Regional Vegetation Research Articles

Late glacial through Early Holocene environments inferred using pollen from coprolites and sediments recovered from Paisley Caves, Oregon

AbstractThe Paisley Cave archeological site in the Northern Great Basin has provided a rich archaeological record from 13,000 to 6000 cal yr BP, including abundant mammalian coprolites preserved in a well-dated stratigraphy. Here we analyze and contrast pollen from within coprolites and pollen in associated sediments to examine vegetation history and assess whether coprolite pollen provides unique information with respect to the coprolite producer, such as the use of specific habitats, foods, or water sources. We found that the dissimilarity of pollen assemblages between coprolites and associated sediments was greater than the serial dissimilarity between stratigraphically adjacent samples within either group. Serial dissimilarity within types was not greater for coprolites than sediments, as would be expected if there were unique pollen signatures derived from the short period (1–2 days) represented by each coprolite. Compared with sediment pollen assemblages, the coprolites had higher abundances of lighter pollen types, and some individual samples were high in wetland taxa (especially Typha). Our results are consistent with coprolite pollen representing short time periods collected as a mammal moves on the landscape, whereas sediment pollen reflects longer time periods and more regional vegetation indicators.

Heterogeneity Analysis of Spatio-Temporal Distribution of Vegetation Cover in Two-Tider Administrative Regions of China

Vegetation cover is a crucial component of regional ecological environments that plays a vital role in maintaining ecosystem balance. This investigation utilized Google Earth Engine and MODIS NDVI products to examine the spatiotemporal heterogeneity of regional vegetation coverage based on the multi-year average NDVI in China. Using the multi-year average NDVI, multi-year change trend slope, coefficient of variation, and Hurst exponent, the spatial and temporal heterogeneity of provincial and prefectural administrative regions were quantified. The results indicated an upward trend in vegetation coverage from 2000 to 2021 at both provincial and prefectural levels, with growth rates of 0.032/10a and 0.03/10a, respectively. Moreover, the multi-year average NDVI significantly correlated with regional precipitation. Notably, vegetation growth was fastest in the Loess Plateau, while degradation was observed in southern Jiangsu and northern Zhejiang. Additionally, the degree of vegetation cover change in Ningxia and Macau was particularly prominent. These findings support the effectiveness of the Loess Plateau greening project and highlight the potential cost of economic and population growth on the ecosystem in eastern and southeastern coastal areas, where local vegetation degradation occurs. This study can serve as a valuable reference for ecosystem restoration and developmental planning at the administrative regional level, with the goal of enhancing vegetation management and conservation efforts in China.

Tracing Low‐CO2 Fluxes in Soil Incubation and 13C Labeling Experiments: A Simplified Gas Sampling System for Respiration and Photosynthesis Measurements

AbstractQuantifying carbon dioxide (CO2) fluxes between soil and atmosphere is key in understanding net ecosystem C exchange and biogeochemical C cycling in plant‐soil systems. In ecosystems with low primary production and sparse vegetation, for example, dry lands or subpolar regions where C fluxes are small, measurement sensitivity is key—even so when measurements are combined with isotopic labeling. Here, we present a simplified gas sampling system developed to facilitate sampling and measurement of low soil CO2 fluxes as well as in situ 13CO2 labeling in the same setup. The capacity of the system was tested in a set of feature tests along with gas measurements of dryland soil‐biocrust systems. The system's sensitivity to capture minor changes in CO2 concentration was confirmed in respiration and photosynthesis measurements of soil‐biocrust systems, where fluxes down to 0.1 μmol CO2 m−2 s−1 were quantified. A balloon, implemented to counterbalance underpressure build‐up during gas withdrawal, mitigated 72% of pressure differences at sampling. The overall system volume was reduced to a minimum to limit contamination caused by residual air, and the design enabled one‐step flushing and evacuation of system compartments and gas sample bags, successfully ruling out cross‐contamination between samples. Ultimately, this system offers a flexible and accessible solution for CO2 measurements that can be applied not only on arid soils with low biological activity and turnover rates, but also on plant‐soil systems. The modifications enabled larger, and thereby more representative, sample volumes to be collected while limiting incubation, contamination, and pressure effects on the intact soil system.

