Stable isotope signatures reflect competitiveness between trees under changed CO2/O3 regimes

Area of Science:

• Plant Ecology
• Environmental Science
• Biogeochemistry

Background:

• Interactions between plant species are crucial for ecosystem dynamics.
• Environmental factors like increased ozone (O3) and carbon dioxide (CO2) concentrations influence plant competition.
• Understanding resource allocation and plant performance under changing conditions is vital.

Purpose of the Study:

• To synthesize experimental findings on inter-plant competition between beech (Fagus sylvatica) and spruce (Picea abies).
• To investigate the effects of elevated O3 and CO2 on the competitiveness of these species.
• To mechanistically interpret plant competitiveness using space-related resource investments and gains, integrating stable isotope data.

Main Methods:

• Synthesis of key findings from a series of experiments.
• Quantification and mechanistic interpretation of plant competitiveness.
• Utilizing stable isotopes (Delta(13)C, delta(18)O) as temporal integrators of plant performance (photosynthesis, water use, nitrogen uptake).

Main Results:

• Beech, the weaker competitor, showed decreased aboveground resource investment efficiency when competing with spruce.
• Beech's resource investment efficiency was positively related to Delta(13)C and stomatal conductance, but negatively to delta(18)O.
• Spruce exhibited strong belowground water competition, paralleled by a high nitrogen assimilation capacity.

Conclusions:

• Combining stable isotope analysis with space-related competitiveness investigations provides mechanistic insights into plant resource competition.
• Environmental changes (elevated O3 and CO2) significantly alter competitive dynamics between beech and spruce.
• Understanding species-specific resource strategies is essential for predicting forest ecosystem responses to global change.