5.1 Effects of SBI effectors for WQT wetland landscaping
Two aspects are commonly admitted for integrations of scenic beauty and ecological effects. On the one hand, knowledge of environmental geography plays a role in moderating beauty cognitions to be ecologically aware. On the other hand, it is believed that landscape aesthetic experience is a psychological process with perceptual, affective, and cognitive characteristics, which are often obtained from patterns of waterbodies, vegetation, and micro-topologies (Gobster et al., 2007). Phenomenon and rules can be indicated from SBI voting as the following:
(1) Vegetation conditions (B1) and SBIs
Plants are often beautifully shaped for sites with higher scores, while dense vegetation is attributed to higher green-looking ratios. The high density of arbours contributes more to SBIs, for scenes with multi-layered vegetation (e.g., Yangbei No.1, SBI = 6.2252) are more favourable to participants than those with a medium density of shrubs (e.g., Yangbei No.2, SBI = 5.8146) or floating-leave plants (e.g., Yangbei No.3, SBI = 5.7278), Based upon theses phenomenon, arbours, shrubs, herbaceous plants, and floating-leave plants should be arranged to maintain proper vegetation structures.
Site planted with homotypic deciduous vegetations often attributes to lower SBIs, while sites vegetated with more amounts of evergreen perennial aquatic plants often reach higher SBIs. Neat artificial Cinnamomum camphora groves can lead to emotions of fatigue or dullness (e.g., Shuijing No.2, SBI = 5.0473). Also, substrate beds of subsurface flow wetlands (SSF) allow sewage to flow from top to bottom, which is planted with high-density and single-typed Cyperus involucrate Rottboll are the most unattractive scene to participants (SBI = 4.3967). Thus, the landscape design of SSF wetlands should focus on improving varieties and integrations of vegetation.
(2) Physical geographic conditions (B2) and SBIs
Sites with semi-natural geo-features are often rated higher SBI, which is influenced by micro-topology and the form of the waterbody. Sites with slope revetment and well-vegetated buffers are often more ornamentally valuable than those with artificial linear embankments (e.g., Yangbei No. 3 and 4). Sites with vegetated wavy micro-topologies are often more attractive than others (e.g., Shuijing No. 2 and 4), for more multi-layered spaces can be created by setting appropriate micro-topologies wetland landscaping can be formed delicately.
Sites with high degrees of waterbody openness are rated higher for SBIs. It is believed that waterscapes with a higher degree of openness often demonstrate more obvious potential than those of lower openness. Psychological perceptions can explain this phenomenon. Semi-natural environments are supported for rendering visitors’ attention (Kaplan 1995). Waterscapes at those sites of higher waterbody openness are beneficial to improve participators’ attention restoration into senses of relaxation, immersion, and calmness. However, those with vast and empty water are often nonattractive (e.g., the sediment pond (SP) at Yangbei No.4), which should be avoided in practical design as much as possible.
(3) Human geographic conditions (B3) and SBIs
Sites with human geographic elements have more potential for natural education, which often attributes to higher SBIs. As for Yangbei Lake Wetlands, the bridge with ornamental boats (site No.1) and waterwheels (site No.2) attributed to higher human geographic characteristics, which highlight features of hydraulic landscapes. As for Shuijing Park, boardwalks and pavilions (Site No.3) and a wooden hut at the ornamental pond (site No.4) support cultural aesthetics. All sites in both wetlands own specific potentials for activities of natural education, especially for presentations of water purification processes. However, no related appliances or signals have been set in situ.
5.2 Applications in landscape design and management
(1) Following strategies of ecological engineering landscaping
Concerning the ‘perception realm’ theory by P. H. Gobster, large-scale patterns of ecological phenomena occurring in ecosystems are often invisible to the human being. In contrast, humans can only perceive small-scale cognitive landscape characters and patterns (Gobster et al., 2007). Thus, landscaping projects should concentrate on people’s landscape aesthetic experience at a specific scale, which would embody broader ecological processes. In line with AHP-based SBIs, strategies of ecological engineering landscaping (EEL) can be adapted in WQT wetlands of their dual attributes of ‘natural engineering’ and ‘engineered nature’.
WQT wetlands can form a harmonious scenic beauty, which can vividly express the naturalness and wilderness of wetlands. By incorporating EEL measures into landscaping, i.e., re-designing buffer zones, constructing green infrastructures, and re-arrangements vegetation structures. Also, waterscapes in different sections of WQT wetlands are recommended to be designed for higher cognitions with EEL, i.e., mechanism and workflows of wetlands in its various sections. Wetland cells are instructed to design in shapes with length/width ratios of less than 4:1 for treatment purposes. Curvilinear shapes that follow existing land contours should be used. By increasing the perimeter lengths of wetland cells by complex shapes, i.e., scalloped edges are shown above, a more affluent zone of transitional habitat for wildlife will be created. However, WQT effects on the overall wetland area would be lost. Thus, WQT wetlands should be designed to balance the habitat and treatment benefits. The landscape sequence in situ should be re-arranged to form an ecological landscape area for natural education to guide EEL engineering. Hence, in landscape planning and design of WQT wetlands, attention should be paid to integrating its aesthetic design issues with the technical engineering aspects of EEL (Huang 2022). In terms of landscape aesthetics, diverse forms of waterbodies, i.e., embankments, shoals, ponds, and pools, can be innovated in practical design for purifying waterbodies and reducing flow rates.
