DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Integrating very-high-resolution imagery, Sentinel-2 time-series data, and machine learning to map shrub fractional abundance across arid and semi-arid ecosystems in China

Journal Article · · Remote Sensing of Environment
 [1];  [1];  [2];  [3];  [3]; ORCiD logo [4];  [1];  [1];  [1];  [5];  [5];  [1];  [1];  [6];  [7];  [1];  [8];  [5];  [5];  [2] more »;  [9] « less
  1. University of Hong Kong, Pokfulam (Hong Kong)
  2. Beijing Normal University, Beijing (China); Moganshan Geospatial Information Laboratory, Deqing (China)
  3. Global Ecology Unit (CREAF-CSIC-UAB), Catalonia (Spain)
  4. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
  5. Chinese Academy of Sciences (CAS), Beijing (China); University of Chinese Academy of Sciences, Beijing (China)
  6. Southeast University, Nanjing (China)
  7. Nanjing Agricultural University (China)
  8. Chinese Academy of Sciences (CAS), Beijing (China)
  9. University of Hong Kong, Pokfulam (Hong Kong); State Key Laboratory of Agrobiotechnology (CUHK), Shatin (Hong Kong)

Shrub fractional abundance (SFA), the proportion of shrub cover per unit area, serves as a critical indicator of environmental aridity and ecosystem health in arid and semi-arid regions, particularly across the Mongolian steppe. However, large-scale SFA mapping in Mongolian steppe ecosystems remains challenging due to the small crown size of shrubs, their sparse distribution, and spectral overlap with coexisting low vegetation (e.g., grasses and herbs), which hinders accurate detection using coarser-resolution satellite data or traditional field surveys. To address these challenges, we developed a two-step approach that integrates very-high-resolution (VHR) imagery, time-series Sentinel-2 data, and deep learning techniques. First, we generated high-accuracy benchmark maps of individual shrub crowns from 0.5 m VHR imagery by combining manual segmentation with a hybrid deep learning framework (Dino V2 and convolutional neural networks). Second, we used these shrub crown maps as training data to build an XGBoost model for predicting SFA from 20 m Sentinel-2 time-series data, leveraging phenological information to improve estimation. We validated our approach across 70 sites (1km2 each) in the Inner Mongolia Autonomous Region, which is representative of Mongolian steppe ecosystems. From VHR imagery, we mapped 1.31 million shrub crowns with an accuracy of R2 = 0.92. Scaling up with Sentinel-2 data yielded regional SFA maps with an R2 = 0.60. Further SHAP (SHapley Additive exPlanations) analysis on the developed XGBoost model revealed that phenological metrics (particularly observations in early-May, mid-July, and late-September), which distinguish shrub phenology from that of other land cover types (e.g., grasses and bare soil), were the most influential predictors of SFA. Finally, our regional SFA maps uncovered unimodal relationships between shrub distribution and climate variables, peaking at mean annual minimum temperatures near 0 °C and annual precipitation around 200 mm. Collectively, these findings demonstrate how the integration of multi-source remote sensing and machine learning can overcome historical limitations in SFA mapping, enabling accurate, spatially continuous assessments across vast Inner-Mongolian steppe ecosystems. Our framework has the potential to be applied to other steppe ecosystems and dryland ecosystems across the Mongolian steppe and beyond, offering a foundation for improved monitoring and ecological impact assessments in the face of global climate changes.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Laboratory Directed Research and Development (LDRD) Program
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
3020931
Journal Information:
Remote Sensing of Environment, Journal Name: Remote Sensing of Environment Vol. 335; ISSN 0034-4257
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

References (91)

