Vegetation Shifts Research Articles

Paleoecology of vegetation changes associated with a prehistoric earthquake at Serpentine Fen, southwestern British Columbia, Canada

A sedimentary exposure near the mouth of Serpentine River, about 25 km southeast of Vancouver, British Columbia, records evidence of a large earthquake that happened about 2000 years ago. The evidence includes sand dykes injected into late Holocene peat and mud. Vegetation changes based on pollen analysis and radiocarbon-dated wood match sedimentary changes at the Serpentine Fen site. A shift from herbaceous to woody peat is matched by a dramatic peak (∼45%) in pollen of Myrica shrubs, indicating uplift and a vegetation shift to drier shrubland from fen, also incorporating detrital spruce wood (Picea). At the top of the woody peat, Myrica pollen disappears and intertidal mud with Triglochin-type pollen increases, indicating subsidence and establishment of an intertidal environment. The section above the woody peat shows increasing amounts of halophyte pollen, especially Chenopodiaceae (or Amaranthaceae) which reaches values up to 60%, and scattered dinoflagellate cysts, indicative of a continued tidal influence. The combined evidence of uplift and subsidence over a short interval is rare at most sites in south-coastal British Columbia.

Cretaceous climate change evidenced in the Senegalese rock record, NW Africa

Climate change directly impacts the source, mode and volume of sediment generation which can be observed in the rock record. To accurately model source to sink systems, in addition to hinterland geology, tectonics and transport distance, a thorough comprehension of the climate is essential. In this study we evaluate the role of climate on Cretaceous sediment delivery into the Senegal Basin, NW Africa, using data recorded from extensive sampling of basinal sediments. This is achieved through the mineralogical characterisation by X-ray diffraction and 146Nd/144Nd and 86Sr/88Sr isotopic analyses, which are correlated against existing, climate, tectonic and oceanographic models.Examples of climatic indicators include the change from predominantly smectitic deep marine basinal-clays recorded from the Cretaceous in DSDP wells 367 and 368 to clays with increased illite and kaolinite content, observed during the Albian and Cenomanian-Turonian, interpreted to be representative of higher humidity following the kaolinisation of hinterland source-rocks. Another climate indicator is the observation of palygorskite in deep-marine sediments, noted to be indicative of ocean anoxia related to the authigenesis of marine-smectite, a product of warm saline bottom waters and increased abundancy of silicon. The increase in salinity is interpreted to be a biproduct of elevated temperatures throughout the Cenomanian and increased denudation of the North Atlantic circumjacent continental evaporite-belts. Increase in silicon (biogenic) is related to a result of ocean-wide mass extinction of foraminifera during OAE2 triggered by the eruption of the Caribbean large igneous province.The results suggest that Cretaceous climate evolution of Senegal can be divided into four stages: 1. Berriasian-Barremian; an arid-period with monsoonal weather producing modest fluvial systems restricted to coastal regions. 2. Aptian-Albian; the establishment of a paleo-Intertropical Convergence Zone began to increase global temperature and humidity as recognised by the increase in kaolinite content. 3. Cenomanian-Turonian; the Cretaceous Thermal Maximum hothouse period incurring exceptional temperatures and humidity. This is represented as an antithetical shift in clay mineralogy from chlorite-illite to smectite-kaolinite throughout most of the onshore and nearshore basinal sediments. 4. Coniacian-Maastrichtian; transitional from tropical-to-tropical swamp-like conditions evidenced by increased onshore basin sediment capture and a shift in vegetation to aquatic-fern species.The impact of climate change throughout the Cretaceous produced dynamic shifts in both river size and source-catchment, witnessing exception rates of denudation during the hotter and more humid periods, which climaxed during the Cenomanian and Turonian as a result of the Cretaceous Thermal Maximum. This eroded sediment was deposited in both the onshore and offshore basins during the mid-late Cretaceous but became increasingly restricted to the onshore segment of the basin during the Late Cretaceous.

