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Article

Conifer Growth Patterns in Primary Succession Locations at Mount St. Helens

by
Alicia Rose
,
Cody Blackketter
,
Marisa D. Fisher
,
Carri J. LeRoy
and
Dylan G. Fischer
*
The Evergreen State College, Olympia, WA 98505, USA
*
Author to whom correspondence should be addressed.
Forests 2025, 16(8), 1245; https://doi.org/10.3390/f16081245
Submission received: 30 June 2025 / Revised: 25 July 2025 / Accepted: 27 July 2025 / Published: 30 July 2025
(This article belongs to the Section Forest Ecology and Management)
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Abstract

The 1980 eruption of Mount St. Helens (WA, USA) presented a unique opportunity to observe primary succession in a post-eruption landscape previously dominated by conifer forests. The eruption scoured soil and biological communities adjacent to the mountain, and species of conifers have generally been slow to colonize the nutrient-poor substrate surrounding the volcano. Further, different species of conifer establish and grow at different rates. The recent advancement of conifers in the post-eruption landscape has highlighted a research gap related to conifer growth patterns. We measured the height, age, and incremental growth of 472 trees representing three common conifers, Pseudotsuga menziesii, Abies procera, and Pinus contorta, on debris avalanche (80 sites) and pyroclastic flow (82 sites) disturbance zones of the 1980 eruption. We paired annual incremental growth with recent climate data. We found that height, age, and growth rates differ among species and sites. All species had higher growth rates on the debris avalanche deposit compared to the pyroclastic flow due to either climate or substrate. Climate influences were mixed, where one species increased growth with temperature, another declined, and another was unrelated. Nevertheless, more than 40 years after the eruption, we find rapid height growth in species with implications for future forests.

1. Introduction

The May 1980 eruption of Mount St. Helens (known as Lawílatɬa in the Cowlitz Indigenous language) in Washington State (USA) devastated thousands of acres of surrounding vegetation via the combined forces of the lateral blast, pyroclastic flows, debris avalanche deposits, tephra fall, and volcanic mudflows [1]. The complex and dramatic effects of these disturbance events led to the creation of dynamic new landscapes which vary greatly depending on their location and the type and magnitude of disturbances received [2]. Following the landscape-changing eruption, rates of both primary succession (establishment of species on barren habitats) and secondary succession (establishment of species on disturbed habitats) have been studied extensively [3,4,5,6,7]. Rate and intensity of changes in vegetation have been shown to differ greatly between sites after disturbance [7,8]. The unique post-eruption mosaic of primary succession landscapes nearest to the volcano necessitates site-specific evaluation of growth rates for key species, especially for conifers trees which represent the species previously dominant in the pre-eruption landscape. To date, only a few studies [4,9] have directly evaluated conifer growth rates in this unique landscape due to slow rates of colonization and growth immediately after the eruption (see below). Now, more than 45 years after the eruption, conifers are notably advancing in previously barren primary succession landscapes near the volcano.
The growth and presence of conifers is important for the succession of this and other sites post-disturbance because conifers represent dominant mature forest species at Mount St. Helens [10], they are autogenic ecosystem engineers [11], and the litterfall from sclerophyllous needles is an important source of organic material for forest soils [12]. Many understory plant species common to mature conifer-dominated forests in the Pacific Northwest (USA) are unable to establish in high-light post-disturbance environments [10], especially if the amplitude of inter-annual variation in weather is sufficient to prevent consistent growth opportunities [13]. Once established, conifers can facilitate growth and development of forest-adapted species while discouraging species adapted to high-light environments [14,15].
A select suite of species dominate conifer regeneration in the primary succession habitats at Mount St. Helens [9], yet their relative growth rates (post-establishment) in these primary succession environments may result in some species advancing faster than others. Two species, Noble fir (Abies procera Rehder) and Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) are present across the primary blast-zone associated with the eruption [9]. More recently, Lodgepole pine (Pinus contorta Douglas ex Loudon) has also become more dominant, and this species has the capacity to grow quickly in high-light montane forests. All three species are considered relatively shade-intolerant, and may exhibit rapid regeneration in open habitats [10,16]. Slow initial juvenile growth means A. procera can require 5–12 years to reach breast height, though growth from the sapling stage to maturity can be rapid [17,18], and height growth can surpass fast-growing P. menziesii at 50 to 75 years [18]. Growth of P. menziesii generally accelerates after five years, maintaining rapid height growth for over 200 years [19]. Water availability is thought to be a more commonly limiting factor to continued growth of P. menziesii than energy limitations on growing season length [19]. Pinus contorta is often found on volcanic ash and pumice in the Cascade region. This species also has an unusually wide ecological amplitude allowing it to thrive on both wet, poorly drained sites and coarse, drought-prone soils [10]. Growth curves for common-garden studies of P. contorta indicate that saplings frequently grow rapidly to heights of >1 m in 2 years, and >1.7 m in the first three years [20,21]. Three-year height has been shown to be strongly correlated with 15- and 20-year heights (r2 = 0.6–0.9), and height growth tends to be stronger in saplings from more southern provenances [21]. Further, growth rates for saplings from provenances that were coastal or in the southern Cascades (Oregon, Washington) often had higher growth rates than trees from more interior or northern populations [21]. Thus, population differences in growth rates have been found in P. contorta, but it is unclear how post-disturbance growth rates at Mount St. Helens compare. A study at Mount St. Helens between 2002 and 2010 [9] found that mean height for each conifer species ranged from 0.3 to 0.6 m for A. procera, 0.5–1.0 m for P. menziesii, and 0.3–0.6 m for P. contorta, implying a statistical average growth rate of 0.04–0.06 m per year, but this survey was conducted when the trees were still quite small. Growth rates are likely to increase as conifers become more established in the new volcanic substrates and reach heights sufficient to escape ungulate herbivory. Differential growth rates could result in differential conifer presence in the new habitats as growth rate differences yield differential biomass and increasing dominance by larger trees.
The presence of distinct disturbance environments following the eruption of Mount St. Helens presents the opportunity to compare growth among recently established conifers in contrasting environments (Figure 1). Two distinct locations adjacent to the volcano, the debris avalanche and pyroclastic flow zones, have been extensively studied as primary succession environments. A debris-flow avalanche that occurred from the north slope of the mountain flowed outward in many distinct lobes [3,22]. In contrast, a 20 km2 area known today as the Pumice Plain was hit by the lateral blast and covered by pyroclastic flows which emerged from the crater and destroyed all vegetation [6]. While both areas represent high-light post-disturbance environments, the debris avalanche is generally lower elevation, with warmer conditions and a longer growing season. The debris avalanche also is more likely to have higher residual or legacy organic matter and could accordingly have higher soil nutrient pools. The pyroclastic flow zone, in contrast, represents a classic primary succession environment where organic matter and nutrient status are dependent on establishment and decay of organisms after 1980. While it is difficult to untangle the edaphic and climatic influences on tree growth in these two settings, comparing growth-climate relationships [23] across these two sites may provide insight into the future relative dominance of conifers regardless of edaphic factors. Although numerous studies have investigated community succession in the areas surrounding Mount St. Helens [4], and on conifer growth rates in response to changing climates [21,24,25,26,27,28], examining the early successional conifer growth rates in these primary succession landscapes after forty years represents a major knowledge gap. As primary succession environments give way to forests, understanding differences in growth rates of trees has the potential to significantly improve our understanding of primary succession. Likewise, a comparison of growth rates of these species of conifers in the context of annual temperature and precipitation can provide insight into the relative importance of annual variation in climate in determining succession outcomes. Mount St. Helens represents one of the few locations on Earth where primary succession has been consistently measured for over four decades, and now development of forests dominated by conifers represents a new phase.
Here, we utilize height, whorl count, and internode length measurements in recolonizing conifers at Mount St. Helens (WA, USA) to address the following questions: (i) How do conifer species differ in age, height, and growth rate? (ii) How do species’ heights, growth rates, and/or ages differ in two primary succession areas (debris avalanche and pyroclastic flow) separated by more than 300 m elevation (~750 m–1100 m elevation) (iii) Do conifer species’ annual growth rates differ in response to temporal variations in climate over the last five years? Answers to these questions fill an important gap in understanding current and future patterns in conifer succession in a post-disturbance volcanic environment.

