Alpine Treeline Ecotone—from Structure and Function to Ecosystem Services

A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Forest Ecology and Management".

Deadline for manuscript submissions: closed (31 March 2023) | Viewed by 16568

Special Issue Editors


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Guest Editor
College of Biology and the Environment, Nanjing Forestry University, Nanjing 210037, China
Interests: treeline ecotone; dendroecology; alpine shrub; climate warming; Tibetan Plateau
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 61004, China
Interests: treeline ecotone; plant functional trait; vegetation pattern; ecosystem services; mountain sustainable development
Special Issues, Collections and Topics in MDPI journals
Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, China
Interests: treeline ecotone; alpine plants; functional traits; plant-plant interaction; climate change

Special Issue Information

Dear Collueagues,

Alpine treeline ecotone as a sensitive monitor of environmental change has aroused increasing attention in recent decades. However, our understanding of the patterns, processes, function, and ecological services of alpine treeline ecotones and their underlying drivers are still limited. Classic and novel research from different perspectives is urgently needed to resolve these uncertainties and enhance our understanding of treeline ecosystems. Multidisciplinary contributions related to treeline ecotones (e.g., from subalpine forest or alpine grassland) are welcome. Topics include, but are not confined to, the following:

  • Alpine vegetation composition, structure and patterns;
  • Dynamics of alpine plant life;
  • Adaptation and evolution of alpine plant life;
  • Treeline changes (e.g., tree growth, recruitment, and range shifts);
  • Grasses and soil microbiota across the treeline ecotone;
  • Biogeochemical cycles from subalpine forest to alpine grassland;
  • Multiple services provided by treeline ecosystems;
  • Livelihoods of mountainous people near, at, and beyond the treeline;
  • Challenges and threats to the functions of treeline ecosystems and management practices.

Dr. Jesús Julio Camarero
Dr. Yafeng Wang
Dr. Jinniu Wang
Dr. Yang Yang
Guest Editors

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Keywords

  • treeline dynamics
  • community structure
  • vegetation pattern
  • biogeochemical cycles
  • environmental drivers
  • function and ecological processes
  • ecosystem services

Published Papers (8 papers)

