Impact of physiological and phenological change on carbon uptake on the Tibetan Plateau revealed through GPP estimation based on spaceborne solar-induced fluorescence.

Although gross primary production (GPP) is an essential proxy for reflecting terrestrial ecosystem function, GPP estimation at regional scale on the Tibetan Plateau (TP) is constrained by the lack of ground observations. Moreover, how climate-induced phenological and physiological change further affects carbon uptake in this region remains unclear. In this study, we first estimated GPP at 8-day intervals and a 0.5° resolution from 2007 to 2015 over the TP based on an improved approach and GOME-2 sun-induced fluorescence (SIF) retrievals. The obtained SIF-based GPP coincided well with flux observations and two state of the art GPP products, with a regional carbon uptake of 0.62 ± 0.04 PgC year-1 or 307 ± 22 gC m-2 year-1. With the SIF-based GPP, two phenological indicators (start and end date of the growing season, i.e., SGS and EGS) and one physiological indicator (maximum photosynthesis capacity, GPPmax) were identified and their relative contributions to inter-annual GPP variability were further quantitatively separated using a multiple regression model. Advanced SGS, delayed EGS, and increasing GPPmax can all enhance carbon uptake and a combination of the three indicators can explain 72 ± 20% of GPP inter-annual variability. The response of annual GPP to phenological and physiological variations has significant altitude dependence, as the decline of annual GPP in most of the area is dominated by the GPPmax decline, while the increase of annual GPP in the high-altitude area is dominated by the advanced SGS. The response of all three indicators to both temperature and precipitation variation has great spatial heterogeneity. Our study suggests that remote sensing of SIF can provide a unique opportunity to estimate GPP in regions with a lack of ground observations and that our enhanced understanding of the impact of the climate-induced phenological and physiological change on GPP variability in alpine ecosystems can improve GPP estimation in a changing climate.

[1]  Michael F. Hutchinson,et al.  Interpolation of Rainfall Data with Thin Plate Smoothing Splines - Part I: Two Dimensional Smoothing of Data with Short Range Correlation , 1998 .

[2]  D. Hollinger,et al.  Influence of spring phenology on seasonal and annual carbon balance in two contrasting New England forests. , 2009, Tree physiology.

[3]  Yanhong Tang,et al.  Calibration of Terra/MODIS gross primary production over an irrigated cropland on the North China Plain and an alpine meadow on the Tibetan Plateau , 2008 .

[4]  A. Huete,et al.  Estimation of vegetation photosynthetic capacity from space‐based measurements of chlorophyll fluorescence for terrestrial biosphere models , 2014, Global change biology.

[5]  C. Frankenberg,et al.  Global monitoring of terrestrial chlorophyll fluorescence from moderate-spectral-resolution near-infrared satellite measurements: methodology, simulations, and application to GOME-2 , 2013 .

[6]  Liqiang Ji,et al.  Carbon dynamics of terrestrial ecosystems on the Tibetan Plateau during the 20th century: an analysis with a process-based biogeochemical model , 2010 .

[7]  Guirui Yu,et al.  Diurnal, seasonal and annual variation in net ecosystem CO2 exchange of an alpine shrubland on Qinghai‐Tibetan plateau , 2006 .

[8]  Wei Sun,et al.  A Meta-analysis of the Effects of Experimental Warming on Plant Physiology and Growth on the Tibetan Plateau , 2014, Journal of Plant Growth Regulation.

[9]  Martha C. Anderson,et al.  The shared and unique values of optical, fluorescence, thermal and microwave satellite data for estimating large-scale crop yields. , 2016 .

[10]  Hideki Kobayashi,et al.  Integration of MODIS land and atmosphere products with a coupled‐process model to estimate gross primary productivity and evapotranspiration from 1 km to global scales , 2011 .

[11]  Stefano Schiavon,et al.  Climate Change 2007: The Physical Science Basis. , 2007 .

[12]  P. Ciais,et al.  Influence of spring and autumn phenological transitions on forest ecosystem productivity , 2010, Philosophical Transactions of the Royal Society B: Biological Sciences.

[13]  Yanhong Tang,et al.  Altitude and temperature dependence of change in the spring vegetation green-up date from 1982 to 2006 in the Qinghai-Xizang Plateau , 2011 .

[14]  M. S. Moran,et al.  Global and time-resolved monitoring of crop photosynthesis with chlorophyll fluorescence , 2014, Proceedings of the National Academy of Sciences.

