Major Vegetation Types Research Articles

Assessing two decades of landscape greenness in relation to temperature and precipitation in a tropical dry forest of Northwestern Mexico

Canopy greenness is an indicator of ecosystem primary productivity, which is often limited by temperature and precipitation. Changes in vegetation greening have been reported mostly at global scales. However, we still have a poor understanding of vegetation greening patterns and drivers for major vegetation types, such as the tropical dry forest, one of the most extensive vegetation types in Mexico. Here, we analyze two decades of interannual variation in greenness and its relationship to temperature and precipitation in the northmost neotropical dry forest occurring in Northwestern Mexico. We constructed time-series linear regression models using standardized anomalies with z-scores (i.e., standard deviations away from the long-term mean) for the Normalized Difference Vegetation Index (NDVI) and the climate data from 2001 to 2021. Our best models indicate both temperature and precipitation exert positive effects on vegetation greenness, particularly from a lagged effect perspective, as retained predictors were the accumulated precipitation of two monsoon (summer) seasons and previous year mean temperature. The lowest levels of landscape greenness seem connected to prolonged droughts and extreme frost events. In fact, a switch from negative to positive NDVI anomalies was observed in the years following the February 2011 extreme frost that affected much of North America, including northern Mexico. Notable, under the stricter statistical criterion of −1.7 ≥ z score ≥ 1.7, only climatic variables presented very-extreme anomalies and these were not necessarily linked to a very-extreme response in landscape greenness. However, considering the criterion of −1.3 ≥ z score ≥ 1.3, we identified several extreme NDVI anomalies and their corresponding climatic anomaly. Therefore, more flexible statistical criteria might reveal climate extremes of ecological and social relevance. Our overall findings have implications for forest and climate risk management, particularly as extreme climatic anomalies are expected to continue increasing in light of climate change.

A record of late Holocene sea level and human impacts from the southeastern Coast of Sri Lanka

AMS radiocarbon-dated palynological evidence from Embilikala Lagoon in Bundala National Park (one of the Ramsar wetland sites) on the southeast coast of Sri Lanka indicates palaeoenvironmental changes during the last 2,700 years. The persistence of fewer mangroves (eg Rhizophoraceae taxa) suggests that sea level low stands occurred between 2,700 and 1750 cal yr BP. From the later age, the relative sea level rose, and reached the present sea level at 950 cal yr BP as indicated by the mangrove maximum. At 2,250, 700–400 and 200–150 cal yr BP, the sudden increase in marine dinoflagellate cysts (eg Spiniferites mirabilis) and foraminifera (Globigerinoides ruber) suggests increased marine influence. This is consistent with a decrease in mangrove habitats. Between 2,700 and 950 cal yr BP, severely degraded dry monsoon forests and minimal levels mangrove suggest human and marine influences were the critical drivers for changing the major vegetation types along the southeastern coast. Vegetation changes have been drastic over the last millennia.

Constraints of commercially available seed diversity in restoration: Implications for plant functional diversity

Societal Impact StatementLarge quantities of diverse native seeds are required to scale up global restoration efforts. However, it remains unclear for many ecosystems how the diversity of available seed in commercial stocks reflects the composition of the ecosystems where vegetation is being remade. This study highlights existing shortfalls in the diversity of seed presently available for use in restoration and identifies gaps in the seed supply chain while providing a new method for optimising species selection given these constraints. This work underscores how improved collaboration between stakeholders is required to strengthen the seed supply chain and help remake functionally diverse vegetation.Summary Restoration using native seed is frequently implemented to restore degraded ecosystems. However, it remains unclear how constraints on the diversity of germplasm available for use in restoration may limit the recovery of both species and plant functional diversity. Using a dataset of seed availability for Australia's major vegetation types, we explore variation in the diversity and breadth of functional traits (leaf mass per area, seed mass, plant height) for species where seed is available on commercial markets relative to unavailable. Using these data, we simulate theoretical seed mixes derived from two species pools: (1) constrained by the current market of commercially available seed, and (2) assuming all native species can be planted; then we compare differences in functional diversity (dispersion) as an exercise to explore possible limitations within the current seed supply. Seed from only 12% of Australian plant species (2992 species) is presently available for immediate purchase. Seed was more frequently available for trees and shrubs than for understorey species. Available species were on average taller, with thicker, longer‐lived leaves than unavailable species. Overall, functional dispersion was lower for seed mixes generated using available seed compared with those drawn from all species. Solutions are required to address seed shortfalls so that plantings are not only species rich but also functionally diverse. We develop two options: (1) quantifying and addressing gaps in the seed supply chain that currently limit the capacity for practitioners to restore diverse vegetation; and (2) applying a trait‐informed species‐selection method to plantings that maximises functional diversity using available seed.

