Assessment of Winter Indoor Humiture and Spatial Optimization of Rural Residential Buildings in Mengda National Nature Reserve, China

Abstract

The development of global nature reserves is currently in a rapid growth phase. One of the key challenges in establishing nature reserves is balancing environmental protection with rural residential development within these areas, where housing plays a crucial role in the built environment. Successful residential architecture in nature reserves typically meets residents’ diverse needs and environmental protection requirements by considering regional ecology, culture, economic conditions, natural environment, indoor thermal comfort, and energy consumption. This study examines rural residential buildings in the Mengda National Nature Reserve (MNNR) under cold climate conditions in Western China. Through surveys, architectural mapping, and thermal–humidity environment assessment of typical residential buildings across multiple rural communities within the nature reserve, this research explores possibilities for improving indoor thermal comfort in nature reserve residential buildings. Combined with local climate adaptability and architectural design characteristics, this study proposes rational spatial improvement strategies. This study explores climate-adaptive design in the MNNR, integrating passive solar energy and sustainable heating. It proposes spatial strategies to reduce energy use and enhance thermal comfort. The research findings provide a valuable reference for the spatial optimisation of rural residential construction in nature reserves under similar climatic conditions.

1. Introduction

Rural communities are prevalent within nature reserves worldwide, making the balance between ecological protection and the rural living environment improvement a widely discussed issue. The special ecological protection requirements in nature reserves demand that community residential buildings meet both green construction and environmental protection needs [1,2,3,4]. These requirements necessitate that the design and construction of community residential buildings gradually achieve low-energy consumption and reduced carbon emissions. In renovating and spatially optimizing existing community residential buildings, multiple factors must be considered, including natural ecology, cultural characteristics, economic development level, and regional features. There is widespread agreement that using local and natural building materials while employing scientific climate-adaptive design strategies to enhance indoor thermal comfort can both ensure comfort and promote both energy conservation and quality of life [5,6,7,8,9]. Optimizing energy use in residential buildings within nature reserves plays a crucial role in supporting global sustainable energy development, as it contributes to a reduction in overall energy consumption and carbon footprints while preserving local ecosystems [10,11,12].

In recent years, the study of indoor thermal environments in residential buildings has gradually become a research hotspot. Zheng et al. [13] studied the summer indoor thermal environment of traditional wooden residences by selecting a typical dwelling in Sishui Town, Longsheng. They tested summer thermal environment parameters and analyzed the indoor temperature and thermal stability characteristics of traditional wooden dwellings in northern Guangxi’s mountainous areas, considering factors such as wood properties and construction methods, and proposed corresponding optimization suggestions. The spatial layout of traditional wooden houses in the mountainous areas of northern Guangxi is good, and their main residential buildings can create a relatively stable indoor thermal environment in summer. Shi et al. [14] studied traditional Tujia residences in Jiangkou County, focusing on indoor thermal environment. After summer measurements, they proposed improvements to the building envelope. They used software modeling to compare energy consumption and indoor temperature changes before and after optimization, ultimately achieving both improved thermal comfort and reduced energy consumption. Liu et al. [15] conducted research on traditional stilted houses in southwestern Hubei, measuring the thermal environment parameters of 208 houses across the winter and summer seasons and surveying 387 residents. They constructed a thermal comfort model to determine thresholds, evaluated typical residences, and proposed optimization directions for winter insulation and summer heat prevention. The indoor thermal environment of residential buildings’ impact on night ventilation was researched. The indoor air and average radiation temperatures both decrease with the adoption of night ventilation, with these temperatures decreasing with an increase in the daily temperature range [16]. Kubota evaluated the effects of different natural ventilation strategies on the indoor thermal environment for Malaysian terraced houses. It can be obtained from the test that night ventilation can provide better thermal comfort for occupants in Malaysian terraced houses compared with the other ventilation strategies in terms of operative temperature [17]. The indoor thermal environment and the residents’ thermal comfort in Tibet were investigated, with on-site environmental parameter measurements and a simultaneous survey using a subjective thermal comfort questionnaire. The acceptable thermal comfort temperature range for residential buildings in this area has been established [18].

Research on indoor thermal comfort in rural residential buildings is extensive, particularly focusing on impoverished areas and plateau regions [19,20,21,22]. Li et al. [23] proposed converting existing new buildings into low-cost, easily maintained passive solar heating buildings, using DeST-h software for simulation analysis. Zhang et al. [24] conducted field research on farming and pastoral residential buildings in central and western Inner Mongolia, measuring winter indoor temperatures and thermal comfort. Shao et al. [25] used DesignBuilder to simulate the heating energy consumption of typical building models. Cui et al. [26] simulated the effects of different renovation measures on typical rural houses using DesignBuilder software. Dong et al. [27] evaluated the indoor thermal comfort of rural residents in Linshui City, obtaining thermal neutral temperatures and analyzing thermal adaptation behaviors.

In recent years, many scholars have conducted in-depth research on improving indoor thermal comfort [28,29,30,31,32,33]. Liu et al. [34] analyzed and evaluated winter indoor thermal environments through measured data, clarifying the insulation effects of building envelopes, elevated floors, and lofts, and the pros and cons of fire pit heating. Jin et al. [35] analyzed thermal environments under existing heating modes and proposed optimization strategies, such as south-facing sunrooms, energy-efficient suspended kang (“kang” is a traditional heated bed commonly found in Northern Chinese homes), and wind energy heating systems. Borgkvist [36] suggested that using passive energy-efficient building techniques improves indoor thermal comfort in Nepal, such as the use of insulation and passive solar heating. Bodach [37] pointed out that traditional buildings use solar passive measures to achieve thermal comfort conditions. The local climate conditions and traditional construction techniques and materials should be considered to improve indoor thermal comfort. Kim et al. [38] analyzed the thermal response of precast concrete sandwich walls with different steel connectors for construction in cold regions. Basudev et al. [39] analyzed the regional differences in the indoor thermal environment of traditional Nepalese houses in winter, and the results showed that traditional buildings have better adaptability to the local climate environment.

Improving thermal comfort is a key goal for rural housing in economically disadvantaged cold regions. Optimizing building form and enhancing heating systems are essential strategies to improve indoor conditions during winter. The Qinghai–Tibet Plateau has unique geographical and climatic characteristics. Winter temperatures typically range from −10 °C to −20 °C, with some areas experiencing even lower temperatures. Annual precipitation remains below 400 mm, with minimal winter rainfall, classifying it as a cold–arid region. Under these conditions, temperature and humidity are the primary factors affecting indoor thermal comfort.

