Differential responses of carbon and water vapor fluxes to climate among evergreen needleleaf forests in the USA

Table 3 Annual and seasonal (carbon uptake period, CUP) sums of net ecosystem CO₂ exchange (NEE_yr and NEE_CUP, g C m⁻²), gross primary production (GPP_yr and GPP_CUP, g C m⁻²), and evapotranspiration (ET_yr and ET_CUP, mm) with the standard deviation and coefficient of variation (CV) at ten forest sites. Ecosystem water use efficiency (EWUE, g C mm⁻¹ ET) was derived from the ratio between GPP and ET sums (EWUE_GPP) and between net ecosystem production (NEP = −NEE) and ET sums (EWUE_NEP) at annual (year) and seasonal (CUP) timescales

Site	NEE_yr	GPP_yr	ET_yr	EWUE_{GPP_yr}	EWUE_{NEP_yr}
Site	NEE_CUP	GPP_CUP	ET_CUP	EWUE_{GPP_CUP}	EWUE_{NEP_CUP}
US-SP1	−70 ± 127	968 ± 344	581 ± 48	1.67 ± 0.57	0.13 ± 0.23
US-SP1	−118 ± 19	661 ± 232	376 ± 44	1.74 ± 0.45	0.32 ± 0.09
US-DK3	−501 ± 176	2337 ± 319	829 ± 75	2.82 ± 0.31	0.60 ± 0.19
US-DK3	Same	Same	Same	Same	Same
US-NC2	−788 ± 304	2839 ± 282	1053 ± 107	2.81 ± 0.45	0.77 ± 0.35
US-NC2	Same	Same	Same	Same	Same
US-Ho1	−256 ± 49	1472 ± 108	367 ± 57	4.08 ± 0.62	0.72 ± 0.21
US-Ho1	−313 ± 44	1428 ± 98	343 ± 45	4.21 ± 0.54	0.93 ± 0.22
US-Ho2	−233 ± 39	1347 ± 94	361 ± 63	3.79 ± 0.44	0.67 ± 0.18
US-Ho2	−290 ± 37	1296 ± 86	339 ± 52	3.87 ± 0.42	0.88 ± 0.21
US-NR1	−34 ± 23	737 ± 99	572 ± 77	1.30 ± 0.18	0.06 ± 0.04
US-NR1	−159 ± 16	666 ± 84	391 ± 36	1.71 ± 0.21	0.41 ± 0.04
US-Fuf	−112 ± 70	937 ± 94	506 ± 46	1.85 ± 0.14	0.22 ± 0.14
US-Fuf	−188 ± 63	726 ± 89	371 ± 40	1.96 ± 0.13	0.50 ± 0.14
US-Me2	−497 ± 91	1335 ± 91	484 ± 40	2.78 ± 0.33	1.02 ± 0.16
US-Me2	−490 ± 74	1296 + 91	445 ± 39	2.93 ± 0.35	1.10 ± 0.13
US-Blo	−579 ± 276	1195 ± 257	681 ± 69	1.76 ± 0.37	0.83 ± 0.36
US-Blo	−578 ± 268	1141 ± 253	662 ± 67	1.72 ± 0.37	0.85 ± 0.36
US-Wrc	−66 ± 88	1370 ± 233	517 ± 71	2.71 ± 0.67	0.13 ± 0.15
US-Wrc	−182 ± 40	617 ± 75	230 ± 35	2.74 ± 0.54	0.82 ± 0.26
CV (%)	83	45	36	40	67
CV (%)	61	58	52	36	35

NEE, GPP, and ET sums and EWUE were determined for each year first, then averaged over the study period