Assessing the suitability of a surveillance fauna-monitoring program for detecting future changes in reptile occupancy

Context Ecological surveillance monitoring typically targets multiple taxonomic groups by using standardised sampling across large spatial scales. Although surveillance monitoring confers advantages over hypothesis-driven monitoring in its broad taxonomic and spatial scope, the approach has been criticised for its disconnect from ecological management and failure to provide insights on the drivers of ecological change Aims To assess the adequacy of a plot-based general fauna-monitoring program for sampling reptiles as indicators of ecosystem health in a semi-arid upland region of the Northern Territory, Australia. Methods We surveyed reptiles at 90 sites, stratified between major landform and vegetation types, and using standard fauna-sampling methods, across the 2568 km2 Tjoritja National Park in the MacDonnell Ranges. We compiled a full inventory of the reptile fauna of the study area and identified species with potential utility as ecological indicators. We then used single-season occupancy models and power analyses to evaluate the adequacy of sampling for detecting potential future changes in occupancy. Key results We detected 57 of the 68 reptile species known from the protected area, 17 of which are potentially useful indicators of ecological health, mostly related to fire management. There was insufficient power to detect moderate (50%) future changes in reptile occupancy for all but the single most detected species. For the two ecological indicator species with sufficient detections for occupancy modelling, a positive association with a keystone structure (dense spinifex grass) was confirmed. However, increasing detection probability or the number of surveys would result in only minor improvements in power to detect occupancy change in these species. Conclusions Although reptiles are potentially useful indicators of ecological health, particularly in relation to fire regimes, the number of sites required to detect future changes in reptile occupancy by using standardised plot-based monitoring in this protected area is prohibitively high. Implications Our results suggest that once ecological associations are understood, monitoring ecological health remotely by using techniques such as fire-scar mapping to track proportions of long-unburnt vegetation should be considered over labour-intensive surveillance monitoring for reptiles. Targeted monitoring of threatened and other reptile species of conservation or cultural concern may also be warranted.

Ants of Uluru-Kata Tjuta National Park in arid Australia: Diversity, faunistic composition and habitat associations

Inland Australia supports by far the world's most diverse arid-adapted ant fauna, but there are no published studies of regional ant faunas from the central arid zone. Here we describe the ants collected by pitfall trapping at 22 sites in World Heritage-listed Uluru-Kata Tjuta National Park (300 mm mean annual rainfall), representing all major vegetation types from spinifex grasslands to eucalypt woodlands. A total of 154 (mostly undescribed) ant species from 26 genera were recorded, with the richest genera being Melophorus (30 species), Monomorium (26), Iridomyrmex (18) and Camponotus (12). The pattern of species accumulation suggests that many more species remain to be collected from the Park, and we estimate that the total fauna consists of around 300 species. The most abundant ants were species of Iridomyrmex (collectively contributing 76% of all ants collected), as is the case throughout arid Australia. Species of Monomorium and Melophorus were also highly abundant. No exotic species were recorded. Ant species composition was strongly related to vegetation type, with a particular distinction between the various grasslands on one hand, and woodlands on the other. Unexpectedly, species richness was higher in structurally simple spinifex grasslands than in eucalypt woodlands. The woodland fauna lacks many taxa characteristic of such habitats in similarly arid regions of southern Australia, which we attribute to remoteness and small patch size. Uluru-Kata Tjuta National Park supports an extremely diverse ant fauna, but surveys of other areas are required for an improved understanding of patterns of ant biodiversity in Australia's central arid zone.

