Montane Regions Research Articles

How Veeries vary: Whole genome sequencing resolves genetic structure in a long-distance migratory bird

Abstract In high-latitude species with high dispersal ability, such as long-distance migratory birds, populations are often assumed to exhibit little genetic structure due to high gene flow or recent postglacial expansion. We sequenced over 120 low-coverage whole genomes from across the breeding range of a long-distance migratory bird, the Veery (Catharus fuscescens), revealing strong evidence for isolation by distance. Additionally, we found distinct genetic structure between boreal, western montane U.S., and southern Appalachian sampling regions. We suggest that population genetic structure in this highly migratory species is detectable with the high resolution afforded by whole-genomic data because, similar to many migratory birds, the Veery exhibits high breeding-site fidelity, which likely limits gene flow. Resolution of isolation by distance across the breeding range was sufficient to assign likely breeding origins of individuals sampled in this species’ poorly understood South American nonbreeding range, demonstrating the potential to assess migratory connectivity in this species using genomic data. As the Veery’s breeding range extends across both historically glaciated and unglaciated regions in North America, we also evaluated whether contemporary patterns of structure and genetic diversity are consistent with historical population isolation in glacial refugia. We found that patterns of genetic diversity did not support southern montane regions (southern Appalachians or western U.S. mountains) as glacial refugia. Overall, our findings suggest that isolation by distance yields subtle associations between genetic structure and geography across the breeding range of this highly vagile species even in the absence of obvious historical vicariance or contemporary barriers to dispersal.

Agroforestry enhances biological activity, diversity and soil-based ecosystem functions in mountain agroecosystems of Latin America: A meta-analysis.

Mountain agroecosystems in Latin America provide multiple ecosystem functions (EFs) and products from global to local scales, particularly for the rural communities who depend on them. Agroforestry has been proposed as a climate-smart farming strategy throughout much of the region to help conserve biodiversity and enhance multiple EFs, especially in mountainous regions. However, large-scale synthesis on the potential of agroforestry across Latin America is lacking. To understand the potential impacts of agroforestry at the continental level, we conducted a meta-analysis examining the effects of agroforestry on biological activity and diversity (BIAD) and multiple EFs across mountain agroecosystems of Latin America. A total of 78 studies were selected based on a formalized literature search in the Web of Science. We analysed differences between (i) silvoarable systems versus cropland, (ii) silvopastoral systems versus pastureland, and (iii) agroforestry versus forest systems, based on response ratios. Response ratios were further used to understand how climate type, precipitation and soil properties (texture) influence key EFs (carbon sequestration, nutrient provision, erosion control, yield production) and BIAD in agroforestry systems. Results revealed that BIAD and EFs related to carbon sequestration and nutrient provisioning were generally higher in agroforestry systems (silvopastoral and silvoarable) compared to croplands and pasturelands without trees. However, the impacts of agroforestry systems on crop yields varied depending on the system considered (i.e., coffee vs. cereals), while forest systems generally provided greater levels of BIAD and EFs than agroforestry systems. Further analysis demonstrated that the impacts of agroforestry systems on BIAD and EFs depend greatly on climate type, soil, and precipitation. For example, silvoarable systems appear to generate the greatest benefits in arid or tropical climates, on sandier soils, and under lower precipitation regimes. Overall, our findings highlight the widespread potential of agroforestry systems to BIAD and multiple EFs across montane regions of Latin America.

The absence of disturbances promoted Late Holocene expansion of silver fir (Abies alba) in the Bohemian Forest

