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Purpose: Climate models predict shifts in precipitation patterns characterized by increased precipitation amount and decreased frequency for semi-arid grasslands in northeast China. However, under these novel climatic conditions, potential differences in plant biomass and its allocation among different degraded grasslands remain unclear. Methods: We conducted a mesocosm experiment to test the effects of higher precipitation amount (increased by 50% from the long-term mean) and lower frequency (decreased by 50%) on plant biomass and allocation in the lightly, moderately, and severely degraded grasslands. Results: Lower precipitation frequency promoted belowground biomass but reduced aboveground biomass through enhancing soil water variability. Higher precipitation amount enhanced aboveground biomass in the lightly and moderately degraded grasslands, but not in the severely degraded grassland due to lower soil nitrogen availability. Lower precipitation frequency weakened or ended the positive effects of higher precipitation amount on aboveground and belowground biomass, and higher precipitation amount suppressed the enhancement of lower precipitation frequency on belowground biomass, which could be attributed to temporary waterlogging. Plants in the moderately degraded grassland preferred to adjust root vertical distribution, which was impacted by the changes in plant community composition. However, adjustment of aboveground biomass vs. belowground biomass was the primary biomass allocation strategy in the other two grasslands. Conclusions: Our findings emphasized the importance of considering the degradation level of grasslands when predicting responses of ecosystem functions to the projected changes in precipitation regimes. These findings are critical for making feasible decisions for the sustainable management of degraded grasslands. Legend: + and − indicate positive and negative relationships, respectively LDG, MDG and SDG-lightly degraded, moderately degraded and severely degraded grasslands, respectively DPF-decreased precipitation frequency treatment, IPA-increased precipitation amount treatment SWC and CVSWC-mean and variation of soil water content, respectively SINC-soil inorganic nitrogen content AGB and BGB-aboveground and belowground biomass, respectively fAGB-AGB / total biomass BGB0–10 (%)-belowground biomass proportion in the 0–10 cm soil layer, BGB 0 - 10 / BGB 0 - 30 × 100 RAGB-relative aboveground biomass [ABSTRACT FROM AUTHOR]

Aims: Terrestrial plants require relative stable stoichiometry of elements for their growth. The effects of plant species and soil phosphorus (P) concentration on P:nutrient stoichiometry in plant remains still unknown. Methods: Soil and plant samples were collected from 88 sites in a P-rich area of a subtropical portion of China to examine the linkage of soil P concentration with the concentrations and stoichiometry of 12 nutrient elements (C, N, P, S, K, Ca, Mg, Fe, Al, Zn, Mn and Na) for different plant species. Results: Soil rich in P increased the concentrations of S, P, K, Ca, Fe, Mg, Mn, Al, and Na in the plants, but induced a strong antagonism to Zn. Meanwhile, the concentrations of C and N in the leaf was restrained when the plants grew in soil under high P concentration. Clustering analysis showed that plant species were categorized according to soil P concentration into P > 2 mg g−1 and P < 2 mg g−1 groups. However, insignificant dissimilarity among plant species was noticed. Conclusions: The stoichiometry of P:nutrient in the plant organs was strongly affected by soil P concentrations and this could reflect soil nutrient status over plant species. Therefore, the difference in soil P concentration is a major driver triggering the variation in elemental stoichiometry. [ABSTRACT FROM AUTHOR]