Research on LIM-based simulation of carbon stock baseline scenario in urban trees: taking the green space of a university in Beijing as an example

  Objective  Faced with the problem that the research on urban landscape tree carbon sink lacks refined small-scale research methods, a technical method based on Landscape Information Model (LIM) was proposed to reverse three-dimensional reconstruction of landscape trees at a specific time point in the urban environment. By simulating the growth of plants at a certain time, the corresponding biomass and carbon storage were obtained, so as to describe the baseline scenario of carbon storage.

  Method  The steps of the experiment to verify this method included: the harvesting and proceeding of the point clouds; the construction of the LIM model; and the calculation and evaluation of the carbon stock of the trees. The objects of the experiment were the 19 selected Sophora japonica standing in rows on both sides of the lawn on the university campus in Beijing. The point clouds harvesting was achieved by terrestrial laser scanning (TLS). The proceeding aimed to segment the individual tree and reduce the density of the points. LIM model construction included 3D digital model construction and growth simulation of individual scholar tree and a group of 19 scholar trees with GIS location. The growth simulation under baseline scenario was also included. The calculation and evaluation of the carbon stock of the trees were realized by applying an allometric growth equation under baseline scenario.

  Result  The LIM model of individual scholar tree was constructed. It was with a 3D digital model integrating the crown and roots and the optimal growth curve, that was from the reconstruction of point clouds. The LIM model was applied to simulate the dynamic growth of the individual scholar tree at the age of 8, 10, 20, 30, 40, 50 years old. The results stated that under the baseline scenario, from seedling emergence to the 50th year of growth, there was a net increase of 1 396.87 kg and an annual increase of 33.261 kg of carbon stock. Such method of LIM model construction was applied to the 19 scholar trees with different ages on campus. It was realized to simulate their individual and colonial biomass and carbon stock in 10, 20, 30, 40, 50 years. The baseline scenario of their carbon stock was described. The current average carbon stock of the 19 scholar trees was 115.33 kg. The current total carbon stock was 2 191.27 kg.

  Conclusion  The results state that it is feasible to apply LIM-based methods to research on the refined small-scale carbon stock of the existing urban trees. The numerical simulation of carbon stock in the LIM model is coupled with the spatial geometry model of plant growth. It is promising to have such a model coupling the carbon calculation and evaluation to much richer application scenarios, such as urban habitat protection, planning and design, project construction, operation and maintenance, asset management, and spatial governance.