Study On Carbon Effects Caused By Farmland Consolidation Based On Land Use And Engineering Characteristics

Currently,land utilization and global climate change has received an universal attention.Green and low-carbon development has become public consensus,it is necessary to conduct in-depth research on carbon effects of the land utilization.Land consolidation,especially farmland consolidation,has become an important way of large-scale land utilization,however,large-scale studies on regional effects based on the polygon of land consolidation are still rare.Using the polygon data of farmland consolidation project implemented in Guangdong,this study comprehensively analyzed the Guangdong farmland consolidation development,and the carbon effects of farmland consolidation from the perspective of land utilization characteristics and implementation feature.The main results are as follows.(1)The implement of farmland consolidation has influenced the carbon sink of cropland ecosystem from many aspects.The effects of farmland consolidation on carbon has been analyzed according to the land utilization characteristics and engineering feature.Farmland consolidation has its own distinctive features:1)land utilization.It influences the carbon composition of project areas through changing the land utilization patterns,thereby causing carbon effects of land utilization pattern transformation.Moreover,it influences the carbon sink ability in project areas,bringing the carbon effects of structure transition.2)Implementation feature.The implementation of farmland consolidation inevitably consumes materials and energy,forming carbon emission effect;meanwhile,ecological protection forest planting has significant carbon sink effect.The carbon effects of farmland consolidation include the indirect carbon effects caused by structure adjustment of land utilization and the change of land utilization patterns,as well as direct carbon effects brought by project implementation.The indirect carbon effects mainly occur in the project benefits developing period,which might be long-term effects and the direct carbon effects mainly take place during the implementation of projects.Utilization structure and utilization patterns are "transformation" and "gradual change" of internal ecosystem,and project implementation should be eternal factors that disturb the regional ecosystem,.Accounting systems are built accordingly in this study.(2)Macro analysis on the project implementation of farmland consolidation and the carbon source/carbon sink of cropland ecosystem in Guangdong is performed using statistical data.Since "the 11th Five-Year Plan",9,757 farmland consolidation projects has been implemented in Guangdong,most of them was conducted from 2006 to 2011.Land consolidation with land development project as the main type occupies absolutely overwhelming proportion,which is a distinct characteristic of farmland consolidation in Guangdong.These projects are mainly located in western Guangdong(e.g.Zhanjiang and Yangjiang)and northern Guangdong(e.g.Heyuan,Qingyuan,Shaoguan),which might be due to the policies of developing inefficient field and hilly land to supplement the cultivated land.With the continuous decline in agricultural carbon sink,the overall cropland ecosystem in Guangdong Province has shifted from "carbon source" to "carbon sink".(3)The overlay analysis of the farmland consolidation polygon and land utilization data in the past years showed that there were huge changes in land utilization structure.From 2009 to 2014,the transition of land utilization patterns took place in 103,900 hectares of land,among which 47.4 thousand hectares of garden soil was turned into cultivated land,44.5 thousand hectares of woodland was turned into cultivated land,8.5 thousand hectares of grassland was turned into cultivated land,276.48hectares of construction land was turned into cultivated land,1257.50hectares of water area and water conservancy facilities were turned into cultivated land,and 1156.22 hectares of unused land was turned into cultivated land,in addition,410.88 hectares of various types of land was changed into construction land due to the construction of country road,supporting facilities,etc.,thereby reducing 1,182,500 tons of carbon stock.It is found that the Gini coefficient decreased year by year from 2009 to 2013,and the variation of carbon stock became stable,while the entire difference decreased.The difference is largest in eastern Guangdong,followed by the Pearl River Delta,western Guangdong and northern Guangdong.Intra-regional difference is slightly greater than the inter-regional difference.(4)Through establishing CASA model to calculate the NPP variation of farmland consolidation project area in past years,and setting up the reference regions to remove the impact of eternal conditions such as weather,our study showed that there were 1,022 of polygons with NPP increase after land consolidation,accounting for 47.07%of the total 2,717 polygons.The regions with changes of polygon significant aggregated in the northern,eastern and western Guangdong.The study using polygons of 835 farmland consolidation projects showed that the NPP increased,expecially in Zhanjiang,which may be related to the scale effect of the arrangement of land consolidation project.(5)Carbon effects mechanism of various projects are different.The carbon effects of land leveling projects are mainly reflected as the carbon sources brought by the energies consumed by various mechanical equipment during the project implementation process;the implementation of farmland shelter project has the dual effect of carbon sources and carbon sinks.Calculation based on four selected farmland consolidation projects found that project implementation caused total carbon emission of 2,501.15 tons,among which the carbon emission caused by cement consumption occupied a large proportion(90.40%),which was 2260.96 tons,followed by diesel(12.96%)and steel(8.39%)products with the carbon emission of 324.03 tons and 209.74 tons,respectively.It is worth noting that the construction of protection forest brings greater carbon sink effect,accounting for 13.09%of the total carbon effects.Because water conservancy and irrigation requires the construction of head ditch,field ditch and other irrigation facilities,it has obviously influenced the cement consumption,with the carbon emission occupying 92.54%of the carbon source effect of total engineering implementation.Through estimating the carbon emission of farmland consolidation projects in Guangdong,it is found that the carbon emission amount is large,and the carbon emission effect of land consolidation project cannot be ignored.It is necessary to improve the planning programming,budgeting,final acceptance and other parts according to the different regions,thereby reducing the project implementation budget and enhancing project quality.In addition,we should consider the low-carbon index during the evaluation of farmland consolidation,which may promote low-carbon consumption and environmental protection.