Above-and Belowground Carbon Allocation Of Plants In The Permafrost Peatland Of The Great Hing’an Mountains

The boreal peatland is an important carbon pool in the world,which is mainly distributed in permafrost regions.However,global warming and permafrost degradation have a profound impact on the composition and structure of plant communities in the region,which will also change the composition and stability of above-and belowground carbon pools in boreal peatlands.In this study,we used the method of spatial and temporal substitution,collected the samples of three plant functional types（deciduous shrubs,evergreen shrubs,and sedge）in seven permafrost peatlands（Beijicun,Tuqiang,Amuer,Pangu,Huzhong,Tahe,and Xinlin）,measured the total carbon（TC）,nitrogen（TN）,and phosphorus（TP）content,and the stable isotope values(δ¹³C andδ¹⁵N)of six tissues（leaves,green stems,brown stems,fine roots,medium roots,and coarse roots）,and combined with ecological stoichiometry（C:N,C:P,and N:P）to explore its response to climate change.We measured the concentration of non-structural carbohydrates（NSC）,structural carbohydrates（SC）,and total polyphenols（TPs）of plants from Xinlin and Tuqiang peatland in the island-shaped and continuous permafrost,respectively.And we collected the biomass of plants in the 1 m×1 m plots of Xinlin and Tuqiang peatland.Finally,calculated the carbon storage,carbohydrate storage,and total polyphenol storage of each tissue and discussed the differences in carbon allocation of different functional plants,and revealed the above-and belowground carbon allocation patterns of plants.The main findings are as follows:（1）TC,TN,and TP contents had an average of 470.69 ± 1.56,8.03 ± 0.23,and1.71 ± 0.61 mg·g^-1,respectively.The C:N,C:P,and N:P ratios had an average of 79.41±1.92,388.89±9.84,and 5.89±0.17,respectively.TC content in shrubs was higher than that of sedge,and the content of TN and TP in shrub leaves was higher than that in stems and roots.There was a similar trend of TN and TP contents,and stoichiometric ratios from leaves to roots between deciduous and evergreen shrubs.The N:P ratio in leaves of sedge（11.61±1.83）was between 10and 20,while that of deciduous（8.50±0.74）and evergreen shrubs（7.36±0.55）was lower than10,showing that sedge was N and P co-limitation while shrubs only limited by N,which was one of the reasons for the expansion of shrubs in the peatland of the Great Hing′an Mountains.（2）Theδ¹³C andδ¹⁵N had an average of-29.16±0.05‰and-4.39±0.08‰.The values ofδ¹³C andδ¹⁵N were significantly higher in leaves and roots of sedge than those of shrubs,which means shrubs had higher nutrient acquisition strategies.That was also an important reason for the expansion of shrubs in this area.Theδ¹³C value was negatively correlated with mean annual temperature,implying warming could increase plant photosynthesis in boreal peatland.（3）In this study,NSC includes soluble sugar（SS）and starch（ST）,SC includes cellulose（CE）and lignin（LI）.The average concentrations of NSC,SS,ST,SC,CE,LI,and TPs of plants in island-shaped permafrost peatland（Xinlin）were 11.58±1.18%,7.17±0.89%,4.42±0.79%,41.16±2.22%,25.57±0.43%,15.59±2.04%and 5.10±1.66%,respectively.The average concentrations of NSC,SS,ST,SC,CE,LI,and TPs of plants in continuous permafrost peatland（Tuqiang）were 9.06±1.06%,6.53±1.45%,2.52±0.43%,47.80±1.59%,29.55±0.72%,18.25±1.25%and 3.61±0.46,respectively.The ST concentration of plants in Xinlin peatland was significantly higher than that of plants in Tuqiang peatland（p<0.05）,which means that warming could promote the non-structural carbohydrates in plants more converted into starch.There were differences in the response of carbohydrates concentrations to climate change in different functional plants.The structural carbohydrates of evergreen shrubs and sedges decreased with warming,which was not conducive to the construction and growth of their plant tissues and organs.Deciduous shrubs,by contrast,were more stable and adaptable to warmer climates.（4）The average biomass,carbon storage,NSC storage,and SC storage of plants in island-shaped permafrost peatland（Xinlin）were 139.70±17.89 g·m^-2,67.66±8.87 g·m^-2,146.48±21.43 mg·m^-2,and 774.70±111.47 mg·m^-2,respectively.The average biomass,carbon storage,NSC storage,and SC storage of plants in continuous permafrost peatland（Tuqiang）were 136.36±18.84 g·m^-2,60.45±8.49 g·m^-2,134.68±19.45 mg·m^-2,and 787.43±109.43 mg·m^-2,respectively.Although there was no significant difference in the average values of plant storage among the sample plots,for different functional plants,the biomass,carbon storage,NSC storage,and SC storage of deciduous shrubs were significantly higher than those of evergreen shrubs and sedges（p<0.05）,indicating that deciduous shrubs in this region have higher carbon storage capacity.Moreover,the starch storage of deciduous shrubs in the Xinlin peatland was significantly higher than that in the Tuqiang peatland and the starch storage of deciduous shrubs increases with climate warming,indicating that climate warming enhances the photosynthetic capacity of deciduous shrubs.（5）There was more carbon in the brown stems of aboveground,while more carbon in the coarse roots of belowground.Overall,the belowground biomass（y₁）,carbon storage（y₂）,structural（y₃）,and nonstructural carbohydrate storage（y₄）of plants in peatlands were higher than those in the aboveground（x）,and the linear correlation was significant,indicating a heterotrophic growth relationship（y₁=1.6557 x-6.3020,R²=0.8192;y₂=1.6444 x-3.5748,R²=0.8197;y₃=1.8016 x-39.6844,R²=0.7511;y₄=1.3828 x+11.8594,R²=0.4517;p<0.01,n=30）.In conclusion,this study based on the analysis of carbon-related indicators for above-and belowground tissues of different plant functional types in the boreal peatland,clarified the above-and belowground carbon allocation characteristics of carbon content,ecological stoichiometry,stable isotopes,carbohydrates,and carbon reserves of plants,and combined with the correlation analysis of biodiversity and biomass,revealed the above-and belowground carbon allocation pattern of plants in the peatland.Discussed the response of above-and belowground carbon allocation of peatland plants to climate warming.This study provided important data for the in-depth understanding of the above-and belowground carbon allocation of plants in the peatland,especially research on the carbon composition of roots,complementing and improving the research on the carbon pool of plants in the Great Hing’an Mountains peatland,and helping to understand the response of plants in the Great Hing’an Mountains peatland to climate warming.