Ecological restoration is the process of reclaiming habitat and ecosystem functions or enabling the ecosystem to develop through a virtuous circle, relying on the ecosystem's self-recovery ability and some artificial measures. The use of ecological restoration technology helps restore the damaged ecosystem and the poorly developed landscape and also creates good urban green spaces. This process of environmental governance is the best choice for improving landscapes in the future, and is in line with today's sustainable development concepts.
Overview of Jinxiu Valley
Overview of Beijing Garden
The 9th China International Garden Expo was held in Beijing in 2013. Jinxiu Valley, one of the "Two Points" of the planning layout of the expo park, is a sunken landscape valley with an area of 24.3 hectares and a depth of 30 meters. Beijing Garden, located in the northwest corner of Jinxiu Valley, was designed as a traditional royal garden themed as "The Garden of Ten Thousand Gardens". The two landscapes add a beauty to each other that blends tradition and modernity. It is hard to imagine that a few years ago the landscape was the largest construction waste landfill in Beijing. Through three years of ecological restoration and construction, the original landfill was transformed into a valley of verdant vegetation and blooming flowers.
The Butchart Gardens in Canada is a successful case of ecological restoration in an abandoned quarry. Through continuous and unremitting efforts of several generations, the gravel slopes where nothing grew more than 100 years ago were transformed into a well-known garden, making it the most vivid textbook for the use of ecological restoration technology. Several ecological restoration methods can be used to ecologically restore severely degraded ecosystems featuring damaged soil and plants and a lack of nutrients for plant growth, including covering the soil, performing physical treatment on the soil, adding nutrients, removing harmful substances, planting pioneer tree or grass species with strong adaptability, and inter-planting other native plants.
Jinxiu Valley and Beijing Garden took the excellent example of the Butchart Gardens for reference and adopted a similar approach in their ecological restoration. In addition, more gardening technologies and Chinese cultural elements were applied in their construction, making them the most distinctive garden landscapes in the Beijing Garden Expo Park. By summarizing the construction characteristics of Jinxiu Valley and Beijing Garden, this article will provide practical reference for such ecological restoration projects.
The Garden Expo Park is an irregular and long narrow 267 hectare plot extending from northwest to southeast along the western bank of the Yongding River in Fengtai District of Beijing. It is nearly 5km long from northwest to southeast and only 248m wide in the narrowest part. The designated area is mainly composed of two parts, namely, Yingshan Forest Park in the northwest and a construction waste landfill in the southeast. The area of the landfill was originally part of the Yongding River bed. It was used as a sand quarry in the 1980s and 1990s, and after years of excavation, a large pit of over 100 hectares was formed and then became a construction waste landfill. When China won the bid for the Garden Expo in 2009, there was still an unfilled gravel pit with an area of about 20 hectares left in the middle of the site. The bottom substrate of the pit was sand and pebble soil of the Yongding River, and the sidewalls and top of the pit were construction waste landfills, most of which was bare land on the river beach with no grass; the ecological environment was extremely poor.
Through analysis of the site, the main problems to be solved were identified as how to transform the harsh habitat into conditions suitable for plant growth, how to transform the existing sand pits into attractive landscapes at a reasonably low cost, and how to fully show the expo’s concept of green and splendid gardens.
The planning and construction of Jinxiu Valley and Beijing Garden take ecological restoration, landscape effects, water conservancy and flood discharge into comprehensive consideration. In line with the concept of harmonious interaction between man and nature, the design aims to transform the sand pit into a valley landscape through ecological restoration measures carried out at the foot of the Yingshan Mountain, turning the wasteland into green landscape. Beijing Garden together with Jinxiu Valley constitutes to a Greater Beijing Garden, with Beijing Garden representing tradition and history by classical style and Jinxiu Valley representing development and future by modern technology and achievement. The two landscapes supplement each other and make a good combination of traditional exquisite garden arts and advanced modern technologies.
Jinxiu Valley makes full use of the existing site and transforms the construction waste landfill into a sunken landscape garden. Platforms were built layer by layer in the 30 meter deep sandpit based on the actual land conditions, creating various effects of forests, flower valleys, waterfalls, streams, and lakes.
Application of ecological restoration technology
The construction of the Garden Expo Park, represented by Jinxiu Valley and Beijing Garden, has had a great impact on the ecological restoration of abandoned land through soil improvement technology, native plants cultivation, and rainwater collection and utilization. The application of ecological restoration technology not only improves the landscape effect and ecological benefits, but also greatly saves the construction cost of green space, which embodies the idea of using technology to create a charming garden expo.