Monitoring Grassland Variation in a Typical Area of the Qinghai Lake Basin Using 30 m Annual Maximum NDVI Data

The normalized difference vegetation index (NDVI) can depict the status of vegetation growth and coverage in grasslands, whereas coarse spatial resolution, cloud cover, and vegetation phenology limit its applicability in fine-scale research, especially in areas covering various vegetation or in fragmented landscapes. In this study, a methodology was developed for obtaining the 30 m annual maximum NDVI to overcome these shortcomings. First, the Landsat NDVI was simulated by fusing Landsat and MODIS NDVI by using the enhanced spatial and temporal adaptive reflectance fusion model (ESTARFM), and then a single-peaked symmetric logistic model was employed to fit the Landsat NDVI data and derive the maximum NDVI in a year. The annual maximum NDVI was then used as a season-independent substitute to monitor grassland variation from 2001 to 2022 in a typical area covering the major vegetation types in the Qinghai Lake Basin. The major conclusions are as follows: (1) Our method for reconstructing the NDVI time series yielded higher accuracy than the existing dataset. The root mean square error (RMSE) for 91.8% of the pixels was less than 0.1. (2) The annual maximum NDVI from 2001 to 2022 exhibited spatial distribution characteristics, with higher values in the northern and southern regions and lower values in the central area. In addition, the earlier vegetation growth maximum dates were related to the vegetation type and accompanied by higher NDVI maxima in the study area. (3) The overall interannual variation showed a slight increasing trend from 2001 to 2022, and the degraded area was characterized as patches and was dominated by Alpine kobresia spp., Forb Meadow, whose change resulted from a combination of permafrost degradation, overgrazing, and rodent infestation and should be given more attention in the Qinghai Lake Basin.

Modern pollen rain reveals differences across forests, open and mosaic landscapes in Madagascar

Societal Impact StatementPalaeoecological investigations are crucial in understanding millennial to centennial land use and land cover change. By analysing the modern pollen rain from four main vegetation types across Madagascar, this research provides baselines for improving the interpretation of pollen records in palaeoecological studies. This study determines the modern pollen‐vegetation relationship in Madagascar and gives a better understanding of the island's landscapes. Despite some spatial limitations, this approach contributes to resolving the debated topic related to the origin of Madagascar's open ecosystems. Knowing the vegetation history prior to and after human settlement would help guide biodiversity management and its associated ecosystem services.Summary Modern pollen rain contributes to calibrating and defining palaeo‐records relative to the current vegetation of diverse landscapes. Quantifying past vegetation change is important to better frame sustainable and resilient management methods of biodiversity considering human needs. In this paper, we aim to assess modern pollen assemblages in different vegetation types in Madagascar and inform how these could contribute to the interpretation of palaeo‐records. We identified modern pollen assemblages from 21 samples across four major vegetation types in Madagascar, including seven (N = 7) newly generated samples from the tropical dry forest in the Northwest region and 14 datasets downloaded from the African Pollen Database website. The downloaded datasets are from core tops representing modern vegetation previously analysed in the tropical dry forests and spiny thickets, the wooded grassland–bushland mosaic and the littoral humid forest. We evaluated the frequency of different taxa in the samples and conducted multivariate analyses to evaluate the similarities and ecological affinities between samples. Pollen rain reflected the main vegetation types across Madagascar and provided information on the current structure and state of the landscape. Regarding the interpretation of pollen records, pollen rain samples revealed that: (i) Open mosaic ecosystems should contain a percentage of at least 40% grass pollen, informing on the origin of the vegetation in older samples and the state of degradation in more recent vegetation reconstructions; and (ii) Anthropogenic vegetation such as plantations are marked by the abundance of pioneer taxa such as Pinus and/or Eucalyptus spp. with a frequency >20%. Our findings improve the interpretations of pollen records and help differentiate past distribution of forest, open and mosaic vegetation, in Madagascar. It will contribute to further research on human practices, land use and into scenarios of conservation planning not only in Madagascar but also across the tropics.

