The influence of elevated CO 2 and soil depth on rhizosphere activity and nutrient availability in a mature Eucalyptus woodland

作者：Johanna Pihlblad, Louise C. Andresen, Catriona A. Macdonald, David S. Ellsworth, Yolima Carrillo · 发表于：Biogeosciences · 年份：2023 · DOI：10.5194/bg-20-505-2023 · 被引用次数：22 · 研究领域：Plant responses to elevated CO2、Soil Carbon and Nitrogen Dynamics、Fire effects on ecosystems

Abstract. Elevated carbon dioxide (eCO2) in the atmosphere increases forest biomass productivity but only where soil nutrients, particularly nitrogen (N) and phosphorus (P), are not limiting growth. eCO2, in turn, can impact rhizosphere nutrient availability. Our current understanding of nutrient cycling under eCO2 is mainly derived from surface soil, leaving mechanisms of the impact of eCO2 on rhizosphere nutrient availability at deeper depths unexplored. To investigate the influence of eCO2 on nutrient availability in soil at depth, we studied various C, N, and P pools (extractable, microbial biomass, total soil C and N, and mineral-associated P) and nutrient cycling processes (enzyme activity and gross N mineralisation) associated with C, N, and P cycling in both bulk and rhizosphere soil at different depths at the Free Air CO2 enrichment facility in a native Australian mature Eucalyptus woodland (EucFACE) on a nutrient-poor soil. We found decreasing nutrient availability and gross N mineralisation with depth; however, this depth-associated decrease was reduced under eCO2, which we suggest is due to enhanced root influence. Increases in available PO43-, adsorbed P, and the C : N and C : P ratio of enzyme activity with depth were observed. We conclude that the influences of roots and of eCO2 can affect available nutrient pools and processes well beyond the surface soil of a mature forest ecosystem. Our findings indicate a faster recycling of nutrients in the rhizosphere, ra...