Investigating the spatio-temporal pattern evolution characteristics of vegetation change in Shendong coal mining area based on kNDVI and intensity analysis

Alterations in vegetation cover serve as a significant indicator of land ecology. The Shendong Coal Mining Area, being the largest coal base globally, holds significant importance for national energy security. Moreover, it has gained recognition for its environmentally conscious approach to coal mining, characterized by the simultaneous implementation of mining activities and effective governance measures. In order to assess the ongoing vegetation recovery and the temporal changes in vegetation within the Shendong Coal Mining Area, we initially utilized Landsat TM/ETM+/OLI remote sensing data. Using the Google Earth Engine (GEE), we developed a novel kernel-normalized vegetation index (kNDVI) and subsequently generated a comprehensive kNDVI dataset spanning the years 2000 to 2020. In addition, the Sen (Theil-Sen median) trend analysis method and MK (Mann-Kendall) test were utilized to examine the temporal trends over a span of 21 years. Furthermore, the Hurst exponent model was employed to forecast the persistent changing patterns of kNDVI. The utilization of the intensity analysis model was ultimately employed to unveil the magnitude of vegetation dynamics. The findings indicated a notable positive trend in the overall kNDVI of vegetation within the study area. In relation to the analysis of changing trends, the vegetation in the region underwent a slight improvement from 2000 to 2010, followed by a significant improvement from 2010 to 2020. During this transition period, a total of 289.07 km2, which represents 32.36% of the overall transition area, experienced a shift in vegetation. The predictive findings from the Hurst model indicate that while the majority of areas within the mining region will exhibit an upward trend in vegetation growth, there will be certain areas that will demonstrate a decline. These declining areas account for 39.08% of the total transition area. Furthermore, the intensity analysis results reveal notable disparities in the characteristics of vegetation growth and evolution between the periods of 2000-2010 and 2010-2020. Throughout the entirety of the transformation process, the transition from slight improvement to significant improvement prevails in terms of both relative intensity and absolute intensity, surpassing alternative transformation processes. Various trend transitions display diverse intensity characteristics that adhere to the overarching principles governing shifts in vegetation growth. Furthermore, the utilization of the intensity analysis framework and intensity spectrum employed in this study demonstrates their efficacy in elucidating the temporal dynamics of vegetation changes. Furthermore, this study plays a pivotal role in the surveillance and assessment of the efficacy of ecological restoration in mining regions. It carries substantial implications for comparable land ecological restoration efforts in mining and reclamation, thereby furnishing a theoretical foundation.

A meta-analysis of peatland microbial diversity and function responses to climate change

Climate change threatens the capacity of peatlands to continue storing carbon (C) belowground. Microorganisms are crucial in regulating the peatland C sink function, but how climate change affects the richness, biomass and functions of peatland microbiomes still remains uncertain. Here, we conducted a global meta-analysis of the response of peatland bacterial, fungal and micro-eukaryote communities to climate change by synthesizing data from 120 climate change experiments. We show that climate drivers such as warming, drought and warming-induced vegetation shift strongly affect microbial diversity, community composition, trophic structure and functions. Using meta-analytic structural equation modelling, we developed a causal understanding among the different strands of microbial properties. We found that climate drivers influenced microbial metabolic rates, such as CO2 fixation and respiration, methane production and oxidation, directly through physiological effects, and indirectly, through microbial species turnover and shifts in the trophic structure of microbial communities. In particular, we found that the response of microbial CO2 fixation increased for each degree in air temperature gained, while the response of microbial CO2 respiration tended to decline. When extrapolated at the global peatland scale using the CMIP6 model under the SSP5-8.5 scenario, our findings suggest that the increasingly positive response of microbial CO2 fixation to temperature anomalies in northern latitudes might compensate to some extent for the possible loss of C from microbial CO2 respiration, possibly allowing peatlands to remain C sinks on long-term. Our findings have crucial implications for advancing our understanding of carbon-climate feedback from peatlands in a warming world.

Source or decomposition of soil organic matter: what is more important with increasing forest age in a subalpine setting?

