Utilization Of Livestock Dung Cake And Its Effects On Greenhouse Gas Emissiongs In Different Rangeland Regions Of Inner Mongolia

Since the industrial revolution,the large-scale development and utilization of fossil and land resources has increased the concentration of carbon dioxide(CO₂)and other greenhouse gases in the atmosphere,and induced the climate change characterized by global warming,which is one of the most serious environmental problems that human society faces.Much efforts have been made to reduce greenhouse gas emissions and increase the atmospheric CO₂sequestration to mitigate the globale climate change.The Chinese government has set the targets to chieve a“carbon peak”by 2030 and“carbon neutrality”by 2060.Greenhouse gas emissions in rangeland regions constitutes an important part of agricultural greenhouse gas emissions,including the emissions from soil,from animal intestinal fermentation,and from animal manure.The vast rangeland regions in China is an important barrier for ecological secutrity and a base for green pastoral produciton in northern China.Livestock dung cakes have been used as the energy materials in the traditional life of rangeland nomads.Dung cakes are an important organic matter with carbon sequestrated by plants and used by livestocks in rangeland ecosystems.The dung-cake burning leads to the direct CO₂emission,and shortens the cycling of the carbon and nutrients in rangeland ecosystems.In recent years,livestock dung cakes produced in rangeland regions have also been transported out of rangeland regions as organic fertilizer for use in arable lands.Many studies have been done on the greenhouse gas emissions from soil,animal intestinal fermentation,and animal manure,but hardly any studies have been done on the utilization of livestock dung cakes in rangeland regions,especially on their effects on greenhouse gas emissions,and on grassland ecosystem health.In the present study,we ingestigtated the produciton and utilization of livestock dung cakes in the pastoral areas in Inner Mongolia,and analysed their ecological effects on greenhouse gas emissions and ecosystem health.We did the ingestigation in five different rangeland regions in Inner Mongolia,that is,the meadow steppe region,typical steppe region,desert steppe region,sandy grassland region and desert region;and used pastoral household as the basic unit to collect the data of both natural and socioeconomic ecosystems.We aimed to understand the status and socail bahavour of dung-cake use in the region,and their implicaitons for rangeland ecosystem health and greenhouse gas emissions,which is important for the development of low-carbon pasotal systems.The specific research contents include:(1)the production and consumption(method and quantity)of livestock dung cakes,and their relationship with natural and socioeconomic factors;(2)the estimation of greenhouse gas emissions from the burning of livestock dung cake in different rangeland regions of Inner Mongolia;(3)the ecological and economic assessment of the livestock dung cakes used as a type of organic fertilizer;and(4)the willingness of herdsman household to sequester carbon and reduce emissions in pasture management,and its relationships with natural and socioeconomic condition.The main results are as follows:(1)The total annual production of dung cake in Inner Mongolia pastoral areas is 9.79 million tons,of which 29%were used as energy by herdsmen's households,40%for building livestock sheds,18%as organic fertilizer,and 13%are lost and discarded.The greenhouse gas emission effect of livestock dung-cake burning is about 3.76 million tons of CO₂equivalent,including 3.42 million tons of CO₂,11,000 tons of CH₄(equivalent to 308,000 tons of CO₂),and 103.5 tons of N₂O(equivalent to27,000 tons of CO₂).(2)The total livestock dung cakes used as biomass fuel by herdsman households in the pastoral areas of Inner Mongolia is about 2.8 million tons.The amont of the produced and burnt dung-cakes decreased with the increase of climate aridity,or with the decrease of the grassland productivity,in the region.Livestock dung cakes mainly came from sheep and goats(74.1%),less from cattle(25.7%)and camel(0.2%).The length of winter(i.e.,the number of days with the average daily temperature below 5?)determined the proportion of livestock dung cakes used as fuel energy in household energy consumption,instead of the availability of other energy sources such as coal,natural gas,and electricity.The length of winter did not only promote the burning of livestock dung cakes,but also affected herders management behavours;it encouraged housholds to raise more livestocks,thereby increasing the production of livestock dung cakes.(3)The total carbon(C)emissions form the burning of dung cakes by hersmen household in rangeland regions of Inner Mongolia were about 941,000 tons,and the total nitrogen(N)emissions were about44,000 tons.From meadow steppe region to desert region,the production and consumption(burning)of livestock dung cakes on the basis of land area(per ha)tended to decrease.The burning proportion of livestock dung cakes(i.e,the ratio of consumption to production)showed no clear change among rangeland regions along the gradient climatic atidity.Temperature is the main controlling factor for the burning and utilization rate of livestock dung cakes in herdsman household's energy consumption.(4)The average annual use of livestock dung cakes as organic fertilizer is about 1.81 million tons,accounting for 18%of the total dung cake production.The dung cake fertilizer was largely used in Tongliao and Ordos regions.Sheep dung is about 1.25 million tons,accounting for69%of the total,and the cattledung is about 0.56 million tons.The dung fertilizer was mainly used in the pastoral and agricultural mixed areas,especially the areas where pastoral production accounted for less than50%of the total agro-pastoral production,and were closer to the arable crop production areas.Considering the ecological benefits,the fertilizer use of the dung cake,could reduce the direct emission of 572,100 tons of carbon and 27,000 tons of nitrogen,compared to the dung-cake burning.This equivalent to a reduction of 2.283 million tons of CO₂equivalent(CO_2-eq),a saving of 58,100 tons of urea fertilizer,and the direct economic income(form saling the dung-cake)of 68.348 million yuan.(5)43% of the herdsman had no awareness of grassland carbon sink and carbon sequestration,and this level of awareness was much lower than that in forest areas of China;however,the herdsmen's willingness to participate in carbon sequestration and emission reduction(89%)was stronger than in other regions.