Chronic N additions to forest ecosystems can enhance soil N availability, potentially leading to reduced C allocation to root systems. This in turn could decrease soil CO2 efflux. We measured soil respiration during the first, fifth, sixth and eighth years of simulated atmospheric NO3\uffe2\uff88\uff92 deposition (3\uffe2\uff80\uff83g\uffe2\uff80\uff83N\uffe2\uff80\uff83m\uffe2\uff88\uff922\uffe2\uff80\uff83yr\uffe2\uff88\uff921) to four sugar maple\uffe2\uff80\uff90dominated northern hardwood forests in Michigan to assess these possibilities. During the first year, soil respiration rates were slightly, but not significantly, higher in the NO3\uffe2\uff88\uff92\uffe2\uff80\uff90amended plots. In all subsequent measurement years, soil respiration rates from NO3\uffe2\uff88\uff92\uffe2\uff80\uff90amended soils were significantly depressed. Soil temperature and soil matric potential were measured concurrently with soil respiration and used to develop regression relationships for predicting soil respiration rates. Estimates of growing season and annual soil CO2 efflux made using these relationships indicate that these C fluxes were depressed by 15% in the eighth year of chronic NO3\uffe2\uff88\uff92 additions. The decrease in soil respiration was not due to reduced C allocation to roots, as root respiration rates, root biomass, and root turnover were not significantly affected by N additions. Aboveground litter also was unchanged by the 8 years of treatment. Of the remaining potential causes for the decline in soil CO2 efflux, reduced microbial respiration appears to be the most likely possibility. Documented reductions in microbial biomass and the activities of extracellular enzymes used for litter degradation on the NO3\uffe2\uff88\uff92\uffe2\uff80\uff90amended plots are consistent with this explanation.
", "keywords": ["Nitrogen Fertilization", "Soil CO 2 Efflux", "Geology and Earth Sciences", "Science", "Atmospheric Nitrate Deposition", "Ecology and Evolutionary Biology", "Root Respiration", "0401 agriculture", " forestry", " and fisheries", "Temperature and Moisture Effects", "04 agricultural and veterinary sciences", "15. Life on land", "Root Biomass"]}, "links": [{"href": "https://doi.org/10.1111/j.1365-2486.2004.00737.x"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Global%20Change%20Biology", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1111/j.1365-2486.2004.00737.x", "name": "item", "description": "10.1111/j.1365-2486.2004.00737.x", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1111/j.1365-2486.2004.00737.x"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2004-05-07T00:00:00Z"}}, {"id": "10.1126/sciadv.aaq1689", "type": "Feature", "geometry": null, "properties": {"updated": "2026-07-27T16:19:52Z", "type": "Journal Article", "created": "2018-08-22", "title": "A keystone microbial enzyme for nitrogen control of soil carbon storage", "description": "Nitrogen-induced suppression of lignin-modifying enzyme activity contributes to soil carbon sequestration.
", "keywords": ["CHANGING ENVIRONMENT", "570", "550", "Nitrogen", "LITTER DECOMPOSITION", "Soil", "Bacterial Proteins", "Research Articles", "Ecosystem", "Soil Microbiology", "2. Zero hunger", "Science & Technology", "Bacteria", "HETEROTROPHIC ACTIVITY", "04 agricultural and veterinary sciences", "15. Life on land", "Carbon", "Enzymes", "N DEPOSITION", "Multidisciplinary Sciences", "ORGANIC-MATTER", "BIOCHEMICAL-COMPOSITION", "TEMPERATE FOREST", "13. Climate action", "SUBTROPICAL FORESTS", "Science & Technology - Other Topics", "0401 agriculture", " forestry", " and fisheries", "ATMOSPHERIC NITRATE DEPOSITION", "SIZE FRACTIONS", "CBIO"]}, "links": [{"href": "https://doi.org/10.1126/sciadv.aaq1689"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Science%20Advances", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1126/sciadv.aaq1689", "name": "item", "description": "10.1126/sciadv.aaq1689", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1126/sciadv.aaq1689"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2018-08-03T00:00:00Z"}}], "links": [{"rel": "self", "type": "application/geo+json", "title": "This document as GeoJSON", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items?keywords=ATMOSPHERIC+NITRATE+DEPOSITION&f=json", "hreflang": "en-US"}, {"rel": "alternate", "type": "text/html", "title": "This document as HTML", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items?keywords=ATMOSPHERIC+NITRATE+DEPOSITION&f=html", "hreflang": "en-US"}, {"rel": "collection", "type": "application/json", "title": "Collection URL", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main", "hreflang": "en-US"}, {"type": "application/geo+json", "rel": "first", "title": "items (first)", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items?keywords=ATMOSPHERIC+NITRATE+DEPOSITION&", "hreflang": "en-US"}, {"rel": "last", "type": "application/geo+json", "title": "items (last)", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items?keywords=ATMOSPHERIC+NITRATE+DEPOSITION&offset=3", "hreflang": "en-US"}], "numberMatched": 3, "numberReturned": 3, "distributedFeatures": [], "timeStamp": "2026-07-28T14:12:58.955110Z"}