Temperate forests in the Northern Hemisphere are strongly affected by increasing annual temperatures and natural disturbances such as droughts, fires, and pest outbreaks. In many regions, alternatives are explored by the forestry industry for previously commercialized tree species which are rapidly declining in areas outside their optimal climatic niches. However, as the current ranges of tree species have been mainly constrained by human activity, their true climatic and ecological niches are likely different from our observations. For example, little is known about environmental niches and population dynamics of tree species with limited dispersal ability, such as silver fir (Abies alba). Long-term (paleo) records of past landscape composition, past climate, and past disturbances can help to reveal the natural environmental niches of tree species. This study focuses on the Bohemian Forest (Šumava) in Czechia, where the human alteration of forests in higher elevations (>1000 m asl) has only been demonstrated from Medieval times onward. We present an interdisciplinary approach of geochemistry, pollen, charcoal, botanical and insect macro remains from a high-elevation peat record for the last seven millennia. Our multi-proxy study aimed to identify episodes of increased fire and other disturbances such as insect outbreaks, which could have influenced forest dynamics and vegetation succession in this montane region. However, the charcoal and macro-fossil records do not indicate any large local fires, insect outbreaks, browsing, or other disturbances (e.g., anthropogenic) for a major part of the record, suggesting that changes in the vegetation after 6500 cal yr BP were mainly caused by climatic fluctuations. Silver fir (Abies alba) expanded from 4300 cal yr BP, and likely became the dominant tree species at this locality for the next 2000 years, with extremely high pollen values up to 60%. During the establishment of silver fir around the peat bog around 5600 cal yr BP and its expansion around 4300 cal yr BP, the geochemical record and low counts of the testate amoeba Archerella flavum indicate drier conditions on the peat bog. Comparison with climatic simulations on a 1 × 1-km scale from the CHELSA database suggests that the local expansion of silver fir possibly coincided with a decrease in precipitation during both the wettest and warmest quarter of the year, related to a decreasing trend in seasonality of annual precipitation; this might confirm the species' higher tolerance to drought. Although silver fir is currently extremely rare in the Bohemian Forest, it has the potential for local expansion if logging, fire, and game browsing are kept to a minimum.

Soil sampling methods for microbial study in montane regions

Soil microorganism studies are crucial in ecological and biological research. However, the lack of standardized analytical methods for sampling makes it challenging to compare studies and obtain consistent results. Therefore, it is essential to establish standardized sampling methods in the field. Our study used a stratification method to collect 120 soil samples from various altitudinal ranges on Cangshan Mountain in China, with an altitude of 4122 m, and incredible microorganism biodiversity. This site provides an ideal landscape for studying elevation patterns in microorganisms. We conducted analyses on the variations of depth and stratification used in the sampling process, as these factors have been found to impact microbial diversity, elevation patterns, and community assembly mechanisms. We found that increasing the sampling depth provided more valuable research results by revealing elevation patterns of soil microorganisms. We therefore recommend sampling to a depth of 35 cm with stratification to determine the overall soil microbial diversity. A depth of 25 cm is suitable for studying elevation patterns with stratification. For investigating community assembly mechanisms without stratification, a depth of 15 cm is recommended. When exploring a specific taxon, the sampling depth can be adjusted accordingly. For studying the elevation pattern of archaea, a depth of 20 cm is appropriate. In the case of fungi, a depth of 40 cm is recommended, while a depth of 20 cm is suitable for studying elevation patterns. This study emphasizes the importance of standardization in sampling methods, particularly along the soil profiles, when studying soil microbiomes in montane areas. These recommendations should be adopted in future research to achieve more consistent and reliable results in the field.

Evaluating the addition of radar with optical data for vegetation mapping in a montane region in Sri Lanka

Evaluating the addition of radar with optical data for vegetation mapping in a montane region in Sri Lanka

A dataset of horizontal and slope-parallel installation of radiometer to measure solar radiation components and turbulent energy flux at Maoershan station in 2016

