Impact of grazing intensities on reproduction patterns of elm trees (Ulmus pumila) in degraded sandy lands in China

Abstract

The effect of grazing on patterns of reproduction in trees has been little reported. We explored the effects of grazing intensities on reproductive growth, allocation patterns, and duration in elm trees (Ulmus pumila L.) at the Horqin Sandy Land, a degraded area in northern China. Current-year shoots were selected from branches and harvested from individual elm trees subjected to one of four grazing intensities (heavy, moderate, light, and no grazing). Shoots, flower buds, flowers, seeds, leaf buds, and leaves were collected, dried, and weighed. Results showed that the biomass in heavy, moderate and light grazing treatments is significantly higher than in no grazing treatment (P < 0.05). The reproductive allocation of U. pumila in heavy grazing treatment was significantly higher from that in the no grazing treatment (P < 0.05). Additionally, we found that reproduction of U. pumila ended later in grazed plots, suggesting the duration of reproduction is extended with grazing disturbance. Our findings suggest that U. pumila may prolong it s duration of reproduction and alter its reproductive biomass in response to grazing. It is not clear whether these effects are related to damage to U. pumila trees by grazers or whether they are due to grazers affecting soil properties or plant competitors around U. pumila trees. . 2003. Impacts of human disturbance on elms-motte-veldt in hunshangak sandland. Acta Phytoecologica Sinica 27:829-834. Choler P, Du G. 2012. Relationship between reproductive allocation and relative abundance among 32 species of a Tibetan Alpine Meadow: effects of fertilization and grazing. PLOS ONE 7(4):e35448. Perez-Llorca M, Vilas JS. 2019. Sexual dimorphism in response to herbivory and competition in the dioecious herb Spinacia oleracea. Plant Ecology 220:57-68 DOI 10.1007/s11258-018-0902-7. R Core Team. 2015. R: a language and environment for statistical computing. Vienna: R Foundation for Statistical Computing. Ren H, Zheng S, Bai Y. 2009. Effects of grazing on foliage biomass allocation of grass land communities in Xilin river basin, Inner Mongolia. . 2005. Structure, pattern and mechanisms of formation of seed banks in sand dune systems in northeastern Inner Mongolia, China. Plant and Soil 277:175-184 DOI 10.1007/s11104-005-6836-6. Zhang M, Wu J, Tang Y. 2016. The effects of grazing on the spatial pattern of elm (Ulmus pumila L.) in the sparse woodland steppe of Horqin Sandy Land in northeastern China. Solid Earth 7:631-637

The influence of tree management practices on phenological growth stages of Ulmus pumila L. (Siberian elm)

“…The reproductive growth extended from February to the beginning of April, whereas the leaves developed throughout April. Tang (2020) observed that the buds of U. pumila trees in a semi‐arid region of North China (119°39′–120°02′E, 42°29′–43°06′N, 480 m a.s.l.) began to expand at the end of March, and that the seed dispersal ended mid‐May.…”

“…Chen and Xu (2012a,b) studied the extension of Siberian elm growing season as an effect of climate change in China and found that such extension was induced mainly by the advancement of start date of leaf unfolding. In North China, Tang (2020) studied the effect of grazing on the reproductive allocation of U. pumila in woodlands of a semi‐arid region and found that U. pumila trees extended the duration of the reproductive stage under grazing. To the best of our knowledge, phenology according BBCH scale and timing of Siberian elm growth stages have not been reported so far, either the effect of management practices on phenology.…”

Indirect Effects of Grazing on Wind-Dispersed Elm Seeds in Sparse Woodlands of Northern China

“…Elm trees provide various ecosystem services and play critical roles in helping to maintain the stability of the ecosystem of sparse woodland. For example, elm trees provide a seed shadow for regeneration and shade for grasses and livestock [15,16].…”

“…The seed dispersal process might be influenced by grazing in direct and indirect ways. Directly, grazing promotes more seed production compared with exclosure lands [14,15]. Indirectly, the grazing animals eat and trample vegetation.…”

“…Elm trees provide various ecosystem services and play critical roles in helping to maintain the stability of the ecosystem of sparse woodland. For example, elm trees provide a seed shadow for regeneration and shade for grasses and livestock[15,16].Sparse woodlands and elm trees, in particular, are, however, threatened by ever-increasing grazing pressure. Grazing leads to a decrease in the area of sparse woodland[14].…”