Effects Of Thinning Treatments Research Articles

Legacy of thinning on woody species composition and structure in southern Appalachian Mountain hardwood forests: restoration implications

In the Appalachian Mountains, Liriodendron tulipifera monocultures are widespread, with these forests lacking both species and structural diversity. In this study, we developed models that described the effects of thinning treatments, conducted almost 60 years ago, on the density, composition, and functional identity of the woody understory in L. tulipifera forests. The woody understory of these thinned L. tulipifera forests was diverse, with the small seedling (<1.4 m), large seedling (≥1.4 m and <2.54 cm dbh), and sapling (≥2.54 and <12.7 cm) layers possessing 38, 32, and 23 species, respectively. Although model performance was low to moderate (r2 = 0.05–0.40), we found that legacy effects, alone or in combination with environmental variables, explained, in part, the variability associated with the density, composition, and functional identity of the small seedling, large seedling, and sapling size classes, with the relative influence of legacy versus environmental effects varying by metric and size class. Post‐thinning basal area and/or percent of basal area removed were not the primary legacy effects influencing the woody understory. Instead, legacy effects associated with species composition of the overstory before and/or after thinning along with average stem diameter post‐thinning, variation in stem diameter post‐thinning, and age at the time of thinning were more influential than density or thinning intensity. This study provides evidence that conserving species diversity during forest management activities can have positive long‐term effects on composition and function of the woody understory and increase restoration potential.

How Elemental Stoichiometric Ratios in Microorganisms Respond to Thinning Management in Larix principis-rupprechtti Mayr. Plantations of the Warm Temperate Zone in China

The stoichiometric ratios of elements in microorganisms play an important role in biogeochemical cycling and evaluating the nutritional limits of microbial growth, but the effects of thinning treatment on the stoichiometric ratio of carbon, nitrogen, and phosphorus in microorganisms remain unclear. We conducted research in a Larix principis-rupprechtti Mayr. plantation to determine the main factors driving microbial carbon (C): nitrogen (N): phosphorus (P) stoichiometry following thinning and the underlying mechanisms of these effects. The plantation study varied in thinning intensity from 0% tree removal (control), 15% tree reduction (high density plantation, HDP), 35% tree reduction (medium density plantation, MDP), and 50% tree reduction (low density plantation, LDP). Our results indicated that medium density plantation significantly increased litter layer biomass, soil temperature, and other soil properties (e.g., soil moisture and nutrient contents). Understory vegetation diversity (i.e., shrub layer and herb layer) was highest in the medium density plantation. Meanwhile, thinning had a great influence on the biomass of microbial communities. For example, the concentration of phospholipid fatty acids (PLFA) for bacteria and fungi in the medium density plantation (MDP) was significantly higher than in other thinning treatments. Combining Pearson correlation analysis, regression modeling, and stepwise regression demonstrated that the alteration of the microbial biomass carbon: nitrogen was primarily related to gram-positive bacteria, gram-negative bacteria, soil temperature, and soil available phosphorus. Variation in bacteria, actinomycetes, gram-positive bacteria, gram–negative bacteria, and soil total phosphorus was primarily associated with shifts in microbial biomass carbon: phosphorus. Moreover, changes in microbial biomass nitrogen: phosphorus were regulated by actinomycetes, gram-negative bacteria, and soil temperature. In conclusion, our research indicates that the stoichiometric ratios of elements in microorganisms could be influenced by thinning management, and emphasizes the importance of soil factors and microbial communities in driving soil microbial stoichiometry.

Thinning efficacy of metamitron on young 'RoHo 3615' (Evelina®) apple

To achieve a high quantity of premium class fruit, chemical thinning is an important component of crop load management in apples. For this purpose, the triazine-type photosynthetic inhibitor metamitron was registered for fruit thinning in Germany. Frequent studies demonstrated consistent thinning effects of metamitron on trees of different apple and pear cultivars. In the present study, the efficacy of metamitron applied at a low concentration (165 g ha−1) was investigated in 2016 and 2017 on young 'RoHo3615' apple trees, planted in 2014. The highest fruit set reduction was achieved when metamitron was applied twice. Single application, in contrast, led to variable results and pointed out the strong dependence of the thinning efficacy of metamitron on favourable weather conditions. Adding citric acid or the growth regulator prohexadione-Ca in combination with ammonium sulphate did not affect the thinning efficacy of metamitron. The fruit quality was high in any treatment and no effects of thinning treatment on fruit colouration or percentage of skin russeting were observed. Consequently, metamitron is an effective fruit thinning agent for young apple trees, which can be additionally used in combination with the mentioned substances, while maintaining a high fruit quality

