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A Comparison of Tree Health Among Forest Types and Conditions at Fort A.P. Hill, Virginia

Posted on: Thursday, 18 August 2005, 03:01 CDT

ABSTRACT: Fort A.P. Hill's Range and Training Land Assessments (RTLA) program initiated long-term monitoring of installation forests to assess forest health and ensure optimal sustainability afforest resources for military training activities. A subset afforest health indicators developed by the USDA Forest Service Forest Health Monitoring (FHM) and Forest Inventory and Analysis programs were used to assess forest health on Army training lands at Fort A.P. Hill, Virginia. Indicators of tree crown condition and tree damage condition were taken in forested areas where militarv training occurs, "tactical concealment areas (TCAs), " and on continuous forest monitoring (CFM) plots established in control stands where military training is absent. A higher percent of trees with high crown dieback, low crown density, and multiple types of stem damage were observed within TCAs than on CFM plots. The results are indicative of possible long-term changes to forest health from military training activities. The FHM forest health indicators proved to be an effective and useful approach to assess tree conditions. South. J. Appl. For. 29(3): 143-147.

Key Words: Forest Health Monitoring, forest health indicators, tactical concealment areas, continuous forest monitoring, military training.

The Department of Defense (DoD) is the fifth largest federal land management agency responsible for managing 25 million ac (10.1 million ha) of land on more than 425 major military installations (Boice 1997). The Army is responsible for almost half of those holdings (12 million ac [4.8 million ha]) and manages its natural resources in accordance with federal, state, and, where appropriate, hostnation environmental laws (Doe et al. 1999).

Natural resources inventory, monitoring, and management activities are conducted under the conservation and stewardship ethos to ensure sustainability of the environment as well as military training, which is the predominant land use.

Fort A.P. Hill's Range and Training Land Assessments (RTLA) program conducts long-term monitoring of forest health on the installation, both in stands where military training is prevalent and in control stands where training is absent. Monitoring of both facilitates comparative analyses to assess impacts from military training and evaluations of forest management activities. The forest stands used for [vehicle] maneuver training are managed as "tactical concealment areas" (TCAs) and have been used as such for decades.

Military units rely on TCAs for a variety of year-round diurnal and/or nocturnal functions such as assembly areas, after-action review sites, tactical operation centers, and sites for bivouacking ("military camping"). Though the sum of these areas amounts to less than 1 % of the total land area of Fort A.P. Hill, these areas are critical for realistic training experiences. As such, TCA sustainability is a management goal of Fort A.P. Hill's Integrated Training Area Management program because military maneuver training can cause soil compaction and decrease plant species cover (Johnson 1982, Trumball et al. 1994, Michunas et al. 1999, Presser et al. 2000), while bivouacking specifically has been shown to decrease groundcover, plant density, and species richness (Trumball et al. 1994). Although forested, TCAs are managed as facilities, using maintenance and rehabilitation practices analogous to recreation campsites (Universal Technologies 2001).

The Forest Health Monitoring (FHM) and Forest Inventory and Analysis (FIA) programs of the USDA Forest Service have developed and implemented forest health indicators to assess resource conditions and trends for local and landscape-level analyses (Mangold 2000). Some of these indicators are tree-level observations that characterize overall tree crown and tree damage condition. These tree-level indicators have been used to conduct trend analysis for individual tree species on a regional scale (Burkman and Bechtold 2000), as well as to conduct small-scale forest health surveys (Randolph 2004). These indicators also provide the basis for quantifying tree health by determining critical thresholds of crown and damage conditions deemed likely to lead to mortality (Steinman 2000). Though these tree-level indicators represent only a small portion of the full suite of all forest health indicators, they were selected to be the most appropriate to use based on preliminary work conducted at Fort A.P Hill.

In this article, tree health indicators were used to estimate overall forest health in forest areas where military training is prevalent and absent to determine if any differences in forest health could be associated with military training activities on Fort A.P. Hill, Virginia. The data presented are the initial (baseline) data on forest health from a larger monitoring program.

Study Site

Fort A.P. Hill is a 75,794-ac (30,686-ha) US Army installation located in Caroline County, Virginia, situated between the metropolitan areas of Richmond and Washington, DC (Figure 1). Fort A.P. Hill is the sixth largest Army installation east of the Mississippi River, consisting of a 27,000-ac live-fire range complex and approximately 49,000 ac of nonlive-fire (vehicle) maneuver training areas. The installation is approximately 80% forested, with the majority of the forest cover types composed of loblolly pine (Pinus taeda), Virginia pine (Pinus virginiana), and mixed oaks (Quercus spp.). Fort A.P. Hill conducted an installation-level forest inventory between 1994 and 1995 that provided stand-level information on forest structure, composition, and density to guide forest management. The forestry department and RTLA program subsequently created a long-term forest monitoring program, continuous forest monitoring (CFM), to provide information on overall stand dynamics, timber growth and yield, and forest health conditions for the more than 1,300 managed forest stands on the installation.

