Landscape Ecol (2016) 31:547–566 DOI 10.1007/s10980-015-0261-x RESEARCH ARTICLE Differentiating anthropogenic modification and precipitation-driven change on vegetation productivity on the Mongolian Plateau Ranjeet John . Jiquan Chen . Youngwook Kim . Zu-tao Ou-yang . Jingfeng Xiao . Hoguen Park . Changliang Shao . Yaoqi Zhang . Amartuvshin Amarjargal . Ochirbat Batkhshig . Jiaguo Qi Received: 12 February 2015 / Accepted: 17 August 2015 / Published online: 28 August 2015 Ó Springer Science+Business Media Dordrecht 2015 Abstract Objectives This study distinguished between Context The Mongolian Plateau, comprising Inner human-induced and precipitation-driven changes in Mongolia, China (IM) and Mongolia (MG) is under- vegetation cover on the plateau across biome, vege- going consistent warming and accelerated land cover/- tation type and administrative divisions. land use change. Extensive modifications of water- Methods Non-parametric trend tests were applied to limited regions can alter ecosystem function and the time series of vegetation indices (VI) derived from processes; hence, it is important to differentiate the MODIS and AVHRR and precipitation from TRMM impacts of human activities and precipitation dynam- and MERRA reanalysis data. VI residuals adjusted for ics on vegetation productivity. rainfall were obtained from the regression between growing season maximum VI and monthly accumu- lated rainfall (June–August) and were used to detect human-induced trends in vegetation productivity dur- ing 1981–2010. The total livestock and population Electronic supplementary material The online version of this article (doi:10.1007/s10980-015-0261-x) contains supple- mentary material, which is available to authorized users. R. John (&) Á J. Chen Á Z. Ou-yang Á Y. Zhang H. Park Á C. Shao Á J. Qi School of Forestry and Wildlife Sciences, Auburn Center for Global Change and Earth Observations, University, Auburn, AL 36949, USA Michigan State University, East Lansing, MI 48823, USA e-mail: [email protected] A. Amarjargal Department of Economics, University of the Humanities, J. Chen Á Z. Ou-yang Á J. Qi Ulaanbaatar 210620, Mongolia Department of Geography, Michigan State University, East Lansing, MI 48823, USA O. Batkhshig Institute of Geography, Mongolian Academy of Sciences, Y. Kim Sukhbaatar, Ulaanbaatar 210620, Mongolia Numerical Terradynamic Simulation Group (NTSG)/ College of Forestry and Conservation, The University of Montana, Missoula, MT 59812, USA J. Xiao Earth Systems Research Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH 03824, USA 123 548 Landscape Ecol (2016) 31:547–566 density trends were identified and then used to explain the last 70 years (Liu et al. 2013), and an increasing the VI residual trends. frequency of extreme climatic events in the last three Results The slope of precipitation-adjusted EVI and decades (Groisman et al. 2009; Ferna´ndez-Gime´nez EVI2 residuals were negatively correlated to total et al. 2012; John et al. 2013b; Pederson et al. 2014). livestock density (R2 = 0.59 and 0.16, p \ 0.05) in The plateau consists of Mongolia (MG) and Inner MG and positively correlated with total population Mongolia (IM),—the third largest province-level density (R2 = 0.31, p \ 0.05) in IM. The slope of administrative region in China (Fig. 1). The two precipitation-adjusted EVI and EVI2 residuals were entities (i.e., MG and IM) have similar ecosystem also negatively correlated with goat density types but distinct socio-economic systems, political (R2 = 0.59 and 0.19, p \ 0.05) and sheep density in regimes, ethnic compositions, and divergent land MG (R2 = 0.59 and 0.13, p \ 0.05) but not in IM. cover/use change trajectories (Qi et al. 2012; Chen Conclusions Some administrative subdivisions in et al. 2015b). The major land use on the plateau has IM and MG showed decreasing trends in VI residuals. historically been herding, but cropland use has These trends could be attributed to increasing live- increased in certain areas of IM (Dong et al. 2011; stock or population density and changes in livestock John et al. 2013b) and more recently in north central herd composition. Other subdivisions showed increas- MG (Pederson et al. 2013). Livestock stocking rates ing trends residuals, suggesting that the vegetation increased sharply in MG following the collapse of the cover increase could be attributed to conservation former Soviet Union and the loss of state support, efforts. which drove migration away from cities (Hilker et al. 2014; Chen et al. 2015b). The level of degradation in Keywords Mongolian Plateau Á Semi-arid Á the Mongol Steppe is closely linked with abrupt Vegetation indices Á Precipitation Á RESTREND Á changes in socio-economic policies, leading to a MODIS Á EVI Á EVI2 Á GIMMS3 g NDVI Á Livestock dramatic increase in livestock stocking rates in both density Á Population density MG and IM during the last two decades (Ojima and Chuluun 2008; Li et al. 2012; Liu et al. 2013; Hilker et al. 2014; Chen et al. 2015b). Herders on the plateau have been forced to adapt to extreme weather