Studies On Forest Carbon Stock In Hani Terraces Watershed

At present,the earth is experiencing a climate change whose main feature is warming,which has not only been a crisis and challenge that all countries in the world need to handle,but also brings huge pressures of carbon emissions reduction to China.Forests occupied the most of the epigeosphere,giving play to the unique role of carbon sequestration.And it is the vital realization route for the "Carbon-Peak and CarbonNeutrality" Target.Therefore,forest carbon stock became a hotspot for governments and scientists.However,there were few of nature reserves and cultural heritage sites between masses of existing studies on forest carbon stock from the scale of nations,provinces,and cities.Hani Rice Terraced Ecosystem in Honghe Prefecture,Yunnan,China,has been identified as the Globally Important Agricultural Heritage System(GIAHS)on June 14th of 2010,which was launched by the Food and Agriculture Organization of the United Nations(FAO),what’s more,it has also been listed into the World Cultural Heritage List by United Nations Educational,Scientific and Culture Organization(UNESCO)on June 22th of 2013.Thus,Hani Rice Terraced Ecosystem becomes a double heritage which tends to be rare around the world.As the brainchild of local ethnic minorities like Hani and Yi,Hani Rice Terraced Ecosystem explained why this system could be considered as a representative of low-carbon,ecology and sustainable.Therefore,it need to be taken seriously to know what important roles Hani Rice Terraced Ecosystem plays in terms of carbon sink and to interpret the ecological wisdom of local ethnic groups in managing the system with scientific data.In view of the fact that the researches for forest carbon storage and its spatial distribution of Hani Rice Terraced Ecosystem have not been reported,which is a research gap in the field.The present research investigated 95 arboreal quadrats of 20 m × 20 m randomly in the watershed,which belongs to key districts of Hani Rice Terraced Ecosystem in Yuanyang County,Honghe County,Liichun County and Jinping County.The Non-parametric Regression Models based on Machine Learning were constructed with Landsat 8 OLI remote sensing image to estimate forest carbon storage of Hani terraces watershed and its spatial pattern was drawn.The ecological wisdom in local was collected by the ethnobotanical survey to study the positive effect on forest carbon sequestration.The following are primary research contents and results:1.There were totally 63 corresponding characteristic parameters from Landsat 8 OLI remote sensing image that were extracted,such as texture feature,vegetation index,greenness component amd wetness component,etc.And the importance analysis of characteristic parameters based on Random Forest was used to analyze and select the features with high correlation with forest carbon stock.As a result,B4_Mean,SAVI,NDVI,Greenness,RVI,B5_Second Moment,B2_Variance and GNDVI were further selected for the implementation of subsequent carbon stock inversion models.2.Three Machine-Learning algorithms of Random Forest(RF),extreme Gradient Boosting(XGboost)and Bootstrap aggregating(Bagging)were selected to establish the forest carbon storage inversion models in Hani terraces watershed.Through the comparison and evaluation for the accuracy of three models,XGboost model with the highest accuracy was selected to be the most applicable to the forest carbon storage inversion in the study area,whose R2 was 0.97,fitting RMAE and MAE were 0.29 and 0.23 respectively,predicted RMSE was 1.08 as well.3.The forest carbon storage estimation and analysis of Hani terraces watershed were completed by XGboost model.The total forest carbon stock in the watershed was 25040219.87 tC.The forest carbon in the watershed of Yuanyang County had the highest storage of 7493131.052 tC and the watershed of Adebo District in Jinping County had the lowest of 3573605.226 tC.As far as forest carbon density was concerned,all of the watershed gained over 60 tC/hm2.the highest forest carbon density in the watershed of Maandi District in Jinping County was 78.957 tC/hm2 and the lowest was 60.138 tC/hm2 in the watershed of Honghe County.4.The result of estimating the forest carbon storage and mapping its spatial pattern of Hani terraces watershed by the optimal XGboost model was in line with its land use pattern.The overall forest coverage in the study area has been more than 60%,and the majority of unit carbon stock of forests were mostly between 2.4 to 5.2 tC.The spatial distribution of forest carbon stock in the watershed was closely associated with the regional terrain,land type,development and planning,whose characteristic was consistent with the integrated "forest-village-terraceriver" structure of Hani Rice Terraced Ecosystem,illustrating that forests of Hani terraces watershed has not only provided sufficient water,but played a significant part in carbon sink.5.The ecological wisdom of people in Hani terraces watershed took positive effect on forest carbon stock.First and foremost,the Spatial vertical distribution characteristic of the "forest-village-terrace-river"structure acted an important role in maintenance water and soil,and system stability.Secondly,the natural water circulation achieved efficient utilization of water resources through the complex material cycle and energy flow,which provides a prerequisite for sustainable development of forest carbon storage.What’s more,the relevant traditional knowledge like sacred forest culture,water separation by cutting wood and constructing ditches,promoted the effective protection and sustainable management of forest resources,providing an important guarantee for forest carbon sink.The innovative point of this research mainly lies in its first time for both study area and research work of Hani Rice Terraced Ecosystem.First and foremost,all of the key terraced districts in Yuanyang County,Honghe County,Luchun County and Jinping County were taken into the study,which can provide significant reference for future research.In addition,this was the first time to study and report the estimation and spatial pattern of existing carbon storage of forests in Hani terraces watershed,facilitating to learn about how much impacts this system has been exerting on climate change mitigation,and serving as primary database for the design and implementation of forest carbon-sink market in local.Finally,the influence of the ecological wisdom in Hani terraces watershed on forest carbon sequestration was discussed,primarily for its"forest-village-terrace-river" structure,utilization system of water,protection and management for forests,and the relevant traditional knowledge,providing reference for increasing forest carbon sink and green development transformation from perspective of nature.