A Study On The Eco-efficiency Of Plantations In The Hilly Mountain Areas Of The Southern Edge Of The Sichuan Basin Based On A Carbon Source/sink Perspective ——Yibin And Luzhou As Examples

In the context of the integration of"carbon peaking"and"carbon neutrality"into the overall layout of ecological civilization construction,the harmonious integration of economic growth,low-carbon emission reduction and resource conservation in the plantation sector is a major challenge for agricultural development.In this context,there is great sigmiaficance for sustainable development of agriculture in the southern hilly areas of Sichuan Basin to incluse carbon source/sink effect into the assement index system of plantation eco-efficiency.Taking Yibin and Luzhou cities in the hilly mountainous region on the southern edge of the Sichuan Basin as the study area.IPCC inventory estimation method,carbon sequestration parameter estimation model,net carbon source/sink estimation model and super-efficient SBM model are used to estimate the carbon source/sink、carbon source/sink intensity and carbon source/sink perspective based on carbon source/sink for the last 20 years（1998-2017）in the region,plantation eco-efficiency was carried out;the influencing factors of plantation eco-efficiency was analysised by Tobit regression model,and corresponding countermeasures were proposed.The main conclusions are as follows.（1）Agricultural and plantation development characteristics:the agricultural structure of the region has been dominated by plantation（48.3%）and animal husbandry（43.7%）over the past 20 years;the average annual disposable income of farmers is RMB5,836,and it is showing an obvious upward trend.The area of arable land in the region is on a downward trend（down by 3.1%）,the arable land replanting index is on an upward trend（up by 33.9%）and fertiliser inputs are on an upward trend（up by 8.5%）.Pesticide inputs were on the rise（up 5.8%）.The structure of crop cultivation is:cereals（67.8%）,potatoes（17.1%）,oil crops（6.8%）,pulses（5.4%）,tobacco（2.3%）and sugar crops（0.5%）.There are clear regional differences in the development of agriculture and plantations in the region.（2）Carbon sources/sinks and their intensity characteristics:the average annual carbon sink in the region’s plantation industry over the past 20 years is 3.64×10~6t,and is on an upward trend（up by 11.8%）;the average carbon sink intensity is 7.96t/hm~2,and is on an upward trend（up by 15.31%）,with the largest carbon sink intensity in Jiangyang District（12.46t/hm~2）and the smallest in Gulin County（5.33t/hm~2）.Except for Junlian,Xuzhou and Longmatan,the carbon sink intensity of the plantation industry in all other counties is on an upward trend.The average annual carbon emission（carbon source）from the plantation industry is 9.1×10~5 t,showing an upward trend（up by 7.3%）;methane carbon emission from rice fields and carbon emission from farming inputs account for 64%and 36%of carbon emission from the plantation industry respectively,and the largest proportion of carbon emission from farming inputs is from chemical fertilizers（53.3%）.The average carbon emission intensity of the cultivation sector in the region is 1.99t/hm~2 and is on an upward trend（up by 10.61%）;the largest carbon emission intensity is in Jiangyang District（2.8t/hm~2）and the smallest in Junlian County（0.94t/hm~2）;except for Longmatan,Xuzhou and Jiang’an,the carbon emission intensity of the cultivation sector in all other counties and districts is on an upward trend.The overall carbon sink effect in the region over the past 20 years is that the average annual net carbon sink in the plantation sector is 2.73×10~6t,and is on an upward trend（up by 13.4%）.The average net carbon sink intensity of the whole region is 5.97t/hm~2 and is on an upward trend（the rate of increase is17.12%）;the net carbon sink intensity is the largest in Jiangyang District（9.66t/hm~2）and the smallest in Xuyong County（4.03t/hm~2）;except for Longmatan and Junlian,the net carbon sink intensity of all other counties and districts is on an obvious upward trend.（3）Characteristics of plantation eco-efficiency:In the past 20 years,the eco-efficiency of plantation in the region is at a low level（ρ=0.727,ρ<1）,and has not yet reached the effective eco-efficiency of plantation.Plantation eco-efficiency is on an upward trend（161%increase）,with plantation eco-efficiency falling before rising.Seven of the counties have high plantation eco-efficiency（Junlian,Longmatan,Luxian,Pingshan,Jiangyang,Xuzhou and Hejiang）,four counties have medium efficiency（Naxi,Gaoxian,Gongxian and Changning）and six counties have low efficiency（Gulin,Xuyong,Xingwen,Jiangan,Cuiping and Nanxi）;the regional differences in plantation eco-efficiency are obvious,with the southern mountainous areas of the region having higher overall plantation eco-efficiency than the northern hilly plains.The ecological efficiency of planting in the southern mountainous areas of the region is higher than that in the northern hilly plains.The redundancy of mechanical power inputs is the most important cause of the loss of planting eco-efficiency in the region,followed by the redundancy of labour inputs and fertiliser inputs.In terms of the typicality of redundancy of various plantation inputs and outputs,the largest redundancy rate in crop sown area is in Xuyong County（41.77%redundancy rate）,the most serious redundancy in labour input is in Changning County（45.61%redundancy rate）,the most serious redundancy in fertiliser input is in Xuyong County（50.96%redundancy rate）,the most serious redundancy in irrigation input is in Cui Ping District（36.76%redundancy rate）,and the most serious redundancy in mechanical power The most serious input redundancy rate was in Nanxi District（with a redundancy rate of 80.26%）,The largest reduction in carbon emissions is in Changning County（46.16%reduction）and the largest shortfall in total plantation output is in Jiang’an County（135%increase）;the main reasons for the loss of eco-efficiency in the plantation industry varied among counties and districts.（4）Factors affecting the ecological efficiency of the plantation industry and suggestions for improving it:the level of farmers’income,the proportion of the plantation industry in agriculture,the per capita electricity consumption of farmers,the scale level of the plantation industry and the net carbon sink of the plantation industry have a significant positive impact on the ecological efficiency of the plantation industry;the density of plantation machinery,the chemical situation of the plantation industry and the proportion of employees in the plantation industry have a significant negative impact on the ecological efficiency of the plantation industry.The future development of the region’s planting industry should reasonably use agricultural machinery and improve its efficiency;reduce the use of agricultural inputs and reduce agricultural carbon emissions;promote the development of low-carbon planting industry according to local conditions;and bring into play the demonstration role of areas with high ecological efficiency in planting industry.