Observation And Research Of Water And Carbon Fluxes On The Farm Scale

In the context of global warming,the Qinghai-Tibet Plateau,as one of the most sensitive and vulnerable areas of global climate change,has attracted the attention of academia and society in the relationship between vegetation and land-climate.The Yellow River source region is located in the northeast of the Qinghai-Tibet plateau,with a high altitude and a large drop.There are complex topography,bad weather,poor soil,and frequent natural disaster.The study on the response of the change of vegetation cover to human activities and climate change in the region provides important theoretical support for the study of ecological sustainable development and global climate change in the region.This study choose the Yellow River source region as the study area,the China regional high space-time resolution ground meteorological elements drive data set and GIMM/NDVI dataset and the current situation of 1:100000 scale land use remote sensing monitoring database as the main data,The land use data,vegetation NDVI data and meteorological factor data sets of the Yellow River source area from 1982 to 2013 were obtained.From the year,season,and month scale analysis climate change and human activities on the Yellow River source area of land use and vegetation index with spatial and temporal variation characteristics and its driving factors.The main conclusions of the paper are as follows:(1)The temperature and precipitation factors in the data set are well applicable to the Yellow River source by comparing the temperature and precipitation data of the meteorological stations in seven countries.Average annual,summer and winter average temperature and precipitation are on the rise.The Yellow River source region average annual temperature of-2.0?,the summer years of average temperature of 7.6? and the years of average temperature of-11.8? in winter.The average annual precipitation of the region is 506.6 mm,while the average summer rainfall is 285.6 mm,and the average precipitation in winter is 11.39 mm.The temperature and precipitation showed a single peak type in a year,with the highest temperature in July,and the lowest in January and December.The temperature fluctuation of winter is greater than summer,but the fluctuation range of winter precipitation is less than summer precipitation.The average surface precipitation of spring,summer,autumn and winter was 97.25 mm,285.65 mm,110.84 mm and 11.94mm respectively,accounting for 19.2%,56.4%,22.1%and 2.4%respectively.The annual average of NDVI in the Yellow River source region and the various seasons varied from year to year,with the average annual average of 0.3246.The overall trend was slightly higher,but the upward trend was smaller and the slope was only 0.3%/10a.During the season,the average annual mean of NDVI in the Yellow River source region was 0.2108,0.5938,0.3502 and 0.1438,respectively,in the summer>autumn>spring>winter.Rise rate spring>winter>autumn>summer,respectively 0.5%/10a,0.4%/10a,0.3%/10a and 0.2%/10a.NDVI has a single peak in a year,with the highest temperature in August,January to April and November to December the lowest temperature.NDVI fluctuates less in winter than in summer NDVI.(2)By the Mann-Kendall non-parametric statistical tests,the annual average temperature of the Yellow River source region and the abrupt temperature of winter temperature occurred around 1998,and the summer temperature mutation point occurred around 1994.The annual precipitation change occurred around 2004.The abrupt change in rainfall in summer occurred around 2005.The abrupt change of precipitation in winter occurred around 1999.The average NDVI mutation point in the Yellow River source region occurred around 1983,and the average NDVI mutation point occurred around 1984,and the average winter NDVI didn't mutate in winter.Through the R/S analysis,the annual average,summer average and winter average temperature and precipitation sequence of the Yellow River source area are highly persistent,while the annual average NDVI,summer average NDVI and winter average NDVI sequence have weaker persistence.(3)Through Morlet wavelet analysis,the first main cycle of temperature change in the Yellow River source region is 22 years,and the second main cycle is 6 years.The first main cycle of summer temperature change is 22 years,and the second main cycle is 28 years.The first main cycle of temperature change in winter is 22 years,and the second main cycle is 28 years.The first main cycle of annual precipitation change in the Yellow River source region is 28 years,and the second main cycle is 21 years,the first main cycle of summer precipitation change in the Yellow River source region is 21 years,and the second main cycle is 19 years.The first main cycle of winter precipitation change in the Yellow River source region is 5 years,and the second main cycle is 10 years.The first main cycle of the annual average NDVI change in the Yellow River source region is 28 years,and the second main cycle is 23 years.The first main cycle of the average NDVI change in summer is 28 years,and the second main cycle is 22 years.The first main cycle of the average NDVI change in winter is 28 years,and the second main cycle is 14 years.