Solar radiation is one of the key parameters driving carbon and water fluxes, as well as other types of terrestrial processes. Radiometers, the most commonly used instruments for measuring local-scale radiation and albedo, are typically installed horizontally according to meteorological observation standards. However, under sloping terrain conditions, their hemispherical view and the surface receiving or reflecting radiation are not vertical. This discrepancy often results in a daily phase shift between net radiation and turbulent energy fluxes. Montane region accounts for one-quarter of the total global land surface area, yet few studies have quantified and corrected the errors resulting from horizontal installation of net radiometers in these areas. The dataset compiled in this paper were solar radiation and turbulent energy flux data measured by horizontal and slope-parallel radiometers in the secondary forest of the Maoershan Forest Ecosystem Research Station in Heilongjiang from March 17, 2016, to April 3, 2017. The data included incident and reflected shortwave radiation, longwave radiation, photosynthetically active radiation, as well as albedo, solar elevation angle, clear sky index, sensible heat flux, latent heat flux, and soil surface heat flux data. These data were stored in half-hour intervals, with radiation and turbulent energy flux data coverage rates during the growing season (May 3, 2016 to October 10, 2016) of 100% and 81.3% respectively. This dataset can provide original data for evaluating the impact of radiometers installation methods on the measurement of radiation components and albedo in montane regions, which not only help to correct historical data or construct more accurate models, but can also provide methodological references for studies related to carbon, water, and energy fluxes.

Climate conditions are primary predictors of the regional‐scale spatial diversity patterns of ectomycorrhizal fungi

AbstractAimSpatial models are valuable for revealing biodiversity patterns but are less commonly applied to soil microbes than to aboveground macroorganisms. Ectomycorrhizal (EM) fungi are symbiotic microbes with high taxonomic and functional diversity that are associated with forest trees. We aimed to predict regional‐scale spatial patterns of EM fungal richness and community composition.LocationForests and subalpine ecosystems in Japan, from Hokkaido to Okinawa.TaxonEM fungi (Asco‐ and Basidiomycetes).MethodsWe used EM fungal DNA sequence data from 1507 soil cores at 39 sites covering a wide range of environmental conditions. The random forest machine learning approach was applied to determine the relative importance of environmental variables (i.e. climate, soil and ecosystem productivity) and to make spatial predictions. The spatial patterns of EM fungal richness and community composition were mapped at 1‐km2 grid resolution.ResultsTemperature generally had a strong influence on EM fungal richness and community composition dissimilarity. Our regional spatial analysis revealed that (1) EM fungal richness was higher in northeastern and montane regions than in southwestern regions and low‐elevation plains, (2) different EM fungal lineages exhibited contrasting spatial diversity patterns and (3) community composition dissimilarity shifted sharply from high to low elevations, and gradually from northeastern to southwestern regions, mainly in relation to climate gradients. Areas with low applicability for spatial modelling were identified based on multidimensional environmental spaces, which will help to prioritize data collection for future research.Main ConclusionsOur study provides a baseline of the potential spatial patterns of EM fungal communities, which were explained primarily by climate variables and secondarily by soil factors and ecosystem productivity. The predicted spatial patterns may be valuable for identifying diversity hotspots and advancing the assessment of climate change impacts on ecologically important root‐associated fungi.

Comparable ectomycorrhizal fungal species richness but low species similarity among native Abies alba and alien Abies grandis from provenance trials in Poland

Our study contributes to the understanding of the diversity of ectomycorrhizal fungal (ECMF) communities of native A. alba and alien A. grandis in provenance trials situated in lowland and montane regions in Poland (Central Europe). Ectomycorrhizal fungi were identified directly from field-collected root tips using PCR- and Sanger-sequencing-based methods. We found that the studied fir species had relatively high and comparable ECMF species richness (66 and 69 fungal taxa on A. grandis and A. alba, respectively). Twenty-six taxa were associated with both hosts and 83 taxa were found uniquely on one or the other fir species. The ECMF community composition and structure of A. alba and A. grandis differed substantially both at the species and the phylogenetic lineage levels. Soil parameters such as total nitrogen, magnesium and potassium content and C/N ratio appeared moderately but significantly correlated with the ECMF community assembly of both firs. The provenance of the host tree species did not appear to be a strong factor in structuring the ECMF communities. This was found despite the low number of common ECMF species and relatively high number of unique species among the individual provenances of both fir species. The results of the study suggest that locally based specificity in host–fungal communities is likely a contributing factor in the outcome of provenance trials. We posit that much insight into the role of tree provenances in shaping ECMF communities will be gained by further exploring this area of research. On the surveyed experimental forest sites of A. alba and A. grandis, fungal species of conservation concern – particularly those that were endangered and rare – have been reported. Our findings imply that tree species planted outside their natural range serve as ecologically important species because they may act as an excellent reservoir of ECMF diversity, a factor of importance in functioning forest ecosystems.