2. Materials and Methods

2.1. Study Area

The study took place within Mount St. Helens National Volcanic Monument (hereafter MSHNVM; 46.245278° N, 122.196389° W) in the southern Cascade Mountains of Washington (USA). The study was conducted from late May to early June 2021 at two iconic primary succession disturbance zones within the monument (Figure 1).
The debris avalanche is characterized by rolling hills and mounds, and these sites are located along the Hummocks Trail (~750 m elevation). This disturbance event was the largest debris avalanche in recorded history [1], and the event destroyed or buried all vegetation and soils associated with the previous forest [3,4,29]. The pyroclastic flow is on the north side of the mountain (and is referred to as the “pumice plain”; ~1100 m elevation). The area is roughly 20 km2 in size and is the result of multiple distinct deposits during and after the initial 1980 eruption [1]. The pyroclastic deposits are generally 10–200 m thick and hence resulted in destruction and burial of all vegetation in the previous forest [1,30,31].

2.2. Climate Data

The climate at MSHNVM is considered wet maritime, characterized by cool, wet winters with an average minimum temperature in January of 4.4 °C and warm, dry summers with an average maximum temperature in July of 22.2 °C [32]. For the period of historical record from 1986 to 2020, mean annual temperature was 6.54 °C [33]. For water years 2015 to 2019, mean precipitation accumulation was 2430 mm and mean temperature was 7.67 °C.
Measurements of mean temperature, annual precipitation, and estimates of vapor pressure deficit were also interpolated for each site and year using the PRISM data explorer platform [34]. Recent yearly growth increments were calculated from internode distances of the five most recent whorls. Measurements were aligned with the prior year’s data, to account for lagged tree growth response to the previous year’s conditions for a full growth cycle.

2.3. Sampling Procedure

Sampling points were selected haphazardly along prominent trails with a target of 30 trees of each of the three most dominant species in each study area. Sample points were selected at approximately 80 m intervals along each trail (Figure 1). At each point, the closest available tree within 5 m was selected. In cases where there was no sample tree present, the sample point was abandoned and travel continued to the next potential point. At each sample point, a line was sighted between the nearest individual of each of the following measured species: noble fir (Abies procera; ABPR), Douglas-fir (Pseudotsuga menziesii; PSME) and lodgepole pine (Pinus contorta; PICO). To calculate species frequency, all conifer individuals were tallied in a 4.5 m radius. If a target conifer species was not present within 100 m of the first two species at a sample point, that species was not recorded for that location. Six samples near the debris avalanche were accidentally selected outside of the debris avalanche disturbance zone but were included in the analysis due to similarities in location, abiotic environment, and a lack of surviving vegetation or legacy dead trees.
Tree age was calculated using the whorl count method [35] summarized as follows: each whorl count was one year, and bottom stubs/knots were counted as one year with the assumption that the lowermost branches were lost. An additional two years were added to every tree to account for initial growth since all three species are unbranched at germination and the first recognizable whorl may not occur until the third year of growth [35]. Care was taken to avoid counting false whorls and/or possible lammas growth (where a secondary flush occurs during the same year). Measurements of each tree included number of whorls and height (m). These measurements were then used to calculate age (whorls + 2) and linear average growth rate over the life of the tree (height/age).
While the above measurements can give average height growth rates over the age of the tree, individual yearly growth rates may be better for determining responses of trees to yearly variation in annual climate. Accordingly, we also sampled trees for annual growth in the most recent five years. A subset of 7–12 trees were randomly selected for each species and site, and measured for internode length (m) between whorls over the past five years of growth from the leader through the top five whorls. This resulted in annual data for 11 A. procera, 7 P. contorta, and 11 P. menziesii at the debris avalanche, and 10 A. procera, 9 P. contorta, and 9 P. menziesii at the pyroclastic flow.
Tree height (m) was measured using a laser rangefinder/hypsometer (OPTi-Logic InSight 400 LH, Opti-Logic Corporation, Tullahoma, TN, USA) and/or a height pole, which extended to form a measuring stick of length equal to the height of the tree being measured. Two researchers measured each tree—one person at the base of the tree extending the pole until it was even with the top of the tree and the second person sighting alignment with the top of the tree from a distance. In the case of trees that were taller than the measurement pole, measurements were taken with the laser hypsometer, repeated by two users, and averaged for accuracy. All annual increment data were measured directly using the height measurement pole.

