Traditional ecological knowledge for sustainability: concepts to and approaches to interpret and quantify material flows
in past Korean landscapes
Department of Environmental Planning, Graduate School of Environmental Studies, Seoul National University. Seoul 151-742, Korea
phone: +82 2 880 5650, email: firstname.lastname@example.org
In terms of nutrient cycling, only a closed system or an open system that is balanced in input and output of essential elements is sustainable. In the past Korean landscapes, the balance was maintained by dominant internal cycles operated at a watershed scale. As the internal cycles were disrupted by new land uses, and the structures and functionings of landscapes have been changed, the sustainability of society is threatened. Disruption of the internal cycles by new land uses has changed the structuring and functionings of the landscapes, threatening the sustainability of the society. This paper aims to examine the internal cycles occurring in past Korean landscapes and proposes a concept of surface area index to characterize landscape structure. Quantitative approaches to measure surface area index and potential application of the index to hydrological and ecological phenomena are proposed. We shows that the index is strongly related to retention capcity of sediments and leaf litter reallocation in terrestrial ecosystems. The index was also advocated to account for scaling-dependence of solar radiation and leaf area index in a rugged montane landscape. We suggest that extracting practical concepts from past landscapes and relevant our traditional ecological knowledge, and testing the concepts with new research tools will be instrumental in constructing sustainable society. We aim to extract from past landscapes practical concepts relevant to our traditional ecological knowledge and to test the concepts with new research tools which will be instrumental in constructing a sustainable society. Although our outcomes are nonconclusive, the approach is promising for improving disciplines such as conservation ecology and restoration in Northeast Asia regions.
Sustainability is defined as the process of change in which the continued exploitation or protection of resources, the direction of investment in land, and associated institutional changes are consistent with figure as well as present objectives for perpetuating environmental qualities and socioeconomic functions of ecosystem (World Commission on Environment and Development 1987). Sustainability is a process which is related to ecological, technological and social dimensions (Berke et al. 1998, Lee 2001).
Sustainability of a landscape or society is intimately coupled with its structure and function (Figure 1). The structure of landscape is shaped by natural and cultural and determines flexibility, connectedness and diversity of ecological processes to generate the biological and biogeochemical capacity, which is essential for adapting and responding to a changing environment (Odum and Turner 1990, Forman 1995, Flore et al. 1998). Succession, biological diversity, forage patterns, spreads of plant propagules, animal locomotion, flows of energy and materials, invading organisms and disturbance, human transportation, and information transfer all have important spatial components at different scales (Turner and Gardner 1991, Forman 1995, Lee 2001). The processes have a strong influence over resource supply and environmental integrity (Lee et al. 1992, Naveh 1995). Since so-called sustainable society relies on a consistent and appropriate resource supply and environmental quality (Brussard et al. 1998), landscape patterns are a pair of key words in landscape ecology and ecosystem management for sustainability (Alington 1998).
As the landscape patterns are created by redistribution of energy and materials, understanding what creates landscape structure, and how ecological and socioeconomic processes are affected by landscape structure may provide an insight into the management of sustainable environment (Forman 1995, Pickett and Cadensasso 1995). Hence, this article aims to examine traditional ecological knowledge by highlighting major pathways of energy and materials in some past Korean landscape systems, which may has served the purpose of maintaining ecosystem processes and function.
Figure 1. Flow chart showing the way in which landscape patterns moulded by natural and cultural factors are related to socioeconomic and ecological sustainability (Lee 2001).
