Non-thinned Stands Research Articles

Forest restoration treatments indirectly diversify pollination networks via floral- and temperature-mediated effects.

In North American conifer forests, a variety of federally initiated thinning programs are implemented to restore pre-European settlement forest structures, but these changes may impact ecosystem function via impacts on sensitive biotic communities. Across the wildland-urban interface of the Front Range region of Colorado, agencies associated with the Collaborative Forest Landscape Restoration Program (CFLRP) have implemented thinning treatments across thousands of hectares of ponderosa pine forest; here we leverage these treatments as an experimental framework to examine thinning effects on a pollinator community. We measured variation in forest structure and sampled bee community assemblages using multiple methods (trapping and netting) to compare bee biodiversity and patterns of floral visitation by bees (bee-flower networks) between mechanically thinned stands that were 3-10 years after treatment and nonthinned stands. Three key findings emerged: (1) Native bee abundance, richness, and diversity were 120%, 53%, and 37% greater, respectively, in thinned stands. In addition, nestedness, richness, and abundance of bee-flower interactions were all substantially higher in thinned stands, and there was increased functional redundancy in bee assemblages after thinning. (2) Structural equation modeling indicated that variation in temperature and floral abundance were mediated by canopy openness and correlated with bee richness and abundance, thereby indirectly driving variation in bee-flower interactions. (3) Four floral species (Penstemon virens, Cerastium arvense, Erysimum capitatum, and Geranium caespitosum) were identified as key connectors in bee-flower interaction networks, though these were not necessarily the most abundant flowering plants. Our analyses indicate that native bee α-diversity and bee-flower interactions positively responded to thinning treatments, and these effects were indirectly driven by canopy removal. We conclude that CFLRP treatments have conservation value for native bee communities. Further monitoring is warranted to evaluate the longevity of these effects.

Long-term growth effects of simulated-drought, mid-rotation fertilization, and thinning on a loblolly pine plantation in southeastern Oklahoma, USA

Loblolly pine (Pinus taeda L.) is the most productive commercial softwood species in the southeastern USA. More frequent drought due to climate change will likely alter loblolly pine productivity, especially in areas where the climate is already highly variable such as the Upper Gulf region of the south-central USA. In a long-term study, we examined the effects of drought treatment (30% throughfall exclusion), fertilization, and thinning on a loblolly pine plantation growing in southeastern Oklahoma, USA to determine how nutrient availability and stand density interact with drier conditions to affect productivity. Our treatments were applied at mid-rotation: throughfall reduction ages 5 to 13, fertilizer ages 5 and 10, and thinning age 10. Treatment effects on diameter and height increment depended on year, with drought treatment tending to decrease diameter and height growth in drier years and fertilization having a stronger positive effects on diameter growth in the years closely following fertilization events. The net effect on standing volume was that fertilization (+7%) and simulated-drought (−8%) countered each other by age 13. Positive fertilization effects were supported by increased foliar nitrogen (N) and phosphorus (P) concentrations, along with increased leaf area index (LAI, +14% measured age 12). Three and four years after thinning, diameter increment increased by 38%, and positive fertilization effects on gross current annual increment were greater in thinned compared to non-thinned stands. Basal area increment in drought-treated stands relative to non-drought-treated stands decreased more during drier years and exhibited recovery during wetter years. The fairly small growth decline in response to 30% throughfall reduction, positive fertilizer effects, and possible post-drought recovery indicate continued plantation viability in the future even at the drier, western fringe of loblolly pine’s commercial range.

