Vegetation recovery with organic matter additions in semiarid Patagonia: is it a matter of water or nutrients?

KOWALJOW ESTEBAN; MAZZARINO MARÍA JULIA

S.C. de Bariloche

Congreso; VI Southern Connection Congress; 2010

CRUB - INIBIOMA, Universidad Nacional del Comahue - CONICET

<!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:1; mso-generic-font-family:roman; mso-font-format:other; mso-font-pitch:variable; mso-font-signature:0 0 0 0 0 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; text-align:justify; mso-pagination:none; font-size:12.0pt; font-family:"Times New Roman","serif"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:ES; mso-fareast-language:ES;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Wildfires in semiarid lands can modify soil nutrient cycling affecting vegetation reestablishment. Organic matter additions to burned soils are associated with an increase of water storage capacity and nutrient release. This work involved a three-year study of the impact of a single application of two amendments with high organic matter contents on a burned ecosystem (shrub-steppe) in semiarid Patagonia. Four treatments were evaluated: biosolids compost and municipal solid waste compost (at 40 Mg ha-1), inorganic fertilizer (100 kg N and 35 kg P ha-1), and no application. Soil moisture was monthly measured and contents of soil organic carbon, inorganic N and available P were determined after one and two years after application. Aboveground phytomass of the dominant species was evaluated after two and three years after application. Composts increased soil organic matter but, contrary to expectations, did not increase soil moisture. Both composts increased soluble N but to values much lower than the inorganic fertilizer; however, biosolids composts increased extractable P to even higher values than the inorganic fertilizer.  Compared with the control, phytomass values, especially those of perennial grasses, were higher with the inorganic fertilizer and intermediate with both composts. These results imply that, at the same soil moisture, plant growth in this disturbed ecosystem was limited by N availability.