Soil CO 2 Uptake in Deserts and Its Implications to the Groundwater Environment

Recent studies of soil carbon cycle in arid and semi-arid ecosystems demonstrated that there exists an abiotic CO2 absorption by saline-alkali soils (Aa) at desert ecosystems and suggested potential contributions of CO2 dissolution beneath deserts to the terrestrial ecosystems carbon balance. However, the overall importance of such soil CO2 uptake is still undetermined and its implications to the groundwater environment remain unaddressed. In this manuscript, a simple method is proposed for the direct computation of Aa from the total soil CO2 flux (Fa) as well as for the evaluation of Aa importance to Fa. An artificial soil-groundwater system was employed to investigate the implications to groundwater environment and it was found that soil CO2 uptake in deserts can contribute a possible influence on the evolution of the groundwater environment, providing that the absorbed CO2 largely remained in the soil-groundwater system.

Some recent studies attributed the abiotic processes to the effects of the soil water dynamics on subterranean carbon cycle and presented theoretical and experimental analyses based on the biogeochemical reactive transport modeling [21,22].This not only developed the methodology of the partition of F a into the biotic and abiotic components across some special environments, but also highlighted that the subterranean dissolution of CO 2 has been involved in the ecosystem carbon balance in deserts, and can even temporally dominate [7][8][9][10][11].However, soil CO 2 dissolution and effusion, as abiotic processes in deserts, are different from the considered processes in these previous studies.Especially in some experimental contrast, only the top few cm of the soil was considered.It became much more impressive after the abiotic CO 2 absorption (A a ) by the soil collected from a saline desert was directly observed after a minimizing-disturbance sterilization treatment on the soil [8].This demonstrated that there exists an abiotic CO 2 uptake by saline-alkali soils (A a ) at desert ecosystems and suggested a potential contribution of such soil CO 2 uptake to the ecosystem carbon balance in deserts [8,10].
There is strong evidence suggesting that A a can contribute significantly to F a and the net ecosystem carbon balance, but the overall importance of the soil CO 2 uptake to F a is still undetermined.Presently, both the field observations and the laboratory experiments are still limited on site scales.Because of the lack of large-scale experiments, the magnitude of such CO 2 uptake is still a matter of controversy.Some recent publications have further presented the laboratory data on the soil abiotic CO 2 absorption and the field data on the net CO 2 exchange in desert ecosystems [23,24], whereas it is still imperative to have a simple method for a direct computation of the abiotic soil CO 2 uptake from the total soil CO 2 flux and for quantifying its overall importance to F a .
The minimizing-disturbance sterilization treatment on soils has been widely recognized as an experimental method for separating A a [10].Since the significance of CO 2 dissolution and effusion as the abiotic processes has become much more impressive after the soil CO 2 uptake was directly observed after such a sterilization treatment on the soil [8,10], another subsequent unresolved issue is whether the beneath CO 2 dissolution has a non-negligible implication to the groundwater environment beneath deserts, providing that the dissolved and absorbed CO 2 largely remained in the soil-groundwater system.This certainly desires a further investigation but remains unaddressed.
This manuscript aims to design a simple method for a direct computation of the abiotic soil CO 2 uptake from the total soil CO 2 flux and proposed a simple approach to quantify its overall importance to F a .After a special treatment, F a is reconciled as a simple function of A a , which is implemented in two different approaches.In the experimental approach, all A a data are collected after the minimizing-disturbance sterilization treatment on the soils, while in the other semi-experimental approach, most of the A a data are directly calculated from a simple regressive model.The potential implications of A a and the beneath CO 2 dissolution to the groundwater environment are also preliminarily discussed.

