International Journal of
Environmental Research
and Public Health
Article
The Relationship between the Restorative Perception of the
Environment and the Physiological and Psychological Effects
of Different Types of Forests on University Students
Qiaohui Liu 1 , Xiaoping Wang 1, Jinglan Liu 2,*, Guolin Zhang 3, Congying An 2 , Yuqi Liu 2 , Xiaoli Fan 2 ,
Yishen Hu 2 and Heng Zhang 4
1 College of Forestry, Beijing Forestry University, Beijing 100083, China; liuqiaohui202109@163.com (Q.L.);
wangxp@bfdic.com (X.W.)
2 School of Ecology and Nature Conservation, Beijing Forestry University, Beijing 100083, China;
acy19961219@163.com (C.A.); rachelyuqi@gmail.com (Y.L.); fanxiao0802@163.com (X.F.);
hys16637102261@163.com (Y.H.)
3 Management and Protection Center, Xiaolongshan National Nature Conservation, Tianshui 741020, China;
z13884583683@163.com
4 Ming Dynasty Tombs Forest Farm, Beijing 102200, China; zhyxm2003@163.com
* Correspondence: liujl66@bjfu.edu.cn; Tel.: +86-010-6233-6716
Citation: Liu, Q.; Wang, X.; Liu, J.;
Zhang, G.; An, C.; Liu, Y.; Fan, X.; Hu,
Y.; Zhang, H. The Relationship
between the Restorative Perception of
the Environment and the
Physiological and Psychological
Effects of Different Types of Forests
on University Students. Int. J. Environ.
Res. Public Health 2021, 18, 12224.
https://doi.org/10.3390/
ijerph182212224
Academic Editor: Simon Bell
Received: 20 October 2021
Accepted: 17 November 2021
Published: 21 November 2021
Abstract: Short-term exposure to a forest environment is beneficial to human physiological and
psychological health. However, there is little known about the relationship between the restorative
perception of environment and physiological and psychological restoration achieved by experiencing
the forest environment. This study evaluated the relationship between the restorative perception
of different types of forests and human physiological and psychological effects. A sample of 30
young adult students from Beijing Forestry University was exposed to coniferous, deciduous, and
mixed forests as well as an urban site. Restorative perception of the environment was measured
using the PRS questionnaire. Restorative effects were measured using physiological indicators
(blood pressure and heart rate) and three psychological questionnaires (Restorative Outcome Scale;
Subjective Vitality Scale; Warwick–Edinburgh Mental Well-being Scale). The results demonstrated
the following: (1) There were significant differences in the perceived restorative power of the three
types of forests, with the highest level in the mixed forest, followed by the coniferous forest and
the deciduous forest. (2) All types of forests were beneficial to physiological and psychological
restoration. The mixed forest had the greatest effect in lowering blood pressure and heart rate as
well as increasing vitality, while the coniferous forest had the strongest increases in psychological
restoration and positive mental health. (3) The level of perceived restorative power of environment
was positively related to the physiological and psychological restoration. These findings provide
practical evidence for forest therapy that can maximize the restorative potential of forests.
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Keywords: restorative environment; forest types; forest therapy; physiological restoration;
psychological impact; human well-being
Copyright: © 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
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4.0/).
1. Introduction
Industrialization has greatly promoted the emergence and development of modern
cities, and urbanization has further expanded the spatial scope of cities. As a result, the
original natural environment and human settlement environment have undergone drastic
changes. Fast-paced urban life, intense competitive pressure, busy work, and separation
from the natural environment have become incentives for an increasing number of chronic
diseases or mental illnesses such as diabetes, obesity, insomnia, and depression among
urban residents [1–3]. Moreover, studies in growing numbers have confirmed that people
can obtain restorative experiences in the natural environment and that there is a proven
positive relationship between exposure to nature and health-related well-being [4,5]. The
Int. J. Environ. Res. Public Health 2021, 18, 12224. https://doi.org/10.3390/ijerph182212224
https://www.mdpi.com/journal/ijerph
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natural environment is considered as a restorative environment for most people, which
can help people to achieve a better recovery from mental fatigue and negative emotions as
well as physiological reactions [6,7].