Multi-locus genomic signatures of local adaptation to snow across the landscape in California populations of a willow leaf beetle.

Organisms living in mountains contend with extreme climatic conditions, including short growing seasons and long winters with extensive snow cover. Anthropogenic climate change is driving unprecedented, rapid warming of montane regions across the globe, resulting in reduced winter snowpack. Loss of snow as a thermal buffer may have serious consequences for animals overwintering in soil, yet little is known about how variability in snowpack acts as a selective agent in montane ecosystems. Here, we examine genomic variation in California populations of the leaf beetle Chrysomela aeneicollis, an emerging natural model system for understanding how organisms respond to climate change. We used a genotype-environment association approach to identify genomic signatures of local adaptation to microclimate in populations from three montane regions with variable snowpack and a coastal region with no snow. We found that both winter-associated environmental variation and geographical distance contribute to overall genomic variation across the landscape. We identified non-synonymous variation in novel candidate loci associated with cytoskeletal function, ion transport and membrane stability, cellular processes associated with cold tolerance in other insects. These findings provide intriguing evidence that variation in snowpack imposes selective gradients in montane ecosystems.

New Finds and Ecology of the Rare Liverworts Scapania apiculata, Scapania carinthiaca, and Scapania scapanioides in Austria.

Scapania apiculata, Scapania carinthiaca, and Scapania scapanioides are rare deadwood-dwelling liverworts threatened across Europe. Scapania carinthiaca is thus listed in the Habitats Directive. However, their distribution data are scattered, and their ecologic demands are insufficiently studied. Here, we present new locations and data on the ecology of the species, which resulted from a targeted search in selected regions of Austria. We found ten new sites each for Scapania apiculata and Scapania scapanioides and twenty for Scapania carinthiaca. Reproduction was exclusively asexual. The macroclimates of all known locations in Austria did not differ significantly between the three species. It was consistently wet, with a mean annual precipitation of 1615.3 mm, a high evenness of rainfall, and a low desiccation risk. The mean temperature averaged 7.4 °C. The habitat was shaded dead wood of Picea abies, Abies alba, and Fagus sylvatica of all decay stages at a median distance of 2.5 m from streams or springy areas in semi-natural forests of montane and submontane regions. Thus, high deadwood volumes under a suitable climate are a prerequisite for the occurrences of the species. The number of locations of new finds has more than doubled in Austria and thus in Europe.

Evolution of the Xerocarpa clade (Opuntia; Opuntieae): Evidence for the Role of the Grand Canyon in the Biogeographic History of the Iconic Beavertail Cactus and Relatives.

The formation of the western North American drylands has led to the evolution of an astounding diversity of species well adapted for such communities. Complex historical patterns often underlie the modern distribution of the flora and fauna of these areas. We investigated the biogeography of a group of desert-adapted prickly pears, known as the Xerocarpa clade, from western North America. The Xerocarpa clade originated in the mid-late Pliocene, likely on the Colorado Plateau, and then moved south into the Mojave, Sonoran, and Chihuahuan deserts, and California montane regions, further diversifying, mostly into the Quaternary. The southward trajectory of the clade was likely greatly influenced by the formation of the Grand Canyon. The synapomorphy of dry fruit presumably impeded the long-distance dispersibility of the beavertail cactus, Opuntia basilaris, while dry, spiny fruit may have enabled O. polyacantha to substantially increase its distribution. Opuntia basilaris evolved a pubescent epidermis, allowing it to invade hotter, drier conditions, while the spine-clothed stems of O. polyacantha may have given it an advantage for increasing its northern range into colder environments. The Xerocarpa clade shows a cold desert origin, and changes in morphological characters have made these sister taxa well adapted for invading broadscale, but oftentimes contrasting habitats.

