关键词: 非正式绿地, 自然演替, 居民感知, 棕地, 闲置土地

Abstract: The park-city concept introduces new requirements for the research and practice of green space. To address the dilemma of "seamless green insertion" in high-density built-up areas against background of stock renewal, systematically identifying, improving, and connecting all types of green spaces is essential. Informal green space (IGS) is an important part of urban green space and serves an extremely important ecosystem function. However, more specifically, the study of IGS has predominantly existed beyond the scope of research investigating urban green spaces (narrow sense) and, thus, lacks a clear definition and systematic cognition.
　　Using the literature analysis method, a total of nine studies in English from January 2000 to July 2021 published on the Web of Science core database were searched using the terms "informal green space". For the same period, a total of 312 studies in English were searched using the terms "brownfields", "vacant lots", "abandoned land" or "spontaneous vegetation", all of which are related to IGS. Meanwhile, seven studies were searched from Chinese National Knowledge Internet (CNKI) using the terms "informal landscape" or "informal green space". Combined with studies related to "vacant lots" and "brownfield", 49 studies in English and 14 studies in Chinese, all of which were strongly related to IGS, were then manually screened. These studies were used to form the research basis.
　　Through a review of the literature, the concepts and classifications of IGS were determined and popular topics in the current research were summarized. Several conclusions were drawn, as follows.
　　First, no consensus on the concept and classification of IGS has yet been reached. IGS was proposed by Rupprecht. It is generally believed that IGS is characteristic of temporality, nature and high accessibility. In the current study, IGS is defined as that which is within built areas in cities and forms due to a lack of and/or maintenance. Accordingly, it is green space spontaneously covered with growing vegetation, and this includes vacant lots, brownfield/industrial wasteland, riverside wasteland, abandoned railway, communities vacant land, gap, vertical planting and microhabitats. Generally speaking, IGS forms the urban green space together with green space (narrow sense) in China's Classification Standards of Urban Green Space (CJJ/T85-2017). Second, in view of popular research topics, the ecological and social functions of IGS as well as residents' perceptual preferences have represented core research content. Studies have expanded from the ecological functions of IGS in the regulation of climate and increased biodiversity to social functions such as promoting fairness around green space and minimizing crime. At the research level, studies have covered single or sample blocks to more systematic research on the urban scale. The current study connected the IGS with urban problems, such as sharp shrinkage. Third, IGS is valuable to the robust development of cities, including strengthening green infrastructure, improving the fairness of urban green space layouts, enriching the biodiversity of cities, and creating safe and healthy community environments for residents (among others). Fourth, residents' perception preferences with respect to IGS include like and hate. Residents view free restriction for use and short distances to their places of residence as fundamentally important. However, a lack of management and adequate garbage disposal practices represent major reasons for why residents reject IGS. Contact frequency with green space, age differences and other individual characteristics represent important factors that influence residents' perception preferences.
　　As an important type of urban green space (broad sense), IGS is attracting increasing attention from researchers. The current study aimed to address the problem of how to accurately understand the potential social and ecological functions of IGS and maximally use these functions to perfect urban green space systems and increase residents' wellbeing. Hence, the current study proposes three renewal IGS design modes: land-use changes, low-disturbance and quality improvement, and interface integration. Meanwhile, the strategic framework centered on IGS is proposed: First, systematically recognize IGS at the urban scale, renew it and improve its quality; second, increase the public's acceptance of natural landscapes; third, increase openness to IGS under the premise of a safety guarantee; fourth, pay attention to demands for use and residents' perceptions of IGS; fifth, understand the landscape penetration of multi-element space interfaces such as streets, walls and roofs by integrating interdisciplinary design (e.g., urban design, architectural design and landscape design).

Key words: informal green space, natural succession, resident perception, brownfield, vacant lots