Attention restoration theory (ART) and stress reduction theory (SRT) are usually
seen as essential theories to illustrate the pathways toward restoration in nature. ART
is based on the assumption that nature can prompt the individual to transform from
“directed attention” to “undirected attention”, so that the individual can be replenished
from the attention fatigue caused by “directed attention”, that is, the stress state can be
restored during the interaction between people and nature [6]. SRT is based on the point of
psychological evolution, which states that people have dependence on or preference for
certain natural characteristics under stress, and contact with the natural environment helps
people gain recovery from all stress [7]. Both ART and SRT theories posit that people have a
strong and consistent positive trend toward the natural environment. According to ART, a
restorative environment generally has four characteristics, namely, being away, fascination,
extent, and compatibility [6]. Being away refers to the psychological state that is generated
by a situation that is different from the usual situation, which can avoid the fatigue of the
psychological state [8]. Fascination means the environment is so attractive that contextual
information can be noticed without effort, so as to avoid continuous use of attention in order
to get relaxion [9]. Extent indicates the environment has enough richness and continuity of
scenes so that concentrated attention can be rested. Compatibility requires an environment
having a good match with the individual’s motivation, behavior, information, ability, or
inclinations [10]. Hartig designed and developed the Perceived Restoration Scale (PRS)
that is used to measure the restorative potential of an environment based on the ART [8],
which has been widely used in an increasing number of environmental restoration studies.
The effects of a restorative environment are reported in both physiological restoration
and psychological well-being. Numerous studies have confirmed that restorative envi-
ronments are beneficial for improving the cognitive and positive emotional state [11,12]
and reducing anxiety and stress [13,14] as well as lowering the occurrence of physical dis-
eases [15], promoting self-identity [16], stimulating creativity [17], restoring attention [18],
and boosting people to achieve a better mental state and work performance. Meanwhile,
studies have concluded that there were differences in the restorative effects of individuals
in different types of environments [18,19]. It was found that scenes in daily life in a city
with more natural elements achieved a higher perception of restoration [20]. In addition,
the dimensions of restorative perception of the environment were of different levels of
importance [21]. Some studies stated that the fascination dimension had the greatest influ-
ence on perceived restorative power of the environment [22,23], while another confirmed
that compatibility had the greatest impact [24]. Moreover, researchers have established a
positive relationship between the perceived restorative power of the natural environments
and physiological and psychological responses, which means that a higher restorative
perception indicates a stronger physiological and psychological restorative effect [25].
Forests are recognized as one of the core health resources because they provide
excellent ecological environments and rich scenic views that create a safer and more
relaxing environment than other types of vegetation [26]. At present, most scientific
research mainly focusses on the difference in the effect of the urban–forest dichotomy, and
results proved the good performance of forests in relation to health benefits [27]. Exposure
to a forest environment helps in reducing blood pressure [28,29] and heart rate [30] while
increasing feelings of vitality, subjective revival, and mental health [31,32]. However,
studies have found that not all forests have the same level of restorative effects [33] as the
promotional effects of the forest on a subjects’ health might be influenced by the different
forest characteristics (age, tree species, size, type, and density of trees and vegetation) that
shaped the forest landscapes and environments [27]. Even the shape of the trees in the forest
can affect health benefits, trees with a natural shape had a better positive effect on lifting
emotions and lowering blood pressure than trees with geometric shapes [34]. Furthermore,
it was confirmed that the restorative effects were closely related to the abundance of plant
Int. J. Environ. Res. Public Health 2021, 18, 12224
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species in the natural environment [35], whereas excessive naturalness and plant density
were also not conducive to the restorative effect. A field experiment in Switzerland showed
that walking in a dense forest with obvious signs of maintenance was more restorative than
walking in an equally dense but unkempt forest [36]. Therefore, the capacity of forests to
improve human health may be influenced by different forest characteristics, which means
that some forests are more appropriate or effective than others.
According to arousal theory [37], people’s cognition and evaluation determine the
emotional forms, and the intensity of emotions depends on the level of arousal. Evaluation
and emotional forms work together on the state of emotions, and the initiation of mood
is usually a response to environmental stimuli and emotions [38]. The cognitive theory
of emotion posits that when people receive stimuli in the environment, they will also
adjust and adapt [39]. Based on above-mentioned theory, Bagozzi put forward the self-
regulation of attitudes theory, which states that evaluation will promote the generation
of emotions and further affect the individual’s behavior or behavior intention, which is
generally expressed as a process of evaluation–emotion–behavior [40]. The restorative
perception of the environment is also a gradual process of psychological perception, which
proceeds from cognitive evaluation of the environment to physiological and psychological
reactions. It is easy for people to rely on and identify with a well-evaluated environment
and realize the match between relaxation expectations and environment to promote the
recovery of physical and mental health.