A novel alpine land cover classification strategy based on a deep convolutional neural network and multi-source remote sensing data in Google Earth Engine

ABSTRACT Alpine land cover (ALC) is facing many challenges with climatic change, biodiversity reduction and other cascading ecosystem damage triggered by natural and anthropogenic interference. Although several global land cover products and thematic maps are already available, their mapping accuracy of alpine and montane regions remains unsatisfactory due to the data acquisition, methodology, and workflow design constraints. Therefore, in this paper, a deep convolutional neural network (DCNN) in Google Earth Engine (GEE) was developed to map the ALC types of the Yarlung Zangbo river basin (YZRB) in the Tibetan plateau using multi-source remote sensing data. The DCNN algorithm was offline trained using automatically generating samples and online deployed in the GEE for a large-scale ALC mapping. Moreover, a set of fine land cover classification system (containing 14 ALC types) was also established in accordance with the natural situation of the YZRB. The overall accuracy and kappa were 86.24% and 0.8156, which were higher than traditional classification algorithms. The spatial distribution of ALC types was analyzed in different gradient zones, and a clear altitudinal characteristic was noticed. The terrain of the YZRB from upper-stream to down-stream with an elevation dramatically decreases, and corresponding to vertical zonal changes from glacier and permanent snow/ice, barren gravel land, alpine desert steppe, alpine steppe, alpine meadow, shrubs, to tree cover. The product can provide valuable land cover information to support alpine ecosystem conservation.

Secretive marsh bird occupancy across a spectrum of hydroelectric reservoir management in western montane Canada

AbstractDam construction projects have created opportunities for water security, targeted flood protection, and energy production but at the cost of increasing anthropogenic pressure on affected aquatic ecosystems. Wetland ecosystems are often among the most vulnerable, as underlying hydrological regimes influence overall wetland structure and function. Marsh bird species are wetland and riparian habitat specialists, many of which are experiencing population declines across North America. We examined how the alteration of hydrological regimes for generating hydroelectric power affected the occurrence of secretive marsh bird species in the western montane region of British Columbia, Canada. We established survey stations in wetlands across 2 regions, the West Kootenay and the Columbia Wetlands, sampling across a spectrum of hydrological regimes and other potentially relevant factors. At each station, we assessed wetland occupancy during the breeding season using broadcast‐callback surveys focused on 5 secretive marsh bird species: American bittern (Botaurus lentiginosus), American coot (Fulica americana), pied‐billed grebe (Podilymbus podiceps), sora (Porzana carolina), and Virginia rail (Rallus limicola). Additionally, we measured vegetation structure and the proximity and size of nearby water bodies for each survey station. We then used occupancy models to assess important correlates behind wetland occupancy for these marsh bird species, considering water management operations, regional differences, and local‐ and landscape‐level wetland characteristics. Secretive marsh bird species were more likely to occupy wetlands in areas with less frequently altered hydrological regimes. Occupancy models highlighted local‐ and landscape‐level characteristics as important correlates for wetland occupancy by marsh birds. Wetlands with frequently altered hydrological regimes had more open water cover and less tall vegetation present, conditions that were negatively associated with occupancy. Altered wetlands in this study were farther from the next nearest wetland, which was also negatively associated with occupancy. We suggest reservoir management is altering vegetation communities within these wetlands, indirectly promoting lower occupancy of secretive marsh bird species.

Richness and Elevation Patterns of a Stonefly (Insecta, Plecoptera) Community of a Southern Appalachian Mountains Watershed, USA

Protected areas are relatively free of human disturbance, are especially common in montane regions, and provide opportunities to study native fauna and flora. Stoneflies are model organisms to assess present and future environmental changes. While stoneflies inhabit cold lakes and a wide size range of lotic systems, diversity is greatest in streams draining mountain landscapes. This study addressed seasonal and elevation patterns of a stonefly fauna inhabiting a protected landscape draining the eastern flank of Mount Mitchell, the highest point of the Appalachian Mountains, USA. In total, 58 species were collected with estimated richness values ranging from 63 to 65. Species determinations were assisted with an integrative molecular approach using the mitochondrial barcode gene. Sampling during spring yielded the most species seasonally. Although certain species were only found at lower or higher sites, several were collected from across a broad range of elevations. Roughly 1/3 (21 = 36%) of the fauna present is known only from the southern Appalachian Highlands region, including one species described as new during this study. The assemblage reported here, however, did not closely align with other Appalachian fauna. Overall, well-structured faunal research continues to be important in light of continuing habitat modifications and climate change.

