Performing Department
Forestry and Wildland Resources
Non Technical Summary
This project consists of three different, yet related, lines of inquiry that will benefit a more than a dozen graduate and undergraduate researchers in refining their field and laboratory skills in forest soils research. The project (1) examines the reliability of a field and laboratory method to quickly determine phosphorus availability to plants.Phosphorus is a critical macronutrient for plant growth. Some soils have naturally occurring characteristics that render phosphorus unavailable for plant uptake. These characteristics are common on volcanic derived soils, which are common on forest soils near Mount Lassen and Mount Shasta in northern California. This study will relate a common field test (sodium fluoride pH) to the amount of phosphorous that is tied up by the soil. In many situations, phosphorous deficiencies would be moderated by mycorrhizal fungi that take up phosphorous and deliver it to the plant root system. Forest managers need to know when phosphorous deficiency is likely to occur, to be able to protect mycorrhizal networks or take other precautions and actions to avoid phosphorous deficiencies in tree growth.
Animal Health Component
90%
Research Effort Categories
Basic
10%
Applied
90%
Developmental
(N/A)
Goals / Objectives
This McIntire-Stennis proposal consists of three different, yet related, lines of inquiry that will benefit a more than a dozen graduate and undergraduate researchers in refining their field and laboratory skills in forest soils research.The first objective addresses the reliability of a field and laboratory method to quickly determine phosphorus availability to plants (Nichole Besyk M.S. Thesis).The second objective addresses a baseline snapshot of all organic carbon at an experimental plot in mixed conifer forest at the L.W. Schatz Demonstration Tree Farm in Humboldt County California (Hollie Ernest M.S. Thesis, one capstone project with ten undergraduate students).The third objective addresses the effects of season and vegetation/soil types on detection of Phytophthora spp. (including the pathogen that causes Sudden Oak Death, Phytophthora ramorum) (Undergraduate capstone project with promise for innovative new techniques). NaF pH Phosphorus RetentionPlant available phosphorus (P) occurs in the anionic forms H2PO4- and HPO42-. These anions are rendered unavailable (P retention) when appreciable quantities of iron and aluminum oxides and other amorphous compounds form insoluble complexes from soil solution. Allophane and imogolite (amorphous aluminum and iron oxides and oxyhydroxides) are common in volcanic-derived forest soils and cause P retention, especially under low pH conditions (Saunders, 1965).This subproject was made more attractive by the availability of archived soil samples and data from Dr. Liles' recent Ph.D. research at U.C. Davis provide us with a unique opportunity to place the last few pieces into a complex puzzle of P retention in volcanic-derived soils. Liles' studies at two of the "Garden of Eden" (GOE) sites in Northern California (Powers and Ferrell, 1996) yielded quantitative color, mineralogy, C:N ratios, and other attributes of volcanic-derived forest soils, but did not examine P retention in these soils. Phosphorus may be a limiting macronutrient in these ponderosa pine forest ecosystems. The opportunity to develop quantitative relationships between field observable measures and P retention is an exciting opportunity. Rounding out this existing dataset will provide a balanced study of P retention in volcanic-derived forest CA soils.Briefly, this research proposes to develop predictive relationships between P retention capacity of soils and: a) well-characterized soil properties for Aiken and Powellton soil series (Liles 2013a, 2013b), and b) sodium fluoride pH (NaF pH) for all soil materials sampled. The addition of sodium fluoride to a soil sample containing amorphous materials causes hydroxyl groups to be replaced by fluoride anions, thus increasing apparent soil solution pH (Fieldes and Perrott, 1966).Phosphorus cycling in forests is a component of supporting ecosystem services that are necessary for the production of all other ecosystem services.Limited phosphorus availability has strong implications for economic value and ecological quality of forest ecosystems. If soil map units are to be used as a basis for soil interpretations, such as forest productivity, a clear understanding and careful definition of P retention, and therefore P limitation, is desirable. This study will provide a better picture of covariates in P retention. Our analyses will shed light on possible models using measured soil properties (quantitative color, C:N, NaF pH, and amorphous material content) to determine levels of potential P retention. Where P retention is high, mycorrhizal uptake of P is especially critical. Mycorrhizal networks are especially susceptible