However, to our knowledge, even though a few studies have explored the restorative
effects of forests on human health and well-being, few have examined the relationship
between the restorative perception assessed using the Perceived Restoration Scale (PRS)
and physiological and psychological restoration achieved by experiencing the forest envi-
ronment. Therefore, the main objective of this study was to investigate the relationship
of the restorative perception of different types of forests (mixed forest, deciduous forest,
and coniferous forest) and its human physiological and psychological restorative effects. In
particular, we sought to pinpoint the relation between restorative perception of environ-
ment and physiological and psychological effects by answering three research questions:
(I) Would the restorative perception assessment of different types of forests be different?
(II) Do different types of forests influence physiological and psychological restoration
differently? (III) Would the relationships between restorative perception and physiological
and psychological restoration be positive?
2. Materials and Methods
2.1. Participants
Participants were recruited from Beijing Forestry University by the Internet (WeChat
mobile application). There were 30 adult university students who participated in the field
experiments, including 16 female and 14 male participants with a mean age of 23.9 years
(SD = 1.86). The sample included different students with majors to avoid the bias of the
students’ major in regard to their forest science knowledge. All subjects of this study
were healthy Chinese adults. Participants with physical or mental disorders or those
taking insomnia drugs or stimulants as well as those with heavy smoking and drinking
habits were excluded from the study. During the recruitment, the aims and experimental
procedures of the study were informed to the students who willingly participated. All
procedures involved in this study were in accordance with the ethical standards of the
Ethics Committee of Beijing Forestry University and the Declaration of Helsinki from 1964.
All participants gave written consent for their voluntary participation.
2.2. Study Sites
Participants were exposed to three different types of forests and an urban site located
in Beijing, China (Figure 1). All the forest sites were in Mangshan National Forest Park, the
largest national forest park in Beijing, which is 40 km away from the city. The total area of
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the Mangshan National Forest Park is 8622 ha, and the forest coverage rate is 86%. The
urban site was a city square in the center of downtown.
The urban site was Wudaokou Shopping Square, which is a city square in the center
of downtown with a large amount of people and vehicles, and the surrounding area
was characterized by urban elements such as a subway station, a shopping mall, roads,
supermarkets, and community houses, which is a typical urban site (Figure 2A).
The forest site in which the species composition was dominated by Quercus mongolica
and Pinus tabuliformis was coded as a mixed forest. It is a typical coniferous and broad-
leaved mixed forest (Figure 2B). For the second forest site, the dominant tree species was
Cotinus coggygria, which grows in summer and sheds its leaves in winter; it was coded
as a deciduous forest (Figure 2C). The species composition of the third forest site was
dominated by Platycladus orientalis, evergreen forest, which was coded as a coniferous
forest (Figure 2D). All three types of forests were planted about 40 years ago, and forest
characteristics in forest sites investigated by the study team are shown in Table 1.
Table 1. Forest characteristics in forest sites.
Forest Site
Dominant tree species
Tree height (m)
Diameter breast height (cm)
Canopy closure (%)
Visual penetration through stand (m)
Stand density (trees ha−1)
Mixed Forest
Deciduous Forest
Pinus tabuliformis
Quercus mongolica
7 ± 1.22
22 ± 3.67
0.7 ± 0.03
40 ± 1.47
525 ± 11
Cotinus coggygria
5 ± 1.00
15 ± 3.35
0.55 ± 0.01
25 ± 3.74
664 ± 10
Data are presented as the means ± SD.
Coniferous Forest
Platycladus orientalis
8 ± 0.81
16 ± 1.81
0.6 ± 0.05
45 ± 1.23
825 ± 8
Figure 1. The map of experimental locations.
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Figure 2. Photos: (A) city site, (B) mixed forest, (C) deciduous forest, (D) coniferous forest.
2.3. Procedures
The experiment took place in June 2021 in sunny weather conditions. Participants
were exposed to each of the study sites at the same time of a different day. The study
protocol was the same for each experiment (Figure 3). Participants gathered in a classroom
of Beijing Forestry University at 8 a.m. of each study day and had their blood pressure and
heart rate measured and completed all questionnaires at the gathering point as baseline
measurements. The procedure of obtaining baseline measurements took nearly 10 min.
Afterward, participants were transported to the study sites by a school bus (nearly 40 min).
