## 4 Discussion
### Effect of Spatial Drivers on Leaf and Canopy Level  
In large scale patterns, leaf level biophysics are overwritten by canopy characteristics. However, the leaf characteristics are affected by spatial drivers. Both chlorophyll a+b and caroten contents were strongly affected by the duration of flooding and the influence of creeks. These relations were positive; higher flood duration increases chlorophyll content. As plants that are flooded more often suffer a higher stress, the opposite might be also expected. Decreasing chlorophyll content is a common response to a variety of stressors [74]. _Spartina_ is also known to decrease its chlorophyll when stressed, but the force required to stress a plant differs greatly between _Spartina_ species [75]. It is possible that in our study site _Spartina_ was not stressed by the regular flooding. Plants are able to adapt well to regularly occurring phenomena, such as the day night cycle, and these factors are not considered stressors, but are described as'regular acclimation' [76]. However, our results indicate that biomass is lower when they are flooded more frequently, indicating that they are indeed stressed. This is also indicated by their improved growth when moved higher in the marsh [2]. Another possibility is that the increase in environmental stress reduces light competition, although our data showed that chlorophyll content is not related to competition. Light availability is also codetermined by flood duration, as top leafs are flooded less than the rest of the plant. We tested the chlorophyll content of fully grown leaves near the top of the plant, so it is also possible that these plants allocate more of their chlorophyll production to their highest leaves, as these are flooded least. This will have to be studied further.  
Creeks were also found to strongly affect chlorophyll content (a+b and caroten). Creeks are known to affect soil conditions (e.g., carbon and nitrogen content) [41], which could play a role in chlorophyll development. However, many of our plots were >40 m away from a Creek, and chlorophyll content is lowest closer to a Creek. Chlorophyll content is therefore unlikely to be a largely affected by nutrients provided by creeks. It remains unclear how this spatial driver affects vegetation properties. The position of a Creek might be codetermined by an underlying cause also affecting chlorophyll content, or the spatial influence of creeks might be larger than expected.  
At the canopy level, we found that LAI and soil moisture content are affected most by wave forcing and competition. In our study area, wave forcing and competition complement each other: high competition only occurs at low wave forcing and vice versa. The _Spartina_ LAI values here presented decreased as competition increased, and correspondingly, also decreased at low wave force levels. A similar pattern is seen in the relation between LAI and flood duration. At low flood duration LAI is low, which corresponds to an increased competition. The highest LAI values occur at intermediate flood duration. This hints towards an optimal growing position, close to the water a high flood duration causes stress, high in the marsh competitors cause stress. This pattern is known in salt marshes [2].  
Overall, the effects of spatial drivers are stronger at the leaf level, likely because here biophysical properties are relatively simple and easy to measure. At the canopy level, there is more noise and the effect of spatial drivers becomes less obvious. This is likely because the canopy level has more complex parameters, such as leaf orientation, which are difficult to measure correctly [12]. The larger variation at canopy level is reinforced by the inherit increase in variation that comes with scaling up. The relationships described by the regression models is intended to show how vegetation characteristics respond to spatial drivers, we would therefore argue for great caution when applying them as predictive models.