Erosion of heterogeneous rock drives diversification of Appalachian fishes.

The high levels of biodiversity supported by mountains suggest a possible link between geologic processes and biological evolution. Freshwater biodiversity is high not only in tectonically active settings but also in tectonically quiescent montane regions such as the Appalachian Mountains. We show that erosion through different rock types drove allopatric divergence between lineages of the Greenfin Darter (Nothonotus chlorobranchius), a fish species endemic to rivers draining metamorphic rocks in the Tennessee River basin in the United States. In the past, metamorphic rock preferred by N. chlorobranchius was more widespread, but as erosion exposed other rock types, lineages of this species were progressively isolated in tributaries farther upstream, where metamorphic rock remained. Our results suggest a geologic mechanism for initiating allopatric diversification in mountains long after tectonic activity ceases.

New records of hump-nosed viper Hypnale nepa from the Horton Plains, Sri Lanka

The Sri Lankan Hump-nosed Viper, Hypnale nepa (Laurenti, 1768) is an endemic species restricted to montane regions above 900 m in Sri Lanka. The Horton Plains is a national park and a montane forest (alt. 2,100–2,300 m a.s.l.) mostly covered by wet grasslands. Faunal surveys carried out in the Horton Plains have so far recorded only three species of snakes: Aspidura trachyprocta, A. copei, and Ptyas mucosa. Herein, we confirm a fourth snake species, and the first photographic

Hydrological response of a headwater catchment in Southeast Brazil—Threshold patterns of stormflow response

AbstractHeadwater catchments are essential water sources for sustaining low flow in downstream rivers. The montane region of Serra da Mantiqueira in Southeast Brazil is the largest water supplier for the densely populated area of São Paulo, where we investigated the hydrological response of a subtropical catchment and four of its sub‐catchments. We discussed the relationships between rainfall, streamflow, baseflow, stormflow, soil moisture, and water table depth using high‐frequency field observations over 4 years. Baseflow accounted for most of the streamflow during the dry season and for half of streamflow in the wet season. In contrast, the variations in soil moisture were dampened, with increases in the early wet season preceding the increase in streamflow and decreases in the late wet season following the decrease in streamflow. The mean runoff coefficient and baseflow index varied from 23% to 37% and from 62% to 75% across the catchments, respectively. At the event scale, all catchments had a pronounced threshold behaviour, where stormflow increased sharply when event precipitation reached ≃10 mm, soil moisture reached ≃51% and water table depth decreased to ≃135 cm. The event stormflow coefficient was highly variable, with a maximum of 25%. The temporally integrated stormflow coefficient was low for conditions below a soil moisture threshold (≃3%–10%) and high above a soil moisture threshold (≃8%–15%). Our estimates of flows and threshold behaviours were consistent across the various study catchments, improving our understanding of runoff generation at a catchment scale. This information should help improve the management of water resources focused on water and food security in a context of climate change.

An increasing trend of inorganic nitrogen deposition across montane regions of China

China has experienced a dramatic increase in the total inorganic nitrogen (TIN) deposition rate over the past three decades and has become one of the hotspots of N deposition worldwide. However, the status and trends of TIN deposition across Chinese mountain regions, which occupy over 60% of the land area of China, are still unclear. Here, we established a time series dataset of TIN deposition across Chinese mountains by data collection to evaluate the status and tendency of TIN deposition in mountain regions. The average TIN deposition flux in the mountains was approximately 9.62 kg N/ha/yr, with a maximum value of 23.49 kg N/ha/yr found in northern montane regions. There was a significant increasing trend of TIN deposition during the last two decades across China's montane regions (p < 0.05), different from the decreasing temporal trend from cropland/city sites. The temporal pattern of TIN deposition in montane areas was spatial and elevation dependent, showing an obvious increasing trend in both Southwest and Northeast Chinese montane areas and in the montane areas with lower (<1000 m. asl) and middle (1000–3000 m. asl) elevations. Our results highlighted the different temporal trends of TIN deposition in China's mountain regions from cropland/city areas, which should be considered in earth system models and environmental policy-making.