While on the bus, participants were randomly and evenly divided into three groups, with
10 participants in each group (group A, group B, and group C). The participants were asked
to sit at the selected spot for 30 min in the respective forest sites. After sitting, researchers
conducted blood pressure and heart rate measurements, and then the participants finished
the questionnaires at the sitting sites. After taking a break for 10 min, participants were
asked to walk 30 min with a speed of moderate energy expenditure. After walking, the
participants chose a flat and comfortable place to sit down and rest for 3 min, researchers
conducted blood pressure and heart rate measurements, and then participants completed
the questionnaires. The entire experimental procedure required each participant to visit
four study sites including three forest sites (three different types of forests) and one urban
site. Each person only visited one forest site on one day. All participants visited three forest
sites and an urban site in order to increase the validity of the study. All 30 participants
visited the urban site at the same time of day and were evenly and randomly divided
into three groups guided by three researchers in each group in order to conduct the
measurements. During the experiment period, talking, eating, and drinking energy drinks
were not allowed.
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Figure 3. Flow diagram for on-site experimental protocol.
2.4. Measurements
Blood pressure (systolic blood pressure (SBP), diastolic blood pressure (DBP)) and
heart rate (HR) were measured to record participants’ physiological responses. Heart rate
and blood pressure are closely related to the sympathetic and parasympathetic nervous
system in the autonomous nervous system. When an individual is in a state of rest or
relaxation, the function of the parasympathetic nervous system is strengthened, and the
heart rate slows down while blood pressure decreases. Conversely, when an individual is
in a state of tension or stress, the excitability of the sympathetic nervous system increases,
and the heart rate and blood pressure also increase [41,42]. Blood pressure parameters
were measured using an Omron IntelliSense blood pressure monitor (HEM-7207). Heart
rate was measured using a Polar monitor (TEAM PRO). A lower score indicates higher
physiological well-being.
The Perceived Restoration Scale (PRS) was used to measure the restorative perception
of the environment, which includes four sub-scales, namely being away, fascination, extent,
and compatibility [8]. In this study, we used the scale with 22 items modified by Chinese
scholars [43]. Each item had a seven-point Likert scale ranging from 0 (= totally disagree)
to 6 (= totally agree). A higher score indicates higher restorative potential.
Three psychological measurement questionnaires all in their Chinese versions were
used to measure participants’ psychological responses. The Restorative Outcome Scale
(ROS) was used to evaluate the restorative effects and was composed of six items. Each item
was ranked on a seven-point Likert scale ranging from 0 (=totally disagree) to 6 (=totally
agree). In this study, we used the scale modified for forest-related experience [32]. The
Subjective Vitality Scale (SVS) was used to the measure level of vitality. It was composed of
four items with a seven-point Likert scale ranging from 0 (=totally disagree) to 6 (=totally
agree). The reliability and validity of the SVS have also been confirmed in a previous
study [44]. The Warwick–Edinburgh Mental Well-being Scale (WEMWBS) was used to
assess positive mental health. This scale can evaluate the positive emotions of mental health
and satisfaction in interpersonal relationships [45]. The Chinese version has 14 items and its
reliability and validity have been verified in a previous study [46]. Each item was evaluated
with a five-point Likert scale ranging from 0 (=not at all) to 4 (=extremely). A higher
score indicates higher psychological well-being in the three psychological measurement
questionnaires. During the site study, 10 min was enough for each participant to finish all
these questionnaires. All questionnaires in this study used the time frame “at this moment”
for timely measurements of the participants’ responses.
Although PRS could also be categorized as a psychological assessment scale, there are
distinct differences between PRS and other three psychological assessment scales. PRS is the
measurement used to assess whether the environment is a restorative environment, which
focus on evaluation of the environment itself. As other three psychological questionnaires
(Restorative Outcome Scale; Subjective Vitality 24 Scale; Warwick–Edinburgh Mental
Int. J. Environ. Res. Public Health 2021, 18, 12224
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Well-being Scale) were used to measure the reactions or responses of participants to the
investigated environments, which are more likely to be used for timely measurement of
participants’ psychological responses (or known as restorative effects) as influenced by
the environment.
2.5. Statistical Analysis
In this study, we used Excel 2010 (Microsoft Corporation) to record raw data from all
questionnaires and measurements. All statistical analyses were processed by SPSS 23.0
(IBM, Armonk, NY, USA). We used a one-way analysis of variance (ANOVA) to compare
the differences between the values of the physiological, psychological, and perceived
restoration level among the three types of forests and the urban site. Least significant
difference (LSD) was used to do a post hoc test to compare the differences of variables in
different types of forests. Spearman rank correlations analyses were conducted to explore
the relationship between the restorative perception of environment and the physiological
and psychological effects.
