Treeline Habitats Research Articles

Systematic analysis of Russula in the North American Rocky Mountain alpine zone

ABSTRACT Russula (Russulales) is an important ectomycorrhizal fungal genus in Arctic and alpine regions where it occurs with Salix, Betula, Dryas, and Polygonum, yet a complex phylogenetic analysis of the genus in these habitats is lacking. This research compared collections of Russula from the Rocky Mountain alpine (Colorado, Montana, Wyoming) with reference specimens from Arctic and alpine habitats, mostly in Europe, using an in-depth morphological study and a phylogenetic analysis of the nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 (ITS barcode) and the second largest subunit of the RNA polymerase II gene (rpb2). One hundred thirty-nine Russula collections were sequenced, including type material. Ten species are reported from alpine or treeline habitats in the Rocky Mountains. This is the first formal report of R. cf. altaica, R. saliceticola, and R. subrubens from the Rocky Mountains and of R. purpureofusca in North America. Russula laevis is reported for the first time under this name with a voucher, and not as an environmental sample. Previous reports of R. nana and R. laccata are molecularly confirmed. Two species are reported from subalpine habitats at treeline: R. montana with conifers and R. cf. altaica with Betula. In this study, R. laccata, R. subrubens, and R. laevis were collected in alpine habitats but have been reported below treeline in Europe; these species may also be present at lower elevations in North America. Most species have an intercontinental distribution and have been reported in other alpine or Arctic habitats. Two unidentified and potentially new species were only found in North America and are discussed. A key to the alpine Russulas of North America is provided.

Hydraulic-stomatal coordination in tree seedlings: tight correlation across environments and ontogeny in Acer pseudoplatanus.

Hydraulic conductance is recognized as a major determinant of gas exchange and productivity. However, whether this also applies to seedlings, a critically important stage for vegetation regeneration, has been largely unknown. We analyzed the hydraulic and stomatal conductance of leaves and shoots for 6-wk-old Acer pseudoplatanus seedlings emerging in different lowland and treeline habitats and under glasshouse conditions, respectively, as well as on 9-, 15- and 18-wk-old plants, and related findings to leaf and xylem anatomical traits. Treeline seedlings had higher leaf area-specific shoot hydraulic conductance (Kshoot-L ), and stomatal conductance (gs ), associated with wider xylem conduits, lower leaf area and higher stomatal density than lowland and glasshouse-grown plants. Across the first 18 wk of development, seedlings increased four-fold in absolute shoot hydraulic conductance (Kshoot ) and declined by half in Kshoot-L , with correlated shifts in xylem and leaf anatomy. Distal leaves had higher leaf hydraulic conductance (Kleaf ) and gs compared to basal leaves. Seedlings show strong variation across growth environments and ontogenetic shifts in hydraulic and anatomical parameters. Across growth sites, ontogenetic stages and leaf orders, gs was tightly correlated with Kshoot-L and Kleaf , balancing hydraulic supply with demand for the earliest stages of seedling establishment.

Multi-dimensional evaluation of small mammal diversity in tree line habitats across the Three Parallel Rivers of Yunnan Protected Areas: Implications for conservation

Multi-dimensional evaluation of small mammal diversity in tree line habitats across the Three Parallel Rivers of Yunnan Protected Areas: Implications for conservation

Observed long-term greening of alpine vegetation—a case study in the French Alps

We combined imagery from multiple sources (MODIS, Landsat-5, 7, 8) with land cover data to test for long-term (1984–2015) greening or browning trends of vegetation in a temperate alpine area, the Ecrins National Park, in the context of recent climate change and domestic grazing practices. We showed that over half (56%) of the Ecrins National Park displayed significant increases in peak normalized difference vegetation index (NDVImax) over the last 16 years (2000–2015). Importantly, the highest proportional increases in NDVImax occurred in rocky habitats at high elevations (> 2500 m a.s.l.). While spatial agreement in the direction of change in NDVImax as detected by MODIS and Landsat was high (76% overlap), correlations between log-response ratio values were of moderate strength (approx. 0.3). In the context of above treeline habitats, we found that proportional increases in NDVImax were higher between 1984 and 2000 than between 2000 and 2015, suggesting a slowing of greening dynamics during the recent decade. The timing of accelerated greening prior to 2000 coincided with a pronounced increase in the amount of snow-free growing degree-days that occurred during the 1980s and 1990s. In the case of grasslands and low-shrub habitats, we did not find evidence for a negative effect of grazing on greening trends, possibly due to the low grazing intensity typically found in the study area. We propose that the emergence of a longer and warmer growing season enabled high-elevation plant communities to produce more biomass, and also allowed for plant colonization of habitats previously characterized by long-lasting snow cover. Increasing plant productivity in an alpine context has potential implications for biodiversity trajectories and for ecosystem services in mountain landscapes. The presented evidence for long-term greening trends in a representative region of the European Alps provides the basis for further research on mechanisms of greening in alpine landscapes.