A Korean map issued in the 16th century demonstrates that Korea consists of several watersheds, defined as the areas that drain to water bodies including lakes, rivers, estuaries, wetlands, streams, and the surrounding landscape (U.S. EPA 2000). In the map, divides of large watersheds are named Daegan (ÓÞÊÏ), Jeonggan (ïáÊÏ), and Jeongmaek (ïáØæ). Baekdoo Daegan is the largest range in Korea, linking Mt. Baekdoo (Mt. Changbaishan), Mt. Dooryu, Mt. Madae, Mt. Keumkang, Mt. Sorak, Mt. Sobaek, Mt. Sokri and Mt. Jiri and dividing Korean Peninsula into eastern and western parts (Figure 2). Jangbak Jeonggan is the range dividing HamKyungbookdo into northern and southern parts, lying from Mt. Dooryu to SeoSura. The other major ranges are 13 Jeongmacks (Lee 1996). It is noted that the concept of Bakdoodaegan is based on watershed, appearing in the Chosunjundodrawn by Sangki Jung in 1757 (ÇÑ¿µ¿ì Ôõ 1999). It is evident that Korean people had in mind a concept of watershed long time ago as the frame of land was expressed by major mountain ranges and rivers even in the map of Honil-Gangri-ryukdae-Gukdo-Jido (ûèìéË²×âÕöÓÛÏÐÔ´ñýÓñ) drawn in 1402 (ÇÑ¿µ¿ì Ôõ 1999).
Figure 2. An old map of the Korean Peninsula is based on watershed concept (from Woo Hyung Lee).
It is also illustrated in many old maps that Korean people had a concept of watershed (Figure 3). Past Korean presumed that divides governed distribution of water and materials in landscapes, but corresponded to the cultural boundary to control information exchange among local areas and regions. An administrative unit of Korea is called Dong (Ô×), derived from Chinese characters implying ¡®water¡¯ and ¡®same¡¯, indicates that the unit is based on the same water (in a watershed). People who shared the same fountain, well, stream, and/or reservoir had more chance to talk to each other and exchange cultural activities. Hence, we are aware that people who reside in the same basin have similarity in terms of housing, tools, dialects, and so forth (ÀÌ¿ìÇü 1996, Lee 2001(ÀÌµµ¿ø 2001)). Unlike many current administrative boundaries, in fact, the natural ones may be useful in interpreting flows of materials and information in land components.
Figure 3. A traditional map of a past town. Redrawn from a map kept in Kyujanggak (Ð¥íñÊÈ), Seoul National University.
Landscape is defined as a mosaic where a cluster of local ecosystems is repeated in similar form over a kilometers-wide area (Forman 1995). An ecosystem cluster represents a group of spatial elements connected by a significant exchange of energy, matter, or information and is a spatial level of hierarchical organization between the local ecosystem and the landscape (Forman 1995, but see Allen 1998). A configuration refers to a specific arrangement of spatial elements that is repeated in other locations and is thus used in any spatial scale. In landscape ecology, however, a configuration is a repeated, spatially explicit cluster of local ecosystems or land uses when it is specifically arranged.
Village, agricultural areas, forests, streams and roads are major components of a cluster in many past Korean landscapes, arranged in a typical way (Figure 4).
Figure 4. Major flows in a configuration of forest, village and cultivated fields, which occurred in old Korean landscapes (Lee 2001).
The specific arrangement of landscape elements seems to evolve from Korean traditional knowledge which is closely tied to climate, topography, soil, vegetation, and human perception.
The cluster of ecosystems is tied together by animal movement as well as material cycling. Many animals feed in one ecosystem, drink in a second, and rest and leave wastes in a third (Senft et al. 1987, Senft 1989). For example, egret and heron populations requires (1) a marsh for feeding that it larger than a certain minimum size; (2) a wooded area for nesting and roosting that is larger than a certain minimum size; and (3) that the marsh and woods are less than a certain maximum distance apart (Forman 1995). Since many species depend on different habitat types to complete their life cycles, their persistence in nature requires a cluster or configuration of different habitat types. The term, ¡°landscape complementation¡± was coined to highlight the requirement (Dunning et al. 1992). Landscape complementation comprises the proximity of critical habitat types (Dunning et al. 1992) and the degree to which organisms can move between them (Taylor et al. 1993, Pope et al. 2000).
