## 4 Discussion
Over 100,000 individual measurements of soil respiration across 23 experimental studies, five different forest types and spanning more than 25, years were conducted with cross-cutting footprints for the US-Ha1 EMS tower data analyzed herein. For example, the relationship between soil CO\({}_{2}\) efflux (R\({}_{\rm s}\)) determined by individual chamber measurements, and total ecosystem respiration, R\({}_{e}\), for the US-Ha1 NEE EC record analyzed in this study, covering shared tower footprints, shows that R\({}_{\rm s}\)/R\({}_{e}\) varied from 0.49 to 0.88 (Figure 1C). The large variation emphasizes the complexity of the biospheric system and seasonal carbon dynamics that challenge model development and monitoring applications. Figure 1C shows that soil chamber measurements (R\({}_{\rm s}\)) and EC measurements (R\({}_{\rm e}\)) capture the perturbation of the 2010 US-Ha1 environment resulting in a severe loss of forest carbon asset value with an uneven recovery spanning the period up to 2019. In forest carbon trading practice, a landowner employing EC may also choose to rely upon repeat soil chamber measurements as feasible and cost-effective to improve understanding of the project soil carbon and financial dynamics. In addition to soil respiration chambers, soil organic carbon measurements were made across the US-Ha1 site footprint [6; 40] to characterize soil carbon pools. Results for soil carbon pools revealed negligible change in net accrual of soil organic carbon for measurements of % soil carbon and soil bulk density over the period 1992-2013 [6; 40]. The US-Ha1 total soil carbon in the top 15 cm of the mineral soil was 6072 (\(\pm\)1509), and, 6021 (\(\pm\)1238) gC m\({}^{-2}\) for 1992 and 2013, respectively (3; Table S11). The lack of temporal resolution for soil carbon changes in the soil column and the difficulty of sampling for detection of small changes in a relatively large and heterogeneous soil carbon pool are unlikely to yield cost-effective, meaningful, and verifiable data for commercial products, although this approach is commonly employed [23; 24]. For example, detection of a significant change (\(p\) < 0.05) in soil carbon of \(\sim\)20 gC m\({}^{-2}\) is estimated to require \(\sim\)164,194 samples for the US-Ha1 soil sampling study surrounding the hemlock dominated (HEM) tower site (3; Figure S6). In contrast, as described previously, NEE and \(R_{cco}\) changes and trends in the flux and the flow of CO\({}_{2}\) and isotopocules into and out of the soil matrix establish contemporary and historic perspectives to guide commercial development and conservative practice for soil carbon sequestration and monetization. NEE integrates complex diurnal and seasonal factors affecting soil CO\({}_{2}\) efflux from the soil column extending from the surface to \(\sim\)1 m in depth including turnover of differing carbon pools, diffusion, short- and long-term changes in temperature, microbial metabolism, root activity and abiotic factors [6]. The US-Ha1 research experiment and similar long-term studies are needed to create and test mitigation and financial approaches to manage climate change with economic, social, and planetary benefits. The \({}^{ISO}\)NEE products defined for \({}^{13}\)C\({}^{16}\)O\({}_{2}\) and \({}^{18}\)O\({}^{12}\)C\({}^{16}\)O have the potential to redefine carbon trading dynamics for CO\({}_{2}\) measurement derivatives. The carbon and oxygen isotopic species as singular or mixed isotopic masses can be quantified and, as for \({}^{12}\)CO\({}_{2}\), be financialized according to mass across project temporal and spatial domains. The market value of these isotopocules have not been priced but are reasonably expected to trade in multiples of pricing for non-isotopic counterparts. Enhanced data for the partitioning of NEE, not currently available in a commercial forest carbon protocol, will benefit investors and landowners in management of projects in terms of forest operations, financial planning, and carbon isotopic flux trading.