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March 5, 2007 1. Extra-credit trip reports 2. 2 assignments 3. MOVE BACK exam questions 4. Desert restoration, follow-up on guest speaker. Manuscript Critiques Due March 26 (see handout) Topical Proposals Due April 2, reviews April 11 (see handout).

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slide1

March 5, 2007

1. Extra-credit trip reports

2. 2 assignments

3. MOVE BACK exam questions

4. Desert restoration, follow-up on guest speaker

slide10

Manuscript Critiques

Due March 26 (see handout)

Topical Proposals

Due April 2, reviews April 11 (see handout)

slide11

MOVE BACK exam questions from March 7 to March 19, 3:00 pm!!!!!!!!

You can still email them any time beginning March 7 before spring break!

Exam 2, per your vote, will include prairie/savanna restoration, amphibian guest lecture, desert restoration guest speaker, desert restoration, Red Rock Canyon virtual tour, and questions about the March 19 lecture on landscape ecosystem perspective will be included.

It would be good to at least skim the highlights of the Beginner’s Guide to Desert Restoration, and the abstracts to the supplemental journal articles listed on the syllabus for the Desert Restoration and Landscape Ecosystem Perspective categories (not Manipulating Successional Trajectories category nor the 2 papers in the Prairie/Savanna category).

slide12

Types of Disturbances in the Mojave Desert (and other deserts)

  • Linear features (e.g., powerlines, roads)
  • Fire
  • Off-road vehicles
  • Hydrological damage (e.g., Owen’s Lake)
  • Abandoned agricultural lands
  • Air pollution
  • Grazing
  • Cactus poaching/mesquite harvest, and so on
slide16

Burro sightings in Lake Mead NRA, 1991-20051

Yellow lines = aerial surveys

NEVADA

ARIZONA

1Map provided by GIS division, Lake Mead NRA

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Disturbance Effects

  • Differ among disturbance types (e.g., some just remove vegetation, others remove soil/nutrients
  • Some acute (e.g., powerline); others less intense but more widespread (e.g., grazing)
  • Alter species composition
  • Initiate undesirable trajectories (exotics-fire)
  • Destroy soil crusts
  • Increase erosion, reducing air quality
  • Release carbon to the atmosphere
slide21

Reference Conditions

  • As in most ecosystems, depend on objectives/scale/time frame, and nature of degradation
  • e.g., blend ORV tracks into surroundings – reference is surroundings – simple trajectory
  • Past (e.g., pre 1900s) conditions not necessarily as well known as in some systems, like ponderosa pine forests
  • Alternative techniques: charcoal example from Sonoran Desert wetlands
slide23

Davis, O.K., T. Minckley, T. Moutoux, T. Jull, and B. Kalin. 2002. The transformation of Sonoran Desert wetlands following the historic decrease of burning. Journal of Arid Environments 50:393-412.

The analysis of sediments from six wetlands (cienegas) in the Sonoran Desert of Arizona, U.S.A., and Sonora, Mexico, document a marked expansion of wetland taxaFparticularly woody plantsFabout 200 years ago at the beginning of the historic period, following a decrease in charcoal percentages and increased percentages of the dung fungus Sporormiella. The presence of charred seeds and fruits of wetland plants in prehistoric sediment establishes burning of the cienega itself. The charcoal decline ca. 250 years ago precedes the first occurrence of the pollen exotic plants at several sites, the change of cienega sediment from silt to peat, and the increase of percentages of the decay fungus Tetraploa. We conclude that prior to the historic period, burning was frequent enough to exclude most woody plants (Celtis, Cephalanthus, Populus, Fraxinus, Salix) from the wetlands and suppress the abundance of bulrush (Scirpus). The cienegas were probably burned seasonally as a management tool to harvest animals and promote agriculture. Prehistoric agricultural utilization of the cienegas is demonstrated by the presence of corn (Zea) and pre-Columbian weeds. This study also records postsettlement (ca. 200 years ago) change of upland vegetation; i.e. an increase in the abundance of Juniperus, Quercus, Larrea, and Prosopis pollen. Historic fire suppression may have permitted the expansion of these non-wetland woody species.

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A Beginner’s Guide to Desert Restoration Manual

  • Restoration planning (general process same here, as in any other ecosystem)
  • Soil salvage and replacement
  • Water mgt (incl irrigating plants)
  • Plant genetic considerations
  • Techniques for plant establishment
slide31

Seeding in North American deserts has been cited to be “successful” in only 1 year in 10.

However……

slide32

Fall

2005

Spring

2006

slide33

Fall

2005

Spring

2006

slide35

Wallace et al. 1980. The challenge of a desert: revegetation of disturbed desert lands. Great Basin Naturalilst Memoirs 4:216-225.

  • Principles developed largely from 1960s-70s work revegetating Nevada Test Site
  • Water clearly critical, but timing and amount per rainfall event just as (or more) important than total quantity
  • May need to manipulate water, sometimes via catchments and terrain manipulation
  • Episodic nature of perennial plant recruitment and replenishment of annual plant seed bank
  • Fertile island structure – concentrated resources, establishment microsites
  • Some pioneer plants can establish in interspaces
slide36

Wallace et al. 1980. The challenge of a desert: revegetation of disturbed desert lands. Great Basin Naturalilst Memoirs 4:216-225.

  • Animals control survival and growth of many species of plants (jackrabbits, pocket gophers, burros, etc.)
  • While water clearly often limiting, do not forget about soil nutrients, particularly nitrogen
  • Must tailor restoration to disturbance type
slide37

This has been the briefest of introductions to desert restoration. However, we will continue to touch on topics important to desert restoration during the remainder of the class – soil restoration, seed banks, landscape ecosystem perspective, human dimensions, and practical constraints, as well as in Wednesday’s virtual tour of Red Rock.

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