2.4. Statistical Analysis

First, a χ2 test was used to determine if counts of the tree species sampled differed by sample area. For this analysis, all species encountered in the survey were used. In all analyses below, only species whose age and annual height growth could be reliably measured using measurement of stem increments were used (the three most abundant species in the survey-Abies procera, Pinus contorta, and Pseudotsuga menziesii).
Normality tests (Shapiro–Wilk) showed that age and growth increment data were distributed non-normally, but variances were equal based on a Levene test. Accordingly, we used a permutative resampling ANOVA approach in the R package (v. 4.5.0) lmPerm (Wheeler and Torchiano 2016 [36]) to determine effects of site (debris flow or pyroclastic flow) and species (Abies procera, ABPR; Pinus contorta, PICO; and Pseudotsuga menziesii, PSME) on the response variables of tree age, tree height, and growth rate. Pairwise comparisons were made on all individual pairs following the same approach, but with the α-level (0.05) adjusted for significance by dividing α by the number of pairwise comparisons performed (in most cases two or three when term interactions were not significant, accounting for two sites and three species).
To determine differences in annual growth rate increment among species and sites in the context of recent climatic variables in the most recent five-years, we used a repeated-measures linear mixed-effect REML model. All response variables were log-transformed prior to analysis to meet normality assumptions. Individual trees were treated as random effects, and both species and site were fixed effects alongside the continuous variables of year, annual precipitation, average annual temperature, and maximum annual VPD. Interaction effects between species and precipitation, temperature, and VPD were also included. Models were constructed and tested using the lme4 package [37] in R along with the lmerTest package [38] to produce type III ANOVA tables. Post hoc comparisons were carried out using Tukey’s HSD tests and comparison of slopes using nonoverlapping 95% confidence intervals (in the case of interaction effects). In all cases an ⍺ = 0.05 was used for significance.

3. Results

The total tree count sampled across the debris avalanche was 281 and 191 across the pyroclastic flow. Psuedotsuga menziesii represented 51% of the total conifers sampled in the debris avalanche zone, and 52% of trees sampled in the pyroclastic flow zone, while Abies procera represented 30% at the debris avalanche, and 27% at the pyroclastic flow (Figure 2). Pinus contorta represented 15% of the total conifers sampled at the debris avalanche and only 6% of trees sampled at the pyroclastic flow. Two additional species not used in the rest of the study were also encountered in our dataset, and these are consistent with occurrence in other studies of woody vegetation at the study site [3,9]. Tsuga heterophylla (Raf.) Sarg. represented only 4% at the debris avalanche, and 15% at the pyroclastic flow. Finally, there was a single individual of Thuja plicata Donn ex D. Don recorded on the debris avalanche. Other conifer species such as Picea engelmannii Parry ex Engelm. and Pinus monticola Douglas ex D. Don are documented at our study sites [3,9], but were not measured in our sampling. The Bray–Curtis Dissimilarity Index was calculated at 0.27 between the two sites, and a χ2 analysis showed the proportion of species sampled differed significantly between the two sites (χ2 = 25.96, p < 0.0001), specifically for the presence of P. contorta and T. heterophylla.
We were able to clearly identify age and height for 29 A. procera, 19 P. contorta, and 32 P. menziesii on the debris avalanche and 36 A. procera, 10 P. contorta, and 36 P. menziesii on the pyroclastic flow. Patterns of conifer age, height, and growth rates varied both among species and at the two different locations at MSH. Mean age for A. procera was 15.89 ± 0.52 (SE) yr, mean age for P. contorta was 14.31 ± 0.78 yr, and mean age for P. menziesii was 13.70 ± 0.51 yr (Figure 3A). Accordingly, many extant trees may have established between 2004 and 2007, reflecting a burst in establishment noted in the master’s thesis by Birchfield in 2010 [9].
Tree species (p < 0.001), site (p < 0.001), and their interaction (p = 0.0064) influenced tree age (Figure 3A and Table 1). Overall, trees were older on the debris avalanche, and species were ranked from oldest to youngest as: A. procera, P. contorta, P. menziesii. Post hoc pairwise differences in age among species indicated A. procera on the debris avalanche were significantly older than P. menziesii on the pyroclastic flow (p = 0.008), and overall (p = 0.005).
Both tree species (p < 0.0001) and site (p < 0.0001), but not their interaction (p = 0.8039), influenced tree height (Figure 3B and Table 1). Similar to the pattern of older trees found on the debris avalanche, we saw taller trees on at the debris avalanche, but the pattern in height is opposite the pattern in age across species, ranked from tallest to shortest as: P. menziesii, P. contorta, A. procera. Mean height for A. procera was 2.05 ± 0.26 m, mean height for P. contorta was 2.49 ± 0.40 m, and mean height for P. menziesii was 3.68 ± 0.26 m (Figure 3). Pseudotsuga menziesii were taller than A. procera (p < 0.0001), and trees were also taller on the debris avalanche than on the pyroclastic flow (p < 0.0001). Other post hoc comparisons were not significant (p > 0.05).
Finally, tree species (p < 0.0001), site (p < 0.0001), and their interaction (p = 0.01) influenced average lifetime growth rates (Table 1 and Figure 3C). Overall, trees had higher growth rates on the debris avalanche (0.22 ± 0.013 SE m yr−1) than on the pyroclastic flow (0.15 ± 0.01 SE m yr−1; Figure 3C). Species were ranked by height growth rate from fastest to slowest as: P. menziesii (0.24 ± 0.016 SE m yr−1), P. contorta (0.16 ± 0.014 SE m yr−1), A. procera (0.12 ± 0.009 SE m yr−1). Pseudotsuga menziesii on the debris avalanche had significantly faster growth rates than A. procera (p = 0.001). On the pyroclastic flow, P. menziesii had significantly faster growth rates than both A. procera (p = 0.001) and P. contorta (p = 0.02; Figure 3C).
Analysis of the most recent five years’ annual increment growth in the context of climatic variables (Table 2) demonstrated significance for three effects: species (F(2, 262.8) = 12.74, p < 0.0001), year (F(1, 271.3) = 13.30, p = 0.0003), and the interaction of species and temperature (F(2, 262.4) = 6.98, p = 0.001). Non-significant factors included precipitation (F(1, 233.5) = 0.39, p = 0.5330), temperature (F(2, 9.64) = 2.93, p = 0.1186), maximum VPD (F(2, 257) = 0.12, p = 0.7264), and interactions between species and precipitation (F(2, 262.3) = 0.67, p = 0.5124), and species and maximum VPD (F(2, 255.6) = 0.32, p = 0.7245). The significant interaction between species and temperature occurred because of contrasting patterns of annual growth rates and average annual temperature between A. procera and P. contorta. While A. procera increased growth with average annual temperature, P. contora decreased in growth (albeit weakly) as average annual temperature increased (Figure 4).
Finally, to account for potential lag effects where the current year’s growth is affected by the previous year’s conditions, we also ran the above model with all climate data lagged by one year. The resulting model only produced significant effects for interactions between species and temperature (F(2, 261.9) = 3.35, p = 0.0364) and species and precipitation (F(2, 259.9) = 9.0, p = 0.0002). All other effects were non-significant (p > 0.05). The nature of the interaction with temperature was similar to non-lagged data (but weaker), where A. procera increased growth slightly with the past-year’s temperature (r2 = 0.04, p < 0.05), while P. contora showed a slight decline (r2 = 0.08, p = 0.014), but P. menziesii did not change (p = 0.386). With precipitation, A. procera and P. menziesii declined with increasing precipitation in the previous year (r2 = 0.18, p < 0.001 and r2 = 0.06, p = 0.018, respectively), and P. contora did not change (p = 0.120).

