Shrub Rhododendron Research Articles

Population Structures and Dynamics of Rhododendron Communities with Different Stages of Succession in Northwest Guizhou, China.

To explore the population structures and dynamics of Rhododendron shrub communities at different stages of succession in northwest Guizhou, China, this study examined the populations of Rhododendron annae and Rhododendron irroratum shrub with two different stages. A space-for-time substitution was employed to establish the diameter class/height structures, static life tables, and survival/mortality rate/disappearance rate curves of both Rhododendron populations with different orders of succession. Their structural and quantitative dynamics were analyzed, and their development trends were predicted. The results showed that, quantitatively, the populations of R. annae and R. irroratum in the two Rhododendron communities with different orders of succession were dominated by age classes one, two, and three as well as height classes i, ii, and iii. The number of Rhododendron plants at the three age classes and the three height classes accounted for 97.61-100% of the total. The quantitative dynamic indices of R. annae and R. irroratum were both greater than 0, with and without considering external interference. In terms of age class and height structures, both Rhododendron populations were expanding populations, presenting "inverted-J-shaped" and irregular pyramid patterns. There was a sufficient number of young individuals, but few or no old individuals. Both survival curves of the populations of R. annae and R. irroratum in the two Rhododendron communities with different orders of succession belonged to the Deevy-II type. In the late stage of succession, the mortality curves and disappearance curves of both Rhododendron populations in these communities presented a trend of increasing first and then decreasing with increasing age class. This result indicates that at each age class, R. annae and R. irroratum showed a trend of gradual increase after two, four, and six years. In brief, the populations of R. annae and R. irroratum have rich reserves of seedlings and saplings, but high mortality and disappearance rates. In this context, it is necessary to reduce human interference and implement targeted conservation measures to promote the natural renewal of Rhododendron populations.

Global warming alters Himalayan alpine shrub growth dynamics and climate sensitivity

Global climate change is having significant effects on plant growth patterns and mountain plants can be particularly vulnerable to accelerated warming. Rising temperatures are releasing plants from cold limitation, such as at high elevations and latitudes, but can also induce drought limitation, as documented for trees from lower elevations and latitudes. Here we test these predictions using a unique natural experiment with Himalayan alpine shrub Rhododendron anthopogon and its growth responses to changing climate over a large portion of its latitudinal and elevational ranges, including steep precipitation and temperature gradients. We determined growth dynamics during the last three decades, representing period of accelerated warming, using annual radial growth increments for nine populations growing on both wet and warm southern localities and drier and cold northern localities in the Himalayas along elevation gradients encompassing the lower and upper species range limits. A significant growth increase over past decades was observed after controlling for confounding effect of shrub age and microsites. However, the magnitude of increase varied among populations. Particularly, populations situated in the lower elevation of the northernmost (cold and dry) locality exhibited most substantial growth enhancement. The relationship between growth variability and climate varied among populations, with the populations from the coldest location displaying the strongest responsiveness to increasing minimum temperatures during July. Minimum temperatures of April and August were the most important factor limiting the growth across most populations. Potential warming-induced drought limitation had no significant impact on growth variation in any part of the species geographic range. Overall, our findings indicate that plant growth is continuously increasing in recent decades and growth-climate relationships are not consistent across populations, with populations from the coldest and wettest localities showing stronger responses. The observed patterns suggest that dwarf-shrubs benefit from ongoing warming, leading to increased shrubification of high elevation alpine ecosystems.

