Photosynthetic trends in India derived from remote sensing measurements during 2000–2019: vegetation dynamics and key climate drivers

Abstract

Significant changes in the photosynthesis of terrestrial vegetation are observed in recent decades due to climate variability, land use and land cover changes, frequent disasters and anthropogenic forcing, but this situation in the Indian context remains largely unexplored. Here, therefore, we estimate the long–term changes in photosynthesis and its key climate drivers in India. The gross photosynthetic activity peaks (FPAR _mean = 0.57) in post–monsoon (September, October and November) due to high soil moisture (87.26 kg/m²), good precipitation (5.2 mm/day) and optimum temperature (21.46 °C) conditions, whereas it is smallest (FPAR _mean = 0.4) in summer (March, April and May) due to very high temperature (27.37 °C) and lower soil moisture (55.45 kg/m²). The trend in FPAR over 2000–2019 reveals enhanced photosynthetic activity in India. In the northwest, both soil moisture and temperature have a positive influence on greening (i.e. moisture induced greening). Conversely, the unfavourable soil moisture and temperature conditions dominate in the peninsular region to trigger browning there (i.e. warming induced moisture stress). Our analyses suggest that the photosynthetic trend is primarily controlled by trend in the soil moisture (44.31%) and air temperature (32.54%). The warming induced moisture stress can be a serious threat in the future to drive browning in more areas. Extreme events such as droughts, landslides and fires are expected to increase in the hilly regions such as the northeast due to browning. Furthermore, as food production and forest resources influence the economy of a country like India, management and conservation of greenery are inevitable for a sustainable ecosystem.

Keywords:

• FPAR
• photosynthetic trend
• soil moisture
• climate drivers
• climate variability

Acknowledgements

We thank the Director, Indian Institute of Technology Kharagpur (IIT Kgp), Head of CORAL IIT Kgp and the Ministry of Education (MoE) for facilitating the study. RK acknowledges the support from MoE, IIT KGP and DGI, SNRM, CUJ. We thank the NASA’s LPDAAC team for providing the MODIS landcover and NDVI products. Giovanni's online data system developed and maintained by the NASA GES DISC for providing the GPM level–3 precipitation data, GLDAS for providing temperature and soil moisture content datasets. CDSP, NDC, IMD, MoES for providing IMD based precipitation and temperature data sets. We thank the anonymous reviewers and the Editor for their insightful and critical comments that helped in improving the quality of the study.

Disclosure statement

The authors declare that they have no known competing interest.

Data availability

MODIS Landcover product is available at: https://lpdaacsvc.cr.usgs.gov/

MODIS NDVI product is available at: https://lpdaacsvc.cr.usgs.gov/

GPM Level–3 Precipitation data is available at: https://giovanni.gsfc.nasa.gov/giovanni/

GLDAS Temperature data is available at: https://giovanni.gsfc.nasa.gov/giovanni/

GLDAS Soil Moisture data is available at: https://giovanni.gsfc.nasa.gov/giovanni/

IMD Precipitation and temperature data is available at: https://www.imdpune.gov.in/index.html