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Research

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27 pages, 4858 KiB  
Article
How Does Vegetation Landscape Structure of Urban Green Spaces Affect Cultural Ecosystem Services at Multiscale: Based on PLS-SEM Model
by Qizheng Mao, Chanjuan Hu, Qinghai Guo, Yuanzheng Li and Min Liu
Forests 2023, 14(7), 1401; https://doi.org/10.3390/f14071401 - 9 Jul 2023
Cited by 2 | Viewed by 2001
Abstract
Benefits of cultural ecosystem services (CESs) of urban green spaces (UGSs) for human health and general well-being have been widely recognized. Optimizing the landscape structure of green vegetation and improving CES are essential to reduce environmental inequality, and detecting the determinant landscape features [...] Read more.
Benefits of cultural ecosystem services (CESs) of urban green spaces (UGSs) for human health and general well-being have been widely recognized. Optimizing the landscape structure of green vegetation and improving CES are essential to reduce environmental inequality, and detecting the determinant landscape features that influence CES at multi-scale is the first step. Using partial least squares structural equation modeling (PLS-SEM), we evaluated multiscale effects of vegetation landscape structure of UGS on residents’ perceptions of CES in 40 residential communities in Zhengzhou city, China. According to our results, at the micro-scale level in a single residential community, public activity spaces within green spaces, particularly large size of open spaces, was the most critical factor affecting residents’ perceptions of recreational services, which provided a multifunctional landscape, with opportunities for multiple recreational leisure activities and entertainment. Then, the percentage of vegetation coverage in green spaces, and large vegetation patches that can significantly improve residents’ perceptions of CES and were identified in the natural landscape. At the ecosystem level and species community level, although vegetation structure contributed little to the level of CES, an open vegetation structure with a large area of grass cover was particularly beneficial to increase aesthetic services, and both richness of flowers and ornamental trees improved residents’ spiritual perception. However, our findings suggest that improving the management of green space vegetation is the most effective and direct way of improving CES and resolving environmental inequities between residential communities with different vegetation coverage and infrastructure, and we suggest that future research should explore residents’ subjective perceptions of both vegetation and landscape structure of UGS at larger spatial scale. Full article
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15 pages, 4903 KiB  
Article
Spatial–Temporal Dynamics of Forest Extent Change in Southwest China in the Recent 20 Years
by Yanlin Zhang, Shujing Wang and Xujun Han
Forests 2023, 14(7), 1378; https://doi.org/10.3390/f14071378 - 5 Jul 2023
Cited by 1 | Viewed by 1008
Abstract
Deforestation is thought of as a huge threat to carbon neutrality and the development of contemporary society and it has brought wide interest and attention in the science community to develop new methods to identify and quantify the occurrence and extent of forest [...] Read more.
Deforestation is thought of as a huge threat to carbon neutrality and the development of contemporary society and it has brought wide interest and attention in the science community to develop new methods to identify and quantify the occurrence and extent of forest loss. Understanding the forest-loss patterns is essential for forest management and protection. With the help of a high-spatial-resolution remote-sensing dataset on forest loss, the spatial and temporal dynamics of deforestation patterns in forests of Southwest China (SWC) have been investigated. The major findings of this study indicated that small-scale (<5 ha) deforestation raised pervasively in the region from 2001 to 2019, and the number of large patches of forest loss (>5 ha) has decreased significantly during the same period. Moreover, the mean size of forest-loss patches showed an increase from 0.34 ha to 0.61 ha over time. With the alarming trend of increasing deforestation in the southern region of our study area, the growth of emerging forest-loss hotspots was clearly observed in Chongqing and Sichuan Province. The results promoted an indepth understanding of forest-loss patterns in SWC and can help provide more coherent guidance for further forest monitoring and conservation. Full article
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16 pages, 4364 KiB  
Article
Alpine Shrubification: Juniper Encroachment into Tundra in the Ural Mountains
by Andrey A. Grigoriev, Yulia V. Shalaumova, Dmitriy S. Balakin, Olga V. Erokhina, Svetlana Yu. Abdulmanova, Pavel A. Moiseev and Jesús Julio Camarero
Forests 2022, 13(12), 2106; https://doi.org/10.3390/f13122106 - 9 Dec 2022
Cited by 2 | Viewed by 1682
Abstract
Snow cover is one of the most important factors affecting the regeneration and growth of shrubs in cold arctic and alpine ecosystems. In many of these cold regions, climate change in the last century is manifested not only in a rapid rise of [...] Read more.