Table 1. Distribution of TCAs and CFM plots by forest cover type on Fort A.P. Hill (1997-2001).

Figure 1. Fort A.P. Hill and the surrounding area.

Methods

Sampling

Circular 32.8-ft (10-m) radius macroplots (overstory tree measurements), each one containing a 16.4-ft (5.0-m) radius subplot (shrub and sapling density), and four 3.28-ft (1-m) square quadrats (seedling density and groundcover estimates) were established in control stands and TCAs as described below.

Control Stands (CFM Plots)

Using the 1994-95 forest inventory, forest stands were stratified into one of three general forest cover types based on stand age and overstory characteristics (hardwood or softwood) for landscape- level inferences (Table 1). This generalized stratification was selected because it met the management needs of the installation. Individual stands of each cover type were randomly selected for proportional sampling. An index was developed using the percent of total forest area by cover type and the number of stands per cover type to determine the proportion of plots allocated to each cover type. One plot was allocated to each selected stand (Figure 2). Plot centers were monumented with PVC piping protruding less than 1 ft (29.6 cm) above the ground. Three trees were selected as witness trees with their distance and bearings to plot center recorded. Qualitative observations on land use were taken during data collection to confirm that plots were established in areas not being used for military training. All CFM plots were inventoried in May through Aug. 1997.

TCAs

TCAs in the maneuver training areas were identified and delineated by installation personnel prior to the inventory. TCAs were stratified by forest cover types identical to the control stands (Table 1). TCAs were then stratified into size classes based on the installation-level management and training requirements of TCAs (Table 2). Between two and five plots were systematically established within each TCA using a 164-ft (50-m) 164-ft (50-m) spacing, or a 82-ft (25-m) 82-ft (25-m) spacing if the 164-ft^sup 2^ (50-m^sup 2^) spacing resulted in less than two plots in a TCA (Figure 2). Multiple plots were established in each TCA to provide information on stand density, species composition, and regeneration potential in addition to information on forest health because TCAs were not distinguishable in the 1994-95 forest inventory. Plot centers were 6-in.-long metal spikes driven flush with the ground. Data were collected in May through Aug. (1999-2001).

Field Measures

The following forest health indicators were recorded for each tree on a TCA and CFM plot to assess forest health conditions.

Figure 2. Inventory plot design.

Table 2. Distribution of TCAs by size class and military unit size on Fort A.P. Hill (1997-2001).

Crown Condition

Uncompacted live crown ratio is a percentage determined by dividing the live crown height by the total live tree height. Crown density is the amount of crown branches, foliage, and reproductive structures that blocks light visibility through the crown (measured as a percent). Crown dieback estimates the severity of recent stress on a tree, recorded as a percentage of the live crown area (USDA Forest Service 2002). All observations for the crown condition indicators were taken to the nearest 5%.

Damage Condition

A maximum of four types of damage were recorded for each tree on a TCA and CFM plot. Three \types specific to FHM and the fourth, exposed roots, was an installationlevel concern added to the list of FHM damages to observe (Table 3).

With the exception of root exposure (presence or absence), the following attributes were recorded for each damage observed:

* Location on the tree (e.g., stump, lower bole, upper bole);

* Severity of the occurrence (% of tree face affected); and

* Damage type.

(USDA Forest Service 2002). With the exception of crown density, indicators of crown and damage condition were taken on all trees ≥3.9 in. (10.0 cm) in dbh within 32.8 ft (10 m) of plot center. Crown density measures were subsampled on 20% of CFM plots and on TCAs greater than 10 ac due to time constraints.

Analysis

The analysis tested the hypotheses that a number of tree-level indicators of crown and damage condition were equivalent in the control and TCA areas. The critical thresholds developed by Steinman (2000) for crown conditions were used in the analysis of the data.

Table 3. List of damages to trees observed on TCAs and CFM plots on Fort A.P. Hill (1997-2001).

