ВІСНИК ЛЬВІВ. УН-ТУ
Серія географічна. 2004. Вип. 31. С. 215–222
VISNYK LVIV UNIV
Ser.Geogr. 2004. №31. Р. 215–222
УДК 911
DRIVING FORCES OF EVOLUTION OF LANDSCAPE SPATIAL PATTERN
A. Khoroshev
Moscow State University, Moscow, 119992 Russia
akhorosh@orc.ru
Landscape science deals with delineation of holistic natural systems with dense
interdependencies among components. Degree of adaptation between abiotic components
(deposits, topography) and mobile components (plant cover, soil) is assumed to be a
criterion of equilibrium or non-equilibrium state of landscape. We analyse reasons for
discrepancy between properties of abiotic and mobile components with focus on selfdevelopment of landscape when it gradually becomes less and less dependent on lithogenic
controls. We used notion of uncertainty in inter-component relations evaluated by means of
discriminant analysis to evaluate degree of landscape equilibrium. The purpose is to
evaluate contribution of self-development to evolution of landscape spatial patterns, to
reveal driving forces of self-development. Low uncertainty (high concordance) is assessed
as equilibrium units that can be considered holistic systems. Interpretation of high
uncertainty involves both processes within the patch and properties of environment
described by means of space image. The results enable to separate patterns with different
degree of determinism between abiotic and mobile components as well as to identify
diverging and converging landscape units.
Key words: equilibrium, landscape components, relations, self-development,
uncertainty
Introduction. Identification of holistic landscape systems has always been a task
of crucial importance for landscape ecology due to close connection with the problem of
forecasting anthropogenically induced changes [12, 9]. Response of landscape to
disturbances is expected to be the same in patches with similar interrelations among
components (namely, deposits, landforms, water, soil cover, plant cover). East European
tradition in landscape research distinguishes so called vertical and horizontal (or
morphological) landscape structure [3] related to topological and chorological relations in
landscape ecology [16]. The former means a set of interacting landscape components like
mentioned above, while the latter is related to a set of landscape units being in interaction
by means of lateral flows of matter, energy and information. The notion “horizontal
structure” is close to “landscape pattern” in landscape ecology [2].
Landscape components have various temporal scales, so their mutual adaptation to each
other requires certain time. Deposits and landforms are treated as inert components as
compared with relatively mobile components like soil and plant cover. This holds true for
plain regions, while in mountains characteristic time scales can be comparable for plant
cover and soil-forming deposits, e.g. in mudflow cones. Equilibrium in relations between
landscape components is a topic of great concern for the researcher who is interested in
problems of landscape resilience. Getting insight into degree of equilibrium enables us to
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© Khoroshev А., 2004
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predict diversity of possible responses of landscape to disturbances. We assume that mobile
components tend to adapt step by step to constraints imposed by inert components,
equilibrium relations being the result. In reality this is not more than particular case.
Abiotic constraints components can be more or less wide. Under certain abiotic conditions
development of soil and plant cover can follow this or that trend depending on occasional
events. The result is diversity of mobile components states under similar lithological and
geomorphological conditions (so called “lithogenic conditions”) and vice versa.
In landscape ecology absolute and relative space are distinguished [6]. Absolute
space involves an Euclidean point of view usually based on defined grid system while
relative space is defined by functions, processes and rates [7]. In other words, relations
between landscape components and landscape units are assumed to be more important than
geographical distance from the relativistic point of view. In landscape mapping evaluation
of these relations is critical for hierarchy identification as well as for choice of management
strategy. In this article we propose to identify landscape patterns based on relationship
between inert and mobile components.
Holistic landscape structures are formed under the influence of a number of
factors. Lithogenic factor is believed to be the most powerful in comparison with
hydroclimatic and biotic ones [12]. Conventional landscape mapping is based on few
fundamental principles having roots on deterministic approach: a) mobile components
reflect properties of lithogenic base on landscape; b) landscape boundaries and boundaries
of geological and geomorphological units are in one-to-one correspondence; c) each
hierarchical level of landscape organization is controlled by specific principal factor of
differentiation [14]. For example higher order landscape units are identified according to
landforms and the lower order ones – according to diversity of bedrock. Mobile
components a priori are believed to differ in perfect concordance with lithogenic diversity.
Different approach is applied by F.N.Milkov [8] who separates landscape units of the same
hierarchical order according to genesis. V.B.Sochava opposed identification of low order
landscape units according to geomorphological properties [11] and argued that a set of
interactions between components should be considered.