Snow cover is one of the most important factors affecting the regeneration and growth of shrubs in cold arctic and alpine ecosystems. In many of these cold regions, climate change in the last century is manifested not only in a rapid rise of temperature, but also in an increase in winter precipitation. For instance, in the Ural Mountains, winter turned warmer and more humid during the past century, leading to higher snow accumulation. We investigated how the change trends in the cold season (November to March) climate conditions affected the recruitment of the shrub Juniperus sibirica Burgsd., the most widespread shrub conifer in mountains of this region where it is dominant in treeless areas. Specifically, we considered seven sites located in the Southern and Northern Urals that are subjected to lower and higher continentality, respectively. We assessed how juniper recruitment changed along altitudinal gradients going from the open forest to the alpine tundra and passing by the transition zone. We found that juniper shrubs recruited at higher elevations during the 20th century in most sites, with a rapid shrub encroachment into alpine tundra (shrubification) after the 1990s. This process was especially intensive in the last decades at the uppermost parts of convex slopes where the snowpack is shallow. We found positive associations between juniper recruitment and cold-season precipitation or temperature in the Northern and Southern Urals, respectively. Shrubification is following upward treeline shifts in the Southern Urals. Our findings indicate that juniper shrubs will tend to colonize sites with low snowpack depth if winter conditions keep warm and wet enough and the snowpack allows the effective protection of shrubs. Full article
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19 pages, 2952 KiB  
Article
Population Dynamics of Juniperus macropoda Bossier Forest Ecosystem in Relation to Soil Physico-Chemical Characteristics in the Cold Desert of North-Western Himalaya
by Dhirender Kumar, Daulat Ram Bhardwaj, Prashant Sharma, Bharti, Neeraj Sankhyan, Nadhir Al-Ansari and Nguyen Thi Thuy Linh
Forests 2022, 13(10), 1624; https://doi.org/10.3390/f13101624 - 3 Oct 2022
Cited by 6 | Viewed by 2154
Abstract
Juniperus macropoda is the only tree species of a cold desert ecosystem that is experiencing high anthropogenic pressure and has a poor regeneration status due to harsh environmental conditions. Due to the limited distribution of Juniperus macropoda in this region, the species have [...] Read more.
Juniperus macropoda is the only tree species of a cold desert ecosystem that is experiencing high anthropogenic pressure and has a poor regeneration status due to harsh environmental conditions. Due to the limited distribution of Juniperus macropoda in this region, the species have remained largely unexplored in terms of understanding the distribution pattern along the elevation and soil fertility gradients. Therefore, the current research was carried out along the elevational gradient, starting from the base line at 3000 m above sea level (m asl) asl with an elevational plot distance of 180 m. The study revealed that the average density of J. macropoda declined gradually from the first elevation range, i.e., 3000–3180 m asl onward, and extended up to the elevation range of 3900–4080 m asl. However, the average seedling and sapling densities were highest at mid-elevation and extended up to an elevation range of 4080–4260 m asl. The J. macropoda population formed a reverse J-shaped structure only up to 3540–3720 m asl. The maximum total biomass and carbon density were recorded in the lowest elevational range, and decreased subsequently. The primary soil nutrients under study decreased sharply along the elevational gradient. Seedling, sapling and tree distributions had a significantly positive relationship (p < 0.05) with available N, P, K, SOC, silt and clay contents and were negatively correlated (p < 0.05) with sand contents. The outcome of the study will form the basis for devising a plan for the management and conservation of J. macropoda forests. Full article
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13 pages, 2303 KiB  
Article
Heterogeneous Responses of Alpine Treelines to Climate Warming across the Tibetan Plateau
by Yafeng Wang, Daihan Li, Ping Ren, Shalik Ram Sigdel and Jesús Julio Camarero
Forests 2022, 13(5), 788; https://doi.org/10.3390/f13050788 - 19 May 2022
Cited by 7 | Viewed by 2441
Abstract
The Tibetan Plateau hosts a continuous distribution of alpine treelines from the Qilian Mountains to the Hengduan Mountains and the Himalaya Mountains. However, not much is known about the broadscale alpine treeline dynamics and their responses to climate warming across the Tibetan Plateau. [...] Read more.
The Tibetan Plateau hosts a continuous distribution of alpine treelines from the Qilian Mountains to the Hengduan Mountains and the Himalaya Mountains. However, not much is known about the broadscale alpine treeline dynamics and their responses to climate warming across the Tibetan Plateau. Herein, we collected a total of 59 treeline sites across different forest regions of the Tibetan Plateau and the related field data (i.e., upward advance magnitude, tree recruitment and height growth), expansion potential (i.e., elevational difference between the current treeline and the tree species line (EP)) and vegetation TI (an index of species interactions) from the published references. Site characteristics (e.g., elevation, slope and aspect) and the related environmental factors were used to analyze the relationships between treeline shifts and environmental variables. Despite increases in the recruitment and growth of trees at most treeline sites, alpine treeline positions showed heterogeneous responses to climate warming. Most treelines advanced over the last century, while some treelines showed long-term stability. EP was significantly and positively linked to the summer warming rate and treeline shifts, suggesting that the position of current tree species line is of crucial importance in evaluating treeline dynamics under climate change. In addition, warming-induced treeline advances were modulated by plant–plant interactions. Overall, this study highlighted the heterogeneous responses of regional-scale alpine treelines to climate warming on the Tibetan Plateau. Full article
