Treeline Research Articles

Impact of climate change on the ecosystem of the central Himalayas, Nepal

The threats of climate change are found in both developed and developing countries. Since the impacts of climate change are global, irreversible, and pervasive, it is gaining worldwide attention. High mountains are the first indicators of climate change. However, the idea of what causes climate change effects on multiple ecosystem services remains scattered. This article is meant for information regarding the impacts of climate change on the ecosystem of Nepal. The result shows that climate change causes tree line shifting, change in land cover, extinction of species due to loss of habitat, imbalance in carbon sequestration on the terrestrial ecosystem while eutrophication of water bodies and extinction of endemic fish species was reported from the aquatic ecosystem. Tropical area is considered to be more affected by climate change in terms of Natural disasters and Health impacts. Moreover, different types of ecological modeling can be simulated in the context of Nepal for the prediction and future analysis of the impacts of climate change in the Ecosystem. Therefore, the impact of climate change is crucial and challenging.

Contribution of conspecific negative density dependence to species diversity is increasing towards low environmental limitation in Japanese forests

Species coexistence is a result of biotic interactions, environmental and historical conditions. The Janzen-Connell hypothesis assumes that conspecific negative density dependence (CNDD) is one of the local processes maintaining high species diversity by decreasing population growth rates at high densities. However, the contribution of CNDD to species richness variation across environmental gradients remains unclear. In 32 large forest plots all over the Japanese archipelago covering > 40,000 individual trees of > 300 species and based on size distributions, we analysed the strength of CNDD of individual species and its contribution to species number and diversity across altitude, mean annual temperature, mean annual precipitation and maximum snow depth gradients. The strength of CNDD was increasing towards low altitudes and high tree species number and diversity. The effect of CNDD on species number was changing across altitude, temperature and snow depth gradients and their combined effects contributed 11–18% of the overall explained variance. Our results suggest that CNDD can work as a mechanism structuring forest communities in the Japanese archipelago. Strong CNDD was observed to be connected with high species diversity under low environmental limitations where local biotic interactions are expected to be stronger than in niche-based community assemblies under high environmental filtering.

Air temperature as a determinant of the forest line in the Tatras

Abstract The forest line has been widely studied by a number of scientists representing various research disciplines. Changes in its position are an indicator of climate change. However, despite numerous studies, it is not always known what has the greatest influence on the position of the forest line. In the Tatras, which are Alpine moun-tains, the position of the forest line in places not disturbed by human activity or slope processes mainly depends on the annual mean air temperature and the number of days with negative temperature and its value in the warm season. The most unfavourable thermal conditions are found at the bottoms of concave landforms, just above the forest line. This thermal barrier effectively limits the upward movement of the forest line, even if the average annual temperature increases. Small concave landforms may have a higher vertical temperature gradient and lower air temperature values at their bottoms than larger and higher-lying forms.

The dynamic land-cover of the Altai Mountains: Perspectives based on past and current environmental and biodiversity changes.

We present climate-dependent changes in the high-mountain forest ecotone, old-growth forests, alpine phytocenoses, and deglaciated forelands in the Aktru glacial basin (Altai Republic, Russia). A number of independent sources (variations in upper treeline altitude, dendrochronological data, analysis of lacustrine sediments and botanical and geographical studies linked with the dynamics of glacial-dammed lakes in the Chuya and Kurai intermountain depressions) suggest Holocene temperatures reached about 4°C higher than today. Unlike the European Alps, glaciers in the continental Altai Mountains disappeared before forming again. Also, the upper altitudinal limit of mountain forests during the Holocene was greater than in the European Alps. The high variability of mountain ecosystems in southern Siberia suggests their potential instability in a currently changing climate. However, periglacial successions associated with the strong continental climate and glacier retreat represent an area of increasing biodiversity and plant cover. The historical and current sensitivity of the continental mountains to climate variations which exceeds that of the European Alps requires greater understanding, environmental protection, and increased social responsibility for the consequences of anthropogenic contributions to climate change: the isolated Altai areas contribute little to climate changes, but are greatly affected by them.

