Therefore, the number of juvenile tillers and tillers also indicates the renewal capacity of VR. Studies have shown that grazing clouds promote the sprouting of bud for clonal plants and improve the VR capacity Dalgleish et al. The number of buds for one tuft increased to different degrees during different recovery growth periods, and the increase at the jointing stage was generally higher than that at the flowering stage.
The results indicated that the renewal capacity of VR was higher at the jointing stage than at the flowering stage. Previous studies have shown that the renewal capacity of VR was related to the grazing tolerance of clonal plants Huhat et al.
The difference in the grazing tolerance of the H. Research has shown that the responses of plants to grazing are different at different growing stages due to differences in structure, storage capacity, and physiological regulation Boege, ; Boege and Marquis, ; Hanley and Fegan, The tufts of the H.
The growth of functional leaves was vigorous, and the physiological response to foraging apical tissue was relatively sensitive. Plants can produce and accumulate photosynthetic products during growth. Therefore, the numbers of tillers under different severities completely returned to the control levels at 7 weeks of recovery growth. However, most stored nutrients are used for sexual reproduction in the upper part of the tiller at the flowering stage, and the functional leaves in the bottom part of the tiller begin to senesce Zhang et al.
Then, the regulatory function of the physiological response to foraging apical tissue is weakened. Therefore, the numbers of tillers under different severities did not return to the control levels at 7 weeks of recovery growth.
In summary, the VR capacity of the H. For local grassland management practices, regardless of whether the grazing severity is light or heavy, there will be no harmful effect of grazing at the jointing stage on population regeneration and the production of H.
The population of clonal grass consists of bud, juvenile tiller without tillering node, vegetative tiller with tillering node, and reproductive tiller with fruit at different stages of life history for VR Yang and Zhu, In different habitats or disturbed conditions at different stages during the growing season, the transformation from bud to juvenile tiller and from juvenile tiller to tiller could change the life history pattern of VR modules of clonal grasses Ott and Hartnett, a.
Considering the composition of different VR modules, the bud is the basic module for supplementation and potential population renewal. The juvenile tiller and tiller are basic modules of the population and the main modules of population matter production, and the capacity for matter production of juvenile tillers increases with the growth of the module Yang and Zhu, The output law of tiller from bud after grazing is one of the most important mechanisms conferring plant resilience to herbivory and is conducive to recovery after grazing for damaged populations Tiffin, The life history pattern of module composition of herbaceous populations is the basis for evaluating population dynamics and matter production Li et al.
In our study, the highest ratio of VR module was tiller under the control treatment, while the ratio of bud was the highest under simulated grazing treatment. The results indicated that the main function of the clonal population is the production of tillers when there is no interference from herbivores. However, the main function of the clonal population is to produce more buds to ensure the potential vegetative reproduction of the population, which is important for the resistance to the interference of herbivores and the productivity recovery after the interference Dalgleish and Hartnett, ; Chen et al.
The change in life history pattern of vegetative propagation components after simulated grazing disturbance indicates the change in the strategies of vegetative reproduction. The tiller is the main VR module of the population with matter production Yang and Zhu, The ratio of tillers under different grazing severities at the jointing stage at 7 weeks of growth recovery was consistent with that under the control treatment.
The results indicated that the population dynamics under grazing treatments were similar to those under the control treatment, and the capacity for matter production was completely restored. However, the capacity for matter production was not fully restored at the flowering stage. Therefore, the recovery capacity of the H. According to the physiological principle of plant nutrient supply for apical dominance, apical dominance would be broken when the top of the plants is grazed by herbivores, promoting resprouting after damage and improving the vegetative propagation of clonal plants Thomson et al.
The compensatory growth of plants first occurs after grazing Zhao et al. However, due to the senescence and death of plant leaves, the continuous growth and production of VR modules are the basis for plants to achieve compensatory growth in matter production Yuan et al.
The maintenance of belowground bud banks in grassland ecosystems enables plants to survive adverse environments, such as grazing disturbance and drought Dalgleish and Hartnett, ; VanderWeide and Hartnett, Therefore, the promotion of bud sprouting after grazing is important for plant compensatory growth, and the output of tiller with multi-leaves from the bud finally promotes the compensatory growth of plants Chen et al.
Therefore, the VR of the population and the turnover rate of modules after grazing disturbances, especially the turnover rate of tiller from bud, were considered the major internal mechanisms of plant compensatory growth Strauss and Agrawal, ; Tiffin, In our study, the increase in bud number and the decrease in tiller number in the H. Compared with that at 1 week after recovery growth, the number of tillers at 7 weeks after recovery growth under the control treatment at the jointing and flowering stages increased by 0.
However, the number of tillers under light severity, medium severity, and heavy severity increased by 4. These results indicate that different grazing severities and initial grazing times promoted the transformation of bud to tiller. The transformation of buds to tillers increased with increased grazing severity, and the number of buds transformed to tillers was higher at the jointing stage.
Therefore, the number of tillers under different grazing severities at the jointing stage at 7 weeks after recovery growth was similar to that under the control treatment, which showed complete compensation.
However, the number of tillers showed undercompensation at the flowering stage. In summary, the mechanism of compensatory vegetative propagation of plants is that grazing provoked vegetative regeneration or resprouting after damage and promoted a significant increase in the number of bud banks and the transformation among VR modules, especially promoting the turnover process of bud to tiller.