Warming and neighbor removal affect white spruce seedling growth differently above and below treeline.

Climate change is expected to be pronounced towards higher latitudes and altitudes. Warming triggers treeline and vegetation shifts, which may aggravate interspecific competition and affect biodiversity. This research tested the effects of a warming climate, habitat type, and neighboring plant competition on the establishment and growth of white spruce (Picea glauca (Moench) Voss) seedlings in a subarctic mountain region. P. glauca seedlings were planted in June 2010 under 4 different treatments (high/control temperatures, with/without competition) in 3 habitats (alpine ridge above treeline/tundra near treeline /forest below treeline habitats). After two growing seasons in 2011, growth, photosynthesis and foliar C and N data were obtained from a total of 156, one-and-a-half year old seedlings that had survived. Elevated temperatures increased growth and photosynthetic rates above and near treeline, but decreased them below treeline. Competition was increased by elevated temperatures in all habitat types. Our results suggest that increasing temperatures will have positive effects on the growth of P. glauca seedlings at the locations where P. glauca is expected to expand its habitat, but increasing temperatures may have negative effects on seedlings growing in mature forests. Due to interspecific competition, possibly belowground competition, the upslope expansion of treelines may not be as fast in the future as it was the last fifty years.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-015-0833-x) contains supplementary material, which is available to authorized users.

Sex differences in ecology of wild yaks at high elevation in the Kekexili Reserve, Tibetan Qinghai Plateau, China

Extreme high and low altitudes and polar environments constrain the distributional limits of terrestrial mammals. In Central Asia, vegetation on the Tibetan Plateau is limited at elevations above ∼5,500 m. Although aspects of the spatial ecology of ungulates are known across many ecosystems, logistical challenges slow the development of knowledge at the upper edge of life. We studied components of the distributional ecology of wild yaks (Bos mutus) in early winter 2012. Males and females occurred above 5,000 m, but the sexes differed socially and ecologically. On average, female groups were about 15 times larger, about 100 m higher (mean elevation 4,875 m), and in wetter or more rugged topography than males. Although females with and without young did not vary in elevation, groups with calves occurred more often in habitats with steeper slopes. An ecological surrogate and congeneric, the closely related North American bison (Bos bison), also exhibits social and ecological differentiation where males occurred historically at high elevation above tree-line habitats in the Rocky Mountains. What distinguishes the present ecology and conservation of wild yaks from bison is that opportunities persist for wide-ranging yak populations across unfenced landscapes in remote protected regions of the Tibetan Qinghai Plateau.

Group Size does not Influence Territory Size and Overlap in a Habituated Population of a Cooperative Breeding Himalayan Galliforme Species

Understanding the factors that influence territorial behaviour is essential for determining whether fragmented habitats are able to support the spatial ecological conditions that maintain cooperative breeding systems of threatened bird species. Here, we examine territorial behaviour of the cooperative breeding Buff-throated Partridge Tetraophasis szechenyii in patchy tree-line habitats of the Pamuling Mountains in western China. This population has been habituated to humans through supplementary feeding by Tibetan Monks. We studied 18 groups during three consecutive breeding seasons and two non-breeding seasons from March 2007 through July 2009, using direct tracking of colourmarked individuals. Territories were occupied by stable family groups, and were centred on the interface of two or more different tree-line habitats. Groups occupied the same close area near the nest from one year to the next. However, territory sizes, estimated using radio-telemetry, were smaller compared to those of other non-cooperative breeding montane Galliformes. Both territory size and overlap were greater during the non-breeding season. Group size did not influence territory size, in either the breeding or non-breeding season. Territorial behaviour was influenced by supplementary food given at two offering sites during both seasons, in proximity to both nesting and roost sites. Further research should focus on examining the interactions between supplementary feeding and family group composition, with direct comparisons of data from non-supplementary fed partridge populations outside of Buddhist Sacred Sites.

