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*Leaves/needles show signs or symptoms of damage due to biotic or abiotic factors. Note the number and location of these areas and describe the nature (e.g. color, size, affected part of the tree) of each affected area. Refer to the following table on the Scoring System of Trees Based on Observed Signs and Symptoms | *Leaves/needles show signs or symptoms of damage due to biotic or abiotic factors. Note the number and location of these areas and describe the nature (e.g. color, size, affected part of the tree) of each affected area. Refer to the following table on the Scoring System of Trees Based on Observed Signs and Symptoms | ||
*Describe any of the observed issues designated in the scoring system. | *Describe any of the observed issues designated in the scoring system. | ||
+ | |||
+ | ====Crown distance assessment==== | ||
+ | The distance between individual canopies can provide positive and negative aspects to tree health. Some positive aspects of canopies being in close proximity to their neighbors is collective support from wind and other abiotic factors, whereas some negative aspects are increased disease transmissivity, shading, and competition for finite moisture and other resources. | ||
+ | *Rate the overall crown distance between adjacent trees in each perpendicular direction and the monitored individual using the system in the table below. | ||
+ | *Please describe any of the observed issues within or among the canopy relating to the adjacent canopies in the scoring system. |
The health of an urban, suburban, rural, or natural forest is rarely limited to individual species alone. An assessment of forest health should be related to both the individual tree and the collection of trees, including interactions between trees.
Many metrics and methods have been developed for assessment of individual tree health. The concept of “resilience” at the individual and canopy levels is the core of the assessment tools. The majority of these evaluative methods and metrics focus on the response of the individual or evaluative unit to a disturbance regime to quantify the “resilience.” The type and capacity of response to the given disturbance and the time it takes to return to the initial qualitative equilibrium state indicate the overall resilience to the disturbance or pressure. Eichorn and Roskams (2013) cite various sources indicating that this return to “equilibrium” is not always return to the initial state, stating that, “open systems will reorganize at critical points of instability.” Determining the critical thresholds for certain pressures, disturbances, and changes the system or individual can tolerate before it cannot recover can provide a proxy for tree and forest health.
The resilience of the tree individuals and canopy is often difficult to quantify directly for multiple pressures. Rather, indirect measures are often employed for inventory and monitoring of tree health. Measurements and metrics can also be taken both directly (e.g. assessing growth rings from a core) and indirectly (e.g. remote sensing of canopy leaf area). Direct and indirect methodologies are discussed and compared below. It is suggested that the base of monitoring, evaluation, and correlation of forest health be that of overall forest resilience, rather than individual tree health. The foundation of the assessment focuses on the health of the individual as a component of the collection of individuals in the forest canopy. Eichhorn and Roskams (2013) suggest using two levels of monitoring and implementation:
These levels are not distinct in their interactions and the information gained at each level can inform the interactions and information at the other level. Interactions at each of these levels may also be correlated with and inform forest health and interactions at the national or global scale. We suggest future strategies and policy efforts to standardize, create, and implement a larger national, and possibly global, forest assessment tool for monitoring, assessing, and evaluating the health of our forest. Per the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests, implementation within the MPCA tree monitoring focuses on the following objectives of Minnesota tree condition monitoring, as a subset of the national and global forest system (Eichorn and Roskams (2013): to contribute to a Minnesota-wide early warning system and to a better understanding of tree vitality, including relationships to stress factors and ecosystem disturbances;
The methodologies presented hereafter focus on these objects in order to establish a framework for a comprehensive tree monitoring system that can be added to as new methodologies and assessment tools emerge.
Assessment of tree and forest health can be measured directly or indirectly at either the Level 1 (overall forest) or Level 2 (individual or stand) scales. Indicators of tree condition found in monitoring efforts may be assessed via qualitative and quantitative methods for assessing morphology and architecture (canopy, trunk, fruit, roots, etc.), forest composition, biotic/abiotic agents, growth rate, and age. Eichhorn and Roskams (2013) give an overview of indicators of tree health that may be focused on within a monitoring program at both Level 1 and Level 2, and the targeted areas for assessment and evaluation. A summary of variables they suggest as indicators of tree condition is presented below.
The proposed MPCA tree and forest monitoring system and protocol presented hereafter focuses mainly on direct measurements of individual trees at a Level 1 scale, as a proxy for Level 2 interactions, using the Eichhorn-Roskams (2013) methodology described above.
Direct measurement methods typically employ tree architecture and morphology as a measure and indicator of tree health. The measurements are broken down by foliation (defoliation) of the upper crown/canopy, apical shoot architecture, and fructification. The following table breaks down the areas of evaluation and assessment within each category of tree area.
Qualitative and quantitative evaluation and assessment of trees, by area of tree.
Link to this table.
Area of tree | Qualitative and quantitative evaluation and assessment |
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Foliage | Leaves, related to ability of tree to capture light for metabolic processes (photosynthesis), particularly noting:
|
Apical shoots and overall tree architecture and morphology |
|
Fructification | Fruit production, as an indicator of reproductive success and health, infection or stress-related response
|
Roots |
|
This section provides a recommended monitoring protocol. The goal of monitoring is to identify issues or concerns that require a response. Responses to monitoring findings are presented in the Operation and maintenance of tree trenches and tree boxes section of this Manual. Specific troubleshooting responses are presented in [table]. This series of responses is mainly on a Level 1, or individual basis, with limited Level 2 assessment suggested via remote sensing technologies. The collection, interpretation, and response to the larger forest (Level 2) health, requires collection and collaboration of results between individuals. Large-scale comparative and predictive metrics and an ecosystem-scale assessment system is suggested for future investigation to provide a standardized system for collection and comparison of Level 1 monitoring information.