This study focuses on four typical rural housing types in the Mengda Nature Reserve of the Qinghai–Tibet Plateau, analyzing their indoor temperature and humidity variations in winter. The primary objective is to explore how building optimization and heating improvements can enhance thermal comfort while balancing environmental conservation and residential needs. This study consists of four main components. First, it documents four types of Zhuangkuo houses through field surveys and mapping. Second, it measures the winter indoor temperature and humidity in five representative buildings. Third, it employs peak–valley analysis to examine temperature and humidity patterns across different building forms. Fourth, it proposes optimization strategies, including spatial layout adjustments, heating system improvements, and better insulation materials. Unlike conventional conservation strategies that rely on relocating residents to minimize human impacts, this study introduces an alternative approach—integrating rural dwellings into the ecological framework of conservation areas. By optimizing vernacular architectural design, we propose a built-environment strategy that enables residential buildings to become part of the protected landscape, rather than external disruptions to it. This method fosters harmonious coexistence between communities and natural reserves, offering a sustainable model that reconciles human habitation with environmental conservation.

2. Research Object and Research Scheme

2.1. Overview of the Nature Reserve

MNNR is located in the eastern region of the Qinghai–Tibet Plateau, specifically within Xunhua County, Haidong City, Qinghai Province, China [40] (Figure 1). The Qinghai–Tibet Plateau is characterized by a cold, arid climate with intense solar radiation. It experiences low annual average temperatures, significant diurnal temperature variations, scarce precipitation concentrated in the summer months, and long, harsh winters. The central plateau predominantly features arid and semi-arid climates, while the eastern and southern edges receive slightly more precipitation due to monsoonal influences. These climatic conditions have shaped the region’s unique ecological environment and human settlement patterns. Compared to the high-altitude regions of the Qinghai–Tibet Plateau, where the climate is frigid, the annual average temperature is below 0 °C, and annual precipitation is less than 400 mm. MNNR, situated in the eastern part of the plateau, exhibits distinct seasonal climate variations. It is characterized by long, cold, and dry winters; short, warm, and humid summers; and significant temperature fluctuations. Additionally, MNNR receives abundant sunshine, with approximately 2500 h of annual sunlight and strong ultraviolet radiation, providing ample solar energy resources.

The Yellow River crosses the reserve and bisects the MNNR, with a minimum elevation of 1780.0 m, followed by a gradual rise in terrain to the north and south, reaching a maximum elevation of 4183.6 m. The MNNR covers a total area of 17,290 hectares, comprising a core zone, a buffer zone, and an experimental zone. Specifically, 17,274.7 hectares consists of land, while 15.3 hectares is water bodies, with a forest coverage rate of 77.4%. The MNNR is home to seven administrative villages, Dazhuang, Hanping, Tashapo, Muchang, Suotong, Zhuantang, and Amacha, with a total of 651 households and 3551 residents, giving it a population density of 14 people per square kilometer.

Table 1. Statistics on rural communities, population, ethnicity, and townships in the MNNR.

Rural Community	Population	Ethnic	Township
Dazhuang	1766	Salar	Qingshui
Tashapo	339	Salar	Qingshui
Hanping	263	Salar	Qingshui
Muchang	481	Salar	Qingshui
Suotong	179	Salar	Qingshui
Zhuantang	268	Tibetan	Qingshui
Amacha	255	Tibetan	Qingshui

shows the details, mapped by the author based on data provided by the Village Office of the Housing and Urban–Rural Development Bureau of Methodist Salar Autonomous County [40,41].

Indoor thermal comfort in winter is influenced by multiple factors, including air temperature, humidity, air velocity, radiant temperature, metabolic rate, and activity level. However, in the Qinghai–Tibet Plateau, due to its unique geographical and climatic conditions, temperature and humidity play a decisive role in determining indoor comfort.

The study area has an average altitude of 3000 m, with winter temperatures typically ranging from −10 °C to −20 °C and, in some areas, even lower. Precipitation is minimal, and relative humidity often falls below 30% during winter. These extreme conditions mainly affect thermal comfort in two key ways:

First, the temperature impact: Severe cold makes indoor heating a top priority. If indoor temperatures are too low, they not only reduce comfort but also pose health risks such as colds, arthritis, and even chronic conditions specific to high-altitude environments.

Secondly, the humidity impact: Dry air can lead to skin irritation, respiratory discomfort, and may exacerbate altitude sickness. Additionally, low humidity accelerates moisture evaporation, making the perceived temperature even lower and further affecting overall thermal comfort.

In a region with harsh winters, dry air, and limited heating resources, regulating temperature and humidity is essential for maintaining livable indoor conditions and safeguarding residents’ health. This study focuses on these two variables to assess their impact on thermal comfort under such climatic conditions. It is important to note that this does not imply that other factors, such as air velocity or radiant temperature, are insignificant; rather, the choice of variables is based on the region’s climatic characteristics, practical concerns of local residents, and the feasibility of research implementation.

According to the zoning plan of the MNNR, all seven villages are located within the experimental zone and are distributed along the small watershed valleys within the MNNR. There are five major small watersheds in the MNNR: Lachun, Dazhuang, Hanping, Muchang, and Dadong. These watersheds house all rural communities and are key areas where agricultural fields, rivers, roads, forests, and wildlife converge. The rugged terrain, narrow valleys, and underdeveloped terraces limit the usable valley area, making these watersheds not only focal points of human activity but also ecologically vulnerable zones. Studies have shown that the nested relationship among “small watershed-settlement-courtyard” landscapes forms a critical interface, influencing ecological conservation in protected areas. The watersheds play a dominant role in maintaining ecosystem stability at the interface. Settlements, as core units within the watershed, significantly contribute to ecosystem stability, while residential courtyards serve as the fundamental units impacting the ecological balance at this interface. Examining residential courtyards and buildings is, thus, crucial for understanding the relationship between local residents and environmental conservation within the MNNR.