BIOVERA-Tree: tree diversity, community composition, forest structure and functional traits along gradients of forest-use intensity and elevation in Veracruz, Mexico.

BackgroundHere, we describe BIOVERA-Tree, a database on tree diversity, community composition, forest structure and functional traits collected in 120 forest plots, distributed along an extensive elevational gradient in Veracruz State, Mexico. BIOVERA-Tree includes information on forest structure from three levels of forest-use intensity, namely old-growth, degraded and secondary forest, replicated across eight elevations from sea-level to near the tree line at 3500 m and on size and location of 4549 tree individuals with a diameter at breast height ≥ 5 cm belonging to 216 species, 154 genera and 80 families. We also report measurements of eight functional traits, namely wood density for 143 species, maximum height for 216 species and leaf traits including: specific leaf area, lamina density, leaf thickness, chlorophyll content and leaf area for 148 species and leaf dry matter content for 145 species.New informationBIOVERA-Tree is a new database comprising data collected in a rigorous sampling design along forest-use intensity and elevational gradients, contributing to our understanding of how interactive effects of forest-use intensity and elevation affect tree diversity, community composition and functional traits in tropical forests.

The Spatial Pattern of the Upper Limit of Montane Deciduous Broad-Leaved Forests and Its Geographical Interpretation in the East Monsoon Realm of China

Montane deciduous broad-leaved forests (MDB) are mainly distributed in the east monsoon realm of China. The upper limit of MDB significantly varies from mountain to mountain. However, the spatial pattern of the upper limit of MDB and its underlying drivers are still unknown. In this study, we conducted hierarchical multiple regression to quantify the effect of climatic factors, peak elevation, and cold tolerance of dominant species on the geographical distribution of the upper limit of MDB on 75 mountains in the east monsoon realm of China. The results show that: (1) the upper limit of MDB in the east monsoon realm of China, 2800 m, is the highest in Taibai peak of the Qinling mountain ranges, from where it tends to decrease both northward and southward. (2) The upper limit of MDB on the mountains with climatic treeline is mainly affected by climatic factors, the minimum temperature of the coldest month (MinT), and the precipitation seasonality (PS), with an R2 of 0.733. (3) The upper limit of MDB on both temperate and subtropical mountains without climatic treeline is affected by MinT, PS, peak elevation, and cold tolerance of dominant species together, with an R2 of 0.793 and 0.748, respectively. (4) The dominant species of the upper limit of MDB significantly differ temperate and subtropical ranges, the former of which is mainly in the genus Betula, and the latter of which is in the genus Quercus. The upper limit of MDB with the genus Fagus as dominant species is only distributed in the mountains towards the south of the Qinling mountain ranges. (5) The warmth index (WI) at the upper limit of deciduous broad-leaved forest on the mountains with climatic treeline is about 60 °C month, which is lower than that at the northernmost boundary of the latitudinal distributed deciduous broad-leaved forest (90 °C month). Our study revealed the spatial pattern and geographical drivers of the upper limit of MDB, improved our understanding of differences in MDB vegetation among different mountain ranges, and provided climatic correlates for predicting the dynamics of the upper limit of MDB under climate change.

The Dry and the Wet Case: Tree Growth Response in Climatologically Contrasting Years on the Island of Corsica

Stem radial variations of Corsican Black pine (Pinus nigra Arnold subsp. laricio Maire) and Maritime pine (Pinus pinaster Aiton) were monitored to quantify the impact of two meteorologically contrasting consecutive years. On the French island of Corsica, in the western Mediterranean basin, the year 2017 was extremely dry, while 2018 was exceptionally wet. We attached electric band dendrometers to 36 pines along an east–west transect, spanning the central mountain range, and set up automated weather stations at all five sites, ranging from 10 m asl to 1600 m asl. Stem radial variations (SRV) were separated into irreversible growth (GRO) and tree water deficit (TWD) periods. During the drought of 2017, the most severe tree water deficits occurred in the western part of the island, whereas trees at higher elevations were more affected than at lower elevations. A prolonged decrease of SRV, even close to the tree line, suggests bimodal growth and reveals high plasticity of growth patterns in both Corsican pines. Stem radial variations correlated significantly with precipitation and temperature. The positive correlations of GRO with precipitation and the negative correlations of TWD with temperature imply that high evapotranspiration led to the intense period of TWD in 2017. A novel approach was used to further investigate the growth/climate relationship by including synoptic-scale pressure situations. This revealed that an elevation gradient in GRO per weather pattern was only present in the wet year and that even rarely occurring weather patterns can have a substantial impact on tree growth. This novel approach provides a more comprehensive insight into meteorological drivers of tree growth patterns by incorporating different scales of the climatic system.