Plant diversity in secondary, montane grasslands – a case study of the abandoned plantations of Mariepskop Mountain, South Africa

Grasslands are one of the most threatened terrestrial ecosystem types, and montane grasslands of particular conservation concern. Despite high rates of transformation in recent decades, croplands and plantations are being abandoned in parts of many countries, creating an opportunity for conservation of montane grasslands through restoration. We report on the changes in the cover of major vegetation types (indigenous forest, grassland, and plantations) between 1935 and 2022, in an area that was intensively afforested from 1930 to 1960 and abandoned in 2000. Montane grassland at the site declined from over 50% of all landcover to below 15%, but subsequently recovered to 30% within 20 years. Many former plantations developed into secondary grassland with estimated gamma plant species richness of 231 for herbaceous species and 45 for savanna species. These are high values considering the size of the study area (4000 ha), and comparable to estimates from primary grassland sites in the broader region. However, at the scale of 1 m2 sampling quadrats, richness in the secondary grasslands was below that recorded in the last remaining patches of primary grassland at the site (means of 2.6 versus 4.7 for graminoid species, and 1.9 versus 2.9 for forbs). Some of the former Eucalyptus plantations had transformed into novel savannas dominated by fire-tolerant, resprouting trees, and may require more active restoration. Secondary grasslands such as those reported on here could potentially make a significant contribution to the conservation of montane biodiversity over the coming decades, warranting further research (both socio-economic and ecological) on the factors that lead to abandonment and promote the emerge of secondary grasslands of high diversity.

Forest vegetation cover in Bu Gia Map National Park, Vietnam

Understanding the composition of tree species is essential for establishing conservation priorities. Bu Gia Map National Park is in the tropical rainforest zone of Southeast Vietnam. This paper is to analyse and assess tree species composition and biodiversity conservation in Bu Gia Map National Park. The diversity of plant species in Bu Gia Map National Park was studied to provide baseline information for conservation and sustainable management processes that will prolong the life of National Park. The results obtained from the study conducted on the plant species composition and forest vegetation in this national park revealed a total of 786 species, spanning 430 genera and 132 families, across three divisions of vascular plants: Polypodiophyta, Pinophyta, and Magnoliophyta. Among these are 300 species of timber plants, 270 species of medicinal plants, 62 species of edible plants, 74 species of ornamental plants, 40 species of industrial plants, 28 species of fiber plants, and 12 species of plants with unknown use. Notably, during the investigation period, Goniothalamus vietnamensis Ban and Myxopyrum smilacifolium Blume were newly recorded in the forest vegetation of Bu Gia Map National Park. The study also describes a variety of forest vegetation in the area, identifying two major forest vegetation types within Bu Gia Map National Park.

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.

Major field margin vegetation types in France and their relationships with climate, agricultural landscapes and management intensity

ABSTRACT Arable field margins are an important semi-natural habitat providing multiple functions in agroecosystems. Despite three decades of research, analyses of species assemblage and functional traits are lacking. Leveraging a national monitoring network in metropolitan France, we aim to provide a comprehensive taxonomic and functional synthesis of field margin flora, outline main field margin types and explore their associations with management practices, climate, and agricultural landscapes. We analysed data from 532 field margins surveyed between 2013 and 2017, using both uni- and multivariate analyses. Field margins exhibited great diversity with 711 distinct taxa (12% of all flora in mainland France) at the national scale and an average of 16 species per 10 m2 locally. While field margins contained few species of conservation value, they offered a refuge for many declining species as well as rare arable weed species. We identified seven main field margin types, each linked to distinct conditions of climate, soil, landscape and agricultural practices. Mediterranean field margins notably differed from all others. In the main cluster, vineyard margins also stood out as distinct from annual crop margins. Additionally, field margins in landscapes with a high proportion of grassland differed from those within intensively cultivated field crop plains in conventional agriculture. Overall, our study highlights the high botanical diversity of field margins and their interest for plant conservation in agricultural landscapes. Promoting the installation and/or maintenance of field margins through agri-environmental schemes should thus favour biodiversity conservation and associated ecosystem provision.

Continental-scale insights into the soil microbial co-occurrence networks of Australia and their environmental drivers

Soil microbial communities and their interactions play a critical role in shaping the functions of ecosystems at regional and continental scales. In recent years, co-occurrence network analyses have provided a way to investigate microbial interactions among different microorganisms. But understanding how different environmental factors shape these networks at the continental scale remains challenging. Analyzing fungal, bacterial, and archaeal data from 166 study sites across Australia, we inferred a meta-community level soil microbial co-occurrence network for the Australian continent. Additionally, we analyzed node-level and network-level topological shifts associated with the five major vegetation types. Our results indicate that soils in the Australian savannah systems harbor a unique microbial association pattern, with the highest proportion of positive linkages, highest modularity and lowest average path length in comparison to soils from other vegetation types. Multi-model approaches revealed that different environmental drivers, including soil properties, temperature, and vegetation type, regulated the spatial distribution of topological parameters of the soil microbial networks analyzed in our study. We further generated high-resolution predication maps of microbial networks for Australia, providing insight into the distribution of soil microbes across the continent. By determining how the microbial co-occurrence networks vary according to vegetation type and mapping the distribution of the key parameters of these networks across Australia, we provide a unique understanding of microbial biogeography at the continental scale.