Fruitful findings by V.N.Solntsev [12] provide an approach to identify landscape
structures according to interactions of landscape components. His concept assumes that
three types of relatively independent landscape systems emerge at the same hierarchical
level being shaped by lateral flows, properties of deposits or solar energy. We make an
attempt to delineate landscape units that possess holistic properties due to perfect
adaptation of mobile components either to lateral flows or to radial flows. Lateral flows are
controlled by degree of relief dissection and slope gradients. Radial flows depend on
texture of deposits affecting soil water capacity and permeability. Classification of
landscape units by intensity of lateral (say, geomorphological classes) and radial flows (say,
lithological classes) is performed in order to discriminate properties of landscape units
between lithogenic classes. This procedure provides identification of landscape units in
which a set of soils and plant cover properties is specific and differs from all other units in
perfect concordance with geomorphological and/or lithological contrasts. In other words,
relative space concept is applied: groups of landscapes are composed in such a way that
distances between groups are the largest possible both by inert and mobile components.
Groups consist of landscape units with equilibrium relations between inert and mobile
components since their properties do not intersect. Possible evolution trends cannot be
multiple. Resilience in relation to disturbances is high.
In parallel, a number of landscape units fail to fall definitely into a certain class sin-
DRIVING FORCES OF EVOLUTION OF LANDSCAPE SPATIAL PATTERN
217
ce properties of mobile components (e.g. abundance of plant species) tend to be included
into several classes with similar values of posterior probabilities. We regard this result as
uncertainty in inter-component relations. Indefinite concordance between inert and mobile
components may be caused by few reasons discussed below. However, in general case
resilience is lower as compared with equilibrium units since bifurcation is possible after
disturbance.
The objective of the research is to separate equilibrium units with lithogenically
determined vertical structure from the units with uncertain relations between inert and
mobile components as well as to reveal driving forces of uncertainty and self-development.
Quantitative information on density of intercomponent relations is applied to identification
of holistic landscape patterns and self-developing landscape units.
Material and methods. Study area is located in the middle taiga region in North
European Russia (the Vaga river basin, 6053’ N 4320’ E). The research has been
performed since 1994 [1, 4, 5]. Interrelations among landscape components are studied at a
fine scale on transect 8050 m long with descriptions regularly spaced over interval 25 m as
well as in coarser scale with 500 sample plots being dispersed over the area 200 km 2.
Landscape is typical for plains with moraine loam covered by surface sandy deposits.
During Holocene epoch landforms were shaped by erosion which followed network of
neotectonic joints. Lithogenic diversity is striking due to different thickness of sand cover
and moraine carbonate loam lying over Permian marlstone. Exposures of marlstone occur
on river valleys slopes. Emergence of alkaline groundwater within joints zones is essential
for geochemical diversity: typical acid Podzolic soils are in close neighbourhood with
neutral Umbric Albeluvisols and Umbrisols. Plant cover consists of primary spruce forests
(Picea obovata) alternating with secondary pine (Pinus silvestris) forests on sandy soils and
birch (Betula pendula) and aspen (Populus tremula) forests on clayey soils. Low shrubs
layer is typical with dominance of Vaccinium myrtillus, Vaccinium vitis-idaea. Moss layer
composition varies in concordance with water supply: sequence of communities with
dominance of Sphagnum sp., Polytrichum commune and Pleurozium schreberii is common
for catenas. Central sections of watershed areas poorly drained being occupied by
oligotrophic mires. Arable lands are located in the area with the most dense river network.
Exposures of marlstone on steep slopes favour formation of fertile Umbrisols cultivated
intensively.
Field material includes description of plant cover (abundance of species, canopy
density and coverage for each layer), soils (thickness of horizons, color according to
Munsell charts, texture, depth of carbonate horizon), landforms (genesis, shape, slope
gradient, aspect). Texture of deposits measured up to the depth of 150 cm with records over
the interval 5 cm is used as the control over intensity of radial flows in soils. Landsat 7
space images as well as map of Quaternary deposits and digital elevation model DEM
(scale 1:50 000) were used to identify landscape units. ArcView 3.2a software was applied
as a tool to calculate characteristics of relief dissection, namely: total length of valleys
around each sample plot, variance of elevations, diversity of aspects, distance to the closest
stream, slope angle. These indices are believed to characterize intensity of lateral transfer at
the site and general drainage conditions.
The approach proposed to identify self-developing landscape units and to interpret
driving forces includes following procedures.
