TY - JOUR
T1 - Dense canopies browning overshadowed by global greening dominant in sparse canopies
AU - Qiu, Bingwen
AU - Ye, Zhiyan
AU - Chen, Chongcheng
AU - Tang, Zhenghong
AU - Chen, Zuoqi
AU - Huang, Hongyu
AU - Zhao, Zhiyuan
AU - Xu, Weiming
AU - Berry, Joe
N1 - Publisher Copyright:
© 2022 Elsevier B.V.
PY - 2022/6/20
Y1 - 2022/6/20
N2 - Greening, an increase in photosynthetically active plant biomass, has been widely reported as period-related and region-specific. We hypothesized that vegetation trends were highly density-dependent with intensified browning in dense canopies and increased greening in sparse canopies. We exploited this insight by estimating vegetation trends in peak growth from dense to sparse canopies graded from 1 to 20 using the non-parametric Mann-Kendall trend test based on the 500 m 8-day composite MODIS Near Infrared Reflectance of terrestrial vegetation (NIRv) time series datasets in the past two decades (2001–2019) at the global scale. We found that global greening increased by 1.42% per grade with strong fit before grade 15 (R2 = 0.95): net browning (11% browning vs 9% greening) exhibited in high-density canopies (NIRv > 0.39) in contrast to 32% greening in low-density canopies (NIRv ≈ 0.15). While the density-dependent greening was evidenced across different biomes and ecosystems, the steepest gradient (changes per grade) in cropland highlighted the increasingly intensified agricultural activities globally. Greening gradients declined in the dryland, but enhanced in the High-latitude ecosystems driven by warming, especially in the shrubland. Density-dependent vegetation trends were accounted for by the disproportionately impacts from climate changes and the unequal contributions of Land Cover Changes (LCC) among dense and sparse canopies. Vegetation trends and greening gradients could be extensively facilitated by Wetting or Decreasing solar Radiation (WDR), especially in sparse grassland and shrubland. Browning was dominant in dense canopies, which was further aggravated by Drying and Increasing solar Radiation (DIR), especially woody vegetation. This study implied the widespread degradation or mortality of highly productive vegetation hidden among global greening dominant in open ecosystems, which might be further exacerbated by the predicted increasing drought under global warming.
AB - Greening, an increase in photosynthetically active plant biomass, has been widely reported as period-related and region-specific. We hypothesized that vegetation trends were highly density-dependent with intensified browning in dense canopies and increased greening in sparse canopies. We exploited this insight by estimating vegetation trends in peak growth from dense to sparse canopies graded from 1 to 20 using the non-parametric Mann-Kendall trend test based on the 500 m 8-day composite MODIS Near Infrared Reflectance of terrestrial vegetation (NIRv) time series datasets in the past two decades (2001–2019) at the global scale. We found that global greening increased by 1.42% per grade with strong fit before grade 15 (R2 = 0.95): net browning (11% browning vs 9% greening) exhibited in high-density canopies (NIRv > 0.39) in contrast to 32% greening in low-density canopies (NIRv ≈ 0.15). While the density-dependent greening was evidenced across different biomes and ecosystems, the steepest gradient (changes per grade) in cropland highlighted the increasingly intensified agricultural activities globally. Greening gradients declined in the dryland, but enhanced in the High-latitude ecosystems driven by warming, especially in the shrubland. Density-dependent vegetation trends were accounted for by the disproportionately impacts from climate changes and the unequal contributions of Land Cover Changes (LCC) among dense and sparse canopies. Vegetation trends and greening gradients could be extensively facilitated by Wetting or Decreasing solar Radiation (WDR), especially in sparse grassland and shrubland. Browning was dominant in dense canopies, which was further aggravated by Drying and Increasing solar Radiation (DIR), especially woody vegetation. This study implied the widespread degradation or mortality of highly productive vegetation hidden among global greening dominant in open ecosystems, which might be further exacerbated by the predicted increasing drought under global warming.
KW - Climatic changes
KW - Density-dependent
KW - Global greening
KW - Peak growth of vegetation
KW - Spatial heterogeneity
KW - Time series images
UR - http://www.scopus.com/inward/record.url?scp=85126805967&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85126805967&partnerID=8YFLogxK
U2 - 10.1016/j.scitotenv.2022.154222
DO - 10.1016/j.scitotenv.2022.154222
M3 - Article
C2 - 35240174
AN - SCOPUS:85126805967
SN - 0048-9697
VL - 826
JO - Science of the Total Environment
JF - Science of the Total Environment
M1 - 154222
ER -