Vegetation Shifts Research Articles

Enhanced mercury deposition in Arctic Alaskan lake sediments coincides with early Holocene hydroclimate shift.

Substantial amounts of mercury (Hg) are projected to be released into Arctic watersheds as permafrost thaws amid warmer and wetter conditions. This may have far-reaching consequences because the highly toxic methylated form of Hg biomagnifies rapidly in ecosystems. However, understanding how climate change affects Hg dynamics in permafrost regions is limited due to the lack of long-term Arctic Hg records. Using a 27-ka Hg sediment record from Burial Lake, northwestern Alaska, we examine how well-characterized temperature, precipitation, and vegetation shifts affected Hg mobilization in a catchment underlain by permafrost. During the Last Glacial Maximum (29.6-19.6ka), Hg concentrations (63±5μg/kg) and Hg flux (8.6±2.2μgm-2yr-1) remain relatively stable. Abrupt warming trends, starting at 17.6ka, do not coincide with Hg levels. After 15ka, the ecosystem transitions to shrub tundra, Hg concentrations (101.2μg/kg) peak at 14.2ka, while flux (5.3±1.3μgm-2yr-1) declines and stabilizes. At ~11ka, increased precipitation coincides with a 72% rise in Hg concentrations and a 32% increase in Hg flux compared to average Hg levels since 15ka. These results suggest that summer rainfall was the primary driver of Hg mobilization from the catchment, while the vegetation shift influenced lake sediment Hg concentrations. At 1990CE, peak Hg levels represent an 88% increase in Hg concentrations (196.3μg/kg) and a sixfold rise in Hg flux (38.1μgm-2yr-1) above background levels, underscoring the need for further research to understand Hg dynamics driven by anthropogenic Hg emissions and climate change.

Annotated review of the mammal fauna in the Chornobyl Biosphere Reserve as of 2023

The review of mammals recorded in the Chornobyl Radiation-Ecological Biosphere Reserve (established in 2016, covering 2273 of the 2600 km² area of the former exclusion zone) is carried out for the second time in the entire history of studies in the region. In addition to presenting a checklist of the local mammal fauna, the review details the changes that have taken place over the last 20 years. In total, 61 species have been recorded in the Reserve (compared to 49 in 2006), representing 7 orders and 19 families. Among them, 10–11 species are non-native, of which 5 were introduced in the last 25–70 years. The rest of the species are autochthonous. Nine species are considered to be phantom species, meaning that they are known from neighbouring areas but have not been found in the Reserve. Twenty-two species have protected status in Ukraine (Red Data Book of Ukraine, 2021), and 6 in Europe (IUCN Red List, 2024). The changes in the checklist of the Reserve’s mammal fauna have mainly resulted from more intense studies and using revised approaches. Research on bats alone has added nine species to the list of mammals. Additionally, feral domestic animals (cats, dogs, and cattle) have been included in the checklist as they have formed established wild populations. Only two species, the golden jackal and the European bison, arrived naturally in the Reserve for the first time. The abundance of most species shows significant long-term and seasonal fluctuations, influenced by climate change, disease, shifts in vegetation, wildfires, floods, intraspecies dynamics, and occasionally human activity. Certain species (lynx, Przewalski’s horse, and bear) continue to increase in number, while the red deer has shifted from being a non-abundant to a dominant species. At the same time, there is limited information on rare and conditionally non-abundant species as they often fall outside the scope of research due to the difficulty of their study. This consideration is not reasonable as those species constitute a substantial portion of the checklist, and many of them are protected species. Nevertheless, the current state of the mammal fauna demonstrates the positive impact of nature conservation and the stable development of autochthonous populations, reinforcing the view that the Chornobyl Radiation-Ecological Biosphere Reserve is a highly valuable wildlife sanctuary in both Ukraine and Europe.