1) Principal components analysis and multidimensional scaling are performed for
sets of data characterizing soils, plant cover, relief and deposits. Factor values obtained are
used at the following steps.
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A. Khoroshev
2) Classification of sample plots according to lithogenic conditions. Two types of
classification were performed using k-means method. Classification by texture of soilforming deposits characterizes conditions for radial flows. Classification by topographic
variables characterizes drainage conditions.
3) Discriminant analysis is performed in order to assess proportion of patches that
differ by soils and plant cover in perfect concordance with classes of topography or
deposits identified before. Posterior probabilities are computed for each sample plots.
4) Shannon formula is applied to calculate uncertainty measure for each sample
plot: H=-ΣPiLog(Pi), where H – uncertainty measure, Pi – probability that plant cover and
soils fall into a certain class (i) of topography or deposits. Uncertainty measure shows
degree of concordance in relations between mobile components and lithogenic conditions.
5) Interpretation of uncertainty measures is performed using regression models:
H=b0+b1*v1+b2*v2+b3*v1*v2+b4*v1^2+b5*v2^2+… , where v1, v2, … - factor values
characterizing landscape properties. The question solved is: which factor is responsible for
equilibrium/unequilibrium in inter-component relations.
6) Interpolation of uncertainty measures over the study area allows us to identify
areas with perfect adaptation of components and areas with continual transitions between
contrast equilibrium units.
7) Estimation of space scale relevant for analysis of inter-component relationship.
To solve this question we compared uncertainty measures calculated in relation to
topography and deposits calculated for landscape scale with 600 m as radius (H1) and for
local scale with 300 m (H2) as radius around each sample plot. If uncertainty in intercomponent relations decreases as larger environment is taken for description of topography
(H1-H2>0), broad space scale is more relevant. In case of increase of uncertainty measure
for broader scale (H1-H2<0), we conclude that the properties of the certain sample plot
needs smaller environment in order to be explained by topography.
The concept worked out is aimed at identification of both lithogenically
determined and self-developing landscape units based on statistical modelling. Low
uncertainty value shows evidence that lithogenic and mobile components are in
equilibrium. Landscape units of this type are quite holistic and emerged most likely as a
result of divergence within landscape.
High uncertainty values are more exciting. Interpretation involves testing several
alternative hypotheses. 1. Uncertainty of mobile components in relation to texture of
deposits (Ut) is compensated by low uncertainty in relation to drainage conditions (Ud) and
vice versa. Regression models
Ut=f(Ud)
provide tools for testing this hypothesis. 2. Uncertainty on higher hierarchical level
can be explained by relations on lower level. To test this alternative data set and grid size
are changed, uncertainty measures for few scales are compared. 3. Uncertainty is explained
by unfinished recovery succession. Statistical models of linkage between uncertainty value
and various properties of soils and plant cover enable to reveal processes responsible for
increase of uncertainty. 4. Self-developing redistribution of matter in soils generates
emergence of new properties of landscape and new landscape units being relatively
independent on abiotic conditions. This phenomenon is known as deterministic uncertainty [10]. The tools include statistical modelling of linkage between uncertainty value and
properties of environment measured on space image in moving window, namely diversity
(H) and deviation from properties of environment (D):
Ut,d=f(H, D).
DRIVING FORCES OF EVOLUTION OF LANDSCAPE SPATIAL PATTERN
219
The approach proposed deals with problem of translation of spatial information
from one scale to another which is considered to be one of the most important challenges in
landscape ecology [15]. Note that uncertainty Ut and Ud is calculated for macroscale, since
it is based on 800 sample plots comprising heterogeneous area of 200 km 2. H and D reflect
both abiotic and biotic heterogeneity in mesoscale. Thus, the procedure enables to evaluate
contribution of mesoscale factors to macroscale uncertainty by means of coefficient of
determination in regression equation. Let us give the simplest example. Plant cover in the
landscape unit is in poor compliance with deposits, namely alder is not typical for boreal
forest on loamy moraine plain. However high Ut value calculated for macroscale can be
easily explained if we consider high diversity of close surroundings of the unit due to
neighbouring small fen 200 m wide. Penetration of alder into common spruce forest is a
result of mesoscale process. If uncertainty is significantly related to mosaic properties of
environment, most probable trend of spatial evolution can be revealed: either convergence
or divergence of landscape units or stable equilibrium relations between lithogenic and
mobile components. To make decision we analyze various combinations of uncertainty
measure, diversity (entropy) of environment and uniqueness measure of the patch compared
with environment. Taking diversity of environment into consideration we obtain
opportunity to evaluate contribution of ecotone factor to uncertainty measure. In case there
is no connection between uncertainty measure and properties of space in close surroundings
we conclude that uncertainty cannot be interpreted as a result of self-development of spatial
pattern. Properties of environment were calculated in two scales with moving windows 500
and 1200 m.
