122 research outputs found
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Patterns of soil organic matter and microclimate accompanying the death and regeneration of a mountain hemlock (Tsuga mertensiana ) forest
No full textSoil organic matter levels, soil temperature and moisture, and vegetation properties were measured along a sequence of death and
regeneration in a mountain hemlock (Tsuga mertensiana) forest. The sequence is produced by slowly moving waves of the root pathogen Phellinus weirii. While analysis of variance for all sampled soil layers indicated no change in carbon mass along the gradient, data suggested a loss of carbon in the 02 layer after stand death. Moisture in the organic layers decreased from the old growth to the young regeneration area and increased in the older regeneration area.
In contrast, both moisture in the mineral soil and temperature at three profile depths increased from the old growth to the young
regeneration area and decreased in the older regeneration area. Multiple regression analyses revealed that little variation in soil carbon levels was explained by variation in vegetation and soil microclimate
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Laws, Regulations and Action Plans for per- and polyfluoroalkyl substances found in Michigan drinking water supplies
No full textPer- and polyfluoroalkyl substances (PFASs) have emerged in the last half century as concerning global contaminants. PFASs have been found in drinking water systems causing negative health impacts for those who rely on this as their primary source of drinking water. PFASs are man-made industrial chemicals composed of carbon chains bonded to fluorine and other substances and cause detrimental impacts to the environment and human health (TOMWC, 2019c). While PFASs are not a new substance, the adverse effects are just starting to be realized. In response, Michigan is pursuing a leadership role in policy, research, training and clean-up/remediation plans for PFAS contamination with the implementation of the Michigan PFAS Action Response Team (MPART). The State of Michigan is poised to be one of the first states to enact Maximum Contamination Levels (MCLs) for some of the most impactful PFASs.
This capstone project seeks to determine the effectiveness of the current legislation and PFAS Action Plans in protecting Michigan citizens from PFAS contaminated drinking water. A review of the current and proposed federal and Michigan legislation was completed as well as the impacts associated with PFASs exposure which identified the success of current policies with regards to the environment, the ecosystem, human health, the economy and the socio-political scene. Additionally, local Northern Michigan government officials and employees of environmental organizations were surveyed to ascertain their opinions of the effectiveness of MPART, the current regulated PFASs levels and to determine what more can be done to assist local areas with current and future PFAS contamination. Key findings of the literature review and the survey illustrate a need for stricter and more detailed legislation that include nationwide MCLs for individual PFASs, further research on the impacts, with emphasis on human health. In addition, it was found that while it might be too early to determine the effectiveness of MPART, there is evidence that local officials lack the necessary training to adequately administer best practices to help mitigate PFAS contamination
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Long-term effects of prescribed fire on nitrogen availability in ponderosa pine stands in central Oregon
No full textThe effects of prescribed burning on the rates of recent litter
decomposition, nitrogen and phosphorus release from litter, soil total and
inorganic nitrogen pools, and net nitrogen mineralization were determined in
ponderosa pine sites that had been burned 0.3, 5 or 12 years earlier. Prescribed
burning decreased litter decomposition rates significantly (p >0.1), in the sites
burned 0.3 and 12 years previously, although the differences in litter
decomposition rates between burned and control plots were small. Nitrogen and
P release from recent litter was significantly higher in the plots burned 5 years
previously, but there were no significant differences in the plots burned 0.3 or 12
years earlier. Soil inorganic N concentration significantly increased shortly after
prescribed burning, but declined thereafter to reach the levels of the control
plots at the end of the next growing season. Both inorganic and total soil N
pools in soil were significantly lower in the plots burned 5 years previously, and
there were no differences in any of the N pools measured for the sites burned 12 years earlier. Prescribed burning did not significantly affect annual net nitrogen
mineralization 0.3 years after burning, but net N mineralization decreased
significantly in the 5 and 12 year burned plots. The decrease in net nitrogen
mineralization is probably caused by a decrease in substrate quantity 5 years
after burning, and by changes in substrate quality 12 years after burning. A long-term
decrease in net N mineralization in the N-poor ponderosa pine stands of
Central Oregon may result in a decrease in long-term site productivity and may
explain the observed pattern of long-term decrease in stand growth following
prescribed burning
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Thinning and urea fertilization effects on emerging grand fir (Abies grandis) foliage and growth of western spruce budworm (Choristoneura occidentalis) larvae
No full textThe objective of this study was to determine how the
balance of carbon to nitrogen in a grand fir ecosystem affects
the chemistry of emerging grand fir foliage and the growth of
western spruce budworm larvae. Forest plots in the grand fir
zone of eastern Oregon were thinned, thinned and fertilized,
fertilized without thinning, or left as a control to determine
how increased nitrogen availability alters the efficacy of
carbon-based chemical defenses at different light levels.
Thinning did not significantly alter any of the foliar
chemical fractions measured while fertilization increased the
concentration of foliar nitrogen and free amino acids.
