studied woodland tree that occurs in pure stands throughout the Intermountain West. Stand development and population dynamics of this species are poorly understood, despite their relevance to management. We describe here the development of stand age structures and population dynamics of mahogany woodlands in northern Utah using tree ages and measurements representing five structurally diverse stands. Establishment periods in all stands lasted decades, and regeneration continued intermittently in the absence of stand-replacing disturbance, eventually creating multiaged structure. Height, crown size, and basal area varied among older mahogany, which may reflect more intense intraspecific competition or increased likelihood of crown damage in older stands. Mahogany woodland managers face significant challenges. It is difficult to characterize historic stand conditions using current age structures because aging mature trees is generally unfeasible. Furthermore, there is little precedent for regenerating mahogany using silvicultural methods. Results suggest that the biggest risk in regenerating mahogany woodlands is low seedling survival, leading to the prolonged absence of mature trees. Consequently, multiaged methods that retain mature trees are recommended.

Ectomycorrhizas of Cercocarpus ledifolius (Rosaceae)

Woody species in the Rosaceae form ectomycorrhizal associations, but the fungal symbionts are unknown. The species of fungi determine whether host plants are isolated from other ectomycorrhizal species in the plant community or linked with other trees through mycorrhizal networks. In this study we identified the fungi that form ectomycorrhizas with Cercocarpus ledifolius (curl-leaf mountain mahogany). • Soil samples were collected under canopies of C. ledifolius. Ectomycorrhizas were described by morphology and by DNA sequences of the ITS region. Host species were confirmed by rbcL sequences. • Sixteen species of fungi were identified from ectomycorrhizas of Cercocarpus ledifolius. The ectomycorrhizal community was distinguished by the presence of a Geopora species situated in the G. arenicola clade and by the absence of Rhizopogon, suilloids, and Sebacinales. Of the species on C. ledifolius, two also occurred on trees of Quercus garryana var. breweri and four on Arctostaphylos sp. • The presence of fungal species in common with other ectomycorrhizal hosts shows that C. ledifolius, Q. garryana var. breweri, and Arctostaphylos species could be linked by a mycorrhizal network, allowing them to exchange nutrients or to share inoculum for seedling roots and new fine roots. Single-host fungi limited to C. ledifolius may improve resource acquisition and reduce competition with other ectomycorrhizal hosts. The finding of a Geopora species as a frequent mycobiont of C. ledifolius suggests that this fungus might be appropriate for inoculating seedlings for habitat restoration.

Technique to Improve Visualization of Elusive Tree-Ring Boundaries in Aspen (Populus tremuloides)

A simple, quick, and inexpensive technique to improve visualization of aspen (Populus tremuloides) tree rings under the microscope, the ‘shadow technique’, is described. The technique assumes appropriate preparation of increment cores or cross-sections and works well on the lighter portions of the sample with fungus- and bacteria-free wood. The shadow technique was used successfully to elucidate tree-ring boundaries in small diameter (<5 cm DBH) aspen from northern Utah that commonly had >100 annual rings. Crossdating verified whether the elusive rings were missing or false rings. Aspen tree-ring measurement will be greatly enhanced with the shadow technique and preliminary investigation suggests it could be used on other species such as curlleaf mountain mahogany (Cercocarpus ledifolius).

HOJAS CAÍDAS Y APORTE DE NUTRIENTES DE DIEZ ESPECIES FORESTALES TROPICALES

El estudio se realizó en el área del cantón Quevedo, en la Finca Experimental “La Represa” de la UTEQ; en parcelas experimentales permanentes de diez años de dad. Cada parcela tiene una superficie de 225 m2 (15 x 15 m). Los árboles se encuentran establecidos a una distancia de 3 x 3 m. Para determinar el aporte de hojas caídas se recolectaron muestras mensualmente durante un año con la utilización de trampas recolectoras. Se determinó la cantidad de hojas caídas por épocas del año (húmedo y seco) y transferencia de nutrientes (N, P, K, Ca, Mg). El aporte de hojas caídas resultó ser mayor en la época seca. La transferencia de nutrientes fue mayor en las especies: Caoba de montaña (Colubrina arborecens Mill) con 139.29, Gmelina (Gmelina arbórea Roxb) con 10.32, Cedro de montaña (Ocotea floribunda (Sw) Mez) con 64.88 y Marañón (Anacardium excelsum (Kunth) Skeels) con 216.89 y 29.87 kg ha-1 año-1 de N, P, K, Ca, Mg, respectivamente.