and Introduction market forces by limiting their traditional frequency of transhumance (otor), becoming sedentary herders The world’s arid/semi-arid biome, which accounts for (more common in IM than MG), and diversifying 41 % of the earth’s land area and where 38 % of the herd composition to minimize risk of livestock human population lives, is vulnerable to ongoing and mortality, all of which has resulted in increased predicted climate change as well as land degradation grazing pressure (Ferna´ndez-Gime´nez 2002; Wang (Reynolds et al. 2007; Li et al. 2012). The grasslands et al. 2013b; Hilker et al. 2014). Extreme climate of the Mongolian Plateau makes up a major portion of events like summer drought and extreme winters or the Eurasian Steppe—the largest, contiguous grass- dzuds, led to the migration of herders to urban areas land ecosystem in the world—and are among the few after record livestock mortality in 2000–2002 (Sankey extant grassland ecosystems with a high diversity of et al. 2009) and again in 2010 (John et al. 2013b; grassland species (Bai et al. 2008; Chen et al. 2013). Hilker et al. 2014). The emergence of a market While there have been many studies that describe the economy and the recent boom in mining partially vegetation, species diversity, and the effects of explain the internal migration in the 2000–2010 environmental stochasticity such as drought and decade, which led to an increase in the urban extreme winters on the Mongolian Plateau, there have population, concentrated mostly in the capital city of been relatively few studies on the vulnerability of the MG, Ulaanbaatar. Similarly, Deng Xiaoping’s reforms Mongolian grasslands to climatic change and anthro- of the 1980s ushered in a market economy in IM, pogenic modification (Hilker et al. 2014; Chen et al. where the agricultural collectives were replaced by 2015a). The temperate steppes of the plateau are under increased privatization of herding and farming (Chen increasing pressure from a 2° rise in average temper- et al. 2015a, b). The last decade saw the introduction of ature, a 7 % reduction in annual precipitation during several grassland conservation measures and green 123 Landscape Ecol (2016) 31:547–566 549 Fig. 1 Land cover map and biome boundaries of the Mongolia are the terrestrial ecoregions (WWF) biome boundaries: desert Plateau. The base map is the MODIS-derived land cover map (I), grassland (II), and forest (III). The heavy, solid line stands with the University of Maryland classification scheme for the political boundary between Mongolia (MG) and Inner (MCD12Q1) for 2010. The polygons delineated by dashed lines Mongolia (IM), China belt schemes to control desertification and to mitigate biomass resulting from anthropogenic modification dust storms originating in IM (Jiang et al. 2006; Liu and large inter-annual precipitation variability are to et al. 2008). study trends in rain use efficiency (RUE) or spatially The identification of various desertification drivers explicit residual trends (RESTRENDS) (Wessels et al. and the separation of anthropogenic drivers from 2007). There are few studies that compared residual climatic effects have long been a topic of contention in analysis results across border regions of large extent semi-arid grassland research. Vegetation dynamics in with similar ecosystem and climate types like the semi-arid grasslands are closely coupled with precip- plateau (Zhao et al. 2014) or linked them with socio- itation variability, which makes it challenging to economic drivers and policy change (Li et al. 2012; distinguish degradation resulting from anthropogenic Chen et al. 2015a). Furthermore, there are no studies modification from vegetation dynamics in water that compared independent RESTREND results limited ecosystems (Wessels et al. 2007). Although obtained from long-term records of VIs derived from several satellite remote sensing methods have been multiple satellite sensors and gridded climate datasets. used to study vegetation degradation using vegetation In this study, we used RESTREND and multiple VI indices (VI) (Kim et al. 2014), the primary methods to and climate datasets to examine the effects of anthro- monitor reduction in grassland canopy cover and pogenic modification and precipitation dynamics on 123 550 Landscape Ecol (2016) 31:547–566 vegetation productivity on the Mongolian Plateau. climate (BSk) in the southwest where potential These state-of-the-art synoptic VI records and evapotranspiration exceeds precipitation and average climate datasets proved to be valuable for facilitat- temperature is less than 18 °C—to a subarctic climate ing cross-validation of the results. This method has in the northeast with cool summers and severe dry a secondary utility in monitoring the growth of winters (Dwc) (Kottek et al. 2006). Mountain ranges irrigation agriculture in water-limited areas as well such as the Altai in the west and the Greater Hingaan as monitoring grassland degradation from increased Mountains in the east isolate the plateau in part from grazing pressure.