2.2. Analysis of Residential Buildings

Historically, the Mengda area boasted abundant forest resources, enabling local residents to construct dwellings using a combination of timber, stone, and adobe. This gave rise to a distinctive type of fortified residential architecture known as Zhuangkuo dwellings [40] (Figure 2). During the coldest month of winter on the Qinghai–Tibet Plateau, the author investigated the residential building characteristics in the three largest villages within MNNR—Mengda Dazhuang Village, Tashapo Village, and Zhuantang Village. A total of 254 “zhuangkuo” (fortified residential complexes) were surveyed on site, including 119 in Mengda Dazhuang Village, 70 in Tashapo Village, and 65 in Zhuantang Village. The survey revealed that “zhuangkuo” is a castle-like vernacular dwelling enclosed by high walls. Its layout is typically rectangular, covering an area of approximately 600 square meters, and consists of four main elements: the entrance gate, perimeter walls, buildings, and a courtyard.

Based on the spatial arrangement of buildings and courtyards, Zhuangkuo dwellings can be categorized into four types: quadrangle courtyards, U-shaped courtyards, L-shaped courtyards, and single-sided houses. The architectural styles include three main forms: “U”-shaped, “L”-shaped, and linear (Figure 2). The linear form further divides into two subtypes: with eaves and without eaves. This unique architectural style reflects the adaptation of local communities to the region’s natural environment and resource availability, while also embodying cultural and historical significance. Based on the distribution characteristics of residential building types within “zhuangkuo” courtyards and considering the diversity of heating methods, this study selected five “zhuangkuo” residences from different villages in MNNR for winter indoor temperature and humidity testing.

2.3. Methodology

This study employed a mixed methods research design, integrating both qualitative and quantitative approaches to examine vernacular dwellings in the MNNR.

The qualitative approach is case selection and classification. A total of 254 vernacular courtyard dwellings (Zhuangkuo dwellings) in MNNR were mapped and categorized based on spatial configuration. The classification process involved on-site measurements, spatial mapping using GIS, and typological analysis. Four main residential forms were identified: U-shaped, L-shaped, single line with eaves, and single line without eaves.

For the quantitative analysis, five representative dwellings from these four catego-ries were selected for systematic temperature and humidity monitoring during the coldest winter months. Temperature and humidity sensors (HOBO MX1101, accuracy: ±0.2 °C, ±3% RH. This instrument is manufactured by Onset Computer Corporation, which is headquartered in Bourne, MA, USA) were installed at three key locations in each dwelling: main hall kang, side-room kang, and corridor. Sensors recorded data every 120 min for 60 consecutive days, generating a dataset of approximately three data points per dwelling. The collected data were processed using mean temperature variation (AT), daily fluctuation range, and thermal stability index (TSI = Tmax − Tmin). Additionally, linear regression models were applied to examine the correlation between spatial form and thermal comfort.

This structured methodology ensures a robust assessment of how different vernacular dwelling forms influence indoor thermal comfort during winter.

2.3.1. Test Equipment and Methods

To assess the ability of rural residential buildings in MNNR to withstand low winter temperatures, we conducted temperature and humidity testing during the coldest month of winter. The testing period spanned from 11 January to 21 January 2020, measuring both indoor and outdoor air temperature and humidity.

Following the guidelines of “JGJ/T347-2014 Standard for Thermal Environmental Testing of Buildings” [42], a HOBO U23-001 data logger (This instrument is manufactured by Onset Computer Corporation, which is headquartered in Bourne, MA, USA) was used to record outdoor air temperature and humidity, placed under the eaves of the buildings. Indoor temperature and humidity measurements were recorded using HOBO U23-002 and HOBO U23-003 for the “zhengfang” (main house) and “xiangfang” (side rooms), respectively. Indoor measurement points were set at heights of 0.6 m, 1.1 m, and 1.7 m. An SW-DA laser distance meter was used to measure the dimensions of each residential building, and floor plans were drawn accordingly.

The testing parameters and instrument specifications are listed in

Table 2. Temperature and humidity measurement instruments.

Instrument Model	Measurement Parameters	Accuracy	Measurement Range	Resolution
HOBO U23-001	Outdoor Air Temperature	±0.21 °C (0~50 °C)	−40–70 °C	0.02 °C (25 °C)
	Outdoor Relative Humidity	±2.5%	0–100%	0.03%
HOBO U23-002	Indoor Main Room Air Temperature	±0.21 °C (0~50 °C)	−20–70 °C	0.024 °C (25 °C)
	Indoor Main Room Relative Humidity	±3.5% (25~85%)	15–95%	0.07% (25 °C)
HOBO U23-003	Indoor Side Room Air Temperature	±0.21 °C (0~50 °C)	−20–70 °C	0.024 °C (25 °C)
	Indoor Side Room Relative Humidity	±3.5% (25~85%)	15–95%	0.07% (25 °C)
SW-DA	Distance Measurement	1.5 mm	0–50 m	0.001 m

, with data sampled at 20 min intervals. Prior to testing, the instruments were calibrated through a pre-test to ensure the scientific validity and reliability of the data. A designated pre-test site was selected, where multiple identical instruments recorded data simultaneously. The deviation between each instrument’s reading and the average value had to fall within the instrument’s precision range, ensuring that any measurement error stemmed from the device’s inherent accuracy rather than external factors. Measurement points were positioned to avoid disrupting residents’ daily activities. For temperature and humidity measurement, the upper accuracy limits of the HOBO series instruments were simulated. Temperature accuracy was adjusted from ±0.21 °C to ±0.3 °C, and humidity accuracy from ±2.5%/±3.5% to ±4%. The results showed that indoor and outdoor temperature fluctuations remained within ±0.5 °C, without altering the overall trend. Humidity variations stayed within ±2%, with consistent patterns observed in the main house, side rooms, and outdoor areas. For distance measurements, even with a maximum error of 1.5 mm, the SW-DA laser rangefinder had a negligible impact on floor plan accuracy and subsequent thermal analysis, as the building dimensions were much larger than this margin of error. Therefore, the selected instruments meet the research requirements, ensuring reliable data.