Land Cover Change and Habitat Fragmentation in Protected Landscape Areas: Analyzing the Impact of Ecological Management on Environmental Sustainability and Species Diversity

Habitat fragmentation due to land cover change is a major threat to biodiversity conservation in protected areas. It therefore becomes important to study the role of the main drivers of habitat fragmentationclimate change, human action and natural disturbancesand the efficacy of ecological management in mitigating these. With the help of GIS (geographical information system) and field surveys, the study tracks land cover dynamics through projected changes in vegetation types, soil erosion and shifts in flora and fauna in five major ecological zones: the Amazon rainforest, Sahara desert, Great Plains of North America, Gobi Desert and the Himalayas. Climate variability and human intervention are found to be the most disruptive factors for habitat integrity, leading to biodiversity loss and population isolation. Adaptive management practices like reforestation, wildlife corridors and pro-environmental land-use policies are seen as having a positive impact on increasing connectivity, maintaining genetic diversity and ensuring ecological resilience. Tailored management actions for the buffer zones in protected areas are also seen as essential for ecological stability and preserving species interactions. The paper presents a useful set of actionable measures for conservation, ensuring an economically-driven ecological approach that focuses on preserving biodiversity through ecosystem-specific, adaptive management.

Ecohydrological Response of a Tropical Peatland to Rainfall Changes Driven by Intertropical Convergence Zone Variability

ABSTRACTAimTropical peatlands are globally significant carbon stores, increasingly threatened by human activities and climate change. However, their ecohydrological responses to shifting water availability remain poorly understood. In this study, we investigate the connections between climate change, hydrology and vegetation dynamics in a coastal tropical peatland in Panama, aiming to understand the effects of future drying on peatland dynamics.LocationBocas del Toro, Panama (9°22′54″N, 82°21′59″W).TaxonAngiosperms.MethodsHigh‐resolution multiproxy palaeoecological data, including pollen and plant macrofossils (vegetation), testate amoebae (water‐table depth) and physical peat properties, are used to explore the relationships between climate change, hydrology and vegetation in a coastal tropical peatland over the past 700 years. Downscaled climate simulations are integrated with this process‐based understanding to project the likely future responses of this coastal peatland to climate change.ResultsWe identify a clear connection between precipitation variability, driven by shifts in the Intertropical Convergence Zone and water‐table dynamics, which subsequently influence changes in the peatland vegetation mosaic. Historical drier periods are marked by the expansion of shrub communities into the open peatland plain.Main ConclusionsPalaeoecological studies incorporating climate and hydrological proxies are essential for understanding both recent and future ecohydrological dynamics of tropical peatlands. Our findings suggest that in response to future climate change, water tables will lower and shrub communities will expand due to rising temperatures and reduced precipitation. Additionally, future sea‐level rise, combined with declining rainfall, may result in seawater intrusion and significant vegetation shifts in coastal tropical peatlands.

Dynamic Shifts in Climate, Vegetation, and Cultural Heritage: A 50-Year Study of Wadi Al Arbaein, South Sinai, Egypt

Dynamic Shifts in Climate, Vegetation, and Cultural Heritage: A 50-Year Study of Wadi Al Arbaein, South Sinai, Egypt

Unveiling hidden diversity: Phylogenomics of neotomine rodents and taxonomic implications for the genus Peromyscus

