Grantee Research Project Results
Final Report: Soil Enzyme Stability as an Ecosystem Indicator
EPA Grant Number: R826592Title: Soil Enzyme Stability as an Ecosystem Indicator
Investigators: Dick, Richard P.
Institution: Oregon State University
EPA Project Officer: Hahn, Intaek
Project Period: August 19, 1998 through August 18, 2000
Project Amount: $196,806
RFA: Ecological Indicators (1998) RFA Text | Recipients Lists
Research Category: Ecological Indicators/Assessment/Restoration , Aquatic Ecosystems
Objective:
The objectives of this research project were to: (1) refine the microwave enzyme stress (MWES) test for maximum sensitivity in detecting soil management/stressors as a soil quality and ecosystem indicator; (2) determine temporal dynamics of selected soil enzyme activities and MWES across diverse agroecosystems; and (3) investigate the relationship of soil enzyme activities with other soil properties to develop conceptual models on the role of enzyme activity and stability as an indicator of soil quality.
Summary/Accomplishments (Outputs/Outcomes):
Ecological assessments assist land managers and policymakers to promote long-term sustainability, yet quantifying environmental sustainability remains an elusive goal. Soil degradation, now a global problem, is the result of adverse landscape management. Soil status is an indicator of ecosystem health, and soil enzyme activity assays act as potential indicators of ecosystem health because they are: operationally practical, sensitive integrative "biological fingerprints" of past soil management, and relate to soil tilth or structure. In this study, a wide range of ecosystems, soil types, and land management practices (forestry and agriculture) were investigated to determine the potential for soil quality indicators that were sensitive to management, but with relatively stable temporal variability. A specific objective of this research project was to develop a relative index that could be calibrated independently of soil type.
In general, the forest soils had much higher activities than agricultural soils. Agricultural soils are regularly disturbed, whereas forest soils, even with recent logging, would have had surface disturbance once with no tillage. Onsite results were consistent for agricultural soils, where those soils receiving greater C inputs (cover cropping, manure, or green manure) or minimal disturbance (unmanaged) have higher activities than the soils receiving lower C inputs or regular tillage. Across the agricultural soils, the biological measurements ergosterol, fungi biomass, and biomass C correlated and showed the same treatment effects as soil enzyme activities. However, bacterial counts showed few significant differences as a function of soil management in either forest or agricultural soils. Arylsulfatase correlated with fungal biomass and ergosterol, a fungal marker. Linking this enzyme to fungi is a promising finding. Fungal-dominated soil should have higher quality because fungal hyphae are important for the formation of aggregates/soil structure. Arylsulfatase and β-glucosidase were relatively stable within a growing season, making these good candidates to predict long-term trajectory of soil management on soil quality, but by themselves, they were not independent of soil type. We overcame this difficulty by developing the following model: soil quality index = arylsulfatase + β-glucosidase activities/silt + clay content. This successfully separated managed and unmanaged soils or improved soil management having a higher soil quality over poorly managed soils, independent of soil type. This assay can be completed on composited and homogenized soil samples (to integrate spatial variability that is not possible for some soil properties such as physical properties) that have been air-dried (simplifies soil preprocessing and an advantage for commercial adoption). Combining these characteristics with the potential that this index can be calibrated and that the assays are relatively simple, makes this soil enzyme index a practical soil quality indicator that could be adopted for commercial use. This overcomes many of the obstacles for using a soil quality indicator, because nearly all soil properties vary naturally as a function of soil type, and do not lend themselves to being universal indicators.
Journal Articles:
No journal articles submitted with this report: View all 8 publications for this projectSupplemental Keywords:
media, soil, risk assessment, ecological effects, ecosystem protection, indicators, restoration, scientific discipline, soil science, methods, measurements, monitoring, geographic areas, pacific northwest, sectors, agriculture, forestry., RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Ecology, Ecosystem/Assessment/Indicators, Ecosystem Protection, Environmental Chemistry, Ecological Effects - Environmental Exposure & Risk, Agronomy, Geology, Ecological Indicators, ecological exposure, biogeochemical indicators, substrate catalysis, biomonitoring, ecosystem indicators, terrestrial, bioassay, environmental stress, soil enzyme, microwave enzyme stress test, agriculture ecosystemsProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.