scholarly journals Linking canopy reflectance to crop structure and photosynthesis to capture and interpret spatiotemporal dimensions of per-field photosynthetic productivity

2016 ◽  
Author(s):  
Wei Xue ◽  
Seungtaek Jeong ◽  
Jonghan Ko ◽  
John Tenhunen
Keyword(s):  
East Asian Monsoon ◽  
Canopy Structure ◽  
Growing Season ◽  
Nitrogen Addition ◽  
Time Shift ◽  
Drought Event ◽  
Canopy Reflectance ◽  
Asian Monsoon Region ◽  
Regional Patterns ◽  
Photosynthetic Productivity

Abstract. Nitrogen and water availability are two of staple environmental elements in agroecosystems that can substantially alter canopy structure and physiology then crop growth, yielding large impacts on ecosystem regulating/production provisions. However, to date, explicitly quantifying such impacts remains challenging partially due to lack of adequate methodology to capture spatial dimensions of ecosystem changes associated with nitrogen and water effects. A data assimilation, where close-range remote sensing measurements of vegetation indices derived from a hand-held instrument and an unmanned aerial vehicle (UAV) system are linked to leaf and canopy photosynthetic traits quantified at plot level by portable chamber systems, was applied to capture and interpret inter- and intra-field variations in gross primary productivity (GPP) in lowland rice grown under flooded condition (paddy rice, PD) subject to three available nutrient availability and under rainfed condition (RF) in East-Asian monsoon region, South Korea. Spatial variations (SVs) in both GPP and light use efficiency (LUEcabs) early in growing season were amplified by nitrogen addition, and such nutritional effects narrowed over time. Shift planting culture from flooded to rainfed conditions strengthened SVs in GPP and LUEcabs. Intervention of prolonged drought event at late growing season dramatically intensified their SVs that are supposed to seasonally decrease. Nevertheless, nitrogen addition effects on SV of LUEcabs at early growth stage made PD field exert greater SVs than RF field. SV of GPP across PD and RF rice were likely related to LAI development less to LUEcabs while, numerical analysis suggested that consider spatial variation and strength in LUEcabs for the same crop type tends to be vital for better evaluation in landscape/regional patterns of ecosystem photosynthetic productivity at critical phenology stages.

scholarly journals Linking canopy reflectance to crop structure and photosynthesis to capture and interpret spatiotemporal dimensions of per-field photosynthetic productivity

2017 ◽  
Vol 14 (5) ◽  
pp. 1315-1332 ◽  
Author(s):  
Wei Xue ◽  
Seungtaek Jeong ◽  
Jonghan Ko ◽  
John Tenhunen
Keyword(s):  
East Asian Monsoon ◽  
Canopy Structure ◽  
Growing Season ◽  
Nitrogen Addition ◽  
Canopy Reflectance ◽  
Asian Monsoon Region ◽  
Regional Patterns ◽  
Area Index ◽  
Photosynthetic Productivity ◽  
Rainfed Conditions

Abstract. Nitrogen and water availability alter canopy structure and physiology, and thus crop growth, yielding large impacts on ecosystem-regulating/production provisions. However, to date, explicitly quantifying such impacts remains challenging partially due to lack of adequate methodology to capture spatial dimensions of ecosystem changes associated with nitrogen and water effects. A data fitting, where close-range remote-sensing measurements of vegetation indices derived from a handheld instrument and an unmanned aerial vehicle (UAV) system are linked to in situ leaf and canopy photosynthetic traits, was applied to capture and interpret inter- and intra-field variations in gross primary productivity (GPP) in lowland rice grown under flooded conditions (paddy rice, PD) subject to three nitrogen application rates and under rainfed conditions (RF) in an East Asian monsoon region of South Korea. Spatial variations (SVs) in both GPP and light use efficiency (LUEcabs) early in the growing season were enlarged by nitrogen addition. The nutritional effects narrowed over time. A shift in planting culture from flooded to rainfed conditions strengthened SVs in GPP and LUEcabs. Intervention of prolonged drought late in the growing season dramatically intensified SVs that were supposed to seasonally decrease. Nevertheless, nitrogen addition effects on SV of LUEcabs at the early growth stage made PD fields exert greater SVs than RF fields. SVs of GPP across PD and RF rice fields were likely related to leaf area index (LAI) development less than to LUEcabs, while numerical analysis suggested that considering strength in LUEcabs and its spatial variation for the same crop type tends to be vital for better evaluation in landscape/regional patterns of ecosystem photosynthetic productivity at critical phenology stages.

scholarly journals Plant ecophysiological processes in spectral profiles: perspective from a deciduous broadleaf forest

