Research On Space-time Change Of Forest Net Primary Productivity In Permafrost Region Of Heilongjiang Province And Its Response Relation Between Surface Temperature

The northeastern part of Heilongjiang Province has a highly latitude geographical location that is strongly sensitive to temperature,a permafrost environment with cold temperatures all year round,and a complex and variable forest ecosystem,so Global climate change will bound to have a strong impact on its ecosystem.Through the study of the productivity and ground temperature of forest ecosystems in permafrost regions,capable of combing the spatiotemporal changes of forest ecosystem productivity and frozen land temperature in long-term sequences,By revealing the response relationship between the two,we can reveal the sensitivity of forest ecosystems in high latitudes permafrost regions to global climate change.Net primary productivity(NPP)and single tree biomass of forest ecosystems are important indicators that reflect the productivity of forest ecosystems at the macro-regional and individual tree scales,Because it has the advantages of relatively simple acquisition,disturbance to forests,and low destructive power,it is the focus and focus of current research on the development of forest ecosystem production.Ground temperature,as an indicator of frozen soil classification and frozen soil degradation,has the advantages of simple acquisition and mature geostatistical analysis techniques,and is a good carrier for frozen soil degradation research.This study uses mechanism models,empirical models,geographic information system methods,and geostatistical method.Analysis of the spatial and temporal distribution of net primary productivity(NPP)and surface temperature of forest ecosystems in the permafrost regions of northeast Heilongjiang Province in 2004,2008,2013,and 2018,Revealing the spatial-temporal trends of ground temperature and net primary productivity in forests from 2004 to 2018,Further analysis of the relationship between the degradation of frozen soil and the productivity of forest ecosystems;The measured tree core sample data was used to estimate the biomass of the larch single tree and the annual new biomass between 2000 and 2018,and the annual new biomass at the single tree scale and the change in surface temperature were analyzed accordingly.The development of forest production at two scales and the results of ground temperature response are used as scientific support for future climate change and rational management of forest ecosystem decisions in high latitude permafrost regions.The main conclusions of this study are as follows:(1)The average forest net primary productivity(NPP)in the growing season of Heilongjiang Province in the permafrost region showed a general downward trend from 2004 to 2018,and there are obvious differences in partition distribution.During 2004-2018,the production capacity of forest ecosystems in permafrost regions showed a slight increase.The productivity of forest ecosystems in permafrost regions is basically stable,Moreover,the productivity of forest ecosystems in these two frozen soil regions has obvious north-south distribution differences,due to the high latitude in the north,the production capacity is weaker than in the south.The productivity of forest ecosystems in sparse island-like frozen soil regions for many years is weakening,and as the latitude decreases,the degree of production capacity weakening increases.(2)The surface temperature of 0 m in the permafrost region of Heilongjiang Province has obvious spatial distribution differences within and outside the study area.The ground temperature in the forested area is lower than that in the non-forested area,which indicates that the forest ecosystem has a lowering effect on the surface temperature during the production process.It can be further speculated that the forest ecosystem has delayed the degradation of frozen soil caused by global climate change to some extent speed.In the complex production process of forest ecosystems in different frozen soil types,due to different latitudes or altitudes,the effect of delaying the degradation of frozen soil may have different degrees of strengthening or weakening effects.The temporal and spatial changes of surface temperature in permafrost regions also have obvious regional differences.The temperature changes in permafrost regions and permafrost regions are not obvious.Improve change.(3)The correlation analysis results of the net primary productivity(NPP)and surface temperature of forest ecosystems from 2004 to 2018 also have obvious regional differences.Forest ecosystems and surface temperature changes in different types of permafrost regions have different responses: The change of NPP to surface temperature in forest ecosystems in permafrost regions is weakly positive sensitivity.NPP will increase with the increase of ground temperature,and the sensitivity has obvious latitude distribution differences.Forest ecosystems in permafrost regions have a strong positive sensitivity to surface temperature,and NPP will increase significantly with increasing ground temperature.The responses of forest ecosystems and surface temperature in the sparse island-like frozen soil regions for many years have obvious latitude differences,from high to low latitudes,they gradually change from forward sensitivity to reverse sensitivity,and the sensitivity also has obvious latitude differences.The area north of the south boundary of permafrost shows a strong inverse correlation,that is,the forest ecosystem will decrease as the surface temperature increases.This correlation result is basically consistent with the trend analysis results of forest net primary productivity(NPP)and surface temperature.(4)Biomass research of larch tree in three plots of Tahe,Xinlin and Hanjiayuan from 2000 to 2018,In the same growing environment,older trees are less sensitive to external influences,and older trees occupy much more resources and energy in forest ecosystems than other vegetation.In the future climate change research,we should pay more attention to young trees.In the process of forest production research and forest ecosystem management,we should pay more attention to older trees.