Responses of tree-type and shrub-type Prosopis (Mimosaceae) taxa to water and nitrogen availabilities

VILELEA, A; RENELLA, MJ; RAVETTA, D.A.

FOREST ECOLOGY AND MANAGEMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2003 vol. 186 p. 327 - 337

0378-1127

The objective of this work was to compare the response of two tree-type Prosopis (P. alba and Prosopis flexuosa-tree) and twoshrub-type taxa (P. flexuosa-shrub and Prosopis strombulifera) to water and nitrogen availabilities. Our hypothesis was that treetypetaxa, native to high-resource environments, would be able to take advantage of water and nitrogen supplies, allocatingresources mainly to growth, while shrubs, native to low-resource environments, would divert resources to functions related tosurvival, such as storage of carbohydrates. Two water availabilities (low-water availability: W0 and high-water availability: W1)and four nitrogen treatments (0, 50, 100 and 200 mg N per seedling) were applied in a factorial greenhouse experiment. Theaddition of N did not affect the shoot:root (S:R) ratio, the rate of leaf appearance (RLA), specific leaf area, CO2 uptake (A),transpiration, water-use efficiency, C:N ratio or the amount of glucose used in total non-structural carbohydrates, nitrogen orfiber. Prosopis alba was the only species in which the addition of N resulted in a higher biomass accumulation under W1.Waterlimitation induced a decrease in growth in every taxa, except in P. strombulifera. The RLA and SLAwere unresponsive to wateravailability, but differed among species: P. strombulifera showed the lowest values for both variables. P. alba under W1 had agreater A than the other species. No significant correlation was found between SLA and A. Under both water availabilities P.strombulifera allocated glucose preferentially to reserves, and P. flexuosa (tree- and shrub-type) to growth (fiber). P.strombulifera had a greater C:N ratio than the other species. In conclusion, only P. alba was able to take advantage ofincreased water and nitrogen supplies and only P. strombulifera diverted resources to storage of carbohydrates while P. flexuosaexhibited an intermediate response pattern of allocation.# 2003 Elsevier B.V. All rights reserved.Keywords: Allocation; Low-resource environments; High-resource environments