Long-term nitrogen addition and drought altered root trait and plant biomass allocation of five herbs in early spring in a temperate forest

In early spring, because the tree and shrub layers are still dormant, the absorption of nutrients by herbs is the key factor to maintain nutrients in temperate forest ecosystems, but it is not clear whether climate change will change the nutrient uptake strategy of herbs. Therefore, we measured the biomass, fine root morphology, and stoichiometry of five dominant herbs in response to environmental changes in early spring in a temperate forest in northeastern China. The results showed that (1) Fine root morphology had strong plasticity. Under nitrogen addition treatment, the herbs tended to change the fine root length to absorb soil nutrients and water. (2) Under drought treatment, the herbs distributed more biomass to the belowground. Maintaining a higher root-shoot ratio might increase the relative supply of water to the herbs. (3) Nitrogen addition significantly decreased the belowground biomass allocation, but increased the ratio of belowground nitrogen to phosphorus (N:P) and the root metabolic activity. (4) Ephemeral herbaceous fine root morphology was more sensitive to water and nitrogen than other herbaceous plants. Collectively, in the context of climate change, early spring herbs may respond to environmental pressure through self-regulation and change growth strategies in temperate forest ecosystems.