2.3.2. Test Subject

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Test Subject One

Test subject one consists of a combination of the U courtyard layout (Figure 2a) and the linear layout without overhanging eaves (Figure 2c). The U courtyard layout employs a heating system combining two kang and a stove, while the linear layout uses a single kang and a stove. Test subject one is a residential dwelling located in Dazhuang Village of Dazhuang Valley within the MNNR. This residence follows the traditional courtyard housing layout and is constructed using earth and timber materials. In terms of climate conditions, the annual total solar radiation in Xunhua County is about 5800–6500 MJ/m², making it a high-solar-energy area. At a height of 70 m, the average wind speed is around 4.5–5.5 m/s, indicating moderate wind energy potential. These climate characteristics provide an important environmental context for analyzing the ability of rural houses in the reserve to withstand winter cold. The buildings surrounding the courtyard include the main living quarters, kitchen, garage, bathroom, and storage room. The living quarters comprise two types of structures (Figure 3): First, a 42-square-meter U-shaped dwelling serving as the primary residence, which accommodates the family’s main winter activities, including dining, recreation, rest, and sleeping. The interior is furnished with kang (heated bed-platform), tables, chairs, stove, and cabinets to facilitate various functions. Second, a 21-square-meter linear dwelling serves as the wing room, primarily used for daytime and nighttime rest during winter, equipped with kang, cabinets, and chairs. The residence employs multiple heating methods for winter. The U-shaped dwelling utilizes a combined heating system of “stove and double kang”, where kang represents a unique traditional Chinese heated bed-platform widely used in northern regions, serving both as a sleeping surface and heating system. The linear dwelling relies on a single kang for winter space heating. Within these two residential structures, the authors established three temperature testing points (Figure 3). The first point is located on the kang table in the U-shaped dwelling, the second in the outdoor corridor space of the main house, and the third on the kang cabinet in the linear dwelling.

The temperature test results for test subject one’s residential building are shown in Figure 4. It shows the temperature changes over time in the main hall kang, side-room kang, and corridor of test subject one, clearly illustrating the temperature fluctuations in each area. The data indicate that during the testing period, the average temperatures in the main house interior, wing room interior, and outdoor corridor were 11 °C, 9.3 °C, and −0.04 °C, respectively. Using the peak–valley method (subtracting the minimum value from the maximum value among all measurements), the temperature fluctuation ranges were 7.5 °C, 3.9 °C, and 16.3 °C, respectively. Comparing the temperature variation curves across multiple test points reveals the following: the main house interior maintained relatively stable temperatures, generally ranging between 5 °C and 15 °C, with a maximum temperature of 15.3 °C, utilizing a combination of fire-heated kang and stove for heating. This suggests that the main house interior temperature was minimally affected by external conditions. The wing room interior showed similar temperature patterns but maintained slightly lower temperatures overall, with a maximum of 12.1 °C, using a single fire-heated kang, indicating somewhat inferior thermal performance compared to the main house. The outdoor corridor exhibited the most dramatic temperature variations, particularly at night, when temperatures fell below −5 °C, demonstrating significant influence from diurnal temperature variations.

The relative humidity test results for test subject one’s residential building are presented in Figure 5. It presents the humidity changes over time in the main hall kang, side-room kang, and corridor of test subject one, showing the variation in humidity levels throughout the day. The data indicate that during the testing period, the average humidity levels in the main house interior, wing room interior, and outdoor corridor were 41%, 39%, and 50%, respectively. Using the peak–valley method (subtracting the minimum value from the maximum value among all measurements), the humidity fluctuation ranges were 8%, 5%, and 26%, respectively. Comparative analysis of humidity variation curves across test points reveals that the main house interior maintained relatively stable humidity levels, showing a slight downward trend from approximately 45% in the morning to 38% in the evening, followed by a minor increase. The wing room interior demonstrated consistent humidity levels, maintaining a narrow range between 38% and 42%. The outdoor corridor exhibited the most significant humidity variations, starting with higher levels of approximately 60% in the morning, decreasing to a minimum of approximately 33% around 18:55, then gradually increasing to reach a peak of approximately 60% by 06:55 the following morning. Overall, the outdoor corridor humidity levels showed substantial influence from external environmental conditions, displaying distinct variation patterns, while indoor environments maintained relatively stable humidity levels with minimal fluctuations. Furthermore, both the main house and wing room interiors experienced slight humidity decreases during nighttime, possibly correlating with nocturnal temperature reductions and corresponding decreases in air moisture content.

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Test Subject Two

Test subject two includes the linear layout with overhanging eaves (Figure 2b) and the linear layout without overhanging eaves (Figure 2c). Both residential buildings utilize a heating system consisting of a single kang and a stove. Test subject two is a residential dwelling located in Dazhuang Village of Dazhuang Valley within the MNNR. This residence follows the traditional courtyard layout and is constructed using earth and timber materials. Based on climate characteristics, Xunhua County receives annual total solar radiation of 5800–6500 MJ/m², ranking among the highest in the country. At 70 m, the average annual wind speed is about 4.5–5.5 m/s, offering moderate wind energy potential. These conditions provide a key environmental basis for assessing the winter cold resistance of rural homes in the nature reserve. The buildings surrounding the courtyard include the main living quarters, kitchen, garage, bathroom, and storage room. The main residential structure follows a linear layout (Figure 6), comprising, first, a 30-square-meter main house that accommodates the family’s primary winter activities, including dining, recreation, rest, and sleeping. The interior is furnished with kang, tables, chairs, stove, cabinets, and chests for various functions. Second is a 30-square-meter wing room primarily used for daytime and nighttime rest during winter, equipped with kang, cabinets, chairs, and a dressing table. The residence employs multiple heating methods for winter. The main house uses a combined system of “single stove and kang” for winter space heating, while the wing room relies solely on a single kang for heating. Within these two residential structures, the authors established three temperature testing points (Figure 6). The first point is located on the tea table in the main house, the second in the outdoor corridor space of the main house, and the third on the kang cabinet in the wing room.

The temperature test results for test subject two’s residence are presented in Figure 7. During the testing period, the average temperatures in the main house interior, wing room interior, and outdoor corridor were 10.6 °C, 9.4 °C, and −5.5 °C, respectively. The peak–valley analysis revealed temperature fluctuation ranges of 8.2 °C, 4.4 °C, and 16.6 °C, respectively. Temperature curve comparisons across test points demonstrate that the main house interior maintained relatively stable temperatures between 8 °C and 12 °C, achieving the highest average temperature with a maximum of 15 °C. The wing room interior exhibited similar temperature patterns but maintained slightly lower temperatures overall. In contrast, the outdoor corridor showed significantly greater temperature fluctuations compared to indoor spaces.

