ECOLOGICAL CONSEQUENCES OF THE POST-SOVIET LAND USE CHANGE IN THE FOREST-STEPPE ZONE OF BASHKORTOSTAN
ЭКОЛОГИЧЕСКИЕ ПОСЛЕДСТВИЯ ИЗМЕНЕНИЯ ПОСТСОВЕТСКОГО ЗЕМЛЕПОЛЬЗОВАНИЯ В ЛЕСОСТЕПНОЙ ЗОНЕ БАШКОРТОСТАНА
P. Liebelt1, M. Frühauf1, R. Suleymanov2, M.A. Komissarov2, D.R. Yumaguzhina3, R.G.Galimova4
П. Либельт1, М. Фрюауф1, Р.Р. Сулейманов2, М.А. Комиссаров2, Д.Р. Юмагужина3, Р.Г. Галимова4
1Martin-Luther University Halle-Wittenberg
(Germany, 06120-Halle, Von-Seckendorff-Platz 4)
2Ufa Scientific Center of the Russian Academy of Science
(Russia, 450054, Republic of Bashkortostan, Ufa, pr. Oktyabrya, 71)
3Bashkirian State Agrarian State University
(Russia, 450001, Republic of Bashkortostan, Ufa, 50th Anniversary of October st., 34)
4Bashkirian State University
(Russia, 450076, Republic of Bashkortostan, Ufa, Zaki Validi st., 32)
1Галле-Виттенбергский университет имени Мартина Лютера
(Германия, 06120, г. Галле, Университетская пл. 4)
2Уфимский научный центр Российской академии наук
(Россия, 450054, Республика Башкортостан, г. Уфа, пр-т Октября, 71)
3Башкирский государственный аграрный университет
(Россия, 450001, Республика Башкортостан, г. Уфа, ул. 50-летия Октября, 34)
4Башкирский государственный университет
(Россия, 450076, Республика Башкортостан, г. Уфа, ул. Заки Валиди, 32)
e-mail: peter.liebelt@geo.uni-halle.de
The steppes and forest steppes of Baskortostan are intensivly used and degradated ecosystems. In the frame of an interdiscilpinary and international reserach project the steering factors of post-Soviet agrarian land use change and their impacts on the soil degradation and rehabilitation were investigated. Particular attention was given to the effects of new technologies on soil degradation indicators and the soil water budget as well as land use potential. In field studies significant environmental and economic effects by changing of agricultural land use quality and intensity were revealed even after short time. These findings show that based on the knowledge of the functional relationships between the intensity and type of land use as well as the pedological consequences great potential arises for the development of strategies for sustainable land use with special reference to specific climatic conditions and climate change. The positive effects of conservation tillage strategies on soil water balance, which particularly occurred in years with long dry periods (droughts) implies that extensive crop farming strategies which based on reduction in tillage intensity might constitute an important measure for climate-optimized land use. In addition, there are economic arguments for more extensive crop farming strategies too.
Степи и лесостепи Башкортостана находятся под интенсивным использованием и являются деградированными экосистемами. В рамках междисциплинарного и международного исследовательского проекта были изучены факторы изменения постсоветского аграрного землепользования и их влияние на деградацию и восстановление почв. Особое внимание было уделено воздействию новых технологий на показатели деградации почв, на водный баланс почвы, а также на потенциал землепользования. В полевых исследованиях, при изменение качества и интенсивности использования сельскохозяйственных земель, даже после короткого времени, были выявлены значительные экологические и экономические последствия. Результаты показывают, что основанный на знании функциональных связей между интенсивностью и типом землепользования, а также влияния на почву, появляется огрмный потенциал для разработки стратегий устойчивого землепользования с особым вниманием на спецефические климатические условия и изменение климата.
Положительные эффекты стратегий сохранения почв на водный баланс почвы, которые особенно характерны для лет с засушливыми периодами (засухами), предполагает, что экстенсивные стратегии земледелия, которые основаны на уменьшении интенсивности обработки почвы, могут стать важной мерой для оптимального к климату землепользования. К тому же, имеются экономические аргументы в пользу более экстенсивных стратегий земледелия.
