Estimation Of Forest Carbon Storage In Altay Mountains And Response Of NPP To Climate Change

The Altay Mountains are sensitive areas in arid and semi-arid regions of western China.The special geographical location makes the forests in the region show unique ecological functions in arid regional ecosystems.This paper takes Xinjiang Altay Mountains as the research object.Based on the results of the 2011 Xinjiang Forest Resources Survey,estimating the carbon storage and carbon density by the biomass source method is of great significance for estimating terrestrial carbon sinks.The main advantage tree species carbon content,in order to improve the carbon storage to choose the best suitable development of the tree species,provide data support for the Altay Mountains forestry carbon sequestration and afforestation technology.By analyzing the response of vegetation NPP to climate change,it is important to evaluate the environmental quality of terrestrial ecosystems,regulate ecological processes and estimate terrestrial carbon sinks.Based on the temperature,precipitation and SPEI meteorological data from 1960 to 2016,this paper analyzed the spatial and temporal distribution of climatic factors in the Altay Mountains for nearly 56 years.Using the MOD13Q1 remote sensing data from 1982 to 2013,the net primary productivity of the forests in the Altay Mountains was analyzed by the CASA model.Temporal and spatial variation characteristics and responses to climate change,the results show that:(1)The Altay Mountains have a total carbon storage of 48.267 Tg and an average carbon density of 48.0 Mg·hm-2.The proportion of carbon stocks in different forest vegetation types:arbor forest 41.494 Tg,shrub forest 4.278 Tg,sparse forest 2.394 Tg,scattered wood 0.095 Tg,and four-sided trees 0.005 Tg;the carbon density values of different forest vegetation types are:arbor forest 79.7 Mg·hm-2,four-sided trees 75.0 Mg·hm-2,scattered wood 45.6 Mg·hm-2,sparse forest 33.6 Mg·hm-2 and shrub forest 6.2 Mg·hm-2.The value of arbor forest is higher than other forest vegetation types in terms of carbon storage and carbon density.From a regional perspective,the carbon reserves of Fuyun Forest Farm accounted for 33.50%of the total carbon storage in the study area,and the carbon density was 54.1 Mg·hm-2,which is the main carbon pool of the Altay Mountains.(2)The carbon storage of arbor forest in the Altay Mountains is concentrated in mature and over-ripe forests with an average carbon density of 65.5 Mg·hm-2.The average carbon storage of arbor forests in different age groups was:mature forest>over-ripe forest>near-mature forest>middle-aged forest>young forest.The carbon storage of the former two accounts for 41.28%and 39.03%of the total carbon storage,respectively.The average carbon density of arbor forests in different age groups was:over-ripe forest>mature forest>near-mature forest>middle-aged forest>young forest age,indicating that the carbon sequestration capacity of mature forest and over-ripe forest was stronger than other age groups.In actual production management,The protection of mature and over-ripe forests should be strengthened to reduce over-harvesting.(3)The total average carbon content of dominant species in the Altay Mountains is 25928.7 g·kg-1.The total average carbon content of dominant species in mountainous areas is higher than that in the valley.By comparing the carbon content of the main dominant species in the Altay Mountains,the best suitable forest types in the Altay Mountains are The trees are sand dates,hawthorns and birches,and the shrubs are white thorns.(4)Temperature and precipitation in Altay Mountains in the past 56 years have changed abruptly in 1990,showing a change to warm and humid,showing low temperature and more precipitation in high altitude areas;SPEI in 1991a is an unstable fluctuation state,before and after the abrupt change,dry and wet are distinct,showing a positive pattern in space,which is mainly related to the vegetation condition,elevation and latitude of the region.(5)In recent 3 1 years,the spatial and temporal distribution of NPP in Altay Mountains showed an upward trend.The annual average NPP of vegetation was 162.94 g·m-2·a-1,which grew fastest in summer and slowly in spring and autumn.The spatial distribution showed that the annual average NPP was 81.71 g·m-2·a-1,and the total regional NPP was 45.18 Tg·a-1.The spatial distribution of NPP showed a trend of high mountain area and low basin.The annual and seasonal NPP trend test showed that the vegetation condition changed as a whole.The vegetation growth plays a major role in summer and spring.NPP in mountainous areas with good water content tends to increase,while that in plains with poor water condition tends to decrease slightly.The correlation analysis between NPP and climate factors shows that annual mean temperature,annual average precipitation and annual average SPEI are positively correlated with NPP,among which annual average precipitation and annual average SPEI have a higher response.