US-NC1 did not have a sim- using empirical relationships with temperature and moisture ilar system as the canopy was open and all the flux was using both the automatic and survey chamber measurements, expected to be accounted for by turbulent exchange. The weighting the collars in proportion to stand-wide area distri- eddy covariance systems were mounted at 6 m at US-NC1 bution of distance to the nearest tree Noormets et al. The distance from the instru- et al. US-NC2 system and survey chamber.
Substrate temperature was surrounded by stands of similar age and species compo- was measured with HI thermometer and substrate sition, whereas US-NC1 bordered with a similar stand in moisture was assessed on qualitative scale based on visual the east, but was surrounded by taller mature pine stands appearance and time since last rainfall. The level of decay of in the other directions. The 30 min mean fluxes of CO2 were the substrate was evaluated periodically according to Harmon computed as the covariance of vertical wind speed and the et al.
However, given the final sample size per decay class et al. As the result, the esti- Delft, the Netherlands , and precipitation P, TE, Camp- mates of base respiration and temperature sensitivity were bell Scientific Inc.
The PAR measure- poorly defined in this decay class. Soil temperature CO2 efflux from CWD were regressed with the temperature of Ts was measured at depths of 5 and 10 cm with CS CSI CWD, grouped by different decay class, and scaled up using a temperature probe, soil volumetric water content VWC was non-linear regression model based on estimated CWD temper- averaged through the top 30 cm using a vertically inserted ature, which in turn was estimated based on the relationship CS time domain reflectometer CSI , and the depth of GWT between CWD and soil temperature over a 4 year period.
Following a harvest, there would be a For years when RCWD measurements were not conducted large pool of coarse roots that would gradually die and , , , the fluxes were estimated using the temper- become a substrate for microbial decomposition. At one ature response model established for Given that from extreme, one could speculate that most of SR would originate July of through June of the sites experienced severe from heterotrophic processes.
However, this scenario did not drought Noormets et al. The moister years than that for As the vegetation and new observed CO2 production, and ii fragmentation, which has root systems developed, RHSoil probably shifted closer to been estimated to be comparable in magnitude to the rate of RHSoil-BL.
Sometimes, fragmenta- the difference between GEP and biometric estimates of net pri- tion may start with a lag of a few years see Harmon et al. Missing from these estimates is the explicit accounting for the decay of harvest residue or slash, which consists of foliage, Harvest losses bark, branches and small stems. In managed forests, the C cycle is open and a significant frac- tion of assimilated carbon leaves the site at harvest.
The exact Data processing and gapfilling amount of removal depends on species, and the market demand for different wood products, which, in turn, may vary Gaps in eddy covariance fluxes and soil respiration were filled regionally and in time. In February, , the tower at US- in similar climate Clark et al. Clearly, gapfilling model estimates fitted to the rest of the year. The closing the carbon balance depends on the correct estimation difference between these estimates was 65 g C m 2 yr 1.
Even though the estimates final products, with the rest being lost in milling and transpor- from the two preferred methods were similar, it has been tation Ingerson, Biomass Partitioning respiration Following the clear-cut harvest of a mixed native hard- Partitioning ecosystem respiration ER to above- and below- wood stand in , site US-NC1 was estimated to have ground heterotrophic RHSoil and autotrophic RA compo- approximately — g C m 2 in CWD and nearly nents was based on several assumptions.
We hypothesized as much in dead fine and coarse roots Table 1. The ground cover removal of stemwood Clark et al. Pine photosynthesis was not directly mea- New 2 year old seedlings were planted in , but the sured, but pine leaf mass contributed only 0. The declines in GEP in and had reached levels comparable to the mid-rotation are attributable to severe droughts during these stand US-NC2, with about g C m 2 in foliage bio- years Fig.
The canopy still had a significant understory The drought years prolonged the postharvest component, particularly in the first part of the growing source phase and suppressed carbon uptake over the season when water availability was higher, discussed in more detail elsewhere Domec et al. The harvesting and subsequent site preparation destroyed the forest floor in the young stand, and partly mixed it with the topsoil. Forest floor measure- ments resumed only 7 years after harvest, by which time forest floor had recovered to about half of that in the mid-rotation stand Table 1.
In the mid-rotation stand, there was a slight increasing trend in forest floor mass Table 1 , but it seemed sensitive to interannual variability in weather data not shown. There was a b distinct cycle of alternating phases of forest floor accu- mulation and loss, but among years, the timing of these phases shifted significantly, with the timing of leaf fall affected both by natural processes of aging and storms data not shown.