Fungal community dynamics across a forest-alpine ecotone.

Climate change is causing upward shift of forest lines worldwide, with consequences for soil biota and carbon (C) sequestration. We here analyse compositional changes in the soil biota across the forest line ecotone, an important transition zone between different ecosystems. We collected soil samples along transects stretching from subalpine mountain birch forests to alpine heath. Soil fungi and micro-eukaryotes were surveyed using DNA metabarcoding of the ITS2 and 18Smarkers, while ergosterol was used to quantify fungal biomass. We observed a strong shift in the soil biota across the forest line ecotone: Below the forest line, there were higher proportions of basidiomycetes and mucoromycetes, including ectomycorrhizal and saprotrophic fungi. Above it, we observed relatively more root-associated ascomycetes, including Archaeorhizomycetes, ericoid mycorrhizal fungi and dark septate endophytes. Ergosterol and percentage C content in soil correlated strongly and positively with the abundance of root-associated ascomycetes. The predominance of ectomycorrhizal and saprotrophic fungi below the forest line probably promote high C turnover, while root-associated ascomycetes above the forest line may enhance C sequestration. With further rise in forest lines, there will be a corresponding shift in the below-ground biota, probably leading to enhanced release of soil C.

FACTORS DETERMINING THE PHENOMENA IN THE UPER TREE LINE ECOTONE IN THE POLAR URALS MOUNTAINS

The article presents the results of the analysis of long-term studies dedicated to the reaction of woody plants to various extreme factors in the Rai-Iz mountain massif and Chernaya mountain, which are located on the southeastern slope of the Polar Urals in the Sob River basin (Russia). The analysis was performed using a unique archive of landscape photos, which were made by the authors from the beginning of the 1960s until the present. The classifi cation and description of the phenomena that are caused by the infl uence of environmental factors on woody vegetation, as well as their presentation using landscape photos, allow us to expand the possibilities of using ground-based images for the purposes of environmental photo monitoring of woody vegetation at the tree line. They can be used as an independent data source to identify factors that determine a morphological structure and spatial altitude of woody vegetation.

Climate-driven palaeofloral fluctuations on a volcanic slope from the low latitudes of the Palaeotethys (early Permian, West Sumatra)

The present paper focuses on plant diversity fluctuations within three ecosystems from a volcanic slope in the sequence analytical context of three superimposed cyclicities. This analysis was possible thanks to the isotopic age evaluation of the volcanic Merangin section that bracketed the Mengkarang Formation on West Sumatra between 296.77 ± 0.04 and 296.14 ± 0.09 Ma (Asselian, Lower Permian). The Merangin section consists of a 490 m long fining and thinning tuffaceous aggregational sequence composed of eight short-eccentricity fining and thinning upwards parasequences. The palaeoflora along the sequence varies from tropical wet taxa, comprising cordaitalean and ferns, to mesic-xeric taxa, typified by seed ferns and early conifers. Herein the palaeofloral content of 14 consecutive lahars from a single volcanic accretion wedge in the seventh parasequence is described in detail. It displays a gradual increase in the ratios of (seed) ferns (Macralethopteris hallei, Sphenopteris sp. and gigantopterids) and early conifers (Dicranophyllum molle, Tobleria bicuspis), reaching a 100% in the 6th bed, and returning to 100% cordaitalean and ferns. The high ratio of seed ferns and early conifers in the 6th lahar is interpreted as reflecting a temporary lowering of the tree line caused by a glacial maximum from a high order cycle (obliquity or precession), superimposed on a short-eccentricity cycle, which in turn is superimposed on our third-order cycle palaeofloral transition described earlier for the whole sequence. Along this lower Permian section from the low latitudes from the Palaeotethys, glacial-interglacial cycles are seen to affect the fluctuations of the vegetation line in a chiefly similar way as during the Quaternary. The diversity fluctuations for three ecosystems (wetlands, lower and upper slope) are modelled for two of the three or more superimposed cycles. Emphasis is put on the appearance of a glacial palaeoflora on top of the sequence.