to physical disruption by soil disturbance. Where there is a pronounced P retention hazard, forest managers can make informed decisions to minimize damage to such networks. In this way, managers can plan for healthy forests which continue to provide ecosystem services and products, and forests which will be best prepared to buffer against impending climate change.Organic distribution at an experimental plot in mixed coniferous forestQuantification of carbon pools are often restricted to above-ground biomass or, if soils are considered, to relatively shallow depths. The Forestry and Wildland Resources Department at Humboldt State University proposed to study the effect of variable retention thinning on carbon and water dynamics at the L.W. Schatz Demonstration Tree Farm to engage faculty in collaborative research. This subproject will quantify compartments that may be neglected in other studies: soil carbon and bulk density to a depth of 100 cm, carbon content and spatial distribution of roots to a depth of 100 cm, carbon content and thickness of forest floor components, carbon content and dry biomass of understory species, and carbon content and dry biomass of slash. These data, coupled with estimates of organic carbon in standing tree biomass will give us a comprehensive picture of organic carbon in compartments across the experimental plot.Effects of seasonality and vegetation/soil type on detection of Phytophthora spp. In forest soils.Detection of disease-causing organisms such as Phytophthora ramorum is usually accomplished by direct sampling of plant tissues or placing plant-based baits in surface waters. Less research has been accomplished from baited soil materials. This subproject examines the effect of seasonality (and therefore soil moisture and temperature) and vegetation type on the detection of Phytophthora spp. Part of this project is to build capacity for forest soils research in HSU's CORE research facility in molecular genetics.
Project Methods
1. Phosphorus Of the soil samples available for study, a subset will be analyzed in a pilot study in summer 2014. We transported archived soils from the Whitmore and Feather Falls Garden of Eden sites (stored at U.C. Davis) to Humboldt State University on January 14, 2014. Soil samples from two soil series (Powellton and Aiken) will be analyzed. These two series have been subjected to fertilization and other treatments within the Garden of Eden experiment, initiated in 1985 (Figure 3). The two treatments that this study will focus on are the control (natural soil condition) and fertilizer only plots (Powers and Ferrell, 1996). Two cores, in 10 cm depth increments from the surface to 2 m depth, were extracted from each of the three treatment plots within a block (indicated by black circles schematically). In other words, six cores were taken from control plots and six cores were taken from fertilizer-only plots.Color - Soil color, as measured by handheld chromameter (see Liles, 2013a for detailed methods), has been determined for more than 700 soil samples (Liles, 2013b; unpublished data). Typical Munsell colors for Aiken soils range from 5YR3/4 (dark reddish brown) at the surface to 2.5YR3/6 (dark red) at 30 cm (User Pedon ID 83CA063319 in NRCS Lab Characterization database).C:N ratios - These ratios were determined for more than 700 soil samples (see Liles, 2013b).Amorphous materials - In addition to the mineralogy analyses completed by Dr. Liles, we will perform a field test for amorphous material content (non-crystalline volcanic materials, i.e. allophane, imogolite). This field test is called the sodium-fluoride (NaF) pH test (NRCS, 2011) and is commonly used to classify andic (volcanic) soils (Soil Survey Staff, 2010). NaF, when added to the soil solution, releases OH- ions that had been bound to Al and Si. This is illustrated by the following reaction:Al(OH)3 + 3 F- → AlF3 + 3 OH-Si(OH)4 + 4 F- → SiF4 + 4 OH-Increased OH- in solution raises the pH. When this reaction results in a pH ≥9.4, it is a strong indicator of andic soil properties. The laboratory method involves adding 50 ml of 1 N NaF to a 1 g soil sample followed by agitation. After 2 minutes, the pH is read with an electrode in the upper 1/3 of the suspension (above the sediments). NaF pH is reported to the nearest 0.1 pH unit.New Zealand Phosphorus Retention- Phosphorus analysis will be completed at the Humboldt State University (HSU) CORE facility for student research. A batch equilibrium method called the "New Zealand P Retention" test is recommended by the Soil Survey Laboratory Methods Manual (NRCS, 2011). This test is appropriate for many soil types. It involves shaking a 5 g soil sample in a 1000 ppm P solution for 24 hours. A nitric vanadomolybdate acid reagent is added to the supernatant and the transmittance is analyzed with a spectrophotometer. The higher percent P retained, the greater the ability of that soil to bind phosphorus and make it unavailable