Afforestation has been the dominant land-use change in the Swiss Alps during the last decades which has not only the potential to increase soil organic carbon sequestration, but it has also the potential to alter soil organic matter (SOM) dynamics through the vegetation shift and change in organic matter (OM) input into soils. The effects of afforestation on SOM dynamics, however, are still not fully understood as specific sources of OM and modifications of soil processes influencing decomposition and preservation remain largely unknown on alpine to subalpine slopes. Within this study we aimed to identify the potential sources and the decomposition of OM in a subalpine afforestation chrono-sequence (0–130 years) with Norway spruce (Picea abies L.) on a former pasture by using a multi-proxy molecular marker approach. We observed that leaf-derived OM plays an essential role in the pasture areas, while root-derived OM only plays a minor role in pasture and forest areas. Needle-derived OM represents the dominant source of SOM with increasing forest age, while understory shrubs and moss also contribute to the OM input in younger forest stand ages. However, needle litter and buildup of organic layers and subsequently less input of fresh OM from organic horizons to mineral soil can result in increased OM decomposition in mineral soils rather than contributing to additional SOM stabilization in mineral soils. This was most pronounced in the oldest forest stand (130-year-old) in the investigated afforestation sequence, particularly in deeper soil horizons (10–45 cm). Thereby, our study provides new insights into SOM dynamics following afforestation, especially with respect to the long-term SOM sequestration potential of afforestation of subalpine pasture soils.

Soil organic carbon stocks did not change after 130 years of afforestation on a former Swiss Alpine pasture

Abstract. Soil organic matter (SOM) plays an important role in the global carbon cycle, especially in alpine ecosystems. However, ongoing forest expansion in high-elevation systems potentially alters SOM storage through changes in organic matter (OM) inputs and microclimate. In this study, we investigated the effects of an Picea abies L. afforestation chrono-sequence (0 to 130 years) of a former subalpine pasture in Switzerland on soil organic carbon (SOC) stocks and SOM dynamics. We found that SOC stocks remained constant throughout the chrono-sequence, with comparable SOC stocks in the mineral soils after afforestation and previous pasture (SOC forest40 = 11.6 ± 1.1 kg m−2, SOC forest130 = 11.0 ± 0.3 kg m−2 and SOC pasture = 11.5 ± 0.5 kg m−2). However, including the additional carbon of the organic horizons in the forest, reaching up to 1.7 kg m−2 in the 55-year old forest, resulted in an increase in the overall SOC stocks following afforestation. We found that the soil C:N ratio in the mineral soil increased in the topsoil (0–5 cm) with increasing forest stand age, from 11.9 ± 1.3 in the pasture to 14.3 ± 1.8 in the 130-year old forest. In turn, we observed a decrease in the soil C:N ratio with increasing depth in all forest stand ages. This suggests that litter-derived organic matter (C:N from 35.1 ± 1.9 to 42.4 ± 10.8) is likely to be incorporated and translocated from the organic horizon to the mineral topsoil (0–10 cm) of the profiles. Due to the high root C:N ratio (pasture 63.5 ± 2.8 and forests between 54.7 ± 3.9 and 61.2 ± 2.9), particulate root-derived organic matter seems to have a rather small effect on forest soil C:N ratios, as well as on SOC accumulation in the mineral soil. These results suggest that, although afforestation does not change the SOC stock in the mineral soil, there is an apparent alteration in the SOM dynamics through changes in the litter composition caused by the vegetation shift. We conclude that, at our study site, spruce afforestation on a former subalpine pasture does not change the total SOC stock and that, consequently, there is no additional SOC sequestration on a decadal to centennial scale.

Climate Change Habitat Model Forecasts for Eight Owl Species in the Southwestern US.

The high-resolution forecasting of vegetation type shifts may prove essential in anticipating and mitigating the impacts of future climate change on bird populations. Here, we used the US Forest Service Ecological Response Unit (ERU) classification to develop and assess vegetation-based breeding habitat profiles for eight owl species occurring in the foothills and mountains of the Southwestern US. Shifts in mapped habitat were forecast using an ecosystem vulnerability model based on the pre-1990 climate envelopes of ERUs and the Intergovernmental Panel on Climate Change's (IPCC) A1B moderate-emission scenario for the future climate. For five of the eight owl species, the regional breeding habitat extent was projected to decline by at least 60% by 2090. Three species, the boreal owl (Aegolius funereus; at the trailing edge of its distribution), flammulated owl (Psiloscops flammeolus), and northern pygmy-owl (Glaucidium gnoma), were projected to experience the steepest habitat loss rates of 85%, 85%, and 76%, respectively. Projected vegetation shifts overlaid with well-documented flammulated owl breeding populations showed the complete or near complete loss of habitat by 2090 in areas of montane forest currently supporting dense aggregations of owl territories. Generalist or lower-elevation owl species were predicted to be less impacted, while, for the whiskered screech-owl (Megascops trichopsis), the contraction of the current habitat was nearly offset by a projected northward expansion. In general, the results of this study suggest high exposure to climate change impacts for the upper-elevation forest owls of semi-arid Southwestern North America. Long-distance migration and low natal philopatry may prove important to some montane owl populations in adapting to the regional loss of habitat.

