کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
9619393 | 158443 | 2005 | 15 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Is soil respiration a major contributor to the carbon budget within a Pacific Northwest old-growth forest?
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
علم هواشناسی
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چکیده انگلیسی
Carbon dioxide (CO2) exchange was measured above the forest floor of a temperate Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco) and Western Hemlock (Tsuga heterophylla (Raf.) Sarg.) old-growth forest in southern Washington State. Continuous flux measurements were conducted from July 1998 to December 2003 using the eddy-covariance technique. Maximum observed fluxes were +6 μmol mâ2 sâ1 on a monthly average in summer decreasing to +1 to +2 μmol mâ2 sâ1 in winter and early spring. Nighttime soil and understory exchange was well described by an exponential function of soil temperature at a depth of 50 mm during periods of moderate soil moisture, but moisture effects required a modification of the equation at low (0.25 m3 mâ3) and very high (0.35 m3 mâ3) soil moisture. Interannual variation was observed in soil respiration and understory carbon exchange and linked to interannual variability in soil moisture and temperature. Maximum CO2 exchange occurred at different times amongst years; a maximum daily CO2 flux was measured as early as May in 2000 and as late as July in 2001. Summer understory photosynthesis was shown to be up to â2 μmol mâ2 sâ1 with some interannual variability. Understory net photosynthesis never exceeded net CO2 efflux on a half-hourly basis, implying at no time was all of the soil respiration recycled by understory photosynthesis. Maximum daily carbon exchange ranged from +5 to +7 g C mâ2 dayâ1 in the summer months and was greatly reduced (but was still non-zero) in the wintertime due to lower soil temperatures, with daily values ranging from +0.5 to +1 g C mâ2 dayâ1. Annual estimates of soil and understory respiration range from 8.7 to 12.8 Mg C haâ1 yearâ1 for a period of 5.5 years with an average of 11.1 ± 1.5 Mg C haâ1 yearâ1. The large observed annual soil efflux is consistent with the presence of large carbon stocks at the Wind River site.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Agricultural and Forest Meteorology - Volume 135, Issues 1â4, 14 December 2005, Pages 269-283
Journal: Agricultural and Forest Meteorology - Volume 135, Issues 1â4, 14 December 2005, Pages 269-283
نویسندگان
Matthias Falk, Kyaw Tha Paw U, Sonia Wharton, Matt Schroeder,