Introduction
Although Russia is the country with the largest area in the world, it has, due to its specific geographic position, a proportionately small area, which can be used for agricultural purposes (13%), esp. for arable farming (7%) [16]. Among all regions, most suitable for agricultural use is the forest-steppe zone, which is, consequently, subjected to a heavy pressure of exploitation [2].
The Republic of Bashkortostan, on the border between European and Asian part of Russia, geographically encompasses great portions of the forest-steppe zone of Russia (Fig. 1) and, by this, constitutes one of the main agrarian regions of the country [9].
Especially the fertile chernozem, which dominates this landscape zone, determines this area´s suitability for arable farming. The climatic conditions are characterized by a high continentality and periodic droughts that have a limiting effect on crop yield [6].
During the Soviet land use epoch, especially under the new agrarian politic of virgin land campaign (1954-1963), a considerable intensification of the agrarian land use took place in Bashkortostan [1, 9]. However, the way of land use, not sufficiently adapted to the natural conditions, and its intensity led to an increasing degradation (Fig. 2) of soils, which manifested itself in a decrease of soil fertility and, particularly strong, especially in the increase of water erosion [5].
After the break down of the Soviet Union, new economic and political framework conditions,
as well as climate change led to new patterns in the complex interaction between land use and soil degradation, out of which arose, in turn, new ecological as well as economic consequences [1, 3, 14].
MethodsWith regard to land use, three major trends can be highlighted: 1) decrease (Fig. 3) in arable land, 2) conversion of arable land to grassland (based on resolution issued by the State Committee on Land Resources of the Republic of Bashkortostan and the Ministry of Agriculture and Food [8] and 3) minimization of soil tillage intensity. This results lead to an increasing heterogenization of agricultural use and in new condition for soil degradation or rehabilitation. An important research question in this context was whether the new soil-conserving agriculture systems are better adapted to the climatic and pedological conditions than the conventional one and which role they could play for soil restauration, a better soil stability and stable or higher yield. This questions have been addressed by the two interdisciplinary research undertakings sponsored by the VW foundation («Development of Land Use and Soil Degradation and their Consequences for the Forest Steppe Zone of Bashkortostan» (2007-2009) and «Consequences of (post-socialist) land use and climate change for landscape water budgets, soil degradation and rehabilitation in the forest steppe zone of Bashkortostan» (2010-2013). Herewith we want presenting some results.
To study the effects of new land use types and different intensities on soils, in particular soil degradation and soil water balance, field trials were carried out at the enterprise «Artemida» unter the landscape conditions of the forest steppes soils 40 km south-west of Ufa. Here could be compared traditional (long term) ploughing and no tillage in his conseqeunces for-especially soil water budget under variable (annual) meteorological conditions of 3 years.
Setup of the research location
At the research location «Artemida», field tests consisting of 4 plots with diverse tillage intensities were carried out (Fig. 4). The tillage intensity was gradually increased from plot A1 up to plot A4. The crop culture used since the beginning of research in 2010 has been spring grain. Test plot A1 is managed by the direct seeding method (No-Till method). Contrary to the cultivated plots A2 and A3, the soil on plot A4 is turned around to get loosened. Test plot A5 was setup as a reference plot to simulate natural conditions. The soil on that plot has not been tilled for more than 10 years, so, due to natural succession, by this time it is covered by a rampant herb and shrub layer. On the test plots, regular measurements of the physical and chemical soil parameters were carried out.
Soil water content and soil temperature were measured on the test plots with a high temporal resolution by means of stationery FDR-probes and soil thermometers. In order to measure precipitation, a Hellmann rain gauge was installed. The FDR-measuring probes were installed in the depths of 20 cm, 40 cm, 60 cm, 80 cm and 100 cm (Fig. 4).
Additionally, mobile FDR-measuring probes were applied to measure the profile cut with a depth of 0-50 cm. These measurements were carried out on test plots A2-A5 with an interval of 10 days with a two-fold repetition.