Neotomine rodents (Cricetidae, Neotominae) represent one of the most commonly encountered and diverse group of rodents in North America, yet phylogenetic relationships within this group remain uncertain. This subfamily is known for its rapid evolution, adding more complexity to our efforts to unravel their evolutionary history. The main debate revolves around the recognition of the genus Peromyscus as monophyletic or paraphyletic due to its relationship with other genera such as Habromys, Megadontomys, Podomys, Neotomodon, and Osgoodomys. Here, we aim to resolve phylogenetic relationships within Neotominae, to further explore their evolutionary history and taxonomic boundaries. We used target capture and high-throughput sequencing of complete mitogenomes and thousands of genome-wide ultraconserved elements loci (UCEs). Our comprehensive analyses encompassed 53 species of Neotominae spanning 12 previously described genera, along with one yet-undescribed genus. We also investigated 12 out of the 13 species groups within Peromyscus. Our analyses, including Maximum Likelihood and Bayesian Inference with both mitogemomes and UCEs, as well as the coalescent species-tree-based approach with UCEs, consistently recovered concordant and well-resolved phylogenies with high levels of nodal support. We identified seven main clades within Neotominae that could potentially be recognized at the generic level, mostly to categorize the genus Peromyscus as a monophyletic group, including one species group within “Peromyscus”. Furthermore, our divergence dating estimates place the crown age of Neotominae to be around the late Miocene at ca. 7.9 – 10.7 mya. While generic level diversification continued through the Pliocene, species level diversification predominantly occurred during the late Pliocene, extending through the Pleistocene and Holocene. These epochs have been recognized as periods with significant changes in flora and fauna, driving ecological transformations on a global scale. We hypothesized that climatic and vegetation shifts during the Neogene and Quaternary, coupled with geological events, topographical features, and the presence of biogeographical corridors played a pivotal role in the speciation and diversification of Neotominae. Recognizing the importance of generating genomic-scale data coupled with a broad taxonomic sampling, our study, for the first time, offers resolution of the relationships among the main lineages of Neotominae. We expect that the phylogeny presented here will serve as a foundational resource for future systematic and evolutionary studies. This includes facilitating a proper comprehensive taxonomic revision of the group and the formal description and naming of new genera.

Vegetation changes of Lushan, China between 1959 and 2020 based on pollen data

Both climatic change and human activity are currently driving the dynamic of vegetation, which may vary from region to region. On Lushan Mountain, located in eastern China, the subtropical secondary forests during the natural succession endure the pressure from ongoing climate warming on the one hand. They are influenced by anthropogenic disturbance on the other hand for recent decades. Previously, palynological research has discovered that the pollen assemblages from surface soil samples on Lushan reflect the characteristics of local vegetation. Here, we did a comparative study by using pollen analysis to investigate the vegetation changes of Lushan from 1959 to 2020. We compared the composition of pollen assemblages obtained in 1959 with that in 2020 along different altitudes. Further, the biomisation method was employed to discover the changes of different vegetation types, which were reflected by the pollen-based reconstructed biomes. Meanwhile, the temporal beta diversity analysis was used to extract the sites: that experienced significant vegetation shift and the most important taxa change. Results showed that the pollen composition over the past 60 years on Lushan had altered remarkably. The vegetation shifted at all altitudes. The current vegetation pattern of Lushan: evergreen broadleaved forest at low elevation, temperate deciduous broadleaved forest at middle elevation and cool mixed forest at high elevation, is the successional consequence of the past 60 years. The forces driving the vegetation dynamics might be from multiple sources. However, human disturbance seems to play quite an important role during forest succession. Our study is potentially useful both for paleoecological reconstructions and wider understanding of current climate change that are relevant to subtropical forests of Asia.

Mechanisms of rapid plant community change from the Miocene Succor Creek flora, Oregon and Idaho (USA).

The fossil record of the U.S. Pacific Northwest preserves many Middle Miocene floras with potential for revealing long-term climate-vegetation dynamics during the Miocene Climatic Optimum. However, the possibility of strong, eccentricity-paced climate oscillations and concurrent, intense volcanism may obscure the signature of prevailing, long-term Miocene climate change. To test the hypothesis that volcanic disturbance drove Middle Miocene vegetation dynamics, high-resolution, stratigraphic pollen records and other paleobotanical data from nine localities of the Sucker Creek Formation were combined with sedimentological and geochemical evidence of disturbance within an updated chronostratigraphic framework based on new U-Pb zircon ages from tuffs. The new ages establish a refined, minimum temporal extent of the Sucker Creek Formation, ~15.8 to ~14.8 Ma, and greatly revise the local and regional chronostratigraphic correlations of its dispersed outcrop belt. Our paleoecological analysis at one ~15.52 Ma locality reveals two abrupt shifts in pollen spectra coinciding with the deposition of thick ash-flow tuffs, wherein vegetation dominated by Cupressaceae/Taxaceae, probably representing a Glyptostrobus oregonensis swamp, and upland conifers was supplanted by early-successional forests with abundant Alnus and Betula. Another ephemeral shift from Cupressaceae/Taxaceae swamp taxa in favor of upland conifers Pinus and Tsuga correlates with a shift from low-Ti shale to high-Ti claystone, suggesting a link between altered surface hydrology and vegetation. In total, three rapid vegetation shifts coincide with ash-flow tuffs and are attributed to volcanic disturbance. Longer-term variability between localities, spanning ~1 Myr of the Miocene Climatic Optimum, is chiefly attributed to eccentricity-paced climate change. Overall, Succor Creek plant associations changed frequently over ≤105 years timespans, reminiscent of Quaternary vegetation records. Succor Creek stratigraphic palynology suggests that numerous and extensive collection of stratigraphically controlled samples is necessary to understand broader vegetation trends through time.