[15]  Liangfu Chen,et al.  Vegetation net primary productivity and its response to climate change during 2001-2008 in the Tibetan Plateau. , 2013, The Science of the total environment.

[16]  P. Blanken,et al.  Joint control of terrestrial gross primary productivity by plant phenology and physiology , 2015, Proceedings of the National Academy of Sciences.

[17]  R. B. Jackson,et al.  A Large and Persistent Carbon Sink in the World’s Forests , 2011, Science.

[18]  John L. Innes,et al.  Spatial and temporal variations in the end date of the vegetation growing season throughout the Qinghai-Tibetan Plateau from 1982 to 2011 , 2014 .

[19]  Eike Luedeling,et al.  Winter and spring warming result in delayed spring phenology on the Tibetan Plateau , 2010, Proceedings of the National Academy of Sciences.

[20]  Miaogen Shen,et al.  Spring phenology was not consistently related to winter warming on the Tibetan Plateau , 2011, Proceedings of the National Academy of Sciences.

[21]  Shilong Piao,et al.  Spatial variations in responses of vegetation autumn phenology to climate change on the Tibetan Plateau , 2016 .

[22]  P. Ciais,et al.  Variations in satellite‐derived phenology in China's temperate vegetation , 2006 .

[23]  Xinquan Zhao,et al.  Seasonal and inter-annual variations in CO2 fluxes over 10 years in an alpine shrubland on the Qinghai-Tibetan Plateau, China , 2016 .

[24]  Qifeng Lu,et al.  Hydrological Response of Alpine Wetlands to Climate Warming in the Eastern Tibetan Plateau , 2016, Remote. Sens..

[25]  F. Woodward,et al.  Terrestrial Gross Carbon Dioxide Uptake: Global Distribution and Covariation with Climate , 2010, Science.

[26]  Jing M. Chen,et al.  Angular normalization of GOME‐2 Sun‐induced chlorophyll fluorescence observation as a better proxy of vegetation productivity , 2017 .

[27]  J. B. Miller,et al.  Increase in observed net carbon dioxide uptake by land and oceans during the past 50 years , 2012, Nature.

[28]  J. Zeng,et al.  Evaluation of remotely sensed and reanalysis soil moisture products over the Tibetan Plateau using in-situ observations , 2015 .

[29]  Jinwei Dong,et al.  Green-up dates in the Tibetan Plateau have continuously advanced from 1982 to 2011 , 2013, Proceedings of the National Academy of Sciences.

[30]  C. Körner.  The use of 'altitude' in ecological research. , 2007, Trends in ecology & evolution.

[31]  M. Shen,et al.  Strong impacts of daily minimum temperature on the green‐up date and summer greenness of the Tibetan Plateau , 2016, Global change biology.

[32]  Yun Chen,et al.  Estimating effects of plantation expansion and climate variability on streamflow for catchments in Australia , 2011 .

[33]  Philippe Ciais,et al.  The carbon balance of terrestrial ecosystems in China , 2009, Nature.

[34]  L. Guanter,et al.  Consistency Between Sun-Induced Chlorophyll Fluorescence and Gross Primary Production of Vegetation in North America , 2016 .

[35]  Philippe Ciais,et al.  Dominant role of plant physiology in trend and variability of gross primary productivity in North America , 2017, Scientific Reports.

[36]  Alan H. Strahler,et al.  Global land cover mapping from MODIS: algorithms and early results , 2002 .

[37]  V. Singh,et al.  Vegetation phenology on the Qinghai-Tibetan Plateau and its response to climate change (1982-2013) , 2018 .

[38]  C. Frankenberg,et al.  Forest productivity and water stress in Amazonia: observations from GOSAT chlorophyll fluorescence , 2013, Proceedings of the Royal Society B: Biological Sciences.

[39]  I. Wing,et al.  Net carbon uptake has increased through warming-induced changes in temperate forest phenology , 2014 .

[40]  C. Miao,et al.  Spatiotemporal Changes in Extreme Temperature and Precipitation Events in the Three‐Rivers Headwater Region, China , 2018, Journal of Geophysical Research: Atmospheres.

[41]  Olivier Boucher,et al.  Projected increase in continental runoff due to plant responses to increasing carbon dioxide , 2007, Nature.

[42]  Hong Jiang,et al.  The impacts of climate change and human activities on biogeochemical cycles on the Qinghai‐Tibetan Plateau , 2013, Global change biology.

