LANDSCAPE ECOLOGY in AGROECOSYSTEMS MANAGEMENT - CHAPTER 10 potx

Changes in Landscape Diversity Patterns in the Province of Wielkopolska, Poland, Influenced by Agriculture Andrzej Mizgajski CONTENTS Introduction Natural Landscape Development of Agricu

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Changes in Landscape Diversity Patterns

in the Province of Wielkopolska, Poland,

Influenced by Agriculture Andrzej Mizgajski

CONTENTS

Introduction Natural Landscape Development of Agricultural Landscape Present-Day Changes in Agricultural Landscape Conclusions

References

INTRODUCTION

Wielkopolska is a historical region situated on the Central European Plain, in the drainage of the Warta, a tributary of the Odra The main relief features of the region are the result of Pleistocene glaciations that moved in from the north Con-sequently, Wielkopolska’s landscape changes from the north to the south although

it has no clear natural borders in the west and the east In comparison to other regions

of Poland, Wielkopolska has had a unique history that is reflected in its economic structure This is especially true with regard to the last two centuries, when, because

of the agricultural and industrial revolution, the modern economic structure of the region was taking shape In the 19th century, the area roughly corresponding to historical Wielkopolska was a separate province under Prussian occupation After Poland regained independence in 1918, the region continued as a compact admin-istrative unit known as a voivodeship Only between 1975 and 1998 was the region

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divided into smaller administrative units Statistics quoted in this chapter refer to Wielkopolska within the historical administrative boundaries that existed at a given time

A characteristic feature of the economy of today’s Wielkopolska is highly inten-sive agriculture and a well-developed farm produce processing industry The share

of acreage of large farms (approximately 20%), in comparison to that of small peasant family holdings, is much higher here than in central Poland

Throughout the region’s history, agriculture exerted the strongest anthropogenic impact on ecosystems, which is reflected in the landscape Man’s impact on the environment has severely reduced the percentage of the land that is a natural or semi-natural ecosystem For example, nature reserves cover only 0.18% of the present-day voivodeship of Wielkopolska

NATURAL LANDSCAPE

The major natural characteristics of the region came into being during Pleistocene glaciations, which covered the area three times from 1 million to 11,000 years BP They left behind a hilly, undulating, and plain terrain lying, for the most part, at

60 to 120 m above sea level The lowest valley bottoms lie below this range, while end moraines rise above it In terms of geological structure, boulder loams — a glacial sediment, and sands, both loamy and friable glacio-fluvial and fluvial sedi-ments, in part reshaped by wind, dominate close to the surface Medium-fertile and poor soils developed on them

The latest glaciation (Würm) engulfed the northern part of the region, dividing

it into two parts with different landscapes The northern part shows greater relief energy and has glacial channels, on the bottom of which are many lakes The southern part was molded by earlier glacier transgressions and certain processes occurring in the forefront of the last continental ice-sheet The terrain here is less varied due to denudation, and there are no natural water reservoirs Wielkopolska lies in the temperate zone Its weather is characterized by the influx of polar-maritime air masses from the west, which dominate in the warm months In winter and spring,

a considerable impact on the weather is exerted by arctic and polar-continental air masses coming from the north and east (Wo 1994) Average temperatures for July, the warmest month, are 17.5 to 18°C, while in January, the coldest month, the average temperature is –2 to –3°C Maximum rainfall is observable in summer (approxi-mately 40%), while in the remaining three seasons the amount of precipitation is rather uniform On average, the region receives 500 to 600 mm of rainfall annually There are two basic types of natural landscape: (1) the plain and undulating landscape of the lowlands and (2) the landscape of valleys and depressions (Figure 10.1) Within each type, there are several subtypes of peculiar morphogenetic character A consequence of the different types of substratum development is the varied properties of the soil and relief which, in combination with the climate, are responsible for local peculiarities of vegetation

The original vegetation of Wielkopolska was forests (Wojterski et al 1978, Wojterski et al 1981) On relatively fertile soils of flat and undulating morainic

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plateaus, dry-ground forests developed, whereas on higher valley terraces and out-wash deposits poor habitats of mixed and pine forests grew Periodically flooded, the bottoms of river valleys were covered with riparian forests, while small, fre-quently peaty depressions with little or no runoff supported alder carrs Original vegetation in individual landscape types is shown in Table 10.1

In the first phase of human history, man was an element of the structure of natural ecosystems From the point of view of the flow of matter and energy, those were

1 — glacifluvial, 2 — glacial, 3 — periglacial Landscapes of hills and heights:

4 — glacial and glacifluvial Landscapes of valleys and depressions: 5 — flood plains, 6 — higher fluvial terraces, 7 — swamp plains Landscapes strongly transformed anthropogenically: 8 — compact urban and industrial developments,

9 — strip-mining of lignite (Adapted from Kondracki 1997.)

