Plain Ecotone Of Agriculture, Animal Husbandry, Subsystem Energy And Energy Analysis,

The Songnen grasslands dominated by Leymus chinensis provide fine pastures for grazing and hay production in the east of the north farming-pastoral zone of China. However, due to successive mowing and over-grazing, the grassland subsystem has experienced huge loss of matters and energy, causing ecosystem degradation successive. In addition, extensive cultivation in the farming subsystem makes resource use efficiency much lower. Both that has led to the damage of the ecosystem of the grassland and farming-pastoral zone. Land wind erosion and desertification, soil erosion, salinization and aridity are aggravated and the productivity is reducing. All of these greatly endanger the farming and animal husbandry production, and become the fatal threat of the environment.Aimed at the above-mentioned problems, the dissertation probed into the patterns and mechanisms of energy-emergy flows in the farming subsystem, the mowing subsystem and the grazing subsystem as case studies by means of multi-scale analyses including the community level, the ecosystem level and the region level. In order to find out the fundamental reasons of lower productivity and degenerated ecological environment, emergy based indices were applied to provide insights into the thermodynamic efficiency of the process, the quality of its output, and the interaction between the process and its surrounding environment. Then, focusing on its economic and ecologic load, the corresponding way out was also brought forward to insure long-term sustainability of the farming-pastoral ecosystem. Following are the main aspects in the studies:1. Based on measurements of biomass and calorific value, we studied energy fixation and conversion of the communities in three above-mentioned subsystems. The results of the stability analysis by means of compartment models were:The equilibrium state in the process of the energy flow was asymptotically stable, regulated by a negative feedback mechanism. The subsystems were in the state of energy accumulation. The time required for the net energy production and the net energy accumulation of the communities reaching the equilibrium state differed among the communities from different subsystems. The former needed about one year, whilst the latter varied from seven years to eleven years in the order the farming subsystem > the grazing subsystem> the mowing subsystem. The self-regulating abilities of the communities in the three subsystems were found to decline significantly with increasing intensity of human disturbances. For the available photosynthetic active radiation (PhAR), energy conversion efficiency (ECE) of the communities was 2.35% in the farming subsystem, 0.97% in the mowing subsystem, and 0.46% in the grazing subsystem.2. By means of emergy analysis, the inflows and outflows of energy and other resources evaluated on a common basis, i.e. the content of solar equivalent energy, were objectively measured in the case studies. Indices and ratios based on energy and emergy analyses were calculated and used to evaluate the behaviors of three subsystems. Their dependence upon the fractions of renewable and nonrenewable inputs as well as locally available versus purchased inputs from outside was stressed. The production of the subsystems that utilized natural resources rationally yet maintained ecological stability was necessary. Ecologically sound, yet productive, use of resources required indicators that assessed not only productive and economic factors, but also environmental impact and ecological effects. Thus, to study a production activity and its interaction with the environment, a new index system of synthetical evaluation, capable of considering ecological and economic aspects, was set up and applied to three subsystems to evaluate how sustainability. The results demonstrated that the mowing subsystem had the greatest synthetical benefits and potentialities of sustainable development. More inflows of industrial subsidiary emergy and high emergy-contained technology into the mowing subsystem shoul...