Meta-analysis of the responses of tree and herb to elevated CO2 in Brazil

Abstract

The CO2 concentration has increased in the atmosphere due to fossil fuel consumption, deforestation, and land-use changes. Brazil represents one of the primary sources of food on the planet and is also the world's largest tropical rainforest, one of the hot spots of biodiversity in the world. In this work, a meta-analysis was conducted to compare several CO2 Brazilian experiments displaying the diversity of plant responses according to life habits, such as trees (79% natives and 21% cultivated) and herbs (33% natives and 67% cultivated). We found that trees and herbs display different responses. The young trees tend to allocate carbon from increased photosynthetic rates and lower respiration in the dark—to organ development, increasing leaves, roots, and stem biomasses. In addition, more starch is accumulated in the young trees, denoting a fine control of carbon metabolism through carbohydrate storage. Herbs increased drastically in water use efficiency, controlled by stomatal conductance, with more soluble sugars, probably with a transient accumulation of carbon primarily stored in seeds as a response to elevated CO2.

Tropical root responses to global changes: A synthesis

“…Although increasing global atmospheric CO 2 concentration is the main driver of global climate changes, its effects on fine roots are likely to be indirect responses: the direct effects of CO 2 occur only in leaves, with changes in roots being secondary or tertiary responses to changes in C allocation or interactions with water or nutrient economies. Although there have been few studies of elevated CO 2 responses in tropical trees (Cernusak et al., 2013; da Silva Fortirer et al., 2023) or forests, the relative response of root growth or root: shoot ratio to equivalent CO 2 was inconsistent, often varying with soil nutrient status (Figure 4; Table S9). Therefore, hypotheses can be proposed based on many studies of temperate regions while recognizing that responses in tropical ecosystems will be shaped by the overriding influence of soils and climate.…”

“…Although there have been few studies of elevated CO 2 responses in tropical trees (Cernusak et al, 2013;da Silva Fortirer et al, 2023) or forests, the relative response of root growth or root: shoot ratio to equivalent CO 2 was inconsistent, often varying with soil nutrient status (Figure 4; Table S9). Therefore, hypotheses can be proposed based on many studies of temperate regions while recognizing that responses in tropical ecosystems will be shaped by the overriding influence of soils and climate.…”