3. Results
3.1. Differences in the Restorative Perception of Experimental Sites
3.1.1. The Total Scores of PRS in the Different Types of Forests and the Urban Site
A one-way ANOVA analysis revealed that the PRS scores significantly differed among
the four experimental sites (F = 1268.04, p < 0.001). The mixed forest was perceived as
the most restorative environment, followed by the coniferous forest and the deciduous
forest, and the urban site was the least restorative (Table 2). The LSD post hoc test showed
significant differences between the urban site and the three types of forests (p < 0.001), and
there were also significant differences among the three forest sites (p < 0.05).
Table 2. Total and dimensional scores of PRS.
Scores of PRS
Dimensional Scores of PRS
Being Away Fascination
Extent
Compatibility
CF
4.29 ± 1.06
5.01 ± 0.96 3.83 ± 1.02 4.81 ± 0.81 3.89 ± 0.81
DF
4.25 ± 1.12
3.99 ± 1.17 4.17 ± 1.13 4.36 ± 1.11 4.53 ± 0.97
MF
4.84 ± 0.95
4.74 ± 1.05 4.85 ± 0.96 4.73 ± 0.91 5.03 ± 0.82
CK
1.56 ± 1.13
1.23 ± 1.00 1.91 ± 1.29 1.24 ± 0.78 1.57 ± 1.05
Data are presented as the means ± SD. CF = coniferous forest, DF = deciduous forest, MF = mixed forest,
CK = city site.
3.1.2. The Four Dimensions of PRS among the Different Types of Forests and the
Urban Site
The scores in the four dimensions of PRS showed that all three forest sites had higher
values than the city site. For the “fascination” and “compatibility” dimensions, the mixed
forest was at the highest level, followed by the deciduous forest and the coniferous forest.
For “being away” and “extent” dimensions, the coniferous forest was at the highest level,
followed by the mixed forest and the deciduous forest (Table 2, Figure 4).
A one-way ANOVA revealed that all four-dimensional scores of “being away” (F = 410,
p < 0.001), “fascination” (F = 312, p < 0.001), “extent” (F = 422, p < 0.001), and “compatibility”
(F = 418, p < 0.001) were significant. The LSD post hoc test showed significant differences
in the dimensions of “being away”, “fascination”, “extent”, and “compatibility” between
the urban site and the three forests (p < 0.001), and there were also significant differences
among the three forest sites (p < 0.05).
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FigFuireg4u. rCeo4m.pCariosomn opfathreisdoimnenosfiotnhalescdoriems oefnPsRiSoinnafolusrceonvrierosnomfenPtaRl sSiteisn. Dfoatuarareenviron
presented as the means ± SEs. CK = city site, CF = coniferous forest, DF = deciduous forest,
MF = mixed forest.
3.2. Differences in the Physiological Restoration in Three Types of Forests
Table 3 shows the mean values and standard deviation (SD) of the evaluated physio-
logical parameters, including blood pressure and heart rate. The mean SBP, DBP, and HR
values decreased in all forest sites, while these parameters had increases in the urban site,
with the strongest decrease in the mixed forest and the lowest decrease in the deciduous
forest (Table 3, Figure 5). The results of a one-way ANOVA showed that the restoration
effects on SBP (F = 52.13, p < 0.001), DBP (F = 27.28, p < 0.001) and HR (F = 17.61, p < 0.001)
differed significantly among the three forest sites and the urban site (Figure 4). The LSD
post hoc test showed significant differences in SBP, DBP, and HR values between the urban
site and the three forest sites (p < 0.001), and there were also significant differences among
the three forest sites (p < 0.05).
Table 3. Mean and standard deviation (SD) of physiological parameters (systolic blood pressure (SBP), diastolic blood
pressure (DBP), and heart rate (HR)) in the four experimental sites.
SBP
DBP
HR
Baseline (TO)
Baseline (TO)
Baseline (TO)
City Site
Mean
SD
113.30
4.71
116.13
7.21
66.70
4.24
68.50
5.90
79.70
4.09
81.17
4.60
Mixed Forest
Mean
SD
117.10
4.44
107.10
7.88
70.77
5.12
64.70
6.74
82.07
3.61
76.92
5.66
Deciduous Forest
Mean
SD
114.33
108.72
68.63
65.27
78.60
75.90
6.48
7.30
5.50
5.731
3.38
4.65
Coniferous Forest
Mean
SD
116.07
5.35
113.73
7.19
71.30
4.69
66.60
5.83
80.63
3.01
78.53
5.67
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Figure 5. Comparison of reduction in values of SBP and DBP as well as HR in the four experimental
sites. Data are presented as the means ± SEs. CK = urban site, CF = coniferous forest, DF = deciduous
forest, MF = mixed forest.