Simulating dust emissions and secondary organic aerosol formation over northern Africa during the mid-Holocene Green Sahara period

Abstract. Paleo-proxy data indicate that a “Green Sahara” thrived in northern Africa during the early- to mid-Holocene (MH; 11 000 to 5000 years before present), characterized by more vegetation cover and reduced dust emissions. Utilizing a state-of-the-art atmospheric chemical transport model, TM5-MP, we assessed the changes in biogenic volatile organic compound (BVOC) emissions, dust emissions and secondary organic aerosol (SOA) concentrations in northern Africa during this period relative to the pre-industrial (PI) period. Our simulations show that dust emissions reduced from 280.6 Tg a−1 in the PI to 26.8 Tg a−1 in the MH, agreeing with indications from eight marine sediment records in the Atlantic Ocean. The northward expansion in northern Africa resulted in an increase in annual emissions of isoprene and monoterpenes during the MH, around 4.3 and 3.5 times higher than that in the PI period, respectively, causing a 1.9-times increase in the SOA surface concentration. Concurrently, enhanced BVOC emissions consumed more hydroxyl radical (OH), resulting in less sulfate formation. This effect counteracted the enhanced SOA surface concentration, altogether leading to a 17 % increase in the cloud condensation nuclei at 0.2 % super saturation over northern Africa. Our simulations provide consistent emission datasets of BVOCs, dust and the SOA formation aligned with the northward shift of vegetation during the “Green Sahara” period, which could serve as a benchmark for MH aerosol input in future Earth system model simulation experiments.

Decadal changes in vegetation cover within coastal dunes at the regional scale in Victoria, SE Australia

Vegetation is a critical boundary condition for the stability of coastal dunes. Globally, vegetation cover is increasing on the coast with many dunes being stabilised in the past decades. This pattern is driven by site-specific (e.g., coastal management) and global (e.g., climatic changes) factors. This study examines changes in dune vegetation during the past six decades at the regional scale along the southeast coast of Australia to understand the relative importance of the climate and human interventions in vegetation cover change. A total area of >31,000 ha, comprising 53% of the open coast of Victoria was studied. Since the 1960's, a general trend of dune stabilisation and coastal greening has occurred with total vegetation cover increasing from 61% to 84% coverage until 2020. At the regional scale, the increase in vegetation cover has been primarily driven by both climatic-related drivers, such as rising temperature, elevating CO2 concentrations and declining windiness, and state-wide coastal management interventions (e.g., marram grass planting, fencing, fire control, grazing removal). The only areas where there was a decline in total area of vegetation was where substantial coastal recession had occurred. The decrease in vegetation is a result of a loss of land area rather than a loss of plant biomass over the dunefields. Therefore, it is considered that the overall decadal changes in both climate and coastal management are forcing the dunes toward a more stabilised state at the regional scale. At the same time, compelling local drivers (e.g., storms and local sediment deficiency) can be the most crucial factor to regulate vegetation change and shift dune mobility at the site-specific scale.

Post-fire recovery of vegetation in the Chornobyl Radiation and Ecological Biosphere Reserve

ABSTRACT Fires significantly affect the structure and diversity of vegetation. Natural recovery of vegetation after fires in the Chornobyl Exclusion Zone is of special interest because of its status as a nuclear disaster area. This is the first assessment of the potential for natural regrowth of forest and post-fire succession after the catastrophic fires of 2020 that scorched 62 000 ha of forest across the territory. Most of these areas (>80%) have high potential for natural regeneration but, in the first instance, forest species are commonly replaced by wasteland weeds, some of them invasive; 10 alien plant species were identified in the studied plots. Megafires facilitate vegetation shifts and opportunities for invasive species, especially in the early stages of succession.

