Dynamics of diameter and height increment of Norway spruce and Scots pine in southern Finland

Key message

Onset and cessation of radial and height increment of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) in southern Finland were independent phenomena. They both contributed to the increment period duration, which was a more crucial factor defining the magnitude of annual radial and height increment.

Context

Phenology of diameter and height increment is a critical component of growth, also contributing to damage and survival of trees.

Aims

We quantified annual variation in intra-annual tracheid production and height increment of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.).

Methods

The number of tracheids and the day of the year for the onset and cessation of tracheid production were monitored from microcores collected repeatedly during growing seasons 2001–2012 in southern Finland. Weekly height increment was also measured in an adjacent sapling stand in 2008–2012.

Results

The first tracheids in pine were found around mid-May and in spruce a week later. The cessation of the tracheid production occurred during the last week of August for both tree species. Increment onset and cessation were independent phenomena, both contributing to the magnitude of tracheid production via increment period duration, which appeared to be a more crucial factor defining the number of tracheids. Duration of the height increment period was also related to shoot length but the connection was less tight than the link between the duration of tracheid production and the number of tracheids. A thermal threshold around 100 d.d. (degree days) was found for the onset of radial increment. No single environmental factor triggered the cessation of tracheid production, but in some years, soil water availability appeared to play a role.

Conclusion

The results indicate that extending growing seasons due to the climatic warming may increase growth in the Finnish forests.

     

Tree mortality in drought-stressed mixed-conifer and ponderosa pine forests, Arizona, USA

We monitored tree mortality in northern Arizona (USA) mixed-conifer and ponderosa pine (Pinus ponderosa Dougl. ex Laws) forests from 1997 to 2007, a period of severe drought in this area. Mortality was pervasive, occurring on 100 and 98% of 53 mixed-conifer and 60 ponderosa pine plots (1-ha each), respectively. Most mortality was attributable to a suite of forest insects, mediated by drought stress. The number of trees dying from 2002 to 2007 was more than 200% greater than the number dying from 1997 to 2002 in mixed-conifer forest and 74% greater in ponderosa pine forest. Extent of mortality was spatially variable in both forest types. Median cumulative mortality (the ratio of dead to live trees) increased by approximately 53 and 65% in mixed-conifer and ponderosa pine forests, respectively, from 2002 to 2007. Median mortality rates from 2002 to 2007 were approximately 2.0% year⁻¹ in mixed-conifer forest (range = 0-28.5%) and 0.4% year⁻¹ in ponderosa pine forest (range = 0-13.6%). Mortality rates generally were not strongly related to either elevation or stand density. Mortality was nonrandom with respect to tree size classes and species. Proportions of trees dying were greatest in the largest size classes, particularly in mixed-conifer forest, where mortality in the largest size class exceeded 22% from 2002 to 2007. Mortality in mixed-conifer forest was particularly pronounced for quaking aspen (85%) and white fir (28%), the least drought tolerant species present. These results provide an early glimpse of how these forest types are likely to respond to predicted climate changes in the southwestern USA. They suggest that these forests are not resilient to climate change, and that treatments to increase resilience to climate change may be appropriate. Research on causes of spatial heterogeneity in extent of mortality might suggest valuable approaches to aid in increasing resilience.     

Predicting survival of planted Douglas-fir and ponderosa pine seedlings on dry,low-elevation sites in southwestern Oregon

Four equations were developed for predicting the probability of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] and ponderosa pine (Pinus ponderosa Dougl. ex Laws.) survival for the first (0–1) and first to third (1–3) growing seasons after applying mulching, scalping, or artificial shading (shade cards) treatments in plantations in southwestern Oregon, U.S.A. Variables describing conifer size, levels of competing vegetation, presence of silvicultural treatments, site factors, and climate factors were collected from 13 sites ranging from 0 to 6 years after planting and examined as potential predictors of survival. Age, stem diameter, a competition index for shrubs, severity of growing season at time of treatment, average annual precipitation, aspect, and slope angle were predictors of Douglas-fir survival during 0–1 and 1–3 growing seasons after treatment; the presence of silvicultural treatments was also a predictor only during the first growing season after treatment. Age, aspect, and slope angle were predictors of ponderosa pine survival over both 0–1 and 1–3 growing seasons after treatment; height-diameter ratio, competition indices for herbs, shrubs, and hardwoods, silvicultural treatment, severity of growing season at time of treatment, and average annual precipitation were also predictors only during the first growing season after treatment; crown width was a predictor of survival only during 1–3 growing seasons after treatment. When significant in the models, predicted probability of survival increases with treatments, less severe weather conditions, diameter, crown width, age, and precipitation; probability decreases with increasing height-diameter ratio and competition indices for herbs, shrubs, and hardwoods.     