While field measures of crown conditions can range from 0 to 100%, conditions likely to lead to mortality are the percent of trees per unit area with low live crown ratio (<30%), low crown density (<30%), and/or high crown dieback (>10%; Steinman 2000). Critical thresholds to predict mortality based on tree damages observed in this assessment have not as yet been developed. Although acreage (size) was a factor in assigning plots to TCAs, all comparisons in forest health measurements were made between trees on TCAs and CFM plots by forest cover type to facilitate robust testing. Three separate Wilcoxon Signed Rank Tests were performed (one for each cover type; α=0.05) with an experiment-wise alpha level adjusted to 0.0009 (α') to compensate for running multiple tests simultaneously (Miller 1991). Failure to adjust the alpha level in this case would increase the likelihood of making a Type I error. Nonparametric tests were conducted because of the non- normal nature of the data, the relative inequality of sample sizes, and violation of the equal variance assumption between land uses.

The overall research hypothesis being tested can be expressed generally as:

H^sub 0^: tree condition^sub TCAs^ = tree condition^sub CFM plots^

H^sub 1^: tree conditions^sub TCAs^ ≠ tree condition^sub CFM plots^

If the null hypothesis was rejected, the findings would suggest associations between forest health conditions and military training. A cause/effect relationship between forest health and military training cannot be established because of the parameters of the study.

Results

Forest health indicators detected differences in crown and damage conditions between trees on TCAs and CFM plots, indicating a decrease in forest health associated with military training. TCAs contained a higher mean percent of trees with low crown density than CFM plots across all forest cover types (Figure 3). TCAs also contained a higher mean percent of trees with high crown dieback than trees on CFM plots for two of the three forest cover types (Figure 3). The mean percent of trees with low live crown ratios was not significantly different between TCAs and CFM plots (Figure 3). The mean percent of trees with stem damage was consistently higher on TCAs than CFM plots for most of the damage types observed. Four of the six types of damages observed occurred more on TCAs than CFM plots for all three forest cover types (Figure 4). TCAs subsequently contained a higher mean percent of trees with any type damage for two of the three forest cover types (Figure 4). The mean percent of trees with decay and the loss of apical dominance were not significantly different between TCAs and CFM plots (Figure 4).

Figure 3. Mean crown conditions between trees on TCAs and on CFM plots by cover type (1 standard error).

Discussion

A decrease in forest health was found to be associated with military training activities. TCAs had more trees with poor crown condition for two of the three indicators (crown density and crown dieback) in at least two of the three cover types. Given the nature of military training that occurs on TCAs, stem damage would likely be the direct impact from military training, whereas the occurrence of poor crown conditions may indicate the indirect or long-term effect of tree stress from those direct impacts (repetitive and multiple stem damages). TCAs had more trees with open wounds attributed to vehicle-tree collisions. These collisions are not an intentional aspect of military training but are attributed to nocturnal activities as well as the size of the vehicles maneuvering through the forests. However, the frequency, extent, and cumulative impacts of those collisions were hitherto unknown. Of particular interest is the sole occurrence of root exposure to trees on TCAs, indicating a specific type of damage associated with military training activities. The decrease in groundcover and increase in soil compaction from repealed and heavy military training (Trumball et al. 1994) may lead to root exposure.

Though four of the six types of damage consistently occurred more frequently on TCAs across all three cover types, the opposite trend was seen for the presence of decay and the loss of apical dominance. This suggests that those damages occur from natural processes unrelated to military training activities (such as decay fungi and storm damage, respectively).

Figure 4. Mean damage conditions between trees on TCAs and CFM plots by cover type (1 standard error).

The lack of significant differences in the percent of trees with any damage and the percent of trees with high crown dieback between TCAs and CFM plots in the hardwood stands less than 85 years old cover type may be a function of stand density and/or RTLA sampling. Younger hardwood stands used for TCAs are generally overstocked. As stated previously, TCAs are not managed as forest stands so they would not have been commercially thinned at any point. Therefore, vehicle traffic is likely restricted to few select trails that amount to a small fraction of the overall TCA area. Damage to the trees might therefore be concentrated along the edge of trails and not evenly dispersed throughout the entirety of the TCA. Its possible that impacts went undetected because trail edges were not specifically targeted for sampling but were meant to be included as part of the sampling process. Though the causes of the differences in tree condition warrant further research, the use of forest health indicators and the application of critical thresholds were viewed as successes by land and program managers. The use of critical thresholds to asses tree health have since been expanded to assess changes in tree condition associated with live-fire munitions damage (Applegate and Davis 2003, Applegate 2004). Further research comparing Fort A.P. Hill data with national FHM data at the state or regional level would allow for greater interpretation of these findings once USDA Forest Service reports become available.