ENAMEL HYPOPLASIA AS A STRESS SIGNAL: UNVEILING PALEOENVIRONMENTAL STRESS EPISODES IN THE SIWALIK’S SUIDS OF PAKISTAN FROM THE MIDDLE MIOCENE TO EARLY PLEISTOCENE

Numerous paleontologists have used research on tooth enamel hypoplasia as a stress signal when assessing paleoenvironments. The goal of the current study was to identify and evaluate stress periods that occurred in the middle Miocene to early Pleistocene eras of the Siwaliks of Pakistan by analyzing enamel hypoplasia in eight extinct suids species: Listriodon pentapotamiae, Tetraconodon minor, Sivachoerus prior, Hippohyus lydekkeri, Hippohyus sivalensis, Hippopotamodon sivalense, Tetraconodon magnus, Propotamochoerus hysudricus. All suid species from all time intervals between 14.2 and 0.6 million years old (Myo) were analyzed, with the exception of those from the 11.2-9.0 Myo time frame (late Miocene), when no suids were found to show enamel hypoplasia. Enamel hypoplasia was the most common in suids from the middle Miocene Siwalik (63%), followed by those from the early Pliocene to the Pleistocene (43%), the late Miocene to the Pliocene (25%), and the late Miocene to the early Pleistocene (33%). The percentage of incidence of E.H with respect to each species was 62.50% in Listriodon pentapotamiae, 50% in Sivachoerus prior and Hippohyus sivalensis, 33.33% in Hippohyus lydekkeri and Propotamochoerus hysudricus and 0% in Tetraconodon minor and Tetraconodon magnus. The prevalence of enamel hypoplasia during the Neogene and Quaternary in the Siwalik region provides evidence for the occurrence of stress episodes, while the proportion of hypoplastic enamel illustrates the relative intensity of these stresses. These stressful events brought on by a lack of food or nutrition happened because of the historical periods' drastic shifts in weather, vegetation, ecology, and wildlife. These stress periods, which occurred from the early Miocene to the Pleistocene, may have spurred the evolution and speciation of the Siwalik fauna, notably the mammals. Key Words: Enamel hypoplasia, Stress signals, Paleoenvironment, Siwaliks, Suids

Assessing damage to agricultural fields from military actions in Ukraine: An integrated approach using statistical indicators and machine learning

The ongoing full-scale Russian invasion of Ukraine has led to widespread damage of agricultural lands, jeopardizing global food security. Timely detection of impacted fields enables quantification of production losses, guiding recovery policies and monitoring military actions. This study presents a robust methodology to automatically identify agricultural areas damaged by wartime ground activities using free Sentinel-2 satellite data. The 10 m resolution spectral bands and vegetation indices are leveraged, alongside their statistical metrics over time, as inputs to a Random Forest classifier. The algorithm efficiently pinpoints damaged fields, with accuracy metrics around 0.85. Subsequent anomaly detection delineates damages within the fields by combining spectral bands and indices. Applying the methodology over 22 biweekly periods in 2022, approximately 500 thousand ha of cropland across 10 regions of Ukraine were classified as damaged, with the most significant impacts occurring from March to September. The algorithm provides updated damage information despite cloud cover and vegetation shifts. The approach demonstrates the efficacy of automated satellite monitoring to assess agricultural impacts of military actions, supporting recovery analysis and documentation of war crimes.