A synthetic review of feedbacks and drivers of shrub encroachment in arid grasslands: FEEDBACKS AND DRIVERS OF SHRUB ENCROACHMENT journal October 2011
Innovation in rangeland monitoring: annual, 30 m, plant functional type percent cover maps for U.S. rangelands, 1984-2017 journal September 2018
Critical transition to woody plant dominance through microclimate feedbacks in North American coastal ecosystems journal June 2020
Precipitation versus temperature as phenology controls in drylands journal July 2022
Shrub encroachment impaired the structure and functioning of alpine meadow communities on the Qinghai–Tibetan Plateau journal May 2022
A Biogeophysical Approach for Automated SWIR Unmixing of Soils and Vegetation journal October 2000
Practical limits on hyperspectral vegetation discrimination in arid and semiarid environments journal August 2001
Effect of shrub encroachment on land surface temperature in semi-arid areas of temperate regions of the Northern Hemisphere journal June 2022
Changes in soil enzymes related to C and N cycle and in soil C and N content under prolonged warming and drought in a Mediterranean shrubland journal June 2008
Estimation of shrub willow biophysical parameters across time and space from Sentinel-2 and unmanned aerial system (UAS) data journal October 2022
Global land cover mapping at 30m resolution: A POK-based operational approach journal May 2015
Mapping fractional woody cover in semi-arid savannahs using multi-seasonal composites from Landsat data journal May 2018
A spectral-temporal constrained deep learning method for tree species mapping of plantation forests using time series Sentinel-2 imagery journal October 2023
Estimating fractional snow cover from MODIS using the normalized difference snow index journal February 2004
Reflectance assessment of seasonal and annual changes in biomass and CO2 uptake of a Mediterranean shrubland submitted to experimental warming and drought journal April 2004
Object-oriented image analysis for mapping shrub encroachment from 1937 to 2003 in southern New Mexico journal October 2004
A comparison of multi-spectral, multi-angular, and multi-temporal remote sensing datasets for fractional shrub canopy mapping in Arctic Alaska journal July 2010
Detecting trends in forest disturbance and recovery using yearly Landsat time series: 1. LandTrendr — Temporal segmentation algorithms journal December 2010
Sentinel-2: ESA's Optical High-Resolution Mission for GMES Operational Services journal May 2012
Estimating the fractional cover of growth forms and bare surface in savannas. A multi-resolution approach based on regression tree ensembles journal February 2013
Continuous change detection and classification of land cover using all available Landsat data journal March 2014
Characterization of shrubland ecosystem components as continuous fields in the northwest United States journal October 2015
Woody plant cover estimation in drylands from Earth Observation based seasonal metrics journal January 2016
Assessing woody vegetation trends in Sahelian drylands using MODIS based seasonal metrics journal September 2016
Mapping continuous fields of tree and shrub cover across the Gran Chaco using Landsat 8 and Sentinel-1 data journal October 2018
Estimating the age and population structure of encroaching shrubs in arid/semiarid grasslands using high spatial resolution remote sensing imagery journal October 2018
Characterizing 32 years of shrub cover dynamics in southern Portugal using annual Landsat composites and machine learning regression modeling journal December 2018
Machine learning and multi-sensor based modelling of woody vegetation in the Molopo Area, South Africa journal March 2019
From woody cover to woody canopies: How Sentinel-1 and Sentinel-2 data advance the mapping of woody plants in savannas journal December 2019
Continental-scale land surface phenology from harmonized Landsat 8 and Sentinel-2 imagery journal April 2020
Disentangling fractional vegetation cover: Regression-based unmixing of simulated spaceborne imaging spectroscopy data journal September 2020
Mapping land-use intensity of grasslands in Germany with machine learning and Sentinel-2 time series journal August 2022
Cloud Mask Intercomparison eXercise (CMIX): An evaluation of cloud masking algorithms for Landsat 8 and Sentinel-2 journal June 2022
Arctic shrub expansion revealed by Landsat-derived multitemporal vegetation cover fractions in the Western Canadian Arctic journal November 2022
Evaluating fine-scale phenology from PlanetScope satellites with ground observations across temperate forests in eastern North America journal December 2022
An ecologically-constrained deep learning model for tropical leaf phenology monitoring using PlanetScope satellites journal March 2023
Integrating very-high-resolution UAS data and airborne imaging spectroscopy to map the fractional composition of Arctic plant functional types in Western Alaska journal March 2023
Modeling global indices for estimating non-photosynthetic vegetation cover journal September 2023
Very high resolution canopy height maps from RGB imagery using self-supervised vision transformer and convolutional decoder trained on aerial lidar journal January 2024
Arctic tundra shrubification can obscure increasing levels of soil erosion in NDVI assessments of land cover derived from satellite imagery journal February 2024
Cross-scale mapping of above-ground biomass and shrub dominance by integrating UAV and satellite data in temperate grassland journal April 2024
Ecoregion-wise fractional mapping of tree functional composition in temperate mixed forests with sentinel data: Integrating time-series spectral and radar data journal April 2024
Spectra-phenology integration for high-resolution, accurate, and scalable mapping of foliar functional traits using time-series Sentinel-2 data journal May 2024
Comparative validation of recent 10 m-resolution global land cover maps journal September 2024
