干旱区生态环境知识资源中心

In the last two decades different native and introduced species of saltbushes (Atriplex: Chenopodiaceae) have been extensively used to increase food resources for domestic livestock in some desertified areas of arid and semiarid Chile. Much of the present knowledge on the environmental impact of such revegetation programs refer to domestic livestock, and little is known on the effects of saltbush litter on soil chemical properties, soil mesofauna, microflora and on decomposition processes. The aim of this paper is twofold: (1) to review some recent ideas regarding surface litter decomposition in desert areas and their applicability to understanding litter decomposition processes and desertification in north-central Chile and (2) to report the results of a study on surface litter decomposition of three Atriplex species (A. repanda, A. semibaccala and A. nummularia). The study was conducted in the coastal desert of north-central Chile (Coquimbo, IV Region, 30 degrees S). After one year in the field, litter of A. repanda showed the highest mass losses (18%), followed by A. nummularia (16%) and by A. semibaccata (11%), differences were significant. For desert areas these mass losses are among the lowest reported in the literature. Reduction in organic matter was about 52% during the first year. Differences were not significant among the litter of the three species of Altriplex. The curves of decrement of organic matter followed a three step (phases) pattern. During the initial 150 d (dry season) the average percentage of organic matter losses was about 10%, then it increased to 35% in the nest 150-270 d (wet season). to decrease to about 7% during the final 270-330 d (dry season following year). This result was a function of the amount of rainfall of the respective phases (0, 119.5 and 2 mm respectively). Total N content decreased gradually, while P decreased erratically. Other mineral constituents of the litter showed strong increments through time.