Effects of long-term nitrogen addition and decreased precipitation on the fine root morphology and anatomy of the main tree species in a temperate forest

Fine root traits vary under increased nitrogen (N) deposition and decreased precipitation across root orders and species, and these differences reflect plant belowground carbon allocation and survival strategies. We aimed to investigate how fine roots respond to N deposition and precipitation changes and provide a database of related information. A long-term platform to explore the changes in fine root morphology and anatomy in response to N addition and decreased precipitation was established in a temperate forest in northern China. The response of Pines koraiensis (PK) fine root diameter, stele diameter and stele-to-root ratio to N deposition differed from that of broadleaf species. Fine roots coordinated nutrient absorption with transportation by changing carbon allocation. Decreased precipitation caused Phellodendron amurense (PA) and Tilia amurensis (TA) to produce thinner fine roots with fast absorption capacity and PK and Fraxinus mandshurica (FM) to produce thicker fine roots with slow absorption capacity. The total absorptive capacity of the fine roots of Quercus mongolica (QM) had the smallest change. The interaction of N deposition with decreased precipitation on fine roots depends on tree species and may be inhibited or synergistic. This study provides insight into the variations in fine root dynamics among five tree species that are associated with environmental conditions and forecasts the trend of belowground carbon storage in boreal forests under multifactor climate change.