Effect of thinning treatment on growth and wood density of Pinus taeda planted in Misiones, Argentina

The greatest increase in growth of the plantation may change the physical properties of wood, and therefore may decrease the wood quality for industry. The current paper aimed to evaluate the effect of thinning treatments on growth and wood density of Pinus taeda planted in Misiones, Argentina (25o 59’ S 54o24’ W). The plantation was established in 1985 with 1644 plants per hectare and three thinning intensity treatments were used (0%, 33% and 66% of the remaining basal area), under design randomized complete blocks (3 1 Ingeniero Forestal, Msc., Instituto Nacional de Tecnologia Agropecuaria (INTA), Av. El Libertador 2472, 3384, Montecarlo, Misiones, Argentina. ramartiarena@montecarlo.inta.gov.ar 2 Ingeniero Forestal, Msc., Instituto Nacional de Tecnologia Agropecuaria (INTA), Av. El Libertador 2472, 3384, Montecarlo, Misiones, Argentina. ecrechi@montecarlo.inta.gov.ar 3 Ingeniero Forestal, Msc.,Instituto Nacional de Tecnologia Agropecuaria (INTA), Av. El Libertador 2472, 3384, Montecarlo, Misiones, Argentina. mpinazo@montecarlo.inta.gov.ar 4 Ingeniero Forestal, Instituto Nacional de Tecnologia Agropecuaria (INTA), Av. El Libertador 2472, 3384, Montecarlo, Misiones, Argentina. avonwallis@montecarlo.inta.gov.ar 5 Ingeniero Forestal, Universidad Nacional de La Plata, Facultad de Ciencias Agrarias y Forestales, CC 31 (1900), La Plata, Provincia de Buenos Aires, Argentina. jmarqui@agro.unlp.edu.ar 6 Licenciada en Biologia, Dra., Facultad de Ciencias Agrarias y Forestales, Universidad Nacional de La Plata, CC 31 (1900), La Plata, Provincia de Buenos Aires, Argentina. Consejo Nacional de Investigaciones Cientificas y tecnicas (CONICET). smonteoliva@yahoo.com.ar Recebido para publicacaoem 31/01/2012 e aceito em17/04/2013

Fire-free natural regeneration in water limited Pinus halepensis forests: a silvicultural approach

We aimed to elucidate environmental and silvicultural factors that determine the extent of fire-free natural regeneration in east Mediterranean Pinus halepensis forests. The specific aims were to study the potential and identify bottlenecks for natural regeneration and examine the effects of overstory thinning and site preparation treatments. We integrated four experiments conducted in diverse ecoregions in Israel ranging from semiarid to subhumid. Seedling emergence and survival were traced for 2–4 years in Mishmar Ha’Emek Forest (MHF) with annual rainfall of 604 mm; Shaharia Forest (SF)—435 mm; and Yatir Forest (YF)—280 mm. Effects of thinning treatments: clearcut, 100 tree, 200 tree ha−1 and control—310 tree ha−1, were examined in MHF. Effects of site preparation treatments: soil scarification and herb clipping were examined in SF. Density of emerged seedlings varied among ecoregions and was linked to average annual rainfall. Within ecoregions, emerged seedling density was higher on north-facing slopes than on south-facing slopes and was strongly related to stand characteristics (e.g., stem basal area) and seed rain. Seedling survival rate of about 20 % was recorded in MHF while no seedling survival was observed in YF and SF during the study years. Thinning treatments reduced seed rain and emerging seedling density, but increased seedling survival and growth. Recruitment 4 years after thinning was highest in the 100 tree ha−1 treatment and lowest in the control. In SF, seedling survival was limited mainly by herbaceous vegetation and was improved by soil scarification and herb clipping. Silvicultural implications are discussed.