The humidity test results for test subject two’s residence are shown in Figure 8. During the testing period, the average humidity levels in the main house interior, wing room interior, and outdoor corridor were 40%, 39%, and 49%, respectively. The peak–valley analysis revealed humidity fluctuation ranges of 8%, 5%, and 30%, respectively. The main house and wing room interiors exhibited remarkably similar humidity patterns, though the wing room showed slightly smaller variations. The outdoor corridor demonstrated significant humidity fluctuations ranging between 30% and 60%, with a decreasing trend from 08:55 to 18:55 and an increasing trend from 18:55 to 06:55.

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Test Subject Three

Test subject three consists of the linear layout without overhanging eaves (Figure 2c) and the L-shaped layout (Figure 2d). The linear layout employs a heating system combining a kang and a stove, while the L-shaped layout incorporates a kang, a stove, and a solar-heated sunroom. Test subject three is a residential dwelling located in Tashapo Village of Muchanggou Valley within the MNNR. This residence represents a modern interpretation of the courtyard housing form, constructed using brick and concrete materials. In terms of climate conditions, Xunhua County receives 5800–6500 MJ/m² of solar radiation annually, significantly above the national average. At 70 m, the average wind speed is 4.5–5.5 m/s, indicating moderate wind energy potential. These factors form a critical environmental basis for evaluating how well rural homes in the reserve withstand winter cold. The buildings surrounding the courtyard include the main living quarters, kitchen, garage, bathroom, and storage room. The living quarters comprise two types (Figure 9): First, a 30-square-meter L-shaped dwelling serves as the main house, which accommodates the family’s primary winter activities, including dining, recreation, rest, and sleeping. The interior is furnished with kang, tables, chairs, stove, cabinets, and chests for various functions. Second, a 36-square-meter linear dwelling serves as the wing room, primarily used for winter daytime and nighttime rest or guest accommodation, equipped with kang, cabinets, and chairs. The residence employs multiple heating methods for winter. The L-shaped main house utilizes a combined system of “single kang and stove” for winter space heating and features a passive solar corridor. The linear wing room uses a combination of “kang, stove, and electric heater” for winter space heating. Within these two residential structures, the author established three temperature testing points (Figure 9). The first point is located on the tea table in the L-shaped main house, the second under the passive solar corridor outside the main house, and the third on the tea table in the linear wing room.

The temperature test results for test subject three’s residence are illustrated in Figure 10. During the testing period, the average temperatures in the main house interior, wing room interior, and outdoor corridor were 10.6 °C, 9.2 °C, and 1.8 °C, respectively. The peak–valley analysis indicated temperature fluctuation ranges of 8.2 °C, 5.6 °C, and 17.6 °C, respectively. Temperature curve comparisons show that both the main house and wing room interiors maintained similar temperature patterns, predominantly ranging between 8 °C and 12 °C, demonstrating relatively stable thermal conditions. The outdoor corridor exhibited more pronounced temperature variations, rising from approximately −5 °C at 08:55, reaching peak temperatures between 12:00 and 12:59, leading to a gradual decline, reflecting significant weather-dependent temperature fluctuations.

The humidity test results for test subject three’s residence are illustrated in Figure 11. During the testing period, the average humidity levels in the main house interior, wing room interior, and outdoor corridor were 40%, 39%, and 43%, respectively. The peak–valley analysis indicated humidity fluctuation ranges of 8%, 16%, and 25%, respectively. The main house interior maintained minimal fluctuations throughout the testing period, without extreme humidity variations. The wing room interior showed slightly larger fluctuations, with notable variations between 19:55 and 23:55. The outdoor corridor exhibited pronounced humidity changes, demonstrating significant rapid increases and decreases with substantial variation amplitude.

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Test Subject Four

Test subject four features a combination of the U courtyard layout (Figure 2b) and the linear layout without overhanging eaves (Figure 2c). The U courtyard layout employs a heating system with two kang and a stove, while the linear layout uses a single kang and a stove. Test subject four is a residential dwelling located in Tashapo Village of Muchanggou Valley within the MNNR. This residence follows the traditional courtyard layout and is constructed using earth and timber materials. Considering climate characteristics, Xunhua County has an annual total solar radiation of 5800–6500 MJ/m², well above the national average. The average wind speed at 70 m is 4.5–5.5 m/s, suggesting moderate wind energy potential. These conditions provide essential environmental data for assessing the winter cold resistance of rural homes in the reserve. The buildings surrounding the courtyard include the main living quarters, kitchen, bathroom, and storage room. The living quarters comprise two types (Figure 12). First, a 27-square-meter U-shaped dwelling serves as the main house, which accommodates the family’s primary winter activities, including dining, recreation, rest, and sleeping. The interior is furnished with kang, tables, chairs, stove, cabinets, and chests for various functions. Second, a 17-square-meter linear dwelling serves as the wing room, primarily used for daytime and nighttime rest during winter, equipped with kang, bed, cabinets, and chairs. The residence employs multiple heating methods for winter. The U-shaped main house utilizes a combined system of “double kang and stove” for winter space heating, while the linear wing room uses a combination of “stove and single kang” for heating. Within these two residential structures, the authors established three temperature testing points. The first point is located on the kang table in the U-shaped main house, the second in the outdoor corridor of the main house, and the third on the tea table in the linear wing room.

The temperature test results for test subject four’s residence are shown in Figure 13. During the testing period, the average temperatures in the main house interior, wing room interior, and outdoor corridor were 7.7 °C, 8.9 °C, and 1.6 °C, respectively. The peak–valley analysis revealed temperature fluctuation ranges of 8.1 °C, 8.6 °C, and 18.6 °C, respectively. Temperature curve comparisons indicate that the main house interior maintained relatively higher temperatures throughout the day, ranging between 7 °C and 15 °C. The wing room interior exhibited slightly lower temperatures overall, ranging between 6 °C and 10 °C, while the outdoor corridor recorded the lowest temperatures, ranging between −2 °C and −8 °C.

The humidity test results for test subject four’s residence are presented in Figure 14. During the testing period, the average humidity levels in the main house interior, wing room interior, and outdoor corridor were 40%, 41%, and 48%, respectively. The peak–valley analysis revealed humidity fluctuation ranges of 8%, 18%, and 23%, respectively. The main house interior maintained stable humidity levels throughout the testing period.

