Chemistry Reference
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individuals were more mature than the pot scale, this behavior was somewhat modest, with
little variation between the values of Gs. This fact can be justified by the findings obtained
by [8] and [25], where they report that with the aging of individuals, the maximum levels of
stomatal conductance decrease due to the greater sensitivity of stomata to the vapor
pressure deficit of the atmosphere. Table 3 also shows the drop in correlation values
between Gs and VPD with increasing age (scale) until appearing to be non-significant in the
watershed scale.
In the other relations it was possible to predict the ecophysiological behavior with
adjustment of the proposed model from young subjects, in this case, the pot scale with 120
days of age, for individuals with 240 days (plot scale) and for individuals with 60 months
(watershed scale), approximately (Tables 4, 5 and 6). However, it also could be verified the
accuracy of the model proposed for extrapolating the plot scale to the watershed scale in
situations involving E, Qleaf and VPD without adjusting the model (Tables 4 and 6). There is
a clear similarity between the ecophysiological responses of these two scales in Figures 2a,
2b and 2c.
The use of models seeks to simplify the complexity of real world privileging certain
fundamental aspects of a system at the expense of detail. To provide an approximate view of
reality, a model must be simple enough to be understood and used, and complex enough to
represent the system under study [1]. The idea of proposing a model based on
environmental variables (Qleaf and VPD) has been strengthened by [45], stating that the
model reflects the conditions of the dynamics of the transport process in the soil-plant-
atmosphere system, constituting the main component responsible for the flow of water in
the plant.
Although the regression of E depending on Qleaf and VPD (Figure 2a and 2c) show the
proximity of the tendency of the response of E between the plot and watershed scales with
increasing Qleaf and / or VPD, the mean values obtained in field were lower for the
watershed scale (Tables 4 and 6). This fact may be related to the reduced number of
observations to the watershed scale compared to others, which may end up masking the
results. Another important detail is related to environmental variables, both Qleaf and VPD
that present, on average, lower than in the days of assessment of the pot and plot scales.
In [20] throughout the work "Physiology in forest models: history and the future" discusses
the importance of understanding the operation and its ecophysiological approach in models
of forest production. In literature, several papers are presented in order to relate the highest
rates of gas exchange and growth of individuals or young forests with more mature ones. In
[5] for example, discuss that the forest productivity increases during the rotation, reaches a
peak near the period when the leaf area is maximum and then decreases substantially. But
the reasons for this decline are not yet completely understood [33, 47]. The latest hypothesis
about the decline in productivity with age was developed by [34], called the hydraulic
limitation hypothesis.
As trees age, their hydraulic properties change, and at the same time, the amount of
radiation intercepted by the canopy varies substantially [17]. With the increased size of the
