| Oasis shelter forest is the main body of forest carbon storage in arid areas,accounting for more than 80%of its total storage.Populus alba var.pyramidalis Bge.is the main tree species in the construction of shelter forest in this area,which is of great significance for estimating the biomass and carbon sink function of the regional farmland shelter forest system.In the past,although there were related studies on the biomass and its distribution pattern of Populus alba var.pyramidalis Bge.farmland shelter forest,there was a lack of systematic understanding on the temporal and spatial distribution of biomass and carbon sequestration characteristics of different age structure forest belt,which directly affected the accuracy of estimating the total biomass and carbon sequestration function of regional shelter forest.In this paper,taking the typical farmland shelterbelt of Populus alba var.pyramidalis Bge.in Dengkou oasis,the edge of Ulan Buh Desert as the research object,using the method of space instead of time,based on the measurement of standard wood and the monitoring of fixed sample plot,the biomass distribution rules of four different forest ages of Populus alba var.pyramidalis Bge.,including young forest,middle age forest,near mature forest and mature forest,were analyzed;and the temporal and spatial distribution characteristics of the biomass and carbon storage of Populus alba var.pyramidalis Bge were studied at different tree-age;the biomass and carbon storage model and calculation method of poplar single plant,forest belt,forest network Populus alba var.pyramidalis Bge.were constructed at different tree-age;and the relationship between the biomass and carbon storage of forest belt and its windproof and carbon sequestration benefits was quantitatively recognized;the evaluation method of wind and carbon sequestration benefits of protective forest was established,and the comprehensive function of protective forest in Dengkou oasis was evaluated,so as to provide the sustainable protection forest for farmland of Populus alba var.pyramidalis Bge.in arid area continuous operation and health management provide scientific and technological support.The main results are as follows:(1)The change rule of biomass per plant in different tree-age shows that there are significant differences in the analysis of variance of individual plant biomass among different tree-age.The biomass is positively correlated with tree-age,and its peak appeared in mature forest.At this time,when the number of shelterbelt is mature,appropriate thinning should be carried out.In this study,the maximum DBH of a single poplar can reach 41.97 cm,and its total biomass can reach 872.304 kg,with an average annual increment of 43.615 kg/A,the biomass is higher than that in similar areas,indicating that the research model in this paper has an obvious effect on improving the quality and efficiency of the cultivation of high biomass and large-diameter grade wood.(2)The change of biomass of each organ of a single plant at different tree-age shows that:the average distribution proportion of total biomass of a single plant turned into the distribution law of stem>taproot>branch>lateral root>bark>leaf,but in the middle age forest,the branch biomass ratio will exceed the root because of the rapid growth of branch biomass.The results show that the tree-age has a great influence on the distribution proportion of each organ of biomass,but the performance of each organ is different.The proportion of stem biomass shows a continuous growth trend with tree-age,while the proportion of other organs show a decreasing trend.The root biomass of Populus alba var.pyramidalis Bge.is mainly distributed in 0-150 cm soil layer,the taproot accounts for about 61.11%of root biomass,and the average distribution proportion of biomass of thick root,large root,medium root,small root and fine root of 5-grade lateral root were 51.13%?30.42%?12.79%?4.06%?12.34%,respectively.With the increase of tree-age,the biomass of taproot,thick lateral root and large lateral root increases,but the distribution proportion and spatial distribution of biomass in all levels of roots have no significant change,which shows that the tree-age has an obvious increase effect on the accumulation of root biomass,but has little effect on its distribution proportion and spatial distribution of root biomass in each soil layer.With the increase of soil depth,the root system decreases gradually at different tree-age,and distributes intensively in shallow soil layer.(3)The changes of carbon content in each organ of a single plant in different tree-age show that the carbon content of each organ of Populus alba var.pyramidalis Bge.can be divided into four categories:high,medium,low and extremely low.Among them,high carbon organs include stem,branch and taproot,with carbon content between 45.28%and 46.04%;medium carbon organs include bark,thick lateral root,large lateral root and leaf,with carbon content between43.23%and 44.04%;low carbon organs include medium lateral root and small lateral root,with carbon content between 40.62%and 41.46%;extremely low carbon organ is mainly fine lateral root,with carbon content around 36.91%.There is no significant difference in carbon content in different organs of Populus alba var.pyramidalis Bge.,and the comparison results are as follows:stem>branch>taproot>bark>thick lateral root>large lateral root>leaf>medium lateral root>small lateral root>fine lateral root.(4)The change rule of carbon storage in each organ of a single plant in different tree-age belts shows that the spatial-temporal distribution characteristics of carbon storage accumulation process and distribution ratio of Populus alba var.pyramidalis Bge.are basically consistent with the biomass.And the tree-age has a significant role in promoting the carbon storage accumulation of trees,but the increase of carbon storage is far less than the biomass.The maximum carbon storage single plant of Populus alba var.pyramidalis Bge.is 397.406 kg,and the annual increment is 18.924 kg/A,higher than that in similar areas,which shows that the shelter forest model in this study can enhance the carbon fixation function of the forest belt.Because of the difference of carbon content in different organs carbon at different tree-age,the distribution ratio of carbon and biomass is quite different,especially in different soil layers.The distribution ratio of taproot carbon storage in 0-50 cm and 50-100 cm soil layers is 27.87%and 29.90%higher than that of biomass respectively,and that of lateral roots is 45.97%and 42.90%lower than that of biomass respectively.(5)The study on the relationship between biomass,carbon storage and windproof and carbon sequestration efficiency of poplar shelter forest shows that biomass and carbon storage are closely related to windproof and carbon sequestration benefits,they are positively related to carbon sequestration benefits,but negatively correlated with porosity of the core index of windproof efficiency.Upper limit of biomass and carbon storage of Populus alba var.pyramidalis Bge.is quantitative by water in farmland forest net,and theirs'the lower limit,which is composed of two rows with a plant row spacing of 1 m×2 m or 1.5 m×3 m,are 94-100 t/hm~2and 43-47 t/hm~2,respectively,the forest belt is close to the sparse structure,which has good windproof benefit.The results show that the biomass and carbon storage of farm shelterbelt of the Dengkou county area are 1.57 t/hm~2 and 0.79 t/hm~2,respectively,with great potential for increase and poor windproof benefit.Therefore,it is necessary to strengthen the construction of shelterbelt to improve the windproof and carbon sequestration benefit. |
PDF Full Text Request