2021 ◽  
Author(s):  
Hibiki M. Noda ◽  
Hiroyuki Muraoka ◽  
Kenlo Nishida Nasahara
Keyword(s):  
Remote Sensing ◽  
Optical Properties ◽  
Spectral Reflectance ◽  
Canopy Structure ◽  
Terrestrial Ecosystems ◽  
Optical Remote Sensing ◽  
Canopy Reflectance ◽  
Broadleaf Forest ◽  
Leaf Optical Properties ◽  
Deciduous Broadleaf Forest

AbstractThe need for progress in satellite remote sensing of terrestrial ecosystems is intensifying under climate change. Further progress in Earth observations of photosynthetic activity and primary production from local to global scales is fundamental to the analysis of the current status and changes in the photosynthetic productivity of terrestrial ecosystems. In this paper, we review plant ecophysiological processes affecting optical properties of the forest canopy which can be measured with optical remote sensing by Earth-observation satellites. Spectral reflectance measured by optical remote sensing is utilized to estimate the temporal and spatial variations in the canopy structure and primary productivity. Optical information reflects the physical characteristics of the targeted vegetation; to use this information efficiently, mechanistic understanding of the basic consequences of plant ecophysiological and optical properties is essential over broad scales, from single leaf to canopy and landscape. In theory, canopy spectral reflectance is regulated by leaf optical properties (reflectance and transmittance spectra) and canopy structure (geometrical distributions of leaf area and angle). In a deciduous broadleaf forest, our measurements and modeling analysis of leaf-level characteristics showed that seasonal changes in chlorophyll content and mesophyll structure of deciduous tree species lead to a seasonal change in leaf optical properties. The canopy reflectance spectrum of the deciduous forest also changes with season. In particular, canopy reflectance in the green region showed a unique pattern in the early growing season: green reflectance increased rapidly after leaf emergence and decreased rapidly after canopy closure. Our model simulation showed that the seasonal change in the leaf optical properties and leaf area index caused this pattern. Based on this understanding we discuss how we can gain ecophysiological information from satellite images at the landscape level. Finally, we discuss the challenges and opportunities of ecophysiological remote sensing by satellites.

Nitrogen addition amplifies the nonlinear drought response of grassland productivity to extended growing‐season droughts

Ecology ◽  
2021 ◽  
Author(s):  
Bo Meng ◽  
Junqin Li ◽  
Gregory E. Maurer ◽  
Shangzhi Zhong ◽  
Yuan Yao ◽  
...  
Keyword(s):  
Growing Season ◽  
Nitrogen Addition ◽  
Drought Response ◽  
Grassland Productivity

Responses of growing‐season soil respiration to water and nitrogen addition as affected by grazing intensity

2018 ◽  
Vol 32 (7) ◽  
pp. 1890-1901 ◽  
Author(s):  
Jianjun Li ◽  
Yin Huang ◽  
Fengwei Xu ◽  
Liji Wu ◽  
Dima Chen ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Grazing Intensity ◽  
Growing Season ◽  
Nitrogen Addition

scholarly journals Ocean Salinity as a Precursor of Summer Rainfall over the East Asian Monsoon Region

2019 ◽  
Vol 32 (17) ◽  
pp. 5659-5676 ◽  
Author(s):  
Biao Chen ◽  
Huiling Qin ◽  
Guixing Chen ◽  
Huijie Xue
Keyword(s):  
Water Vapor ◽  
Asian Monsoon ◽  
East Asian Monsoon ◽  
Summer Rainfall ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
Asian Monsoon Region ◽  
Water Vapor Flux ◽  
Vapor Flux ◽  
Land Water

Abstract The sea surface salinity (SSS) varies largely as a result of the evaporation–precipitation difference, indicating the source or sink of regional/global water vapor. This study identifies a relationship between the spring SSS in the tropical northwest Pacific (TNWP) and the summer rainfall of the East Asian monsoon region (EAMR) during 1980–2017. Analysis suggests that the SSS–rainfall link involves the coupled ocean–atmosphere–land processes with a multifacet evolution. In spring, evaporation and water vapor flux divergence were enhanced in some years over the TNWP where an anomalous atmospheric anticyclone was established and a high SSS was well observed. As a result, the convergence of water vapor flux and soil moisture over the EAMR was strengthened. This ocean-to-land water vapor transport pattern was sustained from spring to summer and played a leading role in the EAMR rainfall. Moreover, the change in local spring soil moisture helped to amplify the summer rainfall by modifying surface thermal conditions and precipitation systems over the EAMR. As the multifacet evolution is closely related to the large-scale ocean-to-land water vapor transport, it can be well represented by the spring SSS in the TNWP. A random forest regression algorithm was used to further evaluate the relative importance of spring SSS in predicting summer rainfall compared to other climate indices. As the SSS is now monitored routinely by satellite and the global Argo float array, it can serve as a good metric for measuring the water cycle and as a precursor for predicting the EAMR rainfall.

