IRCEB Project

IRCEB Project Data from IRCEB Project IRCEB Project: Interannual climate variability and ecosystem processes Global climate is predicted to include increased variability in temperature and precipitation, i.e. more periods of drought and extra precipitation, more heat waves and unexpected frosts. This experiment was designed to monitor ecosystems processes during an experimentally produced anomalously warm, wet or dry year and to see if the unusual climate year had effects that carried over into the following year. The experimental infrastructure was installed in 2002 with data gathering beginning in the summer of 2002. Warming and extra precipitation treatments were added for one year, from Feb. 20, 2003 to Feb. 20, 2004. Data gathering ended in early spring of 2005. Experimental Design The experiment utilized a completely randomized block design with 2 levels of warming (ambient and +4°C) and 2 levels of precipitation (ambient and doubled). Twenty 3 x 2 m plots were placed 1.5 m apart in two rows 3 m apart. Every other plot had two 165 cm by 15 cm radiant infrared heaters suspended above it at a height of 1.4 m (Kalglo electronics Inc., Bethlehem, Pennsylvania, USA). Previous experimentation determined that, at this height, two heaters, each with a radiation output of 100 watt/m2 would warm the soil surface approximately 4°C (Wan et al. 2002). Rigorous testing has shown that the infrared radiation from the heater does not generate any visible light affecting photosynthesis (Kimball 2005). The remaining 10 plots each had two “dummy” heaters, the same size and shape as the infrared heaters, constructed of metal flashing, suspended over the plots at the same height and position as in the warmed plots. Five of the warmed plots and five of the unwarmed plots had attached “water catchments,” an angled sheet of corrugated plastic the same size as the plots. During a rainfall, these catchments directed precipitation onto the plots via three 12.5 mm diameter PVC pipes that distributed the water evenly over the plots. All plots were fitted with the PVC pipes whether or not they were attached to water catchments. With this design, extra precipitation was only supplied to the doubled precipitation treatment plots during natural rain. Heaters, dummy heaters, water catchments, and PCV pipes were in place and functional for one year, from February 20, 2003 to February 20, 2004 (the treatment year). Soil temperature in the middle of each plot was monitored hourly with automated thermocouples (Campbell Science Equipment, Logan, Utah, USA). Soil water content (volumetric) was logged at the same frequency using segmented TDR probes (time domain reflectometry, ESI Equipment, Victoria, British Columbia, Canada). Temperature was measured at 15 cm above the ground and at depths of 7.5, 22.5, 45, 75, and 105 cm. Soil water content was measured over five depth intervals, 0-15 cm, 15-30 cm, 30-60 cm, 60-90 cm, and 90-120 cm. For most of the study period, 11 of or 12 the TDR probes were functioning properly. Plots were assigned to treatments as follows: Control = plots # 2, 6, 10, 14, 18 Double precip = plots # 4, 8, 11, 16, 20 Warmed = plots # 3, 7, 12, 15, 19 Warmed & Double Precip = plots # 1, 5, 9, 13, 17 In addition to temperature and soil moisture, above-ground biomass and community structure were measured three times a year. Soil respiration and soil nutrient availability were measured once a month, and more often at critical periods. Detailed phenology data on twelve species was taken in 2003 and 2004. Root ingrowth cores were installed in 2002 and extracted in 2003 and again in 2004. Root growth was also monitored with a minirhizatron camera. Total annual precipitation at the site during the observation period was 854, 622, and 965 mm, for the years 2002, 2003 and 2004 respectively (Oklahoma Climatological Survey). 