Bark beetle-caused mortality in a drought-affected ponderosa pine landscape in Arizona,USA

Extensive ponderosa pine (Pinus ponderosa Dougl. ex Laws.) mortality associated with a widespread severe drought and increased bark beetle (Coleoptera: Curculionidae, Scolytinae) populations occurred in Arizona from 2001 to 2004. A complex of Ips beetles including: the Arizona fivespined ips, Ips lecontei Swaine, the pine engraver beetle, Ips pini (Say), Ips calligraphus (Germar), Ips latidens (LeConte), Ips knausi Swaine and Ips integer (Eichhoff) were the primary bark beetle species associated with ponderosa pine mortality. In this study we examine stand conditions and physiographic factors associated with bark beetle-caused tree mortality in ponderosa pine forests across five National Forests in Arizona. A total of 633 fixed-radius plots were established across five National Forests in Arizona: Apache-Sitgreaves, Coconino, Kaibab, Prescott, and Tonto. Prior to the bark beetle outbreak, plots with mortality had higher tree and stocking compared with plots without pine mortality. Logistic regression modeling found that probability of ponderosa pine mortality caused by bark beetles was positively correlated with tree density and inversely related with elevation and tree diameter. Given the large geographical extent of this study resulting logistic models to estimate the likelihood of bark beetle attack should have wide applicability across similar ponderosa pine forests across the Southwest. This is particularly true of a model driven by tree density and elevation constructed by combining all forests. Tree mortality resulted in significant reductions in basal area, tree density, stand density index, and mean tree diameter for ponderosa pine and for all species combined in these forests. Most of the observed pine mortality was in the 10–35 cm diameter class, which comprise much of the increase in tree density over the past century as a result of fire suppression and grazing practices. Ecological implications of tree mortality are discussed.     

Individual tree height increment model for managed even-aged stands of ponderosa pine throughout the western United States using linear mixed effects models

A height increment model is developed and evaluated for individual trees of ponderosa pine throughout the species range in western United States. The data set used in this study came from long-term permanent research plots in even-aged, pure stands both planted and of natural origin. The data base consists of six levels-of-growing stock studies supplemented by initial spacing and other permanent-plot thinning studies for a total of 310 plots, 34,263 trees and 122,082 observations. Regression analysis is the most commonly used statistical method in forest modeling. However, research studies with repeated measurements are common in forestry and other biological disciplines. We choose the mixed models instead of the regression analysis approach because it allows for proper treatment of error terms in a repeated measures analysis. The model is well behaved and possessed desirable statistical properties. Our goal is to present a single height increment model applicable throughout the geographic range of ponderosa pine in the United States and by using only data from long-term permanent plots on sites capable of the productivity estimated by Meyer [Meyer, W.H., 1938. Yield of Even-aged Stands of Ponderosa Pine. US Department of Agriculture Technical Bull. 630].     

美国怀俄明州西黄松林分碳库和经济收益比较

A forest carbon (C) sequestration project was conducted to evaluate the economic incentives that would be required by landowners to engage in C trading under different management regimes. Costs associated with joint management for C sequestration and timber would be valuable for establishing sound forest C trading systems. In this study, we calculated the C yield and amortized value of three Wyoming, ponderosa pine stands. The management practices examined were, unmanaged, even-aged (regeneration after clear-cut) and uneven-aged (selectively harvested). Costs and revenues associated with three stands were converted into 2006 real dollars using the all commodity producer price index to facilitate a comparison among the net revenues of three stands. Net revenues were annualized using a conservative annual interest rate of 4.5%. Our even-aged stand had the highest annual average C yield of 2.48 Mg·ha⁻¹·a¹, whereas, the uneven-aged stand had the lowest C accumulation (1.98 Mg·ha⁻¹·a⁻¹). Alternatively, the even-aged stand had the highest amortized net return of $276·ha⁻¹·a⁻¹ and the unmanaged stand had the lowest net return of $276·ha⁻¹·a⁻¹ and the unmanaged stand had the lowest net return of 64 ·ha⁻¹·a⁻¹. On the plots examined, an annual payment of $22 for each additional Mg of C sequestered would encourage a change from uneven aged management to an unmanaged stand that sequesters additional C, in the absence of transactions costs.     

