[1] Archer S, Schimel DS, Holland EA. Mechanisms of shrubland expansion: Land use, climate or CO2. Climatic Change, 1995, 29: 91-99 [2] House JI, Archer S, Breshears DD, et al. Conundrums in mixed woody-herbaceous plant systems. Journal of Biogeography, 2010, 30: 1763-1777 [3] Wu XB. Observation: Long-term increases in mesquite canopy cover in a North Texas savanna. Journal of Range Management, 2001, 54: 171-176 [4] Van Auken OW. Shrub invasions of North American semiarid grasslands. Annual Review of Ecology & Systema-tics, 2000, 31: 197-215 [5] D’Odorico P, Okin GS, Bestelmeyer BT. A synthetic review of feedbacks and drivers of shrub encroachment in arid grasslands. Ecohydrology, 2012, 5: 520-530 [6] Ni J. Carbon storage in grasslands of China. Journal of Arid Environments, 2002, 50: 205-218 [7] Tang X, Zhao X, Bai Y, et al. Carbon pools in China’s terrestrial ecosystems: New estimates based on an intensive field survey. Proceedings of the National Academy of Sciences of the United States of America, 2018, 115: 4021-4026 [8] Petrie MD, Collins SL, Swann AM, et al. Grassland to shrubland state transitions enhance carbon sequestration in the northern Chihuahuan Desert. Global Change Biology, 2015, 21: 1226-1235 [9] Heras MDL, Turnbull L, Wainwright J. Seed-bank structure and plant-recruitment conditions regulate the dynamics of a grassland-shrubland Chihuahuan ecotone. Ecology, 2016, 97: 2303-2318 [10] King AW, Dilling L, Zimmerman GP, et al. The first state of the carbon cycle report (SOCCR): The North American carbon budget and implications for the global carbon cycle. Climate Change Science Program, 2007: 126-147 [11] Van Auken OW, Bush JK. Invasion of Woody Legumes. Vision 4. New York: Springer, 2013 [12] Throop HL, Lajtha K, Kramer M. Density fractionation and 13C reveal changes in soil carbon following woody encroachment in a desert ecosystem. Biogeochemistry, 2013, 112: 409-422 [13] Mckinley DC, Blair JM. Woody plant encroachment by Juniperus virginiana in a mesic native grassland promotes rapid carbon and nitrogen accrual. Ecosystems, 2008, 11: 454-468 [14] Hagos MG, Smit GN. Soil enrichment by Acacia melli-fera subsp. detinens on nutrient poor sandy soil in a semi-arid southern African savanna. Journal of Arid Environments, 2005, 61: 47-59 [15] Li H, Shen HH, Chen LY, et al. Effects of shrub encroachment on soil organic carbon in global grasslands. Scientific Reports, 2016, 6: 28974 [16] Jackson RB, Banner JL, Jobbágy EG, et al. Ecosystem carbon loss with woody plant invasion of grasslands. Nature, 2002, 418: 623-626 [17] Qiu LP, Wei XR, Zhang XC, et al. Soil organic carbon losses due to land use change in a semiarid grassland. Plant and Soil, 2012, 355: 299-309 [18] Coetsee C, Gray EF, Wakeling J, et al. Low gains in ecosystem carbon with woody plant encroachment in a South African savanna. Journal of Tropical Ecology, 2013, 29: 49-60 [19] Belay L, Kebede F. The impact of woody plants encroachment on soil organic carbon and total nitrogen stocks in Yabello District, Borana Zone, Southern Ethio-pia. Journal of the Drylands, 2010, 3: 234-240 [20] Lett MS, Knapp AK, Briggs JM, et al. Influence of shrub encroachment on aboveground net primary productivity and carbon and nitrogen pools in a mesic grassland. Canadian Journal of Botany, 2004, 82: 1363-1370 [21] Torn MS, Trumbore SE, Chadwick OA, et al. Mineral control of soil organic carbon storage and turnover. Nature, 1997, 389: 170-173 [22] Barger NN, Archer SR, Campbell JL, et al. Woody plant proliferation in North American drylands: A synthesis