Summer temperature variability since 1730 CE across the low-to-mid latitudes of western North America from a tree ring blue intensity network

Regional reconstructions of air temperature over the past millennium provide critical context for ongoing climate change, but they are temporally limited in the recent period or absent for many parts of the world. We demonstrate the use of latewood blue intensity (LWB) to reconstruct current-year growing (warm) season maximum temperatures (Tmax) in the low-to-mid latitudes (30°-50°N) of western North America. We present a new tree ring network comprised of 26 LWB chronologies developed from living, high-elevation Engelmann spruce (Picea engelmannii Parry ex Engelm.) sampled across the western United States. The LWB parameter shows strong, positive (r = 0.65–0.73), and temporally-stable correlations with growing season Tmax. From this network we present 4 regional Tmax reconstructions, which characterize regional temperature histories across western North America from northern Mexico to southern British Columbia over the past 4 centuries. Our comparison of these 4 temperature reconstructions highlights the spatial patterns of regional temperature trends throughout time. These reconstructions provide important updates and increased data point density to the tree ring temperature proxy network of the Northern Hemisphere. We highlight the use of blue intensity methods at both low- and mid-latitude upper tree line locations to increase the presence of strongly temperature-sensitive records at increasingly lower latitudes of the Northern Hemisphere.

On the occurrence of the Himalayan Wolf Canis lupus, L. 1758 (Mammalia: Carnivora: Canidae) in the Gaurishankar Conservation Area, Nepal; its existence confirmed through sign and visual evidence in Rolwaling Valley

The Himalayan Wolf Canis lupus L., a top predator of the Third Pole, is proposed to be of a distinct wolf lineage (C. himalayensis) relative to the Holarctic Grey Wolf as described by mtDNA analyses. A biodiversity survey organized by the Gaurishankar Conservation Area Project (GCAP) has captured images of wolves in three different regions, and the study team has observed wolf scats in five additional regions above the tree line in Rolwaling Valley. Further, interviews with local herders provided evidence of wolf depredation of livestock in the area. The Rolwaling Valley in the Gaurishankar Conservation Area was the study area which was divided into 12, 4 x 4 km (16 km2) grid cells, each supplied with one camera trap operated continuously from June to November 2019 (only 6 out of 12 cameras functioned for the duration of our study). Wolf detections were recorded by camera traps from Yalung Pass (4,956 m), Tsho-Rolpa glacial Lake (4,536 m) and the Dudhkunda ridgeline (5,091 m). The photo capture rate index (PCRI) for wolves was 0.71. Our study reports the first photographic evidence of the Himalayan Wolf in the Rolwaling Valley.

Vegetation analysis of the subalpine beech forest on the upper forest line in the Julian Alps (NW Slovenia and NW Italy) and in the northern Dinaric Alps

Abstract Using hierarchical clustering with unweighted pair-group method with arithmetic mean (UPGMA) we arranged 603 phytosociological relevés of beech forests on the present upper forest line, mainly from the Julian Alps and the Trnovo Forest Plateau (we also included the relevés from the Karawanks and the Kamnik Alps), into 32 clusters. Based on their analysis and comparison with previously described similar (alti)montane-subalpine beech communities we classified most of the relevés into the association Polysticho lonchitis-Fagetum and its new subassociations ericetosum carneae, cardaminetosum trifoliae, luzuletosum niveae, luzuletosum luzuloidis, calamagrostietosum variae, allietosum victorialis, adoxetosum moschatellinae, stellarietosum nemorum and several new variants. The altitude of the studied stands is predominantly 1400 to 1550 m (the upper line is at 1660 m); they occur at all aspects, frequently on steep and very steep slopes, mainly on limestone and dolomite limestone, the predominant soil type is rendzina. These stands are species rich (on average 61 species per relevé, altogether more than 500 vascular plants) and have many species in common with the stands of associations Rhododendro hirsuti-Fagetum and Rhodothamno-Laricetum.