Effects of clearcutting on species composition and community renewal of Rhododendron shrubs in northwest Guizhou Province, China

Tree base sprouting is the main reproduction and expansion mode of Rhododendron plants. By leveraging the plot survey method, the species composition, community renewal, and species diversity in three Rhododendron shrub communities in control, and before and after clearcutting (CK, D3yr, and D6yr, respectively) were studied. Moreover, the dissimilarity of Rhododendron communities in CK, D3yr and D6yr were analyzed. The results showed that there were 26 plant species belonging to 14 families and 22 genera, in 3 communities in total, with 19 species of shrub plants and 7 species of herbaceous plants. The number of species increased from 13 in CK to 23 in D3yr and then decreased to 20 in D6yr. The height and coverage of D3yr and D6yr reached 39.3% and 58.9% of that of CK, respectively. The relative height of CK, D3yr, and D6yr was 43.79%, 65.4%, and 58.54%, respectively. The coverage of D3yr and D6yr reached 60.8% and 114.70% of that of CK, respectively. The relative coverage of CK, D3yr, and D6yr was 19.05%, 83.24%, and 77.32%, respectively. The important value of Rhododendron plants in the communities increased from 0.42 in CK to 0.74 in D3yr, and then decreased to 0.67 in D6yr. The α diversity in the shrub layer of D3yr and D6yr were generally lower than those of CK except Pielou evenness index. The β diversity indicates that the similarity between CK and D3yr was lower, that between CK and D6yr was moderate, and that between D3yr and D6yr was higher. The sprouting height and coverage of Rhododendron plants was significantly correlated with age and sprouting time. The sprouting ability of Rhododendron plants increased first and then decreased with age, while the sprouting ability of Rhododendron plants with age of 10–12 years was the strongest. Clearcutting measures can improve the dominance of Rhododendron plants in the communities, promote the sprouting and renewal of Rhododendron population, and accelerate the succession rate of communities.

Altitudinal gradient drives significant changes in soil physico-chemical and eco-physiological properties of Rhododendron anthopogon: a case study from Himalaya

The best natural laboratories for studying the ecological responses of plants are high-altitude areas like the Himalaya, where many gradients coexist on a relatively small spatial scale. Here, we investigate the effect of soil physico-chemical and eco-physiological properties on the broadleaf evergreen woody shrub Rhododendron anthopogon D.Don along an altitudinal gradient in the Kashmir Himalaya. We collected leaf and soil samples for eco-physiological and soil physico-chemical analysis, respectively, at five different sites along an altitudinal gradient (3,220–3,908 m). Our results demonstrate a significant difference between soil physico-chemical and eco-physiological parameters along the altitudinal gradient. A significant correlation was observed between different studied parameters and altitude. Principal component analysis of studied soil physico-chemical and eco-physiological parameters revealed that all the sites were grouped into four clusters according to altitude, suggesting a more pronounced effect of altitude. Our findings showed that soil infiltration capacity increased with altitude, which would be helpful for the growth and development of R. anthopogon. We also observed significant variations in eco-physiological parameters, demonstrating their critical involvement in adapting R. anthopogon to the harsh environment of the alpine regions of Kashmir Himalaya. Therefore, the present study adds to our understanding that R. anthopogon has sufficient soil physico-chemical and eco-physiological plasticity, which should be favorable for its survival in future climates, offering an adaptive advantage and expanding its range shortly.

Inconsistent Growth Responses of Alpine Rhododendron Shrubs to Climate Change at Two Sites on the Eastern Tibetan Plateau

Evidence is accumulating that the radial growth of high-elevation Rhododendron shrubs has high dendrochronological potential. However, it remains unclear if the growth responses of alpine Rhododendron shrubs to climate are contingent on site conditions. Herein, the climate–growth relationships of alpine Rhododendron przewalskii Maxim. shrubs were investigated at two sites (NQ, LWQ) at an elevation of 4300 m on the eastern Tibetan Plateau. We collected ring-width data from 53 Rhododendron shrubs. Well-replicated 111-year-old and 51-year-old long shrub ring-width chronologies were built for NQ and LWQ, respectively. Mean shrub growth did not differ between the two study sites. Mean maximum temperature in September of the previous year was significantly negatively correlated with shrub ring-width indices in site NQ, whereas the August minimum temperature of the current year showed a strong negative association with shrub growth indices in site LWQ. Random effects with the shrub level condition exerted a certain influence on shrub radial growth. Results of previous studies in other forest regions across the Tibetan Plateau, along with this study, revealed the diverse responses of radial growth of alpine Rhododendron shrubs to climate change. Thus, both climatic and local-scale variables should be considered when conducting shrub-based dendrochronological studies. A warmer and drier climate in the future could further reduce Rhododendron shrub growth in particular sites and threaten the survival of alpine shrub ecosystems on the eastern Tibetan Plateau.