Data Sources
Sampling data of soil CO 2 fluxes were collected from Xie et al. [8].The measurements were conducted in the Gurbantunggut Desert, which is located at hinterland of the Eurasian Continent (87 • 56 E, 44 • 17 N; elevation: 461 m), with an arid, windy climate (sunshine: 3079 h; precipitation: 144.7 mm; evapotranspiration: 2020 mm; radiation: 5439 MJ/m 2 ; velocity: 2.6 m/s).Note that two LI-8100s (LI-COR, Lincoln, Nebraska, NE, USA) have been employed for the valid comparison between the flux data measured at the sterilized and unsterilized samples.It should be noted that the soil was smashed, roots-sieved, air-dried and the many sinks and sources of CO 2 in the subsurface environment have been excluded.After sterilization, the net soil CO 2 fluxes were negative and the CO 2 exchange was abiotic.In order to highlight the soil CO 2 uptake, such abiotic exchange is hence defined as "soil abiotic CO 2 absorption" throughout this manuscript (Figure 1).Consequently, the variations of F a were largely determined by A a and the soil microbial respiration (R m ).
With the purpose of a preliminary discussion on the potential implications of the beneath CO 2 dissolution to the groundwater environment, an artificial soil-groundwater system was employed and the groundwater were sampled with six replications (Figure 2).The groundwater pH and the concentration of dissolved inorganic carbon (DIC) in the artificial soil-groundwater system were measured, where the concentration of DIC (symbolized as (DIC) was defined as the sum of the concentration of the dissolved carbonate ion and bicarbonate ion.

Modeling Approach
Neglecting Aa, it is well-known that Fa can be formulated as an exponential function of the soil surface temperature or the ambient air temperature [19]: where Fa20 is measured Fa at 20 °C, TS is the soil temperature (here it is measured at 0-10 cm), and Q10 is the relative change in Fa with 10 °C increases.Rm is formulated as in [20]: where Rm20 is the measured value of Rm at 20 °C.Taking into account Aa, Fa is reconciled as,

Modeling Approach
Neglecting Aa, it is well-known that Fa can be formulated as an exponential function of the soil surface temperature or the ambient air temperature [19]: where Fa20 is measured Fa at 20 °C, TS is the soil temperature (here it is measured at 0-10 cm), and Q10 is the relative change in Fa with 10 °C increases.Rm is formulated as in [20]: where Rm20 is the measured value of Rm at 20 °C.Taking into account Aa, Fa is reconciled as,

Modeling Approach
Neglecting A a , it is well-known that F a can be formulated as an exponential function of the soil surface temperature or the ambient air temperature [19]: where F a20 is measured F a at 20 • C, T S is the soil temperature (here it is measured at 0-10 cm), and Q 10 is the relative change in F a with 10 • C increases.R m is formulated as in [20]: where R m20 is the measured value of R m at 20 The experimental method separates A a by the sterilization treatment on the soils and hence R m20 can be estimated as follows: R m20 = F a20 − A a20 (4) where A a20 are measured A a at 20 • C. Substituting Equation (2) into Equation ( 4), R m is reconciled as: Correspondingly, F a can be finally reconciled as: Unfortunately, extensive time is required during the minimizing-disturbance sterilization treatment on the soil.At large scales, it is necessary to couple with other methodologies.Development of a semi-experimental method for the rough partition of A a is thus necessary.
Similar to semi-experimental approaches for the partition of the biotic components of F a [12], the relationship between A a and F a could be assumed to be represented by a simple linear regressive model and written as: where β 0 and β 1 are determined by the contributions of A a to F a .Under this assumption, R m is reconciled as: and correspondingly R m10 = (1 By Equation ( 2), the Q 10 value for R m can be estimated by Combining Equations ( 8) and ( 10), the soil CO 2 flux could be finally reconciled as The parameters β 0 and β 1 can be estimated by Equation ( 7) after a few experiments and a large magnitude of time will be saved in the partition of A a .
Regarding the first approach, the relationship between the groundwater pH and (DIC) are analyzed by utilizing an exponentially regressive model: where λ 0 and λ 1 are determined by the contributions of (DIC) to the groundwater pH.

Separated Biotic and Abiotic Components of Soil CO 2 Fluxes
The aforementioned parameters of β 0 and β 1 are estimated using the measured values of A a and F a on two clear days in two typical desert ecosystems, saline desert and oasis farmland (Figure 3).
The aforementioned parameters of β0 and β1 are estimated using the measured values of Aa and Fa on two clear days in two typical desert ecosystems, saline desert and oasis farmland (Figure 3).The estimated parameters of β0 and β1 are then applied to the semi-experimental separation of Aa at the corresponding ecosystems in a drought period of one growing season in 2006, taking into account their difference for different ecosystems (the estimated β0 and β1 from saline desert are also applied to its neighbor abandoned farmland, as provided in Table 1).