Forest Structure and Composition under Contrasting Precipitation Regimes in the High Mountains, Western Nepal

The high mountains stretch over 20.4% of Nepal’s land surface with diverse climatic conditions and associated vegetation types. An understanding of tree species and forest structural pattern variations across different climatic regions is crucial for mountain ecology. This study strived to carry out a comparative evaluation of species diversity, main stand variables, and canopy cover of forests with contrasting precipitation conditions in the Annapurna range. Firstly, climate data provided by CHELSA version 1.2, were used to identify distinct precipitation regimes. Lamjung and Mustang were selected as two contrasting precipitation regions, and have average annual precipitation of 2965 mm and 723 mm, respectively. Stratified random sampling was used to study 16 plots, each measuring 500 m2 and near the tree line at an elevation range of 3000 to 4000 m across different precipitation conditions. In total, 870 trees were identified and measured. Five hemispherical photos using a fisheye lens were taken in each plot for recording and analyzing canopy cover. Margalef’s index was used to measure species richness, while two diversity indices: the Shannon–Wiener Index and Simpson Index were used for species diversity. Dominant tree species in both study regions were identified through the Important Value Index (IVI). The Wilcoxon rank-sum test was employed to determine the differences in forest structure and composition variables between the two precipitation regimes. In total, 13 species were recorded with broadleaved species predominating in the high precipitation region and coniferous species in the low precipitation region. Higher species richness and species diversity were recorded in the low precipitation region, whereas the main stand variables: basal area and stem density were found to be higher in the high precipitation region. Overall, an inverse J-shaped diameter distribution was found in both precipitation regions signifying uneven-aged forest. A higher proportion of leaning and buttressed trees were recorded in the high precipitation region. However, similar forest canopy cover conditions (>90%) were observed in both study regions. The findings of this research provide a comprehensive narrative of tree species and forest structure across distinct precipitation regimes, which can be crucial to administrators and local people for the sustainable management of resources in this complex region.

Studies on diversity of charadriiformes (Chordata: Aves) in Chandertal wildlife sanctuary, Himachal Pradesh, India

The studies on diversity of order Charadriiformes (Aves) in Chandertal Wildlife Sanctuary, covering an area of 38.53 sq. km. at an elevation more than 4200 meters in Trans Himalayas is above tree line in which various field trips were organized in different months of year except winters (November to May) due to excessive snowfall at Rohtang pass and Kunzam pass resulting into inaccessible roads. Since the biodiversity decreases with increasing altitude above tree line, similarly our study revealed the presence of only four species belonging to three families of order Charadriiformes viz. Gallinago solitaria; Calidris minuta (Scolopacidae), Charadrius mongolus (Charadriidae) and Himantopus himantopus (Recurvirostridae).

Predicting arctic-alpine lake dissolved oxygen responses to future tree line advance at the Swedish forest-tundra transition zone.

High latitude regions of the globe are experiencing higher warming rates than many other areas and are expected to undergo dramatic change with future warming (Carpenter et al., 2011; Kuhn et al., 2021). One such change is the poleward advance of tree line into prior tundra environments. While nominally a terrestrial ecosystem change, this advance may dramatically alter aquatic ecosystems, with lakes in particular being highly responsive to events that occur in the surrounding landscape. Klaus et al. (2021) address this important issue by using a space-for-time substitution across 40 Swedish arctic-alpine lakes to understand how a transition from tundra to forested watersheds will influence lake dissolved oxygen (DO).

A new endemic species of Mollinedia (Mollinedieae, Monimiaceae) from the southern limit of the Atlantic coastal moist forest

A revision of Monimiaceae from the Southern limit of the Atlantic forest domain resulted in the discovery of a species heretofore undescribed. Mollinedia leucantha, a treelet endemic to the Atlantic coastal moist forest in southern Brazil, is described and illustrated. Morphologically the new species is most similar to Mollinedia schottiana, from which it is set apart by characteristics in the rhytidome, leaves, trichomes, flowers and fruitlets, as well as by distinct flowering times. Additionally, scanning electron microscopy (SEM) images of the flowers and a key to distinguish morphologically similar or related species in the subtropical Atlantic forest are presented. A preliminary extinction risk assessment is also provided for the new species.