Использование физиологически активных веществ для увеличения ростовой активности сельскохозяйственных и декоративных растений

The effect of organic compounds synthesized at the Department of Organic Chemistry of Voronezh State University on the sowing qualities and growth performance of the deciduous shrub Rhododendron yellow (Rhododendron luteum Sweet) and sugar beet (Beta vulgaris L.) was studied. The purpose of the work was to identify the effects of 6-hydroxy‑2,2,4-trimethyl‑1,2- dihydroquinoline and its derivatives on the growth activity of Rhododendron yellow and sugar beet. Treatment of uncoated sugar beet seeds with an aqueous solution of 6-hydroxy‑2,2,4- trimethyl‑1,2-dihydroquinoline increased the seed germination energy by 37–46%, the seed germination by 32–40%, average seedling length by 53–94%, and the weight of 100 seedlings by 69–125% compared to the control. Dihydroquinolines and, to a lesser extent, tetrahydroquinolines may be considered more effective substances in the early stages of development of Rhododendron luteum. The compound 6-hydroxy‑2,2,4-trimethyl‑1,2-dihydroquinoline had a positive effect on the growth activity of Rhododendron yellow and sugar beet. The sowing qualities and growth traits of the plants studied significantly improved under the effect of synthesized organic compounds.

Variation in Water Uptake Dynamics of Dominant Wood Plants of Pinus taiwanensis Hayata Communities Based on Stable Isotopes

Plant community formation is determined by plant competition, while the water uptake depth of vegetation is regarded as a critical factor in maintaining species coexistence under competition. However, the source variation of montane plant water uptake remains poorly understood, especially under the condition of climate change. We introduced stable hydrogen and oxygen isotopes to investigate the water uptake pattern of the trees and shrubs in a Pinus taiwanensis Hayata community in subtropical mountains. The results showed that the main sources of water uptake in plants varied with soil water content, due to variations in annual precipitation distribution. In July and September, under extremely wet conditions, the evergreen conifer species P. taiwanensis and the shrub Eurya muricata mainly absorbed water from the deep soil layer (40–80 cm, more than 70%). By contrast, the deciduous shrub Rhododendron dilatatum largely relied on upper soil water (0–40 cm, 75.4%) in July but the same deep water source in September. In August and the non-growing season (January), when soil moisture content was low, plants preferred surface layer soil water (0–20 cm, above 50%). In October, the soil water in the middle (20–40 cm) and deep layers (40–80 cm) were the main water source of the three plants. However, the plant water sources showed great difference between P. taiwanensis and shrubs in November: P. taiwanensis absorbed more water from the soil surface layers (89.5%), while R. dilatatum mainly took up surface soil water (54.2%) and E. muricata predominantly obtained water from surface soil water (49.6%) and the deep soil layer (39.3%). These findings suggest that the water uptake of dominant woody plants in a P. taiwanensis community has great plasticity, and its water uptake depth varies with soil water content. In addition, these co-existing species generally absorbed water from similar soil layers in the P. taiwanensis community and exhibited a hydrological niche overlap, indicating a very possible competition between species in future water-limited conditions caused by climate change.