Planning map of the Beijing Garden Expo Park (provided by the Design Consortium of Greening and Landscape Facilities for the 9th China International Garden Expo)
The designated area of Beijing Garden and Jinxiu Valley was a construction waste landfill. (Photo by Qiangjian)
Location of Jinxiu Valley versus Beijing Garden (provided by the Design Consortium of Greening and Landscape Facilities of the 9th China International Garden Expo)
Soil mass restoration
Due to the large soil pores of construction waste, the treatment and compaction of the base layer are of top priority when conducting greening in the landfill. With that focus, the ground will not collapse and the soil around the roots of the plants will stay loose. In terms of foundation treatment, the first step is to measure the site and clean up topsoil, trees, bushes and unsuitable materials before it is filled in with earth and stone to prevent subsidence and slippage caused by the rotting of turf and tree roots. And then the pits should be filled and tamped down properly. When filling in the soil, it is important to use the same kind of soil as far as possible, and control the soil moisture within the optimal range. If different kinds of soils are used for filling, it is necessary to pave and fill them in layers, placing the soils with high water permeability under those with low water permeability. Mixed use of different type of soils is not allowed and soils with low permeability should not be used for slopes, in consideration of the drainage of water and stabilization of foundation soils as well as the need to avoid water sacs and soil sliding in the fill. The foundation treatment and filling of the site must meet the requirements of park roads, buildings, and greening in the park. In addition, it is hard to compact large waste particles, so the overburden layer must be tightly compacted to prevent collapse, sinking and other phenomena. For Jinxiu Valley, the greening was built on the construction waste that was covered with soils of an average two meters’ thickness, and the soil is even thicker for special landscapes.
Soil improvement is a key step in the ecological restoration of wasteland. To ensure the survival rate and growth of plants, Jinxiu Valley increased the underground soil area for tree roots. Such soil improvement creates suitable nutrient conditions for plants and large tree pits and can alleviate the side effects of poor water permeability caused by over-compaction. The actual measurement of the physical and chemical properties of the soil showed that the soil was sticky and dense with poor air and water permeability and low nutrients. Planting trees in such soil would affect the aeration of plant roots, and the plants would become weak over time, which is not conducive to tree maintenance and landscape effects. To solve the problem, Jinxiu Valley used a mixed backfill soil in the underground area for tree roots that consisted of grass charcoal (20 percent), organic fertilizer (10 percent), and garden soil (70 percent), to ensure loose soil around the roots and reduce the possibility of collapse. The grass charcoal and organic fertilizer are rich in organic matter and can improve the soil. The acidic grass charcoal helps reduce the pH in alkaline soil, which is beneficial to the growth of trees. When planting, especially of trees in compacted soil, it is necessary to increase the underground soil area for tree roots to 2m×2m×1.5m and to backfill the improved soil.
Soil profile of Jinxiu Valley covered with construction waste (Photo by Zhao Ziliang)
Flower display area in Jinxiu Valley (Photo by Ye Peiwei)
Stone gabion retaining wall made of construction waste (Photo by Zhao Ziliang)
Decorations made of waste materials in the Tiantian Gardening Scenic Area (Photo by Zhao Ziliang)
Plant selection and arrangement
The important foundation of ecological restoration is the self-recovery ability of the ecosystem. Selection of native plants adapted to the local environment will greatly improve the efficiency of ecological restoration and avoid possible damage to the local ecological environment by exotic plant species. In the construction of an urban green space landscape, it is important to plant arbor, shrub, grasses and ground cover plants according to their biological characteristics, so as to establish different plant communities. This principle was used in the planting design of Jinxiu Valley and Beijing Garden. In addition to the different varieties of flowers in the park, Jinxiu Valley and Beijing Garden have also planted trees, shrubs, ground covers and aquatic plants. This approach helps reduce the time and cost of artificial maintenance and management, and helps the environment to renew and recover by itself.
While building the landscape, the pioneer trees with strong adaptability and good soil-fixing effect such as Lespedeza and twigs of chaste trees were planted, which helped accelerate the ecological restoration of Jinxiu Valley. In terms of plant diversity, Jinxiu Valley and Beijing Garden have planted over 360 kinds of plants, including evergreen trees, deciduous trees, evergreen shrubs, flowering shrubs, flowers, ground cover plants, and aquatic plants, of which 220 are woody plants. As the flower display area of the expo, Jinxiu Valley has planted more than 140 varieties of ground covers and flowers, consisting of new and improved varieties introduced and cultivated in Beijing in recent years. Many varieties such as geraniums and argyranthemum frutescens of new colors as well as the begonia semperflorenshybr and fragrant plantain lily with a new shape of leaves (Figure 7) are displayed on a large scale for the first time. The abundant plant species and diverse communities attract wild ducks, magpies, and other animals to set their homes in Jinxiu Valley. Meanwhile, the artificially stocked goldfish, frogs, crickets, orioles and other species in Jinxiu Valley and Beijing Garden add vitality.