Estimates of Elk Summer Range Nutritional Carrying Capacity Constrained by Probabilities of Habitat Selection

We used habitat-selection data from a reintroduced population of elk (Cervus elaphus) in northeastern Nevada, USA, to develop a resource-selection function to adjust nutritional carrying capacity estimates. Constrained estimates provide population levels that minimize overuse of key foraging communities. We estimated economic nutritional carrying capacity (INCC) for 236-kg lactating cow elk in autumn 1999 and 2000 to reflect expected animal performance under maintenance (2,550 kcal/kg DM) and good (2,750 kcal/kg DM) levels of standing digestible energy. We used our resource-selection function to redistribute INCC densities (RSFD) for aspen (Populus tremuloides), conifer, curl-leaf mountain mahogany (Cercocarpus ledifolius), sagebrush (Artemisia spp.)–herb, and snowbrush ceanothus (Ceanothus velutinus) cover types across the summer range and then adjusted original INCC estimates according to these RSFD when expected densities exceeded original INCC estimates. Maintenance performance INCC estimates were 2,533 cow elk (95% CI: 1,327–3,739) in 1999 and 1,655 (95% CI: 886–2,424) in 2000. Good performance INCC estimates were 2,264 cow elk (95% CI: 1,150–3,378) in 1999 and 1,100 (95% CI: 384–1,816) in 2000. The best habitat model provided evidence that forage availability and distance to water influenced habitat selection. Adjustments in INCC for 1999 and 2000 and at both performance levels corresponded to decreases of 18–35% in original INCC estimates. Decreases were attributed to more cow elk predicted by RSFD to be in aspen, conifer, and sagebrush–herb cover types than predicted by INCC. Each year, RSFD predicted that fewer elk would use mahogany and snowbrush cover types than original INCC models. The adjusted carrying capacity estimates provided population levels that should avoid appreciable alteration of aspen, conifer, and sagebrush–herb communities while ensuring nutritious resources during lean periods. Our paper provides a critical refinement for nutritional carrying capacity models through incorporating prediction of animal selection of nutritional resources.

Elk and Mule Deer Diets in North-Central New Mexico

Botanical composition of mule deer and elk diets in winter, spring, summer, and autumn was studied during 1998 and 1999 on woodland rangeland in north-central New Mexico using microhistological analysis of fecal samples. Our study area had no livestock grazing for 60 years but was moderately grazed by mule deer and elk. Elk and mule deer shared 3 of the top 5 key forage species when diets were pooled across seasons and years. These 3 species were oak (Quercus sp.), ponderosa pine (Pinus ponderosa Dougl.), and mullein (Verbascum thapsus L.). When data were pooled across seasons and years, overall dietary overlap between mule deer and elk was 64%. Diet overlaps of 50% or more occurred between mule deer and elk in all 4 seasons in both years of study. Throughout both years, mule deer and elk diets were dominated by browse. Mountain mahogany (Cercocarpus montanus Raf.) was the most abundant browse plant in mule deer diets; ponderosa pine was most abundant in elk diets. Both animals selected forbs, which were in low supply during the study. Scarlet globemallow (Sphaeralcea coccinea Pursh), a nutritious forb, was common in both mule deer and elk diets. Our study and others from woodland rangelands in New Mexico show high potential for forage competition between mule deer and elk. Elk are more dietarily adaptable to changing forage availability than are mule deer. Our study indicates that diets of mule deer and elk are not complementary on woodland rangelands in New Mexico. Therefore, grazing capacity is not increased by common-use grazing of the 2 animals. Both mule deer and elk herds have been increasing on our study area. Therefore, if use of common forage species is kept at moderate levels on southwestern woodland rangelands, mule deer herds can be maintained or increased when elk are present.