Individual tree diameter increment model for managed even-aged stands of ponderosa pine throughout the western United States using a multilevel linear mixed effects model

A diameter increment model is developed and evaluated for individual trees of ponderosa pine throughout the species range in the United States using a multilevel linear mixed model. Stochastic variability is broken down among period, locale, plot, tree and within-tree components. Covariates acting at tree and stand level, as breast height diameter, density, site index, and competition indices are included in the model as fixed effects in order to explain residual variability. The data set used in this study came from long-term permanent research plots in even-aged, pure stands both planted and of natural origin. The data base consists of six levels-of-growing stock studies supplemented by initial spacing and other permanent-plot thinning studies for a total of 310 plots, 34,263 trees and 153,854 observations. Regression analysis is the preferred technique used in growth and yield modeling in forestry. We choose the mixed effects models instead of the regression analysis approach because it allows for proper treatment of error terms in a repeated measures analysis framework. Regional growth and yield models exist for ponderosa pine. However, data collection and analysis procedures differ. As a result, comparisons of growth responses that may be due to geographic variation of the species are not possible. Our goal is to present a single distance-independent diameter increment model applicable throughout the geographic range of ponderosa pine in the United States and by using only data from long-term permanent plots on sites capable of the productivity estimated by Meyer [Meyer, W.H., 1938. Yield of Even-Aged Stands of Ponderosa Pine. US Department of Agriculture Technical Bulletin 630].     

云南松树高——胸径生长关系模型

树高与胸径是林分调查的两个主要因子,同时也是衡量林分生长情况的两个重要指标。文章通过两组不同的调查数据,建立三个模型,利用SPSS软件求解得到了不同林分的云南松的树高和胸径的关系模型都是Power模型,用该模型推算平均树高,对森林调查具有十分重要的意义。     

Phenological variation in height and diameter growth in provenances and families of loblolly pine

The phenology of 5- and 6-year old loblolly pine (Pinus taeda L.) trees was studied over two different growing seasons (1993 and 94) in southwest Georgia. These trees were from 7–9 open-pollinated families from each of four different provenances planted at two locations. The provenances were: Atlantic Coastal Plain (eastern SC), Gulf Hammock (north FL), Lower Gulf (south AL, MS) and Upper Gulf (north AL, MS). Provenances did not vary as to when height growth started in spring, but showed very significant differences for the date of growth cessation in fall. The Gulf Hammock source grew the most and also had the longest height growth period, while the Upper Gulf source was first to stop height growth and had the least annual height increment. Provenances were also significantly different for the date of cessation of diameter growth (a difference of 22 days between Gulf Hammock and Upper Gulf), and the order of cessation was the same as for height. Families within provenances were significantly different for date of cessation of height growth and diameter growth. When family means were considered across provenances, there was a correlation of 0.69 (p-value = 0.0001) between annual height increment and date of height growth cessation. There was a weaker association between faster growth and a longer growing season within provenances.     

Effects of branch height on leaf gas exchange,branch hydraulic conductance and branch sap flux in open-grown ponderosa pine

