Functional syndromes as indicators of ecosystem change in temperate grasslands

MARCOS TEXEIRA; SANTIAGO VERÓN; GONZALO IRISARRI; MARIANO OYARZABAL; LUCIANA STAIANO; SANTIAGO BAEZA; JOSÉ MARÍA PARUELO

ECOLOGICAL INDICATORS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2019 vol. 96 p. 600 - 610

1470-160X

The lack of an organizing conceptual framework to address ecosystem changes reduces our capacity to distinguishbiophysical from direct human impacts on grassland dynamics. This is particularly important for subhumidtemperate grasslands, one of the world?s most threatened biomes. We identified and mapped 4 functional syndromesof grassland change at the wettest end of its worldwide distribution, the Campos in Uruguay. Syndromeswere defined by differences in precipitation use efficiency (PUE, ANPP/precipitation), and in precipitationmarginal response (PMR, slope of the linear regression between ANPP and precipitation) between two periods(1981?1995 and 2001?2011). Temporal trends in aboveground net primary production (ANPP, obtained bysplicing two sources of NDVI, LTDR and MOD13Q1) were also characterized. To rule out the effect of precipitationwe analyzed temporal trends of the residuals from the relationship between ANPP and annual precipitation(RESTRENDS). Functional syndromes associated with increases in seasonality or in the abundance ofannual vegetation (ΔPMR > 0, ΔPUE < 0, ∼14,000 km2) and vegetation cover loss (ΔPUE < 0 andΔPMR < 0,>5000 km2) were the most abundant. ANPP trends were significantly negative in 3.7% of the area(2475 km2) and only positive in 0.3%. However, RESTRENDS were significant in 11% of the area (> 7700 km2),and mostly negative (in ∼7200 km2). Most of these negative trends and residual trends were associated toseasonality increase and vegetation loss syndromes. These patterns were consistent with observed changes in theregion. We highlight that this conceptual framework is suitable for describing patterns of change and potentialcauses. Moreover, it provides policymakers with a novel tool to guide management and conservation policies,pointing to sites where intervention (i.e. conservation, restoration) is needed.