Study Sites
Parameters Applied in Semi-Experimental Method Saline desert β 0 = 0.5284 It is obvious that Aa separated in both the experimental and semi-experimental approaches acts as a CO2 sink.Aa separated into two approaches varies in a similar pattern during the considered drought period.Through comparison with the total soil CO2 flux Fa, it was found that most Fa data are positive.This implies that the other flux component of Fa, the microbial soil respiration Rm, plays a dominant role within this period (Figure 4)   The estimated parameters of β 0 and β 1 are then applied to the semi-experimental separation of A a at the corresponding ecosystems in a drought period of one growing season in 2006, taking into account their difference for different ecosystems (the estimated β 0 and β 1 from saline desert are also applied to its neighbor abandoned farmland, as provided in Table 1).

Study Sites Parameters Applied in Semi-Experimental Method
Saline desert β 0 = 0.5284 It is obvious that A a separated in both the experimental and semi-experimental approaches acts as a CO 2 sink.A a separated into two approaches varies in a similar pattern during the considered drought period.Through comparison with the total soil CO 2 flux F a , it was found that most F a data are positive.This implies that the other flux component of F a , the microbial soil respiration R m , plays a dominant role within this period (Figure 4) The estimated parameters of β0 and β1 are then applied to the semi-experimental separation of Aa at the corresponding ecosystems in a drought period of one growing season in 2006, taking into account their difference for different ecosystems (the estimated β0 and β1 from saline desert are also applied to its neighbor abandoned farmland, as provided in Table 1).