Species diversity of Rhododendron shrub communities and utilization of Rhododendron resources in urban green spaces of Nanjing

Species diversity of Rhododendron shrub communities and utilization of Rhododendron resources in urban green spaces of Nanjing

Intensity, frequency and rate of insect herbivory for an alpine Rhododendron shrub: elevational patterns and leaf-age effects

Intensity, frequency and rate of insect herbivory for an alpine Rhododendron shrub: elevational patterns and leaf-age effects

Shrub growth in the Alps diverges from air temperature since the 1990s

In the European Alps, air temperature has increased almost twice as much as the global average over the last century and, as a corollary, snow cover duration has decreased substantially. In the Arctic, dendroecological studies have evidenced that shrub growth is highly sensitive to temperature—this phenomenon has often been linked to shrub expansion and ecosystem greening. Yet, the impacts of climate change on mountain shrub radial growth have not been studied with a comparable level of detail so far. Moreover, dendroecological studies performed in mountain environments did not account for the potential modulation and/or buffering of global warming impacts by topography, despite its possible crucial role in complex alpine environments. To fill this gap, we analyzed a network of eight sites dominated by the dwarf shrub Rhododendron ferrugineum. The sites selected for analysis represent the diversity of continentality, elevation and slope aspect that can be found across the French Alps. We quantified annual radial increment growth for 119 individuals, assembled meteorological reanalyzes specifically accounting for topographic effects (elevation, slope and aspect) and assessed climate-growth relations using a mixed modeling approach. In agreement with a vast majority of dendroecological work conducted in alpine and arctic environments, we find that the number of growing degree days during the snow-free period snow-free growing degree days (SFGDDs) is a strong and consistent driver of R. ferrugineum growth across all sites since 1960 until the late 1980s. We also document a marked loss of sensitivity of radial growth to increasing SFGDD since the 1990s, with this decoupling being more pronounced at the driest sites. Our observations of the spatial and temporal variability of shrub sensitivity to limiting factors can be compared to the ‘divergence’ problem observed in tree-ring series from circumpolar and alpine regions and, accordingly, sheds light on possible future trajectories of alpine shrub growth in response to ongoing climate change.

Genetic structure of a widespread alpine shrub Rhododendron aureum (Ericaceae) across East Asia.

The vast territory of East Asia, including southwestern Beringia, is considered to have been almost ice free during the Pleistocene. Cold-resistant flora may have persisted in this region expanding or contracting its range during the climate cooling. Only a few plant genera have been studied with a sampling area across their entire geographic range in East Asia; therefore, the understanding of the biogeographic history of alpine flora in this region remains limited. In the present study, genetic variation and population structure in 21 populations of the alpine shrub Rhododendron aureum across its range in East Asia were assessed using 18 microsatellite loci. Phylogenetic analyses revealed three main genetic groups: Siberia, Northeast, and North Pacific. According to the geographical pattern of genetic diversity, the North Pacific group includes populations from Kamchatka, south of Russian Far East, and territories close to central Japan. This group is the most diverse and likely diverged earlier than the Siberia and Northeast groups. Ecological niche modeling predicts range expansion of this species during the period of cooling and, together with demographic history, suggests that the divergence between the three main genetic groups predated the Last Glacial Maximum. Similar to other cold-resistant species such as Larix sibirica and Juniperus communis, the pattern of genetic diversity of R. aureum supports the survival of the species at high latitudes during the Pleistocene with limited contribution of the southern populations to expansion of the species range to the Northeast region and Siberia.

