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University of São Paulo USP (2014)

Mudanças climáticas e o acúmulo de forragem do capim-marandu : cenários futuros para o estado de São Paulo

Andrade, André Santana

Titre : Mudanças climáticas e o acúmulo de forragem do capim-marandu : cenários futuros para o estado de São Paulo

Mudanças climáticas e o acúmulo de forragem do capim-marandu : cenários futuros para o estado de São Paulo

Auteur : Andrade, André Santana

Université de soutenance : Escola Superior de Agricultura Luiz de Queiroz (University of São Paulo USP)

Grade : Maîtrise 2014

Résumé
In 2007 the Intergovernmental Panel on Climate Change presented data showing climate changes in last decades, mainly temperature increase. This change has worried scientists about the future. Therefore, studies have been made to evaluate possible impacts of future climate changes on agricultural production. The pastures in Brazil can be especially affected, because they occupy large areas, many of them on marginal land. In São Paulo state these changes can be important for palisadegrass (Brachiaria brizantha cv. Marandu), present in 7.19 million ha. Therefore, this research evaluated the impacts of climate change on palisadegrass yield in São Paulo state. Projections were created based on downscaled outputs of two general circulation models (PRECIS and ETA-CPTEC) considering the IPCC SRES scenarios A2 (high) and B2 (low). The data obtained from 23 weather stations from 1963 to 2009 was considered as current climate (base line) and future scenarios were determined from 2013 to 2040 and from 2043 to 2070. To associate the climate with palisadegrass growth, the following empirical model was used : DMAR=15.34*DDadjusted (p=0.056, r²=0.95), extracted from research conducted in São Carlos-SP-Brazil, where DMAR is dry matter accumulation rate ; DDadjusted is degree days, calculated with 17.2°C of base temperature and adjusted by one drought attenuation factor (obtained by the ratio actual/maximum soil water storage, considering three soils capacities : 40, 60 and 100 mm). Spatial interpolation was carried out using natural neighbor and kriging methods, with ArcGis 10.1 software tools. Regional analyses were realized based on the LUPA/SP census. In general, the projections showed increase on future yield potential. On soils with 40, 60 and 100 mm of storage capacity, the average annual accumulation (AAA) was, respectively, 18.4, 19.6 and 21.0 using base line data, 26.3, 27.9 and 29.8 using PRECIS output (increase about 42%) and 25.0, 26.6 and 28.7 Mg DM/ha/ano using ETA-CPTEC output (increase about 36%), considering A2 scenario in period of 2043 to 2070. The other projections show intermediate increases. Despite annual yield increase, the variation between seasons (seasonality) and years will increase. The increase in DMAR will be higher in rainy than dry season, especially in soils with low water storage capacity (40 mm) (mainly evidenced by ETA-CPTEC scenarios). For these soils, minimum and maximum DMAR (kg DM/ha/day) was respectively 15.4 (winter) and 94.6 (summer) considering base line, 22.9 (winter) and 125.1 (summer) considering PRECIS model and 18.2 (winter) and 125.9 (summer) considering ETA model, both in A2 for 2043 to 2070 scenario. The results varied a lot between regions, especially in ETA-CPTEC scenarios (extremes ranged from <+10% to >+60%). Warmer regions (west region, in general) showed higher production potential, but they will have lower relative increase in the future. These results are due to increase in temperature in all long year and decrease in water availability in winter and spring, due to higher evapotranspiration and not necessarily decrease in rain. Strategies for mitigation and adaptation were suggested, including mainly pasture and animal management to reduce effects of lower water availability, reduce greenhouse gases emissions and use of summer forage surplus.

Mots clés : Brachiaria brizantha ETA Gramínea tropical Modelo empírico PRECIS Urochloa brizantha Brachiaria brizantha Empirical model ETA PRECIS Tropical grass

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