Response of soil C:N:P stoichiometry, organic carbon stock, and release to wetland grasslandification in Mu Us Desert
Wetlands in Mu Us Desert have severely been threatened by grasslandification over the past decades. Therefore, we studied the impacts of grasslandification on soil carbon (C):nitrogen (N):phosphorus (P) stoichiometry, soil organic carbon (SOC) stock, and release in wetland-grassland transitional zone in Mu Us Desert.
Materials and methods
From wetland to grassland, the transition zone was divided into five different successional stages according to plant communities and soil water conditions. At every stage, soil physical and chemical properties were determined and C:N:P ratios were calculated. SOC stock and soil respirations were also determined to assess soil carbon storage and release.
Results and discussion
After grasslandification, SOC contents of top soils (0–10 cm) decreased from 100.2 to 31.79 g kg−1 in June and from 103.7 to 32.5 g kg−1 in October; total nitrogen (TN) contents of top soils (0–10 cm) decreased from 3.65 to 1.85 g kg−1 in June and from 6.43 to 3.36 g kg−1 in October; and total phosphorus (TP) contents of top soils (0–10 cm) decreased from 179.4 to 117.4 mg kg−1 in June and from 368.6 to 227.8 mg kg−1 in October. From stages Typha angustifolia wetland (TAW) to Phalaris arundinacea L. (PAL), in the top soil (0–10 cm), C:N ratios decreased from 32.2 to 16.9 in June and from 19.0 to 11.8 in October; C:P ratios decreased from 1519.2 to 580.5 in June and from 19.0 to 11.8 in October; and N:P ratios decreased from 46.9 to 34.8 in June and changed from 34.9 to 34.0 in October. SOC stock decreased and soil respiration increased with grasslandification. The decrease of SOC, TN, and TP contents was attributed to the reduction of aboveground biomass and mineralization of SOM, and the decrease of soil C:N, C:P, and N:P ratios was mainly attributed to the faster decreasing speeds of SOC than TN and TP. The reduction of aboveground biomass and increased SOC release led by enhanced soil respiration were the main reasons of SOC stock decrease.
Grasslandification led to lowers levels of SOC, TN, TP, and soil C:N, C:P, and N:P ratios. Grasslandification also led to higher SOC loss, and increased soil respiration was the main reason. Since it is difficult to restore grassland to original wetland, efficient practices should be conducted to reduce water drainage from wetland to prevent grasslandification.
KeywordsCarbon stock and release C:N:P stoichiometry Grasslandification Nutrient status Wetland
Acknowledgements This study was financially supported by Western Light Program of CAS (XBZG2011015) and State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Foundation (A314021402-1605).
- EM Bennett (2001) Human impact on erodable phosphorus and eutrophication: a global perspective. BioScience 3Google Scholar
- Brady NC, Weil RR (2008) Nature and properties of soils, 14th edn. Prentice Hall, Upper Saddle RiverGoogle Scholar
- Li Y et al (2012) Is the C:N:P stoichiometry in soil and soil microbial biomass related to the landscape and land use in southern subtropical China? Glob Biogeochem Cycles 26Google Scholar
- Palmborg C et al (2014) Demand for K and P in reed canary grass (Phalaris arundinacea) during the harvest years. In: EGF at 50: the future of European grasslands. Proceedings of the 25th general meeting of the European grassland federation, Aberystwyth, Wales, 7–11 September 2014, pp 498–501Google Scholar
- Redfield AC (1960) The biological control of chemical factors in the environment. Sci Prog 11:150–170Google Scholar
- Zhang X, Li D, Pan G, Li L, Fan L, Xu X (2008) Conservation of wetland soil C stock and climate change of China. Adv Clim Chang Res 4:202–208Google Scholar