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Research Advances in responses of Semi-arid Grassland to nitrogen and water

A series controlled Field experiments were set in 2005 in Doren Restoration Ecology Experiment Station by Botany Institute, CAS. The station is located in a cultivation land and grassland ecotone in Inner-Mongolia Autonomic Region. Various dosages of Nitrogen and/or phosphorus fertilizers were added and waters were drip irrigated to protected Natural Grassland and grassland restored abandoned cultivated land. The aim was to see the responses of the grassland community composition, species turnover, ecosystem stability, bio-diversity, soil nutrient availability and the efficiency of plant in using the nutrients…

Since 2009, the experiment work was transferred to Our institute. The Soil Chemistry Research Group took the responsibility since 2012. Thirteen papers have been published since then. The main results were as follows.

1 Simulated atmospheric nitrogen deposition and precipitation increased the community stability of the semiarid grassland (Oecologia 2014).

2 Environmental changes drive the stability of semiarid grassland via changing the asynchronous responses of plant species. Increase in precipitation

enhanced species diversity and community stability, but increase in nitrogen precipitation reduced the diversity and stability. Contradictory to the prediction, species diversity is not the driving force to the semiarid grassland stability. The stability of dominant species affects the community stability. The increase in precipitation in the future may offset the negative effect of nitrogen precipitation on the species diversity and community stability.(Journal of Ecology, 2015).

When nitrogen deposition increased, the successions of natural grassland and abandoned cultivated land were differentiated. When precipitation increased in the vegetative season made the succession of the two land type went in a convergent way. (Plant and Soil, 2015)

3 Simulated nitrogen deposition and precipitation significantly affect soil carbon, nitrogen content and soil enzyme activities: nitrogen deposition reduced soil organic carbon content, while increased precipitation increased the organic carbon. Nitrogen deposition reduced soil pH, activities of dehydrogenase and alkaline phosphatase. However, Increased precipitation increased soil pH and enhanced the enzyme activities. (Plant and Soil, 2014).

4 Simulated nitrogen deposition and increased precipitation changed the composition of grassland soil aggregates and dynamics of soil carbon and nitrogen: increase in precipitation increased aggregate sides. Nitrogen deposition and increased precipitation jointly increased total soil nitrogen. Increased precipitation alone reduced 13C value. The increased precipitation is more beneficial to the improvement of soil structure (Soil Science Society of American Journal, 2015).

5 Nitrogen and water adding affect enzyme activities in soil aggregate: Micro- aggregate had higher activities in β-glycosidase and acid phosphatase. Big aggregate had maximum activity of N - acetyl - amino glycosidase. The activities in β-glycosidase and acid phosphatase were inhibited by nitrogen deposition, but the activity of N - acetyl - amino glycosidase was enhanced by added nitrogen. This indicated that nitrogen input is conducive to fungi via reduced pH but not to bacteria (Soil Biology & Biochemistry, 2015).

6 Recent publications

  [1] Xu ZW*, Ren HY, Cai JP, Wang RZ, Li MH, Han XG*, Lewis BJ, Jiang Y*. 2014. Effects of experimentally enhanced precipitation and nitrogen on resistance, recovery and resilience of plant cover in a semi-arid grassland following a natural drought. Oecologia, 176: 1187-1197. Doi: 10.1007/s00442-014-3081-9.

  [2] Xu ZW?, Ren HY?, Li MH, van Ruijven J, Han XG, Wan SQ, Li H, Yu Q, Jiang Y*, Jiang L*. 2015. Environmental changes drive the temporal stability of semi-arid natural grasslands through altering species asynchrony. Journal of Ecology, Doi: 10.1111/1365-2745.12441.

  [3] Xu ZW?, Ren HY?, Cai JP, Wang RZ, He P, Li MH, Lewis BJ, Han XG, Jiang Y*. 2015. Antithetical effects of nitrogen and water availability on community similarity of semiarid grasslands: Evidence from a nine-year manipulation experiment. Plant and Soil, Doi: 10.1007/s11104-015-2634-y.

  [4] Wang RZ, Filley TR, Xu ZW, Wang X, Li MH, Zhang YG, Luo WT, Jiang Y*. 2014. Coupled response of soil carbon and nitrogen pools and enzyme activities to nitrogen and water addition in a semiarid grassland of Inner Mongolia. Plant and Soil, 381(1): 323-336. Doi : 10.1007/s11104-014-2129-2.

  [5] Wang RZ, Dungait JAJ, Creamer CA, Cai JP, Li B, Xu ZW, Zhang YG, Ma YN, Jiang Y*. 2015. Carbon and nitrogen dynamics in soil aggregates under long-term N and water addition in a temperate steppe. Soil Science Society of America Journal, 79: 527-535 Doi:10.2136/sssaj2014.05.0201.

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