The Impact of Vegetation Canopy on the Outdoor Thermal Environment in Cold Winter and Spring

The current study investigated the impact of vegetation canopy on the outdoor thermal environment in cold winter and spring, a less-explored aspect of its climate effects. Firstly, we conducted on-site observations of meteorology parameters on a campus in a hot summer and cold winter region. Then the ENVI-met microclimate simulation model was utilized to simulate the air temperature, relative humidity, wind speed and direction, and solar radiation of typical winter and spring days. Furthermore, the PET index was calculated to evaluate the thermal conditions. Our findings revealed that during the daytime, the vegetation canopy raised air temperature and relative humidity, reduced wind speed, and mitigated solar radiation. Solar radiation emerged as the primary factor affecting thermal comfort in the cold winter and spring. The presence of deciduous broad-leaved vegetation notably reduced cold discomfort and improved thermal comfort in the cold winter and spring. Finally, we propose replacing evergreen broad-leaved vegetation with deciduous broad-leaved vegetation in hot summer and cold winter regions to ensure year-round thermal comfort, especially in the cold winter and spring.

Understanding carbon sequestration trends using model and satellite data under different ecosystems in India

This study discusses carbon sequestration variability in different ecosystems of India. Four different biosphere regions, each over 0.5° × 0.5° area, have been selected considering the geospatial and climatic variability of these regions expanding from Central India (CI), the Northeast region (NER), the Western Ghats (WG), and the Western Himalayan region (WHNI). The climatic conditions of these four regions are different so are the biosphere constituents of these regions. We expect the Gross Primary Productivity (GPP) to enhance during the all India summer monsoon rainfall season but in varied magnitudes suggesting a role of climatic parameters and flora in these regions. The GPP from FLUXCOM for the duration of 2001 to 2019 (19 years) and satellite-derived vegetation indices like the Normalized Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), and Leaf Area Index (LAI) are used in this study to understand the response of regional vegetation to this variability. EVI seems to be better related to GPP in comparison to NDVI in the preliminary analysis. Further analysis suggests LAI correlates better to GPP than EVI and NDVI in different seasons in these four regions. Also, meteorological parameters like surface temperature, rainfall, soil water, and other derived parameters like Vapor Pressure Deficit (VPD) are studied. It is also observed that the year-to-year variability in the climatic conditions could also have a role to play in the observed features. It is proven that the climate around the world is experiencing changes. Vegetation is one of the potent markers to monitor the impact of climate change. These long-term data and trends were studied to understand if there is any significant impact of the changing climatic conditions on the vegetation in these regions. Our study shows that there is an increasing (positive) trend in GPP at these locations though at different rates. WG and WHNI have shown a significant high rate of increase (6.44 and 5.36 gCm−2 y−1, respectively) in GPP over the last two decades.

Three-dimensional Budyko framework incorporating terrestrial water storage: Unraveling water-energy dynamics, vegetation, and ocean-atmosphere interactions

The two-dimensional steady-state Budyko framework, widely used to study water-energy dynamics in landscapes, primarily focused on the partitioning of precipitation into evapotranspiration (ET) and water yield. Though this framework has been extended by incorporating water storage changes into precipitation input for non-steady state conditions, the interactions among water-energy dynamics, vegetation covers, and ocean-atmosphere oscillations within the Budyko framework at finer spatial and temporal scales have been unexplored. This study aims to investigate the interactions of regional hydroclimatic conditions, vegetation, and climate teleconnections over the Indo-China Peninsula (ICP), a region highly vulnerable to climate change. To achieve the objective, we propose a three-dimensional Budyko framework that incorporates the ratio of Gravity Recovery and Climate Experiment (GRACE)-based terrestrial water storage (TWS) or its changes (TWSC) to precipitation (SI/SCI) as the third dimension alongside the traditional two-dimensional Budyko framework. Our findings reveal that TWS has a significant impact on the Budyko framework, particularly during the dry season. The dryness index (DI)/evaporative index (EI) and SI/SCI exhibit positive (strongly negative) linear relationships in the wet (dry) season, respectively. Vegetation covers strongly influence the three-dimensional Budyko framework, with poor performance observed in highly vegetated regions due to high ET demand. Through relative importance analysis, we identify the Silk Road Pattern (SRP) as the most influential climate teleconnection among nine different teleconnections, affecting hydroclimatic conditions over the ICP. Positive (negative) phases of SRP encourage water-limited (energy-limited) ET conditions. This demonstrates that the Budyko parameter is influenced not only by landscapes but also by climate teleconnections, offering potential benefits for Budyko parameter estimation. Furthermore, the linear relationships between DI/EI and SI/SCI in three-dimensional Budyko framework can provide a promising alternative method for evapotranspiration and groundwater estimation.