4. Discussion

This study supports a non-linear model for succession of conifers, without a predictable transition from early seral to late seral species through time [6,7,31,39,40]. Instead, differences in species establishment and growth rates result in one species establishing first (A. procera), and then others increasing faster due to rapid height growth (e.g., P. menziesii; Table 1 and Table 2, and Figure 3). Interestingly, Larson [41] showed A. procera outcompeted P. menziesii in mixed stands in eastern Washington. Interactions through time with temperature make predictions even more complex, especially when individual species growth (i.e., A. procera) may increase with increasing temperatures (Figure 4). As a result, succession from a barren substrate to an eventual conifer forest may approximate a “boat race”, where neither an early-lead, nor a mid-race lead guarantees eventual dominance. The data we present here provide a valuable basis for future growth surveys and succession studies, which are far from over in an ecosystem recovering from a 45-year-old volcanic disturbance.
The significant differences in age, height, and growth rates among species were consistent with our hypotheses that species would have significantly different growth patterns and rates in different disturbance areas. Abies procera was, on average, two years older than P. menziesii, suggesting different colonization processes or vectors for seed dispersal. Abies procera apparently arrived at the debris avalanche earlier, and then P. menziesii only more recently colonized both sites. In spite of this, average A. procera height was only half that of P. menziesii due to the significantly slower growth rate of A. procera. Of the three species included in the study, P. menziesii has the fastest reported growth rate, resulting in the difference in age and height distribution as a common phenomenon where their ranges overlap. This may be partially due to higher water use efficiency and water uptake rates by P. menziesii, especially in relation to P. contorta, as shown in other studies [42]. Pinus contorta had a growth rate, age and height intermediate to A. procera and P. menziesii, and at some sites (i.e., the pyroclastic flow) significantly lower than P. menziesii. Nevertheless, P. contorta was found less frequently during sampling, which contributed to a disproportionately smaller sample size for analysis.
All species had significantly higher growth rates in the debris avalanche zone when compared with the pyroclastic flow zone. While these locations both represent iconic primary succession environments, they likely differ edaphically and climatically. Both areas have limited soil structure, and a mixed tephra substrate [1]. The debris avalanche area may potentially offer more fertile substrate for tree growth due to a potentially more porous mixed size class granularity, and the potential for organic residues that survived the blast [3]. Nevertheless, our study was unable to untangle edaphic effects from the climatic differences between sites (the debris avalanche sites were generally lower elevation and warmer). Our analysis of climate effects may offer more insight. Although we measured recent incremental growth for a proportionally limited number of individuals per species per site, our data shows that tree species growth does vary significantly from year to year in response to mean annual temperature. In the analysis of the most recent five years’ increment growth from 2015 to 2020 paired with climate factors, P. contorta showed significantly higher annual incremental growth where average temperatures were warmer and declined in growth with increasing temperature. Abies procera, in contrast, increased annual incremental growth with increasing annual temperature. Pinus contorta is known to thrive on pumice substrate specifically, where competition is less of a factor [10], consistent with our observations of lower vegetative cover at the pyroclastic flow site where average annual temperatures are also lower. Pseudotsuga menziesii was not sensitive to temperature, and may be more likely to be constrained by water availability than energy limitations or growing season [19]. Climate change predictions that reduce summer precipitation [13,25] may have significant implications for continued growth of this highly productive species in this post-disturbance environment.
Other climate and edaphic metrics might prove more predictive of growth than the three metrics that we used here (average temperature, precipitation, and max VPD). For example, water balance variables (such as radiation, temperature, soil moisture, and actual and potential evapotranspiration) explicitly link climate and plant processes [43,44], and should be explored in future studies. The 1980 eruption resulted in pumice and tephra deposits mostly from 10 to 200 m deep, with particle sizes often from 2 to 10 cm or finer [1,31]. As such, moisture availability can be very limited in sites where pumice accumulations are deep, grain sizes are larger, and precipitation drains quickly. In contrast, large deposits of finer material below coarse material and lapilli [45] could retain water at depth and prevent evaporation at the surface (effectively serving as a mulch). These factors could differ between the two distinct zones studied here. Young trees could struggle to access deeper water sources below surface pumice and other tephra. Very young conifers are also highly affected by both drought and herbivory pressure by elk, which likely represented significant negative impacts on initial growth following the 1980 eruption [46]. Volcanic tephra has been shown to reduce growth and establishment for conifer seedlings [47], and at least part of this effect is edaphic. The lack of any organic-carbon-rich topsoil in the tephra-impacted area and the relatively coarse texture of the pyroclastic material can contribute to water stress for colonizing conifers [48]. Initially after the eruption, plant growth on the Pumice Plain was entirely confined to erosion channels [49]. Tephra from Mount St. Helens can have a low water infiltration rate [50], and may have reduced photosynthesis in establishing plants early after the eruption where depth of tephra was associated with reduced sapling growth [51], but even in some recent record-setting droughts, some tephra affected sites failed to experience expected plant water stress [52], and other studies have shown longer term increases in conifers and even increased diameter growth in response to tephra deposits [8,53]. The highly variable texture, cover, depth, and erodibility of tephra on this landscape (and across disturbance zones) may be a source of variation in our results and represents a promising avenue of future study.
Climate change influences forests both directly and indirectly; direct effects occur through changes in temperature and precipitation, and indirect effects include changes to the occurrence of disturbances. The rate of forest regrowth following disturbance is strongly influenced by climate [13,54,55]. In the Pacific Northwest, temperatures have increased ~1 °C between 1900 and the 1960s and are projected to warm further. Warming temperatures and changing precipitation patterns during the growing season will directly and indirectly affect ecosystem productivity, carbon storage, and soil moisture availability [54,55,56]. Climate directly affects vegetation growth, reproduction, and survival which includes tree growth rates, phenology, and productivity [25]. Consequently, climate also indirectly affects other plant-relevant factors, such as wind; high winds have been shown to decrease leader growth rates and increase water stress [57].