Annual tree monitoring is suggested for the crown and apical shoots (all above-ground structures). It is suggested that this could be performed with rapid assessment tools by citizens’ monitoring programs, watersheds, municipalities, or other groups. Standardization of the monitoring information collected, date of collection, procedure for collection, and reporting of monitoring for comparison of results between individuals and over larger areas is suggested.
Two points should be established and noted on a map and/or (preferred) GPS (Global Positioning System) device for consistent results collection. One point (Point A) should be directly underneath the tree for assessment of leaf area coverage and canopy diameter. The second point (Point B) provides quantitative and qualitative results of tree height and vertical leaf coverage, and is suggested to be at least 50 feet from trunk to provide a fixed location for consistent evaluation as the tree grows. A GIS (Geographic Information system) coverage and GPS-based system would aid in consistent evaluation and database assembly for large-scale evaluation and monitoring assessment and responses. Leaf and other tree debris can also be evaluated at any location underneath and surrounding the tree for gathering additional information regarding tree illness, injury, or stress responses.
Following information gathered should be assembled into a standard format. The information gathered focuses on the above-ground portion of the tree and surface root presence, on an individual/single-tree basis as the standard unit of measurement. Please note: fructification can give ambiguous indications of overall health, and it should not be used as an independent indication of tree health. Fructification can be used in conjunction with the above-ground structural assessment as a component of the Level 1 (individual or stand) monitoring, but will be more effective as a Level 2 (larger-scale forest assessment) to indicate ecosystem-wide response to stressors, such as insect invasion and long-term drought or reduced soil moisture availability.
Level 1 Tree Monitoring focuses on the individual or small unit of individual trees for a field-based assessment tool. This program allows for increased ability to be performed by a layperson or expert, but does not utilize less-accessible programs and methods such as GIS-based or model-based systems that would be more useful at a Level 2 analysis. Other methodologies – electrical conductivity within sap, chlorophyll fluorescence, glucose presence - for Level 1 monitoring were encountered in the literature review, but the tools and/or knowledge required to perform the analyses or monitoring or the detailed level of information gather were prohibitive for generalized use in this level of monitoring program. (Martinez-Trinidad, et al. 2010). It is suggested that this monitoring methodology be standardized in a rapid assessment form for data collection and comparison throughout Minnesota to better perform the Level 2 analyses and provide a greater degree of statistical confidence in results due to standardized methodology.
Includes the leaves and leaf structures and/or needles in the tree. Take a photo from Location A and B that captures the extent of the foliage. Take multiple images if necessary, indicating the general direction of view. Complete the following assessment of the canopy, providing additional information of photo-documentation where appropriate.
Assessing the tree canopy and above-ground structures. Take a photo from Location A and B that captures the extent of the foliage. Take multiple images if necessary, indicating the general direction of view. Complete the following assessment of the canopy, providing additional information of photo-documentation where appropriate.
Link to this table.
Defoliation: a relative amount of needles or leaves are missing from the canopy as compared to a reference tree. | |
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Is there any level of defoliation noted? |
____ Yes |
If defoliation is present, estimate the percent defoliation | |
Describe the location, relative area (ft2) of the defoliation, percent canopy/leaf loss (% of whole area), and any other notable information regarding each defoliation area noted from visual assessment at Locations A and B. Take photographs as necessary, noting the general direction of view. | |
Apical Shoot Architecture: the architecture of the most recent growth of branches in the canopy where the majority of leaves are located and arranged. Answer all of the following questions when examining the apical shoot architecture from Locations A and B and then rate the tree using the Apical shoot scoring system for the Apical Shoot Architecture. | |
What is the estimated length of a typical apical shoot (inches)? | |
Are the upper-most apical shoots alive, as indicated by color and twig turgor pressure (e.g. not dried and brittle in appearance)? |
____ Yes |
What is the color of the typical apical shoot? |
___ Light brown |
Is there any presence of the following in the apical branch growth? Mark all that apply, and indicate general location of the noted issues. |
___ spear-shaped twigs |
Describe any of the noted issues. | |
Fructification: the fruits and fruiting bodies of trees can indicate much about the health or lack thereof of the individual. Answer all of the following, per the Fructification scoring system. | |
Is fruit present on the tree? Only note the presence of new fruit from this year, and not “old” fruit from the previous year, as would be distinguished as wrinkled or shriveled in appearance. |
___Yes |
Describe the location, relative area covered, and any other notable information regarding the fruiting from Locations A and B. Please take photographs as necessary, noting the general direction of view. | |
Roots: the majority of the root system should be below ground and relatively difficult to assess and monitor, however, the presence and effects of circling/girdling roots may provide symptoms in tree morphology. Answer all of the following. | |
Is there a lack of branching or a flat side observed on the tree, or are there any girdling roots observed around the main trunk at or above the soil surface? Note the presence of these features that would indicate root-related issues. |
___ Yes |
Describe the location and any other notable information regarding the presence of roots above ground from Locations A and B. Take photographs as necessary, noting the general direction of view. |
These pressures are witnessed by signs (direct evidence of a damaging factor) and symptoms (indirect results or evidence of the damaging factor (e.g. leaf proliferation following a windstorm)) of tree health due to biotic and abiotic (environmental) influences. Assess the following damages due to biotic and abiotic factors using the following questions and scoring table.
The distance between individual canopies can provide positive and negative aspects to tree health. Some positive aspects of canopies being in close proximity to their neighbors is collective support from wind and other abiotic factors, whereas some negative aspects are increased disease transmissivity, shading, and competition for finite moisture and other resources.