(2) Improving water quality treatment techniques
WQIs-SBIs relationships can be thoroughly explained with the characteristics of WQT wetlands. Constructed WQT wetland consists of 3 parts, including vegetation, microorganisms, and substrates, which integrate a highly complex WQT system. Among them, microorganisms play a vital role in improving water quality. Substrates are ideal for vegetation growth, while their WQT capabilities often relate to vegetation and physical geographic conditions. Suggestions oriented toward improvements of WQT techniques are listed as follows.
For the two wetlands mentioned in the research, physical and human geographic conditions should be optimised, especially for SPs and VFs. Nodes design of the SP and VF wetlands is found to be ignored by landscape architects. These measures can also arouse visitors' attention to the ecological principles of WQT processes. By adapting waterbodies with higher openness, more amounts of natural-form micro-topologies at buffers can contribute to more significant WQI improvements and SBIs. Vegetation can remove multiple pollutants by assimilation and oxidation. E.g., Phragmites australis and Canna indica L. are effective for CODCr and NH3-N removal. Evergreen perennial aquatic plants, e.g., Juncus effusus, are also recommended as ideal vegetation. Therefore, increasing vegetation density and planting more floating-leave vegetation at aeration ponds (AP) and free surface flow wetlands (FSF) are recommended. Otherwise, the constructions of siltation ponds are not appropriate in urban environments, as they are inclined to be polluted significantly, with a marked absence of vegetation and creature.
(3) Applying attention restoration theory
Spatial arrangements on various aspects of landscape patterns and decorative elements can psychologically modify visitors' aesthetic perceptions by affecting information processing capacities. According to attention restoration theory (ART) suggested by S. Kaplan, four sorts of restorative natural environments, including ‘Being away’, ‘Fascination’, ‘Compatibility’, and ‘Extent’, can be attributed to semi-natural wetland waterscapes (Kaplan 1995). It is believed that waterscapes with higher naturalness levels usually demonstrate a better effect of participating in restoration than those of lower naturalness. Among them, ‘being away’ means to be distant from highly artificial elements. Sites with characteristics of ‘fascination’ are often arranged with abundant landscape elements. Sites with spaces for developing diverse educational and recreational activities are regarded with high ‘compatibility’. Sites with readable contents of a substantial scope ate believed to be ‘extent’.
High and medium naturalness can create restorative natural environments of ‘being away’ and ‘extent’. In practical wetland design, waterscapes of higher naturalness and openness with semi-natural micro-topologies can significantly improve water quality treatments and scenic beauty. Thus, by designing waterscapes with naturalised characters, proper vegetation, and sufficient landscape elements, wetland landscapes can be preserved with attention to restoration and lower degrees of homogeneity.
5.3 Further improvements in experiments
So far, two main methods have been widely adopted in Scenic Beauty Estimation (SBE), i.e., expert-based evaluations (Sowińska-Świerkosz et al., 2016) and the perception-based method (Peng & Han, 2018). In terms of cost and time, expert-based methods outperform perception-based methods. It is indicated in the study that it is easier to verify the reliability and validity of perception-based methods with AHP voting than expert-based methods. We believe that further improvements as the following can be adapted in the experiment to enhance its credibility:
(1) Evaluations by the judges can directly reflect conditions of scenic factors. During the long and tedious evaluation process, participants may be impatient with SBI voting. Once no sufficient reward mechanism is offered, which could lead to deviations in the final evaluation results. Thus, it is vital to motivate participants during the SBI voting process.
(2) For the evaluation process that can be disturbed by sunlight conditions, camera-shooting methods should be optimised. Also, if states were permitted, 180° panoramic photographs or virtual reality presentations could be adapted for SBI judging in the future.
(3) For scenes and WQIs are dynamically changing in diverse seasons, SBI voting and water quality monitoring for wetlands shall be repeated at different seasons. At the same time, WQIs–SBIs correlation analysis will be developed more specifically.
(4) In addition to vision, other senses, i.e., hearing, smell, and touch, can also affect the perception of judges. For soundscapes to have intensive relationships with human comforts, fountains with large waterfalls or jects which can produce acoustic aversions (Patón et al., 2019), multi-sensory perception and related SBE scoring should be further proceeded to improve the credibility of experiments.