OPTIMIZATION AND ECONOMIC ANALYSIS OF MULTIPRODUCTS OBTAINED FROM WOOD OF EUCALYPTUS STANDS UNDER DIFFERENT PRODUCTIVE CAPACITY CLASSES AND ROTATION AGES

The present study aimed to analyze the yield and economic viability of the destination, for lumber and energy, of the wood from non-thinned stands of the hybrid Eucalyptus urophylla x Eucalyptus grandis under different productive capacity class and whose production was projected by individual tree growth model to different ages. The simulation of the growth of individual trees was performed by applying the height and diameter growth, and mortality sub-models for three productive capacity classes: high, medium and low. The Kozak model was adjusted to study the stem taper and, in addition, used to optimize patterns for sawing logs and to produce lumber. The economic viability of the projects was evaluated by Net Present Value, Equivalent Periodic Benefit and risk analysis using the Monte Carlo method. It was observed that in areas with less productive capacity the volume of wood destined for energy was greater than 80% and, in areas with greater productive capacity the volume of lumber was greater than 26%. Economic indicators showed that the lumber production was viable at any of the studied rotation age. The risk analysis using the Monte Carlo method did not indicate the possibility of the project being unfeasible under the conditions analyzed. The quantity of different types of products obtained and the wood yield depends on the productive capacity class and age of the stand. The destination of the wood for multiproducts is the most viable option, regardless of the productive capacity class.

A stand level application of efficiency analysis to understand efficacy of fertilization and thinning with drought in a loblolly pine plantation

Loblolly pine (Pinus taeda L.) is the most important and productive commercial timber species in the southern USA. Common plantation management practices such as fertilization and thinning could become inefficient and economically disadvantageous given anticipated climate change effects, such as increased drought severity, especially in the drier Upper Gulf region of the south-central USA. To calculate technical and economic efficiency, we used data envelopment analysis (DEA) to assess the ability of fertilized, thinned, and drought-induced loblolly pine plots in southeastern Oklahoma (n = 32) to turn volume growth and stand density (inputs) into timber products- pulpwood, chip-n-saw, sawtimber- and stored carbon (outputs) across 21, 26, and 31-year rotations. The highest efficiencies were for the fertilized-thinned treatments. We found that thinned stands remain technically, economically, and overall efficient as rotation age increased. Non-thinned stands had lower efficiencies than thinned stands and exhibited a 28% decrease in overall efficiency between ages 21 and 31. Drought decreased overall efficiency by at least 11% when rotation age was 26 years or longer. Fertilization with drought decreased overall efficiency on average by 24%. The results reiterate the importance of thinning to efficiently mediate drought conditions and should remain a staple of plantation silviculture. Results also indicate that fertilization is not likely to help ameliorate drought impacts, from an efficiency standpoint. Study results will benefit practitioners in gauging active forest management decisions and their likely outcomes from a resource efficiency perspective.

Thinning Effects on Biomass and Carbon Stock for Young Taiwania Plantations

Forests play an important role as carbon sinks by sequestrating carbon through photosynthesis. Thinning treatments have large impacts on carbon storage, in addition to strengthening quality and quantity of plantations. This study analyzed the effects of different thinning treatments on carbon stocks in both individual trees and stands of Taiwania (Taiwania cryptomerioides) plantations. Repeated field measurements and allometric equations were used to calculate total C storage and sequestration rates of live trees. The results of this study showed that the total carbon stock of stands with thinning treatments was less than that of the non-thinned stands. The non-thinned 23-year old stands had an estimated carbon stock of 96.8 Mg C ha−1, which is higher than the carbon stock found in either medium- (84.1 Mg C ha−1) or heavily-thinned (74.7 Mg C ha−1) treatment plots of the same age. If the objective of Taiwania plantations was to store large amounts of carbon in the young growth stage, without regard to the initial rate of storage, a better option is no-thinning. However, the medium thinned forests seem to be more promising for carbon sequestration than the no-thinned forests if a longer period is considered.