Impacts of Climate Change on Vegetation in Kenya: Future Projections and Implications for Protected Areas

Climate change will cause substantial vegetation shifts across the world. Africa may face varying dynamics such as tree decline, savannization, and woody encroachment due to rising temperatures and rainfall changes. This study examines the potential effects of climate change on Kenyan vegetation and vegetation shifts for 2050 and 2100, employing a statistical model to predict vegetation state as driven by environmental variables, including temperature, soil moisture, livestock density, and topography. We evaluate the model by hindcasting it from 2020 to 2000 and then project future vegetation states for 2050 and 2100 under SSP 2–4.5 and SSP 5–8.5. In response to moderate emissions, a notable increase in arid-associated shrubland vegetation (53–58%) is forecasted, leading to the expansion of drylands at the expense of savannas, grasslands, and forests. Under high-emission scenarios, savannas are forecasted to expand (52–65%) at the expense of forested areas. Overall, dense forest cover declines across scenarios, affecting protected areas by promoting increased savanna cover and reducing forest area (40% to 50%). These projected shifts in major vegetation types would likely alter ecosystem functioning and associated services, impacting pastoralists and wildlife and raising biodiversity concerns. Protected areas in Kenya could lose 50% of their forests, highlighting the urgency of climate change mitigation. These findings offer a crucial foundation for future research and action on Kenya’s vegetation.

Macrofauna amplify plant litter decomposition and stabilization in arctic soils in a warming climate

The soil organic carbon (SOC) pool of the Arctic region is currently protected by low temperatures, but is likely to decrease due to greater organic matter (OM) decomposition under a warmer climate. Negative feedback for climate warming can, however, be reversed by SOC accrual as climate warming leads to shifts in arctic vegetation (from grass to shrub) and soil faunal (introduction of macrofauna) communities affecting plant-soil C allocation. To decipher these contrasting effects, we performed a laboratory experiment with soils from dry tundra to test the interacting effects of plant litter quality (high-quality grass litter vs. the intermediate- and low-quality litter of shrubs) and soil fauna functional grouping (micro-, meso- and macrofauna [millipede]) on the processes of litter decomposition and OM stabilization.Our findings showed that macrofauna largely promoted decomposition of shrub litter, while soil micro- and mesofauna were mainly responsible for the decomposition of grass litter. Our study thus confirmed that, when introduced and established in a warmer Arctic, macrofauna may become an important agent in shrub litter decomposition. Our data also showed that with shrub litter, higher C content was stabilized as particulate OM (POM) in aggregates, whereas in grass litter and low-quality shrub litter, higher C content was stabilized as mineral-associated OM (MAOM). Both these effects were larger in the presence of macrofauna and with a higher abundance of fungi. This suggests that consequent shrub OM stabilization in occluded POM and MAOM fractions will be carried out jointly by macrofauna and fungi, which will probably lead to more efficient OM stabilization in Arctic soils than in the case of grass litter OM stabilization by micro- and mesofauna and bacteria. In conclusion, our study suggests that vegetation changes and the introduction of macrofauna in a warming climate will most probably lead to higher OM stabilization in Arctic soils.

Climate change impacts: Vegetation shift of broad-leaved and coniferous forests

Climate change is a variation in temperature and precipitation for longer periods due to global warming. It has an impact on tree species distribution, composition and diversity of the forests. Our study aims to answer how future climate change is likely to have an impact on the vegetation shift of broad-leaved and coniferous forests. The study used forest resource assessment data (2010–2014) of Nepal to assess vegetation shift from the perspective of climate change scenario. We collected altogether 392 presence points (observations) for broad-leaved forests and 99 for coniferous forests. These occurrence points accompanied by bioclimatic variables and topographical variables (Elevation, Slope and Aspect) were used as input data in a MaxEnt model to predict the distribution of the coniferous and broad-leaved forests. We found a potential area of the near current (1970–2000) coniferous forest replaced by a broad-leaved forest under a climate change scenario (SSP2 4.5 for 2041–2060) and vice versa. The total projected vegetation shift area of Nepal was found to be approximately 1800 km2 (i.e. over 3 % of the total forest area). Out of the total vegetation shift area, almost 90 % percent of the area was found to be replaced by broad-leaved forest while the remaining 10 % area was found to be replaced by a coniferous forest. The climate change impact has been noticed in the vegetation shift, particularly the presence of broad-leaved forest is more dominant. The study provides better insights into the impact of climate change on the existing vegetation under the future climate change scenario.

The dynamics of vegetation diversity and biomass under traditional grazing in Ethiopia's Somali rangeland.

