CARBON ENRICHMENT IN TREES IN RESPONSE TO ELEVATED CO2, NITROGEN TEMPERATURE, DROUGHT, AND OZONE: A META-ANALYSIS

Abstract

The era of 1700 saw industrial and societal development. However, it adversely contributed to the depletion of natural resources and increased emissions of carbon dioxide (CO2). Since CO2 is a greenhouse gas, it became a global cause of concern. In some studies, CO2 is known for its adverse effects on human health and the ecosystem. While other studies show increased CO2 concentration in the environment promote greater amount of CO2 being absorbed by the plants (termed as eCO2). This eCO2 facilitates photosynthesis and supplements the biomass growth in trees. The positive impacts of eCO2 are largely dependent upon factors such as plant species, genetic makeup, absorption site conditions, drought conditions, ozone levels and concentrations of nitrogen. Despite preliminary stimulation of photosynthesis that the literature focuses on, under the outcome of eCO2, the plant incurs a down-regulation known as photosynthetic acclimation. The aim of this study was to analyze the allocation of biomass in forest species under eCO2 effect and to assess the different environmental factors that contribute to biomass. For this purpose, a meta-database using woody species of plants was developed (timeline 2000 to 2021). Two values for dry biomass were extracted: the ambient levels and the elevated levels of CO2. Standard error for the dry biomass was recorded respectively. The data was presented in either table or in the form of figures. The digitization of the figures was done using the software “GetData” and then incorporated into the meta-database. To understand the way elevated levels of CO2, affect the assimilation of carbon into biomass in the tree species is the main goal of meta-analysis. As well as how there is a shift of biomass allocation at the eCO2. The meta-analysis was done in a multi-factorial way where other treatments viz. drought, nitrogen, ozone, and temperature effect the carbon allocation pattern was also studied. In the current study, it was concluded that there is an overall positive response to carbon treatment which results in overall increase of tree mass as well its tissues like leaves, stems, and roots. Nitrogen, drought, temperature, and ozone also have a positive effect on CO2 enrichment demonstrated by the positive change in percentage of biomass in the total biomass, leaf biomass, root biomass and stem biomass of the trees. Although the results suggest that CO2 enrichment is most likely to be enhanced if there is more availability of nutrients for the trees which is evident by the increase in biomass as compared to low nutrient availability.