Stand density management and blue carbon stock of monospecific mangrove plantation in Bohol, Philippines

Abstract Blue carbon pertains to carbon stock that is stored by marine ecosystems including mangrove forest. Density and blue carbon stock assessment was conducted covering mature Rhizophora stylosa Griff. plantations in Bohol, Philippines. Three stand types were assessed: thinned mature stand (0.34 tree m−2 at 55 years old; 35 ha); non-thinned mature stand (1.2 tree m−2 at 55 years old; 20 ha) and young stand (2.6 tree m−2 at 20 years old; 150 ha). These plantations were initially established with a plant spacing of 0.5 m × 0.5 m. Non-destructive plot sampling technique was used to account biomass and carbon stocks of trees and sediments. Five (5) sample plots measuring 200 m2 were allocated for each stand type. Results showed that the total carbon stock of plantations amassed to 64.5 ktC or 236.6 ktCO2e. More than half (at least 54%) of this stock is imbedded in sediment. Individual accounts showed that carbon stock was largest in non-thinned stand with 435.2 tC ha−1, followed by thinned stand (408.5 tC ha−1) and young stand (276.8 tC ha−1). There was no significant difference between thinned and non-thinned mature stands carbon stocks. Such finding suggested the potential of having thinning intervention. Following the self-thinning rule of 1.1 to 1.3 tree m−2, the local community can harvest as much as 423 trees ha−1 yr−1 for 35 years starting at the plantation age of 20 years. Further, the additional carbon stock between the ages 20 to 55 years could reach about 580 tCO2e ha−1 with an economic value of USD 2,962 ha−1. With this potential benefits, it is recommended that Banacon Island should pursue a carbon offset project for its plantations.

Effects of Simulated Ice Storm Damage on Midrotation Loblolly Pine Stands

We simulated ice damage by shooting a portion of live crown from midrotation (ages 14–16 years) loblolly pine (Pinus taeda L.) stands in southeastern Oklahoma to study the postice damage effects in thinned, thinned-pruned, and nonthinned-nonpruned stands. Four years after damage, diameter growth was faster in the thinned plots than the nonthinned plots as expected. Relative basal area growth (rBAgrowth; basal area growth over the 4-year period/initial basal area) decreased as the fraction of live crown ratio loss (LCRloss) increased in all stands. While the slope of the relationship was similar among silvicultural treatments, the intercept for the nonthinned plots was lower. The result was that a 50% loss of live crown predicted rBAgrowth reductions of 28% in thinned and 64% in nonthinned plots. Canopy opening due to the simulated damage did not have a positive growth effect on the undamaged trees. We did not detect any differences in stem taper, probably because the study included data for only a 4-year recovery period. We conclude that stands can recover from moderate ice storm damage without large loss in production and that thinned stands have less reduction in basal area growth than nonthinned stands.

Overstory and understory relationships in longleaf pine plantations 14 years after thinning and woody control

To develop silvicultural strategies for restoring longleaf pine ( Pinus palustris Mill.) savannas, mortality and growth of overstory pines and midstory hardwoods and abundance and species richness of herbs were studied for 14 years after pine thinning and nonpine woody control. Pine cover in thinned stands was about half of that in nonthinned stands through year 5, but it lagged by only 8% and 3% in years 9 and 14, respectively, because of vigorous crown responses. Despite a cumulative mortality of 64% of hardwood stems from prescribed fires in years 0, 4, and 9, hardwood basal area in thinned stands (2.1 m2·ha–1) was three times that in nonthinned stands (0.7 m2·ha–1) in year 14. Thinning was associated with 13%–22% more cover and six to eight more species of herbs in years 3–8 but only 6% more cover and two more species in year 14 because of accelerated growth of pine cover and hardwood basal area. However, similar increases in cover and richness of herb species in the woody control treatment were retained through year 14 because it had sustained reductions in hardwood and shrub abundance. Silvicultural strategies that substantially delay encroachment by pines, hardwoods, and shrubs will be those most effective at retaining herb species in longleaf pine savannas, including planting pines at wide spacing, periodic thinning and woody control, and frequent burning.