Climate Regulates the Effects of Abrupt Vegetation Shifts on Soil Moisture in the Loess Plateau, China

Climate Regulates the Effects of Abrupt Vegetation Shifts on Soil Moisture in the Loess Plateau, China

Short‐term vegetation shifts in an alpine grassland under current and simulated climate change

AbstractQuestionsRecent years have been characterised by extreme climate conditions. Given that high elevations are undergoing enhanced warming and alpine ecosystems provide important services, we ask: Have alpine grasslands experienced rapid vegetation changes over the last five years? Which species are more sensitive to warmer and/or drier conditions?LocationCarex curvula grassland in the southern Alps (Italy).MethodsSpecies cover was visually estimated in 20 permanent plots, including both control and climate‐manipulated plots, during the period 2017–2022. Climate manipulations, that is, increased temperature and/or reduced precipitation during the snow‐free period, started from 2018. Principal component analysis, redundancy analysis and generalised least‐squares or linear mixed‐effect models were employed to investigate variations in species assemblage and species‐specific responses.ResultsDetectable changes were found in species cover over time and between climate manipulations, with warmed plots experiencing greater shifts in species composition compared to controls. At the species level, however, both increases and decreases in cover were observed over time, with only two non‐dominant forbs, Phyteuma hemisphaericum and Leucanthemopsis alpina, showing either increased cover in warmed plots or lower cover values under drier conditions. No treatment effects and the lowest variation across years were found for the two dominant species (the sedge Carex curvula and the forb Alchemilla pentaphyllea) which together make up more than 70% of vascular plant cover. Despite the short time period investigated, a major cover reduction was observed in all treatments for some snowbed species.ConclusionsThe plant species assemblage of the target alpine grassland was found to be sensitive to short‐term manipulations simulating future climate changes, with individual species exhibiting idiosyncratic responses to manipulations and different cover dynamics over time. A decline in some snowbed specialists already seems to be taking place even in these late‐successional grasslands — at a rate likely to increase in the future — with the majority of other vascular species exhibiting greater resistance to changing environmental conditions.

Vegetation and environmental changes on the Northeast China Plain during warm periods since MIS 3

Understanding past terrestrial ecosystem responses to climate changes is vital for future predictions, but research in densely populated plains is limited due to insufficient materials. This study focuses on vegetation and environmental changes in the Northeast China Plain since Marine Isotopic Stage (MIS) 3 using pollen analysis from core WCZK03. The findings reveal significant shifts in vegetation that correspond to climatic events. During MIS 3 (52–29 cal ka BP), the region was predominantly a lake environment with vegetation transitioning from grassland dominated by Poaceae, Chenopodiaceae and Artemisia to conifer-broadleaf mixed forests as the climate ameliorated. The Last Glacial Maximum (29–17 cal ka BP) was characterized by loess deposits, followed by drought-tolerant grassland (17.0–11.3 cal ka BP) dominated by Artemisia and Chenopodiaceae in the plain. The onset of the Holocene witnessed the expansion of conifer and broad-leaved deciduous forests in hilly areas and the retreat of grassland in the plain. The sedimentary sequence shows transitions from fluvial-lacustrine deposits to loess-like and black soil deposits, showing significant environmental changes. This study suggests that changes in vegetation on the Northeast China Plain were closely related to regional climate patterns and were more responsive to climate changes than the surrounding mountainous areas.

Warming and disturbances affect Arctic-boreal vegetation resilience across northwestern North America.