of impacts on ecosystem carbon balance. Journal of Geophysical Research Biogeosciences, 2015, 116: 165-176 [23] Zhang Z-H (张志华), Li X-Y (李小雁), Jiang Z-Y (蒋志云), et al. Relationship between shrub encroachment and soil properties in the typical steppe of Inner Mongolia. Acta Prataculturae Sinica (草业学报), 2017, 26(2): 224-230 (in Chinese) [24] Zhang P-J (张璞进), Qing H (清 华), Zhang L (张 雷), et al. Population structure and spatial pattern of Caragana tibetica communities in Nei Mongol shrub-encroached grassland. China Journal of Plant Ecology (植物生态学报), 2017, 41(2): 165-174 (in Chinese) [25] Xiong X-G (熊小刚), Han X-G (韩兴国). Spatial heterogeneity in soil carbon and nitrogen resources,caused by Caragana microphylla, in the thicketization of semiarid grassland, Inner Mongolia. Acta Ecologica Sinica (生态学报), 2005, 25(7): 1678-1683 (in Chinese) [26] Zhao Y-N (赵亚楠), Zhou Y-R (周玉蓉), Wang H-M (王红梅). Spatial heterogeneities of soil water conment under anthropogenic introduced shrub (Caragana korshinskii) encroachment in desert grassland of the Eastern Ningxia Area, China. Chinese Journal of Applied Ecology (应用生态学报), 2018, 29(11): 3577-3586 (in Chinese) [27] Bao S-D (鲍士旦). Soil and Agro-Chemistrical Analysis. 3rd Ed. Beijing: China Agriculture Press, 1999: 30 (in Chinese) [28] Porporato A, D’Odorico P, Laio F, et al. Ecohydrology of water-controlled ecosystems. Advances in Water Resources, 2002, 25: 1335-1348 [29] Cho E, Choi M. Regional scale spatio-temporal variability of soil moisture and its relationship with meteorological factors over the Korean peninsula. Journal of Hydrology, 2014, 516: 317-329 [30] Fang KK, Li HK, Wang ZK, et al. Comparative analysis on spatial variability of soil moisture under different land use types in orchard. Scientia Horticulturae, 2016, 207: 65-72 [31] Wang Z-Q (王政权). Geostatistics and Application in Ecology. Beijing: Science Press, 1999: 96-100 (in Chinese) [32] Eldridge DJ, Maestre FT, Maltez-Mouro S, et al. A global database of shrub encroachment effects on ecosystem structure and functioning. Ecology, 2012, 93: 2499 [33] Davidson EA, Trumbore SE, Amundson R. Soil warming and organic carbon content. Nature, 2000, 408: 789-790 [34] Yang Y (杨 阳), Liu B-R (刘秉儒), Song N-P (宋乃平), et al. The effect of planted caragana density on the spatial distribution of soil nutrients in desert steppe. Acta Prataculturae Sinica (草业学报), 2014, 23(5): 107-115 (in Chinese) [35] Song XZ, Peng CH, Zhou GM, et al. Chinese Grain for Green Program led to highly increased soil organic carbon levels: A meta-analysis. Scientific Reports, 2014, 4: 4460 [36] Lu F, Hu H, Sun W, et al. Effects of national ecological restoration projects on carbon sequestration in China from 2001 to 2010. Proceedings of the National Academy of Sciences of the United States of America, 2018, 115: 4039-4044 [37] Yang YH, Luo YQ, Finzi AC. Carbon and nitrogen dynamics during forest stand development: A global synthesis. New Phytologist, 2011, 190: 977-989 [38] Hassink J. The capacity of soils to preserve organic C and N by their association with clay and silt particles. Plant and Soil, 1997, 191: 77-87 [39] Xiong X-G (熊小刚), Han X-G (韩兴国). Dynamics of the small-scale heterogeneity of the soil carbon and nitrogen resources associated with Caragana microphylla in Inner Mongolia degraded steppe. Acta Ecologica Sinica (生态学报), 2006, 26(2): 483-488 (in Chinese) [40] Wang T, Kang FF, Han HR, et al. Spatial variability of organic carbon and total nitrogen in the soils of a subalpine forested catchment at Mt. Taiyue, China. Catena, 2016, 155: 41-52 |