Recent studies have shown that stomata respond to changes in hydraulic conductance of the flow path from soil to leaf. In open-grown tall trees, branches of different heights may have different hydraulic conductances because of differences in path length and growth. We determined if leaf gas exchange, branch sap flux, leaf specific hydraulic conductance, foliar carbon isotope composition (delta13C) and ratios of leaf area to sapwood area within branches were dependent on branch height (10 and 25 m) within the crowns of four open-grown ponderosa pine (Pinus ponderosa Laws.) trees. We found no difference in leaf gas exchange or leaf specific hydraulic conductance from soil to leaf between the upper and lower canopy of our study trees. Branch sap flux per unit leaf area and per unit sapwood area did not differ between the 10- and 25-m canopy positions; however, branch sap flux per unit sapwood area at the 25-m position had consistently lower values. Branches at the 25-m canopy position had lower leaf to sapwood area ratios (0.17 m2 cm-2) compared with branches at the 10-m position (0.27 m2 cm-2) (P = 0.03). Leaf specific conductance of branches in the upper crown did not differ from that in the lower crown. Other studies at our site indicate lower hydraulic conductance, sap flux, whole-tree canopy conductance and photosynthesis in old trees compared with young trees. This study suggests that height alone may not explain these differences.     

Ten-year responses of ponderosa pine growth,vigor, and recruitment to restoration treatments in the Bitterroot Mountains,Montana, USA

Little is known about ponderosa pine forest ecosystem responses to restoration practices in the Northern Rocky Mountains, USA. In this study, restoration treatments aimed at approximating historical forest structure and disturbances included modified single-tree selection cutting, with and without prescribed burning. We compared the effectiveness of restoration treatments on growth, vigor, and composition of recruitment responses with untreated controls. We used a randomized block design to detect treatment differences in mean individual tree basal area increment (BAInc10), growth efficiency (GE), and recruitment abundance between two restoration treatments (Cut-only and Cut-burn) and a Control. We further examined treatment effects by tree age-class (Young, Mature, Presettlement) using a spatial ANOVA model that incorporates the spatial autocorrelation among trees within experimental units. Ten years after implementing restoration treatments, mean individual tree BAInc10 and GE were significantly higher for treated units relative to Control units; all three age-classes benefited similarly from restoration treatments relative to the Control, with the greatest response in the Cut-only and moderate response in the Cut-burn. When treated units were compared, Cut-burn negatively affected BAInc10 and GE relative to Cut-only. Presettlement trees responded positively to treatment relative to the Control, particularly for BAInc10, demonstrating the potential of these old trees to respond to reduced competition. The Cut-burn treatment, in contrast, negatively affected the BAInc10 and GE response of postsettlement trees when compared to Cut-only. Restoration treatments did not reduce the amount of Douglas-fir recruits. In addition, the recruitment of both ponderosa pine and Douglas-fir species was associated with the proximate cover of woody debris in Cut-only and Control treatments. Finally, special consideration needs to be taken for spring Cut-burn treatments, which appeared to dampen growth and vigor, relative to Cut-only, particularly for Young and Mature trees, and increased recruitment of ponderosa pine and particularly Douglas-fir.     

Conserving genetic diversity in ecological restoration: a case study with ponderosa pine in northern Arizona,USA

Our study used allozyme analyses to evaluate potential impacts of ecological restoration treatments on genetic diversity of ponderosa pine (Pinus ponderosa var. scopulorum) populations within the Fort Valley Experimental Forest near Flagstaff, AZ. Allele frequencies varied among pre-settlement clumps, with trees more closely related to each other within clumps. This clumpy spatial stand structure typical of reference conditions thus represents “genetic neighborhoods” and suggests restoration of clumpy versus more evenly dispersed trees in naturally regenerating stands will protect evolutionary genetic patterns. Compared to pre-settlement populations, post-settlement trees had slightly greater heterozygosity, and allelic richness and allele frequencies varied between these two age groups. These genetic differences could have resulted from different selective conditions under which the two age groups became established. Genetic diversity of populations created using different selection criteria for residual post-settlement trees did not vary but simulated removal of 75% of post-settlement trees decreased allelic richness. Maintaining more clumps created from post-settlement populations with higher tree densities across the landscape would be more effective at conserving allelic richness. Overall results of this study indicate use of genetic structure and diversity can help guide restoration treatments to help ensure adaptive potential is conserved.     