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Subregional

Natural-Geographical

Units

Dominant Sediment Type

Dominant Natural Landscape Type

Dominant Associations

of Potential Natural Vegetation

Percentage

of Forests

Prevailing Tree Species in Tree Stands

Pradolina Warty

[Pre-Valley of the Warta River]

Sands of fluvial terraces, alluvial soils and sands, peats

Flood plains, terraces with dunes

Leucobryo-Pinetum Ficario-Ulmetum

Oak 2.0%

Beech 0.5%

Alder 2.2%

Puszcza Notecka

[Wood of the Note River]

Outwash deposits, sands

of fluvial terraces, alluvial soils and fluvial sands, eolian sands

Terraces with dunes, flood plains

Oak 1.1%

Beech 0.3%

Alder 1.5%

[Plain of Nowy Tomy l and Kargowa]

Sands of fluvial terraces, alluvial soils and fluvial sands

Terraces with dunes, outwash, lake district

Leucobryo-Pinetum Pino-Quercetum

Oak 3.6%

Beech 0.6%

Alder 4.0%

[Valley of the Middle-Note c´ ]

Peats, alluvial soils and fluvial sands

Flood plains, terraces with dunes

Pojezierze Wielkopolskie

[Wielko p olskie Lake District]

Glacier tills, morainic sands with boulders

Oak 7.4%

Beech 0.4%

Alder 4.7%

Sandry Gnie nie skie

[Outwash Plains of Gniezno]

district

Oak 5.7%

Alder 4.8%

Dolina Koni ska

[Warta Valley by Konin]

Sands of fluvial terraces Terraces with

dunes, flood plains

Oak 0.5%

Alder 3.0%

Dzielnica Krotoszy ska

[District of Krotoszyn]

Glacier tills, glacial sands with boulders

Oak 23.6%

Beech 0.3%

Alder 5.3%

Source: Adapted from Trampler et al 1990.

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self-regulating systems that were characterized by a long-term balance between the production of biomass and its conversion into energy (Pianka 1974) In those early days, similar to other organisms, man was totally dependent on the supply of food and on other environmental factors

DEVELOPMENT OF AGRICULTURAL LANDSCAPE

Agriculture is the form of human activity that has had a decisive impact on the landscape throughout history The origins of agriculture are related to the Neolithic revolution, or the process of transforming societies of hunters and gatherers into semi-settled and settled societies of food producers It is widely accepted that in Wielkopolska the process began over 6,000 years ago, when the agricultural land-scape began to emerge and later expand at the expense of the natural landland-scape over the next centuries The earliest cultivated areas appeared in well-watered places where soil was light and medium-cohesive, next to lakes and in river valleys, and connected to the regulation of ground water

According to Kurnatowski (1975), the share of the agricultural landscape did not exceed 10% in Wielkopolska in the 10th century Later, settlement moved to higher areas, a tendency that became more conspicuous in the 13th century

(Dunin-W sowicz 1974) The reason behind the move was a rapid growth of population and increased felling of forests, in particular, for constructing strongholds Continued felling reduced the share of forests in Wielkopolska to 50 to 60% in the 14th century (H ady owicz 1932, B aszyk 1976)

The consequences of forest clearings included a change of river regimes and more frequent overflooding which, in turn, made it necessary to move settlements

to higher ground, leaving valley bottoms to renaturalize slowly Larger portions of the natural landscape survived on the bottoms of large river valleys until the late phase of the self-supportive economy The retreat of settlements from river valley bottoms meant a forced change in, but not abandonment of, the cultivation of hydromorphic soils An important role in the expansion of the agricultural landscape

in wet areas was played by Cistercian monks, who arrived in Wielkopolska in the 12th to 13th centuries The second phase of the expansion took place in the 17th and 18th centuries, when settlers from western Europe, mainly from Holland, came

to Poland Their settlements (in Polish ol dry) were established on wet wastelands that they subsequently cultivated Cultivation works were most intensive in the last decades of the 18th century because of large-scale river regulations increasing the runoff rate

