| As an important part of urban ecosystem,urban green space is a major habitat for birds and other animals,and is important for the protection of urban biodiversity.However,traditional parks are usually characterized by plant community of simple structure,which has limited effect on promoting biodiversity.Near-natural greenspace is based on the thought of learning from nature.In the local vegetation characteristics for reference,following the rules of the natural forest community succession,near-natural community is an artificial community with reasonable structure,and plays an important role in promoting urban green space community stability and rich biodiversity.However,how to balance human needs and biodiversity protection has become the focus and difficulty of urban green space development.At the same time,due to the lack of successful demonstration samples,the systematic research on the near-natural greenspace and their biodiversity in the urban center is still not enough.The 2035 Plan of Beijing clearly puts forward the strategy of “building greenspace in abandoned space,allowing forest to enter the city”.The small green space with multi-layered,diverse age and mixed community structure dominated by native plants is constructed,and the urban forest green space with small area has been successfully built in the central city.It is generally believed that biodiversity will improve with the increase of green space area.However,for small green space with an area of less than 5 hectares,can the diversity including plant,insect and bird be effectively improved because of its near-natural community characteristics?This study conducted investigation around this core question,selecting two near-natural greenspace,Guangyanggu Urban Forest and Xinjiekou Urban Forest as the main research objects,which were constructed in Beijing xicheng district since 2017.And four traditional community gardens of the similar area and locations were selected as contrast,to identify the diversity characteristics of the near-natural greenspace in the aspects of plants,birds,and insects.We also explored the influence of near-natural greenspace plant community characteristics on bird and insect diversity,comparing the bird and insect group differences and community stability in different habitat types of near-natural greenspace.On the basis of this,this paper puts forward the improvement strategy of near-natural greenspace and the application method of near-natural community to balance the needs of human activities and biodiversity conservation.The main research results are as follows:(1)A total of 130 species of 108 genera and 47 families of vascular plants were recorded in 6sample greenspace,among which 92 species of 79 genera and 31 families were recorded in near-natural greenspace.The ratio of tree,shrub and grass species in the near natural garden was 1:1.6:2.3,and that in the common garden was 1:0.6:0.5.The richness and diversity index of shrub layer and herb layer in the near-natural greenspace were higher than those in the control group,but there was no significant difference in evenness.Compared with the control group,the dominant families in the near-natural greenspace are more similar to those in the mountainous areas of Beijing.The abundance of bird-feeding and nectar plants in near-natural greenspace was higher than that in common gardens,but the proportion of native plants and the abundance of bird-feeding and nectar plants were not significantly different from that in control group.The height,DBH and crown breadth of trees are significantly lower than that of ordinary gardens,while the complexity of vertical structure of cummunities in near-natural greenspace is significantly higher than that of general gardens.(2)A total of 2131 insects belonging to 173 species,81 families and 12 orders were recorded in 6urban greenlands,including 1267 insects belonging to 135 species,76 families and 11 orders in near-natural greenspace.The insect species richness and diversity of near-natural greenspace were significantly higher than those of control group.The insect community could be divided into three subcommunities(enemies,herbivorous insects,neutral insects)and seven functional groups(leaf-eating,flower-sprout eating,stinger-feeding,stem borer,predator,parasitic and neutral insects).In near-natural greenspace,the abundance and relative abundance of enemies and flower visitors are higher than those in control group.Among the characteristic factors of plant community,the richness of herbs was significantly positively with the abundance of insects,the richness of nectar plants,the proportion of native plants were significantly positively correlated with insect community diversity.The results of variance partitioning analysis showed that native plants and nectar plants had more influence on insect diversity than plant richness.In conclusion,compared with the control group,the near-natural greenspace have a significant advantage in insect diversity,which is mainly reflected in the enemies and flower visiting insects.Taraxacum mongolicum,Echinacea purpurea,Cosmos bipinnatus,Nepeta cataria have a significant attracting effect on natural enemy insects.The high plant diversity,abundant nectar plants and native plants in the near-natural greenspace plant community provide favorable conditions for the improvement of insect diversity.(3)49 species,21 families and 6 orders of birds were recorded in 6 urban parks,and 37 species were discovered in near-natural greenspace.The bird richness and diversity of the near-natural greenspace were significantly higher than that of control group,but the evenness index had no significant difference.Based on bird feeding habit and using way in the plant habitat,birds can be divided into eight groups.The abundance and relative abundance of carnivorous and insect-eating groups in the near natural gardens are higher than those in the common gardens.Among the characteristic factors of plant community,shrub layer richness had positive effects on abundance of birds,herbaceous layer richness had positive effects on bird community diversity,foliage height diversity had positive effect on bird abundance.Insect diversity had a certain correlation with bird richness,and plant richness had a positive effect on bird diversity by affecting insect diversity.In conclusion,compared with control group,the near-natural greenspace have significant advantages in bird diversity,mainly reflected in insectivorous and carnivorous birds.The abundant shrubs,herbs,and the complex vertical structure of the near-natural greenspace contribute to the enhancement of bird diversity.(4)Guangyanggu Urban Forest Park and Xinjiekou Urban Forest Park were divided into four habitat types,including tree-layer developed habitat(T),herb layer developed habitat(H),shrub-herb layer developed habitat(SH),tree-shrub-herb layer developed habitat(TSH).The results of insect sub-community comparison showed that the SH and TSH had higher insect richness and diversity,followed by H,and T had the lowest predator species richness and diversity.The results of bird group comparison showed that the relative abundance of birds in insect-eating/carnivor-flying group was the highest in the shrub-herb layer developed habitat(SH).Shrub-herb layer developed habitat(SH)and tree-shrub-herb layer developed habitat type(TSH)had the most complex food web structure,and the highest control of enemies,tree layer developed habitat(T)had the most simple food web structure,and the weakest control enemies.The results showed that the multi-layered and mixed communities had more complex food web structure,which was beneficial to improve plant,bird and insect diversity.It was suggested that the diversity of undergrowth shrubby and herbaceous layers should be added in certain area in the construction of urban park green space,and the community with complex vertical vegetation structure should be constructed.This study not only confirms the contribution of near-natural communities to biodiversity in small green spaces in metropolitan core urban areas,but also proposes applying the mosaic model of near-natural communities to urban parks based on zoning strategies.The results of this study will provide new ideas and methods for future park design and renovation,so as to improve the biodiversity and community stability of plants,insects and birds in the city. |