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15 pages, 4075 KiB  
Article
Responses to Climate Change of Maximum Latewood Density from Larix speciosa Cheng et Law and Abies delavayi Franch. in the Northwest of Yunnan Province, China
by Guofu Deng, Mingqi Li, Zhixin Hao and Xuemei Shao
Forests 2022, 13(5), 720; https://doi.org/10.3390/f13050720 - 4 May 2022
Cited by 5 | Viewed by 1848
Abstract
Tree-ring density has been used for climate-response analysis and climate reconstruction for many species. However, our knowledge of wood density for the responses of different species to climate remains very limited and inconclusive. To determine the relationship between maximum latewood density (MXD) and [...] Read more.
Tree-ring density has been used for climate-response analysis and climate reconstruction for many species. However, our knowledge of wood density for the responses of different species to climate remains very limited and inconclusive. To determine the relationship between maximum latewood density (MXD) and climate for deciduous and evergreen coniferous species, MXD chronologies were developed from Larix speciosa Cheng et Law and Abies delavayi Franch. growing at 3200–3300 m a.s.l. in Gongshan county, northwestern Yunnan, in China. Significant positive correlations with late summer mean temperature were found for the MXD chronologies of both species. However, the highest correlation occurred in August–September for L. speciosa (r = 0.551, p < 0.01) and in September–October for A. delavayi (r = 0.575, p < 0.01), which may be associated with the physiological habits of trees. Linear model can describe relationships between late-summer temperature and MXD index for L. speciosa (MXD = 0.0506T8–9 − 0.0509, R2 = 30.3%) and A. delavay (MXD = 0.0317T9–10 + 0.4066, R2 = 33.0%). The composite chronology from the two species can reveal a late summer temperature (August−October) signal with the explained variance 32.2% for its response model. However, in dry areas and or at high altitudes close to upper tree line, the responses of wood densities to climate require further investigation for deciduous and evergreen coniferous species. Full article
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14 pages, 2988 KiB  
Article
Radial Stem Growth of the Clonal Shrub Alnus alnobetula at Treeline Is Constrained by Summer Temperature and Winter Desiccation and Differs in Carbon Allocation Strategy Compared to Co-Occurring Pinus cembra
by Walter Oberhuber, Gerhard Wieser, Fabio Bernich and Andreas Gruber
Forests 2022, 13(3), 440; https://doi.org/10.3390/f13030440 - 11 Mar 2022
Cited by 4 | Viewed by 1952
Abstract
Green alder (Alnus alnobetula) is currently the most expanding shrub species in the Alps. Because dense thickets impair tree establishment, understanding how climate affects shrub growth is essential for predictions of treeline dynamics. We evaluated ring width data from >50 A. [...] Read more.
Green alder (Alnus alnobetula) is currently the most expanding shrub species in the Alps. Because dense thickets impair tree establishment, understanding how climate affects shrub growth is essential for predictions of treeline dynamics. We evaluated ring width data from >50 A. alnobetula stems sampled at treeline on Mt. Patscherkofel (Central European Alps, Austria) to identify main climatic drivers and influence of climate warming on radial stem growth (RG). We also compared RG of A. alnobetula with RG of the co-occurring treeline conifer Swiss stone pine (Pinus cembra). We addressed our questions through calculation of response functions and evaluation of climate in years showing exceptional growth deviations. Response function analyses and evaluation of growth trends during 1991–2020 revealed that RG of A. alnobetula is significantly and directly related to summer temperatures. Precipitation in January also showed a direct relationship to RG, indicating effects of frost drought on RG. Surprisingly, nitrogen fixing A. alnobetula showed strikingly lower RG compared to P. cembra, and the latter also responded more strongly to the increase in summer temperature in the course of climate warming. We explain these findings by different carbon allocation strategies, i.e., preference of “vertical” stem growth in late successional P. cembra vs. favoring “horizontal” spread in the pioneer shrub A. alnobetula. Full article
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8 pages, 1361 KiB  
Opinion
Treeline-Quo Vadis? An Ecophysiological Approach
by Andreas Gruber, Walter Oberhuber and Gerhard Wieser
Forests 2022, 13(6), 857; https://doi.org/10.3390/f13060857 - 30 May 2022
Cited by 3 | Viewed by 1807
Abstract
At high elevation or latitude, the margin of the life-form tree is set by low temperature, with trees defined as upright woody species taller than 2–3 m. Globally, the temperature limit of the life-form tree occurs whenever the growing season mean soil temperature [...] Read more.
At high elevation or latitude, the margin of the life-form tree is set by low temperature, with trees defined as upright woody species taller than 2–3 m. Globally, the temperature limit of the life-form tree occurs whenever the growing season mean soil temperature declines to 6.7 ± 0.8 °C. Disturbance and human land use, however, can cause trees to be absent from the climatic treeline. After addressing definitions and concepts related to treeline ecophysiology and examining treeline structure and dynamics, the focus will be on future treeline developments with respect to climate, competition and land use change. Finally, changes in economic structure and land use within the treeline ecotone are outlined with respect to net ecosystem production and year-round evapotranspiration. Full article
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