3.3. Differences in the Psychological Restoration in Three Types of Forests
Table 4 illustrates the mean values and standard deviation (SD) of the assessed psy-
chological parameters, including ROS, SVS, and WEMWBS measures. The mean ROS, SVS,
and WEMWBS values increased in all forest sites, while they decreased in the city site. The
mean value of ROS and WEMWBS increased the most in the coniferous forest followed
by the mixed forest and the deciduous forest. The highest scores of SVS were achieved
in the mixed forest (Table 4). The results of a one-way ANOVA showed that restorative
effects on ROS (F = 302.71, p < 0.001), SVS (F = 328.24, p < 0.001), and WEMWBS (F = 293.47,
p < 0.001) differed significantly among the three forest sites and the urban site (Figure 6).
The LSD post hoc test showed significant differences in ROS, SVS, and WEMWBS values
between the urban site and the three forest sites (p < 0.001), and there were also significant
differences among the three forest sites (p < 0.05).
Table 4. Mean and standard deviation (SD) of psychological parameters (ROS, SVS, and WEMWBS) in the four
experimental sites.
ROS
SVS
WEMWBS
Baseline (TO)
Baseline (TO)
Baseline (TO)
City Site
Mean
SD
2.03
0.75
1.51
0.97
1.83
1.03
0.95
0.72
1.86
0.710
1.57
1.04
Mixed Forest
Mean
SD
2.21
0.78
4.24
1.31
1.74
0.88
4.60
1.07
1.93
0.715
2.95
0.89
Deciduous Forest
Mean
SD
2.15
0.76
4.14
1.21
1.80
0.95
4.35
1.22
2.01
0.72
2.95
0.92
Coniferous Forest
Mean
SD
1.79
0.81
4.01
1.27
1.97
0.91
3.94
1.42
1.89
0.73
3.02
0.87
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Figure 6. Comparison of the increased values of ROS, SVS, and WEMWBS in the four experimental
sites. Data are presented as the mean ± SEs. CK = city site, CF = coniferous forest, DF = deciduous
forest, MF = mixed forest.
3.4. The Relationship between Restorative Perception of Environment and Physiological Parameters
The Spearman rank correlations showed that the level of PRS and the four sub-scales
of PRS were positively related to the restoration experience measured by the SBP, DBP, and
HR in all forest environments (Table 5). The correlation coefficient is a negative value, but it
is described as a positive correlation because decreases in physiological indicators portray
a better restorative effect of the environment. The highest correlations were calculated for
the PRS in the SBP, and the highest correlations were calculated for the four sub-scales
of PRS in “compatibility” followed by “fascination” in the SBP. All these correlations
between physiological indicators and PRS as well as four sub-scales of PRS were significant
(p < 0.01).
Table 5. Spearman rank correlations between the PRS and four sub-scales of PRS and the SBP, DBP, and HR.
SBP
DBP
HR
Spearman
Correlation
Sig. (two-tailed)
Spearman
Correlation
Sig. (two-tailed)
Spearman
Correlation
Sig. (two-tailed)
Four Sub-Scales of PRS
PRS
Being Away
Fascination
Extent
−0.506 **
−0.370 **
−0.468 **
0.000
0.000
0.000
−0.352 **
−0.328 **
−0.345 **
0.000
0.000
0.000
−0.347 **
−0.258 **
−0.328 **
0.000
0.000
0.000
** Correlation is significant at the p < 0.01 level (two-tailed).
−0.327 **
0.000
−0.373 **
0.000
−0.357 **
0.000
Compatibility
−0.506 **
0.000
−0.352 **
0.000
−0.347 **
0.000
−
−
−
−
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3.5. The Relationship between Restorative Perception of the Environment and
Psychological Parameters
The Spearman rank correlations showed that the level of PRS and the four sub-scales
of PRS were positively related to the restoration experience measured by the ROS, SVS, and
WEMWBS in all forest environments (Table 6). The highest correlations were calculated for
the PRS in the SVS, and the highest correlations were calculated for the four sub-scales of
PRS in “being away” in the ROS. All these correlations between physiological indicators
and PRS as well as the four sub-scales of PRS were significant (p < 0.01).