A peculiar trait of self-supporting economy was the multiple use made of indi-vidual kinds of farmland that are clearly kept separate today Animals, for instance, were grazed not only on pastures but also on winter crops, in forests and on meadows Agroecosystems also had forests as an element They were a source of animal feed (acorns, mast, young tree shoots) and a grazing area Intensive use of forests by selective tree felling and grazing degraded these ecosystems, resulting in their changing into heathland

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A common trait of different agricultural systems throughout this period was a self-supporting type of economy It was characterized by the absence of external, anthropogenic feeding of agroecosystems with matter and energy The fertility of soils in self-supportive land cultivation systems was maintained by burning sponta-neous vegetation (swidden farming), fertilizing with livestock excrements and nat-ural regenerative processes (fallow farming) (Kostrowicki 1973) With growing population and developing farm produce market, the output of biomass from agro-ecosystems grew, while there was no external feeding with nutrients In consequence, soil productivity fell, making it necessary to begin cultivating ever-newer land at the expense of the natural forest landscape This process continued in Wielkopolska until the first decades of the 19th century, when farmlands reached their greatest acreage According to different sources, in the early 19th century forests in Wielkopolska occupied as little as 20% of the land (Baur 1842, Janczak 1965) From 1801 to 1806, Meitzen (1868–1871) specified the structure of land use in what was then the Grand Duchy of Posen (an area roughly corresponding to Wielkopolska) in the following manner: meadows, pastures, used forested areas and wastelands made up 69.6%, 23% was taken up by arable land, and only 7.4% were covered by forests It can be estimated that over half of the region’s area was taken up by extensively used elements

of the agricultural landscape, including forest pastures and land lying fallow

In the 19th century, a new quality emerged in the human impact on the environ-ment owing to the departure from the self-supportive economy and the growth of external feeding of agroecosystems with matter and energy The main reasons were the introduction of artificial fertilizers and mechanical draught The result was a stop

to oligotrophication of agroecosystems and a more intensive land use The main stimulus of the change in agriculture was the emancipation of peasants and a gradual drawing of them into the system of market economy Wielkopolska was at that time within the borders of Prussia, where agrarian reforms were introduced in the 1820s and 1830s Economic and ownership changes were reflected in the landscape by the shrinking of wastelands and the more intensive use of agricultural and forest eco-systems In 1864, the share of wastelands in Wielkopolska was estimated at 16,500 ha (0.1% of the region) (Meitzen 1869–1871); however, among the very extensively used areas one has to consider lands classified as pastures (6% of the region) At the same time, the share of arable land reached 60% However, it must be considered that some of this area lay fallow Fallow farming was replaced by crop rotation in Wielkopolska in the course of the second part of the 19th century This change was reflected in the landscape from which wastelands disappeared and were replaced by arable land, whose share increased by 25% (Klein 1973) Arable lands reached their greatest share in 1921 when they occupied two thirds of the region’s area The reason behind this increase was the food shortages during World War I and immediately afterward

Another feature of the agricultural landscape is the size structure of individual holdings In the 19th century, only 30% of farmland was taken up by small peasant holdings Complexes of them made enclaves among huge estates of great landown-ers Dramatic changes in the structure of individual holdings were brought about by parcellation, which affected the largest holdings in the period from Poland’s regaining

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of independence in 1918 until World War II As a result, the proportions were reversed and the share of small peasant holdings exceeded two thirds The size structure of individual holdings that ensued then has not changed much until this day

A peculiar trait of the evolution of Wielkopolska’s agricultural landscape over the last 200 years is the elimination of infertile sandy lands from cultivation and instead afforesting them The forests only slightly contracted in the 19th century, but profound structural changes did occur in their distribution In the wake of the Napoleonic Wars, Prussia suffered from a deep economic crisis A shortage of capital made many owners cut down their forests This practice was further encouraged by the development of industry and a growing demand for timber At the same time, the government encouraged afforestation, which became particularly intensive in the latter half of the century What was afforested were heathland and the poorest, sandy cropland; they were planted with fast-growing conifers, particularly pine Since the 1920s, the percentage of arable land has been on the decline, while the share of forests has been growing According to statistics, from 1921 to 1973 forested areas grew by almost 170,000 ha in the voivodeship of Wielkopolska making the percent-age of forests rise from 18.1 to 23.5% Later, however, the share of forests remained stable Afforestations carried out in the period between the two world wars were primarily a consequence of a difficult situation in agriculture and unprofitability of farming on the least fertile soils