Effect of Long-Term Nitrogen and Phosphorus Additions on Understory Plant Nutrients in a Primary Tropical Forest

Humid tropical forests are commonly characterized as N-rich but P-deficient. Increased N deposition may drive N saturation and aggravate P limitation in tropical forests. Thus, P addition is proposed to mitigate the negative effects of N deposition by stimulating N cycling. However, little is known regarding the effect of altered N and P supply on the nutrient status of understory plants in tropical forests, which is critical for predicting the consequences of disturbed nutrient cycles. We assessed the responses of N concentration, P concentration, and N:P ratios of seven understory species to N and P addition in an 8-year fertilization experiment in a primary forest in south China. The results showed that N addition had no effect on plant N concentration, P concentration, and N:P ratios for most species. In contrast, P addition significantly increased P concentration, and decreased N:P ratios but had no effect on plant N concentration. The magnitude of P concentration responses to P addition largely depended on the types of organs and species. The increased P was more concentrated in the fine roots and branches than in the leaves. The gymnospermous liana Gnetum montanum Markgr. had particularly lower foliar N: P (~9.8) and was much more responsive to P addition than the other species studied. These results indicate that most plants are saturated in N but have great potential to restore P in primary tropical forests. N deposition does not necessarily aggravate plant P deficiency, and P addition does not increase the retention of deposited N by increasing the N concentration. In the long term, P inputs may alter the community composition in tropical forests owing to species-specific responses.

Forests buffer the climate‐induced decline of body mass in a mountain herbivore

Climate change is known to affect key life‐history traits, such as body mass, reproduction, and survival in many species. Animal populations inhabiting mountain habitats are adapted to extreme seasonal environmental conditions but are also expected to be especially vulnerable to climate change. Studies on mountain ungulates typically focus on populations or sections of populations living above the tree line, whereas populations inhabiting forested habitats are largely understudied. Here, we investigate whether forested areas can mitigate the impact of climatic change on life‐history traits by evaluating the interactive effects of temperature and habitat characteristics on body mass variation in the Alpine chamois Rupicapra rupicapra rupicapra. We examined data of 20,573 yearling chamois collected from 1993 to 2019 in 28 mountain ranges in the Austrian Eastern Alps, characterized by different proportion of forest cover. Our results show that the temporal decline of chamois body mass is less pronounced in areas with greater proportion of forest cover. For chamois living in forest habitats only, no significant temporal change in body mass was detected. Variation in body mass was affected by the interaction between density and snow cover, as well as by the interaction between spring temperatures and forest cover, supporting the role of forests as thermal buffer against the effects of increasing temperatures on life‐history traits in a mountain ungulate. In turn, this study suggests a buffering effect of forests against climate change impacts. Assessments of the consequences of climate change on the life‐history traits and population dynamics of mountain‐dwelling species should thus consider the plasticity of the species with respect to the use and availability of different habitat types.

Climate-induced reversal of tree growth patterns at a tropical treeline.

Globally, cold-limited trees and forests are expected to experience growth acceleration as a direct response to warming temperatures. However, thresholds of temperature limitation may vary substantially with local environmental conditions, leading to heterogeneous responses in tree ecophysiology. We used dendroecological and isotopic methods to quantify shifting tree growth and resource use over the past 143 years across topographic aspects in a high-elevation forest of central Mexico. Trees on south-facing slopes (SFS) grew faster than those on north-facing slopes (NFS) until the mid-20th century, when this pattern reversed notably with marked growth rate declines on SFS and increases on NFS. Stable isotopes of carbon, oxygen, and carbon-to-nitrogen ratios suggest that this reversal is linked to interactions between CO2 stimulation of photosynthesis and water or nitrogen limitation. Our findings highlight the importance of incorporating landscape processes and habitat heterogeneity in predictions of tree growth responses to global environmental change.