Performing Department
School of Natural Resource Sciences
Non Technical Summary
Projected climate regime shifts across the northern United States include altered precipitation patterns, lengthened growing seasons, and hotter summers, in addition to global increases in atmospheric carbon dioxide concentration. But recent trends of specialized agricultural land use suggest a general decline in agroecosystem resilience to climate variability, although the importance of specific factors in the face of complex regime shifts are unknown. Sustaining agricultural production despite climate variability and change must be a primary goal of the NDAES to address state and national issues of production elements of food security. Nonetheless there remains a critical need to isolate specific drivers of change, identify options for mitigation and adaptation, and predict land management responses to climate variability and change.North Dakota represents an ideal system to test resilience and identify vulnerabilities to climate variability and change in the US food production system for three main reasons:Latitude: The state sits at the northern edge of the nation and is particularly susceptible to warmer winters that might extend spring and fall growing seasons, and hotter summers that might substantially increase evapotranspiration potential.Precipitation: Spanning three grassland ecoregions-shortgrass steppe, mixed-grass prairie, and tallgrass prairie-North Dakota is acclimated to a distinct rainfall gradient that is predicted to be disrupted by climate variability and change.Land use: Historically home to a broad variety of crop diversity, the expansion of the Western Corn Belt has reduced crop diversity in North Dakota.Ironically, increased corn acreage at the expense of small grain and pulse crop acreage might be the opposite response agriculture should use to mitigate impacts of global environmental change, because from a plant physiology standpoint it is possible that the cool-season growth periods (early spring and late fall) will become more amenable to crop production and the summer warm-season growth period increasingly harsh. Likewise, the main invasive species of North Dakota rangeland are C3 grasses--Kentucky bluegrass (Poa pratensis) and smooth brome (Bromus inermis)--that likely enjoy a physiological advantage over native species under increased [CO2] and warmer cool-season growth periods. Some research has downplayed the effect of global warming, suggesting that C3 and C4 plants will shift compositional proportion accordingly and maintain grassland productivity. But these studies concentrate on native grassland species and do not explicitly consider the advantages that global environmental changes, such as atmospheric carbon fertilization, might afford exotic C3 invaders.Thus, major questions about response, resilience, and vulnerability surround both cropland and rangeland agriculture in North Dakota, and the state is particularly well-located to address each. North Dakota represents clear environmental, ecological, and land-use gradients, with substantial perennial grassland remaining among crop production.
Animal Health Component
0%
Research Effort Categories
Basic
100%
Applied
0%
Developmental
0%
Goals / Objectives
Determine productive capacity and resilience of North Dakota crops to increased atmospheric carbon dioxide concentration.Predict effectiveness of fire and grazing for invasive species management in North Dakota rangeland livestock production systems under predicted climate change scenarios, compared across management systems and disturbance regimes.
Project Methods
A. Experimentally-controlled environmentsGreenhouse and growth chambers will allow the control and manipulation of environmental parameters. These facilities are available through the ND AES Fargo main station. A novel contribution of the proposed work is to study these relationships at sub-ambient as well as above-ambient CO2. Many studies have reported changes at elevated CO2 but because of the difficulty of removing a gas from the atmosphere, few have studied plant responses at sub-ambient levels analogous to a pre-industrial or even 19th century atmosphere. But other research (Bond and Midgley 2000) suggests the competitive threshold between C3 and C4 plants was crossed decades ago. If so, studies that only add CO2 report linear increases based on observations of small, marginal differences in an otherwise asymptotic relationship. The proposed work is poised to make a substantial contribution to understanding how different plant groups have responded and will respond to global environmental change.Included species in the annual study consist of crop plants (see below) selected to replicate across taxonomic groups within each photosynthetic pathway to control for confounding interactions between physiology, phenology, and species-specific traits. A single and consistent variety will be used for each. The range grasses study will include Kentucky bluegrass (Poa pratensis) and smooth brome (Bromus inermis) as non-native, C3 invaders, and little bluestem (Schizachyrium scoparium) and blue grama (Bouteloua gracilis) as economically-important native, C4 range grasses.A list of annual crop species in the experimental growth chamber study. List is organized by photosynthetic pathway (C3 or C4, in bold) and taxonomic group (Family: subfamily/tribe, underlined); Poaceae = grasses, Amaranthaceae = pigweeds & goosefoots.C4 photosynthetic pathway: Poaceae: Paniceae, Foxtail millet (Setaria