Effects of land use and climate on web-building spiders and their prey in dry dipterocarp forests

Dry dipterocarp forest is a key dry forest type across South-East Asia. Despite these dipterocarps being endangered and widely unprotected, the factors that may affect their function at local and landscape scales are unknown. To identify drivers for future conservation programs at both local (habitat structure) and landscape (land use, climate) scales, the prey captured by web-building spiders, which are model predators in dry dipterocarps, were investigated. Overall, 21 dry dipterocarp forest stands representing the gradient of agricultural intensification were selected across North-East Thailand where captured and potential prey of web-building spiders was collected. Within each plot, the percentual coverage of major vegetation types (e.g., trees, shrubs, grass) was quantified. Around each plot, the landscape composition within a 5 km radius was quantified as the proportion of agroecosystems, forests, water bodies, and urban areas. Further, climate data for each plot were extracted from a public database. The prey captured by web-building spiders was most affected by the composition of landscapes; the evenness of captured prey showed a hump-shaped relationship with the proportion of agroecosystems in each landscape. The observed change in captured prey composition between plots was predominantly caused by changes in web type composition between local spider communities. The total number of captured prey decreased with increasing mean annual precipitation which mirrored the decline of total prey availability along this gradient. The results indicate that the predation by web-building spiders in dry dipterocarps is most threatened by changes in rainfall pattern and land-use change, specifically by agricultural intensification at the landscape scale.

Identifying key landscape pattern indices influencing the NPP: A case study of the upper and middle reaches of the Yellow River

Human activities and climate change directly affect the composition, structure, and function of ecosystems and, consequently, their net primary productivity (NPP). In this study, we explored the response relationships between landscape pattern indices and NPP changes in three major vegetation types (forest, grassland, and shrubland) in the upper and middle reaches of the Yellow River Basin using a random forest model. The results showed that landscape fragmentation increased, leading to higher landscape heterogeneity and edge effects. Patch shapes became more irregular, and spatial distribution became more dispersed. From 2000 to 2015, both vegetation types and NPP showed significant spatial heterogeneity in the study area. The number of patches (NP), largest patch index (LPI), and percent-like adjacency (PLADJ) metrics were used to determine the core landscape characteristics to assess the NPP changes in forest, shrubland, and grassland, respectively. This study provides a basis for understanding the relationships among landscape patterns, vegetation types, and NPP and serves as a reference for developing NPP predictive models in the Loess Plateau region.

Effects of root plates, pits and mounds following windthrow events on the biodiversity of plants and lichens in Central European mountain forests

Windthrows lead to the formation of a characteristic land microtopography and they provide new habitats and substrata for species. The present study is novel, because it concerns different taxonomic groups of organisms and effects of various variables on species composition, richness and abundance within root plate-pit-mound (RPM) complexes. For the first time we studied lichens, liverworts, mosses and vascular plants on RPM complexes across major vegetation types, from deciduous to coniferous forests. We analyzed 164 RPM complexes which included in total 268 components: 115 root plates, 80 pits and 73 mounds. Besides the vegetation types and component types the following variables were also considered: dimensions (area, size), age (decomposition degree), species of the uprooted tree, shade, and elevation. The research revealed that root plates, pits and mounds had their own indicator species, but the key factors for the species composition were the species of uprooted trees and the vegetation type. Furthermore, the type of component and the vegetation type were also the most main variables determining the richness and abundance of the studied taxonomic groups of species. Analyses revealed the greatest species richness and abundance of lichens on root plates, and the highest richness of liverworts and vascular plants in pits. The type of component had no effect on the species richness of mosses. However, they were most abundant on mounds. The response of individual groups to the vegetation types and other variables varied. Findings from the study indicated that the presence of uprooted trees with different features (size and age, species of uprooted tree) is important for the biodiversity of mountain forests. We recommend leaving uprooted trees in forest communities for natural colonization, preferably large objects. Moreover, in managed forests a mosaic of forest communities that mimic the structure of natural unmanaged forests should be supported.

