A novel remote sensing-based method of ozone damage assessment effect on Net Primary Productivity of various vegetation types

摘要

Tropospheric ozone causes considerable damage to both agricultural crops and forest trees, leading to Net Primary Productivity (NPP) reduction. Ozone damage is conventionally investigated using experiments limited in scope and study area. This study attempted to develop a novel remote sensing-based method to assess the effect of regional ozone damage on the NPP of various vegetation types, combining AOT40 (Accumulated Ozone exposure over a Threshold of 40 ppb) and MODIS NPP products. Annual averages of multi-year (five periods during 2009-2013) cumulative AOT40 values and NPP data for each MODIS image pixel were compared to investigate the relationships between NPP and AOT40, and construct linear AOT40-based NPP response models for each of five vegetation types. Our results showed negative significant relationships between NPP and AOT40 for all vegetation types, using at least 4-year average AOT40 values. Estimated maps of ozone impacts on NPP showed a 4-48% reduction for the Kanto area of Japan in response to AOT40 for the year 2013, and a higher ozone sensitivity of crop species (with NPP decrease of 12-48%) than forest species (with NPP decrease of 4-39%). The largest decreases (over 40% in some locations) occurred in the agricultural lands in the central part of the study area. This remote sensing-based method was considered as suitable for regional ozone damage assessment with considerable precision based on comparison with the results of previous experiment-based studies.