|Klass, Jeremy -|
|Trojan, Jacqueline -|
|Thomas, Stephen -|
Submitted to: Ecological Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 27, 2011
Publication Date: August 8, 2011
Citation: Klass, J.R., Trojan, J.M., Thomas, S., Peters, D.C. 2011. Utilizing the trophic interactions of nematodes as indicators of change in soil biota associated with the loss of bouteloua eriopda grasslands [abstract]. The 96th Ecological Society of America, August 7-12, 2011, Austin, Texas. PS 9-110. p. 30567. Technical Abstract: Conversion of perennial grasslands to shrublands is a desertification process that is important globally. Changes in aboveground ecosystem properties with this conversion have been well-documented, but little is known about how belowground communities are affected, yet these belowground communities may be important constraints on the reversal of this state change. We examined nematode community structure and feeding as a proxy for soil biotic change across a desertification gradient in southern NM, USA. We had two objectives: (1) to compare nematode trophic structure and species diversity within vegetation states representing different stages of desertification and (2) to compare nematode community structure between bare and vegetated patches because research has shown that semi-arid grasslands are highly connected via a matrix of endophytic fungi and soil biotic crusts that link vegetated and bare ground patches. The gradient included a perennial grassland dominated by Bouteloua eriopoda, the historic dominant in the Chihuahuan Desert, a duneland dominated by the native invasive shrub, Prosopis glandulosa, and the ecotone between them. We also sampled a relatively undisturbed, ungrazed B. eriopoda grassland at a nearby site to serve as an end member of our gradient. Nematode communities were sampled using soil cores to depth of 15 cm at each location in 2009 and 2010. Results showed that grasslands and mesquite dunelands had different trophic groupings; herbivorous nematode communities with lower species diversity and evenness occurred in both ends of our established gradient compared with the ecotone. Nematode communities had significantly greater numbers in 2009 than 2010 in the duneland. Herbivorous nematodes were found in greater numbers in 2009 than 2010 in the ecotone. Nematode trophic structure and herbivore communities were significantly different from all vegetation states with the highest observed diversity in the undisturbed, ungrazed B. eriopoda grassland sampled in 2010. Vegetated and bare ground patches within the two grassland sites had similar herbivore communities, especially species from the family Tylenchinae. However, dunes in the mesquite dunelande areas had significantly larger nematode abundance than interdune areas where bacteriavores dominated, mediating N transformations and possibly perpetuating the “islands of fertility” found in dunelands. Decreased nematode trophic structure and species diversity in the Jornada samples compared with the undisturbed grassland illustrate the effect of desertification on the soil biotic community. Our results show that nematodes can be used to identify changes in belowground community structure based on trophic interactions. Large-scale disturbances like desertification can have consequences on the diversity and soil biotic functioning at finer spatial scales.