Distribution Pattern and Management Strategy of Invasive Weed Parthenium hysterophorus L. in Gorakhpur, India

Background: Parthenium hysterophorus L. (Family Asteraceae, local name Chatakchandni), an invader weed, assumes importance and poses a problem because of its nuisance value. The present study accounts for its population structure, community relation and its probable association with neighbour species within the major grassland vegetation types of the region. Materials and Methods: For the study of population status, phytosociological characters, neighbour relations of Parthenium and its contribution to the two major grasslands’ the managed and natural were calculated by the standard sampling methods. Results: Highly disturbed or completely cleaned sites may be fast colonized and aggregated by Parthenium, as evident from the values of its phytosociological attributes. In natural grassland, however, the number of species as the nearest neighbour of Parthenium was quite high. Parthenium was found to occur at all different stages of growth and at every stage of its life cycle throughout the year. In the months of July, November and March, a much greater number of individuals were in the seedling stage. Conclusion: Since there is no lapse period between seed dispersal and germination, effective management may be exercised only before they enter the reproductive phase. Since there is no mode of asexual regeneration in this species, manual elimination must be held at juvenile stage to get an area rid of this noxious weed.

Developing Spatial and Temporal Continuous Fractional Vegetation Cover Based on Landsat and Sentinel-2 Data with a Deep Learning Approach

Fractional vegetation cover (FVC) has a significant role in indicating changes in ecosystems and is useful for simulating growth processes and modeling land surfaces. The fine-resolution FVC products represent detailed vegetation cover information within fine grids. However, the long revisit cycle of satellites with fine-resolution sensors and cloud contamination has resulted in poor spatial and temporal continuity. In this study, we propose to derive a spatially and temporally continuous FVC dataset by comparing multiple methods, including the data-fusion method (STARFM), curve-fitting reconstruction (S-G filtering), and deep learning prediction (Bi-LSTM). By combining Landsat and Sentinel-2 data, the integrated FVC was used to construct the initial input of fine-resolution FVC with gaps. The results showed that the FVC of gaps were estimated and time-series FVC was reconstructed. The Bi-LSTM method was the most effective and achieved the highest accuracy (R2 = 0.857), followed by the data-fusion method (R2 = 0.709) and curve-fitting method (R2 = 0.705), and the optimal time step was 3. The inclusion of relevant variables in the Bi-LSTM model, including LAI, albedo, and FAPAR derived from coarse-resolution products, further reduced the RMSE from 5.022 to 2.797. By applying the optimized Bi-LSTM model to Hubei Province, a time series 30 m FVC dataset was generated, characterized by a spatial and temporal continuity. In terms of the major vegetation types in Hubei (e.g., evergreen and deciduous forests, grass, and cropland), the seasonal trends as well as the spatial details were captured by the reconstructed 30 m FVC. It was concluded that the proposed method was applicable to reconstruct the time-series FVC over a large spatial scale, and the produced fine-resolution dataset can support the data needed by many Earth system science studies.

Tracking Changes in Vegetation Structure Following Fire in the Cerrado Biome Using ICESat‐2

AbstractFires mediate grass and tree competition and alter vegetation structure in savanna ecosystems, with important implications for regional carbon, water, and energy fluxes. However, direct observations of how fire frequency influences vegetation structure and post‐fire recovery have been limited to small experimental field studies. Here, we combined lidar‐derived canopy height and canopy cover from NASA's Ice, Cloud, and land Elevation Satellite‐2 with over two decades of burned area data from the Moderate Resolution Imaging Spectroradiometer sensors to provide the first biome‐wide estimates of post‐fire changes in canopy structure for major vegetation types in the Cerrado (Brazil). Mean canopy height decreased with increasing burn frequency for all natural cover types, with the greatest decline observed for forests and savannas. The ability to separate changes in fractional canopy cover from height growth using lidar data highlighted the long‐time scales of vegetation recovery in forests and savannas after fire. For forests in medium and high precipitation areas, canopy cover returned to unburned values within 5 years following fire, whereas mean canopy height remained below unburned values, even in the oldest fires (14–20 years). Recovery times increased with decreasing rainfall, with average values of both fractional cover and canopy height below unburned areas after 14–20 years for savannas. We observed gradual recovery of vegetation height and cover over decades, even in mesic or wet savanna regions like the Cerrado. Infrequent fire activity, particularly in areas with greater land management, influences ecosystem structure across the biome, with important consequences for biodiversity conservation.