In a similar fashion, many insects were maintained in a cluster of forest, a rice paddy, a water way, and scattered irrigating ponds in old agricultural systems. For example, a species of firefly (Luciola lateralis) is able to complete her life when she is supported by the adjacent landscape elements (Figure 5). The fireflies inhabit forest near a pond, feed on mollusks such as freshwater snails in streams, and lay eggs on rice paddies. Larvae and pupae spend their spans in ponds and banks. As the condition was satisfied in traditional Korean agricultural landscapes until 1970s, the fireflies were ubiquitously encountered, but recently became restricted to rice paddies, ponds, wetlands and watercourses lying in slope and remote from automobile roads.
Figure 5. Life cycle of a firefly species and landscape complementation. Drawn from data of Y.-I. Mah.
The major reason that the number of fireflies is declining may be due to the loss of landscape complementation. There were a lot of ponds and wetlands among rice paddies, divided by banks in traditional Korean agricultural landscapes. Fireflies were maintained by the complementation of shallow waters, paddy bank, and streams, forest areas. While small rice paddies were merged in larger rectilinear form like a chess board, and irrigation systems were improved during the last decades, most of ponds and wetlands were removed. Furthermore, paddy banks where larvae of fireflies should spend their lifespan were also destroyed or weakened. In addition, it appears that mating of adult firefly has been interrupted by increasing number of electric lights, which were established in agricultural villages and rest areas around highways and local roads (H.-C. Park, unpublished paper). Overall, the landscape change caused damage of landscape complementation.
In summary, only a closed system or an open system that is balanced in input and output of essential elements is sustainable (Figure 6). In the past Korean landscapes, the balance was maintained by internal cycles predominantly operated at a watershed scale. The sustainability of past Korean landscapes has been secured by internal cycling of objects such as energy, materials, organisms, and information in a configuration of spatial elements as old Korean did evidently recognize. Since the cycling was disturbed by recent land use practices, landscapes have been subject to longer and external pathways of objects. It is noted that leakage of objects is more probable in a long pathway than in a short one, unless additional energy is not subsidized for security. Accordingly, we hypothesize that recent environmental degradation is intrinsically associated with the long transport of objects, and will be remedied when management practices are employed to cycle objects among components and secure less leakage during transfer.
Figure 6. A system that is operated by internal cyclings (a) is more sustainable than one operated by external cyclings (b). When the external cycles are intimately linked, it becomes internal at a large scale (c).
The hypothesis will be manageable when an approach to quantify landscape structures and functions and relate one to the other is available. The hypothesis will be manageable when a method to quantify and correlate landscape structures and functions is available. Unfortunately, this is yet unavailable. Hereby, we propose two indices to quantitatively characterize landscape structure and function. Although relevant ideas are premature and discussion is limited, we would like to share these at least to raise some quesitons during a China-Korea joint symposium.
Until recently, landscape ecology has been mainly concerned with two-dimensional organization of ecological phenomena and their reciprocal effects on processes and pattern (Lee 2001). For example, classical theory of island biogeography focused on size effect of island on species number, failing to include vertical structure as well as horizontal differentiation of landscape (MacArthur & Wilson 1967). Size and shape of patch and corridor, characteristics of boundary, and configuration are frequently related to functions and changes of landscape (Forman 1995). Hence, methodology and indices based on two-dimensional views are of predominant concern to describe landscape structure (Hargis et al 1998, Tinker et al. 1998).
Two-dimensional views minimize such patterns and processes, whereas three-dimensional views, especially in rugged, vegetated, and/or man-made landscapes, provide additonal key insights. With increasing topographic relief or steepness, for instance, vertical flows and movements appear to increase rapidly relative to horizontal flows (Swanson et al. 1988). Especially, current theory and indices may deviate from situation in areas whose land surface undulates.
