Effects Of Nitrogen And Water Reduction On Carbon And Nitrogen Distribution In Early Spring Herbaceous Plants

In early spring,the herbaceous plants,as a special ecological layer under the deciduous broad-leaved forest,plays an important role in the energy flow and material circulation of the forest ecosystem.At present,the increase in nitrogen deposition and changes in precipitation patterns in the context of global climate change have had an impact on the stability and the development process of the ecosystem.Therefore,to investigate the effects of increased nitrogen deposition and reduced precipitation on early spring herbaceous plants,in this study,artificial simulated nitrogen deposition and precipitation control experiments were conducted in broad-leaved Korean pine forest in Changbai Mountain.Four treatments were designed: control treatment(CK),nitrogen addition treatment(N),water reduction treatment(W),nitrogen addition and water reduction(NW),the biomass,root morphological traits and ecological stoichiometry of 17 species of early spring herbs were measured,the effects of nitrogen deposition and precipitation on the growth and survival strategies of herbaceous plants in early spring were compared and analyzed.Research indicates:(1)For the early spring herb biomass in the experiment,most of the early spring herbaceous plants would increase their biomass compared with the control and water-reducing treatment under the nitrogen addition treatment.Among them,for early spring herbaceous plants with well-developed underground tubers or significantly downward grading of the root system,the root-to-crown ratio would increase compared with the control and water-reducing treatment,the early spring herbaceous plants were tending to develop toward underground plant organs;while for early spring herbaceous plants with underdeveloped underground tubers or single root systems,the root-to-crown ratio would decrease compared with the control and water-reducing treatment,the plant development tended to aboveground plant organs.(2)For the root morphological traits of the early spring herbs in the experiment,under the water-reducing treatment,the biomass of most early spring herbs was reduced compared with the other treatments.Under the interaction of nitrogen addition and water reduction,the biomass of most early spring herbaceous plants would increase compared with the other treatments.Among them,the increase in biomass of herbaceous plants in the early spring was more obvious than that of the water-reducing treatment.It was showed that applying nitrogen to plants under drought conditions was conducive to plant nutrient development,and plants with more developed underground tubers were more inclined to the development of underground plant organs.(3)For the root morphological traits of the early spring herbs in the experiment,overall nitrogen addition treatment increased the total root length and total root surface area of early spring herbaceous plants compared with the other three treatments.Compared with the control,the other treatments reduced the root average diameter of most early spring herbs,and the treatments had no significant effect on total root length and total root surface area.Under water-reducing conditions,nitrogen addition treatment increased the total root length and total root surface area of most early-spring herbaceous plants,while the average root diameter did not change significantly.Increasing the total root length and total root surface area were conducive to plants absorbing more nutrients for growth and development.(4)For the overall above-ground stoichiometric ratio of herbaceous plants in the experiment,nitrogen deposition and water-reducing changes under nitrogen deposition have more influence on the content of chemical elements and stoichiometric ratio of the above-ground plants.Compared with the control,the other treatments all decreased the P content on the ground(by 7.5% to 12.9%),and the increase in nitrogen deposition and decrease in precipitation were mostly not conducive to the absorption and transformation of P content in the early spring herbaceous plants.The increase of nitrogen deposition and the change of water loss under the condition of nitrogen deposition have a great influence on the absorption and transformation of N in the early spring herbaceous plants.(5)For the overall underground stoichiometric ratio of herbaceous plants in early spring,the decrease of precipitation and the increase of nitrogen deposition under the condition of reduced precipitation had more influence on the content of underground chemical elements and stoichiometric ratio of plants.Compared with the water-reducing treatment,nitrogen addition and water reduction resulted in a significant decrease in underground P content(P<0.05)and a significant increase in underground C:P(P<0.05);compared with the nitrogen addition treatment,nitrogen addition and water reduction significantly increased the underground C:N ratio(P<0.05),and the reduced water treatment significantly reduced the underground N:P(P<0.05).(6)For the aboveground and underground stoichiometric ratios of herbaceous plants in early spring,nitrogen addition treatment had a significant effect on the correlation between aboveground and underground N content and its stoichiometric ratio,water-reducing treatment had a significant impact on the correlation between aboveground and underground P content and its stoichiometric ratio,the interaction of nitrogen addition and water reduction had a significant effect on the correlation of aboveground and underground C content,N content and C:N.In conclusion,simulated environmental conditions that increased nitrogen deposition and reduced precipitation,the study of changes in biomass,root morphological traits and stoichiometric ratios of early spring herbaceous plants has important implications for exploring strategies for balancing the growth of early spring herbaceous plants,for the energy cycling of ecosystems,and for changing ecosystem carbon pools.