Effect of Nutrient Addition on the Productivity and Species Richness of Grassland Along With an Elevational Gradient in Tajikistan

Abstract

Grasslands provide key resource for the millions of people who are dependent on livestock in Tajikistan. Productivity and species richness (SR) are important characteristics of grassland ecosystems and are greatly affected by nutrient inputs. The effect that climate change might have on these characteristics remains unclear. Here, an in situ nitrogen (N) and phosphorus (P) fertilization experiment was conducted at four sites along with an elevational gradient (650, 1,100, 1,250, and 2,000 m) in western Tajikistan over 2 years (2018 and 2019) to examine the influences of nutrient availability and climate change on aboveground biomass (AGB) and SR; precipitation and temperature were also considered to analyze the responses. It demonstrated that enrichment with N, P, and their combinations significantly increased AGB along with an elevational gradient (p < 0.05). AGB increased as the concentrations of nutrients added increased. The maximum AGB, which was 2-fold higher compared with control, was observed when 90 kg N ha–1year–1 and 30 kg P ha–1year–1 were added. In addition, nitrogen addition alone stimulated greater AGB than P addition, although no significant difference was observed between these two treatments. Enrichment with N, P, and their combination had no significant effect on SR; however, SR significantly changed at different elevation. Elevation had direct effect on precipitation and temperature, which, in turn, resulted in variation in AGB and SR. Moreover, both nutrient and elevation had significant effect on AGB and SR, but there was no interaction effect of them. AGB and SR interacted with significant negative correlation. In the high-elevation area, plants grew better in the warmer year (2018); this indicates that grasslands in high mountain areas in Tajikistan might have higher productivity as the climate warms, which will positively affect the economic development of the country.

Nutrient addition alters plant community productivity but not the species diversity of a mountain meadow in Tajikistan

“…The major differences between the negative biomass-diversity results obtained in this study and the other widely detected relationships could be linked to nutrient levels and light competition ( Zhou et al., 2016 ; Li et al., 2017 ; Fayiah et al., 2019 ). In mountainous areas, climate factors also regulate plant growth ( Fan et al., 2021 ). In this study, the AGB of the dominant species fluctuated among the years with the highest values occurring in 2022 when the diversity index values were lowest ( Figures 2 , 6 ).…”

“…This may have been because P. pabularia occupied more habitat space and resources in the well-resourced environments, leading to an increase in its biomass and biomass suppression in other species, which would reduce diversity. Combining the diversity analysis with precipitation and temperature showed that precipitation and temperature in 2022 were suitable for plant growth ( Fan et al., 2021 ; Figures 1 , 2 ). As a result, an increase in the AGB of the dominant species decreased species diversity ( Stevens et al., 2004 ; Koerner et al., 2018 ) through light competition ( Hautier et al., 2009 ; DeMalach and Kadmon, 2017 ), which caused a negative biomass-diversity relationship.…”

“…Tajikistan is a typical mountainous country in Central Asia with considerable amounts of grassland. The grassland distribution mainly extends between 300 and 4000 m above sea level, resulting in various microclimates and grassland varieties ( Fan et al., 2021 ). Grasslands are crucial resources for the Tajikistan economy.…”

The influence of precipitation timing and amount on soil microbial community in a temperate desert ecosystem

“…Plant growth and primary productivity are known to be stimulated by increased precipitation amounts, as supported by various studies (Robertson et al, 2009;Bao et al, 2020;Cheng et al, 2021;Fan et al, 2021). However, the water requirements of plants vary during different developmental stages (Gutierrez et al, 2010;Alam et al, 2021;Sun H. et al, 2021), with higher water requirements in the early growing season than in the late growing season for optimal growth (Sun R. et al, 2021).…”