Results about the impact of the different strategies of soil tillage on the soil moisture dynamic with regard to the specific climate conditions and climate change
The field analysis based on descriptive statistics of the measurements of the soil water content carried out by means of the FDR-probe (measurement interval: October 2010–October 2012, number of measurements per test plot: 84) shows that the samples` value distribution varies according to test plot. The focus of the data analysis has been on the lower part of the value distribution, because, due to spatial proximity of the research area to the agronomic drought determined limit, water shortage is an important factor of limitation for agricultural production in the research area. The Boxplot-diagram (Fig. 5/6) illustrates the distribution of the measurements of the absolute soil water content in the A-Horizon in a depth of 0-50 cm.
It becomes clear that all relevant central tendencies of the frequency distribution of the values of the absolute soil water content show a rising gradient from plot A4 over plot A3 to plot A2, thus, with a decreasing intensity of tillage. The median value, for example, rises from 121,2 mm on plot A4 (conventional tillage) to 131,6 mm on plot A2 (minimum tillage), which is equivalent to an increase of 10,4 mm / 8,6% (Fig. 6).
This gradient can also be found in the studied near-surface layers: 0-10 cm, 10-20 cm and 20-30 cm of the A–horizon and is most clearly pronounced in a soil depth of 10-20 cm (Fig. 6). The median value increases in this depth from 18,6 Vol. % (plot A4) by 9,8 Vol. % to 28,4 Vol. % (plot A2). Even more striking is the increase of the 25% percentile. Under conventional tillage (plot A4), the 25% percentile of the measurements amounts to 11,4 Vol. %, and under minimum tillage (plot A2) – distinctively higher to 21,5 Vol.
When comparing the soil water content throughout the growing seasons 2011 and 2012, it becomes apparent that the soil moisture gradient, which has been present in the upper 30cm of the soil throughout the entire period 2011-2012, has been much more apparent during the growing season 2012 than in 2011 that is caused by the dryer wether conditions (drought) in 2012. Fig. 7 reflects the temporal dynamic of the relative volumetric soil water content on test plots: reference plot (green), Cenius-plot (blue) and plough (grey) for the growing season 2012. At the beginning of the growing season, up to around the middle of May, the soils of the test plots in a depth of 20 cm show a similarly high soil water content of around 40 Vol. %, which lies slightly above the maximum field capacity (37-39 Vol. %) of the soils. The high amount of soil water has been caused by the ending of the snowmelt period in April, which allowed great amounts of water to infiltrate the soil. The equivalent of the snow cover in water before the beginning of snowmelt amounted to approximately 90 mm. During the course of May, a drying of the soil occurred as a result of relatively dry weather conditions and increasing air temperatures. From then on, diverse courses of the development of soil moisture began. While the soil water content on the conservationally cultivated plot A3 decreased only moderately, it drastically fell on the conventionally tilled plot A4. On June, 6th, the soil water content on plot A3 was already 11 Vol. % higher than on plot A4.
This difference between the plots remained until the end of the growing season. In order to identify the reasons for these clear differences it is necessary to examine the factors influencing the soil water content in more detail.
Climatic factors of influence. One of the reasons for the unequal value distribution of the soil water content, as well as differences in its temporal dynamic between the growing seasons (April-September) 2011 and 2012, is provided by differences in the climate conditions during the research. These differences are reflected in the verified climate water balance (CWB). It can be concluded from the CWB that due to climate conditions the water input into the total soil water content in 2011 was higher than in 2012. In spring as well as during the entire growing season of 2011, the water input into the total soil water content through melt-water and precipitation was considerably higher than in 2012. The year 2012 was an unusually dry year. Apart from a considerably smaller snow cover in spring (water equivalent 2012: 90 mm; vs. water equivalent 2011: 155 mm), distinctively less precipitation fell during the growing season (N during growing season 2012: 265 mm; vs. N during growing season 2011: 315 mm). Precipitation occurred mostly in form of short heavy rain and did not lead to a discernable reaction or an increase in soil water content in soil layers below 20 cm. This can be explained by interception and evaporation losses as well as surface runoff on slightly sloped test areas. The impact of evaporation losses, especially under dry climate conditions, on the total soil water content can be concluded from a negative correlation between soil temperature and the soil water content during the growing season 2012, as soil temperature has a strong influence on evaporation. The correlation is stronger on the conventionally tilled plot (A4) than on the conservationally plot A3. This can be interpreted as a stronger sensibility of the soil moisture towards soil temperature and, by this, towards evaporation, on the ploughed field than on the conservationally tilled test plot A3. The comparison between the climatic conditions and the soil water dynamic as well as the value distribution of the soil water content leads to the conclusion that dry climatic phases and periods of drought intensify the positive effects conservation soil cultivation has on the total soil water content. The analyses of climate data by the institute «Bashgidromet» carried out by the working group BSU indicate different climate trends, such as an increase of the average air temperature and a decrease in the sum of precipitation, which take place during the growing season in southern near-steppe regions of the forest-steppe. This gives rise to increasing aridity, which could – according to our project results – best be countered by conservation tillage, due to its more favourable soil water dynamic.