Compensatory growth is a positive response of plants to damage and is generally measured by the traits related to fitness. In fact, changes in biomass and the number of plant organs indicate the compensatory growth capacity Mundim et al. In our study, the numbers of buds, juvenile tillers and tillers produced by VR were used to calculate the CI.
According to the difference in the CI among different grazing severities and different grazing periods and the change in the CI at different recovery growth times, the CI can comprehensively effectively indicate compensatory VR under different simulated grazing treatments and provide scientific guidance for grassland management.
We can determine a plan for rotational grazing and provide practical scientific guidance for grassland grazing management. CIs of buds under different severities at the jointing stage were higher than those at the flowering stage. The results indicated that the compensatory growth of VR and recovery capacities of the H.
The number of tillers mainly showed undercompensation, while showed complete compensation at the jointing stage at 7 weeks. The results indicated that different grazing severities at both growing stages had adverse effects on the matter production of the H.
The adverse effects at the jointing stage were completely eliminated at 7 weeks after recovery growth with the prolongation of recovery growth time, and the biomass production showed complete compensation or overcompensation unpublished data. However, the adverse effects at the flowering stage continued. Therefore, the grazing rotation of grassland when the productivity was completely restored was 50 days at the jointing stage and longer at the flowering stage. The duration for which the adverse effects of different grazing severities at the flowering stage would be eliminated and whether they could be eliminated in this growing season need further study.
In this study, the clonal tussock grass Hordeum brevisubulatum was selected to study the effect of simulated grazing. Four clipping severities at the jointing and flowering stages were implemented, and three sampling times were used at different recovery durations. We found that simulated grazing increased the number of buds.
The promotion was greater in the jointing stage than the flowering stage, and the increase decreased with prolonged recovery growth time. The number of tillers significantly decreased, and the decreasing effect weakened with prolonged recovery growth time.
The tiller number showed undercompensation at 1 and 3 weeks after recovery growth, while it showed complete compensation at the jointing stage and undercompensation at the flowering stage at 7 weeks after recovery growth. Our results suggest that different simulated grazing severities at the jointing stage could increase the output of tiller from bud and improve the compensatory growth capacity.
The datasets generated for this study are available on request to the corresponding author. YY and JY designed the experiments. JY performed the experiments. JY and HL analyzed the data and wrote the manuscript. All authors read and approved the manuscript.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Anderson, M. Defoliation effects on reproductive biomass: importance of scale and timing. Range Manag. Belsky, A. Does herbivory benefit plants? A review of the evidence. Benson, E. The role of seed and vegetative reproduction in plant recruitment and demography in tallgrass prairie.
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Facing herbivory as you grow up: the ontogeny of resistance in plants. Trends Ecol. Busso, C. Effects of drought and defoliation on bud viability in two caespitose grasses. Chen, X. Consequences of repeated defoliation on belowground bud banks of Carex brevicuspis Cyperaceae in the Dongting Lake wetlands, China. Front Plant Sci. Coffin, D. Spatial and temporal variation in the seed bank of a semiarid grassland. Da Silveira Pontes, L. The role of plant traits and their plasticity in the response of pasture grasses to nutrients and cutting frequency.
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Hanley, M. Concepts of source and sink strength were implemented and used to simulate tiller production. Go directly to: Content Search box Breadcrumb. Sub-project 2: tiller production in relation to carbon acquisition and distribution When wheat plants do shade each other, leaf photosynthesis rate is reduced, and less assimilates are available for growth and development of the plant, compared to unshaded conditions.
This Postdoc project started in December and ended in April Twitter Whatsapp Linkedin Email. The life of an individual shoot is usually not more than one year, and frequently less. Tillers formed in the fall are important to winter survival of the stand and spring regrowth, but may die during summer. Tillers formed in the spring may be important for summer survival.
Those tillers initiating inflorescences in spring usually die before the end of summer. A young tiller depends on the parent shoot for photo-assimilates until it has developed several leaves and an adequate root system. Although a mature tiller may appear to function as an independent entity, some relationship apparently exists between tillers interconnected by a common vascular system. Thus, a grass plant appears to be a highly organized system rather than a collection of competing tillers.
Tillers produce many additional roots. Therefore, grazing should be deferred in the spring until such time as they can tolerate limited defoliation. For example, midwestern and southern wheat farmers commonly graze early growth of wheat during the tillering phase of development. However, when the shoots start to produce a central stem early-jointing or transition stage they cease grazing because of the possible destruction of the growing point which contains the rudimentary seed head.
Similarly, in western Oregon, sheep are commonly put on grass seed fields to graze but are removed before culm elongation. But, there is an additional threat at this growth stage. Livestock might defoliate a shoot in a manner which saves the growing point but may cause one or more leaf blades to be defoliated below the collar zone.
When this occurs, the recovery growth consists of a flowering stem with the seed head in tact, but with severly reduced leaf blade area. Leaves are the site of photosynthesis, so livestock should not graze so long that plants are denuded.
The above response to early grazing is commonly seen with rotational grazing where several paddocks are grazed sequentially. The first paddock is frequently grazed for too long resulting in recovery growth comprised chiefly of skeletonized flowering stem a naked culm with a seed head but no leaf blades.
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