PRS™-probes are a valuable tool for ecology research because they are a functional measure of bioavailable nutrient supply rates. There are basic reasons why PRS™-probes are a relevant ecological tool; such as, they can be used in-situ and are sensitive to soil water content and temperature. In other words, PRS™-probes provide a measurement that accounts for temporal variability in soil nutrient bioavailability. This allows the PRS™-probes to capture nutrient pulses as affected by rainfall simulation or to measure the longer-term dynamics of nutrient flux due to temperature manipulation and CO₂ flux treatments. A traditional chemical-based soil extractant is a static measure that may miss nutrient pulses or long-term nutrient supply rate changes. A functional measure of soil nutrient supply rate is important for describing plant response to climate manipulation experiments.

Additionally, PRS™-probes provide a holistic, perceptive measure of soil nutrient supply rates because they measure variations in nutrient availability as influenced by soil chemical, physical, and biological properties. Chemical-based soil extractant are most sensitive to chemical differences between soils and are insensitive to the influence of soil physical and biological properties on nutrient bioavailability. Furthermore, chemical-based soil extractants are biased under certain soil pHs or are inaccurate in some soil types. This discrepancy makes soil nutrient data hard to compare between research sites. On the other hand, the PRS™-probe functions the same across soil types and pHs. This makes the PRS™-probe an invaluable tool for comparing the response of soil nutrient supply rates to climate change across LTER and LTSP sites and, for that matter, across the world!

Supply rate of soil P decreases in elevated CO₂ plots
Johnson et al (2001) used PRS™-probes to measure the soil supply rate of NO₃, NH₄, and P from elevated and ambient CO₂ treatments in a Florida scrub oak system. Initially, the soil P supply rate was much lower with elevated CO₂, but the difference decreased over time (Table 1). The authors concluded the decrease in the soil P supply rate was most likely the result of increased plant uptake of P in the elevated CO2 chambers.

Table 1

PRS™-probe Related Literature:

1. Johnson, D.W., Hungate, B.A., Dijkstra, P., Hymus, G., and Drake, B.J. 2001. J. Environ. Qual. 30: 501-507.
   Effects of elevated carbon dioxide on soils in a Florida shrub oak ecosystem.
2. Johnson, D.W., Hungate, B.A., Dijkstra, P., Hymus, G., Hinkle, C.R., Stiling, P., and Drake, B.J. 2003. Ecol. Appl. 13: 1388-1399.
   The effects of elevated CO2 on nutrient distribution in a fire-adapted shrub oak forest.

Studying the role of soil nutrient dynamics in non-native plant invasion is vital in understanding ecological processes responsible for non-native plant establishment. The PRS™-probes provide a holistic picture of soil nutrient supply rates because the anion PRS™-probe simultaneously adsorbs NO₃^--N, P, S, Al, Fe, Mn, Cu, Zn, B, and Pb while the cation PRS™-probe adsorbs NH₄⁺-N, K, Ca, and Mg. The PRS™-probes provide a measure of nutrient bioavailability that goes beyond the difference in nutrient quantity to functional data on the interaction of nutrient supply rates and their role in plant community dynamics. For example, a chemical-based soil extractant is an index of the quantity of nutrients which are extracted separately by different chemicals. Data from these chemical-based, "traditional" soil tests may miss which nutrient is truly limiting establishment or may underestimate the role of nutrient interactions in plant invasion. PRS™-probes adsorb accompanying nutrients which accounts for factors important to the amount of nutrients plants can uptake; such as, soil solution ion activity.

Role of fire frequency on changing N availability and its effect on cheatgrass invasiveness: To burn or not to burn
In much of the Intermountain West, many acres of historically Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh) - bunchgrass communities are being invaded and dominated by cheatgrass (Bromus tectorum L.). The hypothesis for explaining the successful establishment of cheatgrass in these areas is increased fire frequency. Drs. Kirk Davies, Roger Sheley and Jon Bates, with the USDA-ARS in Burns, Oregon, used PRS™-probes to measure the difference in soil nutrient supply rates between six plots burned 4-years prior to cheatgrass seeding and six un-burned control plots (0.4 ha plots). The total N supply rate (NH₄^-N + NO₃-N) was 1.5 times larger and cheatgrass density 300% greater in un-burned plots than in burned plots (Fig. 1). However, there was no in soil supply rates of K and P between burned and un-burned plots. Using this data, along with additional data, the researchers concluded that prescribed burning may actually increase the resistance of late seral Wyoming big sagebrush communities to cheatgrass invasion.

Fig. 1. Mean (n=6) soil nutrient supply rates (+ SE), mentioned using in situ burials of PRS™-probes, over the growing season for the burned and un-burned control plots. For each nutrient, different lower case letters indicate significant differences between treatments (P < 0.05).


This is just a sampling of the ecological research projects that have benefited from using PRS™-probes. We sincerely believe PRS™-probes are a valuable tool for virtually any ecological project in which plant available soil nutrients play a role in determining plant community composition, structure, diversity, and productivity.