Pedological factors of influence resultingout of tillage
Apart from climate, tillage, as well as the resulting changes of the soil properties, constitutes a control quantity influencing the soil water content. Physical and chemical soil properties, as well as the thereout resulting factors relevant for the soil water content such as the rate of infiltration and evaporation, have been examined.
Of a special relevance for infiltration are the physical parameters of soil: type of soil and soil structure, because these factors determine the development of the soil pore system, which is responsible for water transport [7, 15, 19]. Depending on the size of the pores, different forces act influencing the transport of soil water and, hence, infiltration. Penetrometer measurements in year 2012 indicate that the bulk density in the upper 30cm soil layer under classic tillage (plot A4) is lower than when preserving tillage is applied (plot A3/A2). This accounts for the fact that under intensive mechanical soil loosening pores and hollow spaces between the aggregates are created, which can result in an increase of infiltration (Fig. 8). According to Ehlers (1996), the increase of the infiltration coefficient is determined by a number of factors. On the one hand, increased surface roughness, which can be achieved through soil loosening, leads to an increase in infiltration. On the other hand, a great number of coarse probes between the aggregates have the same effect. Analyses of infiltration show that the water in the upper layer on the plough variant has the highest rate of infiltration (Fig. 9).
Summary and outlookThus, it can be concluded that ploughing has had a positive effect on infiltration of the upper soil layer. Nevertheless, conventionally tilled soil is exposed to a higher risk of disaggregation, which entails a decrease in infiltration [4, 7, 17]. Experiments on the aggregate stability on the test plots have revealed that when ploughing has been applied, aggregate stability has been the lowest in comparison to the rest of the plots. Nonetheless, aggregate stability on the plough variant was still on a high level. Infiltration is especially important in spring during the snowmelt, because it determines the amounts of melt water, which can be absorbed by the soil and which portion runs off the surface and, by this, can evoke erosion.
The investigation has revealed that the soil water dynamics can be differentiated according to the method of tillage and climatic conditions, which brings along consequences for agricultural production. In year 2011, there has been a sufficient water input due to weather conditions so that the positive effect of minimal tillage has not become visible to its full extent.
The high temporally resolution measurements of the soil water content allow to conclude that a minimization of tillage in light of the increasing aridity of the climate (Data by Bashgidromet, 2011) in the southern regions of the forest-steppe zone can lead to an increase in the soil water content and, thus, to a stabilization of crop yield. Therefore, conservation tillage in the near-steppe forest-steppe regions constitutes a suitable measure to adapt the agriculture to the ongoing climate change.
Under these conditions, the highest yield has been achieved on the conventionally tilled plot A4, which can be explained by a number of factors of ploughing, such as the high rate of mineralization, low bulk density as well as a favourable seed-bed ensilage [12]. Under the very dry weather conditions of year 2012, an opposing image of the yield situation arises. The low climatic water input and the ability of the conservationally tilled plots (A3 and A2) better to accumulate water have led to the outcome of a higher yield (up to 65%) on conservationally tilled plots than on the conventionally tilled plot. Thus themeasurements at the test side of the Artemida Company confirm the results of the analyses of agro-economic effect of agricultural companies that apply different cropping systems.
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