bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growing stock estimation for alpine forests in Austria: a robust lidar-based approach
Authors: Hollaus M. , Wagner W. , Schadauer K. , Maier B. , Gabler K. 
Published: August 2009

The overall goal of this study was to describe a novel area-based semiempirical model for estimating growing stock from small-footprint light detection and ranging (lidar) data. The model assumes a linear relationship between growing stock and lidar-derived canopy volume that is stratified according to several canopy height classes to account for height dependent differences in canopy structure and nonlinear tree size-shape relationships. It was applied over a 128 km2 alpine area in Austria where operational forest inventory data and lidar data acquired in winter and summer were available. The analysis showed that the semiempirical model was quite robust against changes in laser point density and acquisition time. Further, it was found that the model performed as well as a widely used iterative regression method based on a multiplicative model. Both models reached a high coefficient of determination (R2 = 0.76–0.86) and a standard deviation of the residuals in the order of 20.4%–29.1%. Although it is less flexible than the multiplicative model, the advantages of the semiempirical model are its simplicity and the fact that its coefficients can be physically interpreted. These traits can be expected to enhance the applicability of the model in regions where high-quality inventory data are lacking.
Effects of tree species and clear-cut forestry on forest-floor characteristics in adjacent temperate forests in northern Spain
Authors: Gartzia-Bengoetxea Nahia , González-Arias Ander , Martínez de Arano Inazio 
Published: August 2009

The litter layer (L) and fermented humified layer (FH) in forest floor under European beech ( Fagus sylvatica L.), pedunculate oak ( Quercus robur L.), and radiata pine ( Pinus radiata D. Don) were studied in northern Spain. Recovery from heavy mechanization was also assessed in a chronosequence from two adjacent pine plantations (3 and 16 years old). Interspecific differences in forest-floor mass and mass distribution were related to litter quality and decomposition rates. In the L layer, acid-insoluble residue/N, C/N, and C/P ratios were lower, and pH and Ca contents higher in the deciduous stands than in the pine stand. The microbial respiration rate was higher and functional diversity lower in the pine stand than in the deciduous stands, without differences in microbial biomass. Cross-polarization, magic angle spinning 13C nuclear magnetic resonance and proximate analysis revealed similar C functional groups in beech and pine stands. Forest floor was still absent 3 years after heavy mechanization, and after 16 years, it was 50% less abundant than in the mature stand. Microbial respiration rate, biomass, and diversity were similar in the L layer in 16-year-old and mature pine stands, but in the FH layer, microbial-community diversity remained low after 16 years. The results underline the effects of forest management on C transformations in the forest-floor layers. These effects may be evident even after 16 years of heavy mechanization.
Controlling Kalmia and reestablishing conifer dominance enhances soil fertility indicators in central Newfoundland, Canada
Authors: Moroni Martin T. , Thiffault Nelson , Titus Brian D. , Mante Christina , Makeschin Franz 
Published: August 2009

Growth rates of young conifers can be poor on disturbed sites dominated by Kalmia angustifolia L. Hence, a conifer revegetation trial was established on a Kalmia -dominated site to evaluate the effects of various silvicultural options and planted species on selected soil organic layer characteristics. Larix laricina (Du Roi) K. Koch, Pinus banksiana Lamb., and Picea mariana (Mill.) BSP seedlings were planted in plots with or without Kalmia control with herbicides. The effect of fertilizer amendment was also assessed. Seventeen years postplanting, organic layer fertility indicators suggest that soil fertility improved after Kalmia control and conifer reestablishment, especially if nitrogen (N) – phosphorus – potassium fertilizer was also applied. When Kalmia was controlled, aerobically mineralizable N and exchangeable sodium concentrations were increased; fertilizer addition to herbicided plots also increased exchangeable potassium and calcium concentrations, and cation exchange capacity compared with untreated control plots. Conifer height, diameter, and canopy closure were Larix > Pinus > Picea. Kalmia cover in control plots was 87%; Kalmia reinvasion in herbicided plots achieved 40%–43% cover but did not differ among the conifer species. Principal component analysis indicated that aerobically mineralizable N and total N were positively correlated with canopy closure. Our results suggest that increases in organic-layer fertility were related to increased conifer size resulting from Kalmia control.
Relationships between acoustic variables and different measures of stiffness in standing Pinus taeda trees
Authors: Mora Christian R. , Schimleck Laurence R. , Isik Fikret , Mahon Jerry M. , Clark Alexander , Daniels Richard F. 
Published: August 2009