(5)

Test Subject Five

Based on differences in architectural layout and heating methods, test subject five consists of a combination of the linear layout with overhanging eaves (Figure 2b) and the linear layout without overhanging eaves (Figure 2c). The linear layout with overhanging eaves utilizes a combination of a single kang (heated bed), a stove, and a sun-heated corridor for warmth, while the linear layout without overhanging eaves relies on a combination of a single kang and a stove for heating. Test subject five is a residential dwelling located in Tashapo Village of Muchanggou Valley within the MNNR. This residence follows the traditional courtyard layout and is constructed using earth and timber materials. From a climate analysis perspective, Xunhua County has two notable features: first, its annual solar radiation reaches 5800–6500 MJ/m², nearly twice the national average; second, the average wind speed at 70 m remains between 4.5 and 5.5 m/s, offering moderate wind energy potential. These two climate factors serve as key data for evaluating the winter cold resistance of rural homes in the nature reserve. The buildings surrounding the courtyard include the main living quarters, kitchen, garage, bathroom, and storage room. The main residential structure follows a linear layout, comprising the main house and wing room (Figure 15). The main house covers 50 square meters and accommodates the family’s primary winter activities, including dining, recreation, rest, and sleeping. The interior is furnished with kang, tables, chairs, stove, cabinets, and chests for various functions. The wing room is a 10-square-meter linear dwelling primarily used for daytime and nighttime rest during winter, equipped with kang, cabinets, and tea table. The residence employs multiple heating methods for winter. The main house uses a combined system of “single kang and stove” for winter space heating and features a passive solar corridor, while the wing room uses a combination of “stove and single kang” for heating. Within these two residential structures, the authors established three temperature testing points (Figure 15). The first point is located on the kang table in the main house, the second under the passive solar corridor outside the main house, and the third on the tea table in the wing room.

The temperature test results for test subject five’s residence are presented in Figure 16. During the testing period, the average temperatures in the main house interior, wing room interior, and outdoor corridor were 10.2 °C, 14 °C, and 2.5 °C, respectively. The peak–valley analysis showed temperature fluctuation ranges of 8.1 °C, 9.6 °C, and 14.6 °C, respectively. Temperature curve comparisons demonstrate that the main house interior maintained relatively stable temperatures throughout the day, predominantly ranging between 6 °C and 15 °C. The wing room interior followed similar temperature patterns but maintained slightly higher temperatures overall, ranging between 10 °C and 19 °C, with a maximum temperature of approximately 19 °C. The outdoor corridor exhibited the most significant temperature variations, with extreme diurnal temperature differences reaching a minimum of −3.5 °C.

The humidity test results for test subject five’s residence are shown in Figure 17. During the testing period, the average humidity levels in the main house interior, wing room interior, and outdoor corridor were 40%, 43%, and 46%, respectively. The peak–valley analysis demonstrated fluctuation ranges of 8 °C, 14 °C, and 23 °C, respectively.

The reasons for the decrease in indoor temperature in residential areas in the MNNR mainly involve multiple aspects, such as the natural climate, building structure, heating system, and human factors. Due to its high altitude, the annual average temperature in the MNNR is relatively low, with winter temperatures reaching up to −30 °C. At the same time, there is a large temperature difference between day and night, with a brief increase in temperature during the day and rapid loss of heat at night. This directly leads to a decrease in indoor temperature. On the other hand, the insulation performance of traditional building envelope structures in the region is relatively poor compared to modern building materials, and indoor heat is easily dissipated through the walls. Due to poor local economic conditions and infrastructure, the heating system of traditional buildings in the community mainly relies on burning wood and coal through stoves and heated kang beds for heating. Through visits and investigations, it was found that 15–25 kg of firewood is needed daily to maintain a comfortable indoor temperature in the local area. Therefore, this exacerbates the contradiction between ecological protection and living environment in nature reserves.

3. Results and Analysis

This study analyzes temperature and humidity data collected from five test subjects, each featuring different architectural layouts and heating systems. By examining these data, we gain deeper insights into the relationship between building structures, heating methods, and winter environmental conditions, comparing temperature and humidity fluctuations to evaluate the performance of various heating systems and architectural designs.

3.1. Temperature and Humidity Analysis for Each Test Subject

3.1.1. Test Subject One

Temperature Analysis: Test subject one combines traditional “U” and “linear” architectural layouts. The heating system includes double kang beds in the main house, a stove, and a single kang in the side rooms. Temperature readings from the kang tables in the main house and the outdoor corridor show a significant temperature difference. The kang-heated areas maintain a stable and comfortable temperature, whereas the corridor remains much colder, indicating limited heating efficiency in open spaces.

Humidity Analysis: The humidity in the kang area was higher, potentially due to the use of stove heating, which introduces moisture into the air. The outdoor corridor, however, showed lower humidity, likely because of its exposure to external air and the lack of direct heating.

3.1.2. Test Subject Two

Temperature Analysis: This test subject consists of two linear buildings, both heated by a stove and a single kang. Temperature readings from the tea table in the main house and the outdoor corridor indicate that the combination of the stove and kang provides sufficient warmth in the main living area. However, the side rooms remain relatively cold due to the absence of an auxiliary heating system.

Humidity Analysis: Humidity was noted to be higher in the kang areas, which aligns with traditional heating methods that involve a more direct and enclosed heat source. However, the air in the main house was relatively dry in non-heated areas, highlighting the difference in air moisture between the heated and unheated spaces.

3.1.3. Test Subject Three

Temperature Analysis: The residence of test subject three features an L-shaped main house integrating a kang, a stove, and a passive solar-heated corridor. Temperature measurements indicate that the passive solar heating in the corridor enhances overall warmth in the main house, particularly on sunny days. However, additional electric heaters are required in the side rooms to maintain a comfortable temperature alongside the traditional heating methods.

Humidity Analysis: The solar corridor reduced the need for moisture-laden heating in the main house, and the air there was drier, improving the comfort level during the winter. The wing room, depending more heavily on electric heating, had fluctuating humidity levels that depended on the outside weather conditions.

3.1.4. Test Subject Four

Temperature Analysis: In test subject four, the U-shaped building is heated by double kang beds and a stove, while the linear side rooms rely on a single kang and a stove. Temperature data show that the main house remains warm and comfortable, whereas the side rooms remain significantly colder throughout the day. The lower heating efficiency in these spaces is due to the lack of direct heating methods.

Humidity Analysis: Similar to other test subjects, the main house’s humidity levels were notably higher in the kang areas, indicating that traditional heating methods contribute to maintaining warmth as well as moisture. The linear wing room experienced lower humidity levels due to its smaller size and less effective heating.