5. Conclusions

The deposits from the 1980 eruption of Mount St. Helens provide an opportunity to examine revegetation, tree regeneration, and soil development over time because we can date the disturbance and the start of regeneration. Prior to the eruption, forests were conifer-dominant mature forests [58], and conifer regrowth represents the start of a potential trajectory back to a forested state. These terrestrial ecosystems at Mount St. Helens were destroyed and replaced with a nutrient poor pumice and ash, and the succession trajectory is still unclear [7]. Our data demonstrate differences in species and climate relationships which could be important for predicting these future trajectories. Variation in relative growth rates through time may also change for these conifer species as weather and microclimate interactions materialize under climate change Monitoring conifer growth here provides valuable insight into the rate of succession in a young terrestrial ecosystem; if trees can be expected to continue establishment at similar rates and frequencies in the coming years, then these measurements and surveys could be used to model and map the future of the Mount St. Helens landscape as it returns to a more natural post-disturbance state.

Author Contributions

Conceptualization, D.G.F., A.R., M.D.F. and C.B.; methodology, D.G.F., A.R., M.D.F. and C.B.; formal analysis, D.G.F., A.R., M.D.F. and C.B.; resources, D.G.F. and C.J.L.; data curation, D.G.F.; writing—original draft preparation, A.R., M.D.F. and C.B.; writing—review and editing, D.G.F. and C.J.L.; visualization, D.G.F., A.R., M.D.F. and C.B.; supervision, D.G.F.; project administration, D.G.F.; funding acquisition, D.G.F. and C.J.L. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by National Science Foundation grant DEB-1836387 to C.J.L. and internal funds for undergraduate research and academic programs at The Evergreen State College.

Data Availability Statement

All data and will be available following publication at osf.oi under the title “Data for Conifer Growth Patterns in Primary Succession Locations at Mount St. Helens” and the link: https://osf.io/d3yhk/?view_only=194f2d35ce0047a995624efb3ef04653, accessed on 26 July 2025.

Acknowledgments

We thank the academic program Field Ecology 2021 under the supervision of D.G.F. at The Evergreen State College for helping in the process of project design and implementation and extensive review. We would also like to thank The Evergreen State College Science Instructional Technicians and appreciate the resources available through the Evergreen Science Support Center. All research was conducted on land historically and currently stewarded by the Cowlitz Indian Tribe and the Confederated Tribes and Bands of the Yakama Nation. The USDA Forest Service provided a permit for research at the Mount St. Helens National Volcanic Monument.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