Ecosystem-level CO2 exchange US-NC1 was a strong source of C to the atmosphere immediately following the harvest, owing to the har- vest residue, large pool of dead roots and disturbance Fig. The rate of decomposition of the dead surements, the black dashed line marks cumulative carbon organic matter slowed in subsequent years, but some of balance, and the gray line is a rectangular hyperbola fitted to the decline in SR was compensated for by increasing non-drought-year data.
The main changes whereas without the drought, the transition from C in the site-level losses were driven by the decrease in source to sink may have occurred a year earlier. CWD mass and areal coverage, whereas the CO2 evolu- However, a detailed evaluation of drought effects and tion rate per unit CWD area changed much less other interannual variability separate from age-related Fig.
Therefore, the temperature-adjusted decay- changes is beyond the scope of the current study. The class-specific decay rates were applied throughout the average rate of annual sequestration at the mid-rotation study period within each site. The mass-based esti- stand US-NC2 was g C m 2 yr 1, but individual mates of RCWD were negative in some years, and were years varied widely, ranging from to g attributed to i measurement uncertainty in years 3 C m 2 yr 1.
The gapfilling uncer- respectively Fig. As hypothe- sized, the methods diverged more in the young than a the mid-rotation stand. The interannual variability was greater using the biometric estimate RA1 , possibly due to temporal lags between assimila- tion and growth, and interannual variability in alloca- tion to storage and root growth.
Heterotrophic soil respiration was estimated as the residual Eqn 3c and could be used to assess the b Fig. The fluxes are presented as estimates of CO2 emis- two loblolly pine stands. Years 1—5 come from US-NC1, sions. See Methods for further details and assumptions. Given that the biometric and statistical estimates of RHsoil are independent of SR measure- ments, their ratio offers an assessment of internal consistency. However, in the early rotation stand, both data-based estimates of RHsoil diverged significantly from the global model and while they were consistent in 3 years out of the 5 year observation period, during severe droughts, the biometric estimates exceed SR, Fig.
However, the temporal pine plantations. Years 1—5 come from US-NC1, years 13—17 dynamic was very similar with the statistical method. RA is the average of biometric and global esti- Overall, even by the 5th year of measurements, the mates RA1 and RA2, see Methods , RHSoil is estimated as the heterotrophic component of soil CO2 efflux remained residual.
On one hand, there would have been more logging slash and root biomass Table 1. Although we re-checked the allometric equations for different ages of loblolly pine and are confident about the productivity estimates of different pools, we are less sure about harvest removal, and other related changes. Even when trees died, their size was well below the CWD threshold. Given the proportionality of this estimate to standing biomass and the aggrading nature of the stand, the 5 year mean CWD production rate was esti- mated at 7—12 g C m 2 yr 1 based on the snag produc- tion and fall-over rates, and about 30 g m 2 yr 1 based Fig.
Based on by priming soil C mineralization Smolander et al. Although the difference between the mass loss pine plantation at harvest age, and ii a mixed bottom- and flux upscaling estimates of RCWD was smaller than land hardwood forest similar to what was at US-NC1 the expected uncertainty of either method, the fact that prior to planting, we estimated that aboveground upscaled chamber fluxes were consistently lower than woody harvest residue was or g C m 2, CWD mass loss could also be attributable to three respectively, and the total dead organic matter pro- methodological biases.
First, CO2 emissions from the duced in a harvest was or g C m 2, respec- ends of decaying CWD exceed the lateral flux rates tively Table 1. As we measured RCWD in be an overestimate as it should be smaller than the the traditional way, with collars mounted on the slash pool. Second, it is also possible that our sampling, removed from the site.
This could have been exaggerated Discussion by presumably greater fragmentation of these decay classes. And finally, it is possible that fragmentation Uncertainties may have been greater than the assumed equivalence This study was an attempt to evaluate rotation cycle car- with mineralization as the CWD was disturbed during bon balance using an unreplicated pair of loblolly pine the harvest and subsequent site preparation. The stands.
As such, it is vulnerable to the weaknesses typi- importance of photodegradation in the current study cally associated with chronosequence studies, including was discounted on account of reports of it being limited site matching, representativeness, and changes in envi- in mesic environments Smith et al. Yet, if it did ronmental conditions and management practices over occur, photodegradation would have inflated the time Yanai et al.
In the mates in the first few years following the harvest. The current study, the early-rotation site US-NC1 had a rotation cycle carbon balance is also affected by higher site index than the mid-rotation site US-NC2 88 assumptions made in extrapolations of various pool and 66, respectively.