Acoustic tools are increasingly used to estimate standing-tree (dynamic) stiffness; however, such techniques overestimate static stiffness, the standard measurement for determining modulus of elasticity (MOE) of wood. This study aimed to identify correction methods for standing-tree estimates making dynamic and static stiffness comparable. Sixty Pinus taeda L. trees, ranging from 14 to 19 years old, obtained from genetic tests established in the southeastern United States, were analyzed. Standing-tree acoustic velocities were measured using the TreeSonic tool. Acoustic velocities were also recorded in butt logs cut from the same trees using the Director HM200. A strong but biased relationship between tree and log velocities was observed, with tree velocities 32% higher (on average) than the corresponding log velocities. Two correction methods, one for calibrating tree velocities and one for accounting for differences in wood moisture content, were used to determine an adjusted MOE. After correction, adjusted MOE estimates were in good agreement with static longitudinal MOE values measured on clearwood specimens obtained from the trees, and no systematic bias was observed. The results of this study show that acoustic estimates of MOE on standing trees largely depend on how the data are processed and the reference method used.
Death and Taxus: the high cost of palatability for a declining evergreen shrub, Taxus canadensis
Authors: Holmes Stacie A. , Webster Christopher R. , Flaspohler David J. , Froese Robert E. 
Published: August 2009

Taxus canadensis Marsh., a shade-tolerant evergreen shrub, is in decline as a result of past anthropogenic disturbances and increased cervid browsing. To identify factors that may be influencing establishment for this species, we planted 1080 T. canadensis cuttings in a hemlock–hardwood forest in the spring of 2004. Cuttings were planted across a gradient of light environments, consisting of artificial canopy gaps (61–441 m2) and closed-canopy conditions, and half were protected with deer exclosures. Following four growing seasons, T. canadensis survival in exclosures was 92% compared with 75% in controls. A mixed-effects binary logistic regression analysis revealed that deer exclusion had the most influence on the probability of survival; all else being equal an individual was nearly seven times more likely to survive if planted inside an exclosure (P < 0.001). Increasing light intensity had a counterbalancing effect on growth and survival; light increased leader growth (P = 0.019) but reduced an individual’s probability of survival (P < 0.001), possibly owing to enhanced herbivory and elevated moisture stress. Consequently, enhancing resource availability and growth may not decrease the impact of biomass loss to herbivory. These results suggest that even with relatively low herbivore densities, exclosures are required for the recovery of highly palatable species.
Carbon sequestration in a chronosequence of Scots pine stands in a reclaimed opencast oil shale mine
Authors: Karu Helen , Szava-Kovats Robert , Pensa Margus , Kull Olevi 
Published: August 2009

