Vegetation Cover Drives Arthropod Communities in Mediterranean/Subtropical Green Roof Habitats

Ibrahim Salman,Leon Blaustein

doi:10.3390/su10114209

Abstract

Worldwide, urban areas are expanding both in size and number, which results in a decline in habitats suitable for urban flora and fauna. The construction of urban green features, such as green roofs, may provide suitable habitat patches for many species in urban areas. On green roofs, two approaches have been used to select plants—i.e., matching similar habitat to green roofs (habitat template approach) or identifying plants with suitable traits (plant trait approach). While both approaches may result in suitable habitats for arthropods, how arthropods respond to different combinations of plants is an open question. The aim of this study was to investigate how the structural complexity of different plant forms can affect the abundance and richness of arthropods on green roofs. The experimental design crossed the presence and absence of annuals with three Sedum sediforme (Jacq.) Pau (common name: stonecrops) treatments—i.e., uniformly disrupted Sedum, clumped disrupted Sedum, and no Sedum. We hypothesized that an increased structural diversity due to the coexistence of different life forms of plants on roofs is positively related to the abundance and richness of arthropods. We found that arthropod abundance and richness were positively associated with the percent of vegetation cover and negatively associated with substrate temperature. Neither arthropod abundance nor richness was influenced by the relative moisture of substrate. We also found that arthropod abundance and richness varied by green roof setups (treatments) and by seasonality. Arthropod abundance on green roofs was the highest in treatments with annuals only, while species richness was slightly similar between treatments containing annuals but varied between sampling periods. This study suggests that adding annuals to traditional Sedum roofs has positive effects on arthropods. This finding can support the development of biodiverse cities because most extensive green roofs are inaccessible to the public and can provide undisturbed habitat for several plant and arthropod species.

Highlights

IntroductionSince the early 1990s, there has been an approximate 2 billion people increase [1]
Worldwide, urban areas are expanding both in size and number
33 ooff 1144 different life forms of plants on roofs is positively related to the abundance and richness of Warethhryoppootdhse.sized that an increased structural diversity due to the coexistence of different life forms of plants on roofs is positively related to the abundance and richness of arthropods

Summary

Introduction

Since the early 1990s, there has been an approximate 2 billion people increase [1]. This rapid urbanization is associated with an increase in both natural resource use and habitat fragmentation, leading to a decrease in alpha diversity. Preserving habitat diversity is practically important within urban areas, considering that cities play a crucial role for native species [2,3]. Conservation biologists have focused primarily on the protection of natural ecosystems and have placed little importance on urban areas or urban biodiversity [4]. Most studies on wildlife in cities have focused on birds [5,6]. Invertebrates, in general, comprise approximately 80% of all described species [10], which makes them an ideal research topic

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