What is the fine-grained topic of the following text: Authors: Lipson, D. A.; Wilson, R. F.; Oechel, W. C.
This study reports the effects of long-term elevated atmospheric CO2 on root production and microbial activity, biomass, and diversity in a chaparral ecosystem in southern California. Only return the topic.
Effects of long-term elevated atmospheric CO2 on root production and microbial activity in a chaparral ecosystem in southern California.