Abstract. Leymus chinensis (Trin.) Tzvelev grassland is the most widely distributed native steppe vegetation type suitable for haymaking in the semiarid pastoral regions of north-east Asia. The long-term effects of four mowing regimes (mowing once a year, twice a year, once every 2 years and twice every 3 years), and climatic variability on the hay production from L. chinensis grassland were investigated using permanent plots over 27 years. The results showed that (i) the overall cumulative annual herbage production over the 27 years was the highest under 'mowing once a year', and 'mowing twice a year' did not produce any significant change in the amount of harvested herbage; (ii) mowing induced a reduction in herbage production mostly in the first couple of years, and the reduction was larger under frequent than less frequent mowing. The annual herbage production in harvest years was higher under less frequent mowing (once every 2 years, or twice every 3 years) than that under annual mowing, but the higher herbage production in harvest years under less frequent mowing could not compensate for the herbage not made into hay in the years without harvest; (iii) annual herbage production generally increased with annual precipitation, but the response of annual herbage production to precipitation was best described by quadratic (instead of linear or logarithmic) equations, which suggested a decline in annual herbage production under the highest annual precipitation in the region, and the relationships stood under different mowing regimes; and (iv) an analysis of hay yield and quality, and costs of the mowing operation, showed that the haymaking from L. chinensis grassland was financially viable as long as the herbage production was not extremely low under drought. It is concluded that the best practice for haymaking from L. chinensis grassland should be based on the rule of 'mowing once a year' in high-production years and grazing in low-production years; and a light grazing early in the season may increase hay quality mowed in the autumn if the grassland grows well early in the season in high-production years.

Context Previous studies demonstrate that mowing inhibits tall species but facilitates short species and C 4 species. However, as each species has a growth-form and simultaneously a C-pathway, it is important to know whether the effects of mowing on a species is determined only or majorly by its growth-from or C-pathway. Objective We test the hypothesis that mowing facilitates the growth of short species and of C 4 species, and disentangle the interactive effects of plant growth-forms and C-pathways on plant responses to mowing. Methods We monitored plant production species by species in the grassland under mowing versus intact natural conditions over 30 years. We clustered all species into six plant growth-form groups and two C-pathways, and examined their dynamics. Results Mowing significantly (P \ 0.05) increased short bunchgrasses (SG) and annual and biannual (AB) species and decreased tall grasses; mowing also significantly increased C 4 species (P \ 0.01).However, as the C 4 species in the grassland are majorly SG and AB, and the mowing enhancement on C 4 SG and AB are respectively not greater than that on C 3 SG and AB, the C 4 -pathway does not show a growth advantage under mowing, which suggests other plant traits such as phenology my also play an important role in plant response to mowing. Conclusions Plant growth-forms instead of C-pathways play a dominant role in determining plant response to mowing disturbance in the grassland dominated by C 3 -species. Our results provide new insights into the mechanisms of grassland succession, and have implications for management of the Inner Mongolia grassland.

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Effects of mowing on the composition and diversity of grasslands varied with climate change (e.g., precipitation and temperature). However, the interactive effects of long-term mowing and climate change on the diversity and stability of leguminous and non-leguminous species in the semi-arid grasslands are largely unknown. Here, we used in situ monitoring data from 1982 to 2011 to examine the effects of continuous mowing and climate change on the plant biomass and diversity of leguminous and non-leguminous species, and soil total nitrogen in the typical semi-arid grasslands of northern China. Results showed that the biomass and diversity of leguminous species significantly decreased with the increasing in the biomass and diversity of non-leguminous species during the 30-a period. Variations in biomass were mainly affected by the long-term mowing, while variations in diversity were mainly explained by the climate change. Moreover, the normalized change rates of diversity in leguminous species were significantly higher than those in non-leguminous species. Mowing and temperature together contributed to the diversity changes of leguminous species, with mowing accounting for 50.0% and temperature 28.0%. Temporal stability of leguminous species was substantially lower than that of non-leguminous species. Consequently, soil total nitrogen decreased in the 2000s compared with the 1980s. These findings demonstrated that leguminous species were more sensitive to the long-term mowing and climate change than non-leguminous species in the semi-arid grasslands. Thus, reseeding appropriate leguminous plants when mowing in the semi-arid grasslands may be a better strategy to improve nitrogen levels of grassland ecosystems and maintain ecosystem biodiversity.