3.1.5. Test Subject Five

Temperature Analysis: Test subject five consists of a linear main house with a passive solar-heated corridor and a side house without solar features. The combination of kang beds, a stove, and the passive solar corridor in the main house provides optimal warmth. In contrast, the side house, heated only by a stove and kang, exhibits poor insulation performance, particularly during colder periods.

Humidity Analysis: The passive solar corridor played a crucial role in maintaining a balanced humidity level, reducing the need for additional moisture from the stove. On the other hand, the wing room had fluctuating humidity levels depending on the stove’s heat output.

3.2. Analysis Based on Temperature, Humidity, and Other Factors

3.2.1. Temperature Comparisons

Main House vs. Wing Room: Across all test subjects, the temperature in the main house was consistently higher and more stable than in the side rooms, indicating that primary living spaces benefit from better insulation and heat retention. The use of multiple heating systems, such as a combination of kang and stove heating, proved to be more effective in maintaining warmth.

Heating Efficiency: The best heating performance was observed in test subjects one, three, and five, where the main house utilized a combination of kang and stove heating systems, supplemented with solar passive heating in some cases. In contrast, the wing rooms, which often relied on a single kang or stove, had less effective heating, particularly in larger or more exposed spaces.

3.2.2. Humidity Comparisons

Moisture Retention in Heated Areas: Areas heated by kang systems displayed significantly higher humidity levels, suggesting that traditional heating methods, such as the combination of kang and stove, help maintain higher indoor humidity levels, which is beneficial in cold and dry winter conditions.

Effect of Solar Heating: In test subjects three and five, where passive solar heating was implemented, the humidity levels in the main house were lower, reflecting the reduced reliance on moisture-producing heating systems.

3.2.3. Comparative Analysis of Building Forms, Heating Systems, and Heating Efficiency

Building Form: Significant differences in heat distribution were observed between U-shaped layout and linear layout buildings. The U design created a more varied facade, which contributed to better heat retention compared to the linear layout.

Heating Systems: The combination of kang, stove, and passive solar heating proved to be the most effective in maintaining warmth and comfort, as seen in test subjects three and five. The inclusion of electric heaters in the wing rooms of test subject three further contributed to improved temperature control.

Building Size and Area: Larger residences such as those in test subjects one and five, with additional spaces and more advanced heating systems, showed better overall temperature regulation. Smaller wing rooms, regardless of the heating system, struggled to maintain consistent warmth, highlighting the importance of optimizing heat distribution in smaller spaces.

The results from the five test subjects illustrate how building design, heating systems, and environmental conditions influence the indoor climate in winter. The use of combined heating methods, including kang, stoves, and solar corridors, provides better thermal comfort and humidity control. The main house in each test subject typically performed better than the wing room, which often lacked supplementary heating. This study highlights the importance of considering both architectural layout and heating systems in designing energy-efficient and comfortable homes for winter conditions. Future studies could explore optimizing heating systems for smaller rooms and integrating passive solar designs to improve overall energy efficiency and comfort.

4. Discussion

This research reveals important connections between building design, heating strategies, and environmental conditions in the MNNR. Our findings confirm that building size, heating approaches, and architectural form significantly impact indoor thermal environments during winter. The study demonstrates that thoughtful architectural optimization, combined with appropriate heating methods and controlled building dimensions, can substantially improve indoor comfort for residents.

4.1. Inheriting and Optimizing the Geometric Forms of Tradition

The data from the tests on three types of residential building forms discussed earlier indicate that, comparatively, the “U-shaped” building form exhibits more stable temperature fluctuations and provides relatively comfortable indoor conditions. This form holds significant value as the main house (zhengfang) and is recommended as the primary design for main houses in the renovation of residential buildings. Meanwhile, the rectangular zhuangkuo residential form demonstrates environmental advantages, such as fewer heat dissipation surfaces, reduced indoor heat loss, and the ability to shield against cold winds from the northwest. By studying its spatial morphology, it is possible to extract the construction wisdom embedded in its symbiotic relationship with the MNNR, thereby refining representative architectural forms and layouts while optimizing functionality and spatial organization (Figure 18).

Technologically, replacing the traditional earthen–wood structures of rural residences with earth–steel structures can reduce the reliance on timber, optimize the structure of earthen buildings, increase the number of floors, and minimize land usage. Modern rammed-earth techniques and new earthen brick technologies can be employed to enhance the strength and water resistance of earthen materials, thereby improving the overall insulation performance of the buildings, promoting air temperature stabilization. Additionally, optimizing the structure of residential buildings is one approach for improving the indoor thermal environment during winter. Installing double-glazed windows can further enhance insulation and reduce heat loss (Figure 18).

4.2. Maximizing the Use of Solar Energy to Improve Indoor Comfort in Residential Buildings

Based on the results of the tests, adopting passive sunspaces to improve indoor thermal environments is a feasible strategy, but further functional and spatial optimizations of the architectural form are required. Considering the issues of environmental pollution and the high-energy consumption caused by coal-fired heating during winter in the MNNR, this study proposes utilizing solar energy as a clean energy source to enhance the indoor thermal environment.

Firstly, the optimization of passive sunspaces and the addition of passive solar courtyards can improve the overall insulation performance of residential buildings during winter. Passive solar courtyards should be located on the south side to maximize sunlight absorption during the winter months. A sunlit corridor should be introduced as a transitional space, with large, high-performance, insulated glass doors and windows used in areas connecting the courtyard to the interior (Figure 19). Secondly, this study recommends replacing traditional firewood- or coal-burning kang (heated bed platforms) with solar-powered heated kang. These heated platforms, primarily used as sleeping areas, should be positioned on the south side near the windows. Their main structures should use materials with good thermal storage properties, such as bricks or concrete.

By leveraging passive solar courtyard technology and passive solar-heated kang technology, the thermal insulation of courtyards during winter can be improved, reducing reliance on traditional energy sources. This approach is of significant importance for forest conservation within the MNNR.

4.3. Spatial Temperature Analysis

The use of carbon fiber underfloor heating and magnesium cement roof insulation technologies is proposed to enhance the indoor thermal comfort of rural residences during winter. Specific measures include the following:

Carbon Fiber Underfloor Heating Technology: Selecting floor materials with high thermal conductivity and using scientific installation patterns, such as “S-shaped” or “rectangular loop”, to ensure more uniform and efficient heat distribution, thereby improving the indoor thermal environment.

