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Restoration of a ponderosa pine forest increases soil CO 2 efflux more than either water or nitrogen additions
Author(s) -
Selmants Paul C,
Hart Stephen C,
Boyle Sarah I,
Gehring Catherine A,
Hungate Bruce A
Publication year - 2008
Publication title -
journal of applied ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.503
H-Index - 181
eISSN - 1365-2664
pISSN - 0021-8901
DOI - 10.1111/j.1365-2664.2008.01460.x
Subject(s) - environmental science , ecosystem , restoration ecology , thinning , biomass (ecology) , soil water , forest ecology , forest restoration , agronomy , ecology , soil science , biology
Summary1 Ecological restoration often involves returning ecosystem structure to some predisturbance reference state, but ecosystem function must also recover if restoration efforts are to be self‐sustaining over the long term. In the south‐western United States, ponderosa pine forest structure was altered by disruption of the fire regime following Euro‐American settlement. Forest structure is now being restored to presettlement conditions through the application of thinning and burning treatments. However, the effects of these treatments on below‐ground ecosystem processes remain unclear. 2 We conducted a water and nitrogen (N) addition experiment in adjacent restored and unrestored ponderosa pine stands and compared soil CO 2 efflux in response to these treatments over a 13‐month period. Our goals were to (i) quantify water and N limitation to below‐ground carbon (C) cycling in contemporary high‐density ponderosa pine forests; and (ii) determine if restoration alleviates water and N limitations. 3 Restoration thinning and burning increased soil CO 2 efflux, along with surface soil water content, temperature and herbaceous fine root biomass, while total fine root biomass decreased as a result of restoration. 4 Water and N additions increased C flux from soils to a similar degree in both restored and unrestored ponderosa pine stands, but the increase was relatively small when compared to that stimulated by restoration. 5 Synthesis and applications. An understanding of how ecosystem processes respond to treatments designed to restore ecosystem structure is critical in ensuring the long‐term success of restoration efforts. Here we show that, although water and N stimulate C flux from soils in these semi‐arid forests, restoration treatments have a much greater effect on soil C balance than increased water and N availability by themselves. This suggests that increased quality of C inputs from a recovering understorey herbaceous community is a key component of restoring ecosystem function (e.g. below‐ground C cycling) in south‐western ponderosa pine forests.