How greenhouse horticulture in arid regions can contribute to climate-resilient and sustainable food security

A potential change in climate and temperature could strongly affect weather-related crop losses. Using wastelands to grow crops in controlled greenhouse environments could improve global food security and preserve ecosystems. However, the impact of climate change on additional energy and water requirements of greenhouse-horticulture food production is still unknown. Using a greenhouse simulator for four locations (The Netherlands, Spain, Saudi Arabia and Namibia), we show that a rise in outdoor temperatures can be counterbalanced with a more intensive water-based cooling. Between 6.9% and 17.9%, more water is required in the worst-case scenario in the year 2100, while the yield quantity decreases by 3%–6% due to slightly deteriorating growth conditions within the greenhouse. Since cooling systems consume up to 90% of the total water use in desert greenhouses, saltwater cooling could play an essential role in increasing the efficiency and sustainability of greenhouse horticulture systems in arid regions. In this study, we investigate the economic and technical feasibility of such greenhouse systems on a larger scale and show the massive potential of these systems. The developed scenarios demonstrate considerable climate resilience, enabling the cultivation of fresh vegetables in arid and infertile regions both presently and in the future.

Automatically drawing vegetation classification maps using digital time‐lapse cameras in alpine ecosystems

AbstractAlpine ecosystems are particularly vulnerable to climate change. Monitoring the distribution of alpine vegetation is required to plan practical conservation activities. However, conventional field observations, airborne and satellite remote sensing are difficult in terms of coverage, cost and resolution in alpine areas. Ground‐based time‐lapse cameras have been used to observe the regions' snowmelt and vegetation phenology and offer significant advantages in terms of cost, resolution and frequency. However, they have not been used in research monitoring of vegetation distribution patterns. This study proposes a novel method for drawing georeferenced vegetation classification maps from ground‐based imagery of alpine regions. Our approach had two components: vegetation classification and georectification. The proposed vegetation classification method uses a pixel time series acquired from fall images, utilizing the fall leaf color patterns. We demonstrated that the performance of the vegetation classification could be improved using time‐lapse imagery and a Recurrent Neural Network. We also developed a novel method to accurately transform ground‐based images into georeferenced data. We propose the following approaches: (1) an automated procedure to acquire Ground Control Points and (2) a camera model that considers lens distortions for accurate georectification. We demonstrated that the proposed approach outperforms conventional methods, in addition to achieving sufficient accuracy to observe the vegetation distribution on a plant‐community scale. The evaluation revealed an F1 score and root‐mean‐square error of 0.937 and 3.4 m in the vegetation classification and georectification, respectively. Our results highlight the potential of inexpensive time‐lapse cameras to monitor the distribution of alpine vegetation. The proposed method can significantly contribute to the effective conservation planning of alpine ecosystems.

Greening rate in North Korea doubles South Korea

South and North Korea have experienced contrasting economic developments since the 1950s while sharing similar climates. Previous studies revealed an overall long-term greening trend across the Korean Peninsula based on greenness data from coarse-resolution satellite images. However, there has been no comprehensive comparison of the greenness patterns and the driving mechanisms between two countries due to the limitations of coarse-resolution satellite data. Here, we performed cross-calibration among Landsat sensors and adopted a phenology-based approach to generate Landsat annual maximum Normalized Difference Vegetation Index (NDVImax) time series for each pixel from 1986 to 2017. We found that over 1986–2017, the greening rate in North Korea was almost twice that of South Korea. Cropland in South Korea is the main source of the greening discrepancy. The expansion of agricultural facilities in the stable cropland area and urbanization in the cropland loss area of South Korea contributed 57% to the significant negative NDVImax trend, which was dominant over the forest NDVImax increase resulting from rising temperatures, CO2 fertilization effects and afforestation projects. However, in North Korea, CO2 fertilization effects in the stable cropland area and transition from grassland to cropland promoted an increase in NDVImax, despite decreasing NDVImax in forest areas due to deforestation. Our results highlight the need for delineating fine-scale land-use changes to advance our understanding of regional vegetation dynamics.

