Abstract
The response of compensatory growth is an important adaptive strategy for plants to grazing. However, most previous studies on compensatory growth of plants focused on the compensation of the biomass or the number of sexual reproductive offspring and neglected the compensatory growth of vegetative reproduction (VR). This is important not only for plant compensatory growth studies, but also for theoretical and practical studies of grassland production. The clonal tussock grass Hordeum brevisubulatum was selected as the research object. Four different clipping severities (unclipping and clipping stubble at heights of 15, 10, and 5 cm) at the jointing stage and flowering stage were implemented to study the effect of simulated grazing. To explore the effect of recovery growth time on plant growth after simulated grazing, three sampling times were used at different recovery times after simulated grazing (1, 3, and 7 weeks). We found that light and moderate grazing severity significantly increased the number of vegetative reproduction modules, the promotion of simulated grazing on the number of vegetative reproduction modules was higher in the jointing stage than the flowering stage, and the increase in simulated grazing severity decreased with prolonged recovery growth time. The number of tillers significantly decreased with the increase in simulated grazing in both the jointing and flowering stages at 1 week after damage, and the decreasing effect weakened with the prolonged recovery growth time. The bud number mainly showed over-compensation, the juvenile tiller number showed complete compensation, and the tiller number showed under-compensation at 1 and 3 weeks after recovery growth. The number of tillers showed complete compensation under different grazing severities in the jointing stage, while it showed under-compensation in the flowering stage at 7 weeks after recovery growth. Our results indicated that different grazing severities in the jointing stage could promote the output of tillers with matter production capacity from vegetative reproduction modules, as well as improve the capability of compensatory growth. Therefore, in plant production, there will be a sustainable development effect on the renewal and productivity of the H. brevisubulatum population, resulting in different grazing severities in the jointing stage.
Highlights
Plant organs are often damaged by grazing in grassland ecosystems at different stages of plant growth
In examining the differences between different stages at the same grazing severity, it was found that the number of buds at the jointing stage under different severities at 1 week after recovery growth (Figure 1A1) and under light and heavy severities at 7 weeks after recovery growth (Figure 1A3), the number of juvenile tillers under medium severity at 3 weeks after recovery growth (Figure 1B2) and different severities 7 weeks after recovery growth (Figure 1B3), and the number of tillers under light and medium severities at 7 weeks after recovery growth (Figure 1C3) were greater than those at the flowering stage. These results indicated that simulated grazing by herbivores at different stages of growth first promoted the vegetative reproduction (VR) of H. brevisubulatum tufts and produced more buds, and this effect at the jointing stage was greater than that at the flowering stage
Bud produced by VR will grow further and yield juvenile tiller and tiller in the growing season (Fidelis et al, 2014; Chen et al, 2016)
Summary
Plant organs are often damaged by grazing in grassland ecosystems at different stages of plant growth. Compensatory growth is defined as the ability of plants to offset the adverse effects of tissue damage, restore organic functionality, and maintain normal growth after grazing (McNaughton, 1983). Previous studies on compensatory growth have mainly focused on biomass (Erbilgin et al, 2014; Scholes et al, 2016; Wan et al, 2016), while the compensatory growth of countable traits only focused on the number of sexually propagated offspring (Levine and Paige, 2004; Mundim et al, 2012). Little attention has been paid to the compensation of the number of vegetatively propagated offspring in previous studies on plant compensatory growth. For perennial grasses, the importance of vegetative reproduction (VR) has been neglected
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