Longitudinal growth strain as a log and wood quality predictor for plantation-grown Eucalyptus nitens sawlogs

Peripheral longitudinal growth strain (LGS) was measured on a total of 81, 22-year-old pruned Eucalyptus nitens trees from five thinning treatments in a plantation thinning trial in Tasmania. Growth strain data were gathered at breast height on each tree using the CIRAD-Foret method. The effects of thinning treatment and tree diameter on LGS and its relationships to solid-wood traits determined in a processing trial were examined. LGS was significantly higher in the direction of the prevailing wind and was not significantly affected by either thinning treatment or tree diameter. An index of log end splitting was positively related to tree diameter, sawlog position (upper/lower), and LGS, which explained up to an additional 20% of the variance after tree diameter and log position were accounted for in a linear regression model. High LGS and log end splitting were significant indicators of increased board end splitting.

The effects of a thinning treatment on carbon stocks in a northern Arizona ponderosa pine forest

Vast areas of ponderosa pine ( Pinus ponderosa Dougl. ex Laws.) forest in the western United States have become unnaturally dense because of relatively recent land management practices that include fire suppression and livestock grazing. In many areas, thinning treatments can re-establish the natural ecological processes and help restore ecosystem structure and function. Precipitous global climate change has focused attention on the carbon storage in forests. An unintended consequence of fire suppression has been the increased storage of carbon in ponderosa stands. Thinning treatments reduce standing carbon stocks while releasing carbon through the combustion of fuel in logging machinery, burning slash, and the decay of logging slash and wood products. These reductions and releases of stored carbon must be compared to the risk of catastrophic fire burning through the stand and releasing large quantities of carbon to the atmosphere to more fully understand the costs and benefits – in carbon terms – of forest restoration strategies. This study examines the effect of a restoration thinning treatment on the carbon stock of a ponderosa pine forest. The total pre-treatment above-ground carbon stock was 48,880 kg C ha −1 and the post-treatment stand had 36,420 kg C ha −1. The carbon stock in trees across the stand ranged from 28,560 to 67,560 kg C ha −1 pre-treatment and from 11,970 to 55,510 kg C ha −1 post-treatment. 8240 kg C ha −1 was removed from the site and sold to the wholesale firewood market (plot values ranged from 4890 to 12,310 kg C ha −1), 91 kg C ha −1 was released from the combustion of fuel in harvesting operations and trucking, and the processing of the firewood required carbon released 33 kg C ha −1. The burning of slash piled on site released 4140 kg C ha −1 (plot values ranged from 2920 to 6900 kg C ha −1). We estimated that in a stand-replacing fire, the treated stand would release 2410 kg C ha −1 less to the atmosphere than the untreated stand. However, the thinning treatment resulted in stand structural changes that make the stand less likely to support a crown fire and therefore more likely to avoid the carbon releases associated with crown fires, even under extreme fire conditions. On balance, the thinning treatment released 3114 kg C ha −1. If the wood removed from the site had been used in longer-lasting products, the thinning could have resulted in net carbon storage on the order of 3351 kg C ha −1.

Effects of thinning treatment on an ectomycorrhizal succession under Scots pine

We describe a 16 yr dataset of ectomycorrhizal fruit bodies under Scots pine (Pinus sylvestris), starting from seedlings, and explore the effects of a 50% thinning treatment imposed in year 12. The over-riding pattern in the data was of successional development, with Paxillus involutus and Laccaria proxima in the earliest years, followed by Suillus species, while in later years Amanita and Cortinarius species became prominent. The typical pattern was for each species in turn to increase to a maximum count then gradually decline without actually disappearing from the community (an addition succession). For nine out of the 30 species recorded the time profiles were fitted significantly by a long-normal curve, although the best-fit lognormal models consistently under-estimated the peak count. Thinning increased counts of Suillus bovinus, Gomphidius roseus and Cortinarius semisanguineus, but overall its effect on the community was minor. Rainfall in September was weakly correlated with successional advancement (measured as DCA first axis scores). Mean fruiting date increased significantly as the stands aged.