SHRUBLANDS OR GRASSLANDS TO NOVEL ECOSYSTEMS Deb Peters, Jin Yao
Slide 2 Temporal context (legacies, lags, feedbacks, past &
recent management practices, climate, disturbance) Past Present
Perennial grassland Woody plant invaded grassland Coppice duneland
Environmental drivers (climate, grazing) Urban, suburban,
agricultural Future states plant plant assemblage landscape unit
Soil-geomorphic template Transport vectors Resource redistribution
Spatial context Ag land Shrubland Novel systems (exotic grasses)
Perennial grassland Jornada LTER framework (alternative states,
multiple scales, spatial and temporal context) Slide 3 Lehmann
lovegrass occurrence at Jornada McGlone CM. 2001. Response of an
introduced grass, Eragrostis Lehmanniana, to a prescribed burn in
the Northern Chihuahuan Desert: Implications for community
dynamics. NMSU Master Thesis. ERLE patches and presence GPSed
during 1998-2001 by McGlone CM. G SUMM C CALI C SAND in the 1950s
and 1960s, JER staff seeded Lehmann lovegrass for restoration or
spring forage with limited success. Current populations are
probably from seeds transported downslope from seeded populations.
Slide 4 Lehmann lovegrass increased on long-term NPP plots in wet
period (2004-2008; die off with freeze in 2011) McGlone CM. 2001.
Response of an introduced grass, Eragrostis Lehmanniana, to a
prescribed burn in the Northern Chihuahuan Desert: Implications for
community dynamics. NMSU Master Thesis. % of quadrat with ERLE G
SUMM C CALI C SAND Frequency data from NPP locations Slide 5
Regionally, Lehmann lovegrass has expanded throughout the Southwest
(county-level reporting) Data source: USDA plants database
Frequency (%) Santa Rita, AZ Lehmann lovegrass expansion (exploded)
in Sonoran Desert in 1990s; maintained thru time Frequency (%)
Basal cover (%) Invasive grass from South Africa Slide 6 Objectives
I. To quantify the climatic and edaphic controls on Lehmann
lovegrass seedling establishment and survival for: 1. the Jornada
landscape 2. the Chihuahuan Desert II. To predict its future
geographic distribution under alternative climate scenarios.
Collaboration with EF 1065699 (2011-2016) Lehmann lovegrass
invasion as a novel ecosystem in the Chihuahuan Desert Slide 7
SOILWAT Daily time step, multi-layer model of soil water dynamics
and seedling establishment Parameterized using literature values
for Lehmann lovegrass and similar native grass species Model
validation Field observations vs. simulated results Jornada
(Chihuahuan Desert) vs. Santa Rita (Sonoran Desert) SOILWAT model
parameterization and validation Slide 8 1.Establishment simulated
for 57 weather stations representing Chihuahuan Desert 2.Current
daily precipitation and temperature 3.Alternative climate scenarios
Temperature increase by 2.5 o C Vary precipitation amount (no
change, decrease or increase by 10%) 4. 6 soil types 5. Extrapolate
to entire region using regression equations and PRISM climate data
Chihuahuan Desert simulated seedling establishment Slide 9
Regression equations for extrapolation - Loamy sand and sandy loam
(examples) SoilY_intMAPPPT _Jul PPT _Sep Tmean _Dec Tmin _Jan R2R2
Current climate Loamy sand-0.300.010.040.030.74 Sandy
loam-0.400.010.030.040.65 T increases by 2.5 o C, PPT stays same
Loamy sand-0.580.020.040.89 Sandy loam-0.380.010.030.050.81 T
increases by 2.5 o C, PPT decreases by 10% Loamy
sand-0.580.020.050.90 Sandy loam-0.440.020.040.060.84 T increases
by 2.5 o C, PPT increases by 10% Loamy sand-0.570.020.040.87 Sandy
loam-0.320.010.030.040.78 N = 57, model p < 0.0001 for all
cases. Slide 10 PRISM data for current climate 1981-2010 Mean
annual precipitationMean annual temperature Slide 11 Current
climate Hotter, PPT no change Regional variation in change in
seedling establishment on loamy sand soils (mesquite) Hotter and
wetterHotter and drier Slide 12 Current climate Sandy loam soils
greater change in establishment than loamy sand soils sandy loam
(grassland) loamy sand (mesquite) Hotter and drier Current climate
Hotter and drier Slide 13 Objectives - future I. To quantify the
climatic and edaphic controls on Lehmann lovegrass seedling
establishment and survival for: 1. the Jornada landscape future
plans are to simulate the Jornada under climate change scenarios 2.
the Chihuahuan Desert II. To predict its future geographic
distribution under alternative climate scenarios. III. Continue
long-term monitoring of Lehmanns populations IV. Model results lead
to mechanistic field studies Lehmann lovegrass invasion as a novel
ecosystem in the Chihuahuan Desert