Vertical characteristics of landscape may be described by surface ruggedness or roughness. Although ruggedness is used for geological or topographical elements (Forman 1995), roughness is used in a general sense in this study. Surface roughness refers to the sum of slope, valley, peak, exposure, elevation, height and density of vegetation, and organic residues on the ground.
The functioning and maintenance of landscape are largely influenced by heterogeneity (Flores et al. 1998), which results from patches of different roughness. Vegetative buffer zones or hedgerows remove sediment, nutrients, pesticides, and herbicides from surface and subsurface runoffs by increasing the hydraulic roughness and biochemical activities of the landscape (Lee et al. 1989, Iversen et al. 1993). It is well known that roughness causes deposition of particulates by reducing surface flow velocity while biochemical processes control assimilation and decay of dissolved chemicals. In this case, the roughness is partially responsible for biogeochemical aspects of vegetation and soils as a whole. Although only color may contribute to generation of visual heterogeneity and regulate animal locomotion, it is not considered in the current study.
Beasom et al. (1983) proposed that ruggedness be expressed by the total length of contour lines per unit area on a topographical map. However, there may be difficulties in applying the definition to a landscape of small scale as it takes time to survey fluctuating microtopography in fields and draw contours in details. Furthermore, ruggedness does not consider aspects of tree stem, branch, foliage, and organic residue. Alternatively, a surface area index is defined as the ratio of air-exposed surface area of landscape to its area projected downward. For example, the surface area index of a smooth and horizontal plane is one, but greater than one when the plane is slanted or crumpled as projected area decreases. The index also increases when any three-dimensional structures are placed on the upper surface of plane. Contribution of simple landforms and vertical stratification of forest to surface area index are illustrated in Figure 7. Although the examples are too simple to represent real situations, these help us to understand how the surface area index is related to landscape features.
Figure 7. Relative surface area indices for some landscape components (ÀÌµµ¿ø 1998).
In a similar way, leaf area index (LAI), which represents all of the upper surfaces of leaves projected downward to a unit area of ground beneath the canopy (Waring and Running 1998), has been employed for several decades. As plant ecologists are concerned with photosynthetically active parts of plants, LAI is limitedly warranted in describing biological phenomena mainly and hydrological processes partially. For instance, FOREST-BGC model, which estimates primary productivity as a function of LAI and is widely used in ecosystem analyses (Running and Gower 1991), failed to differentiate microtopographic effects on evapotranspiration and soil moisture, although observed soil temperature and moisture are significantly different depending on landscape location in a Korean forest (Kang, personal communication). Manning¡®s roughness coefficient, which is employed in hydraulics to estimate stream flow, is also comparable to the surface area index as both of them consider resistance of land surface to a moving object (see Brooks et al. 1991). However, the coefficient is empirically determined and restricted to estimate discharge in water ways. On the other hand, the surface area index includes surface areas of abiotic ground components, and biogenic materials such as stems, branches, living foliage, and fallen residues, and man-made structures. Once the index is determined for landscape elements, that will be extensively tested to describe movements of water, wind, animal, and human transportation means from a landscape perspective.
As water flow, wind, animal locomotion and human transportation are sensitive to surface roughness, the index would be instrumental in studying functionings of landscape and region at different scales. It is hypothesized that an area of large surface area index is more variable than that of small one and thus acts as a sink or source of objects. For example, Lee et al. (1999) observed that surface roughness was positively related to density of woody shrubs in a forest floor and could describe retention of leaf litter quantitatively. Primary productivity increases with increasing LAI in forest ecosystems, implying that energy trapping efficiency of landscape is positively proportional to LAI (Waring and Running 1998). Interception of precipitation is high and thus stream flow is low when a forest is dominated by tree species of high LAI (Swank and Douglas 1974). Contributions of undergrowths and concave area to material retention and retardation of water discharge are analyzed below. Many animals may also prefer to reside in a forest composed of dense canopy, understory and litter, rather than an open area.