Rapid warming and increasing disturbances in high-latitude regions have caused extensive vegetation shifts and uncertainty in future carbon budgets. Better predictions of vegetation dynamics and functions require characterizing resilience, which indicates the capability of an ecosystem to recover from perturbations. Here, using temporal autocorrelation of remotely sensed greenness, we quantify time-varying vegetation resilience during 2000-2019 across northwestern North American Arctic-boreal ecosystems. We find that vegetation resilience significantly decreased in southern boreal forests, including forests showing greening trends, while it increased in most of the Arctic tundra. Warm and dry areas with high elevation and dense vegetation cover were among the hotspots of reduced resilience. Resilience further declined both before and after forest losses and fires, especially in southern boreal forests. These findings indicate that warming and disturbance have been altering vegetation resilience, potentially undermining the expected long-term increase of high-latitude carbon uptake under future climate.

Influence of climate, weather and floral associations on pollinator community composition across an elevational gradient

Insect pollinators, which are ectothermic, are especially sensitive to abiotic conditions, which often drive predictable patterns of pollinator species turnover along environmental gradients. However, pollinator activity is also reliant on suitable biotic conditions, such as the presence of host plants. High‐elevation environments provide a useful setting to examine the relative contribution of abiotic and biotic factors in shaping species interactions as they are often characterised by strong environmental gradients over short geographic distances. Here, we examined pollination interaction networks across an elevational gradient from 930–2000 m a.s.l. in southern Australia, to determine the underlying patterns of pollinator activity and their interactions with flowers. Interaction frequency of Diptera increased at high elevations, while interaction frequency of Hymenoptera and Coleoptera decreased. We provide evidence that this elevational pattern of activity is partly driven by floral associations, with interactions dominated by Hymenoptera‐attracting plant families at lower elevations (Proteaceae, Fabaceae) and a Diptera‐attracting family at high elevation (Asteraceae). Pollinator activity was also influenced by weather conditions, with reduced activity for all three orders at lower temperatures, and Diptera active across the broadest range of temperature, humidity and wind conditions. We suggest that changes across elevation gradients in pollinator community composition are driven by both direct responses to abiotic conditions such as temperature, as well as the elevational distribution patterns of associated flowering plants. Despite these distinct shifts in composition of the pollinator assemblage with elevation, pollination network structure was stable across the elevational gradient, with moderate levels of specialisation and low levels of connectance and nestedness present across the gradient. By considering both abiotic conditions and biotic processes, our results provide insight for predicting the impacts of upslope vegetation shifts on pollinator communities in the face of climate change.

Analysis of changes before and after forest fires with LAI, NDVI and ET time series: Focusing on major forest fires in Korea

This study investigates the changes caused by forest fires and the following recovery processes, targeting four forest fire sites in Korea. The time series of two vegetation indices, leaf area index (LAI) and normalized difference vegetation index (NDVI) are investigated along with evapotranspiration (ET) time series for the study objectives. The analysis results show that LAI is most sensitive to burn severity and burned area with its change ranging from 40 % to 70 %, while the changes of NDVI and ET remain 30 % and 20 %, respectively, regardless of forest fire sites. The recovery time from forest fire also varies according to indices: the recovery time is estimated to be about 15 years when considering LAI and NDVI, while just 5 years when considering ET. Overall, LAI seems better to analyze the change in vegetation before and after forest fires. Different vegetation shift patterns after the forest fire are also noticed, mostly from evergreen needleleaf trees to deciduous broadleaf trees. However, it is also found that bad soil fertility condition and artificial afforestation help to maintain the evergreen needleleaf trees after the forest fire.