Thinning increased tree vigor (g wood produced per m²
foliage), but fertilization only increased vigor in the
thinned plots. Fertilization increased the weights of
western spruce budworm pupae; thinning had no effect.
Male and female pupal weights correlated with foliar free
amino acid concentration and the ratios of foliar free amino
acids to foliar nitrogen, available carbohydrates, and lignin,
but stepwise regression analysis showed that foliar free amino
acid concentration alone explained most of the variation
in pupal weights.
The correlation of foliar free amino acid concentration
with male and female pupal weights, and the lack of
correlation of any indices of carbohydrate availability
suggest that changes in available nitrogen rather than changes
in the carbon/nitrogen balance were associated with changes in
larval growth. This can be attributed to either a lack of
defensive capability in the emerging foliage or a failure to
measure or manipulate the variables responsible for
controlling foliar defense. However, larval growth is only
one aspect of plant susceptibility to insects; changing the
carbon/nitrogen balance in the grand fir ecosystem may
ultimately affect the susceptibility of grand fir to western
spruce budworm by changing the balance between plant growth
and levels of plant herbivory
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Effects of nutrient and light limitation on mountain hemlock : susceptibility to laminated root rot
No full textMountain hemlock forests in the Oregon Cascades exhibit wave-form dieback resulting from infection by laminated root rot (Phellinus weirii). Although Phellinus remains viable in dead roots after the wave of dieback passes, many regenerating mountain hemlock forests do not become
immediately reinfected. We measured at least a doubling of nitrogen availability in the dieback and regrowth zones, and thought that this increased availability could improve tree resistance to the fungus. To test this hypothesis, we grew small mountain hemlocks under nutrient and light limitations
in a growth-room, and then inoculated with the fungus. Trees growing without added nutrients had significantly greater foliage damage and mortality after Phellinus
inoculation than did trees growing with nutrients. Shading significantly increased susceptibility whether or not nutrients were added. We believe that increased nitrogen
availability and possibly increased light levels after dieback in the field act similarly to increase resistance
and prevent reinfection of the regrowing stands. Foliage damage and susceptibilty to infection were related to pool sizes of total nitrogen, phosphorus, and non-structural carbohydrates. Plants with very low nitrogen reserves ( < 10 mg N per plant) , or very low energy reserves ( < 20 mg starch per plant), were more susceptible. It appears that resistance to Phellinus occurs via a defensive pathway that requires resources of both nutrients and carbohydrates
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Soil changes after afforestation in Yellow River loess : a case study in Gansu Province, People's Republic of China
No full textWidespread erosion of the Yellow River loess plateau has led to serious soil and water conservation problems for north central China. In the DingXi District of Gansu
Province, with less than 400 mm annual precipitation, terraced plantations for timber, fuel, or fodder form part of a large scale afforestation project to meet local needs as well as conservation goals. To determine changes in the calcareous (pH 8.5-9.5) loess soil due to plantations, 14 and 24 year old stands of Pinus tabulaeformis Carr. were compared to an adjacent 26 year old stand of the shrubby legume Caraana microphylla (Pall.) Lam. and to unterraced pasture and new unplanted
terraces. The 24 year old pine plot had significantly less soil nitrogen and organic carbon than the pasture or legume plots, but had higher pH than the legume plot. The
nitrogen-fixing legume maintained soil nitrogen and organic carbon levels equivalent to the pasture, and had lower pH
and bulk density in the upper horizons. Other nutrients showed no significant differences due to plantations. Nutrient depletion under pure P. tabulaeformis
plantations may limit future growth under these conditions. The shrubby legume can improve soil fertility while providing fuel and fodder in pure or mixed stands. Results from this case study suggest that the site
loses significant amounts of nitrogen from terraced plantations. Hypotheses are developed linking the alkaline and calcareous properties of the soil to loss of nitrogen made available by enhanced decomposition and mineralization of native organic matter. Weeding and cultivation (to
conserve soil moisture) and gleaning for fuel and fodder which removes ground vegetation and litter from the site may also affect the nitrogen cycle by lowering uptake,
retention, and inputs
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Biologic activity in two western Oregon Douglas-fir stands : a research link to management
No full textInformation about forest substrate respiration, nitrogenase activity and
mineralizable nitrogen may be incorporated into carbon and nitrogen budgets that comprise an important element of forest management planning. In this study, substrate respiration, nitrogenase activity and mineralizable nitrogen were measured in two western Oregon Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] stands within litter, well decayed logs and mineral soils. To examine the potential effect of living conifer roots on substrate respiration, nitrogenase and mineralizable nitrogen, the perimeters of one half the plots were trenched. After two years, there was no significant difference between plot types in respiration, nitrogenase activity or mineralizable nitrogen rates at both sites. The 75-80 year old lower elevation stand located in the Coast Range had greater levels of all three variables than the higher elevation western Cascade 450 year old stand in the H. J. Andrews Forest. At both sites, litter usually yielded greater rates of respiration, nitrogenase activity and mineralizable nitrogen than either decayed logs or mineral soils. Greater rates occurred in decayed logs than in mineral soils; rates at 4 cm in these substrates were significantly higher than rates at 20 cm. Strongest correlations were found between litter volumetric moisture content,