scholarly journals Estimation of Gross Primary Productivity (GPP) Phenology of a Short-Rotation Plantation Using Remotely Sensed Indices Derived from Sentinel-2 Images

2020 ◽  
Vol 12 (13) ◽  
pp. 2104
Author(s):  
Maral Maleki ◽  
Nicola Arriga ◽  
José Miguel Barrios ◽  
Sebastian Wieneke ◽  
Qiang Liu ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Seasonal Pattern ◽  
Vegetation Indices ◽  
Canopy Structure ◽  
Growing Season ◽  
Gross Primary Productivity ◽  
Imaging Spectrometer ◽  
Short Rotation ◽  
Medium Resolution ◽  
Sentinel 2

This study aimed to understand which vegetation indices (VIs) are an ideal proxy for describing phenology and interannual variability of Gross Primary Productivity (GPP) in short-rotation coppice (SRC) plantations. Canopy structure- and chlorophyll-sensitive VIs derived from Sentinel-2 images were used to estimate the start and end of the growing season (SOS and EOS, respectively) during the period 2016–2018, for an SRC poplar (Populus spp.) plantation in Lochristi (Belgium). Three different filtering methods (Savitzky–Golay (SavGol), polynomial (Polyfit) and Harmonic Analysis of Time Series (HANTS)) and five SOS- and EOS threshold methods (first derivative function, 10% and 20% percentages and 10% and 20% percentiles) were applied to identify the optimal methods for the determination of phenophases. Our results showed that the MEdium Resolution Imaging Spectrometer (MERIS) Terrestrial Chlorophyll Index (MTCI) had the best fit with GPP phenology, as derived from eddy covariance measurements, in identifying SOS- and EOS-dates. For SOS, the performance was only slightly better than for several other indices, whereas for EOS, MTCI performed markedly better. The relationship between SOS/EOS derived from GPP and VIs varied interannually. MTCI described best the seasonal pattern of the SRC plantation’s GPP (R2 = 0.52 when combining all three years). However, during the extreme dry year 2018, the Chlorophyll Red Edge Index performed slightly better in reproducing growing season GPP variability than MTCI (R2 = 0.59; R2 = 0.49, respectively). Regarding smoothing functions, Polyfit and HANTS methods showed the best (and very similar) performances. We further found that defining SOS as the date at which the 10% or 20% percentile occurred, yielded the best agreement between the VIs and the GPP; while for EOS the dates of the 10% percentile threshold came out as the best.

scholarly journals Effects of rainfall manipulation and nitrogen addition on plant biomass allocation in a semiarid sandy grassland

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Jing Zhang ◽  
Xiaoan Zuo ◽  
Xueyong Zhao ◽  
Jianxia Ma ◽  
Eduardo Medina-Roldán
Keyword(s):  
Biomass Allocation ◽  
Plant Biomass ◽  
Extreme Rainfall ◽  
Growing Season ◽  
Nitrogen Addition ◽  
Extreme Drought ◽  
N Addition ◽  
Rainfall Distribution ◽  
Grassland Plants ◽  
Sandy Grassland

Abstract Extreme climate events and nitrogen (N) deposition are increasingly affecting the structure and function of terrestrial ecosystems. However, the response of plant biomass to variations to these global change drivers is still unclear in semi-arid regions, especially in degraded sandy grasslands. In this study, a manipulative field experiment run over two years (from 2017 to 2018) was conducted to examine the effect of rainfall alteration and nitrogen addition on biomass allocation of annuals and perennial plants in Horqin sandy grassland, Northern China. Our experiment simulated extreme rainfall and extreme drought (a 60% reduction or increment in the growing season rainfall with respect to a control background) and N addition (20 g/m2) during the growing seasons. We found that the sufficient rainfall during late July and August compensates for biomass losses caused by insufficient water in May and June. When rainfall distribution is relatively uniform during the growing season, extreme rainfall increased aboveground biomass (AGB) and belowground biomass (BGB) of annuals, while extreme drought reduced AGB and BGB of perennials. Rainfall alteration had no significant impacts on the root-shoot ratio (R/S) of sandy grassland plants, while N addition reduced R/S of grassland species when there was sufficient rainfall in the early growing season. The biomass of annuals was more sensitive to rainfall alteration and nitrogen addition than the biomass of perennials. Our findings emphasize the importance of monthly rainfall distribution patterns during the growing season, which not only directly affect the growth and development of grassland plants, but also affect the nitrogen availability of grassland plants.

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