Identifying the Responses of Vegetation Gross Primary Productivity and Water Use Efficiency to Climate Change under Different Aridity Gradients across China

Despite the fact that gross primary productivity (GPP) and water use efficiency (WUE) have been widely used as indicators to evaluate the water-carbon cycle, uncertainties exist in the patterns of GPP and WUE responses to climate variability along different aridity gradients. In this study, the aridity index was used to divide China into four arid-humid zones. The spatiotemporal variability of multiple vegetation types GPP and WUE in response to climate change under different arid-humid zones were investigated based on remote sensing data. The results indicated that the increasing trend of WUE in the four arid-humid zones of China was less pronounced than GPP from 2001 to 2021. The GPP value decreased gradually from the humid to the arid zone, and the WUE value in the arid zone was slightly higher than in the semi-arid zone. The GPP of all vegetation types in China showed a tendency to increase, while shrubland and wetland WUE tended to decrease. The major vegetation types (e.g., forest, cropland and grassland) in each aridity gradient contributed to the changes in local GPP and WUE. However, in individual arid-humid zones, wetland and shrubland also exhibited high GPP and WUE values that were not inferior to forest and cropland. Temperature and precipitation were the main climatic factors responsible for the increase in vegetation GPP in different aridity gradients, with a higher positive correlation for temperature than precipitation. WUE showed a distinct positive and negative correlation with the thermal factors (temperature and net radiation) and the moisture factors (precipitation and relative humidity); this pattern was more pronounced in the humid and semi-humid zones. Net radiation and precipitation may be the main climatic factors causing a slight upward trend in WUE across the arid-humid zones, while the decrease in shrubland and wetland WUE may be related to relative humidity and precipitation.

Estimating fractional cover of saltmarsh vegetation species in coastal wetlands in the Yellow River Delta, China using ensemble learning model

Saltmarshes in coastal wetlands provide important ecosystem services. Satellite remote sensing has been widely used for mapping and classification of saltmarsh vegetation, however, medium-spatial-resolution satellite datasets such as Landsat-series imagery may induce mixed pixel problems over saltmarsh landscapes which are spatially heterogeneous. Sub-pixel fractional cover estimation of saltmarsh vegetation at species level are required to better understand the distribution and canopy structure of saltmarsh vegetation. In this study, we presented an approach framework for estimating and mapping the fractional cover of major saltmarsh species in the Yellow River Delta, China based on time series Landsat 8 Operational Land Imager data. To solve the problem that the coastal area is frequently covered by clouds, we adopted the recently developed virtual image-based cloud removal (VICR) algorithm to reconstruct missing image values under the cloud/cloud shadows over the time series Landsat imagery. Then, we developed an ensemble learning model (ELM), which incorporates Random Forest Regression (RFR), K-Nearest Neighbor Regression (KNNR) and Gradient Boosted Regression Tree (GBRT) based on temporal-spectral features derived from the time-series cloudless images to estimate the fractional cover of major vegetation types, i.e., Phragmites australis, Suaeda salsa and the invasive species, Spartina alterniflora. High spatial resolution imagery acquired by the Unmanned Aerial Vehicle and Gaofen-6 satellites were used for reference sample collections. The results showed that our approach successfully estimated the fractional cover of each saltmarsh species (average of R-square:0.891, RMSE: 7.48%). Through four scenarios of experiments, we found that the ELM is advantageous over each individual model. When the images during key months were absent, cloud removal for the Landsat images considerably improved the estimation accuracies. In the study area, Spartina alterniflora covers the largest area (5753.97 ha), followed by Phragmites australis with spatial extent area of 4208.4 ha and Suaeda salsa of 1984.41 ha. The average fractional cover of S. alterniflora was 58.45%, that of P. australis was 51.64% and that of S.salsa was 51.64%.