Magnesium Cement Roof Insulation Technology: Employing multilayer composite insulation structures, such as installing a vapor barrier beneath the magnesium cement insulation layer, to prevent indoor water vapor from entering the insulation layer and reducing its effectiveness.

The above architectural and spatial technological innovations, as demonstrated through experiments (

Table 3. Spatial pathways for the optimization of indoor thermal environments in buildings in the MNNR.

Spatial Optimization Technique	Technical Advantages
Earth-Steel Structure Modern Rammed Earth Technology	Utilizes earth–steel structures as load-bearing elements instead of traditional timber, combining the advantages of both steel and rammed earth materials. Enhances the durability and mechanical properties of rammed earth by adding sand, cement, fibers, and stabilizers to the soil while applying external force to bond soil particles, ensuring the material remains environmentally sustainable and reusable.
New-Type Rammed EarthBrick Technology	Involves material modification and tool improvement. Material modification aligns with modern rammed earth technology, while tool improvement uses a static compression block molding mechanism to produce rammed earth bricks, improving production efficiency
Passive Solar Courtyard Technology	Addresses the limitations of the “narrow and long” layout of traditional solar corridors by enhancing the living environment in larger courtyards. Features measures like high windows on the north and south sides to create natural, cyclic ventilation for extreme heat conditions.
Passive Solar Heated Bed Technology	Retains the advantages of traditional heated beds made of rammed earth while replacing firewood, coal, and cow dung with electricity to eliminate resource depletion and environmental pollution. Combines with solar water heaters to enhance efficiency.
Carbon Fiber Under floor Heating Technology	Directly heats indoor objects without warming the air, reducing indoor heat and humidity loss caused by air convection, thereby improving overall comfort.
Magnesium Cement Roof Insulation Technology	Utilizes industrial magnesium waste, a by product of salt lake magnesium production in Qinghai Province, to manufacture insulation materials for zhuangkuo roofs, reducing the accumulation of industrial waste and mitigating ecological impacts on the plateau.

), reveal that the performance of new zhuangkuo residential forms surpasses that of traditional zhuangkuo residences in terms of winter insulation, summer ventilation, structural stability, and indoor lighting. These advancements provide a valuable reference for enabling villagers to gradually reduce their reliance on traditional energy sources while pursuing modern comfort. Furthermore, these innovations enhance the potential for accommodating tourists, serving as an effective means of integrating local communities into the management of resources and facilities within the MNNR.

5. Conclusions

Multiple factors influence indoor thermal comfort during the winter months. These include humidity, air temperature, radiation temperature, air moisture content, air velocity, activity level, and metabolism. This study specifically examines air temperature and humidity as the primary test parameters, reflecting the unique geographical and climatic conditions found on the Qinghai–Tibet Plateau. By conducting systematic indoor thermal environment testing across five residential buildings in the MNNR, our research investigates various approaches to enhance indoor comfort. We explore improvements in building materials, spatial configurations, and heating methods, with the goal of optimizing living conditions while prioritizing environmental sustainability.

Our research has yielded several important conclusions. First, we propose inheriting and optimizing the traditional “Zhuangkuo” residential forms native to the MNNR. This involves maintaining the primary spatial position of the U-shaped main house (zhengfang) while also increasing building width-to-depth ratios, optimizing column–grid structures, and improving construction techniques. These adjustments significantly enhance indoor thermal comfort, especially during winter, while preserving the architectural identity that defines local dwellings.

We also found that integrating passive solar design with sustainable heating methods offers substantial benefits. By incorporating passive solar corridor designs, optimizing window placements, and adjusting building heights, we developed a spatial framework that enhances natural daylighting and thermal regulation. Our research further suggests that carbon fiber underfloor heating and magnesium cement roof insulation serve as innovative strategies to reduce indoor heat loss and energy consumption, thereby decreasing reliance on traditional fuels like firewood and coal.

A crucial aspect of our findings centers on balancing ecological conservation with residential development needs. Optimizing residential environments proves essential for both improving villagers’ quality of life and preserving natural resources within the MNNR. Traditional residential models no longer fully satisfy modern living requirements or support energy-intensive construction at scale. Instead, we advocate for resource-efficient development approaches that utilize locally available materials and passive energy solutions, maintaining ecological balance while honoring vernacular construction wisdom.

Based on our findings, we offer several strategic recommendations for optimizing traditional residential architecture in cold climate regions. These include enhancing spatial layouts through adjusted building proportions and optimized window positioning; applying passive solar energy designs to improve indoor thermal stability; incorporating new insulation and heating technologies to minimize heat loss; reducing dependence on traditional fuels while preserving cultural heritage; and establishing a harmonious balance between ecological protection and residential development that can serve as a reference for conservation areas with similar climatic conditions worldwide.

Additionally, this study makes three key contributions to conservation-focused architectural research. First, it offers a conceptual contribution by proposing an alternative conservation strategy that integrates vernacular dwellings into the ecological framework, rather than relying on displacement policies. This challenges conventional human exclusion models in protected areas. Second, it provides a methodological contribution through systematic thermal monitoring of different rural building typologies. This approach offers empirical evidence on how architectural configurations influence microclimatic conditions, forming a data-driven basis for sustainable rural design. Third, it presents a practical contribution by offering a scalable architectural strategy applicable to other conservation areas with similar climatic and socio-cultural contexts. This provides a realistic framework for sustainable community integration in nature reserves.

While this study provides valuable insights into optimizing rural residential architecture in nature reserves under cold climate conditions, several limitations should be acknowledged. First, the research data primarily come from selected representative samples within the MNNR. Therefore, further studies are needed to assess the applicability of these findings to different geographic and climatic contexts. Second, the thermal comfort assessment in this study is based on short-term measurement data. Future research should incorporate long-term dynamic monitoring and numerical simulations to enhance accuracy and capture seasonal variations in indoor thermal environments. Additionally, given the emerging shift in conservation policies that now emphasize community participation rather than forced relocation, future research should further explore how rural housing design can seamlessly integrate into protected areas while minimizing human impact. Investigating multi-scale planning approaches that balance ecological conservation and residential sustainability would provide valuable insights for conservation policies and rural development strategies in similar environmental contexts.