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Land cover change affects the amount and reactivity of DOM exported from old growth and regenerating forests in headwater ecosystems
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  • Timothy Fegel,
  • Claudia Boot,
  • Tim Covino,
  • Kelly Elder,
  • Ed Hall,
  • Banning Starr,
  • Charles Rhoades
Timothy Fegel
USDA Forest Service Rocky Mountain Research Station
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Claudia Boot
Colorado State University
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Tim Covino
Colorado State University
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Kelly Elder
USDA Forest Service Rocky Mountain Research Station
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Ed Hall
Colorado State University, Colorado State University
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Banning Starr
USDA Forest Service Rocky Mountain Research Station
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Charles Rhoades
USDA Forest Service Rocky Mountain Research Station
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Abstract

Headwater forest ecosystems of the western U.S. generate a large portion of the dissolved organic matter (DOM) transported across North America. Land cover changes that alter forest structure and forest species composition affect the quantity and composition of DOM transferred to aquatic ecosystems. Clear-cut harvesting effects ~1% of the forest area of North America annually, leaving most forests in varying stages of successional regrowth, and the total area of old-growth forest decreasing. The consequences of this widespread management practice on watershed carbon cycling remain unknown. We investigated the role of land cover change from old-growth subalpine forest to lodgepole pine dominated second-growth on the character and reactivity of DOM hillslope exports. We evaluated inputs of DOM from litter leachates and export of DOM collected at the base of trenched hillslopes during a three-year period (2016-2018) at the Fraser Experimental Forest in northcentral Colorado, USA. Dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) were higher in lateral subsurface flow draining old- versus secondary-growth forest. Fluorescence spectroscopy showed that the DOM exported from the old-growth forest was more heterogeneous and aromatic and that proteinaceous, microbially processed DOM components were more prevalent in the second-growth forest. Biological oxygen demand (BOD) assays revealed much lower microbial metabolism of both DOM inputs from litter leachate and subsurface exports from old-growth forest. Old-growth and second-growth forests are co-mingled in managed ecosystems, and our findings demonstrate that the influence of species composition on DOM inputs can affect the reactivity of DOM transferred from terrestrial to aquatic ecosystems.

Peer review status:UNDER REVIEW

25 Sep 2020Submitted to Hydrological Processes
26 Sep 2020Submission Checks Completed
26 Sep 2020Assigned to Editor
30 Sep 2020Reviewer(s) Assigned
24 Nov 2020Review(s) Completed, Editorial Evaluation Pending
04 Jan 2021Editorial Decision: Revise Major
18 Feb 20211st Revision Received
22 Feb 2021Submission Checks Completed
22 Feb 2021Reviewer(s) Assigned
22 Feb 2021Assigned to Editor
11 Apr 2021Review(s) Completed, Editorial Evaluation Pending
12 Apr 2021Editorial Decision: Revise Minor
05 May 20212nd Revision Received
06 May 2021Submission Checks Completed
06 May 2021Assigned to Editor
06 May 2021Reviewer(s) Assigned
16 May 2021Review(s) Completed, Editorial Evaluation Pending
17 May 2021Editorial Decision: Revise Minor
18 Jun 20213rd Revision Received
19 Jun 2021Submission Checks Completed
19 Jun 2021Assigned to Editor
19 Jun 2021Reviewer(s) Assigned