The Research On The Response Of The NPP To Human Activities In The Northwestern Zhejiang Based On Remote Sensing And Ecological Model

Climate warming leads to changes in precipitation patterns and extreme weather events in northwestern of Zhejiang province.Some studies have found that the main factor leading climate warming since the 1950s was the increase in carbon dioxide concentrations.The changes in land use types,such as deforestation,urban expansion,were one of the main causes of carbon dioxide concentrations increase.Forest ecosystems are major reserves for terrestrial carbon,and play an important role in the global carbon cycle.Forest ecosystems are also major components of global primary production,thereby slowing the rise of atmospheric carbon dioxide concentrations.In China,long-term and persistent human disturbances,such as the changes in land use types,have simultaneously altered the biodiversity and stability of forest ecosystems,thereby degrading the carbon fixation capacity of forest ecosystems.The establishment of nature reserves and zoning management is the best way to protect the biodiversity of ecosystems,and maintain ecological security.Net primary production(NPP)can reflect the exchange of carbon dioxide between vegetation and environment,and the carbon footprint.Therefore,it is an important indicator of the carbon fixation capacity of forest ecosystems.However,there has been no research on the efectiveness of zoning management on NPP.In Anji,the area of forest is degrading at a rapid rate because of the swift economic growth,and the area of the Moso bamboo(Phyllostachys pubescens)forest grows rapidly over the last 31 years.Therefore,an appreciation of whether NPP has increased or decreased in Anji,and the influence of the urbanization and upward spread of Moso bamboo forest on NPP is urgently required.To date the impact of the urbanization and upward spread of Moso bamboo forest on NPP in Anji over the last 31 years has not been estimated.Based on the background mentioned above,in this study:(1)We used the Triplex-Flux model to simulate the 30 min NPP in Moso bamboo forest ecosystem in Anji,and analyzed the impact of the On and Off-year management of Moso bamboo forest on NPP from daily and monthly scales.The results will provide theoretical guidance for Moso bamboo forest management and forest ecosystem restoration.(2)We used the CASA model to estimate the monthly NPP in the Tianmu Mountain Nature Reserve during the period 1984?2014,explored the temporal and spatial changes of NPP in three zones of the nature reserve,and analyzed the effectiveness of zoning management on NPP.The results will provide scientific evidence for the study on the relationship between nature conservation and ecosystem service functions,and provide theoretical guidance for zoning management and ecosystem restoration.(3)Based on the simulated NPP,meteorological data,and NDVI in the Tianmu Mountain Nature Reserve and Anji,we established the NPPpot models for the broadleaf forest,needle leaf forest,Moso bamboo forest,agricultural land,urban land,and water in Anji.The results will provide theoretical guidance for accurate estimation of NPPpot,and provide data support for the assessment of regional potential production.Then,we established the human activity disturbance index(HADI)to explore the impact of the land-use and land-cover change on NPP.The results will provide scientific evidence for quantitative description of the impact of human activities on NPP.Summarised the research results,the mainly conclusions shown as:(1)Based on the flux tower and MODIS MOD15A2H 500 m LAI data,the Triplex-Flux model is paraneterized and validated.The results show that the simulated NPP was largely consistent with the observed NPP(R2>0.85,p<0.01).This means that the Triplex-Flux model is suitable for NPP estimation in the Tianmu Mountain Nature Reserve and Anji.We also used the CASA model to estimate the NPP,and validated the simulated NPP.The results show that the simulated NPP was largely consistent with the observed NPP and the simulated NPP by Triplex-Flux model(R2>0.39,p<0.01).This means that the CASA model is suitable for NPP estimation in the Tianmu Mountain Nature Reserve and Anji.