The Effect Of Increasing Nitrogen And Decreasing Water On Fine Root Morphology And Anatomy Of Main Tree Species In Changbai Mountain

The impact of nitrogen deposition and precipitation reduction caused by global climate change on the underground carbon cycle and fine root dynamics of forests has attracted much attention.As an important organ for plant to absorb,store and release nutrients,fine roots play an important role in the response of plants to nitrogen deposition and precipitation reduction.Control,nitrogen application,precipitation reduction and simultaneous nitrogen application were selected in this study,with 3 replicates for each treatment.The root system was graded according to the root order,the biomass of the fine root was measured,the morphological characteristics of the fine root were measured by the scanner,and the anatomical structure of the fine root was observed by paraffin section technique.Increased N deposition resulted in a significant decrease in cortical thickness of the 3rd order roots of Pinus koraiensis,the 2-3 order roots of Fraxinus mandshurica,and the 2nd to 4th order fine roots of Phellodendron amurense,the 4th order fine roots of Quercus mongolica,and the 1st to 2nd order fine roots of Tilia amurensis.The decrease of precipitation promoted the absorption function of the 3-order roots of Pinus koraiensis,Phellodendron amurense and Fraxinus mandshurica,and restricted their transportation function,and the cortex thickness and stele diameter of the 1-3 order fine roots of Quercus mongolica were increased,but the stele-to-root diameter ratio was significantly decreased.The root length,surface area and diameter of 1-2 order and 1-3 order of Pinus koraiensis and Phellodendron amurense were reduced,while the root diameter of 1-2 order of Quercus mongolica was increased but the length was reduced,and the root diameter of 3-5 order was reduced.The diameter of the 1-order of Tilia amurensis decreased,the diameter of the 2-order increased,and the diameter of the 1-st order root of Tilia amurensis increased.The results showed that(1)the response of fine roots to soil nitrogen enrichment was significantly different within and between species.The return of C input into 3-order of fine roots of Pinus koraiensis and Tilia amurensis were higher than that of other broad-leaved tree species.(2)Under the condition of decreasing precipitation,the fine roots of Pinus koraiensis and Fraxinus mandshurica adopt slow absorption strategy,the fine roots of Phellodendron amurense and Tilia amurensis adopt fast absorption strategy,and the fine roots of Quercus mongolica adopt two strategies.The decrease of precipitation led to the adjustment of the anatomical structure of the absorptive roots and the definition of the division of labor.(3)The decrease of precipitation may weaken the toxicity of soil acidification to the fine roots of Pinus koraiensis and Phellodendron amurense.