The vast grassland areas of Inner Mongolia are part of the Eurasian steppe ecosystem and characterized by a semi-arid climate with average annual rainfall of 335 mm, ranging between 210 and 530 mm (Figure 2). Perennial C3 grass species, such as Leymus chinensis Trin. Tzvel., Stipa grandis P. Smirn., Agropyron cristatum L. Gaertn. or Carex korshinsky Kom., are the dominant species in plant communities of this widely
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Figure 2 Pre-growing season (September-March), growing season (April-August) and annual precipitation (September- August) from 1983 to 2006. Solid line, dash line and dash-dot line denote the mean precipitation amount from 1983 to 2006 for pre-growing season, growing season and annual pre- cipitation respectively.
degraded grassland ecosystem (Schˆonbach et al., 2009; 2011; Wan et al., 2011). Inner Mongolian grasslands have always been grazed by livestock; in former times by wild animals and in more recent decades by domestic herbivores such as sheep, goats and cattle. However, since the 1950s, grazing management has been subjected to a dramatic shift from pastoral nomadism to sedentary livestock farming. This shift in grazing system was accompanied by sharply increasing stocking rates (Wang and Ripley, 1997; Zhou et al., 2007; Butterbach-Bahl et al., 2011). The economic reform of China began in the late 1970s and has led to a further rapid expansion of livestock (Figure 3) resulting in degradation and declining primary produc- tion in most of the grasslands on the Inner Mongolia Plateau in northern China (Zhou et al., 2007). Both non-adapted grazing management strategies and excessive stocking rates have exceeded the sustainable carrying capacity of this grassland and thus have led to a rapid decrease in soil cover through the removal of herbage by grazing animals. A reduction or loss in the soil protecting litter layer necessarily increases the risk of soil erosion and depletes soil organic carbon stocks and thus induces degradation processes. More than 70% of the Inner Mongolian steppe area has now become degraded, and there are serious con- straints for livestock management (Ren et al., 2008; Lin et al., 2011) and ecosystem functioning (Bai et al., 2008; Wan et al., 2011). In this context, recent studies have highlighted the negative impact of intensive grazing on biomass production and diversity as well as on livestock performance (Zhou et al., 2007; Glindemann
et al., 2009; Schˆonbach et al., 2009; 2011; 2012; Wan et al., 2011). Overgrazing seriously impedes multifunc- tioning of grasslands, e.g. through decreasing primary and secondary production, depleting soil organic car- bon stocks, and through diminished habitat and spe- cies diversity. Within the framework of a Sino-German research cooperation programme [Matter Fluxes of Grasslands in Inner Mongolia (MAGIM)], degradation processes in semi-arid Inner Mongolian grassland have been studied during 2004-2012. Research activities mainly focused on the improvement of current grazing man- agement strategies aiming at sustainable maximization of primary and secondary production, i.e. 'sustainable intensiﬁcation'. A large-scale grazing experiment was conducted to test whether annual alternation between grazing and hay making (Alternating System) may provide higher productivity compared with the current system of continuous spatial separation of grazing and hay making (Continuous System). The effect of man- agement systems in terms of sustainable intensiﬁcation was tested along a wide gradient of grazing intensities from ungrazed to very heavily grazed. The results sug- gest that, compared to the Continuous System, alter- nating grazing (Alternating System) provide signiﬁcantly higher aboveground primary productivity (Figure 4) and soil protection (Figure 5) at high graz- ing intensities (Schˆonbach et al., 2011). Furthermore, botanical composition was less adversely affected by grazing in the Alternating System than in the Contin- uous System (Wan et al., 2011). However, land use of grasslands in northern China is currently governed by agricultural industrialization contradicting the aims of sustainable intensiﬁcation (Cui and Lui, 2006). Both the increasing demand for food of animal origin and the limited availability of agricultural area have resulted in a substantial short- age in agricultural land resources (Figure 3). Thus, potential increases in agricultural production largely depend on intensiﬁed farming. Since the end of the 1990s, intensiﬁed production through agricultural industrialization management has become a typical rural development strategy by the Chinese govern- ment (Zhang et al., 2011). The strategy of land-intensive farming has also been applied in environmentally sen- sitive areas, such as the widely