Hydrodynamics and Sediment Transport of Downslope Turbidity Current Through Rigid Vegetation

AbstractSystematical downslope‐turbidity‐current experiments were performed to clarify the relationship between sediment‐transport modes and current propagation patterns caused by rigid vegetation, as well as adjustments in turbulence characteristics of current. The equations for predicting the front velocities of downslope turbidity currents with emergent vegetation were proposed and validated via experimental data. Experimental results reveal that sediment deposition causes the lower turbulent kinetic energy (TKE) peaks of turbidity currents to decrease or even disappear without affecting their upper TKE peaks, while the rigid vegetation has the opposite effect. Vegetation stems destroy the longitudinal low‐high speed streaks associated with the quasi‐streamwise eddies in the near‐bed region and increase the proportions of the outward and inward interactions. In addition, sediment deposition severely suppresses the turbulent bursting events within turbidity currents but does not influence the relative proportions of the four bursting types. Rigid vegetation and sediment deposition both degrade the absolute values of the third‐order moments of velocity fluctuations without changing their signs to reduce the generation frequency of sweep events. Emergent rigid vegetation accelerates the formation of the reflected bore to provide energy for the deposited sediment to move downstream continuously. On the other hand, the dense submerged vegetation makes turbidity currents easily form the two‐head propagating mode, which allows part of the sediments carried by the upper current head to be transported downstream rather than deposited within or upstream of the vegetation region. Furthermore, the sloping boundary provides favorable conditions to initiate these specific modes for sediment transport adjusted by rigid vegetation.

The Application of OpenFOAM in Modelling Flow for Vegetated Channel

Vegetation plays an important role in the hydrodynamic behaviour of an open channel flow. This study attempted to investigate the flow characteristics of an emergent vegetated channel using Open-source Operations and Manipulation (OpenFOAM). InterFoam is an OpenFOAM solver used to model this simulation. It is one of the methods available to model free-flow surface flow. Results for flow velocity profile can be generated using ParaView software. This study used a constant inlet velocity of 0.0417 m/s. There are two sets of models including model L8 with a solid volume fraction (SVF) of 8% using 9 rigid dowels, and model 4S with SVF of 4% using 17 dowels within a 1.2 m2 study area. Dowels in L8 are arranged in linear formation compared to the 4S model in a staggered arrangement. The study found that in model 4S, the stem-scale vortices are developed individually after each dowel due to sparse staggered vegetation. Meanwhile, model 8L suggests oppositely the vortex is cramped from the closeness of the dowels. The shear layer is formed as the flow enters the vegetation patch at upstream and the instability causes the shear layer vortices between inside and outside the vegetation region. Both models agreed that as the flow moves downstream the vortices are greater and make the streamwise velocity region become slower. The vertical velocity profile acknowledges the shear layer patch-scale vortices have a greater influence on the flow of both models. The magnitude of turbulence intensity in lateral directions is bigger in model 4S than in model 8L. The influence of vortices shed by upstream cylinders has an increasing impact on the irregular shedding behaviour of downstream cylinders as plant density increases. In general, the TKE values of the Model 4S are higher than those of the Model 8L. Regardless of the solid volume percentage difference, the vegetation pattern between linear and staggered has an effect on the flow. Computational Fluid Dynamic (CFD) is indeed capable to solve complex hydrodynamic characteristics.