After World War II, a sizeable amount of afforestation was necessitated by errors

in methods of farming on sandy soils belonging to state-owned or collective farms

In an effort to maximally increase crop yield at minimum outlays, it was a common practice to use large doses of fertilizers, in particular ones with nitrogen, and to abandon fertilizing with manure Such a cultivation of light sandy soils led to a dramatic decline in organic content of soil and its rapid depletion Consequently, afforestation was necessary to reclaim the soils

A good illustration of this process is the change in the landscape structure in the

Wielkopol-ska (Figure 10.2), where forested areas grew by as much as 60% Such intensive afforestation was a result of the prevalence of poor soils in the poviat

Next to tree felling, changes in water relations are a major influence exerted by agriculture on the landscape The present state of the landscape owes much to the regulations of the Odra, Warta, Note , and Obra rivers, increasing the runoff rate Vast regulation projects were undertaken in the last quarter of the 18th century making approximately 200,000 ha of valley bottom part of agroecosystems (Henning

1979, Falkowski and Kar owska 1961) Betterment drainages of land were continued until modern times; their intensity has noticeably decreased only recently The area where betterment drainages have been carried out exceeds 1 million ha, i.e., 55%

of farmland, in the voivodeship of Wielkopolska The disappearance of water mills, sawmills and fuller mills, the functioning of which required retention of water to drive the machines, also contributed to the dehydration of the landscape It is estimated (Go aski 1980) that in the late 18th century, in the lower Warta drainage alone, there were 420 such establishments; after only 150 years they were almost entirely gone

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Human activities aimed at increasing the rate of water runoff from ecosystems have led to profound, qualitative changes in the landscape of Wielkopolska (Kaniecki 1991) One such change is the lowering of subsurface water, by several dozen centimeters, to two meters Another is the lowering of lake surfaces by 13% on the average, between 1890 and 1980, which is evident from cartographic analysis However, the process was much more rapid in the case of small lakes (up to 20 ha), where the decline in surface area reached 50% The smallest bodies of water (up to

1 ha) tended to disappear totally; from about 1890 to 1960, their numbers fell from over 11,000 to around 2,500 Because of drainages, the acreage of farmland has indeed grown, but problems related to the overdrying of land have appeared as well Those problems become more acute with more intensive crop production

The landscape and ecological consequences of anthropogenic changes in water relations led to the hypothesis that Wielkopolska was “turning into a steppe” (Wodz-iczko, 1947) or, to use today’s terminology, that it is drying up Successive studies revealed the following changes in ecosystems:

19th century Legend: 1 — cereal crops, 2 — crops other than cereals, 3 — fallow land, 4 — meadows, 5 — pastures, 6 — forests, 7a — surface waters, 7b — developed areas, roads, 8 — heathland (After Mizgajski 1990.)

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• Hydrological parameters — lowering of low water marks and ground-water table

• Soil properties — overdrying, gleying recession, and a quicker mineralization of organic substance causing a decrease in humus content

• The vegetation cover — elimination of swamp and riparian forests, spread of xerophytes and plant associations typical of dry habitats

• The fauna — decrease in the number of forest species in favor of species living

in an open landscape; appearance of xerophilous mollusk species

The above list of consequences must be supplemented with a list of changes brought about by the elimination of surface waters, such as the disappearance of belts of spontaneous vegetation that serve as biogeochemical barriers deciding the buffer capacities of agroecosystems (Ryszkowski 1999) An illustration of the extent to which this process took place in the second half of the 20th century may be the recorded changes in the landscape surrounding the village of Zamorze, located about

50 km west of Pozna (Mizgajski and Kafel-G bowska 1990) In an area approxi-mately 12 km2, about 50 point and linear changes of topographical landscape ele-ments that occurred in 1940–1982 were recorded The most frequent type of change (27 places) was the drying up of ponds, in part accompanied by burying or removing

of spontaneous vegetation communities surrounding them Twenty cases of drainage ditch burying were recorded, frequently accompanied by the elimination of tree and bush belts growing along them Furthermore, trees were felled along abandoned roads or ploughed field margins (six cases) A clear majority of changes consisting

of the elimination of small landscape elements were direct or indirect consequences

of drainage works carried out mostly in the 1970s In this respect, the example of the village of Zamorze can be treated as representative of the whole of Wielkopolska

