Abstract
Defoliation is widely used for grassland management. Our understanding of how grass species adjust their regrowth and regain balance after defoliation remains limited. In the present study, we examined the regrowth processes of two dominant species after defoliation in grasslands in Inner Mongolia. Our results showed that the aboveground biomass and total biomass of both species significantly decreased and did not completely recover to the control level after 30 days of regrowth. The leaf mass ratio of Leymus chinensis reached the control level at 15 days, but that of Stipa grandis did not recover to the control level. The root mass ratio of these species reached the same levels as that of the control plants within 10 days after defoliation. As indicated by the dynamics of water-soluble carbohydrates (WSCs), protein, and biomass-based shoot: root ratios, both species regained balances of WSCs and protein between above- and below-ground organs at day 10 after defoliation; however, the biomass regained balance 15 days after defoliation. We deduced that the biomass-based shoot:root ratio was regulated by the WSCs and protein concentrations. In conclusion, following defoliation, both grass species first restore their nutrient-based balance between above- and below-ground parts and then regain biomass balance.
Highlights
Defoliation caused by animal grazing and hay production has profound impacts on plant growth and development in grassland ecosystems
Defoliation significantly decreased the height of L. chinensis and S. grandis during the 30 days of regrowth (Table 1)
No significant effects of defoliation on the number of tillers per plant were observed in either species, but the number of tillers increased in L. chinensis regardless of defoliation treatment
Summary
Defoliation caused by animal grazing and hay production has profound impacts on plant growth and development in grassland ecosystems. Defoliation decreases the total leaf area, plant photosynthesis, and uptake and assimilation of nutrients, such as carbon and nitrogen, but increases the mobilization of reserved nutrients to develop new leaves and stems (Macduff and Jackson, 1992; Volenec et al, 1996). The ability of plants, which use internal stores of carbon and nitrogen, both to rapidly restore photosynthetically active leaf area and to meet the maintenance demands of other organs, is among the key factors that facilitate plant survival during the first 2 weeks of regrowth after defoliation (Volenec et al, 1996). Numerous studies have highlighted the importance of water-soluble carbohydrate (WSC) reserves of grass species during regrowth following defoliation (Hume, 1991; Donaghy and Fulkerson, 1997). WSCs in the stem stubble (residual stem after defoliation)
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