Understory vegetation response after 30 years of interval prescribed burning in two ponderosa pine sites in northern Arizona,USA

Southwestern USA ponderosa pine (Pinus ponderosa C. Lawson var. scopulorum Engelm.) forests evolved with frequent surface fires and have changed dramatically over the last century. Overstory tree density has sharply increased while abundance of understory vegetation has declined primarily due to the near cessation of fires. We examined effects of varying prescribed fire-return intervals (1, 2, 4, 6, 8, and 10 years, plus unburned) on the abundance and composition of understory vegetation in 2007 and 2008 after 30+ years of fall prescribed burning at two ponderosa pine sites. We found that after 30 years, overstory canopy cover remained high, while understory plant canopy cover was low, averaging <12% on all burn intervals. We attributed the weak understory response to a few factors – the most important of which was the high overstory cover at both sites. Graminoid cover and cover of the major grass species, Elymus elymoides (squirreltail), increased on shorter fire-return intervals compared to unburned plots, but only at one site. Community composition differed significantly between shorter fire-return intervals and unburned plots at one site, but not the other. For several response variables, precipitation levels appeared to have a stronger effect than treatments. Our findings suggest that low-severity burn treatments in southwestern ponderosa pine forests, especially those that do not decrease overstory cover, are minimally effective in increasing understory plant cover. Thinning of these dense forests along with prescribed burning is necessary to increase cover of understory vegetation.     

Influence of moisture stress and induced resistance in ponderosa pine,Pinus ponderosa Dougl. ex. Laws,on the pine sawfly,Neodiprion autumnalis Smith

Plant moisture stress is artificially maintained for ponderosa pine, Pinus ponderosa Dougl. ex Laws, seedlings using polyethylene glycol. Stressed seedlings produce significantly lower amounts of needle nitrogen, phenols, and tannins than non-stressed seedlings. Field tests reveal that previously damaged foliage is a significantly poorer food source for the pine sawfly, Neodiprion autumnalis Smith (Hymenoptera: Diprionidae), than non-damaged foliage. Field studies further indicate that the effect of induction by defoliation is more important than the effect of stress level. These results are discussed in terms of their potential impact on future studies on preferential selection by herbivores of stressed host plants.     

A comparison of three approaches to modeling leaf gas exchange in annually drought-stressed ponderosa pine forests

We tested, compared and modified three models of stomatal conductance at the leaf level in a forest ecosystem where drought stress is a major factor controlling forest productivity. The models were tested against 2 years (1999 and 2000) of leaf-level measurements on ponderosa pine (Pinus ponderosa Dougl. ex Laws.) growing in the Mediterranean climate of California, USA. The Ball, Woodrow and Berry (1987) (BWB) model was modified to account for soil water stress. Among the models, results of the modified BWB model were in the closest agreement with observations (r2 = 0.71). The Jarvis (1976) model showed systematic simulation errors related to vapor pressure deficit (r2 = 0.65). Results of the Williams, Rastetter, Fernandes et al. (1996) (SPA) model showed the poorest correlation with empirical data, but this model has only one calibration parameter (r2 = 0.60). Sensitivity analyses showed that, in all three models, predictions of stomatal conductance were most responsive to photosynthetically active radiation and soil water content. Stomatal conductance showed little sensitivity to vapor pressure deficit in the Jarvis model, whereas in both the BWB and SPA models, vapor pressure deficit (or relative humidity) was the third most important variable. Parameterization of the SPA model was in accordance with the parameterization of the modified BWB model, although the two models differ greatly. Measured and modeled results indicate that stomatal behavior is not water conservative during spring; however, during summer, when soil water content is low and vapor pressure deficit is high, stomatal conductance decreases and, according to the models, intrinsic water- use efficiency increases.     

Introduction of ponderosa pine and Douglas-fir to Argentina

Patterns of shoot elongation of 2-yr seedlings from native North American populations of ponderosa pine and Douglas-fir were compared to those of Argentine land races originating from unknown provenances. The comparisons were conducted in Moscow, Idaho (USA), and suggested that the ponderosa pine land race was descended from a California provenance at low or middle elevations but that the growth potential of the land race was only mediocre in comparison to eight native populations. The Douglas-fir land race exhibited a relatively high growth potential in comparison to 19 native provenances and undoubtedly originated from a mild coastal environment. The results provide concrete recommendations for upgrading the growth potential of the Argentine land races by importing germ plasm of specific provenances.     