Study Sites
Parameters Applied in Semi-Experimental Method Saline desert β 0 = 0.5284 It is obvious that Aa separated in both the experimental and semi-experimental approaches acts as a CO2 sink.Aa separated into two approaches varies in a similar pattern during the considered drought period.Through comparison with the total soil CO2 flux Fa, it was found that most Fa data are positive.This implies that the other flux component of Fa, the microbial soil respiration Rm, plays a dominant role within this period (Figure 4) Considering that β0 and β1 are determined by the contributions of Aa to Fa, they might be very different in various ecosystems (Aa is not very different, but Fa can be very different).Choosing soil sites for the few sampled experiments should be done cautiously.
The values of Q10 for the microbial soil respiration Rm might also be different in various ecosystems.From the visualization of the separated Rm in considered drought period by a  Considering that β 0 and β 1 are determined by the contributions of A a to F a , they might be very different in various ecosystems (A a is not very different, but F a can be very different).Choosing soil sites for the few sampled experiments should be done cautiously.
The values of Q 10 for the microbial soil respiration R m might also be different in various ecosystems.From the visualization of the separated R m in considered drought period by a continuous Water 2016, 8, 379 6 of 12 curve, the gradient of R m in some sites and sampling days might not be evident.For to this reason, only the separated results of R m on nine sampled days are presented here and three kinds of ecosystems are selected for the comparison, the saline desert, abandoned farmland and oasis farmland.It could also facilitate the valid and explicit comparison between the separated results of R m from the experimental method and the semi-experimental method.Obviously, the separated R m in the semi-experimental and experimental approaches show similar patterns.The diurnal dynamics on nine sampled days also reveal a duplicated variability (Figures 5 and 6).
Water 2016, 8, 379 6 of 12 continuous curve, the gradient of Rm in some sites and sampling days might not be evident.For to this reason, only the separated results of Rm on nine sampled days are presented here and three kinds of ecosystems are selected for the comparison, the saline desert, abandoned farmland and oasis farmland.It could also facilitate the valid and explicit comparison between the separated results of Rm from the experimental method and the semi-experimental method.Obviously, the separated Rm in the semi-experimental and experimental approaches show similar patterns.The diurnal dynamics on nine sampled days also reveal a duplicated variability (Figures 5 and 6).The separated results of Rm in the former two ecosystems are almost the same (Table 2), which are all different with the oasis farmland.This might be the reason that the soil microbial activity in the saline desert is very different to that in oasis farmland.
The separated Aa from the semi-experimental approach represents about 80% of that from the experimental approach, which indicates a reliable cross validation (Figure 7).In fact, the experimental method should still be used with much caution since it indicates a large magnitude of carbon sink in the most barren ecosystems [10,14].Thus, the cross validations between these two methods are necessary.Water 2016, 8, 379 6 of 12 continuous curve, the gradient of Rm in some sites and sampling days might not be evident.For to this reason, only the separated results of Rm on nine sampled days are presented here and three kinds of ecosystems are selected for the comparison, the saline desert, abandoned farmland and oasis farmland.It could also facilitate the valid and explicit comparison between the separated results of Rm from the experimental method and the semi-experimental method.Obviously, the separated Rm in the semi-experimental and experimental approaches show similar patterns.The diurnal dynamics on nine sampled days also reveal a duplicated variability (Figures 5 and 6).The separated results of Rm in the former two ecosystems are almost the same (Table 2), which are all different with the oasis farmland.This might be the reason that the soil microbial activity in the saline desert is very different to that in oasis farmland.
The separated Aa from the semi-experimental approach represents about 80% of that from the experimental approach, which indicates a reliable cross validation (Figure 7).In fact, the experimental method should still be used with much caution since it indicates a large magnitude of carbon sink in the most barren ecosystems [10,14].Thus, the cross validations between these two methods are necessary.The separated results of R m in the former two ecosystems are almost the same (Table 2), which are all different with the oasis farmland.This might be the reason that the soil microbial activity in the saline desert is very different to that in oasis farmland.
The separated A a from the semi-experimental approach represents about 80% of that from the experimental approach, which indicates a reliable cross validation (Figure 7).In fact, the experimental method should still be used with much caution since it indicates a large magnitude of carbon sink in the most barren ecosystems [10,14].Thus, the cross validations between these two methods are necessary.Employing the estimated β0 and β1 in Equation ( 10) and fitted Q10 provided in Table 2, the separated Rm by the semi-experimental method explain well the variability of separated Rm by the experimental method (Figure 8).Both semi-experimental and experimental methods reconcile Fa as a direct sum of Aa and Rm, rendering the cross validation of reconciled Fa using these two methods necessary.In Figure 9, it is also found that Fa reconciled by Equation ( 11) using the semi-experimental approach almost coincides with that reconciled by Equation ( 6) in the experimental approach.The aforementioned results of cross validation also show that the semi-experimental separations of Rm and Aa proposed in Section 2 are both feasible and reliable (Table 3).Employing the estimated β 0 and β 1 in Equation ( 10) and fitted Q 10 provided in Table 2, the separated R m by the semi-experimental method explain well the variability of separated R m by the experimental method (Figure 8).Both semi-experimental and experimental methods reconcile F a as a direct sum of A a and R m , rendering the cross validation of reconciled F a using these two methods necessary.In Figure 9, it is also found that F a reconciled by Equation ( 11) using the semi-experimental approach almost coincides with that reconciled by Equation ( 6) in the experimental approach.The aforementioned results of cross validation also show that the semi-experimental separations of R m and A a proposed in Section 2 are both feasible and reliable (Table 3).Employing the estimated β0 and β1 in Equation (10) and fitted Q10 provided in Table 2, the separated Rm by the semi-experimental method explain well the variability of separated Rm by the experimental method (Figure 8).Both semi-experimental and experimental methods reconcile Fa as a direct sum of Aa and Rm, rendering the cross validation of reconciled Fa using these two methods necessary.In Figure 9, it is also found that Fa reconciled by Equation ( 11) using the semi-experimental approach almost coincides with that reconciled by Equation ( 6) in the experimental approach.The aforementioned results of cross validation also show that the semi-experimental separations of Rm and Aa proposed in Section 2 are both feasible and reliable (Table 3).