2003 being a drought year with an especially dry fall. Detailed Oklahoma climate data from the Washington mesonet site (~100 yds away from the experiment) are available from the Oklahoma Climatological Survey through their Oklahoma Mesonet Program. Complete air and soil temperature data from the experiment is given here. This is raw thermocouple data, default numbers and "bad" data have not been removed. Soil moisture and biomass data are to follow soon. Contact for Oklahoma data: Rebecca Sherry, A parallel experiment was carried out on intact monoliths of prairie in more control conditions at the Desert Research Institute in Reno, NV (DRI, The twelve monoliths were extracted from a site immediately adjacent to the experiment described above. Contact at DRI: Jay Arnone, Data NS Temperature 2002 Part 1 NS Temperature 2002 Part 2 NS Temperature 2002 Part 3 NS Temperature 2003 Part 1 NS Temperature 2003 Part 2 NS Temperature 2003 Part 3 NS Temperature 2003 Part 4 NS Temperature 2004 All NS Temperature 2005 End TECO model The Terrestrial ECOsystem (TECO) model evolves from its precursor model TCS [Luo and Reynolds, 1999]. It is a process-based ecosystem model and designed to examine critical processes in regulating interactive responses of plants and ecosystems to elevated CO2, warming, altered precipitation. TECO has four major components: canopy photosynthesis, soil water dynamic , plant growth (allocation and phenology), soil carbon transfers. The canopy photosynthesis and soil water dynamic sub-models run at the hourly time step. The plant growth and soil carbon sub-models run at daily time step. The detailed deblahion of the TECO model is in the appendix. Here is a brief deblahion. The canopy photosynthesis was simulated by a multi-layer process-based model, which mainly evolves from the model developed by Wang and Leuning [1998]. It simulates radiation transmission in the canopy based on Beer’s law. Foliage is divided into sunlit and shaded leaves. Leaf photosynthesis is estimated based on the Farquhar photosynthesis model [Farquhar et al., 1980] and a stomatal conductance model proposed by Ball et al. [1987]. Schematic presentation of TECO model. A. Canopy model; B. Soil water dynamics model; C. Plant growth model; D. Carbon transfer model. Rectangles represent the carbon pools. Soil is stratified into three layers. Ra: autotrophic respiration. Rh: heterotrophic respiration, NSC: non-structure carbohydrate. The soil water dynamic sub-model stratifies soil into ten layers. The thickness of the first layer is 10 cm and 20 cm for the other 9 layers. Soil water content of these layers is determined by mass balance between water influx and efflux. The water influx is precipitation for the surface layer and percolation for deeper layers. The water efflux includes evaporation, transpiration, and runoff. Evaporation is mainly controlled by the moisture of the first soil layer and evaporative demand of atmosphere. Transpiration is regulated by stomatal conductance, soil moisture, and root distribution. The plant growth sub-model simulates carbon allocation and phenology following ALPHAPHA model [Luo et al., 1995; Denison and Loomis, 1989] and CTEM [Arora and Boer, 2005], respectively. Allocation of assimilated carbon among the leaves, stems, and roots depends on their growth rates, and varies with phenology. Phenology is represented by annual variation of leaf area index (LAI). Leaf onset, the start of a growing season, is determined by growing degree days (GDDs). Leaf senescence is induced by low temperature and low soil moisture. When LAI is below a certain level (LAI<0.1), the end of growing season comes. The carbon transfer sub-model considers the movement of carbon from plant to soil through litterfall and the decomposition of litter and soil organic carbon [Luo and Reynolds, 1999; Barrett, 2002]. In this sub-model, a soil profile is divided into three layers with carbon movement from upper to lower layers. Carbon inputs to the soil from root growth and dead root residues are partitioned into these three layers. Download Please send a email to Ensheng Weng if you downloaded the model or have any questions. TECO model (It contains source code and test run data) Please cite the following references if you use TECO model in your studies: Weng, E. S., and Luo, Yiqi. 2008. Soil hydrological properties regulate grassland ecosystem responses to multifactor global change: a modeling analysis. Journal of Geophysical Research – Biogeosciences doi:10.1029/2007JG000539. [Download] References Weng, E. S., and Luo, Yiqi. 2008. Soil hydrological properties regulate grassland ecosystem responses to multifactor global change: a modeling analysis. Journal of Geophysical Research – Biogeosciences doi:10.1029/2007JG000539. [Download] Zhou, X., E. S. Weng, and Y. Q. Luo. 2008. Modeling Patterns of nonlinearity in ecosystem responses to temperature, CO2, and precipitation changes. Ecological Applications18:453-466. [Download]