Natural mortality in thinning and fertilisation experiments with pine and spruce in Sweden

Natural mortality in a 30-year period was examined in thinning and fertilisation experiments with 48 blocks in Scots pine ( Pinus sylvstris L.) and 23 blocks in Norway spruce ( Picea abies (L.) Karst.) with up to 12 different treatments. Of about 90,000 living trees at start of the experiments 18.7% were registered as dead by natural mortality in the 30-year observation period. In non-thinned stands about 20% of the volume growth disappeared by natural mortality, in thinned stands about 10%. In normally thinned pine stands (repeated thinning from below with moderate intensity) the annual mortality of the basal area at start of an average 7-year period was 0.34%. In spruce stands, on more fertile sites, the corresponding figure was about 0.6%. In an effort to model the mortality, severe damage not leading to final felling was identified in 1.7% of the observation periods. It was assumed that this part of the mortality, representing 24% of the total volume mortality, could be recovered by active thinning. The probability for severe damage increased sharply with stand top height, as shown in a logistic regression. The more sparse mortality was expressed as a function of site fertility, stand density, disturbance by thinning and form of treatment (thinned from above or below or non-thinned). The naturally dead trees were approximately of mean size in normally thinned stands while the self-thinning in non-thinned stands tended to occur amongst smaller than average trees. Diagrams were presented for basal area development and stem number reduction in the non-thinned stands.

Implementing Regional Locale and Thinning Response in the Loblolly Pine Height-Diameter Relationship

Abstract This study uses two regionwide data sets, one exemplified by intensive management and the other by nonintensive management, to investigate whether including regional locale and thinning response improves the loblolly pine height–diameter relationship. Results showed that including geographic coordinates as scaled variables, in addition to including a thinning response modifier, reduces the variability of an individual-tree height model compared with a baseline model without these covariates. Holding stand conditions constant, tree height for a given diameter will generally be greater at south and east locales within the natural range of loblolly pine, and thinning will lead to slightly greater tree heights. Equations that include geographic locale of the stand and a thinning modifier that incorporates amount of time since thinning are proposed. These equations can be used for thinned or nonthinned stands throughout the natural geographic range of the species.

The effects of prescribed fire and silvicultural thinning on the aboveground carbon stocks and net primary production of overstory trees in an oak-hickory ecosystem in southern Ohio

More than 70 years of fire suppression has influenced forest dynamics and led to the accumulation of fuels in many forests of the United States. To address these changes, forest managers increasingly seek to restore historical ecosystem structure and function through the reintroduction of fire and disturbance processes that mimic fire such as silvicultural thinning. In oak forests of eastern North America, prescribed fire and thinning are important tools used to facilitate oak ( Quercus spp.) regeneration and recruitment. The global scientific community is increasingly raising concerns about the accumulation of atmospheric CO 2, and its potential to impact global climate; therefore, activities such as prescribed fire and thinning that can influence the carbon balance of terrestrial ecosystems should be evaluated. We used field measurements and modeling with the PnET-II carbon balance model in oak forests of southern Ohio, USA, to (1) assess the efficacy of prescribed fire and silvicultural thinning in facilitating oak recruitment and regeneration, and (2) quantify the impacts of these treatments on aboveground carbon stocks and net primary production. Silvicultural thinning increased recruitment of maples, but oak recruitment was minimal. Prescribed burning caused an increase in the mortality rate of oaks’ major competitor ( Acer rubrum L.) in the overstory (stems ≥10 cm DBH), but oak mortality also increased following the burn treatments. Our measurements of stem growth suggest that the timing of the prescribed fires coincided with the initiation of growth in oaks, which may have created vulnerability in these species that are generally considered fire-resistant. The pre-treatment aboveground biomass of overstory trees was approximately 233 Mg/ha (Mg = 1 × 10 6 g). Prescribed burning had significant impacts on the mortality of stems; however, it had no significant effects on the aboveground net primary production (ANPP). Thinning removed approximately 30% of the aboveground biomass and resulted in significant but transient (1 year) reduction of ANPP (386 and 560 g C m −2 year −1 for thinned and non-thinned stands, respectively). In sum, thinning created recruitment opportunities in our study area, but these opportunities were captured by maples, and oak recruitment was minimal. Prescribed fire caused mortality in oaks and maples, and the oak mortality may have been related to the coincidence of the burn treatment and the initiation of oak stem growth. Finally, our data suggest that there is a transient impact of thinning on ANPP, but that there is no long-term effect of thinning and/or burning treatments on the aboveground carbon uptake in oak forests.

