Effects of Ozone Pollution and Climate Variability/Change on Spatial and Temporal Patterns of Terrestrial Primary Productivity and Carbon Storage in China

Abstract

Over the past several decades, China’s terrestrial ecosystems have experienced severe air pollution and other environmental changes. Quantifying how these environmental changes have affected carbon (C) fluxes and storage in China’s terrestrial ecosystems is crucial to understanding the global C cycle as well as China’s sustainability. Using an improved Dynamic Land Ecosystem Model (DLEM), I assessed the spatial and temporal patterns of net primary productivity (NPP) and C storage in China’s terrestrial ecosystems in response to tropospheric ozone (O3) pollution and historical climate variability/ change in the context of multi-factor global change during 1961-2005. An overall evaluation has been implemented to investigate how elevated O3 in combination with climate variability has affected the C cycle in terrestrial ecosystems of the nation. The modeled results showed that during 1961-2005, elevated O3 resulted in a mean 4.5% loss in NPP and a 0.9% reduction in total C storage for China’s terrestrial ecosystems as a whole, which has reduced the magnitude of terrestrial C sink during the same period. The reduction of C storage among different terrestrial ecosystems varied from 0.1 Tg C to 312 Tg C (1 T = 1012) with a decreasing rate ranging from 0.2% to 6.9%. For example, China’s grassland ecosystems, distributed mainly in arid and semi-arid regions of North China, were the most vulnerable in response to climate variability/ change and elevated O3. The effect of O3 pollution on China’s forest ecosystems could be accelerated by climate extreme events such as drought. For agricultural ecosystems, some rain-fed cropland areas in arid and semi-arid regions of North China, which experienced high O3 levels and frequent drought events, acted as a C source. However the effect of O3 pollution and climate variability/change on C storage in cropland could be modified by land management (e.g. irrigation and fertilizer). Results from this study indicate that improved air quality could significantly increase productivity and C storage in China’s terrestrial ecosystems and that optimized land management options could enhance the adaptation of terrestrial ecosystem to climate variability/change and air pollution.