Table 1. Ponderosa pine stands in central Oregon, USA referred to in the text. The CWD (coarse woody debris) is >10 cm dia and >1 m length. FWD (fine woody debris) is >6 mm and <10 cm. LF (litterfall) includes foliage and wood <1 cm dia. The 5-year average (2004–2008) LAI is 1.5 at the young plantation and 3.3 at the mature forest
Fig. 1.
The 5-year average weekly means of air temperature, vapour pressure deficit (VPD), soil water content (SWC) in the top 30 cm, and the 16-cm soil temperature for the mature pine (dashed) and the young plantation (solid). The sharp peaks in VPD are from extreme hot and dry events that survive the 5-year averaging.
Table 2. Estimates of mean annual gross ecosystem production (−GEP), ecosystem respiration (ER) and net ecosystem exchange (−NEE) (g C m−2 yr−1) based on eddy-covariance measurements. The uncertainty (one standard deviation) in an individual estimate of annual NEE due to gap-filling and flux partitioning is shown in parenthesis
Fig. 2.
Cumulative estimates of total ecosystem respiration (ER) for the mature pine (dashed) and the young plantation (solid) for the eddy-covariance method (heavy curves) and the chamber-based method (light curves).
Fig. 3.
Annual −NEE based on eddy-covariance and storage measurements and NEP based on biometric measurements for the mature pine (top) and the young plantation (middle). The bottom panel is the difference (mature minus young) between sites using NEE (solid) and NEP (dashed).
Table 3. Five-year average (2004–2008) quantities described in the text, except for the biological estimates at the young plantation which are 4-year averages (2004–2007)
Fig. 4.
The 5-year average monthly mean carbon fluxes for the mature pine (dashed) and young plantation (solid). Error bars denote ±1 standard error based on the interannual variability.
Fig. 5.
The 5-year average of the 30-day running mean GEP ratio (GEP at mature site divided by GEP at young plantation, dashed) and the ER ratio (solid).
Fig. 6.
The 5-year average monthly mean water fluxes (PPT from rain gauges and ET from eddy-covariance) for the mature pine (dashed) and young plantation (solid). Error bars denote ±1 standard error based on the interannual variability. The bottom panel is the difference (PPT–ET).
Fig. 7.
The average diel cycle of −GEP at the mature site (top) and the young plantation for 15 May to 15 June (solid) and 15 July to 15 August (dotted).
Fig. 8.
Interannual variability of −NEE at the mature site (dashed) and the young plantation (solid). Error bars denote the 90% confidence interval based on the uncertainty in the annual average due to gap-filling and flux partitioning.
Fig. 9.
The 5-year average seasonal pattern of daily inherent water-use efficiency (IWUE =−GEP×VPD/ET) for the mature pine (dashed) and young plantation (solid). The bottom panel is the actual water-use efficiency (WUE = −GEP/ET). Daily values have been smoothed with a 15-day running average for display.
Fig. 10.
The 2-year average (2004 and 2006) seasonal pattern of the normalised tree transpiration from sapflow measurements for the mature pine (dashed) and the young plantation (solid) for April–November.