Influence of early thinning in broadleaved stands on development of remaining stems

Precommercial thinning studies were performed in eight hardwood stands in southern Sweden. Birch (Betula pendula Roth and B. pubescens Ehrh.) was the dominating tree species, but aspen (Populus tremula L.), black alder [Alnus glutinosa (L.) Gaertn.] and lime (Tilia cordata Mill.) were also present. Main stems were selected before thinning. Three treatments were applied in each stand: (1) no thinning (control), (2) standard thinning, and (3) strong thinning, i.e. leaving about two-thirds of the stem number of treatment 2. Each treatment was replicated three times on all sites. The development of the main stems were recorded during the five consecutive years. Breast height diameter and green crown size (length and width) developed significantly more slowly in the control treatment than in the thinned ones, whereas tree height development was little affected by treatment. Simulation of 10 years’ future growth from the time of the end of the study indicated that future diameter growth will be lower in initially non-thinned stands than in immediately thinned ones. The study results stress the importance for future growth of proper early silviculture in young broadleaved stands (i.e. early and high intensity thinning), a topic that has not been fully evaluated before.

The relationship between the density of Cryptomeria japonica stands and texture statistics derived from very high resolution imagery

To detect non-thinned stands using very-high-resolution imagery, we assessed the relationship between the texture statistics derived from the gray level co-occurrence matrix (GLCM) and the density of Cryptomeria japonica stands. Because it was difficult to make the condition, like stand age and slope, consistent using real images and stands, simulated images were used. The results showed that each texture statistic had a unique pattern of variation, owing to stand density. Moreover, the amount of thinning affected the texture statistics. Because the values of the texture statistics varied according to the amount of it even if the stand density was the same, it was indicated that it was difficult to predict stand density using the texture derived from GLCM. Nevertheless, it should be possible to extract stands that have not been thinned using the texture statistics from very-high-resolution imagery, especially the homogeneity and the angular second moment.

Growth and yield prediction using the modified Buckman model

A model to manage even-aged stands was developed using a modification of the Buckman model. Data from Eucalyptus urophylla and Eucalyptus cloeziana stands located in the Northern region of Minas Gerais State, Brazil were used in the formulation of the system. The proposed model generated precise and unbiased estimates in non-thinned stands.

Growth of Pinus elliottii, P. pinaster and P. radiata on coastal dune soils near Jervis Bay, Australian Capital Territory

Summary The growth of Pinus elliottii, P. pinaster and P. radiata on coastal dune soils is compared over a period of 23 y. Small growth responses to the application of urea, gypsum combined with potassium sulphate, dicalcium phosphate, and lime were obtained in the early phase of the experiment but they had dissipated at 15 y when the experiment was thinned. Immediately prior to thinning, stand basal area was 44.3, 33.9 and 39.4 m2 ha−1 for P. radiata, P. pinaster and P. elliottii respectively. In the second (late) phase of the experiment no growth response was obtained to superphosphate applied with or without urea to thinned or non-thinned stands. In non-thinned stands, P. radiata and P. elliottii had similar growth rates; both species grew faster than P. pinaster. Thinning reduced productivity of P. elliottii. The results are discussed in relation to the notion of Type 1 and Type 2 growth responses, problems in forecasting future growth from early measurements, and the problem of estimating changes in stand productivity between rotations.