Surface area index includes the characteristics of topography, woody stems and branches, canopy, understory, litter and man-made structures. Contribution of each component to surface area index of a landscape element is separately estimated. Contribution of topography is able to be determined by digital elevation model (Band 1989). Swank and Schreuder (1973) reported estimates of foliage, branch and stem surface area for a white pine stand by using three different methods: (1) stratified two-phase sampling, (2) two-phase sampling with a regression estimator, and (3) two-phase sampling with a ratio-of-means estimator. Surface area of stem may be a function of tree density and size in a forest floor. Contribution of canopy and understory to surface area is represented by LAI, which is estimated from measurement of leaf litterfall collected periodically throughout the year (Burton et al. 1991), the fraction of visible light transmitted through the canopy to the ground (Gower and Norman 1991), and remote sensing imagery (Chen and Cihlar 1996, Myneni et al. 1997, Kim et al. unpublished data). Leaf area of understory is also estimated by videography (Law 1995). As the amount of litter is determined in the field, its contribution is estimated (Lee et al. 1999). Surface of man-made structures can be directly measured or calculated.
Estimated value of surface area index is dependent on the scale that is considered in field survey or map (Figure 8). Similarly, the length of a coastline is infinitely long if it were outlined in infinite detail (Allen and Hoekstra 1992). In this regard, landscape roughness as well as the length of a coastline needs to be estimated at different scales depending on the levels of interest (Ahl and Allen 1996). Regional and landscape processes are investigated with low resolution of map, but local processes with high resolution of map.
Figure 8. Plot of surface area index against resolution of digital elevation model (Kang, unpublished data).
A log-log plot of grid size of the estimators and the estimate of surface area gives an aproximately straight descending line. The line slopes down because the finer the resolution used in the estimation, the larger the estimate of the surface area index. The slope is one minus the fractal dimension of the landscape (Allen & Hoekstra 1992). Fractal dimensions are estimated by regressing log surface area index against log grid size. Complex surface of a landscape more in surface area index to small changes in the grid size. Therefore, the steeper the slope of surface area to grid size, greater the fractal dimension. If there are more than two slopes in the graph, it suggests that major driving forces shaping landscape surface are differentiated at the resolution where transition occurs (Lee 2001). This property may help us detect major factors influencing landscape structure at different scales (Krummel et al. 1987, Lee et al. 2000). For example, the fractal dimsion of intact landform will be abruptly shifted at a specific resolution of analysis when natural or human disturbance is placed on the landscape, suggesting that the disturbance is influential at the smaller or larger scale than the resolution.
In fact, scale-dependence is observed in many case of nature (Holling 1992, Kang 2001). For example, the effects that small rocks and shrubs have on direction and speed of water flow are comparable to the effects that large ridges and valleys have. A large ridge plays a significant role in directing large mammals, but has a relatively little influence over that of very small invertebrates which spend whole life cycle in a valley. Grossi et al. (1995) reported that roe deer used the medium size of grain in an old field of approximately 1000 ha and their behaviors were coupled with the arrangement of diverse patches, while earthworms seemed static at one scale. As a matter of fact, ecological processes and heterogeneity are organized and operated at different hierarchical levels (O¡®Neill et al. 1986, Urban et al. 1987). Hence, some spatial scales will be more appropriate than others in quantifying roughness and managing ecological processes depending on what objects are considered (Fleury and Brown 1997).