to organisms. In preparation for this McIntire-Stennis proposal, Dr. Marshall and Graduate Student visited Stewart G. Wilson, Ph. D student at U.C. Davis, who has developed efficient laboratory methods for P analysis of many soil samples. The necessary equipment to perform P retention and NaF pH is available at HSU.Statistical Analysis - We will perform a GLM ANOVA to study differences and interactions between variables. We will also perform a regression analysis to determine which variables predict phosphorus retention. Initially, we will analyze soils from 0-10 cm and 40-50 cm depths to contrast higher organic matter in the surface and potentially higher crystallinity deeper in the profile. We are also curious about P retention in fertilized versus control plots. Less P retention in fertilized plots could suggest P saturation of retention sites by added fertilizers. More P retention in fertilized plots could suggest that P was taken up with other nutrients in ponderosa pine or soil biota before complexation by amorphous materials. No differences in P retention between fertilized and control plots could suggest that the magnitude of P inputs was very small or very large compared to the retention capacity of the soil. Further analyses of additional depths may follow, after determining the variability within replicates for the two depths stated above. The variables in this study are shown in Table 3. Each variable combination will be replicated 20 times to understand variability within test procedures.2. Carbon Soil carbon, roots and bulk density were sampled on meter squared grids placed vertically against two backhoe trenches at the L.W. Schatz Demonstration Tree Farm near Korbel, CA. Grids were subdivided into decimeter square subplots and cubic decimeter volumes were extracted to determine dry bulk density (corrected for rock fragments), soil loss-on-ignition organic matter, soil organic carbon and nitrogen (by combustion), soil texture, root dry biomass, root loss-on- ignition organic matter, and root organic carbon and nitrogen (by combustion). Significantly, soils were sampled to a depth of 100 cm and horizontally between trees.Forest floor (litter and duff) materials were sampled in transects to determine dry mass per area.. Depth to mineral surface soils were recorded. Forest floor materials were dried and weighed and subsampled for loss-on-ignition organic matter and organic carbon and nitrogen content by combustion.Understory vegetation was sampled along several transects at the study area. Biomass and dry matter per area were determined using a unit weight and nearest neighbor method (for density and biomass per individual). Plant tissue was collected and dried for the unit weight estimation and for loss-on-ignition organic matter and carbon and nitrogen determination (combustion).Slash dry mass per area was estimated using a fuels modeling procedure. Subsamples of woody material at different degrees of decomposition were prepared for loss-on-ignition for dry organic matter content and organic carbon and nitrogen determination (combustion).Statistical analysis - Carbon Statistical analyses will focus on best methods to characterize carbon variability across the study site and optimization of samples needed for designated confidence intervals for this site.3. Phytophthora Soils from franciscan complex parent material (riparian, mixed conifer, and oak woodland), and serpentine parent material (mixed conifer) were sampled in Humboldt County, Northern California. Phytophthora was baited from each soil type with Port-Orford cedar and Rhododendron leaf disc baits and cultured on plates of clarified V8 agar mixed with ampicillin, rifampin, pentachloronitrobenzene (PCNB), hymexazol, nystatin, and pimaricin (PARPNH). Phytophthora morphotypes were isolated and bacterial contamination was excluded using a modified Van Tieghem plate method. Hyphal DNA was extracted using both a NaOH extraction method and Qiagen Plant DNeasy kit to compare results. DNA was then amplified using PCR with ITS (internal transcribed spacer) primer pairs ITS4-5, ITS 4-6, and the nested primer pairs Phyto1-4, and Phyto2-3. DNA from both extraction methods were submitted for sequencing after PCR amplification. Initial sequencing produced weak and noisy results. To improve results, better isolation of hyphae when culturing, and elimination of bacteria and yeast needs to be further practiced and investigated to insure cleaner samples and to insure there is only one organism growing."Since the above work was submitted for a poster at the soils meetings we have sampled in different seasons (fall and winter 2015) and have refined out methods to exclude bacterial contamination. As we move into summer 2016, we hope to develop a technique using genetic markers and a sophisticated plate reader which could potentially speed up the identification of Phytophthora spp. from soil samples and other environmental samples.