A re-assessment of diversity among Philippine gymnures (Mammalia: Erinaceidae: Podogymnura), with a new species from eastern Mindanao

Podogymnura, a Philippine endemic genus of gymnures ("soft-furred hedgehogs"), has been known previously only from the highlands of central Mindanao (P. truei truei and P. t. minima) and from two small islands off the northeast tip of Mindanao (P. aureospinula). Based on a combination of mitochondrial genetic and qualitative and quantitative morphological data, we recognize P. minima, formerly considered a subspecies of P. truei, as a distinct species. We also recognize specimens from two little-studied montane regions of southeastern Mindanao, Mt. Hamiguitan and Mt. Kampalili, as a distinctive new species, P. intermedia n. sp. We estimate that dispersal of a common ancestor from Borneo to Mindanao ca. 1.9 to 3.5 Ma gave rise to Podogymnura, followed by speciation within Mindanao beginning 0.53 to 0.97 Ma. These results further increase the rich diversity of mammals on Mindanao, and underscore the importance of the eastern Mindanao highlands as a likely important but little-studied center of Philippine mammalian diversity.

Dynamic Characteristics of Vegetation Change Based on Reconstructed Heterogenous NDVI in Seismic Regions

The need to protect forests and enhance the capacity of mountain ecosystems is highlighted in the U.N.’s Sustainable Development Goal (SDG) 15. The worst-hit areas of the 2008 Wenchuan Earthquake in southwest China were mountainous regions with high biodiversity and the impacted area is typical of other montane regions, with the need for detecting vegetation changes following the impacts of catastrophes. While the widely used remotely sensed vegetation indicator NDVI is available from various satellite data sources, these satellites are available for different monitoring periods and durations. Combining these datasets proved challenging to make a continuous characterization of vegetation change over an extended time period. In this study, compared with linear regression, multiple linear regression, and random forest, Convolutional Neural Networks (CNNs) performed best with an average R2 of 0.819 (leave-one-out cross-validation). Thus, the CNNs model was selected to establish the map of the overlapping periods of two remote-sensing products: SPOT-VGT NDVI and PROBA-V NDVI, to reconstruct a SPOT-VGT NDVI for the period from June 2014 to December 2018 in the worst-hit areas of the Wenchuan earthquake. We analyzed the original and reconstructed SPOT-VGT NDVI in the hard-hit areas of the Wenchuan earthquake from 1999 to 2018, and we concluded that NDVI showed an overall upward trend throughout the study period, but experienced a sharp decline in 2008 and reached its lowest value a year later (2009). Vegetation recovery was rapid from 2009 until 2011 after which, it returned to a pattern of slower natural growth (2012–2018). The Longmenshan fault zone experienced the greatest vegetation damage and initiation of recovery there has caused the overall regional average recovery to lag by 1–2 years. In areas where the land was denuded of vegetation (i.e., effectively all vegetation was stripped from the surface) after the earthquake, the damage exceeded what was experienced anywhere else in the entire study area, and by 2018 it remained unrestored. In the 15 years since the earthquake, the areas that were denuded were expected to recover to the level of restoration equivalent with the NDVI of 2007, as was the case in other earthquake-damaged regions. In addition to the earthquake and the immediate loss of vegetation, the Chinese government’s Grain for Green Policy, the elevation ranges within the region, the forest’s phenological conditions, and human activities all had an impact on vegetation recovery and restoration. The reconstructed NDVI provides a long-term continuous record, which contributes to the identifying changes that are improving predictive forest recovery models and to better vegetation management following catastrophic disturbances, such as earthquakes.