(2)Based on the simulated NPP by Triplex-Flux model,we analyzed the impact of the On and Off-year management of Moso bamboo forest on NPP from daily and monthly scales.On the monthly time scale,the NPP were influenced by the atmospheric temperature(Ta),temperature at the soil depth of 5cm(Ts),photosynthetic photon flux density(PPFD),atmospheric CO2 concentration(Ca),vapor pressure deficit(VPD),leaf area index(LAI),and the On and Off-year management of Moso bamboo forest.Overall,the NPP in the On-year(NPPon)were higher than those in the Off-year(NPPoff).The NPPon were higher than NPPoff throughout the Wintering period(December,January,and February)and bamboo whip budding period(March?May).During the growth period(June?September),the NPPon were lower than NPPoff in June and July,however,the NPPon were higher than NPPoff in August.The NPPon in the bamboo harvest period(October and November)were lower than NPPoff in the bamboo shoots hatching period(October and November).On the daily time scale,the NPPon were higher than NPPoff throughout the Wintering and bamboo whip budding period,while,the NPPon were lower than the NPPoff during the growth period,the NPPon in the bamboo harvest period were lower than NPPoff in the bamboo shoots hatching period.The carbon use efficiency(CUE)in the On-year(CUEon)were higher than those in the Off-year(CUEoff),and the annual averaged CUE during the period 2011?2014 were 0.55,0.52,0.53,and 0.52 year-1.The CUEon were higher than CUEoir throughout the Wintering and bamboo whip budding period,During the growth period,the CUEon were lower than CUEoff in June and July,however,the CUEon were higher than CUEoff in August,the CUEon in the bamboo harvest period were lower than CUEoff in the bamboo shoots hatching period.(3)Based on the simulated NPP by CASA model,we analyzed the effectiveness of zoning management on NPP in the Tianmu Mountain Nature Reserve.The total annual averaged NPP during the period 1984-2014 was 3.07 × 1010 g C year-1,and the annual averaged NPP per unit area was 707.68 g C m-2 year-1.The largest annual mean NPP appeared in the moso bamboo forest(739.77)and evergreen broadleaf forest(738.97),followed by the deciduous broadleaf forest(694.34),with the needle leaf forest having the smallest annual mean NPP(673.23).In general,the NPP values in the core zone were higher than those in the buffer zone and experimental zone during the period 1984-2014.The largest averaged annual NPP per unit appeared in the core zone(719.83),followed by the buffer zone(710.91),with the experimental zone having the smallest averaged annual NPP per unit(705.6).At the p<0.1 level,there was no region where NPP had decreased significantly in the core zone and buffer zone,and there was only 0.23%of the total area in the experimental zone where NPP had decreased significantly.The area of the regions where NPP had decreased significantly in the experimental zone was 8.04 ha.At the p<0.05 level,there was no area where NPP had decreased significantly in the core zone,buffer zone and experimental zone.The results show that the zoning management on NPP was effective in the Tianmu Mountain Nature Reserve.(4)Based on the meteorological data,NDVI,NPP of the broadleaf forest,needle leaf forest,and Moso bamboo forest in the Tianmu Mountain Nature Reserve where the land cover types had not changed over the last 31 years,we established and validated the NPPpot model for the 3 different forest types.The results show that the simulated NPPpot were largely consistent with the simulated NPP by CASA model(R2>0.86,p<0.01).This means that the NPPpot models are suitable for NPPpot estimation in Anji.In general,the NPPpot values in the Moso bamboo forest were higher than those in the other 3 forest types.The annual averaged NPPpot per unit area was 771.39 g C m-2 year 1.The largest annual mean NPPpot appeared in the moso bamboo forest(883.28 g C m-2 year-1),followed by the broadleaf forest(859.09 g C m-2 year-1),with the needle leaf forest having the smallest annual mean NPPpot(700.07 g C m-2 year-1).The annual averaged NPPact per unit area was 751.23 g C m-2 year-1.The largest annual mean NPPact appeared in the moso bamboo forest(821.88),followed by the broadleaf forest(760.79),with the needle leaf forest having the smallest annual mean NPPact(726.46).(5)Based on the simulated NPPpot and NPPact,we estimated the HANPPlucc and HADI in Anji in 2014.Affected by human activities,the HANPPlucc in Anji is 1.21×1011 g C year-1,and the HANPPlucc per unit area was 64.26 g C m-2 year-1.The degradation of the broadleaf forest and needle leaf forest is the main reason for the decrease of NPP in Anji,which resulted in a decrease of 3.58%and 2.40%in NPP.However,the upward spread of Moso bamboo forest increased the NPP of 3.32x1010 g C year-1.Overall,due to the high forest coverage rate in Anji,the averaged HADI was low(13.08%).