甘肃南部7种高寒杜鹃生物量模拟

精确测定与模拟高山-亚高山灌丛生物量是了解陆地生态系统碳功能的重要基础工作。以甘肃南部高山-亚高山地区常见的7种高寒杜鹃（Rhododendron spp.）灌木为对象，通过标准植株收获法，建立易测因子与各器官生物量及总生物量的方程并检验拟合精度，筛选最优拟合方程。结果表明：（1）自变量和函数的类型对杜鹃生物量的模拟效果影响较大，700组方程中以D和D²H为自变量和以幂函数为模型拟合的R²相对集中、中位数都较高。（2）遴选出的35组单物种最优生物量模型的R²介于0.66-0.99之间、中位数为0.92，除山光杜鹃（Rh.oreodoxa）的茎、叶生物量和地上生物量模型为线性函数、麻花杜鹃（Rh.maculiferum）的所有模型为指数函数外，其余的生物量模型均为幂函数；D和D²H是单物种生物量模型的最佳预测变量，H仅是黄毛杜鹃（Rh.rufum）除根外、美容杜鹃（Rh.calophytum）叶生物量的最佳预测变量。（3）混合物种最优模型是以D²H为自变量的幂函数，除对叶生物量的模拟精度相对较低外，对其它生物量的模拟均较好。甘肃南部7种高寒杜鹃灌木生物量模型的建立为高寒地区灌丛生态系统碳汇功能的研究提供了支撑。;Rhododendron species are broad-leaved evergreen woody shrubs belonging to Ericaceae, and are an important constituent of alpine and subalpine ecosystems. Rh. species are endemic to Tibetan Plateau and surrounding areas. Unlike for trees, biomass estimation models are virtually lacking for Rh. species in natural communities. Therefore, accurate measurement and modeling of biomass for alpine-subalpine Rh. species is a fundamental work for quantifying carbon functions of terrestrial ecosystems. This study aimed to develop allometric models for the estimation of biomass storage of seven Rh. species' in the alpine-subalpine region of southern Gansu Province. Investigated species included Rh. rufum, Rh. przewalskii, Rh. alophytum, Rh. oreodoxa, Rh. taibaiense, Rh. capitatum and Rh. maculiferum. A total of 312 individuals were harvested for the measurements of above- and belowground biomass. Commonly used models, such as linear, logarithmic, power-law and exponential functions were used for estimating biomass, and basal diameter (D), height (H), canopy (C), crown volume (V) and square of basal diameter×plant height (D²H) from field measurements were used as independent variables, and leaf biomass, stem biomass, aboveground biomass, root biomass and total biomass were treated as dependent variables. Among a total number of 700 models tested, significant relationships were detected between biomass components and field measurements of predictors for the seven studied woody species (all P<0.01). Using D and D²H as independent variables and the power function resulted in a relatively narrow distribution and a high median of R² values. The R² values of the selected 35 optimal models for individual species from the 700 sets varied between 0.66 and 0.99, with a median of 0.92.The models for stem biomass, leaf biomass and aboveground biomass of Rh. oreodoxa were linear functions, for each of these biomass of Rh. maculiferum were exponential functions, while the rest of the biomass models were power functions. The plant height (H) was the best independent variable for the estimation of stem biomass, leaf biomass and aboveground biomass of Rh. rufum and leaf biomass of Rh. calophytum. The results also showed that the power function with D²H as the independent variable was the best model for mixed species, but the predictive power for leaf biomass was relatively low using the mixed-species' model. The establishment of seven alpine rhododendron shrub biomass models in southern Gansu Provide can serve as an important tool for the study of the carbon sink function of shrub ecosystems in alpine regions. In addition, these models may be applied to Rh. woodland elsewhere in eastern Tibetan Plateau.

Ring widths of Rhododendron shrubs reveal a persistent winter warming in the central Himalaya

Himalayan Mountains provide unique opportunities for the extension of shrub-ring based dendroclimatology beyond the upper tree limit. However, little is known about limiting climate factors of shrub growth under harsh environmental conditions. We established a new ring-width chronology of a Himalayan shrub rhododendron (Rhododendron campanulatum D. Don) at the upper Krummholz treeline in the Mt. Gaurishankar massif, central Himalaya, Nepal. Bootstrapped correlation analysis showed positive relationships between radial growth and temperatures of all months from previous November to current October. Correlations were the highest with winter (December-February) minimum temperature (r = 0.781, p < 0.001), indicating that radial growth of R. campanulatum is strongly sensitive to winter minimum temperature. The linear regression model explained 61 % of the actual winter minimum temperature variance during the calibration period 1960–2013. Periods of low and high minimum winter temperatures in the central Himalaya were consistent with cool and warm episodes found by other regional winter temperature reconstructions from the Himalayas and the Tibetan Plateau. Spatial correlation analysis with land surface temperatures revealed the spatial representativeness of our reconstruction for a larger geographical territory over the Himalayas and the Tibetan Plateau. Furthermore, winter temperature in the central Himalaya is teleconnected with the December-February India-Burma trough. The persistent increasing winter temperature in recent decades in the central Himalaya coincides with continental-scale warming. Alpine vegetation in humid regions of the Himalayas may benefit from winter warming via an earlier start and extension of the growing season, as long as moisture availability is sufficient.

