Interaction Effect between Elevated CO₂ and Fertilization on Biomass, Gas Exchange and C/N Ratio of European Beech (Fagus sylvatica L.).

Neda Lotfiomran,Jörg Fromm,Michael Köhl

doi:10.3390/plants5030038

Neda Lotfiomran, Jörg Fromm + Show 1 more

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https://doi.org/10.3390/plants5030038

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Abstract

The effects of elevated CO2 and interaction effects between elevated CO2 and nutrient supplies on growth and the C/N ratio of European beech (Fagus sylvatica L.) saplings were studied. One-year-old beech saplings were grown in a greenhouse at ambient (385 ppm) and elevated CO2 (770 ppm/950 ppm), with or without fertilization for two growing seasons. In this study, emphasis is placed on the combined fertilization including phosphorus, potassium and nitrogen with two level of elevated CO2. The fertilized plants grown under elevated CO2 had the highest net leaf photosynthesis rate (Ac). The saplings grown under elevated CO2 had a significantly lower stomatal conductance (gs) than saplings grown under ambient air. No interaction effect was found between elevated CO2 and fertilization on Ac. A interaction effect between CO2 and fertilization, as well as between date and fertilization and between date and CO2 was detected on gs. Leaf chlorophyll content index (CCI) and leaf nitrogen content were strongly positively correlated to each other and both of them decreased under elevated CO2. At the end of both growing seasons, stem dry weight was greater under elevated CO2 and root dry weight was not affected by different treatments. No interaction effect was detected between elevated CO2 and nutrient supplies on the dry weight of different plant tissues (stems and roots). However, elevated CO2 caused a significant decrease in the nitrogen content of plant tissues. Nitrogen reduction in the leaves under elevated CO2 was about 10% and distinctly higher than in the stem and root. The interaction effect of elevated CO2 and fertilization on C/N ratio in plants tissues was significant. The results led to the conclusion that photosynthesis and the C/N ratio increased while stomatal conductance and leaf nitrogen content decreased under elevated CO2 and nutrient-limited conditions. In general, under nutrient-limited conditions, the plant responses to elevated CO2 were decreased.

Highlights

Carbon dioxide is a natural component of the atmosphere and an essential factor for the growth of trees since nearly half of their constituents are composed of carbon
Plants grown under elevated CO2 conditions produced significantly heavier stems (Figure 1), but the differences between fertilized and unfertilized plants grown under different CO2 levels were not significant (Table 1)
Fertilization alone had no effect on dry weight but under elevated CO2, the difference between the dry weight of the leaves of unfertilized and fertilized plants was significant (Table 1)

Summary

Introduction

Carbon dioxide is a natural component of the atmosphere and an essential factor for the growth of trees since nearly half of their constituents are composed of carbon. The CO2 content in the ambient atmosphere has not been constant through time. Since around 1850, it has continuously risen from about 270 ppm to around 400 ppm at present and will continue to do so in future [1]. Carbon dioxide emissions are the most important cause of global warming. As a sink for CO2 , forests play an important role in the discussion about global warming [2]. The recent rise of the CO2 content

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