References

  1. Lipman, P.W.; Mullineaux, D.R. The 1980 Eruptions of Mount St. Helens, Washington; Geological Survey Professional Paper 1250; United States Geological Survey: Reston, VA, USA, 1981; p. 867. [Google Scholar]
  2. Crisafulli, C.M.; Dale, V.H. Ecological Responses at Mount St. Helens: Revisited 35 Years After the 1980 Eruption; Springer: New York, NY, USA, 2018; ISBN 978-1-4939-7449-8. [Google Scholar]
  3. Dale, V.H.; Campbell, D.R.; Adams, W.M.; Crissafulli, C.M.; Dains, V.I.; Frenzen, P.M.; Holland, R.F. Plant Succession on the Mount St. Helens Debris-Avalanche Deposit. In Ecological Responses to the 1980 Eruption of Mount St. Helens; Dale, V.H., Swanson, F.J., Crisafulli, C.M., Eds.; Springer: New York, NY, USA, 2005; pp. 59–73. [Google Scholar]
  4. Dale, V.H.; Crisafulli, C.M.; Swanson, F.J. 25 Years of Ecological Change at Mount St. Helens. Science 2005, 308, 961–962. [Google Scholar] [CrossRef]
  5. del Moral, R.; Titus, J.H. Primary Succession on Mount St. Helens: Rates, Determinism, and Alternative States. In Ecological Responses at Mount St. Helens: Revisited 35 Years After the 1980 Eruption; Crisafulli, C.M., Dale, V.H., Eds.; Springer: New York, NY, USA, 2018; pp. 127–148. ISBN 978-1-4939-7451-1. [Google Scholar]
  6. Del Moral, R.; Titus, J.H.; Cook, A.M. Early Primary Succession on Mount St. Helens, Washington, USA. J. Veg. Sci. 1995, 6, 107–120. [Google Scholar] [CrossRef]
  7. Chang, C.C.; Halpern, C.B.; Antos, J.A.; Avolio, M.L.; Biswas, A.; Cook, J.E.; del Moral, R.; Fischer, D.G.; Holz, A.; Pabst, R.J.; et al. Testing Conceptual Models of Early Plant Succession across a Disturbance Gradient. J. Ecol. 2019, 107, 517–530. [Google Scholar] [CrossRef]
  8. Fischer, D.G.; Antos, J.A.; Biswas, A.; Zobel, D.B. Understorey Succession after Burial by Tephra from Mount St. Helens. J. Ecol. 2019, 107, 531–544. [Google Scholar] [CrossRef]
  9. Birchfield, M. Thirty Years of Conifer Establishment in Volcanic Primary Succession at Mount St. Helens: Patterns and Factors Affecting Establishment—Washington State University. Master’s Thesis, Washington State University, Vancouver, WA, USA, 2011. [Google Scholar]
  10. Franklin, J.F.; Dyrness, C.T. Natural Vegetation of Oregon and Washington; Gen. Tech. Rep. PNW-GTR-008; U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station: Portland, OR, USA, 1973; Volume 427. [Google Scholar]
  11. Stachowicz, J.J. Mutualism, Facilitation, and the Structure of Ecological Communities: Positive Interactions Play a Critical, but Underappreciated, Role in Ecological Communities by Reducing Physical or Biotic Stresses in Existing Habitats and by Creating New Habitats on Which Many Species Depend. BioScience 2001, 51, 235–246. [Google Scholar] [CrossRef]
  12. Binkley, D.; Fisher, R.F. Ecology and Management of Forest Soils; John Wiley & Sons: Hoboken, NJ, USA, 2019; ISBN 978-1-119-45565-3. [Google Scholar]
  13. Dale, V.H.; Joyce, L.A.; McNulty, S.; Neilson, R.P.; Ayres, M.P.; Flannigan, M.D.; Hanson, P.J.; Irland, L.C.; Lugo, A.E.; Peterson, C.J.; et al. Climate Change and Forest Disturbances. BioScience 2001, 51, 723–734. [Google Scholar] [CrossRef]
  14. Haugo, R.D.; Halpern, C.B. Vegetation Responses to Conifer Encroachment in a Western Cascade Meadow: A Chronosequence Approach. Can. J. Bot. 2007, 85, 285–298. [Google Scholar] [CrossRef]
  15. Halpern, C.B.; Antos, J.A.; Rice, J.M.; Haugo, R.D.; Lang, N.L. Tree Invasion of a Montane Meadow Complex: Temporal Trends, Spatial Patterns, and Biotic Interactions. J. Veg. Sci. 2010, 21, 717–732. [Google Scholar] [CrossRef]
  16. Franklin, J.F. Abies procera Rehd. Noble Fir. In Silvics of North America: V1. Conifers; Burns, R., Honkala, B., Eds.; U.S. Department of Agriculture, Forest Service: Washington, DC, USA, 1990; ISBN 978-0-16-027145-8. [Google Scholar]
  17. Harrington, C.A.; Murray, M.D. Patterns of Height Growth in Western True Firs. In Proceedings of the Biology and Management of True Fir in the Pacific Northwest Symposium, Seattle-Tacoma, WA, USA, 24–26 February 1981; College of Forest Resources, University of Washington: Seattle, WA, USA, 1982; Volume 24, pp. 209–214. [Google Scholar]
  18. Jagodzinski, A.M.; Banaszczak, P. Stem Volume and Aboveground Woody Biomass in Noble Fir [Abies procera Rehder] Stands in the Rogow Arboretum [Poland]. Acta Sci. Polonorum. Silvarum Colendarum Ratio Ind. Lignaria 2010, 9, 9–24. [Google Scholar]
  19. Littell, J.S.; Peterson, D.L.; Tjoelker, M. Douglas-Fir Growth in Mountain Ecosystems: Water Limits Tree Growth from Stand to Region. Ecol. Monogr. 2008, 78, 349–368. [Google Scholar] [CrossRef]
  20. Chuine, I.; Aitken, S.N.; Ying, C.C. Temperature Thresholds of Shoot Elongation in Provenances of Pinus Contorta. Can. J. For. Res. 2001, 31, 1444–1455. [Google Scholar] [CrossRef]
  21. Chuine, I.; Rehfeldt, G.E.; Aitken, S.N. Height Growth Determinants and Adaptation to Temperature in Pines: A Case Study of Pinus Contorta and Pinus Monticola. Can. J. For. Res. 2006, 36, 1059–1066. [Google Scholar] [CrossRef]
  22. Voight, B.; Janda, R.; Glicken, H.; Douglass, P.M.; Nolan, M.; Hoblitt, R. Catastrophic Rockslide-Avalanche of May 18, 1980, Mount St. Helens Volcano, Washington (abs); U.S. Geological Survey, U.S. Department of the Interior: Reston, VA, USA, 1980; Volume 12, p. 542. [Google Scholar]
  23. Littell, J.S.; Peterson, D.L. A Method for Estimating Vulnerability of Douglas-Fir Growth to Climate Change in the Northwestern, U.S. For. Chron. 2005, 81, 369–374. [Google Scholar] [CrossRef]
  24. St Clair, B.; Howe, G.T. Genetic Maladaptation of Coastal Douglas-Fir Seedlings to Future Climates. Glob. Change Biol. 2007, 13, 1441–1454. [Google Scholar] [CrossRef]
  25. Chmura, D.J.; Anderson, P.D.; Howe, G.T.; Harrington, C.A.; Halofsky, J.E.; Peterson, D.L.; Shaw, D.C.; St. Clair, J.B. Forest Responses to Climate Change in the Northwestern United States: Ecophysiological Foundations for Adaptive Management. For. Ecol. Manag. 2011, 261, 1121–1142. [Google Scholar] [CrossRef]
  26. Cortini, F.; Comeau, P.G.; Boateng, J.O.; Bedford, L.; McClarnon, J.; Powelson, A. Effects of Climate on Growth of Lodgepole Pine and White Spruce Following Site Preparation and Its Implications in a Changing Climate. Can. J. For. Res. 2011, 41, 180–194. [Google Scholar] [CrossRef]
  27. Rehfeldt, G.E.; Leites, L.P.; Bradley St Clair, J.; Jaquish, B.C.; Sáenz-Romero, C.; López-Upton, J.; Joyce, D.G. Comparative Genetic Responses to Climate in the Varieties of Pinus Ponderosa and Pseudotsuga Menziesii: Clines in Growth Potential. For. Ecol. Manag. 2014, 324, 138–146. [Google Scholar] [CrossRef]
