Drought responses of forage supply increased with increasing aridity in South American rangelands (Organized oral session).

LAURA YAHDJIAN; BONDARUK VIVIANA; GASTON OÑATIBIA; FERNANDEZ ROBERTO

Montreal

Congreso; 2022 ESA & CSEE Joint Meeting.; 2022

Ecological Society of America

Background/Question/MethodsThe magnitude, frequency, and duration of droughts is increasing globally as a result ofhuman activities. The impact of drought is particularly important in rangelands, where netprimary production is closely linked to annual precipitation patterns. Consequently, theprovision of valuable rangeland’s ecosystem services, such as the supply of forage forlivestock production, can be severely affected. The objective of this study was to assess thesensitivity to drought of forage productivity in rangelands located in a wide aridity gradient inArgentina, South America, a region which economy depends mainly on agricultural products,and which is often underrepresented in scientific studies.To achieve our goals, we established comparable drought treatments among a wide range ofArgentine rangelands with contrasting climates (mean annual precipitation from 150 to1000mm/yr), simulating dry years with the same low probability of occurrence (once every 100years). We followed the International Drought Experiment protocol of reducing incomingprecipitation during three consecutive years with rain-out shelters in field plots and comparedthem with control plots. We estimated changes in forage productivity at nine experimentalsites during the peak growing season, considering the biomass accounted for by speciesfrequently consumed by domestic grazers using to local knowledge.Results/ConclusionsWe found that arid and semi-arid rangelands were more severely impaired by drought intheir forage supply than mesic rangelands. Forage productivity decreased on average by ca.50% during three consecutive drought years in arid and semi-arid rangelands, whereasmesic sites did not differ significantly between drought and control treatments. Consequently,the sensitivity to drought of forage productivity increased across the aridity gradient. Thenegative impact on forage productivity of arid and semi-arid rangelands was mainly driven bysevere reduction in the productivity of a few dominant forage species. In seven of the ninerangelands, we found detrimental effects on forage productivity during the first experimentalyear, and in five of those sites the effect of drought was accentuated with multi-yeardroughts.Our main findings indicate that the imposed extreme drought halved forage supply for themore arid sites. This pattern highlights the urgent need to implement strategies to mitigatethe detrimental consequences of expected water shortages, particularly in arid and semiaridrangelands, where forage provision is strongly associated with ecosystem conservation andhuman well-being. Our study incorporates local knowledge to improve our understanding ofthe relationship between the provision of ecological services and people’s perception.