Objective Fire is one of the major disasters affecting urban human settlement environment, which brings increasingly severe challenges to residents’ personal property and urban ecological benefits. In this paper, a comprehensive evaluation system of fire resistance of plant communities based on ground litter was constructed, which provides a new control idea for fire prevention and control and management of urban green space system, urban ecological safety and maintenance of green space health.

Method In this study, typical arbor communities and surface litter in the Shanghai Ring Green Belt were taken as research objects. Field survey was carried out to obtain data on mass characteristics and spatial distribution. Four indices, namely the average mass per unit area, coefficient of variation, skewness and kurtosis were used to describe mass characteristics of surface litter. Its spatial distribution was analyzed through range, fractal dimension, and Kriging interpolation. In addition, a calorimeter was used to obtain measured data such as calorific value, combustion time, temperature change, and incomplete combustion index, which were used to characterize the combustion characteristics of communities. Based on a total of 10 indices from the above three aspects, the CRITIC (criteria importance through intercriteria correlation) weight method was adopted to construct a comprehensive evaluation system for fire resistance of surface litter communities, and fire resistance of communities was ranked and analyzed.

Result (1) The average mass per unit area of ground litter in different communities varied greatly, ranging from 46.92 to 604.48 g/m². The mass dispersion degree of ground litter per unit area of each community was large, that is, there were a lot of fallen leaves deposited in some areas, and the mass was far above average value. The highest degree of dispersion was Osmanthus fragrans B community, and its coefficient of variation, skewness and kurtosis were the largest. (2) In terms of spatial distribution of ground litter, the comparative order of fire resistance was as follows: type I (fragmentation distribution) > type II (local centralized distribution) > type III (large area centralized distribution). (3) The heat value of ground litter was high, incomplete combustion index was small, burning time was long, temperature was moderate, and fire resistance was poor. Under same conditions, the ground litter of community was difficult to ignite. In general, fire resistance of conifer community was lower than that of broadleaved trees. (4) According to comprehensive evaluation system, the order of fire resistance of 21 communities from strong to weak was as follows: Celtis sinensis B community, Osmanthus fragrans B community, Firmiana simplex + Ligustrum lucidum community, Sapindus saponaria B community, Koelreuteria paniculata + Ligustrum lucidum community, Sapindus saponaria A community, Camphora septentrionalis community, Liquidambar formosana + Pterocarya stenoptera community, Elaeocarpus decipiens + Liriodendron chinense community, Celtis sinensis A community > Ginkgo biloba community, Ginkgo biloba + Camphora officinarum + Ligustrum lucidum community, Distylium racemosum + Populus euramericana ‘I-214’ community, Koelreuteria paniculata community, Ligustrum lucidum + Sapindus saponaria community, Zelkova serrata community, Taxodium distichum var. imbricatum community, Acer buergerianum community, Osmanthus fragrans A community, Ligustrum lucidum community, Taxodium distichum community.

Conclusion Communities with less surface litter, more fragmented distribution and weaker combustibility have stronger overall fire resistance.