A remote sensing technique has been applied to detect spatial distribution of LAI across landscapes in two ways. One is to relate the NDVI of a satellite image with light absorption by canopy. NDVI can be converted to the rate of photosynthesis using several physiological modifications. In this case, LAI is determined by an allocation rule of the estimated daily or monthly photosynthesis to leaf production. This approach needs physiological models for photosynthesis and leaf allocation. The second approach is to relate directly the NDVI to LAI using a simple linear regression model between vegetation indices from satellite images and ground-measured LAI. Although the two approaches have their own strengths and weaknesses, respectively, the approaches have a common problem when those are applied in rugged landscapes. For there is no satellite image with fine spatial and temporal resolutions sufficient to detect spatial distribution of LAI across landscapes. Above all, seasonal change of LAI of temperate mixed-hardwood forests needs high temporal resolution of satellite images. Although NOAA AVHRR is the case, it is limited by a coarse spatial resolution for landscape-scale studies. Although the first method is more physiologically meaningful, it is difficult to apply the method in mixed-hardwood landscapes by several reasons. Determining physiological parameters of each plant species is very labor-intensive and also the aggregate physiological parameters of mixed-hardwood forest are difficult to be determined from the parameters of each species. The latter approach is less ecologically meaningful than the former one because it assumes a linear relationship between a vegetation index and LAI, not the absorbed radiation. The assumption is basically grounded on another assumption that the degree of physiological limitation is spatially invariant regardless of spatial variations of local environment. If appropriate physiological modifications are considered, the latter approach may be advocated to predict spatial distribution of LAI across landscapes.
Primary productivity will be high when the environment is favorable. We assume that potential productivity is positively related to incident solar radiation and negatively to slope and elevation. Slope is a surrogate of soil fertility because sediment is accumulated in flat areas. Sedimentation occurs only in valleys not in ridges. Negative relationship of DEM is therefore included to avoid sedimentation in ridge area. Figure 9 shows the potential productivity and NDVI comparatively. Topographic solar radiation was predicted using TopoRad (Kang et al., in process). Potential productivity accounts for why the physiological modification to NDVI is needed.
Figure 9. Comparison between the potential productivity and LAI derived from NDVI. (a) a shade relief map indicating 12 sub-regions, (b) topographic solar radiation, (c) LAI, and (d) the potential productivity. In (d), the potential productivity was overlapped on the LAI map for visual comparison of the both maps. Used grid resolution is 30m¢¥30m. The potential productivities were calculated in twelve sub-regions, respectively.
The estimated values exponentially decrease as the resolution increase (Figure 9). The upper threshold of resolution is defined as the resolution over that estimated solar radiation and LAI do not vary significantly. As a landscape becomes complex topographically, the upper threshold may increase. The resolution where the variation of solar radiation and LAI are lower than critical values was determined as the upper threshold. Here, the critical values specific to solar radiation and LAI were used, respectively. The upper threshold of resolution was significantly different among 12 sub-regions. The threshold was highly correlated to topographic surface area index in the sub-regions (Figure 10).
Figure 10. Relationships between the upper threshold of resolution and surface area index in the cases of LAI (a) and solar radiation (b). Kang, unpublished data.
Retrieving traditional ecological knowledge and practical concepts which old people considered when they created landscapes, and testing the concepts with new research tools will be promising for improving disciplines such as conservation ecology and restoration in Northeast Asia regions. In this paper, an ecological sustainability was addressed in terms of traditional ecological knowledge or human perception related to past Korean landscapes.
A surface area index was proposed to evaluate the concept quantitatively. The index can be differentiated into three components. One is a topographic surface area index, determined by only local topography. The more rugged landform, the higher topographic surface area index is. The second is a biotic surface area index, largely describing the surface enlarged by vegetation. The last one is related to the surface of artifacts such as buildings, and bridges. We expect that many traditional landscapes have a higher ratio of total surface area index to the topographic one than human-dominated landscapes do nowadays and that the comparable properties of past and current landscape features are responsible for environmental change.
Spatial data of potential productivity will be essential when we plan land uses for sustainable society. Although the idea addressed here is premature, it is promising for research regarding interface between human sciences and landscape ecology and developing a physiologically based NDVI-LAI model at a landscape scale. Relevant concepts would be improved to characterize our unique landscapes in northeast Asia region. Comparative studies at different countries will pave the way for Asian ecology.
This paper is based on research financially supported by Korean Science and Engineering Foundation grant KOSEF 2000-2-51300-002-3 and facilitated by Environmental Planning Institute, Seoul National University.
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