Results and discussion. Spatial pattern of the landscape is shaped by a network of
joints stretching north-eastward and north-westward. River valleys, streams, bog expanses
indicate joints of various rank orders. We identified seven neotectonic blocks based on
density and depth of joints and separated by the most pronounced lineaments. Discriminant
analysis shows that 70 % of sample plots differ significantly given that they are located
within this or that block. Thus, blocks are treated as macroscale holistic landscape systems.
Apparently, neotectonic and palaeolandscape events were specific within each block and
imposed important constraints over possible trends of landscape structure development.
The lower hierarchical level of landscape organization is determined by diversity
of conditions for lateral and radial flows. At the macroscale drainage conditions (relief
dissection) impose constraints on diversity of components: 60 % of sample plots are
discriminated correctly taking herb layer properties as dependent variables, 40-45 % taking trees, low shrubs, moss layers or soils as dependent variables, i.e. as responses to
lithogenic contrasts. Total set of mobile components properties is discriminated correctly
up to 50 % between drainage classes. Figures for responses to texture classes are similar.
Thus, lithogenic factors in macroscale control totally no more than half of variability of
soils and plant cover.
Topographically determined and lithologically determined holistic landscape
systems with perfect one-to-one correspondence between lithogenic classes and mobile
components were identified based on posterior probabilities. It turned out that in deeply
dissected areas plant cover and soils have much in common despite lithological diversity
Holistic structures are determined by intensive lateral flows rather than lithology resulting
in convergent self-organization. On the contrary, in poorly dissected areas mobile
components respond to texture of deposits and ignore, sometimes, lateral drainage conditions.
In case where radial flows have highest intensity like sandy deposits equilibrium
landscape units emerge despite this or that pattern of neighbouring river valleys. High
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A. Khoroshev
uncertainty areas in relation both to deposits and relief dominate in flat watershed areas
favouring self-development of spatial pattern.
One of the possible explanations of high inter-component uncertainty involves
scale effect. Finer scale calculation showed decrease of uncertainty for soils and increase of
uncertainty for plant cover layers. Scale effect is especially well manifested in opposite
hydrological conditions. In swamped areas soils and herbs are sensitive to mesorelief
within 600 m as radius being insensitive to microrelief within 300 m as radius. Trees,
shrubs and mosses, on the contrary, respond to the closest environment (300 m). In the
driest pine-dominated habitats mosses and soils are sensitive to drainage conditions in local
(300 m) environment while trees, shrubs and herbs depend on drainage conditions within
600 m.
Nature of uncertainty in relations between components in study area turned out to
depend on several soil and phytocoenotic processes. Illuviation in soil profile affects
equilibrium of soils in relation to deposits. Emergence of carbonate-saturated groundwater
distorts equilibrium typical for boreal landscapes. This phenomenon is manifested as humus
accumulation in soil which forces plant cover to become insensitive to deposits owing to
paradox combination of oligorophic and mesotrophic species. Equilibrium of tree storey in
relation to both deposits and topography depends on stage of recovery succession, being
lower in climax spruce-dominated associations. Lithogenic contrasts are masked by strong
influence of spruce canopy on phytocoenotic and soil processes. Low shrubs, herbs and
mosses in climax associations depend on canopy trees rather than on properties of deposits
and topography. At initial stages of succession or in second-growth forests plant cover is
more diverse and responds to abiotic conditions much better.
To reveal self-developing landscape units we related uncertainty measures explained above
to properties of spatial pattern in surroundings of sample plots. High diversity of
environment can show evidence of ecotone effect as explanation of uncertainty of relations
between plant cover and abiotic conditions while homogeneous environment makes us to
exclude this factor. Unique patch inside homogeneous matrix may testify either divergence
of spatial pattern or gradual disappearance of the patch given that equilibrium is either high
or low. We revealed the following variants. 1. Positive linkage between uncertainty and
diversity and negative linkage with uniqueness is a result of convergence in mosaic
environment. Neighbourhood of small landscape units in unequilibrium state is typical.
