Vegetation structure is as important as climate to explain ecosystem functioning across Patagonian rangelands

GAITAN JJ; OLIVA GE; BRAN DE; MAESTRE FT; MR AGUIAR; EG JOBBÁGY; BUONO GG; FERRANTE D; NAKAMATSU VB; CIARI G; SALOMONO JM; MASSARA V

JOURNAL OF ECOLOGY (PRINT)

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2014

0022-0477

Summary 1. Drylands cover about 41% of Earth?s land surface and are a key ecosystem for grazing worldwide, as 65% of their territory is used for rangelands. These production systems are largely dependent on the aboveground net primary productivity (ANPP) of natural vegetation. Thus understanding the interplay of biotic and abiotic factors controlling of ANPP, and related functions, can largely assist to design more sustainable uses for rangelands, particularly in the context of global climatic change. 2. We evaluated the relative importance of climate (temperature, precipitation and its seasonal distribution) and vegetation structure (grass cover, GC; shrub cover, SC; and species richness, SR) as drivers of ANPP, precipitation-use efficiency (PUE) and precipitation marginal response (PMR) across a broad natural gradient in Patagonian rangelands. We statistically accounted for the effects of covaring factors using structural equation modelling. 3. Climatic variables explained 60%, 52% and 12% of the variation found in GC, SC and SR, respectively. The SC increased and GC and SR decreased as towards warmer, drier, and more winter-concentrated rainfall climates. 4. Climatic variables and vegetation structure explained 70%, 60% and 29% of the variation in ANPP, PUE and PMR, respectively. Vegetation cover was a major driver of variations on ecosystem functioning, with positive effect on ANPP, PUE and PMR. GC effect on these functions was fourfold than that of SC. SR also had a significative and positive effect on functional attributes. Of the climatic variables, mean annual precipitation had the highest effect on ANPP (positive) and PUE (negative). Proportion of precipitation falling during spring-summer had the highest effect on PMR (positive). Mean annual temperature had a strong negative effect on ANPP and PUE and a positive direct effect on PMR. 5. Synthesis and applications. Our results show that vegetation structure exerted a strong control, as important as climate, on ecosystem functioning at the regional scale. Appropiate grazing management allowing maintaining and enhancing vegetation cover and SR, particularly that of grasses, could offset adverse effects on ecosystem functioning induced by global climatic change.