Nitrogen addition and drought impose divergent effects on belowground bud banks of grassland community: a meta-analysis

Abstract

Introduction: Belowground bud banks (or bud-bearing organs) underlie grassland regeneration and community succession following ecosystem perturbations. Disturbances of nitrogen (N) enrichment, overgrazing, wildfire, and drought substantially affect grassland ecosystem succession and aboveground productivity.

Methods: To understand the magnitude and direction of the disturbances on the belowground bud banks, we conducted a meta-analysis on 46 peer-reviewed studies published from 1980 to 2023. The meta-analysis comprises 231 observations of bud bank density per unit area and 410 observations of bud bank density per tiller.

Results: Results indicate that N addition remarkably promotes bud banks densities and plant functional groups of grass in the belowground bud banks. While drought negatively affects bud banks densities and functional groups of grasses and forbs. We found that effects of the N addition and drought on the bud banks depend on the bud type, e.g., root sprouting buds, bulb buds, and dormant buds. However, grazing and wildfire have no significant effect on the bud banks.

Discussion: Our results suggest that the N addition and drought may significantly exert promotional and inhibitory effects, respectively, on belowground bud banks, critically altering plant regrowth, community succession, and grassland community dynamics.

Keywords: aboveground productivity; anthropogenic disturbances; belowground bud banks; clonal growth; clonal organs; global change.

Figure 1

The biomes and study sites over the world covered in the analyzed dataset.

Figure 2

Belowground bud-bearing organ types covered in the analyzed dataset.

Figure 3

Responses (indicated by log response ratio mean effect sizes) of belowground bud bank densities to disturbances of wildfire, grazing, drought, and N addition. Error bars represent 95%-confidence intervals around the mean effect size estimates. The asterisk (*) indicates a statistically significant effect on the belowground bud bank density (i.e., P < 0.05), while ns denotes no significant effect. Sample sizes (i.e., the number of effect sizes) are given in parentheses. The dashed vertical line indicates zero effect of the global environmental change drivers.

Figure 4

Responses of belowground bud bank densities of different bud types to disturbances of wildfire, grazing, drought, and N addition. Error bars represent 95%-confidence intervals around the mean effect size estimates. The asterisk (*, **, and ***) indicates a statistically significant effect on the belowground bud bank density (i.e., P < 0.05), while ns denotes no significant effect. Sample sizes (i.e., the number of effect sizes) are given in parentheses. The dashed vertical line indicates zero effect of the global environmental change drivers. (A) denotes the density of bud bank per unit area, (B) denotes the density of bud bank of per tiller, respectively.

Figure 5

Responses of belowground bud bank densities of different plant functional groups to disturbances of wildfire, grazing, drought, and N addition. Error bars represent 95%-confidence intervals around the mean effect size estimates. The asterisk (*) indicates a statistically significant effect on the belowground bud bank density (P < 0.05), The asterisk (***) indicates a statistically significant effect on the belowground bud bank density (P < 0.001), respectively, while ns denotes no significant effect. Sample sizes (i.e., the number of effect sizes) are given in parentheses. The dashed vertical line indicates zero effect of the global environmental change drivers.