Ecotone effect is possible. This type of relations is typical for flat watershed surfaces with
sandy or two-layered deposits. 2. Positive linkage of uncertainty with both diversity and
uniqueness characterises dependence of patch state on distance to landscape boundaries.
Equilibrium patches are formed in core sections of uniform landscape units with size about
500 m. The closer to boundary, the higher uncertainty is. At the same time uncertainty is
high if the patch is located within larger uniform landscape unit with size about 1200 m.
Thus, large uniform landscape unit is treated as a result of self-development because mobile
components in core sections cease to obey lithogenic conditions. This is typical for large
mire expanses in watershed depressions. 3. If uncertainty is negatively related to both
diversity and uniqueness we conclude that the patch emerged either as a result of
convergence within large uniform unit or as a result of divergence within mosaic
envirionment. Ecotone effect is impossible. This is true for flat watershed areas with sandy
deposits. In depressions mosses and low shrubs can also easily adapt to mosaic
environment being in equilibrium with deposits even if the patch is small. Then equilibrium
is a kind of adaptation to mosaic environment by means of self-isolation. High uncertainty
in this variant is a result of self-development, decrease of linkage with lithogenic condi tions.
DRIVING FORCES OF EVOLUTION OF LANDSCAPE SPATIAL PATTERN
221
4. Negative linkage between uncertainty and diversity and parallel positive one with
uniqueness is revealed for gentle slopes with sandy or loamy deposits. This type of
relations testifies start of divergence or degradation of the patch in alien environment, e.g.
small forest “island” surrounded by arable lands.
Conclusion. The results show evidence that starting conditions of landscape
evolution are influenced by block organization of the territory. Inter-component relations
have certain degree of freedom for self-development. Approximately half of soils and plant
cover variability is determined by topography and deposits. The densest linkages are typical
for slope units, the least dense ones with great opportunities for self-development – for
humid flat watershed areas. Contribution of local factors to uncertainty of lithogenic-biotic
relations is significant in watershed depressions and wide flat and slightly inclined
watershed areas. On slopes and narrow watershed areas properties of mobile components
are determined mostly by lithogenic conditions. Compact areas with high uncertainty of
intercomponent relations are located of flat and wide watershed areas and in mire
depressions. Principal factors of uncertainty are identified, namely: emergence of alkaline
ground waters, radial redistribution of substance in soils, peat accumulation, interactions
among vegetation layers, stage of recovery succession. Combined analysis of uncertainty
values and structure of local environment enabled to prove phenomena of convergence and
divergence of low-order landscape units as a result of self-development. Self-development
capacity is related to size of landscape unit. Homogeneity of environment frequently
encourages self-development and increase of independence of mobile components on
lithogenic base of landscape.
The research was supported by Russian Foundation for Basic Research (grant 0105-64822).
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РУШІЙНІ СИЛИ ЕВОЛЮЦІЇ ПРОСТОРОВОЇ СТРУКТУРИ ЛАНДШАФТУ
А. Хорошев
Московський державний університет, Москва, 11992 Росія
akhorosh@orc.ru
Ландшафтознавство займається виділенням холістичних природних систем із
сильними взаємозалежностями між компонентами. Ступінь пристосованості між
абіотичними компонентами (геологічні відклади, рельєф) та мобільними
компонентами (рослинний покрив, ґрунт) вважають критерієм зрівноваженості
ландшафту. Аналізуються причини неузгодженості між абіотичними та мобільними
компонентами з наголосом на саморозвиток ландшафту, коли він стає все менш
залежним від літогенного чинника. Використано уявлення про невизначеність
міжкомпонентних взаємозв’язків, яка оцінюється за допомогою дискримінантного
аналізу. Мета полягає в оцінці впливу саморозвитку на еволюцію просторової
структури ландшафту для виявлення рушійних сил саморозвитку. Низька
невизначеність (висока узгодженість) вказує на рівновагу одиниці, яку можна
розглядати як холістичну систему. Інтерпретація високої невизначеності охоплює як
процеси всередині одиниці, так і властивості середовища, які описуються
просторовим зображенням. Це дає змогу виділяти просторові структури з різним
ступенем детермінованості абіотичних і мобільних компонентів, а також
визначати ландшафтні одиниці, що дивергують або конвергують.
Ключові слова: рівновага,
саморозвиток, невизначеність.
ландшафтні
компоненти,
взаємозв’язки,
Стаття надійшла до редколегії 28.03.2004
Прийнята до друку 16.06.2004