Objective The sense of smell is of vital importance to humans. Olfactory landscapes have a remarkable impact on human physiology, behavior, and emotions. Nature reserves boast relatively unique types of scents, with their characteristic mechanisms differing from those of urban olfactory landscapes. However, current research on olfactory landscapes mainly centers around cities and gardens. The aim of this research is to clarify the elements of olfactory landscapes in the built environment of nature reserves and the impact mechanisms on human perception. This study aims to: 1) construct a classification system for the olfactory landscapes in the Jiuzhaigou World Heritage Site; 2) explore the action paths of the characteristics of different types of olfactory landscapes on tourists' perception; 3) provide new evidence for the knowledge system through the evidence of olfactory landscape walks.

Methods This study investigates olfactory landscapes in the Jiuzhaigou National Nature Reserve, focusing on how odors affect visitors' perceptions of the environment. The reserve, recognized for its rich biodiversity and natural beauty, was studied through an olfactory walking survey, where eight key olfactory areas were identified. Data was collected from 100 healthy participants via interviews and questionnaires conducted between July 27-29, 2022. The participants, aged from under 18 to over 60, were asked to identify odors and rate their perceptions of the environment based on 12 sensory indicators such as familiarity, sweetness, and naturalness. Interviews helped categorize odors into various types, such as human-driven, facility-driven, water-driven, plant-driven, and soil-driven. Statistical analysis, conducted in Excel and SPSS, focused on the frequency of odor categories, the mean sensory ratings, and correlations between olfactory features and perceptions. The study used Spearman partial correlation to analyze relationships while adjusting for other factors. The goal was to explore how different elements of olfactory landscapes influence visitors' experiences, providing valuable insights into the role of smell in enhancing natural tourism and environmental design.

Results Respondents identified odors at eight sampling sites, which were categorized into four types of olfactory landscapes based on the dominant smells: 1) Human-Dominated: Site 7 had a 50% Probability of Odor Manifestation (POM), dominated by incense from Tibetan Buddhist prayers. 2) Facility-Dominated: Site 3, with a POM of 47.06%, had wood smells from pavilions and boardwalks. 3) Water-Dominated: At Sites 2 and 5, the odor was influenced by damp, cool characteristics of waterfalls, with POMs of 50% and 35.9%, respectively. 4) Plant-Dominated: Sites 1, 4, 6, and 8 had vegetation-based odors. Site 1 was dominated by grass (POM 36.84%), while the others had tree-dominant smells, with POMs ranging from 20% to 57.15%. The mean scores for perceptual evaluations and odor characteristics revealed the following: 1) Human-Dominated and Water-Dominated landscapes scored the highest in liking, relaxation, and satisfaction, ranking first and second, respectively. 2) Plant-Dominated landscape ranked lowest in satisfaction. 3) Facility-Dominated landscape scored lowest in liking and relaxation. In terms of odor characteristics: 1) Human-Dominated excelled in familiarity, compatibility, sweetness, intensity, and uniqueness. 2) Water-Dominated scored highest in naturalness, freshness, diffusion, exposure frequency, and persistence. 3) Plant-Dominated scored highest in recognition and mixing. 4) Facility-Dominated ranked lowest in compatibility, freshness, uniqueness, and diffusion. Further analysis was conducted to explore how the characteristics of the olfactory landscapes influenced perceptual evaluations: 1) Human-Dominated Landscape: Familiarity was strongly positively correlated with relaxation (p < 0.01), with no significant correlations found for other indicators. 2) Facility-Dominated Odor: Compatibility and naturalness positively correlated with liking (p < 0.05) and relaxation (p < 0.01). Sweetness, naturalness, and mixing were positively correlated with liking. 3) Water-Dominated Odor: Duration was positively correlated with liking, while familiarity and duration were negatively correlated with satisfaction. 4) Plant-Dominated Odor: Compatibility, uniqueness, and exposure frequency were positively correlated with liking, while compatibility, naturalness, uniqueness, diffusion, and persistence correlated with relaxation.

Conclusion Understanding and revealing the current situation of olfactory landscapes in World Natural Heritage Sites is of great theoretical and practical significance for improving environmental quality and tourism experience. Based on on-site investigations and tourist perception evaluations, this study established a classification framework system for the scent landscapes in Jiuzhaigou and analyzed in detail the differences in elemental characteristics and perception evaluations of four types of olfactory landscapes. The study found that: 1) For human-dominated olfactory landscapes, there is only a highly significant positive correlation between familiarity and relaxation, and there is no significant correlation among the three perception evaluation indicators; 2) Facility-dominated olfactory landscapes are below the average level in all perception evaluation indicators and received the most negative ratings; 3) Water-vapor-dominated olfactory landscapes usually receive high perception ratings, and all evaluation indicators exceed the average level; 4) Plant-dominated olfactory landscapes stand out in relaxation ratings, and relaxation is related to its degree of matching, naturalness, uniqueness, diffusivity, exposure frequency, persistence, and degree of mixing. The same elemental characteristics have significant differences in the degree of influence and priority order on perception evaluations in different types of olfactory landscapes. The research results further emphasize the unique role of aroma in creating spiritual value and the significant impact of plant scents on relaxation experience.