Making use of nearby materials and waste recycling
Reduction of the transportation distance of materials is one of the standards of green buildings and eco-friendly gardens. The construction of Jinxiu Valley strictly followed that rule. The valley selected local plants and used stone materials produced from Fangshan District in the southwest of Beijing, which greatly saved the costs of transportation and time. In addition, many highlights of the landscapes in Jinxiu Valley are made from the waste materials of the original garbage pits, such as the stone gabion retaining wall made of waste building materials in the "Yan Shu" square, the decorations made of waste water pipes and wood in the Tiantian Gardening scenic area, and animal-shaped artworks woven from clipped plant branches in the Herb Garden. They embody the concept of environmental protection, and demonstrate the uniqueness of Jinxiu Valley.
Rainwater collection and reclaimed water utilization
To eliminate the crisis of surface runoff, make full use of the excess precipitation in summer, and provide tourists with a better recreational environment, Jinxiu Valley has built an almost one hectare lake at the bottom of the valley. The constructed wetland water system simulates the natural water environment to deal with any water crisis. In addition, a rainwater collection and recharge system was designed and has realized the recycling of water resources in Jinxiu Valley through collecting excess precipitation and using it to water plants. Jinxiu Valley and Beijing Garden have an irrigation water pipeline and a domestic water pipeline. The plants can be irrigated by rainwater and reclaimed water, which reduces resource consumption in water treatment.
Application of precision irrigation technology
Conducting irrigation based on the water demand of different plants, called precision irrigation, can minimize the waste of water resources. Precision irrigation adopts a relatively precise irrigation mode according to the physiological and environmental characteristics of each type of plant. Precision irrigation technology has been applied in Jinxiu Valley and Beijing Park to improve the utilization efficiency of water resources. Using a system composed of irrigation monitoring controllers and rainfall sensors, sprinkler irrigation and drip irrigation facilities are able to achieve accurate and automatic control of time and water volume of irrigation for different kinds of plants when needed. The data can also be adjusted at any time based on the experience accumulated in the maintenance process. According to preliminary calculations, the system can save 15 percent of the water used in manual irrigation, and 20 to 30 percent of the volume used in broad irrigation.
Cultural and ecological landscape restoration
While ecological restoration technology has improved the natural environment of Jinxiu Valley and Beijing Garden, various garden construction techniques have been used for the traditional cultural deposits of the gardens. Jinxiu Valley borrows the essence of the traditional Eight Sights of Yanjing, highlighting the design of hills, stones, water, flowers and waterfalls. Beijing Garden, with an area of only 1.25 hectares, fully demonstrates the royal garden culture through buildings, plants, mountains, rocks, and water plants. The three-folded courtyard in the garden displays the three types of imperial gardens, the buildings inside covers 10 different styles, the stone design covers five styles including caves, pathways, creeks and walls and the water body covers five including pools, streams, springs and wells. In the ancient buildings of the garden, traditional techniques have been used to color paint 188 figures including people, flowers and birds, and landscapes. All these make Beijing Garden the most complete traditional garden built in Beijing over the past 100 years.
Since the opening of the 9th China International Garden Expo, Jinxiu Valley and Beijing Garden have received more than 400,000 visitors. It is proved that the application of ecological restoration technology to the construction of greenbelt landscape reflects the perfect combination of traditional garden culture and modern ecological restoration technology. In addition, ecological restoration realizes landscaping of degraded wasteland, improves landscape effects and ecological benefits of the park, and saves the cost of green space construction. As Jinxiu Valley and Beijing Garden have become the most distinctive scenic spots in the Garden Expo Park, ecological restoration technology will be widely promoted and used in future urban construction.
The lake formed by collecting rainwater at the bottom of Jinxiu Valley (Photo by Ye Peiwei)
A weather station in Beijing Garden of Jinxiu Valley to collect data required for precision irrigation. (Photo by Ye Peiwei)
The Yantai viewing area of Jinxiu Valley (Overlooking the Eight Sights of Yanjing) (Photo by Ye Peiwei)