Table 6. Spearman rank correlations between the PRS and four sub-scales of PRS and the ROS, SVS, and WEMWBS.
ROS
SVS
WEMWBS
Spearman
Correlation
Sig. (two-tailed)
Spearman
Correlation
Sig. (two-tailed)
Spearman
Correlation
Sig. (two-tailed)
Four Sub-Scales of PRS
PRS
Being Away
Fascination
Extent
0.541 **
0.737 **
0.570 **
0.000
0.000
0.000
0.708 **
0.678 **
0.673 **
0.000
0.000
0.000
0.458 **
0.669 **
0.535 **
0.000
0.000
0.000
** Correlation is significant at the p < 0.01 level (two-tailed).
0.538 **
0.000
0.542 **
0.000
0.502 **
0.000
Compatibility
0.541 **
0.000
0.708 **
0.000
0.458 **
0.000
4. Discussion
4.1. Restorative Perception of Different Environments
There were significant differences in the values of the PRS and the four sub-scales
of the PRS in the different types of forests and the urban site. The mean scores of the
PRS were at a higher level in all forest sites compared with that in the urban site, which
means that the forest environments were better restorative environments. This is consistent
with previous research on restorative forest environments [47–49]. The mean scores of
PRS had the highest values in the mixed forest followed by the coniferous forest and
deciduous forest. A possible explanation for the results may be the public’s preferences
for the structural attributes of forests. To some degree, people seem to prefer natural
landscapes. The scenes in the less natural group received less visual attention from the
subjects [50,51]. Mixed forests form a stand structure with multiple layers and a thick
canopy and have more abundant understory vegetation, thus, the beauty of the mixed
forest is higher than that of the pure forests [52]. Comparing the city environment with
the forest environments, “fascination” showed significant changes in both forest sites and
city sites. This finding is consistent with ART, which posits that the attention-grabbing
qualities of a natural environment are the core element of its restorative potential [6,19].
ART may offer some additional interpretation, as it states that a more natural environment
tends to afford a restoration experience in the sense of being away, fascinated, coherent,
and compatible.
4.2. Effects of Different Environments on Physiological Health
The results of the study showed significantly different levels of SBP, DBP, and HR
restoration between the urban site and the forest sites, which is consistent with the results of
previous studies that natural environments exert greater physiological restorative impacts
than do built environments [53–55]. Forests are superior because they provide a special
interior forest climate with reduced air temperature, high air purity and humidity, and
special light conditions. These climatic factors are beneficial to health and relieve the
respiratory tract and the thermoregulation system [56]. In addition, in line with our
expectations, we found significant difference in the mean level of SBP, DBP, and HR
restoration of subjects among three different types of forests, with strongest recovery in the
Int. J. Environ. Res. Public Health 2021, 18, 12224
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mixed forest. This may be because a natural environment with rich sensory stimulation can
easily arouse the biophilic emotion of people who love nature and desire to be subordinate
to nature. The positive reaction of the body is more obvious in scenes with rich sensory
stimulation [57]. In particular, the restorative qualities may be more perceptible in the
mixed forest, which has a more complex tree composition.
4.3. Effects of Different Environments on Psychological Well-Being
From the results, it was found that forest environments had a better restorative effect
on ROS, SVS, and WEMWBS than did the urban environment. This is consistent with the
results of previous studies, which confirmed that values in the ROS and SVS increased
because of forest exposure [31,48]. One of the most important factors is the peace and quiet
in forests, which is essential for mental recovery in a time of acoustic stimulus overload in
urban settings. Moreover, there were significant difference in ROS, SVS, and WEMWBS
in three forests. The coniferous forest had the strongest effects on increase of ROS and
WEMWBS, which may be related to the volatile organic compounds (VOCs) emitted by
trees and plants. It has been confirmed that the coniferous forest was more productive in
the emission of phytoncide [58], which is beneficial for reducing mental fatigue, improving
cognitive performance, and inducing relaxation [59]. Environmental characteristics such as
moderate complexity and depth are among the most important mechanisms following the
SRT, which also explains why the coniferous forest in this study could provide a greater
perceived psychological restoration experience than the others [60].