  28. Jansons, A.; Dzenis, J.; Matisons, R.; Samariks, V.; Jansone, B. Intra-Annual Height Growth Dynamics of Scots and Lodgepole Pines and Its Relationship with Meteorological Parameters in Central Latvia. Agron. Res. 2020, 18, 410–421. [Google Scholar] [CrossRef]
  29. Major, J.J.; Crisafulli, C.M.; Frenzen, P.; Bishop, J. After the Disaster: The Hydrogeomorphic, Ecological, and Biological Responses to the 1980 Eruption of Mount St. Helens, Washington. In Volcanoes to Vineyards: Geologic Field Trips through the Dynamic Landscape of the Pacific Northwest; O’Connor, J.E., Dorsey, R.J., Madin, I.P., Eds.; Geological Society of America: Boulder, CO, USA, 2009; Volume 15, ISBN 978-0-8137-0015-1. [Google Scholar]
  30. Adams, A.B.; Dale, V.H.; Smith, E.P.; Kruckeberg, A.R. Plant Survival, Growth Form and Regeneration Following the 18 May 1980 Eruption of Mount St. Helens, Washington. Northwest Sci. 1987, 61, 160–170. [Google Scholar]
  31. Del Moral, R.; Wood, D.M. Early Primary Succession on the Volcano Mount St. Helens. J. Veg. Sci. 1993, 4, 223–234. [Google Scholar] [CrossRef]
  32. Swanson, F.J.; Crisafulli, C.M.; Yamaguchi, D.K. Geological and Ecological Settings of Mount St. Helens Before May 18, 1980. In Ecological Responses to the 1980 Eruption of Mount St. Helens; Dale, V.H., Swanson, F.J., Crisafulli, C.M., Eds.; Springer: New York, NY, USA, 2005; pp. 13–26. ISBN 978-0-387-23868-5. [Google Scholar]
  33. NRCS Spirit Lake SNOTEL Weather Station. Available online: https://wcc.sc.egov.usda.gov/nwcc/site?sitenum=777 (accessed on 23 June 2025).
  34. PRISM Climate Group Oregon State University, PRISM. Available online: https://prism.oregonstate.edu/explorer/ (accessed on 21 June 2024).
  35. Avery, T.E.; Burkhart, H.E. Forest Measurements, 5th ed.; Waveland Press: Long Grove, IL, USA, 2015; ISBN 978-1-4786-2974-0. [Google Scholar]
  36. Wheeler, B.; Torchiano, M. lmPerm: Permutation Tests for Linear Models. R Package Version 2.1.5. 2025. Available online: https://github.com/mtorchiano/lmperm (accessed on 26 July 2025).
  37. Bates, D.; Mächler, M.; Bolker, B.; Walker, S. Fitting Linear Mixed-Effects Models Using Lme4. J. Stat. Softw. 2015, 67, 1–48. [Google Scholar] [CrossRef]
  38. Kuznetsova, A.; Brockhoff, P.B.; Christensen, R.H.B. lmerTest Package: Tests in Linear Mixed Effects Models. J. Stat. Softw. 2017, 82, 1–26. [Google Scholar] [CrossRef]
  39. Cattelino, P.J.; Noble, I.R.; Slatyer, R.O.; Kessell, S.R. Predicting the Multiple Pathways of Plant Succession. Environ. Manag. 1979, 3, 41–50. [Google Scholar] [CrossRef]
  40. Chang, C.C.; Turner, B.L. Ecological Succession in a Changing World. J. Ecol. 2019, 107, 503–509. [Google Scholar] [CrossRef]
  41. Larson, B.C. Development and Growth of Even-Aged Stands of Douglas-Fir and Grand Fir. Can. J. For. Res. 1986, 16, 367–372. [Google Scholar] [CrossRef]
  42. Smit, J.; van den Driessche, R. Root Growth and Water Use Efficiency of Douglas-Fir (Pseudotsuga menziesii (Mirb.) Franco) and Lodgepole Pine (Pinus contorta Dougl.) Seedlings. Tree Physiol. 1992, 11, 401–410. [Google Scholar] [CrossRef]
  43. Lookingbill, T.R.; Urban, D.L. Gradient Analysis, the next Generation: Towards More Plant-Relevant Explanatory Variables. Can. J. For. Res. 2005, 35, 1744–1753. [Google Scholar] [CrossRef]
  44. Stephenson, N. Actual Evapotranspiration and Deficit: Biologically Meaningful Correlates of Vegetation Distribution across Spatial Scales. J. Biogeogr. 1998, 25, 855–870. [Google Scholar] [CrossRef]
  45. Kuntz, M.A.; Rowley, P.D.; MacLeod, N.S.; Reynolds, R.L.; McBroome, L.A.; Kaplan, A.M.; Lidke, D.J. Petrography and Particle-Size Distribution of Pyroclastic-Flow, Ash-Cloud, and Surge Deposits. In U.S. Geological Survey Professional Paper; U.S. Geological Survey, U.S. Department of the Interior: Reston, VA, USA, 1981; Volume 1250, pp. 525–539. [Google Scholar]
  46. Dale, V.H.; Adams, W.M. Plant Reestablishment 15 Years after the Debris Avalanche at Mount St. Helens, Washington. Sci. Total Environ. 2003, 313, 101–113. [Google Scholar] [CrossRef]
  47. Caruso, J.L.; Sumida-Stevens, S.; Sovonick-Dunford, S.; Winget, G.D.; Jayasimhulu, K. Influence of Mount St. Helens Volcanic Ash on Growth and Abscisic Acid in Douglas-Fir Seedlings. J. Plant Physiol. 1990, 137, 229–232. [Google Scholar] [CrossRef]
  48. Antos, J.A.; Zobel, D.B. Recovery of Forest Understories Buried by Tephra from Mount St. Helens. Vegetatio 1986, 64, 103–111. [Google Scholar] [CrossRef]
  49. Collins, B.D.; Dunne, T. Effects of Forest Land Management on Erosion and Revegetation after the Eruption of Mount St. Helens. Earth Surf. Processes Landf 1988, 13, 193–205. [Google Scholar] [CrossRef]
  50. Pierson, T.C.; Major, J.J. Hydrogeomorphic Effects of Explosive Volcanic Eruptions on Drainage Basins. Annu. Rev. Earth Planet. Sci. 2014, 42, 469–507. [Google Scholar] [CrossRef]
  51. Hinckley, T.M.; Imoto, H.; Lee, K.; Lacker, S.; Morikawa, Y.; Vogt, K.A.; Grier, C.C.; Keyes, M.R.; Teskey, R.O.; Seymour, V. Impact of Tephra Deposition on Growth in Conifers: The Year of the Eruption. Can. J. For. Res. 1984, 14, 731–739. [Google Scholar] [CrossRef]
  52. Watt, A.J.; Fischer, D.G.; Antos, J.A.; Zobel, D.B. Leaf-Level Physiology in Four Subalpine Plants in Tephra-Impacted Forests during Drought. Can. J. For. Res. 2018, 48, 431–441. [Google Scholar] [CrossRef]
  53. Miller, A.E.; Sherriff, R.L.; Berg, E.E. Effects of the Novarupta (1912) Eruption on Forests of South-Central Alaska: Clues from the Tree-Ring Record. Alsk. Park Sci. 2012, 11, 74–77. [Google Scholar]
  54. Littell, J.S.; Oneil, E.E.; McKenzie, D.; Hicke, J.A.; Lutz, J.A.; Norheim, R.A.; Elsner, M.M. Forest Ecosystems, Disturbance, and Climatic Change in Washington State, USA. Clim. Change 2010, 102, 129–158. [Google Scholar] [CrossRef]
  55. Case, M.J.; Lawler, J.J. Relative Vulnerability to Climate Change of Trees in Western North America. Clim. Change 2016, 136, 367–379. [Google Scholar] [CrossRef]
  56. Case, M.J.; Johnson, B.G.; Bartowitz, K.J.; Hudiburg, T.W. Forests of the Future: Climate Change Impacts and Implications for Carbon Storage in the Pacific Northwest, USA. For. Ecol. Manag. 2021, 482, 118886. [Google Scholar] [CrossRef]
  57. Rees, D.J.; Grace, J. The Effects of Wind on the Extension Growth of Pinus Contorta Douglas. For. Int. J. For. Res. 1980, 53, 145–153. [Google Scholar] [CrossRef]
