Main Land Vegetation Productivity And Their Relationship With Climatic Factors In China

In the context of global warming,it is important to study the net primary productivity of forests,grasslands and desert vegetation and their relationship with climate factors.This study uses the GIMMS3 g remote sensing time series dataset for nearly 34 years,combined with meteorological data and vegetation type data.The CASA model was used to estimate the NPP and its spatial and temporal changes in forests and different forest vegetation types,grasslands and deserts from 1928 to 2015.The second-order partial correlation analysis method was used to analyze the interannual correlation between forest and different forest vegetation types,grassland and desert vegetation NPP and climatic factors.The sliding partial correlation analysis method was used to analyze the correlation between NPP and climate factors of forests and different forest vegetation types,grassland and desert vegetation with time.conclusion as below:(1)From 1982 to 2015,the annual average NPP of forest vegetation is 887×1012 g C/a,and the annual average NPP per unit area is 650.73 g C/m2/a.It shows a decreasing distribution from southeast to northwest.The highest unit of NPP is the evergreen broad-leaved forest.The carbon sequestration capacity of forests and different forest vegetation types has increased year by year,and NPP has generally improved.The NPP of forest vegetation increased significantly in summer and autumn(P<0.05).The evergreen broad-leaved forest increased significantly in summer(P<0.05).The NPP of deciduous broad-leaved forest increased significantly in summer and autumn(P<0.01).The evergreen coniferous forest and deciduous broad-leaved forest increased significantly in spring(P<0.01).The summer NPP of mixed forests increased the fastest(P<0.01).The average annual temperature of the forest in the forest area increased significantly(P<0.01).The year-on-year increase in temperature has a positive impact on the accumulation of NPP in forest vegetation.The decline in precipitation may have a negative impact on NPP.Increasing annual solar radiation has a positive effect on the accumulation of NPP.The sensitivity of forest vegetation to temperature has increased year by year,and the sensitivity to precipitation has gradually decreased.The sensitivity of deciduous broad-leaved forest,deciduous coniferous forest and mixed forest to air temperature increased year by year,and the sensitivity of evergreen broad-leaved forest and evergreen coniferous forest to air temperature decreased year by year.The sensitivity of deciduous broad-leaved forests and evergreen coniferous forests to precipitation increased year by year,and the sensitivity of the other three to precipitation decreased year by year.The sensitivity of the five types of forest vegetation to solar radiation has been decreasing year by year.(2)The average annual average NPP of grassland vegetation from 1982 to 2015 was 245.52×1012 g C/a,and the annual average NPP per unit area was 186.39 g C/m2/a.It shows a gradual increase in distribution characteristics from southwest to northeast.The carbon sequestration capacity of grassland vegetation has increased year by year,and NPP has generally improved.NPP peaked in July and August.NPP in all seasons is growing,with the fastest in spring.The temperature and solar radiation in the grassland area increased significantly(P<0.05).The increase in temperature contributes to the accumulation of NPP.Precipitation and solar radiation are key controlling factors for grassland vegetation growth.The sensitivity of grassland vegetation to temperature and solar radiation is gradually decreasing,and the sensitivity to precipitation is increasing year by year.(3)The annual average NPP of desert vegetation from 1982 to 2015 was 58.52×1012 g C/a,and the average NPP per unit area was 50.22 g C/m2/a.There are more southeastern and northwestern parts,less distribution in the south and middle east,but the overall level of NPP in desert vegetation is lower.NPP has generally improved,and carbon sequestration capacity has increased year by year,but it has declined in some areas.The accumulation period of NPP is from April to October.The NPP of all seasons is increasing and the winter is the fastest.The annual average temperature,precipitation and solar radiation in the desert area showed a significant increase(P<0.01).Precipitation and solar radiation are the main limiting factors for the growth of desert vegetation.In the context of global warming,the sensitivity of desert vegetation to temperature,precipitation and solar radiation has decreased year by year.