4.4. The Relationships between Restorative Perception of Environment and Physiological and
Psychological Restoration
The reductions in SBP, DBP, and HR as well as the increments in ROS, SVS, and
WEMWBS measured in the three forests may reflect the restorative capacity of forest envi-
ronments. Additionally, the results of the physiological and psychological changes were
significantly positive correlated with the PRS and the four dimensions of the PRS. These
findings indicate that a higher perceived restoration assessment in the green environments
and the significant correlations with the perceived level of restoration in these areas are
consistent [61]. To a certain extent, this conclusion enriches the evidence of the meaning
of perception of nature’s effect on health. Combining environmental characteristic assess-
ment with changes in the physiological and psychological response will help us to fully
understand the restorative effect of greenness and the mechanisms that benefit from it. In
addition, it is worth noting that the result of our study showing correlation is significant,
but the correlation coefficient is weak. To some degree, it means that the correlations are
not strong overall.
4.5. Limitations
The study investigated the relationship between the perceived restorative power of the
environment and the physiological and psychological restoration effects in young people
of different types of forests. The results of our study confirm previous findings that forest
environments have more positive impacts on the physiological and psychological charac-
teristics of the subjects than urban environments and provide a novel exploration of the
forest’s restorative effects. Nevertheless, there are some limitations in this study. First, we
only explored the restoration effects of a short-term forest exposure on the participant’s
health but did not examine the sustainability of the restorative effects. It is necessary to
examine the duration of the forest exposure’s impacts by specific follow-up assessments.
Second, only university students were involved in this study. Future studies should explore
how forest exposure influences subjects of different socio-demographic backgrounds. Third,
this study was carried out in summer, and the change of season is an important factor
for forest landscapes and environments. Thus, it is important to examine how different
seasons will affect the physiological and psychological parameters of the subjects. Fourth,
the physiological measurements that were used had some limitations, for example, heart
rate can be influenced by many different factors (including walking). Fifth, the extensive
Int. J. Environ. Res. Public Health 2021, 18, 12224
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nature of the task might have influenced the results to some degree as all participants
completed three questionnaires three times. In general, future research needs to consider
the restorative effects of different natural environments with different characteristics of
landscape and environments on subjects with special needs or preferences.
5. Conclusions
We examined the relationship between the restorative perception of the environment
assessed via the Perceived Restoration Scale (PRS) and the physiological and psychological
restoration achieved by experience of the forest environment. Results showed significant
differences in the assessment of the restorative perception of the three types of forests, with
the highest level in the mixed forest, followed by the coniferous forest and the deciduous
forest. In addition, all types of forests had a stronger restorative effect than the urban
environment did, as assessed by reductions in SBP, DBP, and HR and increments in ROS,
SVS, and WEMWBS. We found significant decreases in blood pressure and heart rate and
increases in SVS in the mixed forest, while ROS and WEMWBS significantly improved in
the coniferous forest, which suggests that forest types and tree species composition are
closely associated with forest therapy potential. In addition, physiological and psychologi-
cal changes were significantly positively correlated with the PRS and the four dimensions
of the PRS. These findings indicate that a higher perceived restoration experience in the
green environments and the significant correlations with the perceived level of restoration
in these areas are consistent. Exploring the differences in the restoration effects of different
forest types can effectively support the design and management of future healing forest en-
vironments. These findings provide practical evidence for forest therapy that can maximize
the restorative effects of forests.
Author Contributions: Conceptualization, Q.L., J.L. and X.W.; experimental design, Q.L.; data acqui-
sition, Q.L., Y.L., C.A., X.F., Y.H. and H.Z.; methodology, Q.L., J.L. and X.W.; writing—original draft
preparation, Q.L.; writing—review and editing, Q.L., J.L. and G.Z.; visualization, Q.L; supervision,
J.L. and X.W. All authors have read and agreed to the published version of the manuscript.
Funding: This study was supported by the Beijing Municipal Science and Technology Commission:
Research and Demonstration of Key Technology of National Park System Construction around Beijing
(grant number Z161100001116084).
Institutional Review Board Statement: The study was conducted according to the guidelines of
the Declaration of Helsinki and approved by the Ethics Committee of the Department of Psychol-
ogy, School of Humanities and Social Sciences, Beijing Forestry University (Z161100001116084,
24 March 2021).
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.
Data Availability Statement: No publicly archived datasets, analyzed or generated, were used in
this study.
Acknowledgments: We wish to acknowledge the help provided by the 30 participants who took part
in the experiment. We also thank Jianping Wu for technical assistance during the research. Finally,
thanks to the staff of Mangshan National Forest Park for their support and help for this study.
Conflicts of Interest: The authors declare no conflict of interest.
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