[43]  M. Schaepman,et al.  Intercomparison, interpretation, and assessment of spring phenology in North America estimated from remote sensing for 1982–2006 , 2009 .

[44]  Corinne Le Quéré,et al.  Climate Change 2013: The Physical Science Basis , 2013 .

[45]  Zhenchun Hao,et al.  Hydrological projections of future climate change over the source region of Yellow River and Yangtze River in the Tibetan Plateau: A comprehensive assessment by coupling RegCM4 and VIC model , 2018, Hydrological Processes.

[46]  Yanhong Tang,et al.  Influences of temperature and precipitation before the growing season on spring phenology in grasslands of the central and eastern Qinghai-Tibetan Plateau , 2011 .

[47]  Yanhong Tang,et al.  Temperature and biomass influences on interannual changes in CO2 exchange in an alpine meadow on the Qinghai‐Tibetan Plateau , 2006 .

[48]  Xiangming Xiao,et al.  Modeling gross primary production of alpine ecosystems in the Tibetan Plateau using MODIS images and climate data , 2007 .

[49]  Kelly K. Caylor,et al.  Explaining inter-annual variability of gross primary productivity from plant phenology and physiology , 2016 .

[50]  Bing Zhang,et al.  Responses of net primary productivity to phenological dynamics in the Tibetan Plateau, China , 2017 .

[51]  Tao Wang,et al.  Plant phenological responses to climate change on the Tibetan Plateau: research status and challenges , 2015 .

[52]  E. Vaganov,et al.  New perspective on spring vegetation phenology and global climate change based on Tibetan Plateau tree-ring data , 2017, Proceedings of the National Academy of Sciences.

[53]  A. Arneth,et al.  Global patterns of land-atmosphere fluxes of carbon dioxide, latent heat, and sensible heat derived from eddy covariance, satellite, and meteorological observations , 2011 .

[54]  S. Running,et al.  Global Terrestrial Gross and Net Primary Productivity from the Earth Observing System , 2000 .

[55]  Sari Palmroth,et al.  Leaf stomatal responses to vapour pressure deficit under current and CO(2)-enriched atmosphere explained by the economics of gas exchange. , 2008, Plant, cell & environment.

[56]  J. Tao,et al.  The impact of climate change and anthropogenic activities on alpine grassland over the Qinghai-Tibet Plateau , 2014 .

[57]  C. Tucker,et al.  Climate-Driven Increases in Global Terrestrial Net Primary Production from 1982 to 1999 , 2003, Science.

[58]  Wenquan Zhu,et al.  Continuous but diverse advancement of spring-summer phenology in response to climate warming across the Qinghai-Tibetan Plateau , 2016 .

[59]  D. Lobell,et al.  Improving the monitoring of crop productivity using spaceborne solar‐induced fluorescence , 2016, Global change biology.

[60]  S. Piao,et al.  Spring vegetation green-up date in China inferred from SPOT NDVI data: A multiple model analysis , 2012 .

[61]  Youngryel Ryu,et al.  Multi-scale evaluation of global gross primary productivity and evapotranspiration products derived from Breathing Earth System Simulator (BESS) , 2016 .

[62]  James S. Clark,et al.  Effects of climate and atmospheric CO2 partial pressure on the global distribution of C4 grasses: present, past, and future , 1998, Oecologia.

[63]  Yanhong Tang,et al.  Carbon dioxide exchange between the atmosphere and an alpine meadow ecosystem on the Qinghai–Tibetan Plateau, China , 2004 .

[64]  Guirui Yu,et al.  A MODIS-based Photosynthetic Capacity Model to estimate gross primary production in Northern China and the Tibetan Plateau , 2014 .

[65]  C. Frankenberg,et al.  OCO-2 advances photosynthesis observation from space via solar-induced chlorophyll fluorescence , 2017, Science.

[66]  L. Guanter,et al.  The seasonal cycle of satellite chlorophyll fluorescence observations and its relationship to vegetation phenology and ecosystem atmosphere carbon exchange , 2014 .

[67]  Michael F. Hutchinson,et al.  Interpolation of Rainfall Data with Thin Plate Smoothing Splines - Part II: Analysis of Topographic Dependence , 2002 .

[68]  J. Monteith.  SOLAR RADIATION AND PRODUCTIVITY IN TROPICAL ECOSYSTEMS , 1972 .