Ecosystems that develop on mine spoil can serve as significant sinks for CO2. The aim of this study was to estimate the rate of carbon accumulation and its distribution along forest ecosystem partitions in young Scots pine ( Pinus sylvestris L.) plantations in the Narva oil shale opencast, Estonia. The tree layer was measured in 2004 in 13 stands afforested with 2-year-old seedlings during 1968 to 1994. Three stands (afforested in 1990, 1983, and 1968) were selected for detailed analysis of the carbon sequestration. Soil profiles were sampled in these stands in 2005. Radiocarbon analysis combined with a simple model of litter production was used to differentiate between plant-derived recent carbon and carbon stemming from fragments of oil shale. Total carbon accumulated since afforestation in vegetation, forest floor, and A horizon was 7.8 t·ha–1in the stand established in 1990, 34.5 t·ha–1in that established in 1983, and 133.4 t·ha–1in that established in 1968. Most of the sequestered carbon was allocated to tree stems; their portion increasing with age from 28% to 51%. The portion of recent soil organic carbon increased from 5% to 23%, which shows that soils contribute significantly to carbon accumulation during early forest succession on degraded land.
Climate and intraannual density fluctuations in Pinus pinaster subsp. mesogeensis in Spanish woodlands
Authors: Bogino Stella , Bravo Felipe 
Published: August 2009

Intraannual features or anomalies in the tree rings of woody species may provided useful information for ecological and climatological studies. The frequency of intraannual density fluctuations (IADFs), differences in IADFs according to the cambial age, changes in IADFs in the last century, and relationships of IADFs to radial growth and climate were analyzed in five stands of Pinus pinaster subsp. mesogeensis (Fieschi & Gaussen) Silba in east-central Spain. Standard dendrochronological techniques were used. Two cores were extracted 1.30 m above ground level from 15 dominant and codominant trees at each sampling site. The data were analyzed by analysis of variance, Pearson’s correlation, and logistic regression. Results showed that (i) the mean frequency of IADFs was higher in younger than older trees; (ii) the frequency of IADFs increased from the 1940s to the present; (iii) radial growth was negatively correlated with the presence of IADFs; and (iv) density fluctuations may be predicted by using a logistic model, with monthly rainfall and temperature as independent variables. Studies of intraannual features or anomalies in radial growth may be useful for ecological and climatological applications under forecasted climate change scenarios.
Ice storm effects on the canopy structure of a northern hardwood forest after 8 years
Authors: Weeks Brian C. , Hamburg Steven P. , Vadeboncoeur Matthew A. 
Published: August 2009

Ice storms can cause severe damage to forest canopies, resulting in differential mortality among tree species and size classes and leading to long-lasting changes in the vertical structure and composition of the forest. An intense ice storm in 1998 damaged large areas of the northern hardwood forest, including much of the Hubbard Brook Experimental Forest, New Hampshire (USA). Following up on detailed poststorm assessments, we measured changes in the vertical structure of the forest canopy 8 years poststorm. We focused on how the presence of disease-induced advance regeneration of American beech ( Fagus grandifolia Ehrh.) has affected canopy structure in the recovering forest. We measured foliage-height profiles using a point-quadrat approach and a pole-mounted leaf area index (LAI) sensor. Although the total LAIs of damaged and undamaged areas were similar, areas damaged in 1998 showed an increased proportion of total leaf area between 6 and 10 m above the ground. The foliage at this height is largely (54%) beech. To the extent that this heavily beech-dominated understory layer suppresses regeneration of other species, these findings suggest that rare disturbances of mature northern hardwood forests affected by beech bark disease will increase the importance of damage-prone and economically marginal beech.
Seed germination and seedling vigor of weevil-damaged acorns of red oak
Authors: Lombardo Jeffrey A. , McCarthy Brian C. 
Published: August 2009

