Productive performance of alternative land covers along aridity gradients: Ecological, agronomic and economic perspectives

BALDI, G.; JOBBÁGY, E.G.; VON BERNARD, T.; VON BERNARD, T.; MURRAY, F.; VIGLIZZO, E.F.; MURRAY, F.; VIGLIZZO, E.F.; BALDI, G.; JOBBÁGY, E.G.

AGRICULTURAL SYSTEMS

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2016 vol. 149 p. 20 - 29

0308-521X

The replacement of natural vegetation by pastures and extensive crops is generally driven by economic incentivesand supported by technology improvements and multiple subsidies. However, towards areas of increasingaridity the productive performance of these replacements may decline from all perspectives ? ecological to agronomicto economic ? due to intrinsic differences in the structural and physiological adjustment of natural and cultivatedvegetation to reduced and fluctuating water availability. We compare natural woody vegetation,perennial C4 pastures and annual crops (maize, soybean and wheat) along a gradient of decreasing precipitation(900?400 mm of annual mean) encompassing the current agricultural frontier of the Dry Chaco and WesternEspinal ecoregions of South America. We assess (i) aboveground net primary productivity (ANPP) (ii) yields ofproduct dry mass, edible energy and protein outputs and, (iii) economic gross profits and return of investment.We linked climatic with yield data from national statistics, field trials and empiric models, togetherwith productiveparameters and market prices obtained from local consultants and economic bulletins. Maize achieved thehighest ANPP of all vegetation covers (+42% in average compared to the rest) along the entire precipitation gradient,while the rest of the crops were very similar to natural vegetation. Pastures approached theANPP of naturalvegetation in the humid range, but had the lowest performance below700mm(−15%). Along the entire precipitationgradient, maizewas outstanding in mass and edible energy yieldwhile soybeanwas so in protein production.Soybean had the highest gross profit per hectare (+50%) and total capital return of investment (+70%).Pastures offered the highest functional capital return of investment (+98%; without fixed capital, infrastructureand land value costs), explaining their relevance at the onset of the deforestation process and the gradual prevalenceof crops afterwards.While agronomic and economic incentives for natural vegetation replacement remainstrong along thewhole aridity gradient, crop choice rather than land use system seemto shape the key ecologicalprocess of net primary productivity.