|
|
Archived soil samples (1937-1999) and historic air quality data from the Los Angeles Basin were used for reconstructing the record of change between atmospheric NO(x) loads, soil delta(15)N values and the diversity of arbuscular mycorrhizae (AM), which are ubiquitous plant-fungus mutualists that control plant community productivity. A tripling of atmospheric NO(x) loads between 1937 and the 1970s was paralleled by soil nitrogen enrichment (delta(15)N = 3.18). From 1975 onwards, atmospheric NO(x) declined, but soils became nitrogen saturated (delta(15) N = -4 and NO(3)-nitrogen = 171mgkg(-1)). The shifts in the AM community followed 28 years of atmospheric nitrogen enrichment and coincided with the onset of soil...
|
Soil microbial activity and soil nutrients were monitored on a revegetated coal surface mine in southwestern Wyoming from the initial planting in 1982 through 1987. Total soil nitrogen (N) and organic matter did not change during this period. However, despite no changes in available phosphorus (P) concentrations, the total P declined over 50% during the five-year period, with no apparent reduction in the loss rates. The greatest loss was in the bound inorganic P pool. Moisture appeared not to limit microbial mass-C. Microbial mass-C was higher under shrubs than in interspaces and increased with time. Total organic matter did not increase. Thus, the ratio of microbial mass-C to organic matter-C increased during the...
|
The rangeland grass, Bouteloua gracilis was inoculated with its mycorrhizal symbiont, Glomus fasciculatus, to determine the influence of vesicular-arbuscular mycorrhizae on water status, stomatal behaviour and photosynthesis as well as gross plant morphology, biomass and phosphorus content. Mycorrhizal infection increased transpiration rates by over 100% with 50 to 70% lower leaf resistances to water vapour diffusion. Leaf xylem pressure was not different between mycorrhizal and non-mycorrhizal plants indicating that whole-plant resistance to water transport was reduced by more than 50%. Photosynthetic rates under saturating light conditions increased 68% with infection as a consequence of a 33% reduction in stomatal...
|
The effects of inoculation with vesicular-arbuscular mycorrhizal fungi on nonmycotrophic (plants which do not form a mycorrhizal association) colonizing annuals and on mycotrophic perennials were investigated in southwestern Wyoming. A subsoil containing no initial mycorrhizal inoculum was used, and seeds of the later successional perennials were planted. The annuals were removed from one-half of the sampling quadrats to test for the interaction of competition and mycorrhizae on the perennials. During the third and fourth years of succession, the density and percent cover of Salsola kali, the most abundant nonmycotrophic annual, decreased by one-half to one-third with inoculation. Mycorrhizal hyphae and spores were...
|
Root growth characteristics and water transport were compared between non-mycorrhizal Bouteloua gracilis and vesicular–arbuscular mycorrhizal Bouteloua gracilis infected with Glomus fasciculatus. Mycorrhizal plants did not have significantly different leaf area or root length from non-mycorrhizal plants, but did have significantly fewer and shorter root hairs. Mycorrhizal plants had 50% lower leaf resistance with no change in leaf or root water potentials; thus transpiration was increased 100% with a 50% reduction in whole-plant, soil-to-root and root-to-leaf resistance. Assuming that the difference in water uptake was due to transport via the mycorrhizal hyphae, estimated fungus-to-root transport was 2.8 × 10−5...
|
View more...
|