As a result, the combination of sizes to the time of harvest. We used linear extrapola- sites as in this study may represent net ecosystem car- tion of all major biomass pools, based on the consistent bon balance intermediate to those with internally con- trends across both stands Table 1. This may be coun- sistent site indices as the rate of recovery may currently ter-intuitive, as there are limits to leaf area and fine root have been overestimated, whereas the fluxes at later biomass, but given the observed trends, saturation stages may have been underestimated.
It remains points could not be detected. In case the leaf and fine unclear whether the difference in site indices is primar- roots pools and respective detritus inputs at harvest ily due to soil properties, the 25 ppm increase in atmo- are overestimated, the extent of soil C loss would be spheric CO2 between the two harvests, or the fact that underestimated.
Yet, C transformations tion pathways leaching, CH4, and VOC emissions , the in the early years of recovery from stand-replacing dis- amount and decomposition dynamics of fine logging turbance need to be better constrained, particularly as slash, and photodegradation.
However, these fluxes are they have disproportionate influence on long-term C assumed to be minor in their contribution to total site C balance of the stand.
On the other hand, even though the decomposition of fine Biomass woody debris may be faster than that of CWD Mattson et al. Assuming litter additions and turnover Methods. In addition, we re-checked the carbon con- rates similar to the mid-rotation stand, the 7 year time- tent of hardwood species, and switched from hard- point fit on the same trend-line that characterizes the wood allometric equations based on diameter at breast change in that stand, consistent with earlier observa- height DBH and height to those based only on DBH.
For integrated rotation cycle estimates for American holly Ilex opaca and lower carbon balance, the dynamics of forest floor per se are estimates for red maple Acer rubrum , compared with not important if it recovers, but the effect that this initial estimates. However, most of the changes in total disturbance has on mineral soil carbon cycling and new above- and belowground biomass pools were attribut- carbon transfer from above- to belowground pools able to pine biomass, because of the overwhelming could be important.
For example, microbial biomass predominance of this species over hardwoods. The integrated Table 1. However, if we consider the vegetation that CO2 exchange over 25 year rotation cycle area under was at US-NC1 prior to this planting i.
Although we did not measure ecosystem biomass at maturity was The harvest residue generated by clearcutting each mass Table 1 suggest that the NPP of this forest must of these forests would be 58 or 33 t C ha 1, respec- be about fivefold lower.
The esti- removal rate for pines Clark et al. With fine logging residue that was While the removal and the harvest-related dynamics of this pool may alter car- subsequent recovery of leaf area after harvest resulted bon transfer from aboveground to belowground pools.
Yet, the contribution of different decline of forest floor over a 20 year period following components changed significantly Figs 1—5 as dis- harvest. Although some hypotheses have been put for- cussed below. Overall, the dynamics and mechanisms ward that might explain the long-lasting impact of of flux recovery were strongly affected by the rapid col- harvesting Aber et al. However, some loss of forest floor is stand but also to large extremes in precipitation expected, probably enhanced by the mixing of forest Domec et al.
The effect of floor with mineral soil Yanai et al. In this study, the year drought in Noormets et al. We did observe the hypothesized where mixing of slash with mineral soil and subsequent increase in RH, both in above- and below-ground, but bedding destroyed a clearly defined forest floor. This is likely attributable to the in Canada Howard et al.
However, given the relatively high fine root ratory Mattson et al. The similarity of inputs to and losses from the CWD pool It is unknown effect of harvest, yet both inputs to and outputs from this whether branchfall, which was threefold greater than pool remain poorly quantified in relation to other fluxes. CWD input, contributed more or less to the soil C pool. Key terms for understanding the water cycle are. A 4d book cycles of nature little raindrop nature stories water to extend this activity create your own water cycle bag experiment it s a super simple science experiment that will show how water transforms.
Water precipitation cycle condensation evaporation clouds the sun temperature to name a few. The water cycle worksheets provide experiements and hands on ideas to help children learn about the water cycle also known as the hydrologic cycle. You may use the word cards for a matching game or word wall. A book about the water cycle.
Free printable grade 5 math worksheets. It consists of the one page worksheet and an answer key. Worksheets math grade 5. Both are part of the water cycle. In this science worksheet your child determines whether statements about the water cycle are true. Evaporation is the process of changing from liquid to gas. You will receive 10 definition cards and 10 word cards. A copy of the carbon cycle A4 sheet for each pupil Figure 1. Either a copy of. Carbon Cycle Worksheet Homeschooldressage.
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