temperature in litter, and respiration and/or nitrogenase activity. In general, positive correlations existed between substrate moisture content and respiration; substrate moisture content and nitrogenase activity were often significantly and positively correlated. Both respiration and nitrogenase activity correlated negatively with temperature. Regardless of substrate, few significant correlations existed between
substrate moisture or temperature and mineralizable nitrogen. This study confirmed
that substrate respiration, nitrogenase activity and mineralizable nitrogen in western Oregon may be controlled more by substrate moisture content than substrate
temperature and that litter and down woody debris play an important role in determining potential nitrogen reservoirs within forests
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Leaf litter chemistry and decomposition in a Pacific Northwest Coniferous forest ecosystem
No full textThe effects of initial leaf litter chemistry of 16 common coniferous and deciduous hardwoods and shrubs on their annual decomposition patterns were studied on the H.J. Andrews Experimental Forest (Oregon). Leaf litters were characterized by their chemical qualities, which included measurement of elemental fractions (C, N, P, K, Ca, Mg), proximate fractions (non-polar, polar, acid-soluble extractives, acid-soluble lignin and acid-insoluble "Klason lignin"), and colorimetric characters (total phenolics, reactive polyphenolics, water-soluble carbohydrates, water-soluble condensed tannins, and water and acid-insoluble condensed tannins). These analytical methods improve upon traditional proximate analysis (Ryan et al. 1990) used to characterize leaf litters, through measurement of reactive and residual phenolic fractions and acid-soluble lignin. This paper discusses the procedures that are involved in improving proximate analysis and the link between leaf chemistry and one year
decomposition rates. Significant differences were found in leaf litter qualities and in
decomposition rates (expressed as decay) among species. The annual decay (k) for the leaf litter ranged from 0.27 to 1.02. The decay values for all species combined had highly significant (p [less than or equal to] 0.0001) correlations with 29 out of the 36 initial chemistry variables tested. The three highest correlations were with acid-insoluble
condensed tannins (r= 0.83 p [less than or equal to] 0.0001 n=339), the lignocellulose index (r= -0.81 p[less than or equal to] 0.0001, n=339) and acid-insoluble residue or 'Klason lignin" (r= -0.80 p [less than or equal to] 0.0001, n=339). A multiple regression model with all 16 species suggested that annual decomposition was best related to acid-insoluble condensed tannins, Klason lignin, water-insoluble condensed tannins, Ca and total phenolic:N ( R²=0.84, p [less than or equal] 0.0001, n= 339). Correlation and multiple linear regression models with each species' decay rate revealed that no one single initial chemical predictor could best explain the decomposition rates for each of the 16 species and that there were a wide range of chemical predictors related to the patterns of decomposition for each species
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Biology and chemistry of a meadow-to-forest transition in the Central Oregon Cascades
No full textIn this study, biological and chemical characteristics were determined for two high-elevation meadow-to-forest transitions located in the Central Oregon Cascades. The chloroform fumigation incubation method (CFIM) was used to determine microbial biomass C(MBC) and the N flush due to fumigation (NF), and meadow values were compared to forest values for each. Meadow and forest MBC values were also compared for estimates of MBC determined with microscopy and these values were compared to CFIM estimates. Net N mineralization and C mineralization were determined for an 85-d incubation period and used as a measure of labile C and N. Microbial biomass C and NF were then compared to these labile pools in order to investigate the relationship between the amount of each nutrient stored in biomass and the magnitude of the respective labile nutrient pool for each. Long-term and short-term net N mineralization rates and C/N ratios were also compared for meadow and forest soils, and the relationship between these two characteristics was examined. In general, microbial biomass estimates made with the CFIM method did not show any significant differences between meadow and forest soils. Mean MBC for both sites as determined by CFIM was estimated to be 369 and 406 μg C g⁻¹ soil in meadow and forest soils, respectively. Mean NF was estimated to be 37 and 56 μg N g⁻¹ soil in meadow and forest soils, respectively. MBC estimates made using microscopy showed biomass C to be greater in the forest than in the meadow. Mean MBC as determined by microscopy was estimated to be 529 and 1846 μg C g⁻¹ soil in meadow and forest soils, respectively. The NF measured as a percentage of the net N mineralized over 85 d was significantly greater in the forest than in the meadow soils, but was a substantial percentage in both. The means of these values were 30 and 166% in meadow and forest soils, respectively. This led to the conclusion that biomass N may be a very important pool of stored labile N in this ecosystem. Net N mineralization rates were almost always greater in the meadow than in the forest soils. Net N mineralization for the 10-d incubations averaged 21 μg N g⁻¹ soil in the meadow and 8 μg N g⁻¹ soil in the forest Rates for long-term N mineralization averaged 126 μg N g⁻¹ soil in the meadow and 52 μg N g⁻¹ soil in the forest. Net N mineralization rates were correlated with C/N ratios for both short-term and long-term incubations
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