Historical vegetation shifts in southeastern Amazonia: Unraveling ecotone dynamics in the Carajás region over the last ∼14000 cal yr BP

This study investigates the Pleistocene–Holocene transition in Serra Leste, a highly endangered southeastern Amazonian ecotone, with a focus on the lake-filling process, climate changes, and potential consequences to forest and savanna dynamics. The lake's development began at approximately 14000 cal yr BP, resulting from the collapse of the fractured lateritic crust. Sedimentation patterns and geochemical, palynological and micro-charcoal proxies reveal shifts in detrital input and redox conditions, forest/savanna areas, and local and regional fire events, indicating a highly dynamic environmental history. The evolution of the lake is characterized by initial deltaic lobe deposition and forest dominance, followed in the Middle Holocene by sedimentary gaps or reduced detrital input; woody vegetation dominance, with a notable shift toward a more open landscape; and savanna and semideciduous dry forest, accompanied by a decrease in ombrophilous forests. A resurgence in arboreal elements recorded in the Late Holocene indicates an expansion of ombrophilous forests under wetter climate conditions and the establishment of a more continuous forest matrix, with the presence of likely “hyperdominant” taxa. Frequent local fire events and the occurrence of temporarily correlated archeological sites in the Serra Leste region suggest the influence of ancient indigenous communities on vegetation changes during the Late Holocene.

Increasing evapotranspiration in peatlands from the monsoon regions of East China with the rapid warming during the early Holocene

Peatlands are one of the largest natural terrestrial carbon store, which evolve closely with the hydrological functioning. Evapotranspiration serves as a nexus of the carbon and water cycles in peatlands. Its long-term changes in the geological past are essential to gain a complete understanding of its response to global warming. Here, the evapotranspiration changes in peatlands from the monsoon regions of East China during the significant warming period of ∼ 11.5–10 ka in the Early Holocene are investigated, based on a new leaf wax δD record from the Hani peatland in Northeast China along with the previously reported representative records across monsoonal eastern China. All of the leaf wax δD records exhibit less depleted values during this episode, which follow neither with the changes in precipitation isotopes nor the vegetation compositions. They are thus interpreted as enhanced evapotranspiration. Further comprehensive comparisons based on paleoenvironmental records reveal that evapotranspiration changes are highly sensitive to rising temperatures but are intricately linked with precipitation variations. The strong evapotranspiration appears to be potentially linked to water table drawdown on longer timescales, which further actively interacts with peat-forming plants. Our results suggest that evapotranspiration is expected to increase in peatlands as the climate warms, but its changes might be complicated by accompanying hydrological and vegetational shifts.

Feedbacks Regulating the Salinization of Coastal Landscapes.

The impact of saltwater intrusion on coastal forests and farmland is typically understood as sea-level-driven inundation of a static terrestrial landscape, where ecosystems neither adapt to nor influence saltwater intrusion. Yet recent observations of tree mortality and reduced crop yields have inspired new process-based research into the hydrologic, geomorphic, biotic, and anthropogenic mechanisms involved. We review several negative feedbacks that help stabilize ecosystems in the early stages of salinity stress (e.g., reduced water use and resource competition in surviving trees, soil accretion, and farmland management). However, processes that reduce salinity are often accompanied by increases in hypoxia and other changes that may amplify saltwater intrusion and vegetation shifts after a threshold is exceeded (e.g., subsidence following tree root mortality). This conceptual framework helps explain observed rates of vegetation change that are less than predicted for a static landscape while recognizing the inevitability of large-scale change.

Large grazers suppress a foundational plant and reduce soil carbon concentration in eastern US saltmarshes

Abstract Large grazers modify vegetated ecosystems and are increasingly viewed as keystone species in trophic rewilding schemes. Yet, as their ecosystem influences are context‐dependent, a crucial challenge is identifying where grazers sustain, versus undermine, important ecosystem properties and their resilience. Previous work in diverse European saltmarshes found that, despite changing plant and invertebrate community structure, grazers do not suppress below‐ground properties, including soil organic carbon (SOC). We hypothesised that, in contrast, eastern US saltmarshes would be sensitive to large grazers as extensive areas are dominated by a single grass, Spartina alterniflora. We predicted that grazers would reduce above‐ and below‐ground Spartina biomass, suppress invertebrate densities, shift soil texture and ultimately reduce SOC concentration. We tested our hypotheses using a replicated 51‐month large grazer (horse) exclusion experiment in Georgia, coupled with observations of 14 long‐term grazed sites, spanning ~1000 km of the eastern US coast. Grazer exclusion quickly led to increased Spartina height, cover and flowering, and increased snail density. Changes in vegetation structure were reflected in modified soil texture (reduced sand, increased clay) and elevated root biomass, yet we found no response of SOC. Large grazer exclusion also reduced drought‐associated vegetation die‐off. We also observed vegetation shifts in sites along the eastern US seaboard where grazing has occurred for hundreds of years. Unlike in the exclusion experiment, long‐term grazing was associated with reduced SOC. A structural equation model implicated grazing by revealing reduced stem height as a key driver of reduced soil organic carbon. Synthesis: These results illustrate the context dependency of large grazer impacts on ecosystem properties in coastal wetlands. In contrast to well‐studied European marshes, eastern US marshes are dominated and structured by a single foundational grass species resulting in vegetation and soil properties being more sensitive to grazing. Coastal systems characterised by a single foundation species might be inherently vulnerable to large grazers and lack resilience in the face of other disturbances, underlining that frameworks to explain and predict large grazer impacts must account for geographic variation in ecosystem structure.