PRESENT-DAY CHANGES IN AGRICULTURAL LANDSCAPE

Present-day intensive farming is characterized by extremely heavy inputs of matter and energy into agroecosystems by man This is clearly seen in very high doses of artificial fertilizers Moreover, the rise of large pig farms using industrial feeds resulted in breaking earlier systemic ties between crop and stock farming Farmers ceased to rely on the supply of manure from their own animals for crop cultivation, replacing it with artificial fertilizers and catch crops Owing to industrial feeds, the size of a stock farm ceased to be dependent on the amount of feed produced

by the farm, i.e., on the acreage of cropland Furthermore, farmers, who were earlier bound to their farms, which were the sources of subsistence, turned into workers supplying labor, while the farms ceased to be sources of produce for them Thus, agroecosystems changed from closed systems dominated by stabilizing internal flows

of matter and energy into open systems, where external relations are of primary importance (Mizgajski 1990) Any errors in controlling such systems lead to uncon-trollable changes in the landscape

In Wielkopolska, these changes were observable primarily on large state farms that had a priority in the supply of means of production In the 1970s and 1980s, the use of artificial fertilizers grew rapidly in such farms, accompanied by the rise

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of large animal herds This increased the significance of agricultural nonpoint pol-lution leading to the eutrophication of ecosystems and landscape effects such as the disappearance of lakes This process continues despite the fact that agriculture became less intensive in the 1990s The change of the political system in Poland initiated the process of profound socio-economic changes in rural areas Subjecting agriculture to market pressures and abolishing subsidies to great state-owned farms resulted in an overall decrease in the intensity of land use

Poland’s transition to a market economy consisted mainly of the release of prices, withdrawal of subsidies to businesses, and deregulation of foreign trade As a con-sequence, the ratio between produce prices and those of manufactured goods became less and less advantageous This, in turn, resulted in the lowering of agricultural production intensity due to the shortage of funds for basic means of production, including fertilizers and pesticides In due course, the consumption of fertilizers in central Wielkopolska fell from over 250 kg NPK/ha in the 1980s to approximately

100 kg NPK/ha in the early 1990s The intensity of fertilizer use began to climb again to approximately 130 kg NPK/ha in the late 1990s

Decreased use of fertilizers was not reflected, however, in less eutrophication pressure exerted by agriculture on the environment Go dyn and Grabia (1998) inves-tigated the drainage of the Cybina, one of the smaller tributaries of the river Warta They estimated that from the catchment area of 15,600 ha, the river annually receives almost 120 tons of N and over 5 tons of P as agricultural nonpoint pollution From the point of view of matter flow, the landscape of Wielkopolska is dominated by autonomous areas (plains) with a significant share of allochthonous areas (no-drainage depressions) A smaller share is taken up by sloping areas, known as transit ones As

a result, the ecosystems of the region tend to retain substances introduced to them Consequently, one should not expect that the decline in the use of fertilizers would

be reflected soon in lower numbers of biogens in ecosystems Thus, it can justifiably

be claimed that present-day changes in Wielkopolska’s landscape consisting of the disappearance of lakes are largely caused by eutrophication brought about by agri-cultural nonpoint pollution The landscape changes aggravate the consequences of earlier draining projects that induced irreversible changes in water conditions The high price of the means of agricultural production and the low price of farm produce make farmers more interested in afforestation of the poorest lands Such lands are usually found in large complexes, in areas that already now have a high percentage of forests New afforestations will simplify the landscape by combining forested areas into large forest complexes, whereas good soils will be even more intensively farmed since their afforestation is practically out of the question for economic reasons To counteract the simplification of the landscape-ecological struc-ture of such areas, it is necessary to increase the share of biotopes of seminatural vegetation, specifically by planting trees along field margins and roads Such actions have already been taken in Wielkopolska, and there are plans to continue them (Ryszkowski et al 2000) An important factor influencing landscape appearance is the field structure In Wielkopolska, family farms (a total of 150,000) dominate, occupying in aggregate almost 80% of farmland Their average size is about 7 ha in

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