Removing riparian Rhododendron maximum in post-Tsuga canadensis riparian forests does not degrade water quality in southern Appalachian streams

In the past century, the evergreen woody shrub, Rhododendron maximum, has experienced habitat expansion following foundational tree species die-off in eastern US deciduous forests. Rhododendron can potentially alter stream chemistry, temperature, trophic dynamics, and in-stream decomposition rates, given its dominance in riparian areas. Here we conducted two operational-scale (3 ha) riparian treatments that removed rhododendron through cutting alone (CR, canopy removal), or removing both the rhododendron canopy and forest floor using cutting and prescribed fire (CFFR, canopy and forest floor removal). We expected that rhododendron shrub removal, with or without soil organic horizon removal, would increase soil nutrient availability and subsequently alter stream pH, acid neutralizing capacity (ANC), inorganic nitrogen (NO3-N, NH4-N), total dissolved inorganic nitrogen, dissolved organic carbon (DOC), calcium (Ca), potassium (K), and magnesium (Mg). We hypothesized that responses would occur more quickly in the CFFR treatment. Treatments reduced shrub-, but not tree basal area. Treatments lowered soil N, but not C. Stream chemistry responses to treatments varied between CR and CFFR and were transient, generally with pH, N, and some cations declining, and aluminum (Al) and DOC showing a pulse increase. By removing rhododendron, the remaining deciduous trees likely accelerated N uptake as soil moisture availability increased. This could partially explain why we observed lower than expected stream nutrients (NO3-N, Ca, and Mg) after treatments. Initial rhododendron slash on the forest floor coupled with incomplete consumption of the O-horizon on the CFFR treatment likely elevated DOC in the upper soil horizons and mobilized Al. From a management perspective, using these treatments to restore structure and function to riparian forests in the wake of eastern hemlock mortality, with or without fire, would most likely not result in short-term diminished water quality that is common when overstory trees are harvested and may even lower stream NO3-N concentrations long term.

Tidying up the cluttered understorey: Foraging strategy mediates bat activity responses to invasive rhododendron

Biological invasions pose a significant threat to biodiversity, yet the severity and direction of impacts differs between taxa. The non-native evergreen shrub Rhododendron ponticum has colonized large areas of woodland understorey in the UK and is currently undergoing widespread clearance due to its negative impacts on native flora and as a potential host reservoir for harmful pathogens. Presence of rhododendron significantly increases the amount of structural clutter in the understorey and, hence, modifies microhabitat structure, which might have an impact on bat foraging activity. Here, for the first time, we investigated the effects of rhododendron on activity of British bat species by performing autonomous acoustic surveys at twelve sites in Richmond Park, London, where rhododendron was either present, absent or recently removed. The effects of other microhabitat characteristics likely to influence bat activity (e.g. tree diversity, canopy cover, distance to water and the presence/absence of deer) were also considered. We predicted that the increased understorey clutter present in areas invaded by rhododendron would reduce the activity of larger, less agile bats Nyctalus noctula, Eptesicus serotinus and Nyctalus leisleri (NSL), whereas the activity of bat species able to forage within, or at the edges of, clutter (e.g. Myotis spp. and Pipistrellus spp.) would not be negatively affected. While our results indicated a significant reduction in the activity of larger, open space foragers (NSL) in rhododendron-invaded areas, deer presence had a stronger negative effect than woody understory density and canopy cover on these bat species. Activity of other bats recorded was not negatively impacted by the presence of rhododendron. However, sites where rhododendron had been removed demonstrated higher bat activity levels than sites where rhododendron was present and absent with the exception of Pipistrellus pygmaeus, which displayed higher activity levels in the presence of woody understorey. NSL and P. pipistrellus also demonstrated more frequent commuting/roosting activity in sites without rhododendron, although P. pygmaeus and Myotis spp. appeared to be regularly utilising at least some rhododendron sites for this purpose. To mitigate potential negative effects of rhododendron removal on some bat species, we therefore suggest restriction of deer access to sites to enable recovery of native woody understorey.

