Grazing exclusion reduces below-ground biomass of temperate subhumid grasslands of southern South America. A meta-analysis and a below-ground database.

LUIS LÓPEZ-MARSICO; MARIANO OYARZABAL; ALICE ALTESOR; JOSÉ MARÍA PARUELO

AUSTRAL ECOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2024

1442-9985

There are several plant below-ground biomass databases for grasslands, but the contribution from the southern hemisphere is minimal. Particularly, no study has compiled the published values of plant below-ground biomass for the temperate subhumid grasslands of South America. In these grasslands, called Río de la Plata grasslands, grazing is the most frequent disturbance. No study has synthesized through a meta-analysis the effect of grazing exclusion on below-ground biomass. We set two objectives: 1) To compile and synthesize data of four variables: below-ground biomass, fraction of total biomass allocated below-ground, below-ground net primary productivity, and below-ground biomass turnover rate. 2) To estimate the effect of grazing exclusion on below-ground biomass by means of a meta-analysis. There are 15 studies published on six out of eight regional sub-divisions of the Río de la Plata grasslands. The most evaluated variable was below-ground biomass, followed by the fraction of total biomass allocated below-ground, while the other two variables were scarcely registered. Below-ground biomass in the shallow portion of the soil (0-10 cm) was on average 877 gr.m-2. The fraction of total biomass allocated below-ground was on average 0.75. Below-ground net primary productivity resulted in an average of 245 gr.m-2.y-1 (estimated using the ingrowth core method) or 560 gr.m-2.y-1 (soil core method). Below-ground biomass turnover rate presented an average of 2.5 years. On average, the effect of grazing exclusion on below-ground biomass depended on exclusion time. When exclusion time was shorter than or equal to three years, grazing exclusion did not affect below-ground biomass. In contrast, when exclusion time was longer than three years, grazing exclusion reduced below-ground biomass by 62% (0-10 cm depth) and by 40% (total depth). This is the first plant below-ground database and meta-analysis of the effect of grazing exclusion on below-ground biomass for Río de la Plata grasslands.