Nesting Behavior of Szechenyi's Monal-Partridge in Treeline Habitats, Pamuling Mountains, China

We report nesting behavior of Szechenyi's Monal-Partridge (Tetraophasis szechenyii) in treeline habitats of the Pamuling Mountains, Sichuan Province, China. Szechenyi's Monal-Partridge used both ground and tree nests. Ground nests were scrapes in the soil, positioned at the base of a tree or scrub, and occurred in all habitats except Sichuan kobresia (Kobresia setchwanensis) meadow. Tree nests were cup shaped and placed 1.9–12.0 m above ground level, distributed proportionally in all habitats except scrub hollyleaf-like oak (Quercus aquifolioides) and Sichuan kobresia meadow habitats. The proportion of nest types between first and re-nesting attempts did not vary significantly. Only 54% of ground nests and 33% of tree nests survived until hatching with predation being the principal cause of ground nest failure. Hatching success was 97%. We recorded six re-nesting attempts, four of which were tree nests, but all were unsuccessful. Preserving a mosaic of treeline habitats that include ground vegetation, and fir/oak woodland habitat will be essential for maintaining suitable nesting habitats for Szechenyi's Monal-Partridge in the Pamuling Mountains.

Densities and habitat preferences of Andean cloud-forest birds in pristine and degraded habitats in north-eastern Ecuador

SummaryThe montane cloud-forests of the north-central Andes and the montane grassland and transitional elfin forest of the central Andean páramo contain a high diversity of bird species including several restricted range and uncommon species. Little is known of how densities of Andean cloud-forest species are affected by habitat degradation. Bird densities within pristine and degraded habitats at the Guandera Biological Reserve, Carchi province, Ecuador were recorded over a 10-week period. Densities were calculated for 48 species; where densities could be compared, 69% of species occurred at a higher density in pristine habitats. Pristine forest had the highest species richness with 72 species and páramo contained 44 species. In total, 26% of pristine forest species were only found in pristine forest, 39% of páramo species only in páramo, 13% of farmland species only in farmland and there were no exclusively secondary scrub species; 47% of species found in pristine forest, and 50% found in páramo were found in both secondary scrub and farmland. Restricted range species recorded at Guandera included the Carunculated Caracara Phalcobenus carunculatus, Black-thighed Puffleg Eriocnemis derbyi, Chestnut-bellied Cotinga Doliornis remseni, Crescent-faced Antpitta Grallaricula lineifrons, Masked Mountain-tanager Buthraupis wetmorei and Black-backed Bush-tanager Urothraupis stolzmanni. Three further species that occurred at Guandera of relatively local occurrence were the Grey-breasted Mountain Toucan Andigena hypoglauca, Golden-breasted Puffleg Eriocnemis mosquera and Mountain Avocetbill Opisthoprora euryptera. Of these nine species at least five used degraded habitats, while three occurred only in pristine treeline habitats.

Late-glacial climate and ecology of a kettle section at Brampton, Ontario, Canada, as determined from fossil Coleoptera

A 5 m sequence of organic-rich sediments (ca. 13 000 years BP to ca. 4500 BP) from a drained glacial kettle pond near Brampton, Ontario, has yielded a rich and varied assemblage of coleopteran fossils. This paper discusses the beetles recovered from the basal 1 m of the section (ca. 13 000 to 12 500 BP), which represent the earliest phase of deposition in the kettle, prior to the final melt-out of underlying ice. The species are typical of northern boreal or tree-line habitats today. They illustrate that during this time the landscape was predominantly open ground, with herb and shrub vegetation. Individual trees or isolated clumps of conifers were nearby, as suggested by the presence of scolytids (bark beetles). The mean July temperature was in the range from 12.5 to 15 °C, indicating that the lack of trees is a lag effect in colonization, perhaps due to unsuitable substrate conditions rather than to an unfavourable climate.