Post-1935 changes in forest vegetation of Grand Canyon National Park, Arizona, USA: Part 1 - ponderosa pine forest

Vegetation plots originally sampled in Grand Canyon National Park (GCNP), Arizona, USA in 1935 are the earliest-known, sample-intensive, quantitative documentation of forest vegetation over a Southwest USA landscape. These historical plots were located as accurately as possible and resampled in 2004 to document multi-decadal changes in never-harvested Southwestern forests. Findings for ponderosa pine forest (PPF) differed among three forest subtypes (dry, mesic, and moist PPF), indicating that understanding the ecology of PPF subtypes is essential for development of ecologically based management practices. Dry PPF, which is transitional with pinyon-juniper vegetation at low elevation, exhibited no changes from 1935 to 2004. Mesic PPF, the core subtype of PPF, had increased densities of total trees, ponderosa pine (Pinus ponderosa), and white fir (Abies concolor) in the 10-29.9 cm diameter class from 1935 to 2004 that may have induced decreased densities of larger ponderosa pines and total tree and ponderosa pine basal areas. Moist PPF, which is transitional with mixed conifer forest at high elevation, was the most dynamic PPF subtype with decreases from 1935 to 2004 in total density and total basal area that are largely attributable to decreases in quaking aspen (Populus tremuloides). Graphical synthesis of datasets with historical and modern values for density and basal area indicates that overall PPF (all subtypes combined) increased in sapling density of all species combined and conifers with canopy potential and decreased in density of quaking aspen trees since the late 19th century. PPF of GCNP has passed through an accretion phase of forest development with increases in density and, depending on PPF subtype and variable being examined, is at or past the point of inflection to recession of density and basal area. Increases in small diameter ponderosa pine and white fir from 1935 to 2004 portend potential additional accretion, but decreases in total basal area, density and basal area of quaking aspen, basal area of ponderosa pine, and density of larger diameter ponderosa pine indicate PPF has passed the inflection point from accretion to recession. Uncertainties about 19th-century PPF structure and composition and about future ecological and societal environments lead to the conclusion that resource managers of GCNP and other natural areas should consider a change in focus from the objective of achieving desired future conditions to an objective of avoiding undesired future conditions.     

Use of stump diameter to estimate diameter at breast height and tree volume for major pine species in El Salto, Durango (Mexico)

Foresters may require to estimate the diameter at breast height(d.b.h.) and the volume of trees that have been cut, and mayonly have available the stumps as an indicator of the size ofthe trees. In the present study, equations for predicting bothd.b.h. and volume from stump diameter inside bark were developedfor major pine species in the forest region of El Salto, Durango(Mexico). The d.b.h. was estimated with relatively high accuracywith a simple linear model. The tree volume was also estimatedwith high precision by use of an allometric equation. Weightedlinear and non-linear least squares methods were used to takeinto account the problem of heteroscedasticity observed in thevolume–stump diameter relationships. The results of thenon-linear extra sum of squares method and of the F tests indicatedthat species-based equations for estimating both d.b.h. andvolume from stump diameter are required.     

An approach to modeling the joint distribution of tree diameter and height data

Advantages of the application of bivariate distribution models to forest management cannot be overemphasized. However, there are quite a number of flexible statistical distributions not yet evaluated in their bivariate domains. Therefore, in this article, we evaluated the bivariate forms of some probability distribution models used in quantitative forestry. Six bivariate distributions were assessed: Burr XII (Burr XII-2), Dagum (Dagum-2), Kumaraswamy (Kum-2), the new Logit-Logistic-Dagum (LLD-2) distribution, Logit-Logistic (LL-2), and the much used Johnson’s S_BB. All models were constructed using the Plackett’s method except for the S_BB distribution. Appropriate constraints were imposed on the boundary parameters of the bivariate distributions using fractions derived from the Gumbel distribution. Models were fitted with maximum likelihood to the joint distribution of diameter and height data of Eucalyptus camaldulensis Dehn from 90 sample plots. Model assessment was based on negative log-likelihood (-ΛΛ), Corrected Akaike Information Criterion (AICc), Bayesian Information Criterion (BIC) and Hannan-Quinn Criterion (HQC). The result showed that the Johnson’s S_BB had the overall best performance. Their ranking order was: S_BB > LLD-2 > Burr XII-2 > Dagum-2 > LL-2 > Kum-2. These models can be used to simulate timber harvesting regime.