Implications of Soil CO2 Uptake to the Groundwater Environment
Although soil CO2 uptake in deserts has been investigated in many previous studies, its potential influences on the groundwater environment remain unaddressed [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39].This is partially due to the lack of a simple method for the separation and quantification of such CO2 uptake.This study presents a simple yet efficient method for partitioning CO2 influxes to and efflux from bare saline-alkali soils, implying a time to consider the implications of such CO2 uptake beneath deserts to the groundwater environment.An unresolved issue, where the absorbed CO2 has gone, still remains.Most studies assumed that these absorbed CO2 are partially dissolved in the soil-groundwater system.However, the magnitude of the beneath CO2 dissolution remains undetermined [25][26][27][28][29][30].
Furthermore, the experimental partition method is still desired for further improvement.Based on some recent studies, there exists little difference between abiotic soil CO2 influx and efflux when excluding the role of groundwater and soil is left to absorb/release CO2 naturally [28].The difference might be attributed to the extent of the sterilization treatment on the soil and the existence of some soil microbial respiration (Rm), or the interaction between the existing Rm and Aa.Future studies must keep a most cautious mind in extending the results from the laboratory experiments to field research.In reality, the conditions are much more complex and the additional confounding factors for many flux components exist and might interact with each other.
It has been widely recognized that the overall magnitude of CO2 dissolution beneath deserts and its contributions to the ecosystem carbon balance can be huge [30][31][32][33][34][35][36][37][38][39], but its effect on the local environment are seldom reported.As a first attempt to analyze the implications of the soil CO2 uptake to the groundwater environment, the present study simply assumes that the absorbed CO2 has been largely dissolved in the soil-groundwater system beneath the deserts.Under this assumption, an artificial soil-groundwater system has been incubated for a long period in the laboratory.Collected data at the first stage confirm that the implications to the water environment should be taken into account (Figure 10).Although soil CO 2 uptake in deserts has been investigated in many previous studies, its potential influences on the groundwater environment remain unaddressed [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39].This is partially due to the lack of a simple method for the separation and quantification of such CO 2 uptake.This study presents a simple yet efficient method for partitioning CO 2 influxes to and efflux from bare saline-alkali soils, implying a time to consider the implications of such CO 2 uptake beneath deserts to the groundwater environment.An unresolved issue, where the absorbed CO 2 has gone, still remains.Most studies assumed that these absorbed CO 2 are partially dissolved in the soil-groundwater system.However, the magnitude of the beneath CO 2 dissolution remains undetermined [25][26][27][28][29][30].
Furthermore, the experimental partition method is still desired for further improvement.Based on some recent studies, there exists little difference between abiotic soil CO 2 influx and efflux when excluding the role of groundwater and soil is left to absorb/release CO 2 naturally [28].The difference might be attributed to the extent of the sterilization treatment on the soil and the existence of some soil microbial respiration (R m ), or the interaction between the existing R m and A a .Future studies must keep a most cautious mind in extending the results from the laboratory experiments to field research.In reality, the conditions are much more complex and the additional confounding factors for many flux components exist and might interact with each other.
It has been widely recognized that the overall magnitude of CO 2 dissolution beneath deserts and its contributions to the ecosystem carbon balance can be huge [30][31][32][33][34][35][36][37][38][39], but its effect on the local environment are seldom reported.As a first attempt to analyze the implications of the soil CO 2 uptake to the groundwater environment, the present study simply assumes that the absorbed CO 2 has been largely dissolved in the soil-groundwater system beneath the deserts.Under this assumption, an artificial soil-groundwater system has been incubated for a long period in the laboratory.Collected data at the first stage confirm that the implications to the water environment should be taken into account (Figure 10).Since the potential contributions of these abiotic components to the total soil CO2 fluxes were non-negligible, the implication of the biotic CO2 effluxes and abiotic CO2 influxes to the soil-groundwater environment cycle is a subsequent problem.Despite the recent studies of soil carbon cycle in the desert ecosystems and the biogeochemical investigations in the arid ecosystems [40][41][42][43][44][45][46][47][48][49], the dynamics of beneath CO2 dissolution [7,10] is still not well-understood.Furthermore, even the mechanisms of subterranean abiotic processes are still not wholly known.It is worth noting that the groundwater pH is essentially significant for the local water environment and has attracted a wide attention [50][51][52][53][54][55][56][57][58][59][60].Attaining a reliable quantification for the contributions of soil CO2 uptake to the groundwater environment remains one major challenge and hence should be a research priority.
Because the mechanisms for the abiotic CO2 absorption and the overall magnitude of the soil CO2 uptake are still not well-understood, there are still considerable uncertainties in more explicit analyses of the contributions of such soil CO2 uptake to the groundwater environment [8,10,14].Additionally, the data required by the present experimental method can only be collected from the top few cm of the soil.The whole atmospheric exchange of CO2 requires some further investigations towards better and more suitable experimental and non-experimental methodologies.

