Ecology Letters (2011) 14: 187\uffe2\uff80\uff93194
AbstractThe degree to which rising atmospheric CO2 will be offset by carbon (C) sequestration in forests depends in part on the capacity of trees and soil microbes to make physiological adjustments that can alleviate resource limitation. Here, we show for the first time that mature trees exposed to CO2 enrichment increase the release of soluble C from roots to soil, and that such increases are coupled to the accelerated turnover of nitrogen (N) pools in the rhizosphere. Over the course of 3\uffe2\uff80\uff83years, we measured in situ rates of root exudation from 420 intact loblolly pine (Pinus taeda L.) roots. Trees fumigated with elevated CO2 (200 p.p.m.v. over background) increased exudation rates (\uffce\uffbcg\uffe2\uff80\uff83C\uffe2\uff80\uff83cm\uffe2\uff88\uff921\uffe2\uff80\uff83root\uffe2\uff80\uff83h\uffe2\uff88\uff921) by 55% during the primary growing season, leading to a 50% annual increase in dissolved organic inputs to fumigated forest soils. These increases in root\uffe2\uff80\uff90derived C were positively correlated with microbial release of extracellular enzymes involved in breakdown of organic N (R2\uffe2\uff80\uff83=\uffe2\uff80\uff830.66; P\uffe2\uff80\uff83=\uffe2\uff80\uff830.006) in the rhizosphere, indicating that exudation stimulated microbial activity and accelerated the rate of soil organic matter (SOM) turnover. In support of this conclusion, trees exposed to both elevated CO2 and N fertilization did not increase exudation rates and had reduced enzyme activities in the rhizosphere. Collectively, our results provide field\uffe2\uff80\uff90based empirical support suggesting that sustained growth responses of forests to elevated CO2 in low fertility soils are maintained by enhanced rates of microbial activity and N cycling fuelled by inputs of root\uffe2\uff80\uff90derived C. To the extent that increases in exudation also stimulate SOM decomposition, such changes may prevent soil C accumulation in forest ecosystems.
", "keywords": ["0106 biological sciences", "Nitrogen", "Plant Exudates", "Pinus taeda", "04 agricultural and veterinary sciences", "15. Life on land", "Carbon Dioxide", "01 natural sciences", "Plant Roots", "Carbon", "Trees", "Soil", "13. Climate action", "Rhizosphere", "North Carolina", "0401 agriculture", " forestry", " and fisheries", "Soil Microbiology"]}, "links": [{"href": "https://doi.org/10.1111/j.1461-0248.2010.01570.x"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Ecology%20Letters", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1111/j.1461-0248.2010.01570.x", "name": "item", "description": "10.1111/j.1461-0248.2010.01570.x", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1111/j.1461-0248.2010.01570.x"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2010-12-22T00:00:00Z"}}, {"id": "10.1111/j.1365-3040.2008.01869.x", "type": "Feature", "geometry": null, "properties": {"updated": "2026-07-26T16:18:46Z", "type": "Journal Article", "created": "2008-08-05", "title": "Fine-Root Respiration In A Loblolly Pine (Pinus Taedal.) Forest Exposed To Elevated Co2and N Fertilization", "description": "ABSTRACTForest ecosystems release large amounts of carbon to the atmosphere from fine\uffe2\uff80\uff90root respiration (Rr), but the control of this flux and its temperature sensitivity (Q10) are poorly understood. We attempted to: (1) identify the factors limiting this flux using additions of glucose and an electron transport uncoupler (carbonyl cyanide m\uffe2\uff80\uff90chlorophenylhydrazone); and (2) improve yearly estimates of Rr by directly measuring its Q10in situ using temperature\uffe2\uff80\uff90controlled cuvettes buried around intact, attached roots. The proximal limits of Rr of loblolly pine (Pinus taeda L.) trees exposed to free\uffe2\uff80\uff90air CO2 enrichment (FACE) and N fertilization were seasonally variable; enzyme capacity limited Rr in the winter, and a combination of substrate supply and adenylate availability limited Rr in summer months. The limiting factors of Rr were not affected by elevated CO2 or N fertilization. Elevated CO2 increased annual stand\uffe2\uff80\uff90level Rr by 34% whereas the combination of elevated CO2 and N fertilization reduced Rr by 40%. Measurements of in situ Rr with high temporal resolution detected diel patterns that were correlated with canopy photosynthesis with a lag of 1\uffe2\uff80\uff83d or less as measured by eddy covariance, indicating a dynamic link between canopy photosynthesis and root respiration. These results suggest that Rr is coupled to daily canopy photosynthesis and increases with carbon allocation below ground.
