Effects of plateau pika disturbance levels on the plant diversity and biomass of an alpine meadow

Abstract

The plateau pika (Ochotona curzoniae) is known to influence the plant diversity and biomass of the alpine meadow, and it is regarded as a pest. The species has been subject to extensive controls without a clear target density in the Qinghai-Tibetan Plateau. We investigated the effects of different plateau pika disturbance levels on plant composition, species diversity and biomass. The density of active burrow entrances was used as an index of disturbance levels I, II, III and IV (corresponding to 8, 19, 27 and 39 active burrow entrances per 625 m 2 ). We found that the plant community composition differed with different disturbance levels. The plant replacements were mainly related to associate plants rather than dominant plants. With the increase in the plateau pika disturbance levels, the plant cover decreased, and the plant height first increased and then decreased. The plant evenness index was higher in the levels II and III disturbance conditions, while the plant diversity index and plant richness index were highest in the level IV disturbance condition. The disturbance levels had no effect on the total plant biomass; however, the intermediate disturbance levels (II and III) increased the palatable plant biomass. The total plant biomass was mainly dependent on the unpalatable plant biomass. The total plant biomass showed a positive correlation with the richness index and a negative correlation with the evenness index. The palatable plant biomass showed a positive correlation with the evenness index and a negative correlation with the richness index. These results imply that the intermediate disturbance levels are beneficial to livestock production as they increase the alpine meadow quality, and the higher disturbance level is better for plant diversity conservation in the alpine meadows of the Qinghai-Tibetan Plateau.

Changes in soil carbon and nitrogen stocks following degradation of alpine grasslands on the Qinghai‐Tibetan Plateau: A meta‐analysis

“…The increased soil BD were mainly attributed to livestock (e.g., yak and Tibetan sheep) trampling, which resulted in mechanical stress imposed on the soils and then induced the collapse of soil structure (Hiltbrunner et al, 2012; Zhou, Gan, Shangguan, & Dong, 2010). In addition, grazing or rodent activities could decrease the amount of aboveground biomass and limit the development of root system, leading to a reduction in SOM inputs (Bai et al, 2015; Pang & Guo, 2018). This was another reason for the increased soil BD because SOM is a loose and porous material that not only serves as the major component of soils (Arvidsson, 1998; Ruehlmann & Körschens, 2009), but also plays an important role in the formation of soil aggregates (Piccolo & Mbagwu, 1999).…”

“…There are multiple potential mechanisms responsible for the depletion of SOC and STN stocks after grassland degradation. First, livestock grazing and rodent activities (e.g., burrowing) could negatively impact the growth of plants, reducing both above‐ and belowground productivity of the plant community (Bai et al, 2015; Li, Dong, Wen, et al, 2014; Pang & Guo, 2018). In this case, the inputs of SOM from plants (e.g., plant residues and root exudates) would be decreased.…”

Effect of plateau pika disturbance on the ecosystem services of alpine grasslands

“…Plateau pika disturbance in relation to lower palatable plant biomass has also been reported in a previous study (Liu et al, 2017), while prairie dog disturbance has been reported to be related to higher palatable plant biomass (Martínez-Estévez et al, 2013). Prairie dog disturbance encourages the arid grassland in North America to shift from annual plants to perennial plants, in which blue gramma (Bouteluoa gracilis ) and vine mesquite (Panicum obtusum ) are usually perennial plants that are palatable for livestock (Sierra-Corona et al, 2015), whereas plateau pika disturbance enables alpine grassland composition to change from sedge to unpalatable broad-leaved plants in the Qinghai-Tibetan Plateau (Pang & Guo, 2018). In this case, plateau pikas preferentially consume dicotyledons, and most dicotyledons are unpalatable plants (Pang & Guo, 2017;Zhao et al, 2013).…”

“…As the disturbance intensity increases, the palatable plant biomass, plant species richness, soil organic carbon stock, soil total nitrogen and phosphorus stocks show downward parabolas, demonstrating that there is a threshold of plateau pika disturbance intensity for maximizing the forage availability, biodiversity conservation, carbon sequestration, and soil nitrogen and phosphorus maintenance services. When the disturbance intensity is within the threshold of disturbance intensity, plateau pika disturbance can enhance soil total nitrogen (Li et al, 2014) and organic carbon accumulation (Yu et al, 2017b), increase palatable plant biomass (Pang & Guo, 2018) by improving the growth potential of grass plants (Wang et al, 2012b), and encourage more hygrophytes and mesophytes, annual and perennial, common and rare plants to coexist (Guo et al, 2012b), contributing to higher forage available, biodiversity conservation, carbon sequestration, soil total nitrogen and phosphorus maintenance services. When the disturbance intensity is below the threshold of disturbance intensity, the dominant sedge plants place great competitive pressure on grass plants, which leads grass plants to maintain a low percentage (Pang & Guo, 2018;Wang et al, 2012b) and makes it difficult for rare plants to coexist.…”

“…When the disturbance intensity is within the threshold of disturbance intensity, plateau pika disturbance can enhance soil total nitrogen (Li et al, 2014) and organic carbon accumulation (Yu et al, 2017b), increase palatable plant biomass (Pang & Guo, 2018) by improving the growth potential of grass plants (Wang et al, 2012b), and encourage more hygrophytes and mesophytes, annual and perennial, common and rare plants to coexist (Guo et al, 2012b), contributing to higher forage available, biodiversity conservation, carbon sequestration, soil total nitrogen and phosphorus maintenance services. When the disturbance intensity is below the threshold of disturbance intensity, the dominant sedge plants place great competitive pressure on grass plants, which leads grass plants to maintain a low percentage (Pang & Guo, 2018;Wang et al, 2012b) and makes it difficult for rare plants to coexist. Once the disturbance intensity surpasses its threshold, low soil water content in alpine grassland (Liu et al, 2013) only sustains the xerophytes and mesophytes, most of which are unpalatable (Pang & Guo, 2018), resulting in reductions in palatable plant biomass and plant species richness.…”