Abstract
Extreme climate events and nitrogen (N) deposition are increasingly affecting the structure and function of terrestrial ecosystems. However, the response of plant biomass to variations to these global change drivers is still unclear in semi-arid regions, especially in degraded sandy grasslands. In this study, a manipulative field experiment run over two years (from 2017 to 2018) was conducted to examine the effect of rainfall alteration and nitrogen addition on biomass allocation of annuals and perennial plants in Horqin sandy grassland, Northern China. Our experiment simulated extreme rainfall and extreme drought (a 60% reduction or increment in the growing season rainfall with respect to a control background) and N addition (20 g/m2) during the growing seasons. We found that the sufficient rainfall during late July and August compensates for biomass losses caused by insufficient water in May and June. When rainfall distribution is relatively uniform during the growing season, extreme rainfall increased aboveground biomass (AGB) and belowground biomass (BGB) of annuals, while extreme drought reduced AGB and BGB of perennials. Rainfall alteration had no significant impacts on the root-shoot ratio (R/S) of sandy grassland plants, while N addition reduced R/S of grassland species when there was sufficient rainfall in the early growing season. The biomass of annuals was more sensitive to rainfall alteration and nitrogen addition than the biomass of perennials. Our findings emphasize the importance of monthly rainfall distribution patterns during the growing season, which not only directly affect the growth and development of grassland plants, but also affect the nitrogen availability of grassland plants.
Highlights
Extreme climate events and nitrogen (N) deposition are increasingly affecting the structure and function of terrestrial ecosystems
We addressed the following questions: (1) how do aboveground biomass (AGB), belowground biomass (BGB), coarse roots biomass (CR) and fine roots biomass (FR) of annuals and perennials change with rainfall alterations and nitrogen addition? (2) How do the allocation of AGB and BGB between annuals and perennials differ in their response to changes in rainfall and N?
Rainfall manipulation and nitrogen addition in different years had significant effects on AGB, BGB, CR and FR of annuals and perennials in sandy grassland, but the interactive effects of rainfall and nitrogen had no significant effect on biomass (Table 1)
Summary
Extreme climate events and nitrogen (N) deposition are increasingly affecting the structure and function of terrestrial ecosystems. A manipulative field experiment run over two years (from 2017 to 2018) was conducted to examine the effect of rainfall alteration and nitrogen addition on biomass allocation of annuals and perennial plants in Horqin sandy grassland, Northern China. By contrast, delayed rainfall often increases the availability of soil water at the later stage of growth, delaying the plant senescence[20] It is less known how excessive rainfall and extreme drought affect biomass allocation among years with different rainfall distribution during the growing season. Little is known with respect to how rainfall changes, N deposition and their interaction in semiarid grasslands will affect the allocation of aboveground and belowground biomass distribution of annuals and perennials
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
