Responses of palatable plants to climate and grazing in semi-arid grasslands of Mongolia

Abstract

Grassland ecosystems are essential resources for mobile pastoralism in drylands. Understanding the temporal variability and disturbance in palatable species in grasslands is a key issue in nature conservation and human economy. In this study, we examined plant trait responses to climate and grazing variability in semi-arid grasslands of Mongolia. Ungrazed exclosure areas were established in two nomadically grazed grasslands, Bayan-Unjuul (BU) in 2004 and Baganuur (BN) in 2016. Plant aboveground biomass (AGB) was surveyed by species inside and outside the exclosures. Plant species were classified into 11 groups on the basis of palatability, life duration, and functional type. Data on air temperature and precipitation were obtained from weather observatories, and the number of livestock was monitored by using time-lapse cameras since 2016 at BU and BN. Analysis of temporal variation from 2004 to 2019 in the ungrazed plot at BU indicated that the aridity index, which was closely correlated with precipitation, in June–July of the current year affected the AGB of both palatable and unpalatable species. Rainfall intensity in June contributed to the increase in AGB of palatable plants, in particular perennial grasses. Previous years’ aridity affected the current-year AGB, which is known as the “legacy effect”. The legacy effect was positive on perennial grasses and forbs and negative on annual forbs, resulting in a positive effect on the ratio of AGB of palatable species to total AGB. The increase in livestock numbers in summer decreased the ratio of AGB of palatable plants in the grazed plots to that in the ungrazed plots, and increased this ratio of annual forbs and unpalatable perennial shrubs. A multiple regression model showed that AGB of palatable plants in the grazed areas was controlled primarily by rainfall intensity in June of the current year and secondarily by livestock number in summer.

Keywords

• Aridity
• Dryland
• Grazing
• Mongolia
• Palatability
• Semi-arid grassland