italica), Proso millet (Panicum miliaceum); Poaceae: Andropogoneae, Sorghum (Sorghum bicolor), Corn (Zea mays); Amaranthaceae: Amaranthoideae, Grain amaranth (Amaranthus cruentus).C3 photosynthetic pathway: Poaceae: Triticeae, Hard red spring wheat (Triticum aestivum), Barley (Hordeum vulgare); Poaceae: Aveneae, Common oat (Avena sativa); Poaceae: Poeae, Annual ryegrass (Lolium multiflorum); Amaranthaceae: Chenopodioideae, quinoa (Chenopodium quinoa).Initially, C3 and C4 plants will be grown in sub-irrigated trays to maintain soil moisture and at ambient growing season temperatures with only varied CO2 concentration, to understand the full range of variation attributable to differences in photosynthetic pathway. Beginning with the annual crops, the growth chamber will be set at the following levels of CO2 concentration: 100ppm, 250ppm, ambient (ca. 450ppm), 750ppm, and 1000ppm. A full round of CO2 treatments will be conducted before adding moisture and temperature treatments as above. Due to potential issues with acclimation and slower response rates, only three levels of CO2 concentration will be used in the growth chamber for the range grass experiment: ambient (ca. 450ppm) and two extreme levels dependent on strength of response across photosynthetic pathways as determined from the annual crop experiment.Data collectionAnnual plants will be seeded in pots of standard greenhouse growth media, timed such that all pots can go into the growth chamber between the emergence of the first and second leaves. A sufficient number of pots will allow for five independent samples to be harvested weekly for six weeks. These destructive samples will be measured for aboveground and belowground biomass, root:shoot ratio, and leaf area index, and specific leaf area index.Range grasses will be seeded in pots and grown in the greenhouse several weeks before the completion of the annual crop experiment to ensure establishment of these perennial grasses. For each round (different CO2 concentration) of the range grass growth chamber experiment, established potted plants at the same developmental stage will be placed in the growth chamber and allowed to acclimate for one week. After the acclimation period, one subset of pots will be treated by clipping all aboveground material within 1cm of the growth medium surface to simulate grazing; another subset of pots will be treated to a total defoliation by propane burner to simulate fire; and third subset will be left untreated as a control. All pots will be returned to the growth chamber. A sufficient number of pots will allow for five independent samples to be harvested at 10-day intervals for six weeks following clipping and burning treatments. These destructive samples will be measured for aboveground and belowground biomass, root:shoot ratio, leaf area index, specific leaf area index, and 13C ratio of aboveground biomass, a measure of recovery to defoliation as plants shift from root reserves to new photosynthate.Data analysisAll statistical analyses will be conducted in the R statistical environment. Package lme4 will be used to compare group means across treatments with multiple mixed-effect linear regression models. Model fit will be assessed via AIC model selection, with confidence intervals and beta coefficients from scaled data calculated to determine relative effect sizes of included parameters.B. Field plotsExperimental plots strike a balance between control over environmental conditions and the reality of actual environmental conditions. These plots have already been established at the ND AES Dickinson Research Extension Center and NDSU Albert Ekre Preserve near main campus in Fargo. These sites span an environmental gradient of soil, precipitation, and plant communities representative of broad variation across the Northern Great Plains. Existing treatments on the plots include variable species richness (based on random draws at initial planting), nitrogen and phosphorous fertilization, and a crossed clipping treatment. Year 1 of the proposed project will initiate a prescribed fire treatment by burning a subset of plots, and burn half of those plots again in Year 2 to compare response to annual fire across the moisture gradient (DREC in the more-arid west vs. Ekre in the east). Plots will be assigned to the fire treatment such that existing mini-rhizotron tubes will be equally allocated to each fire treatment.Data collectionResponse variables include aboveground biomass at the stand- and species- levels as well as belowground biomass (depth determined by in-field core data), which is measured with a root mini-rhizotron. Macros in ImageJ, an open-source image processing software, will be programmed to map and measure belowground root activity from mini-rhizotron data. Stand-level total seasonal aboveground biomass production will be estimated with pin intercept frames. Individual plant responses to fire and clipping treatments will be tracked by tagging specific grass bunches prior to burns (replicated mix of tribe-level selections across cool- and warm- season species). These responses are designed to scale up similar responses as measured in the range grasses growth chamber experiment.Data analysisAll statistical analyses will be conducted in R and will consist of multiple mixed-effect linear regression models to compare group means across treatments. Model fit will be assessed via AIC model selection, with confidence intervals and beta coefficients from scaled data calculated to determine relative effect sizes of included parameters.