Divergent trends in grassland degradation and desertification under land use and climate change in Central Asia from 2000 to 2020

Grassland degradation (within-state change) and desertification (state conversion from grasslands to deserts) are different states in the complex dynamic process of grassland deterioration. However, the dynamics and associated drivers of the two states have been rarely examined separately, which is critical for early warning and conservation policy making. Here, the grassland degradation and desertification in Central Asia (CA) were studied due to their evident vulnerability to climate extremes and human activities. We performed a two-step approach to identify the critical state zones first (i.e., grasslands, deserts, and the desertification zones) and then assess the vegetation dynamics within each zone. Finally, we quantified the roles of CO2 fertilization effect, climate change, climate variability, land use (LU), and anthropogenic climate change (ACC) on the vegetation dynamics in different state zones. The results showed that the areas of grasslands and sparse vegetation regions (including deserts and desertification zones) were stable from 2000 to 2020, but the trends of vegetation greenness were divergent with a reduction in grasslands and an increase in sparse vegetation regions. Furthermore, climate change and climate variability were the main driving force affecting grassland degradation in CA. Yet the vegetation greening in the desertification and desert zones was mainly driven by the rising CO2 and LU. Moreover, ACC degraded 20.63% of grasslands and sparsely vegetated lands in CA on the baseline of 2000. The results highlighted the risks of grassland degradation in CA. This study proposed a methodology to examine grassland degradation and desertification in detail and quantify the associated driving factors (especially ACC) at the pixel scale, which provided some insights on developing region-precise strategies for grassland conservation in CA and other drylands.

Changes in How Climate Forces the Vegetation of Southern Africa

Global climatic changes are altering ecosystem structure and functioning, yet detecting and forecasting such change is difficult. In this study, we use the concept of a phytoclime—a region where climate favours the growth of similar combinations of plant types—to examine how changes in climate forcing may impact on regional vegetation. We use species distribution data to estimate the parameters of a physiological plant growth model for 5006 vascular plant species common to southern Africa. Plant type suitability surfaces are calculated as the average climatic suitability of locations for all species belonging to a plant type. We calculated plant type suitability surfaces for ten different plant types. The resulting surfaces were used to produce a spatial classification of phytoclimes, which we interpret as regions that can climatically support particular plant type combinations. We use the phytoclime definitions and climatologies from five global circulation models (GCMs) simulating three shared economic pathways (SSPs) to forecast how the climatic forcing underlying the phytoclimes will change. Our analyses forecast that change in phytoclime state will be widespread throughout the region. There were, however, substantial differences in the timing of when changes would occur. The central interior of the region was forecast to change earlier than the arid west and southern coast. These differences in timing were driven by differences in the responses of trees, succulents, C3 and C4 grasses to the GCMs forecast aridification of the region’s central interior. Phytoclime modelling provides an indication of the potential of a region’s climate to support different plant types; it thereby provides forecasts of the potential impacts of climate change on regional vegetation structure and functioning.

Unravelling geospatial distribution and genetic diversity of greenhouse whitefly, Trialeurodes vaporariorum (Westwood) from Himalayan Region

The Greenhouse whitefly (GWF), Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae), is a destructive pest that affects protected cultivation worldwide. The Indian Himalayan region is particularly vulnerable to GWF introduction, invasion, and spread due to the expansion of protected cultivation and climate change. In this study, we collected 32 naturally occurring GWF populations, mainly from the Uttarakhand state in the Indian Himalayan region, to investigate the distribution pattern and genetic diversity of T. vaporariorum. Our sampling was representative of the region's vegetation diversity and geographical location, and we collected samples from multiple sites within each locality to account for local variations. The mtCOI gene was used to accurately detect and identify GWF and to sequence haplotypes prevalent in the Uttarakhand state. The maximum likelihood method used for phylogenetic studies revealed that all 32 whitefly samples in this study belonged to T. vaporariorum and were prevalent in all the collected localities. Our population genetic study using mtCOI showed variation within T. vaporariorum populations, with 20 distinct haplotypes present. Notably, haplotype 2 (H2) was the most dominant haplotype among the sampled populations. These results provide fundamental knowledge for understanding the geographical distribution and ecology of T. vaporariorum in the Uttarakhand state of the Indian Himalayan region. The discovery of geospatial and genetic diversity of GWF in the Himalayan region underscores the importance of pest alertness, research prioritization, and the development of sustainable management strategies to protect crops.