Predicting plants in the wild: Mapping arctic and boreal plants with UAS-based visible and near infrared reflectance spectra

Biophysical changes in the Arctic and boreal zones drive shifts in vegetation, such as increasing shrub cover from warming soil or loss of living mat species due to fire. Understanding current and future responses to these factors requires mapping vegetation at a fine taxonomic resolution and landscape scale. Plants vary in size and spectral signatures, which hampers mapping of meaningful functional groups at coarse spatial resolution. Fine spatial grain of remotely sensed data (<10 cm pixels) is often necessary to resolve patches of many Arctic and boreal plant groups, such as bryophytes and lichens, which are significant components of terrestrial vegetation cover. Separation of co-occurring small vegetation patches in images also requires high spectral resolution. Our goal here was to test the capabilities of UAS-based imaging spectroscopy for mapping plant functional types (PFT) using high spatial and spectral resolution data over Arctic and boreal vegetation at four sites in central Alaska. We then tested several Machine and Deep learning models of PFT cover using the reflectance spectra. The best models were very simple, balancing both bias (overfitting caused by imbalance sample sizes) and variance (fit to the independent validation data), explaining > 50 % of the independent ground cover estimation and > 84 % accuracy in estimating validation pixels. We explored the impact of spectral resolution on PFT mapping by including vegetation indices and a gradient of narrow (5 nm) to wide (50 nm) band features in our classification models across. Vegetation indices were the most important predictors for classifying PFTs, while including band features improved models, with narrow and wide bandwidths having similar importance but models with wide bandwidths performing slightly better. We conclude that Arctic and boreal PFT reflectance can be pooled across sites for mapping with relatively few labeled pixels. Underfit, simple algorithms outperformed deep learning, at least with these small sample sizes, in classifying PFTs by balancing bias and variance. Future work should aim to increase the number of labeled pixels and the detail of labels to further improve mapping taxonomic precision.

Fire drives major Holocene vegetation shifts between subtropical and Mediterranean‐type ecosystems: a case study from a biodiversity hotspot in South Africa

Fire plays a pivotal role in driving ecological shifts between Mediterranean‐type vegetation and subtropical ecosystems in South Africa. This study investigates long‐term environmental dynamics and ecological regime changes at the Mediterranean‐type vegetation /subtropical boundary using a 6000‐year palaeoecological sequence from the Baviaanskloof – a region of South Africa characterized by high levels of biodiversity and climate dynamism. Combining fossil pollen and microcharcoal data from a rock hyrax Procavia capensis midden, we analyse vegetation responses to environmental changes. Our findings reveal that Mediterranean‐type vegetation resilience prevailed until ca 2800 cal year BP when a major fire event triggered a transition to a subtropical thicket‐dominated environment. This abrupt ecological turnover underscores the significance of fire as a major driver of vegetation change at the Mediterranean‐type vegetation /subtropical boundary. Our study emphasizes the vulnerability of Mediterranean‐type vegetation ecosystems to global environmental change, suggesting potential implications for similar biome boundaries worldwide. By integrating multi‐proxy palaeoecological evidence, we gain insights into the resilience and vulnerability of these ecosystems, aiding in understanding future responses to climate change scenarios.