Do southern Appalachian Mountain summer stream temperatures respond to removal of understory rhododendron thickets?

AbstractDense understory thickets of the native evergreen shrub Rhododendron maximum expanded initially following elimination of American chestnut by the chestnut blight, and later in response to loss of the eastern hemlock due to hemlock woolly adelgid invasion. Rhododendron thickets often blanket streams and their riparian zones, creating cool, low‐light microclimates. To determine the effect of such understory thickets on summer stream temperatures, we removed riparian rhododendron understory on 300 m reaches of two southern Appalachian Mountain headwater streams, while leaving two 300 m reference reaches undisturbed. Overhead canopy was left intact in all four streams, but all streams were selected to have a significant component of dead or dying eastern hemlock in the overstory, creating time‐varying canopy gaps throughout the reach. We continuously monitored temperatures upstream, within and downstream of treatment and reference reaches. Temperatures were monitored in all four streams in the summer before treatments were imposed (2014), and for two summers following treatment (2015, 2016). Temperatures varied significantly across and within streams prior to treatment and across years for the reference streams. After rhododendron removal, increases in summer stream temperatures were observed at some locations within the treatment reaches, but these increases did not persist downstream and varied by watershed, sensor, and year. Significant increases in daily maxima in treatment reaches ranged from 0.9 to 2.6°C. Overhead canopy provided enough shade to prevent rhododendron removal from increasing summer temperatures to levels deleterious to native cold‐water fauna (average summer temperatures remained below 16°C), and local temperature effects were not persistent.

Distribution of Royle’s Pika Ochotona roylei in Parvati Kunda Groundwater Complex

Royle’s Pika Ochotona roylei is high altitude animal belonging to the family Ochotonidae in order Lagomorpha. Royle’s Pika was reported in different locations between an elevation of 2180 to 5950 meters above sea level (m asl). This study carried in February and October 2017 recorded a small population of Royle’s Pika in the Parvati Kunda Groundwater Complex of Gatlang village in Rasuwa District, Nepal. A total of 12 Royle’s pika individuals were head counted from three sites while Pika foraged plants were observed in other sites. Pika was observed in talus groove amidst Rhododendron-fir forest, Fir-hemlock forest, and Rhododendron shrub close to the alpine meadow. Pika in the study was distributed from the Parvati Kunda wetland proximity at an elevation of 2605 m with a direct count of 2 individuals to an elevation of 3000 m asl beneath Tshumer hill with a headcount of 7 individuals. However, the population of Royle’s Pika in the area was estimated more. The population density of 6 individuals/hectare was calculated in the area, which is relatively lower than the population density accounted for in other areas.

Dramatic altitudinal variations in leaf mass per area of two plant growth forms at extreme heights

Knowledge of how leaf mass per area (LMA) and its components, leaf thickness (LT) and leaf density (LD), and related leaf traits may vary with altitude concerning different plant life forms at extremely high altitudes is scarce. We measured LMA, leaf nitrogen (Nmass), LT, LD, and the related anatomical characteristics of an evergreen shrub (Rhododendron aganniphum var. schizopeplum, RAS) and a wintergreen herb (Bergenia purpurascen, BP) along an altitudinal gradient above 4200 m a.s.l. to disclose how LMA for two different growth forms may vary with altitude and which leaf attribute determines the within-species variation of LMA. LMA significantly increased with rising altitude, at a pace of 40 g m−2/100 m for RAS and 12 g m−2/100 m for BP, respectively. LT was mainly responsible for the variability in LMA for RAS, and the variation of LT and LD contributed almost equally for BP. Nmass tended to decrease with rising altitude, and was negatively related to LMA and LT for both species. Foliar δ13C showed significantly rising trends with altitude, and was positively correlated with LMA and LT. The results indicated that plants at the extremely high altitudes are adapted to possessing especially higher LMA and steeper slopes of the relationships between LMA and altitude, as well as lower leaf nitrogen concentrations and higher δ13C to cope with the low-temperature environment. Compared with many other studies, LMA for both species are assumed to be more sensitive to the changing environment (especially warming). Also, Rhododendron shrub displayed steeper slope compared with dwarf herbs beneath the shrub layer indicating the former species should be more sensitive to warming climate. In all, exploring the plant strategies via leaf functional traits is of importance to understand the geography of evergreen species in alpine regions and its responses to future climate change.