Traditional grazing management practices are central to rangeland productivity and biodiversity. However, the degradation of rangelands and loss of ecosystem services have raised concerns about the future of pastoralism as a form of land use. It is imperative to understand how these practices influence vegetation attributes, e.g., herbaceous species diversity and composition, growth forms (grass, forbs), life form (annuals, perennials), tree metrics (density, canopy cover, and biomass). This study evaluates vegetation shifts under three grazing management practices-enclosures, open grazing, and browsing lands-in the Somali pastoral ecosystem of Ethiopia. Enclosures exhibited the highest diversity in herbaceous species, with open grazing lands favoring forbs and annuals. Distinct compositional shifts in herbaceous species were observed across regimes, especially in grass and annuals. Enclosures had three times higher herbage biomass of open grazing and double that of browsing management practice. Conversely, browsing management practices presented optimal wood biomass, density, and canopy cover. The results highlight that a transition to combined enclosure and browsing practices can elevate plant production and diversity, benefiting the Somali rangeland economy. Consequently, dryland restoration should incorporate indigenous knowledge to ensure future rangeland sustainability and biodiversity preservation.

Forest reorganisation effects on fuel moisture content can exceed changes due to climate warming in wet temperate forests.

The distributions of vegetation and fire activity are changing rapidly in response to climate warming. In many regions, climate effects on dead fuel moisture content (FMC) are expected to increase future wildfire activity. However, forest FMC is largely driven by microclimate conditions, which are moderated from open weather by vegetation canopies. As shifts in vegetation increase under climate warming, the extent to which future fire activity will be driven by climate directly or associated vegetation shifts remains unresolved. Here, we present a study aimed at quantifying the relative magnitudes of (i) direct climate warming, and (ii) vegetation change, on FMC. Field sites to evaluate these effects were established in a natural laboratory of altered forest states to mature wet temperate forest in south-eastern Australia. FMC was estimated using a process-based model and 48 years of reconstructed climate data. Canopy effects on microclimate were captured by transferring inputs from climate to microclimate using models parameterised with field observations. To evaluate the relative magnitude of climate and vegetation effects, we calculated the maximum difference in mean annual FMC across annual climate replicates and compared this to FMC differences across reorganising forest sites. Our results show vegetation effects on FMC can exceed those related to expected climate change. Changes to forest structure and composition increased (+15.7%) and decreased (-12.3%) mean annual FMC, with a larger negative effect when forest cover was completely removed (-18.5%). In contrast, the largest climate effect on FMC was -6.6% across 48-years of data. Our study demonstrates that the magnitude of vegetation effects on FMC can exceed expected climate change effects. Models of future fire activity that do not account for changing vegetation effects on microclimate are omitting a key biophysical control on FMC and therefore may not be accurately predicting future fire activity.

Permafrost microbial communities follow shifts in vegetation, soils, and megafauna extinctions in Late Pleistocene NW North America

AbstractWe analyzed the microbial constituent of sedimentary ancient DNA sequence data recovered from subarctic loessal permafrost sediments dating between 30,000 and 4000 years ago. These data were originally studied for paleo‐ecological shifts in plants and animals associated with the Pleistocene–Holocene transition. Here, we explore whether there were changes in microbial communities paralleling the transition from distinctive cold‐adapted Ice Age megafauna and vegetation communities—the mammoth steppe ecosystem—toward the expansion of woody shrubs, extirpation of grazing megaherbivores, and development of the boreal forest. We observe a clear shift in the relative proportions of prokaryotic taxa after ca. 13,300 years ago associated with the collapse of the mammoth steppe. These data are consistent among study sites and between replicates processed with different methodologies (shotgun sequencing and targeted capture), which highlights that the “off‐target” fraction of metagenomic data used to study macro‐ecosystems can also be used to investigate synchronous changes in microbial communities. Functional analyses were performed with SEED and KEGG databases where we observed a shift in methane metabolism pathways after ~13,100 years ago, which suggests that there was a shift in methanogenesis away from animal gut microflora at the end of the Pleistocene. There does not appear to be a significant shift in the overall diversity of microbial communities despite the observed taxonomic and functional changes.

