Seasonal Photosynthesis and Carbon Assimilation of Dynamics in a Zelkova serrata (Thunb.) Makino Plantation

Chung-I Chen,Ching-Wen Wang,Ya-Nan Wang,Yung-Chih Chen,Heng-Hsun Lin,Jui-Chu Yu

doi:10.3390/f12040467

Abstract

As anthropogenic greenhouse gas emissions intensify global climate change, plantations have become an important tool to mitigate atmospheric CO2. Our aim in this study was to estimate carbon assimilation and clarify the impact of environmental factors on the photosynthesis of Zelkova serrata (Thunb.) Makino, an important plantation species that is extensively planted in low altitude regions of East Asia. We measured monthly gas exchange parameters and leaf area index to estimate carbon assimilation. The results showed that gas exchange was significantly affected by vapor pressure deficit and temperature, especially in the dry season, and both photosynthetic rate and carbon assimilation decreased. Lower daytime assimilation and higher nighttime respiration during the dry season, which caused a 43% decrease in carbon assimilation in Z. serrata plantations. Z. serrata exhibited lower photosynthetic rate and lower carbon assimilation following planting in a tropical monsoon climate area. Therefore, the effects of extreme weather such as high temperature and vapor pressure deficit on Z. serrata forest carbon budget could be stronger in the future. Leaf area showed seasonal variation, and severe defoliation was caused by a typhoon in the summer. The annual carbon assimilation was estimated at 3.50 Mg C ha−1 year−1 in the study area.

Highlights

Forests are the world’s largest terrestrial carbon sink and can sequester CO2 from the atmosphere, modify atmospheric components, mitigate greenhouse effects, and provide ecosystem services such as provisioning of fodder and timber and non-timber products that facilitate sustainable livelihoods
The aims of the present study were to clarify the seasonal dynamic on photosynthesis and carbon assimilation dynamics of Z. serrata plantations and identify the key environmental factors influencing its growth performance under tropical monsoon climates
Forests play a crucial role in terrestrial carbon budgets under climate change and provide several important ecosystem service functions

Summary

Introduction

Forests are the world’s largest terrestrial carbon sink and can sequester CO2 from the atmosphere, modify atmospheric components, mitigate greenhouse effects, and provide ecosystem services such as provisioning of fodder and timber and non-timber products that facilitate sustainable livelihoods. Environmental factors such as precipitation and soil water content may not be the major factors affecting carbon assimilation, whereas vapor pressure deficit and warming could strongly impact forest carbon sinks under drought conditions [5,6]. The impact of extreme weather on forests is becoming increasingly severe under climate change, especially in seasonally dry ecosystems, due to cycles of prolonged drought and heavy rain. Drought is the primary cause of stress in forest ecosystems under climate change and may increase tree mortality under climatic warming [6]. Increasing vapor pressure deficit under climatic warming can reduce forest CO2 uptake regardless of changes in soil water content, warming may be the main climate factor that impacts carbon storage in tropical dry region [5,6]. The forest response to changing environmental conditions may affect the regional and global climate [6]

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