Acorn weevils (Coleoptera: Curculionidae) are well-known predators of oak acorns in the eastern hardwood forest region of the United States. We examined the germination percentage of seeds, as well as the physical characteristics of seedlings, originating from both weevil-damaged and sound acorns of red oak ( Quercus rubra L.) to determine if weevil depredation impacts seedling vigor. Seeds were grown under greenhouse conditions for a period of 8 weeks. X-ray imaging was used as a nondestructive method for determining seed condition prior to germination. The combined data set showed a reduction in germination percentage from 86% for sound acorns to 26% for those damaged by weevils. Seven seedling metrics were evaluated for differences between seedlings originating from sound and those from weevil-damaged acorns. Of these metrics, the number of leaf flushes, total number of leaves, root collar diameter, shoot length, and dry mass were significantly (P < 0.05) different. Two variables, root length and shoot diameter, were not significantly different. Early allocation of resources to root establishment likely explains these findings. Because of reduced stem height and leaf number, seedlings from weevil-damaged acorns are likely to be less competitive in the forest understory than those from sound acorns.
Improving initiation, genotype capture, and family representation in somatic embryogenesis of Pinus radiata by a combination of zygotic embryo maturity, media, and explant preparation
Authors: Hargreaves Cathy L. , Reeves Cathie B. , Find Jens I. , Gough Keiko , Josekutty Puthiyaparambil , Skudder Dolina B. , van der Maas Susan A. , Sigley Margaret R. , Menzies Mike I. , Low Charlie B. , Mullin Tim J. 
Published: August 2009

The principal aim of this investigation was to improve somatic embryogenesis initiation and to enhance representation of families and genotypes within those families of Pinus radiata D. Don. A total of 19 open-pollinated seed families, many with unrelated and weakly related parents, were tested. Optimum stage of cone maturity for initiation success was tested by five collections made at 1 week intervals, spanning the developmental period from pro-embryo to cotyledonary embryos. Two media were compared; embryo-development media (EDM6) and a modified Litvay medium (Glitz). Two zygotic embryo explant-preparation techniques were tested; embryos with retained megagametophytes and excised embryos. Proliferating embryogenic tissues were obtained from all four treatments (2850 explants per treatment, 570 per collection time) for the 19 families. The best initiation rates were achieved with a combination of Glitz medium with excised zygotic embryos, with 55% of explants from all collections and all families combined giving rise to proliferating embryogenic tissue. At the optimal collection time for each of the families, this treatment gave a range of 47%–97% initiation success with an average of 70% per family.
Engineering and Directed Evolution of a Ca2+ Binding Site A‐Deficient AprE Mutant Reveal an Essential Contribution of the Loop Leu75–Leu82 to Enzyme Activity
Authors: Romero-García Eliel R. , Téllez-Valencia Alfredo , Trujillo María F. , Sampedro José G. , Nájera Hugo , Rojo-Domínguez Arturo , García-Soto Jesús , Pedraza-Reyes Mario 
Published: August 2009

An aprE mutant from B. subtilis 168 lacking the connecting loop Leu75–Leu82 which is predicted to encode a Ca2+ binding site was constructed. Expression of the mutant gene (aprE ΔLeu75–Leu82) produced B. subtilis colonies lacking protease activity. Intrinsic fluorescence analysis revealed spectral differences between wild‐type AprE and AprEΔL75–L82. An AprEΔL75–L82 variant with reestablished enzyme activity was selected by directed evolution. The novel mutations Thr66Met/Gly102Asp located in positions which are predicted to be important for catalytic activity were identified in this variant. Although these mutations restored hydrolysis, they had no effect with respect to thermal inactivation of AprEΔL75–L82
T66M
G102D. These results support the proposal that in addition to function as a calcium binding site, the loop that connects β‐sheet e3 with α‐helix c plays a structural role on enzyme activity of AprE from B. subtilis 168.
Interactions between Transient and Long-Term Auditory Memory as Reflected by the Mismatch Negativity
Authors: Winkler István , Cowan Nelson , Csépe Valéria , Czigler István , Näätänen Risto 
Published: August 2009