Greening and Browning Trends on the Pacific Slope of Peru and Northern Chile

Accurate detection and quantification of regional vegetation trends are essential for understanding the dynamics of landscape ecology and vegetation distribution. We applied a comprehensive trend analysis to satellite data to describe geospatial changes in vegetation along the Pacific slope of Peru and northern Chile, from sea level to the continental divide, a region characterised by biologically unique and highly sensitive arid and semi-arid environments. Our statistical analyses show broad regional patterns of positive trends in EVI, called “greening”, alongside patterns of “browning”, where trends are negative between 2000 and 2020. The coastal plain and foothills, up 1000 m, contain notable greening of the coastal Lomas and newly irrigated agricultural lands occurring alongside browning trends related to changes in land use practices and urban development. Strikingly, the precordilleras show a distinct ‘greening strip’, which extends from approximately 6°S to 22°S, with an altitudinal trend, ascending from the tropical lowlands (170–780 m) in northern Peru to the subtropics (1000–2800 m) in central Peru and temperate zone (2600–4300 m) in southern Peru and northern Chile. We find that the geographical characteristics of the greening strip do not match climate zones previously established by Köppen and Geiger. Greening and browning trends in the coastal deserts and the high Andes lie within well defined climatic and life zones, producing variable but identifiable trends. However, the distinct Pacific slope greening presents an unexpected distribution with respect to the regional Köppen–Geiger climate and life zones. This work provides insights on understanding the effects of climate change on Peru’s diverse ecosystems in highly sensitive, biologically unique arid and semi-arid environments on the Pacific slope.

Differentiation characteristics of karst vegetation resilience and its response to climate and ecological restoration projects

AbstractIn light of the recent pressure from global warming, extreme drought events, and deleterious human activity, the strength and long‐term change trends of vegetation in karst regions—in terms of their resistance to external disturbances—have not been studied systematically. Therefore, herein, we quantified the vegetation resilience and its nonlinear change trends in south China karst under different environmental gradients by measuring the lag‐1 autocorrelation to time‐series Normalized Difference Vegetation Index (1990–2018), clarifying the driving forces of vegetation resilience changes. It was shown that the vegetation resilience change in south China karst was not monotonous. In the first stage (pre‐2002), precipitation and warming promoted the increase of regional vegetation resilience (slope = −0.045, p < 0.0001). In the second stage (during 2002–2010), the increasing trend of vegetation resilience was not obvious and vegetation resilience was difficult to keep up with vegetation productivity, indicating the time‐lagged effect of ecological restoration projects to vegetation resilience. In the third stage (post‐2010), due to the continuous advancement of ecological restoration projects, vegetation resilience increased significantly and had the largest amplitude (slope = −0.128, p < 0.0001). Simultaneously, under different environmental gradients, vegetation resilience showed significant differentiation characteristics. In comparison to non‐karst regions, increases in the vegetation resilience were more obvious in karst regions especially in the post‐2010. With increases in the soil depth, the vegetation resilience exhibited an increasing trend, indicating its dependence on soil. At slopes >25°, the vegetation resilience increased most obviously and the resilience of meadows was the largest, which can be the preferred vegetation type for ecological restoration projects. This research provides another perspective to understand karst vegetation ecosystem and the results will facilitate the protection of karst ecosystems.

Vertical Farming: An Option in Modern Food Production: A Review

Meeting the food needs will be one of the major problems, as farmland is being lost due to causes including soil contamination, water scarcity, and climate change, among others. In this situation, a workable alternative to manage this perennial problem is provided by vertical farming, an energy-efficient, environmentally friendly agricultural technology that does not use soil. Vertical farming could indeed be an important factor in the production of crops and vegetables in regions with scarce soil and water resources. With modern technology such as hydroponics, aeroponics, and aquaponics, the idea of a vertical farm appears to have a promising future. In times of pandemics like COVID-19, it has emerged as a viable option for growing a wide range of food crops to suit the dietary needs of the growing world population.