(4)The spatial distribution of annual temperature,precipitation,NDVI,and spatial distribution of the trend over the past 32 years is calculated through ArcGIS and IDL platform.The spatial distribution of temperature is mainly affected by altitude,and the average temperature is lower in high-altitude areas.The variation range of the average precipitation in the Yellow River source region was 234.6?839.2 mm,which was in the southeast of the source region and the distribution in the northwest.The average precipitation in spring,summer,autumn and winter were 38.8?186.35 mm,144.28?421.45 mm,32.86?204.88 mm and 2.94?25.96 mm,respectively.In the annual and seasonal scales,the temperature distribution trend of the Yellow River source region is similar.Most of the temperature is on the uptrend,and the most uptrend is in the western and central parts of the source region.The spatial distribution of precipitation in four seasons has high similarity.The spatial distribution of precipitation trend in the Yellow River source region is similar,and the rising trend is mainly distributed in the high altitude in the west and middle of the source region.The downward trend is mainly distributed in the low-altitude areas of the southeastern and middle parts of the region.The average NDVI was 0.3246 on the Yellow River source region,and the range of NDVI was-0.0395-0.6140.The average NDVI range in spring,summer,autumn and winter is-0.0656?0.4815,0.0006?0.874,-0.0306?0.7 and-0.069?0.507.The spatial distribution of NDVI is mainly affected by the latitude and topography,and the spatial distribution of NDVI it is similar to the spatial distribution of precipitation,which is less in the southeastern part of the source area and less in the northwest.In the change of annual scale,most of the spatial distribution of NDVI in the Yellow River source region has increased trend,and the variation range is mainly concentrated at-1.659%/10 a?1.659%/10a,and average 0.28%/10a.In the winter NDVI change trend,most of the regions show an increasing trend,with the variation range mainly concentrated at-2%/10a?2.5%/10a,average 0.3%/10a.(5)In the past three decades,the land use type area has changed little and more stable.Each period is dominated by two types of land use,such as grass and unused land,which together account for over 90%of the total area of the Yellow River.From 1985 to 1995,the area of cultivated land and grassland increased,and the remaining types decreased.From 1995 to 2005,the land use trend reversed from 1985 to 1995.And from 2005 to 2015,the land use has not changed Over the past three decades,various land use types have changed little over the years.The vast majority of cultivated land is in the following areas of 3500m,and has been increasing slightly for many years.The forest land is more than 3500?4000m;The grass is more than 50%in each elevation,in which more than 70%of the area is more than 3500m;waters in the 3000m below the regional water area has an upward trend;urban and rural areas,industrial and mining,residential land distribution in 4000m below;The unutilized areas are evenly distributed on each elevation,and the area has changed little over the years..(6)In summer,NDVI averaged a multi-year average of 0.5504,0.7096,0.6045,0.4407,0.4407,0.4767 and 0.5230 respectively in cultivated land,woodland,grassland,water,industrial and mining land and unused land.Forest land>grassland>arable land>unused land>industrial and mining land>waters.The rate of change of NDVI was 0.4%/10 a,the change rate of NDVI was-0.03%/10 a,and the change rate of NDVI was 0.2%/10 a,cultivated land>grassland>forest land.NDVI of each land use type is the highest in 3500?4000m area.At yearly scale NDVI and precipitation are weakly correlated while NDVI and temperature are medium positive correlation.At monthly scale NDVI response to temperature and precipitation are positive correlation,NDVI peak value of temperature and precipitation have a month or so,the lagging behind of DNVI and precipitation have good linear relation,DNVI good quadratic function relation with temperature changes.NDVI and precipitation and temperature show a certain degree of noose,in the direction of counterclockwise.