Determinants of Caragana microphylla density distribution in the Mongolian steppe

Abstract

Regional differences in Caragana microphylla density in the Mongolian steppes were explained by considering multiple abiotic and biotic factors collectively, including aridity gradients, grazing regimes, fire disturbance, and interspecific interactions. In the central and eastern Mongolian steppes, we collected vegetation data from 127 sites. Along 250‐m line transects, the hit frequencies of C. microphylla and tall‐grass species were recorded. Ancillary data included weather information, livestock populations, fire occurrence maps, and herder camp locations. Based on the steppe types and disturbance regimes, the sites were classified into 12 sub‐groups. The data were statistically analyzed at the site, county, and sub‐group levels. The natural C. microphylla density decreased with climatic aridity from forb‐steppes to semi‐desert steppes, but this pattern was not observed at grazed and burned sites. Livestock grazing decreased C. microphylla density, but this effect was considerably confounded by aridity effects, especially in the central steppes, making the relationship between C. microphylla and livestock densities complex. Although fire appeared to be an important factor in the eastern steppes, the mechanism of its effect on C. microphylla density was unclear, because the fire–shrub interaction is influenced by the tall‐grass recovery process after fire. Based on our results, we propose that two different confounding effects, namely aridity versus grazing and fire versus interspecific interactions, play important roles in determining the spatial distribution of C. microphylla density in the central and eastern Mongolian steppes, respectively.

Livestock grazing and trampling effects on plant functional composition at three wells in the desert steppe of Mongolia

“…Second, because of its high biomass and nitrogen content, new branches of Caragana spp. can be attractive resources during spring and early summer before awn emergence in July (Jigjidsuren and Johnson 2003;Narantsetseg et al 2014), which may reduce grazing pressure on herbaceous plants at Bshrub. Edible shrubs such as Caragana spp.…”

“…In arid grasslands, though climate-driven, inter-annual variations of plant biodiversity and biomass are strong (Fernandez-Gimenez and Allen-Diaz 1999; Stumpp et al 2005), it is also clear that livestock have critical impacts on plant communities and locally participate in pasture land degradation . Because the daily feeding distance of livestock is generally constrained to a few kilometers in Mongolia (Cérénhand 2005), livestock impacts can produce finer-scale pasture heterogeneity of plant composition and standing biomass than that caused by regional climate gradients (Narantsetseg et al 2014;Narantsetseg et al 2015).…”

Earlier flowering did not alter pollen limitation in an early flowering shrub under short-term experimental warming

“…C. microphylla is a leguminous, spinose, and deciduous shrub that occurs as a main component in forb-steppe and semi-desert steppe 33 . It is the most dominant species of the 12 Caragana species found on the Mongolia steppes 34 .…”

Increased pollinator service and reduced pollen limitation in the fixed dune populations of a desert shrub

“…(Fabaceae) is a hermaphroditic, perennial shrub and the most dominant of 12 Caragana species in the Mongolian steppes 44 . C. microphylla grows up to 3 m in height and is a primary plant in the forb-steppe and semi-desert steppe 45 . In northern China, this shrub is widely planted to stabilize mobile dunes from seeds.…”