  58. Gallant, A.L. Revegetation-Microhabitat Relations in the Blast Zone of Mount St. Helens. Master’s Thesis, Oregon State University, Corvallis, OR, USA, 1985. [Google Scholar]
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Figure 1. This map of the study area shows the regions of Mount St. Helens National Volcanic Monument characterized by multiple volcanic disturbance zones including the debris avalanche and pyroclastic flow zones. Sampling locations are indicated by purple dots (see methods; 82 sites in the pyroclastic flow and 80 sites in the debris avalanche).
Figure 1. This map of the study area shows the regions of Mount St. Helens National Volcanic Monument characterized by multiple volcanic disturbance zones including the debris avalanche and pyroclastic flow zones. Sampling locations are indicated by purple dots (see methods; 82 sites in the pyroclastic flow and 80 sites in the debris avalanche).
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Forests 16 01245 g002
Figure 2. The distribution of tree species surveyed in two distinct areas recovering from the 1980 eruption of Mount St. Helens. The debris avalanche is largely northwest of the mountain. The pyroclastic flow is largely due north. Species surveyed included ABPR (Abies procera), PICO (Pinus contorta), PSME (Pseudotsuga menziesii), and TSHE (Tsuga heterophylla).
Figure 2. The distribution of tree species surveyed in two distinct areas recovering from the 1980 eruption of Mount St. Helens. The debris avalanche is largely northwest of the mountain. The pyroclastic flow is largely due north. Species surveyed included ABPR (Abies procera), PICO (Pinus contorta), PSME (Pseudotsuga menziesii), and TSHE (Tsuga heterophylla).
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Figure 3. The patterns in tree species (A) age, (B) height, and (C) linear average annual growth rate in two major disturbance zones at Mount St. Helens 40 years after the eruption. Box-plots show median values and quartiles. Debris avalanche (debris) and pyroclastic flow (pyro) zones are the two sites represented. Four-letter species codes are ABPR (Abies procera), PICO (Pinus contorta), and PSME (Pseudotsuga menziesii).
Figure 3. The patterns in tree species (A) age, (B) height, and (C) linear average annual growth rate in two major disturbance zones at Mount St. Helens 40 years after the eruption. Box-plots show median values and quartiles. Debris avalanche (debris) and pyroclastic flow (pyro) zones are the two sites represented. Four-letter species codes are ABPR (Abies procera), PICO (Pinus contorta), and PSME (Pseudotsuga menziesii).
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Figure 4. Most recent 5-year annual height growth rates for 2016 through 2020 (log-scale) by temperature. Points represent species averages at a given annual temperature. Years with shared average temperatures at a given site are represented with shared points for each species. Error bars represent one standard error. Abies procera showed a significant increase with temperature, while P. contora declined, resulting in a significant temperature by species interaction in a REML model (F(2, 265.5) = 6.89, p = 0.001). Simple linear regressions are also shown between temperature and growth rate by species (A. procera r2 = 0.25; P. contora r2 = 0.06).
Figure 4. Most recent 5-year annual height growth rates for 2016 through 2020 (log-scale) by temperature. Points represent species averages at a given annual temperature. Years with shared average temperatures at a given site are represented with shared points for each species. Error bars represent one standard error. Abies procera showed a significant increase with temperature, while P. contora declined, resulting in a significant temperature by species interaction in a REML model (F(2, 265.5) = 6.89, p = 0.001). Simple linear regressions are also shown between temperature and growth rate by species (A. procera r2 = 0.25; P. contora r2 = 0.06).
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Table 1. Permutative ANOVA results for comparison of age, height, and growth rate for three species of conifers in two locations at Mount St. Helens.
Table 1. Permutative ANOVA results for comparison of age, height, and growth rate for three species of conifers in two locations at Mount St. Helens.
VariableFactordfSums of SquaresMean SquarePermutationsp
AgeSpecies2175.8287.915000<0.0001
Location157.7457.7395000<0.0001
Species × Location211.995.99750000.0064
Residuals1562771.6217.767
Height (m)Species296.0648.0285000<0.0001
Location167.467.3995000<0.0001
Species × Location21.510.754510.8039
Residuals156658.984.224
Growth Rate (m yr−1)Species20.501680.250845000<0.0001
Location10.181850.1818515000<0.0001
Species × Location20.004510.00225450000.01
Residuals1561.40860.009029
Table 2. Table of climate conditions from 2016 to 2020 and average growth for the three primary tree species examined.
Table 2. Table of climate conditions from 2016 to 2020 and average growth for the three primary tree species examined.
SiteYear Mean Air Temp. (°C)Precipitation
(mm yr−1)		Max
VPD (kPa)		Pseudotsuga menziesii Mean 5-Year Growth
(m yr−1)		Abies procera
Mean 5-Year Growth (m yr−1)		Pinus contorta
Mean 5-Year Growth (m yr−1)
Debris
Avalanche		20168.129247.20.160.140.09
20177.628048.130.250.190.11
20188.121018.450.250.150.15
20197.417806.880.300.170.14
20207.827157.790.360.280.13
Pyroclastic Flow20167.134686.150.270.050.16
20176.735487.180.220.060.16
20187.125507.40.210.070.20
20196.421246.130.260.050.15
20206.7294870.380.130.19
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Rose, A.; Blackketter, C.; Fisher, M.D.; LeRoy, C.J.; Fischer, D.G. Conifer Growth Patterns in Primary Succession Locations at Mount St. Helens. Forests 2025, 16, 1245. https://doi.org/10.3390/f16081245

AMA Style

Rose A, Blackketter C, Fisher MD, LeRoy CJ, Fischer DG. Conifer Growth Patterns in Primary Succession Locations at Mount St. Helens. Forests. 2025; 16(8):1245. https://doi.org/10.3390/f16081245

Chicago/Turabian Style

Rose, Alicia, Cody Blackketter, Marisa D. Fisher, Carri J. LeRoy, and Dylan G. Fischer. 2025. "Conifer Growth Patterns in Primary Succession Locations at Mount St. Helens" Forests 16, no. 8: 1245. https://doi.org/10.3390/f16081245

APA Style

Rose, A., Blackketter, C., Fisher, M. D., LeRoy, C. J., & Fischer, D. G. (2025). Conifer Growth Patterns in Primary Succession Locations at Mount St. Helens. Forests, 16(8), 1245. https://doi.org/10.3390/f16081245

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