Mapping fractional vegetation cover in Sub-Saharan rangelands using phenological feature spaces journal March 2025
Climate Warming Does Not Always Extend the Plant Growing Season in Inner Mongolian Grasslands: Evidence From a 30‐Year In Situ Observations at Eight Experimental Sites journal July 2019
Drivers of woody plant encroachment over Africa journal June 2018
More than one quarter of Africa’s tree cover is found outside areas previously classified as forest journal May 2023
Mapping the global distribution of C4 vegetation using observations and optimality theory journal February 2024
The success of woody plant removal depends on encroachment stage and plant traits journal December 2022
A high-resolution canopy height model of the Earth journal September 2023
An unexpectedly large count of trees in the West African Sahara and Sahel journal October 2020
A foundation model for clinical-grade computational pathology and rare cancers detection journal July 2024
Dynamic World, Near real-time global 10 m land use land cover mapping journal June 2022
TerraClimate, a high-resolution global dataset of monthly climate and climatic water balance from 1958–2015 journal January 2018
Estimating woody and herbaceous vegetation cover from time series satellite observations journal November 1999
Patterns of ant species richness along elevational gradients in an arid ecosystem journal March 2003
Rapid loss of lakes on the Mongolian Plateau journal February 2015
Extreme drought impacts have been underestimated in grasslands and shrublands globally journal January 2024
Stochastic Games journal October 1953
Spectral unmixing of vegetation, soil and dry carbon cover in arid regions: Comparing multispectral and hyperspectral observations journal January 2002
Google Earth as a virtual globe tool for Earth science applications at the global scale: progress and perspectives journal December 2011
Modelling gross primary production in semi-arid Inner Mongolia using MODIS imagery and eddy covariance data journal January 2013
Arctic shrubification mediates the impacts of warming climate on changes to tundra vegetation journal December 2016
Remote sensing from unoccupied aerial systems: Opportunities to enhance Arctic plant ecology in a changing climate journal August 2022
DeepForest: A Python package for RGB deep learning tree crown delineation journal October 2020
Woody encroachment: social–ecological impacts and sustainable management journal July 2024
Shrub and precipitation interactions shape functional diversity of nematode communities on the Qinghai–Tibet Plateau journal March 2023
Ericoid shrub encroachment shifts aboveground–belowground linkages in three peatlands across Europe and Western Siberia journal August 2023
Aridity‐dependent shifts in biodiversity–stability relationships but not in underlying mechanisms journal June 2024
Vegetation-microclimate feedbacks in woodland-grassland ecotones: Vegetation-microclimate feedbacks journal October 2012
Response of plant species richness and primary productivity in shrublands along a north–south gradient in Europe to seven years of experimental warming and drought: reductions in primary productivity in the heat and drought year of 2003 journal December 2007
Beyond gradual warming: extreme weather events alter flower phenology of European grassland and heath species journal February 2009
Directional climate change and potential reversal of desertification in arid and semiarid ecosystems journal July 2011
Impacts of shrub encroachment on ecosystem structure and functioning: towards a global synthesis: Synthesizing shrub encroachment effects journal May 2011
Spectroscopy outperforms leaf trait relationships for predicting photosynthetic capacity across different forest types journal July 2021
Drivers of woody dominance across global drylands journal October 2024
Climate rather than overgrazing explains most rangeland primary productivity change in Mongolia journal September 2025
Evaluation of a decided sample size in machine learning applications journal February 2023
Extraction of fractional vegetation cover in arid desert area based on Chinese GF-6 satellite journal April 2021
Shrub Cover on the North Slope of Alaska: a circa 2000 Baseline Map journal August 2011
Variable Importance Plots—An Introduction to the vip Package journal January 2020
Toward Operational Mapping of Woody Canopy Cover in Tropical Savannas Using Google Earth Engine journal January 2020
Improved Mapping of Mountain Shrublands Using the Sentinel-2 Red-Edge Band journal November 2019
A Probability-Based Spectral Unmixing Analysis for Mapping Percentage Vegetation Cover of Arid and Semi-Arid Areas journal December 2019
Quantifying Western U.S. Rangelands as Fractional Components with Multi-Resolution Remote Sensing and In Situ Data journal January 2020
Effects of Training Set Size on Supervised Machine-Learning Land-Cover Classification of Large-Area High-Resolution Remotely Sensed Data journal January 2021
Mapping Shrub Coverage in Xilin Gol Grassland with Multi-Temporal Sentinel-2 Imagery journal July 2022
Deep-learning Versus OBIA for Scattered Shrub Detection with Google Earth Imagery: Ziziphus lotus as Case Study journal November 2017
Horizontal Positional Accuracy of Google Earth’s High-Resolution Imagery Archive journal December 2008
Finer-Resolution Mapping of Global Land Cover: Recent Developments, Consistency Analysis, and Prospects journal March 2021

Similar Records

Using high spatial resolution satellite imagery to map forest burn severity across spatial scales in a Pine Barrens ecosystem
Journal Article · Sat Jan 21 00:00:00 UTC 2017 · Remote Sensing of Environment · OSTI ID:1344231

Energetic considerations and habitat quality for elk in arid grasslands and coniferous forests
Journal Article · Mon Apr 01 04:00:00 UTC 1991 · Journal of Wildlife Management; (United States) · OSTI ID:5811909

BSSD 2019 Performance Metric Q2
Technical Report · Wed Mar 27 04:00:00 UTC 2019 · OSTI ID:1504630