*5.3. Presentation Layer*

The presentation layer represents the effect factors related to biodiversity, community structures, and ecosystems. The layer represents the existential state of species and is thus regarded as a presentation layer because variations in the generating layer can be represented by this layer. The presentation layer includes three sublayers. The first

sublayer (presentation layer one) is related to biodiversity and can be considered part of the community structure. Biodiversity often refers to functional diversity, phylogenetic diversity, species classification diversity, and so on. However, according to Oehri et al. [52], landscape diversity is also positively linked to EFs. The second sublayer (presentation layer two) represents the community structure and can be viewed as a part of an ecosystem. According to the works reviewed above, many effect factors of community structure are related to different aspects of community structure aside from biodiversity, including species' spatial patterns and trophic level structures. However, Delgado-Baquerizo et al. [66] found that the BEF relationship can also be affected by the biodiversity of other biomes. The authors show that the positive relationship between plant diversity and multifunctionality can be affected by soil biodiversity. The last sublayer (presentation layer three) is related to ecosystems and covers not only biological features but also abiotic environments. Due to the strong effects of environmental factors such as temperature and geology on EFs [67–69], presentation layer three reflects abiotic factors in most cases.

Moreover, the presentation layer reflects the interactions between human cognition and spatiotemporal scales. First, the presentation of species in this layer depends on levels of human cognition. The development of human cognition can enhance the form of presentation used. For example, according to human cognitive development, numerous biodiversity indexes with different ecological implications have been built to reflect certain aspects of biodiversity [53,70]. According to cognitive development, different methods for expressing community structures such as pattern indexes have also been proposed [71]. Second, as it is meaningless to study biodiversity, communities, and ecosystems without considering a spatiotemporal scale, human cognition about biodiversity, communities, and ecosystems is limited by the spatiotemporal scale. Moreover, the development of human cognition can also improve our understanding of scale effects and can further enhance the accuracy of species presentation in the presentation layer. Over the last three decades, numerous studies have focused on BEF at fine scales and over short time periods [72]. Such studies reveal the mechanisms of BEF at small scales but do not test the mechanisms involved at larger scales. Further understanding the role of scale in BEF research can help guide policies on BEF management [53].

### *5.4. Effect Layer*

The effect layer focuses on EFs and forms the outermost layer of the generatingpresentation model. Because EF is related to the effects of ecosystems, the layer is termed the effect layer. Within this layer, there are tradeoffs and synergies among different EFs. In addition, variations in the presentation layer generated from variations in the generating layer can influence the effect layer. The effect layer can also have feedback effects on the generating layer. A feedback loop thus exists between these three layers.