Changes in biogenic volatile organic compound emissions in response to the El Niño–Southern Oscillation

Abstract. Emissions of biogenic volatile organic compounds (BVOCs) from the terrestrial biosphere play a significant role in major atmospheric processes. BVOCs are highly reactive compounds that influence the atmosphere's oxidation capacity and also serve as precursors for the formation of aerosols that influence global radiation budgets. Emissions depend on the response of vegetation to atmospheric conditions (primarily temperature and light), as well as other stresses, e.g. from droughts and herbivory. The El Niño–Southern Oscillation (ENSO) is a naturally occurring cycle arising from anomalies in the sea surface temperature (SST) in the tropical Pacific. ENSO perturbs the natural seasonality of weather systems on both global and regional scales and is considered the most significant driver of climate variability. Several studies have evaluated the sensitivity of BVOC fluxes during ENSO events using historical transient simulations. While this approach employs realistic scenarios, it is difficult to assess the impact of ENSO alone given the multiple types of climate forcing, e.g. from anthropogenic emissions of CO2 and aerosol. In this study, a global atmospheric chemistry–climate model with enabled interactive vegetation was used to conduct two sets of simulations: (1) isolated ENSO event simulations, in which a single ENSO event is used to perturb otherwise baseline conditions, and (2) sustained ENSO simulations, in which the same ENSO conditions are reproduced for an extended period of time. From the isolated ENSO events, we present global and regional BVOC emission changes resulting from the immediate response of vegetation to atmospheric states. More focus is given to the sustained ENSO simulations, which have the benefit of reducing the internal variability for more robust statistics when linking atmospheric and vegetation variables with BVOC flux anomalies. Additionally, these simulations explore long-term changes in the biosphere with potential shifts in vegetation in this possible climate mode, accounting for the prospect of increased intensity and frequency of ENSO with climate change. Our results show that strong El Niño events increase global isoprene emission fluxes by 2.9 % and that one single ENSO event perturbs the Earth system so markedly that BVOC emission fluxes do not return to baseline emissions within several years after the event. We show that persistent ENSO conditions shift the vegetation to a new quasi-equilibrium state, leading to an amplification of BVOC emission changes with up to a 19 % increase in isoprene fluxes over the Amazon. We provide evidence that BVOC-induced changes in plant phenology, such as the leaf area index (LAI), have a significant influence on BVOC emissions in the sustained ENSO climate mode.

Palynological response deduced through spatially distinct surface samples to reconstruct palaeoecology and palaeoclimate of the Barak Valley, Assam (Indo-Burma region), northeast India

Establishing modern pollen analogues under various vegetation types in a location is necessary without which it is difficult to accurately interpret fossil pollen assemblages in any region in terms of the past environment and palaeoclimate. We have analysed the modern pollen dataset of 30 surface soil and sediment samples from the forested, cropland, wetland and river sites of the Karimganj District in south Assam, to comprehend the connection between the recent pollen assemblage and the vegetation patterns in the Barak Valley. The overall pollen data reflect the tropical moist deciduous and semi-evergreen forest comprising Syzygium, Schleichera, Terminalia, Lagerstroemia, Duabanga, Sapotaceae, Ilex, Mesua and Schima under a warm and humid climate in response to rainfall variations in the region. The presence of Euphorbiaceae and Convolvulaceae inferred high monsoonal activity in and around the region. A robust relationship between local herbaceous vegetation and pollen was observed. The steady occurrence of cereal pollen (average 18.67%) along with other cultural pollen taxa like Brassicaceae, Coriandrum and Solanaceae illustrate intense agricultural activity around the valley areas. Multivariate principal component analysis (PCA) and box plot were applied to the quantified data obtained from pollen frequency analyses of the surface samples which clearly revealed a significant variation and similarity in vegetation types. Thus, an attempt has been commenced to precisely observe the behavioural pattern of modern pollen deposition in a varied depositional setting, which could, in turn, help in assessing the expanse of agricultural practices and the depth of deterioration of pristine forests and surrounding areas. This modern training dataset could also help in the precise reconstruction of past climate and vegetation shifts in the Barak Valley region. A correlation of regional palynodata with other regions of the Indian subcontinent and Indo-Burma will also be assessed for better interpretation.