Conclusions
This study presented a simple yet efficient method to work out the magnitude of soil abiotic CO2 absorption in deserts from the data set of soil CO2 fluxes, along with a first approach to illustrate its potential role in influencing environments in an artificial soil-groundwater system.The first approach highlighted significant events where an evident variation of the groundwater pH, provided that the absorbed CO2 largely remained in the soil-groundwater system.Considering the CO2 sink size across different environments remains unknown, there are still considerable uncertainties and further investigations are necessary.
Since the potential contributions of these abiotic components to the total soil CO 2 fluxes were non-negligible, the implication of the biotic CO 2 effluxes and abiotic CO 2 influxes to the soil-groundwater environment cycle is a subsequent problem.Despite the recent studies of soil carbon cycle in the desert ecosystems and the biogeochemical investigations in the arid ecosystems [40][41][42][43][44][45][46][47][48][49], the dynamics of beneath CO 2 dissolution [7,10] is still not well-understood.Furthermore, even the mechanisms of subterranean abiotic processes are still not wholly known.It is worth noting that the groundwater pH is essentially significant for the local water environment and has attracted a wide attention [50][51][52][53][54][55][56][57][58][59][60].Attaining a reliable quantification for the contributions of soil CO 2 uptake to the groundwater environment remains one major challenge and hence should be a research priority.
Because the mechanisms for the abiotic CO 2 absorption and the overall magnitude of the soil CO 2 uptake are still not well-understood, there are still considerable uncertainties in more explicit analyses of the contributions of such soil CO 2 uptake to the groundwater environment [8,10,14].Additionally, the data required by the present experimental method can only be collected from the top few cm of the soil.The whole atmospheric exchange of CO 2 requires some further investigations towards better and more suitable experimental and non-experimental methodologies.

Conclusions
This study presented a simple yet efficient method to work out the magnitude of soil abiotic CO 2 absorption in deserts from the data set of soil CO 2 fluxes, along with a first approach to illustrate its potential role in influencing environments in an artificial soil-groundwater system.The first approach highlighted significant events where an evident variation of the groundwater pH, provided that the absorbed CO 2 largely remained in the soil-groundwater system.Considering the CO 2 sink size across different environments remains unknown, there are still considerable uncertainties and further investigations are necessary.

Figure 2 .
Figure 2. A diagram of the artificial soil-groundwater system.The samples were collected from #1, with 6 replications.

Figure 2 .
Figure 2. A diagram of the artificial soil-groundwater system.The samples were collected from #1, with 6 replications.

Figure 2 .
Figure 2. A diagram of the artificial soil-groundwater system.The samples were collected from #1, with 6 replications.

Figure 4 .
Figure 4. Isolated A a by experimental/semi-experimental method.

Figure 7 .
Figure 7. Reliability of semi-experimental partition method (the green line is the linear regression line determined by the observed values and the simulated values) utilizing a linear regression curve (the green line).The diagonal blue line is taken as a reference.

Figure 8 .
Figure 8. Cross validation of isolated Rm by two methods.

1 ]Figure 7 .
Figure 7. Reliability of semi-experimental partition method (the green line is the linear regression line determined by the observed values and the simulated values) utilizing a linear regression curve (the green line).The diagonal blue line is taken as a reference.

Figure 7 .
Figure 7. Reliability of semi-experimental partition method (the green line is the linear regression line determined by the observed values and the simulated values) utilizing a linear regression curve (the green line).The diagonal blue line is taken as a reference.

Figure 8 .
Figure 8. Cross validation of isolated Rm by two methods.

1 ]Figure 8 .
Figure 8. Cross validation of isolated R m by two methods.

Figure 9 .
Figure 9. Cross validation of reconciled Fa by two methods, utilizing a linear regression curve (the green line).The diagonal blue line is taken as a reference.

2 s - 1 ]Figure 9 .
Figure 9. Cross validation of reconciled F a by two methods, utilizing a linear regression curve (the green line).The diagonal blue line is taken as a reference.

Figure 10 .
Figure 10.The relationship between the groundwater pH and the concentration of dissolved inorganic carbon (DIC) in the artificial soil-groundwater system.

Table 1 .
Suitable parameters for the isolation of Aa.

Table 1 .
Suitable parameters for the isolation of A a .

Table 1 .
Suitable parameters for the isolation of Aa.

Table 2 .
Q 10 values for isolated R m by two methods.

Table 2 .
Q10 values for isolated Rm by two methods.

Table 2 .
Q10 values for isolated Rm by two methods.

Table 3 .
Fitted relationships between isolated components by two methods.

Table 3 .
Fitted relationships between isolated components by two methods.