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International Arid Lands Consortium (IALC) 1998

Nitrogen, Productivity & Soil Biota in the Chihuahuan & Negev Deserts

Nitrogen Soil biota Deserts

Titre : Nitrogen, Productivity & Soil Biota in the Chihuahuan & Negev Deserts

Date/Durée : May 15, 1998 to June 30, 2000

This project examined the response of soil biota to periodic rainfall events in the Chihuahuan Desert in New Mexico, USA and the Negev Desert in Israel. Total N, soluble N and biomass N and plant productivity were determined in both the US and Israel sites as well as the populations of selected microbes at each site (mycorrhizal fungi at both sites, bacteria in the US and nematodes in Israel). This study is the first to demonstrate that halophytes in the Negev are indeed mycorrhizal and that levels of colonization were positively correlated with soil moisture and organic matter. Arbuscular mycorrhizal fungi (AMF) colonization in the Chihuahuan samples was consistently higher than for the Negev sites. Like the Negev, these rates appear to be positively correlated with soil moisture levels, however, no significant relationship appears with nitrogen. Preliminary analysis of spore counts show a trend toward negative correlation with soil moisture. This finding would be consistent with production of propagules which are more resistant to desiccation that intraradicular hyphae. As previously shown, total heterotrophic bacteria numbers and Nitrogen Efficient Guild (NEG) member numbers were positively correlated with soil moisture. It appears that, as predicted, responses to moisture are not as dramatic in second and third wetting events. The previously demonstrated phenomenon of higher populations in the resource island immediately surrounding shrubs disappeared at extremely low moisture levels but returned as moisture increased. Finally, as predicted, Negev nematode communities respond to soil moisture. This response is reflected in rapid changes in species richness and trophic structure.

Partenaires : * Institution of Principle Investigator while on this project : New Mexico State University * Partners : Bar-Ilan University, Faculty of Life Sciences, Ramat Gan

Financement : Support for this project came from the USDA Cooperative State Research, Education, and Extension Service

Présentation : IALC

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