东北温带森林常见树种粗根分解过程及调控因子

Coarse root decomposition and its control factors among 10 co-occuring common tree species in a temperate forest,Northeast China

粗根是森林生态系统中重要的碳库和养分库,对生态系统的碳和养分循环起着重要的作用。但目前人们对于影响粗根分解的主要因素以及粗根分解模式的研究较少。采用埋袋法对东北温带森林常见的10个树种(黄檗、胡桃楸、水曲柳、色木槭、红松、落叶松、白桦、春榆、紫缎、蒙古栎)的粗根(5—10 mm)进行了为期1年的分解实验研究,来探索粗根分解和养分释放的动态变化规律。研究结果表明:黄檗、胡桃楸、水曲柳、色木槭、红松、落叶松、白桦、春榆、紫缎、蒙古栎粗根年分解系数分别为0.826、0.897、0.477、0.341、0.358、0.264、0.244、0.593、0.458、0.227。由此可见,胡桃楸分解速率最快,蒙古栎分解速率最慢。在粗根分解过程中,不同调控因子对根系分解的影响不同。研究结果表明,粗根的分解速率与根系的初始C/N比例呈显著负相关(P<0.0001),与初始木质素含量呈负相关(P<0.0001),与初始非结构性碳水化合物(NSC)含量呈正相关(P<0.0001)。初始C/N、木质素含量与非结构性碳水化合物含量分别可以解释所研究的10个树种粗根分解速率的68%、20%与65%。研究结论对于预测粗根参与的碳循环与养分释放具有重要意义。

Coarse roots(>5 mm)are important functional organs of plants.Its main physiological function is to maintain the growth of fine roots while transporting and absorbing water and nutrients from the soil.while it also stores photosynthates,anchoring and supporting the above-ground parts of the plant.Coarse roots are conduits for nutrients and water,as well as storage sites for carbon and nutrients.In addition,the turnover of coarse roots slowly transports carbon and nutrients to the soil and soil organisms and affects the long-term ecosystem productivity and CO2 emissions of forests.Root decomposition is the main way that carbon and nutrients are returned to the soil.On average,the amount of underground litter in the forest accounts for about 48%of the total annual.Therefore,root decomposition is an important basis for the circulation of nutrients,carbon and energy within and between ecosystems,the biosphere and the atmosphere.Coarse root is important carbon pool and stock of nutrients in forest ecosystems,which plays an important role in the carbon and nutrient cycling of ecosystems.However,there are few studies on the dominant factors and decomposition patterns affecting the coarse root at present.In this study,the coarse roots(5-10 mm)of 10 tree species(Phellodendron amurense,Juglans mandshurica,Fraxinus mandschurica,Acer mono,Pinus koraiensis,Larix gmelinii,Betula platyphylla,Ulmus davidiana japonica,Tilia amurensis and Quercus mongolica)commonly found in the temperate forests of the Northeast China were studied by burier-bag method in 2020-2021,to explore the dynamic variation rule of the coarse root decomposition and release of nutrients.The results show that the annual decomposition coefficients of the coarse roots of Phellodendron amurense,Juglans mandshurica,Fraxinus mandschurica,Acer mono,Pinus koraiensis,Larix gmelinii,Betula platyphylla,Ulmus davidiana japonica,Tilia amurensis and Quercus mongolica are 0.826,0.897,0.477,0.341,0.358,0.264,0.244,0.593,0.458 and 0.227,respectively.The Juglans mandshurica decomposition rate is the fastest,while Quercus mongolica is the slowest.In the process of coarse root decomposition,different regulatory factors have different effects.The results prove that the decomposition rate of the coarse roots is negatively correlated with the initial C/N ratio of roots(P<0.0001)and initial lignin content(P<0.0001),but positive correlation with the initial non-structural carbohydrate content(P<0.0001).The initial C/N,lignin and non-structural carbohydrate content can explain 68%,20%,and 65%of the coarse root decomposition rates across the 10 tree species,respectively.The conclusion is significance for predicting the carbon cycle and release of nutrients of coarse roots.