degraded grasslands of Inner Mongolia. In this region, much effort has recently been put into the promotion of dairy farming. Thus, not only has the number of small ruminants increased in recent decades (Figure 3), but in the more recent past, the number of dairy cows increased by around 20% per year (Cui and Lui, 2006; Zhang et al., 2011). Today, northern China with its vast grassland resources has become the major milk- producing region in China, with Inner Mongolia as the number one producer of raw milk. During the last decades, dairy farming in Inner Mongolia has faced a substantial increase in milk production of more than 1200% between 1980 and 2006; i.e. the output of raw milk increased from 07 million tonnes to 88 million
tonnes within the respective time period (Table 1). Thus, the contribution of Inner Mongolia to the total raw milk production of China increased between 1980 and 2006 from 5 to 26%. The Inner Mongolia govern- ment has strongly advocated expansion of the dairy industry and encouraged farmers into contracts with dairy processors. However, animal nutrition is a major constraint for dairy farming in Inner Mongolia as pro- ductivity of the widely degraded grassland is relatively low and most grass species provide insufﬁcient nutri- tion for dairy cows, even during the growing periods in summer (Cui and Lui, 2006; Schˆonbach et al., 2009). Small ruminants such as sheep and goats are well adapted to these limited conditions, whereas high-yielding dairy cows require measures to compen- sate for nutritional deﬁciency. To meet the nutrient requirements of dairy cattle and to protect the grass- land from further grazing pressure, conﬁnement dairy systems are being promoted by the Chinese govern- ment (Cui and Lui, 2006). Therefore, the shift in live- stock farming from grassland-based systems using small ruminants (sheep and goat) to grassland-inde- pendent dairy production systems results in substantial feedstuff imports into this region, such as soybean meal, palm kernel cake or wheat (Cui and Lui, 2006; Zhang et al., 2011). Imports affect regional nutrient budgets with serious constraints on ecosystem func- tioning. Increasing the production of slurry and man- ure results in environmental hazards to water and air quality, because so far, most dairy farmers have no adequate means of managing the excreta from their cows, and this is commonly deposited near the farm- houses. Furthermore, grasslands are being converted into arable land with the aim of cultivating forage crops, and these are commonly irrigated using fossil groundwater resources (e.g. Cui and Lui, 2006; Hu, 2009).
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John et al. (2009) evaluated land-use changes in Inner Mongolia for a 12-year period (1992-2004), and they showed that grasslands, comprising savannah, shrubland and other grassland, decreased in area by 72 911 km² ( 10%), while croplands increased by 66 146 km² (+78%). Both overgrazing and conversion of grassland into arable land increase the risk of soil erosion and release large amounts of CO2 through depleting soil organic carbon stocks (Zhou et al., 2007). Arable farming on former grasslands in such arid or semi-arid ecosystems requires comprehensive irrigation with fossil groundwater, thus requiring the construction of water wells and irrigation systems. A consolidated view of all these factors indicates that intensiﬁed, industrialized dairy farming in Inner Mongolia hardly meets the idea of a sustainable agri- cultural production. Intensiﬁcation and industrializa- tion of dairy farming have boosted the demand for protein-rich feedstuff, primarily soybean meal. Global ﬂows of agricultural commodities are well docu- mented, identifying China as the world's largest importer of soybeans. Around 35% of the South American soybean production is exported to China to meet their demand of 50 million tonnes per year (FAOSTAT, 2012). However, the boost in global demands has led to a tremendous expansion in soy- bean cultivation areas in South America, predomi- nantly through the conversion of rainforest (in Brazil) and grassland (Argentina and Brazil) into arable land (Dalgaard et al., 2008; Gerber et al., 2010). To assess the sustainability of dairy farming systems worldwide, it is essential to consider both direct and indirect effects of an outsourced feedstuff production, e.g. by answering the question of what are the main environ- mental impacts of cultivation, processing and transport of soybean meal originated from South America?
Abstract | Materials and methods | Results | Discussion | References | Abstract | Background | Sustainable intensiﬁcation - changing paradigm in forage production | Sustainable intensiﬁcation of dairy farming - the speciﬁc role of grassland- based forage production | References |