Riparian Status (FREP)
Not functioning properly corresponds to 23% of the visited sites and the other 77% are still functioning, including 46% with some or high risk of becoming 'not properly functioning'.
Questions 1, 6, 10, 12, 14 and 15 provide the idea of a low disturbance with aquatic habitat and native vegetation. However, Questions 2, 3, 7, 8, 11 and 13 suggest erosive processes and deficiency at the streambank, where the sediments can be retained last.
Questions 1, 6, 10, 12, 14 and 15 provide the idea of a low disturbance with aquatic habitat and native vegetation. However, Questions 2, 3, 7, 8, 11 and 13 suggest erosive processes and deficiency at the streambank, where the sediments can be retained last.
Question 1: What are the factors involving a not properly functioning riparian area?
Graph 11: Multivariate partitioning (mvpart) - CART - of the 15 main questions. The title of question 13 was replaced by one of its sub-questions to highlight the effect of the streambank coverage. Its main question is "Has sufficient vegetation been retained to provide shade and reduce bank microclimate change? " and it is 'yes' only if the guidance sub-question is 'yes' as well.
Table 03: Amount of the variance explained by the questions.
Split |
Amount of variance explained |
Q13 |
51.25% |
Q12 |
6.65% |
Q11 |
6.22% |
Q7 |
3.16% |
Q4 |
2.68% |
Q12 |
2.02% |
Questions 13, 12 and 11 are all related to vegetation and their mechanisms provide functionality to the riparian area.
Question 13 - Trees and shrubs in the streambank - is the first node and it is responsible for 51% of the variance. This question establishes 60% of minimum coverage by deep-rooted plants such as shrubs and trees.
Question 12 as second and third node evidence the importance of the root network and woody debris to have a properly functioning riparian area.
Question 11 means surface protection to avoid erosion.
Therefore, plants with larger dimensions and deep root systems are the key component of a healthy riparian area.
As many factors in a riparian area are related, questions 04 and 07 present 'moss' and 'channel morphology' as indicators of the level of disturbance or consequences of the adequate quantity of larger plants. Moss depends on shade and water retention by woody debris to grow. Channel morphology needs the stability of the banks provided by deep-rooted plants to keep their morphology intact.
Question 13 - Trees and shrubs in the streambank - is the first node and it is responsible for 51% of the variance. This question establishes 60% of minimum coverage by deep-rooted plants such as shrubs and trees.
Question 12 as second and third node evidence the importance of the root network and woody debris to have a properly functioning riparian area.
Question 11 means surface protection to avoid erosion.
Therefore, plants with larger dimensions and deep root systems are the key component of a healthy riparian area.
As many factors in a riparian area are related, questions 04 and 07 present 'moss' and 'channel morphology' as indicators of the level of disturbance or consequences of the adequate quantity of larger plants. Moss depends on shade and water retention by woody debris to grow. Channel morphology needs the stability of the banks provided by deep-rooted plants to keep their morphology intact.
Table 04: Questions that could alternatively be used as criteria in the multivariate regression tree analysis.
Alternatives to Q13 |
Threshold left side |
Amount of variance explained |
Q11 |
<0.5 |
44.28% |
Q12 |
< 0.5 |
36.74% |
Q2 |
< 0.5 |
32.32% |
The alternatives to Question 13 on the first node would be Q11: regarding the soil coverage; or Q12: presence of root network and large woody debris production; or Q2: if the streambank is intact.
Correlations
The correlation among the causes of damages, presence of deep-rooted plants on banks and riparian status is represented by the table below.
Table 05 : Correlations among causes and effect related to the factor raised by the multivariate analysis.
R² |
Natural Cause |
Anthropic Cause |
Natural + Anthropic Causes |
Deep-rooted bank |
Natural Cause |
1 |
-0.4 |
0.4 |
-0.2 |
Anthropic Cause |
-0.4 |
1 |
0.7 |
-0.2 |
Natural + Anthropic Causes |
0.4 |
0.7 |
1 |
-0.4 |
Deep-rooted bank |
-0.2 |
-0.2 |
-0.4 |
1 |
Riparian Status |
-0.4 |
-0.6 |
-0.9 |
0.4 |
Question 2: How do conventional treatments contribute on riparian functionality?
'Natural + Anthropic causes' is inversely correlated to the 'Riparian Status' (-0.9). This evidences that the more damaged, the less properly functioning the riparian area will be.
Individually, 'Natural cause' (-0.4) presents a lower correlation to the riparian status than 'Anthropic cause' (-0.6). That points to fact that damages caused by nature are less significant than the damages caused by human activities regarding the riparian functionality.
Deep-rooted bank means the bank area coverage by plants with deep root systems as defined in the methodology. Both 'Natural Cause' and 'Anthropic Cause' presents a low and inverse correlation (-0.2) individually. However, when correlated to the total, 'Natural + Anthropic Causes' (-0.4), the more deep-rooted plants on the bank, the fewer damages in the riparian area independently whether natural or anthropic. In the opposite way (+0.4), the more deep-rooted the bank, the better is the riparian status, reinforcing the importance of deep-rooted plants on banks.
Once 'Natural Cause' is less significant (-0.4) to riparian status than 'Anthropic Cause (-0.6), allied to the fact that those factors individually have the same low and inverse correlation with the coverage by deep-rooted plants (-0.2), and together presents lower and still negative correlation (-0.4), it is possible to understand that natural damages may eliminate deep-rooted plants from banks and riparian area, however the effect on riparian functionality is less severe than when they are suppressed by human activities. This is also evidenced by Graph 09 on the 'Data Exploration' tab where 'Not properly functioning' riparian areas present more 'Anthropic causes' than 'Natural'.
Individually, 'Natural cause' (-0.4) presents a lower correlation to the riparian status than 'Anthropic cause' (-0.6). That points to fact that damages caused by nature are less significant than the damages caused by human activities regarding the riparian functionality.
Deep-rooted bank means the bank area coverage by plants with deep root systems as defined in the methodology. Both 'Natural Cause' and 'Anthropic Cause' presents a low and inverse correlation (-0.2) individually. However, when correlated to the total, 'Natural + Anthropic Causes' (-0.4), the more deep-rooted plants on the bank, the fewer damages in the riparian area independently whether natural or anthropic. In the opposite way (+0.4), the more deep-rooted the bank, the better is the riparian status, reinforcing the importance of deep-rooted plants on banks.
Once 'Natural Cause' is less significant (-0.4) to riparian status than 'Anthropic Cause (-0.6), allied to the fact that those factors individually have the same low and inverse correlation with the coverage by deep-rooted plants (-0.2), and together presents lower and still negative correlation (-0.4), it is possible to understand that natural damages may eliminate deep-rooted plants from banks and riparian area, however the effect on riparian functionality is less severe than when they are suppressed by human activities. This is also evidenced by Graph 09 on the 'Data Exploration' tab where 'Not properly functioning' riparian areas present more 'Anthropic causes' than 'Natural'.