Spatial Representation And Variation Characteristics Of Water And Heat Fluxes In Larix Gmelinii Forest

The cold-temperate coniferous forest is a unique forest type in northeastern China.As an endemic species in the cold-temperate coniferous forest in China.It is necessary to study the water and heat fluxes of the Larix gmelinii forest ecosystem and has high scientific and geographical representation.This research,the Larix gmelinii forest ecosystem was used as the research object,Based on the Footprint model,the flux spatial representation of different time scales was studied using the flux observation data and meteorological data of 2015 and 2016 in this area,and the weighted average method was adopted.The energy balance method studies the characteristics of water and heat flux changes at different time scales.Provide scientific basis and reference data for the study of forest sustainable management in the region.The results show that:The energy balance closure of Larix gmelinii forest during the whole study period was 72%.The main factors affecting flux source region change are wind direction wind direction,the direction of source region and the area of source region are different in the steady state of different atmosphere;The characteristics of water-heat flux change are mainly affected by changes in meteorological factors such as net solar radiation,temperature,wind speed,and wind direction.The net solar radiation is blocked by clouds in continuous cloudy or rainy weather,and the radiation is difficult to reach the surface,resulting in a significant reduction in net radiation.The results of the energy closure test of Larix gmelinii ecosystem data are consistent.The source area of the flux at the daily scale is greater than the source area under cloudy conditions in the sunny states,and the area of the September flux source is larger than that of the August source area on the monthly scale.The area of flux source area in growing season is smaller than that in non-growing season source area under different atmospheric stability,and the location direction of flux footprint tends to be consistent with the wind direction.Since the net radiation is strengthened under clear conditions,the exchange of turbulent heat flux increases,so the overall area of the flux source area in sunny conditions is greater than that of cloudy weather.The area of the source area in the growing season and the non-growth season is different.This results in frequent turbulent exchanges between the ground and the gas,and thevertical diffusion of matter.The flux tower information comes from the flux tower.Close range,and small flux source area,the growth season source area is smaller than the non-growth season.When the atmosphere is in stable state,the vertical diffusion of turbulence is weak,and the horizontal movement is the main source area.The source area extends to the place within 0.6 kilometers of the upwind direction,and the area and spatial extent of the flux source area are measured.The main factors affecting the footprint distribution are atmospheric stability and wind speed.The period time of 2015 and 2016,in the typical weather,the leaves pine forest in the sunny state is mainly in heat exchange.Due to the absence of cloud cover in sunny days,the net radiation of the sun is strengthened,and the surface temperature increases rapidly,resulting in the heat exchange of the underlying surface turbulence.The characteristics of the monthly cumulative values of latent heat flux(LE)and sensible heat flux(H)in the growing season are the highest in August compared with other months in latent heat and sensible heat flux.From the daily mean value change of monthly-scale hydrothermal flux(latent heat flux,sensible heat flux),it was found that in mid-August,the latent heat flux reached the maximum in August.From this we can see that Larix gmelinii experienced intense water-heat exchange in August.During the study period of the growing season,the net radiation and temperature reached the maximum value.This demonstrated on a larger scale that during the growing season,the change of the water heat flux showed a unimodal trend,and in August it was dominated by latent heat exchange.