Shrub facilitation promotes selective tree establishment beyond the climatic treeline

The alpine treeline is shifting upward due to climate warming. However, the treeline species composition and the pace of its upward migration can be mediated by ecological interactions. In particular, so-called ecosystem engineers, i.e. species that modulate the microscale environmental conditions, at the treeline may play a crucial role. We conducted a three-year seedling transplant experiment at the alpine treeline ecotone in southwest China to study how the shrub Rhododendron rupicola modifies the microscale physical and biotic environments and thus influences the establishment and performance of the two treeline species Larix potaninii and Picea likiangensis. Seedlings were transplanted to the current timberline and treeline, as well as above the current treeline in order to determine the responses of the two tree species to the shrub with respect to the current tree distribution. R. rupicola modified the microenvironment by increasing soil moisture and nutrient contents, buffering soil temperature fluctuations, and by increasing richness and changing the composition of root-associated fungi. As a result, tree seedlings planted under shrubs had significantly higher survival, growth rates and nutrient accumulations than those planted in open ground. Furthermore, seedlings planted at lower elevations performed better than those planted at higher elevations. Beyond the treeline, seedling survival was very low on open ground but strongly facilitated by the shrub. Finally, facilitation effects were species-specific, with Larix benefitting more from the shrub than Picea, while Picea had less mortality than Larix in the absence of the shrub. This study demonstrates that shrubs, through the amelioration of physical and biotic microenvironmental conditions, can act as stepping stones for the establishment of selective tree species beyond the current treeline. This suggests that biotic interactions can strongly modify the treeline species composition and push the treeline beyond its current climatic limits, thereby facilitating the upward shift with ongoing climate warming.

Tree Sapling Responses to 10 Years of Experimental Manipulation of Temperature, Nutrient Availability, and Shrub Cover at the Pyrenean Treeline.

Treelines are sensitive to environmental changes, but few studies provide a mechanistic approach to understand treeline dynamics based on field experiments. The aim of this study was to determine how changes in the abiotic and/or biotic conditions associated with global change affect the performance of tree seedlings (later saplings) at the treeline in a 10-year experiment. A fully factorial experiment in the Central Pyrenees was initiated in autumn 2006; 192 Pinus uncinata seedlings were transplanted into microplots with contrasting environmental conditions of (1) increased vs. ambient temperature, (2) increased nutrient availability vs. no increase, and (3) presence vs. absence of the dominant shrub Rhododendron ferrugineum. We assessed the performance of young pines on several occasions over 10 years. The pines were removed at the end of the experiment in autumn 2016 to characterize their morphology and to conduct chemical and isotopic analyses on their needles. Both the warming and the fertilization treatments increased seedling growth soon after the start of the experiment. R. ferrugineum facilitated the survival and development of pine seedlings during the early years and affected the chemical composition of the needles. Toward the end of the experiment, the transplanted P. uncinata individuals, by then saplings, competed with R. ferrugineum for light and nutrients; the presence of the shrub probably altered the strategy of P. uncinata for acquiring nutrients and buffered the effects of warming and fertilization. The pines were highly sensitive to all factors and their interactions throughout the entire experimental period. These findings indicated that the interactive effects of several key abiotic and biotic drivers associated with global change should be investigated simultaneously for understanding the contribution of young trees to treeline dynamics.