", "keywords": ["580", "0106 biological sciences", "Analysis of Variance", "Nitrates", "Atmosphere", "Nitrogen", "Cell Respiration", "Temperature", "Pinus taeda", "Carbon Dioxide", "15. Life on land", "Plant Roots", "01 natural sciences", "Carbon", "Trees", "Glucose", "Oxygen Consumption", "050101 - Ecological Impacts of Climate Change", "13. Climate action", "North Carolina", "Seasons", "Least-Squares Analysis", "Photosynthesis", "Fertilizers", "Ecosystem"]}, "links": [{"href": "https://doi.org/10.1111/j.1365-3040.2008.01869.x"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Plant%2C%20Cell%20%26amp%3B%20Environment", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.1111/j.1365-3040.2008.01869.x", "name": "item", "description": "10.1111/j.1365-3040.2008.01869.x", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.1111/j.1365-3040.2008.01869.x"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2008-10-06T00:00:00Z"}}, {"id": "10.2134/jeq2015.04.0186", "type": "Feature", "geometry": null, "properties": {"updated": "2026-07-26T16:20:00Z", "type": "Journal Article", "created": "2016-02-12", "description": "Aerial extent of wetland ecosystems has decreased dramatically since precolonial times due to the conversion of these areas for human use. Wetlands provide various ecosystem services, and conservation efforts are being made to restore wetlands and their functions, including soil carbon storage. This Mid-Atlantic Regional USDA Wetland Conservation Effects Assessment Project study was conducted to evaluate the effects and effectiveness of wetland conservation practices along the Mid-Atlantic Coastal Plain. This study examined 48 wetland sites in Delaware, Maryland, Virginia, and North Carolina under natural, prior converted cropland, and 5- to 10-yr post wetland restoration states. The North Carolina sites mainly contained soils dominated by organic soil materials and therefore were analyzed separately from the rest of the sites, which primarily contained mineral soils. Soil samples were collected using the bulk density core method by horizon to a depth of 1 m and were analyzed for percent carbon. The natural wetlands were found to have significantly greater carbon stocks (21.5 \u00b1 5.2 kg C m) than prior converted croplands (7.95 \u00b1 1.93 kg C m; < 0.01) and restored wetlands (4.82 \u00b1 1.13 kg C m; < 0.001). The restored and prior converted sites did not differ significantly, possibly the result of the methods used to restore the wetlands, and the relatively young age of the restored sites. Wetlands were either restored by plugging drainage structures, with minimal surface disturbance, or by scraping the surface (i.e., excavation) to increase hydroperiod. Sites restored with the scraping technique had significantly lower carbon stocks (2.70 \u00b1 0.38 kg C m) than those restored by passive techniques (6.06 \u00b1 1.50 kg C m; = 0.09). Therefore, techniques that involve excavation and scraping to restore hydrology appear to negatively affect C storage.", "keywords": ["Soil", "Wetlands", "North Carolina", "0401 agriculture", " forestry", " and fisheries", "04 agricultural and veterinary sciences", "15. Life on land", "Delaware", "Carbon", "6. Clean water"]}, "links": [{"href": "https://doi.org/10.2134/jeq2015.04.0186"}, {"rel": "related", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/Journal%20of%20Environmental%20Quality", "name": "related record", "description": "related record", "type": "application/json"}, {"rel": "self", "type": "application/geo+json", "title": "10.2134/jeq2015.04.0186", "name": "item", "description": "10.2134/jeq2015.04.0186", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items/10.2134/jeq2015.04.0186"}, {"rel": "collection", "type": "application/json", "title": "Collection", "name": "collection", "description": "Collection", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main"}], "time": {"date": "2016-03-01T00:00:00Z"}}], "links": [{"rel": "self", "type": "application/geo+json", "title": "This document as GeoJSON", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items?keywords=North+Carolina&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=North+Carolina&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=North+Carolina&", "hreflang": "en-US"}, {"rel": "last", "type": "application/geo+json", "title": "items (last)", "href": "https://repository.soilwise-he.eu/cat/collections/metadata:main/items?keywords=North+Carolina&offset=3", "hreflang": "en-US"}], "numberMatched": 3, "numberReturned": 3, "distributedFeatures": [], "timeStamp": "2026-07-27T09:01:31.480142Z"}