Numerical Modelling of Turbulence Kinetic Energy in Open Channel Flows with Mixed-Layer Vegetation

Vegetation plays a vital role in the flow characteristics of natural open channels, such as rivers. Typically, vegetation density is higher in the lower layer and sparser in the upper layer of these channels. In this research, Ansys Fluent and the k–ϵ model have been employed to simulate various vegetation configurations to capture intricate flow complexities within vegetation regions. Numerical analysis demonstrated that the numerical results align with anticipated Turbulence Kinetic Energy data obtained from analytical and experimental studies. Our findings revealed that double-layer vegetation induces a more intricate flow distribution. In the spaces between vegetation zones, Turbulence Kinetic Energy decreases due to the resistance imposed by the vegetation patches. This resistance has positive implications for sustaining aquatic life and facilitating sediment deposition, promoting a more environmentally sustainable outcome.

Dominance of Topography on Vegetation Dynamics in the Mt. Qomolangma National Nature Reserve: A UMAP and PLS-SEM Analysis

The southern portion of the Qinghai–Tibet Plateau (QTP) and the central Himalayan region are home to the Mt. Qomolangma (Everest) National Nature Reserve (QNNR), which is the world’s highest nature reserve and is distinguished by delicate natural ecosystems and unique geographic features. Analyzing regional vegetation trends, as well as the impacts of natural and anthropogenic variables on vegetation coverage, is crucial for local environmental protection and sustainable development. In this study, the variation patterns of the MOD13Q1 Normalized Difference Vegetation Index (NDVI) data were explored, and the responses of vegetation development to both natural and anthropogenic parameters were investigated by applying trend analysis and partial correlation analysis, as well as the partial least squares-structural equation model (PLS-SEM). To better comprehend the spatial characteristics and interrelationships between NDVI and various parameters under different vegetation types, the Uniform Manifold Approximation and Projection (UMAP) was employed for dimensionality reduction and visualization. The results illustrated that between 2000 and 2018, the reserve greened up at a rate of 0.00073/a (p < 0.05), with vegetation improvement areas accounting for 49.46%. The major climatic driver for the greening trend of vegetation was temperature. Topography (especially elevation) remains dominant in regulating vegetation development in the QNNR, despite a progressively growing impact of hydrothermal conditions on vegetation development. Additionally, the implementation of environmental initiatives has stifled the adverse impacts of human activity.

Holocene forest and land-use history of the Erzgebirge, central Europe: a review of palynological data

Abstract. The ongoing ecological conversion of mountain forests in central Europe from widespread Picea monocultures to mixed stands conceptually also requires a historical perspective on the very long-term, i.e. Holocene, vegetation and land-use dynamics. Detailed sources of information for this are palynological data. The Erzgebirge in focus here, with a maximum height of 1244 m a.s.l., represents an extreme case of extensive historical deforestation since the Middle Ages due to mining, metallurgy, and other industrial activities, as well as rural and urban colonisation. For this regional review we collected and evaluated 121 pollen diagrams of different stratigraphic, taxonomic, and chronological resolution. This number makes this region an upland area in central Europe with an exceptionally high density of palynological data. Using well-dated diagrams going back to the early Holocene, main regional vegetation phases were derived: the Betula–Pinus phase (ca. 11 600–10 200 cal yr BP), the Corylus phase (ca. 10 200–9000 cal yr BP), the Picea phase (ca. 9000–6000 cal yr BP), the Fagus–Picea phase (ca. 6000–4500 cal yr BP), the Abies–Fagus–Picea phase (ca. 4000–1000 cal yr BP), and the anthropogenic vegetation phase (ca. 1000–0 cal yr BP). Some diagrams show the presence or even continuous curves of potential pasture and meadow indicators from around 2000 cal BCE at the earliest. Even cereal pollen grains occur sporadically already before the High Medieval. These palynological indications of a local prehistoric human impact also in the higher altitudes find parallels in the (geo-)archaeologically proven Bronze Age tin placer mining and in the geochemically proven Iron Age metallurgy in the Erzgebirge. The pollen data show that immediately before the medieval clearing, i.e. beginning at the end of the 12th century CE, forests were mainly dominated by Fagus and Abies and complemented by Picea with increasing share towards the highest altitudes. According to historical data, the minimum of the regional forest cover was reached during the 17th–18th centuries CE. The dominance of Picea in modern pollen spectra is caused by anthropogenic afforestation in the form of monocultures since that time. Future palynological investigations, preferably within the framework of altitudinal transect studies, should aim for chronologically and taxonomically high-resolution and radiometrically well-dated pollen diagrams from the larger peatlands.