Abstract
Field net primary productivity (NPP) is useful in research modeling of regional and global carbon cycles and for validating results by remote sensing or process-based models. In this study, we used multiple models of NPP estimation and vegetation classification methods to study Chinese vegetation NPP characteristics, trends, and drivers using 7618 field measurements from the 1960s, 1980s, and 2000s. The values of other relevant NPP models, as well as process-based simulation and remote sensing models, were compared. Our results showed that NPP ranged from 3 to 12,407 gC·m−2·year−1 with a mean value of 571 gC·m−2·year−1. Vegetation NPP gradually decreased from the southeast to the northwest. Forest, farmland, and grassland NPP was 1152, 294, and 518 gC·m−2·year−1, respectively. Total NPP of grassland was higher than that of farmland. Total terrestrial NPP decreased from 3.58 to 3.41 Pg C·year−1 from the 1960s to the 2000s, a decadal decrease of 4.7%. Total NPP in forests and grasslands consistently showed a decreasing trend and decreased by 0.46 Pg C·year−1and 0.16 Pg C·year−1, respectively, whereas NPP for farmland showed an opposite trend, with a growth of 0.45 Pg C·year−1. Our research findings filled gaps in the information regarding NPP for the entire landmass of China based on field data from a long-term time series and provide valuable information and a basis for validation analyses by remote sensing models, as well as a robust quantification of carbon estimation to anticipate future development at the national and global scale.
Highlights
Net primary production (NPP) is the amount of organic matter produced by photosynthesis per unit of time and area, minus autotrophic respiration of vegetation [1,2,3]
net primary productivity (NPP) at the site level can be acquired by field measurements, such as the aboveground biomass (AGB) and belowground biomass (BGB) in grasslands
The higher decline of NPP was mainly distributed in the northern part of Southwest China, along the Yangtze River Middle Plains (YR) with a decrease above 60%, followed by the northern part of Inner Mongolia, the Changbai mountain forest area in Northeastern China, and the Eastern Liaoning Plain, with a decline below 20%
Summary
Net primary production (NPP) is the amount of organic matter produced by photosynthesis per unit of time and area, minus autotrophic respiration of vegetation [1,2,3]. With the rapid development of remote sensing and GIS technology, numerous studies at regional and global scales have been conducted concerning the method of rapidly estimating NPP using moderate-resolution satellite Normalized Difference Vegetation Index (NDVI) datasets (e.g., the Advanced Very High Resolution Radiometer (AVHRR) data and the Moderate. Resolution Imaging Spectroradiometer (MODIS) data) [9,10,11,12,13,14,15,16,17,18] into an estimation model, such as the Carnegie-Ames-Stanford-Approach (CASA) model [19,20,21], the Global Production Efficiency Model (GLO-PEM) [22,23], or the Eddy Covariance-Light Use Efficiency (EC-LUE) model [24], the Atmosphere-Vegetation Interaction Model (AVIM2) [25,26], or spatial interpolation [27,28]. The remote sensing images can provide continuous, dynamic, and comprehensive land-surface information for any region on Earth [29,30]
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