Effects of fire and grazing on above‐ground biomass and species diversity in recovering grasslands in northeast China

Abstract

Questions:Fire and grazing can affect plant communities through different pathways in grasslands. However, little is known about how these disturbances affect plant communities in recovered semi-arid grasslands. Here we investigated effects of prescribed fire, sheep grazing and their interactions on above-ground biomass and species diversity in degraded semi-arid grasslands recovered from cropping agriculture.Location: Keerqin grasslands, northeast China. Methods:A short-term grazing and burning experiment with split-plot design was conducted, with burning applied at the main plot level and grazing applied at the subplot level. After 1 year of spring burning and 2 years of grazing by sheep, the above-ground biomass, species diversity, biomass proportion of plant functional groups and soil resource availability of the grasslands were measured and compared between treatments using a split-plot ANOVA model. Results:One-year of spring fire significantly increased above-ground biomass, while 2 years of grazing by sheep significantly decreased it. Species diversity was reduced by grazing in the burned plots but enhanced by grazing in the unburned plots. Fire significantly increased the biomass percentage of grasses and reduced that of forbs.Fire also changed soil water content and inorganic N concentration, and grazing enhanced light intensity to the soil surface. Moreover, above-ground biomass was positively related to soil water content and inorganic N concentration under both disturbances. Species diversity had a positive linear relationship with biomass percentage of grasses and a negative relationship with biomass percentage of forbs under sheep grazing.Conclusions: Both short-term fire and grazing are important in determining the above-ground biomass in degraded semi-arid grasslands, and their effects are opposite. Grazing coupled with fire has negative effects on species diversity. Thus, we advise that fire and grazing should be carefully applied when used in the same management regime to maintain above-ground biomass and species diversity in managing this grassland ecosystem.

Disturbance effects on productivity–plant diversity relationships from a 22‐year‐old successional field

“…The positive effect of mowing on taxonomic diversity in this study is consistent with the common perspective that taxonomic diversity is usually enhanced by mowing in various grasslands, up to a certain level of intensity or frequency after which it becomes detrimental (Collins et al, 1998;Yang et al, 2012). Mowing may enhance seedling germination by the removal of litter and above-ground biomass and facilitate the establishment of short-saturated species within the community and new colonists through the suppression of dominance of competitive species (Foster and Gross, 1998;Whalley, 2005;Martin and Wilsey, 2006;Huang et al, 2018), especially in highly productive grasslands (Lezama et al, 2014). In addition, increased productivity under mowing observed in this study is driven by the enhanced biomass production of grasses rather than forbs.…”

“…For instance, fertilization is often found to reduce taxonomic diversity in grasslands through changing resource heterogeneity and availability, increasing productivity, and increasing competitive exclusion among species (Hautier et al, 2009;Zhang et al, 2014;Harpole et al, 2016;DeMalach et al, 2017). In contrast, mowing usually increases taxonomic diversity through inhibition of dominant species and stimulation of subdominant or rare species within the community, allowing new colonization (Foster and Gross, 1998;Whalley, 2005;Martin and Wilsey, 2006;Huang et al, 2018). The niche-dimensional hypothesis assumes that niches are determined by limiting resources that allow for species coexistence within communities (Harpole and Tilman, 2007;Harpole et al, 2016).…”

A global meta-analyses of the response of multi-taxa diversity to grazing intensity in grasslands

“…Classical ecological theory shows that species diversity is assumed to follow a unimodal response along gradients of grazing intensity, and peaks with intermediate grazing intensity (McNaughton 1983, Milchunas et al 1988, Milchunas and Lauenroth 1993. Currently, a majority of the world's grasslands are experiencing overgrazing (Salvati and Carlucci 2015), which threatens the biodiversity of grassland ecosystems (Smith 1940, Borer et al 2014, Huang et al 2018. Therefore, a better understanding of the effects of grazing on the biodiversity of grasslands at the global scale through the Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence.…”

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

“…The grazing treatments, heavy grazing (HG), moderate grazing (MG), light grazing (LG) and no grazing (CK) were established in the study region for more than 20 years. The mean stocking rates in HG, MG, and LG were 2.68 sheep units ha −1 , 1.88 sheep units ha −1 , and 0.76 sheep units ha −1 , respectively (Wang et al, 2018). Over the long-term under grazing, the vegetation and soil properties are different from each other in treated plots (Tang et al, 2016).…”

“…Livestock grazing in sandy lands can impact vegetation and soils, leading to desertification in arid and semi-arid lands (Kraaij & Ward, 2006;Wang et al, 2015). Livestock grazing can also decrease biodiversity, reduce biomass accumulation and soil organic matter, increase soil bulk densities and alter ecosystem services (Huang et al, 2018;Tang et al, 2016;Zuo et al, 2018). Effects of grazing on plants in sandy lands are reported in seedlings, recruitment and species diversity (Lv et al, 2016;Tang, Jiang & Lv, 2014;Wang et al, 2018).…”