| With the acceleration of urbanization,urban ecosystems are redesigned and rebuilt to meet the needs of urban infrastructure,becoming fragile and sensitive.To fully understand the degree of disturbance of human society to the urban ecosystem,researchers urgently need an evaluation method that can fully reflect the dynamic changes of the ecosystem and easy to carry out and operate.By monitoring and evaluating the biological sound of the acoustic community,soundscape ecology provides a new perspective for explaining the ecosystem changes caused by human disturbance.However,the ecological analysis of soundscape in urban areas is often disturbed by artificial sound elements thus cannot be widely carried out.To have a more comprehensive understanding of the dynamic changes of biological sound in the urban forest area,this study selected the biological sound in the urban forest of Yangtaishan in Shenzhen as the research object,starting from the temporal and spatial distribution pattern and urban space and vegetation factors.The purpose of this study is to solve four main problems in urban forest areas:(1)how to avoid the interference of artificial sound produced by human activities to the study of biological sound;(2)what are the characteristics of the temporal and spatial distribution pattern of the biological acoustic activity of the acoustic community;(3)what is the influence of urban space on the dynamic change of biological sound;(4)what is the relationship between bioacoustic activity and different structural factors of urban forest vegetation.Herein,this study used the combination of array and scattered microphone layout to monitor the dynamic changes of biological sound in Yangtaishan urban forest marginal and inner area,respectively.The array layout consisted of 30 portable recording devices,and a 5 × 6 microphone array was used to solve the relationship between the complex urban spatial pattern and the dynamic changes of bioacoustics.The scattered layout was composed of 10 fixed recording equipment to solve the relationship between community structure characteristics and bioacoustic dynamic changes of the typical subtropical evergreen broad-leaved forest.In order to evaluate the dynamic changes of biological sound in the urban area more accurately,this study classified the sound and did statistics of six kinds of sound scene elements(bird song,insect sound,bird sound,artificial biological sound,artificial sound,and blank sound)based on artificial intelligence algorithm,and on the premise of eliminating the interference of artificial sound elements.Normalized sound index(NDSI),acoustic diversity index(ADI),and power spectral density(PSD)were used to quantitatively analyze the dominance,diversity,and spectral composition of bioacoustics.The results showed that:(1)the urban forest provided an important acoustic space for the acoustic community and created the necessary sound place for the urban biological community.Comparing the proportion of sound landscape elements in different urban forest environments,it was found that the inner area had more biological sound elements(inner area 72.51%,marginal area 61.10%),fewer artificial sound elements(inner area 1.14%,staggering area 14.60%)and artificial biological production(inner area 0.47%,marginal area 9.85%).Simultaneously,the proportion of blank sound in the inner area(26.35%)was slightly higher than that in the interlaced area(24.28%).The results showed that the intensity of biological acoustic activity in the inner area was higher than that in the marginal area.Simultaneously,the artificial interference was weakened,and the overall acoustic environment was more suitable for the biological acoustic activity.(2)Acoustic communities in urban forest environments shared limited acoustic spatial resources in the frequency domain,activity time,and space.The analysis of bioacoustic characteristics and diurnal variation showed that the main frequencies of birdsong and insect singing in the region are concentrated between 2-4k Hz and 4-7k Hz,respectively,and had the relationship of "one decline and the other," indicating the layered utilization of acoustic space among different acoustic communities.The bird community tried to avoid artificial sound activities in the study area by adjusting the time and place of sound production.(3)NDSI and ADI indices were suitable for quantifying the dynamic changes of acoustic communities in urban forest areas and evaluated the dynamic characteristics of acoustic communities in terms of the dominance and diversity of biological sound in acoustic space,respectively.Simultaneously,the research results showed that the ADI index was sensitive to the change of artificial sound,so it is necessary to calculate after removing the artificial sound elements.(4)The responses of bioacoustic dominance and diversity to urban spatial elements were different in different seasons and affected by spatial and vegetation factors,respectively.The influence of urban spatial structure on bird songs was mainly concentrated in spring.In contrast,that of insects was concentrated in summer,which reflected the differences in the utilization of spatial structure among different acoustic communities.Bioacoustic dominance was related to spatial factors such as forest edge distance,trail distance,and trunk road distance.In contrast,diversity was related to vegetation factors such as leaf area index,leaf height diversity,and canopy openness.(5)Normalized vegetation index,tree height diversity,and canopy vegetation density were the internal factors affecting the dynamic change of urban forest vegetation structure.Vegetation structure factors had the highest explanatory power to birdsong in spring and insect song in summer.Simultaneously,vegetation normalization index and tree height diversity positively affected bioacoustic dominance in each season.In contrast,canopy vegetation density showed a negative effect on bioacoustic diversity in each season.The difference between vegetation structure and biological sound dominance and diversity showed that different types of sound production patterns of acoustic communities had different dependence on the spatial structure of vegetation.This study showed the possibility and specific scheme of using acoustic methods to monitor and evaluate the dynamics of acoustic communities in urban forest areas.This paper reveals the temporal and spatial distribution pattern of the acoustic community under the background of the urban forest and its relationship with complex urban space and vegetation structure factors,which provided a new perspective for studying urban forest biodiversity in the future.It also provided new reference data for urban forest planning and management. |
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