Conclusion

Forest health indicators proved useful in quantifying resource conditions and showing associations between forest health conditions and military training activities. Critical thresholds were equally useful in qualifying existing conditions and were used by land managers to prioritize sites for remediation of conditions. RTLA will continue to monitor forest conditions on TCAs and CFM plots for long-term trend analysis to better understand the dynamics of military training on forest health. The application of forest health indicators and critical thresholds may prove useful to other Army installations with similar training requirements. The results of this project show current conditions that may be indicative of long- term forest health concerns from military training activities. The results also add to the growing body of knowledge regarding long- term environmental impacts from military training activities and can be used to develop management approaches to sustain TCAs for military training activities.

Literature Cited

APPLEGATE, J.R., AND R. DAVIS. 2003. Target: Firing range health. The Military Engineer 95(625):39-40.

APPLEGATE, J.R. 2004. Managing the range environment for Infantry training. Infantry Magazine May-June:47-48.

BOICE, L.P. 1997. Defending our nation and its biodiversity. End. Spec. Bull. 22(1):4-5.

BURKMAN, W.G.. AND W.A. BECHTOLD. 2000. Has Virginia pine declined? The use of forest health monitoring and other information in determination. P. 258-264 in Integrated tools for natural resources inventories in the 21st century: An international conference on the inventory and monitoring of forested ecosystems, Hansen, M., and T. Burk (eds.). Gen. Tech. Rep. NRCS-212, St. Paul, MN.

DOE, W.W. III, R.B. SHAW, R.G. BAILEY, D.S. JONES, AND T.E. MACIA. 1999. Locations and environments of U.S. Army training and testing lands: An ecoregion framework for assessment. Federal Facilities Environ. J. 3:9-26.

JOHNSON, F.L. 1982. Effects of tank training activities on botanical features at Fort Hood, Texas. Southw. Natur. 27(3):309- 314.

MANGOLD, R. 2000. Overview of the forest health monitoring program. P. 129-140 in Integrated tools for natural resources inventories in the 21st century: An international conference on the inventory and monitoring of forested ecosystems, Hansen. M.. and T. Burk, (eds.). Gen. Tech. Rep. NRCS-212. St. Paul. MN.

MILCHUNAS, D.G., K.A. SCHULZ, AND R.B. SHAW. 1999. Plant community responses to disturbance by mechanized military maneuvers. J. Environ. Qual. 28(5): 1533-1547.

MILLER, R.G. JR. 1991. Simultaneous statistical inference. 2nd Ed. Springer-Verlag, New York, NY.

PROSSER, C.W., K.K. SEDIVEC, AND W.T. BARKER. 2000. Tracked vehicle effects on vegetation and soil characteristics. J. Ran. Manage. 53(6):666-670.

RANDOLPH, K.C. 2004. An evaluation of changes i\n tree crown characteristics to assess forest health in two Indiana state parks. North. J. Appl. For. 21(1):50-55.

STEINMAN, J. 2000. Tracking the health of individual trees over time on forest health monitoring plots. P. 334-339 in Integrated tools for natural resources inventories in the 21st century: An international conference on the inventory and monitoring of forested ecosystems, Hansen, M., and T. Burk (eds.). Gen. Tech. Rep. NRCS- 212, St. Paul, MN.

TRUMBALL, V.L., P.C. DLBOIS, R.J. BROZKA, AND R. GUYETTE. 1994. Military camping impacts on vegetation and soils of the Ozark Plateau. J. Environ. Manage. 40(4):329-339.

UNIVERSAL TECHNOLOGIES, INC. 2001. Tactical concealment area (TCA) rehabilitation guide. Unpublished. Directorate of Public Works, Fort A.P. Hill, US Army.

USDA FOREST SERVICE. 2002. Field instructions for southern forest inventories. Available online at fia.fs.fed.us/library/ ForestHealthlndicators.pdf; accessed Nov. 2003.

Jason R. Applegate, Engineering and Environment, Inc., under contract support to the Department of the Army, Fort A.P. Hill, VA 22427; and Jim Steinman, USDA Forest Service, Newtown Square, PA 19073.

NOTE: Jason R. Applegate can be reached at (804) 633-8465: Fax: (804) 633-8443; Jason_R_Applegate@belvoir.army.mil. This article is the first of potentially several works stemming from this effort. Funding for this work was provided by United States Government, and as such is in the Public Domain. This work would not have been possible without support from the US Army Environmental Center and the USDA Forest Service, Southern Research Station. I would also like to thank Kristine Brown for her efforts in conducting and coordinating fieldwork and all field technicians who have assisted the program over the course of this project. This work would not have been possible without their efforts under frequently arduous conditions. Manuscript received March 13. 2003, accepted January 27, 2005. Copyright 2005 by the Society of American Foresters.

Copyright Society of American Foresters Aug 2005

Source: Southern Journal of Applied Forestry

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