Abstract
The mismatch negativity (MMN) event-related potential (ERP) component is elicited by any discriminable change in series of repetitive auditory stimuli. MMN is generated by a process registering the deviation of the incoming stimulus from the trace of the previous repetitive stimulus. Using MMN as a probe into auditory sensory memory, the present study addressed the question of whether the sensory memory representation is formed strictly on the basis of an automatic feature analysis of incoming sensory stimuli or information from long-term memory is also incorporated. Trains of 6 tone bursts (standards with up to 1 deviant per train) separated by 9.5-sec intertrain intervals were presented to subjects performing a visual tracking task and disregarding the auditory stimuli. Trains were grouped into stimulus blocks of 20 trains with a 2-min rest period between blocks. In the Constant-Standard Condition, both standard and deviant stimuli remained fixed across the session, encouraging the formation of a long-term memory representation. To eliminate the carryover of sensory storage from one train to the next, the first 3.6 sec of the intertrain interval was filled with 6 tones of random frequencies. In the Roving-Standard Condition, the standard changed from train to train and the intervening tones were omitted. It was found that MMN was elicited by deviants presented in Position 2 of the trains in the Constant-Standard Condition revealing that a single reminder of the constant standard reactivated the standard-stimulus representation. The MMN amplitude increased across trials within each stimulus block in the Constant- but not in the Roving-Standard Condition, demonstrating long-term learning in that condition (i.e., the standard-stimulus trace indexed by the MMN amplitude benefitted from the presentations of the constant standard in the previous trains). The present results suggest that the transient auditory sensory memory representation underlying the MMN is facilitated by a longer-term representation of the corresponding stimulus.
Long-Term Retention Deficits in Two Cases of Disproportionate Retrograde Amnesia
Authors: Kapur Narinder , Scholey Keith , Moore Elizabeth , Barker Simon , Brice Jason , Thompson Simon , Shiel Agnes , Carn Roland , Abbott Patricia , Fleming John 
Published: August 2009

AbstractThe status of very long-term retention, together with detailed brain imaging correlates, is presented in two patients with disproportionately dense retrograde amnesia. The first patient suffered a severe closed head injury and was left with dense autobiographical amnesia for events that she had experienced prior to her injury. She showed relatively mild, patchy memory impairment on standard anterograde memory tests. Postinjury autobiographical memory was relatively spared. However, postinjury long-term knowledge acquisition was significantly impaired. The second patient also suffered a severe head injury and was left with marked retrograde amnesia for events that she had experienced prior to her injury. She also showed relatively mild, patchy impairment on standard anterograde memory tests. Using specially designed tests, this patient showed normal immediate learning and delayed recall using a range of materials, but displayed significantly faster rate of forgetting over a period of 6 weeks than control subjects who were matched on initial delayed levels of retention. In both cases, there was major pathology in the region of the left temporal lobe, with lateral structures being more affected than medial structures. Our findings provide further evidence relating to the independence of certain anterograde and retrograde memory mechanisms, and support recent observations (De Renzi & Lucchelli, 1993) that link some instances of retrograde amnesia to impairment in very long-term retention. The possibility is raised that some forms of retrograde amnesia, such as the present cases, represent a type of “disconnection syndrome,” whereby visual-semantic and other associations are disconnected from verbal representations of such associations. Lesions to intrahemispheric fasciculi or similar association fibers, in combination with lesions to critical anterior or posterior cerebral structures, may play an important role in such a disconnection.
Dissociations in the Processing of “What” and “Where” Information in Working Memory: An Event-Related Potential Analysis
Authors: Mecklinger A. , Müller N. 
Published: August 2009

Abstract
Based on recent research that suggests that the processing of spatial and object information in the primate brain involves functionally and anatomically different systems, we examined whether the encoding and retention of object and spatial information in working memory are associated with different ERP components. In a study-test procedure subjects were asked to either remember simple geometric objects presented in a 4 by 4 spatial matrix irrespective of their position (object memory task) or to remember spatial positions of the objects irrespective of their forms (spatial memory task). The EEG was recorded from 13 electrodes during the study phase and the test phase. Recognition performance (reaction time and accuracy) was not different for the two memory tasks. PCA analyses suggest that the same four ERP components are evoked in the study phase by both tasks, which could be identified as N100, P200, P300, and slow wave. ERPs started to differ as a function of memory task 225 msec after stimulus onset at the posterior recording sites: An occipital maximal P200 component, lateralized to the right posterior temporal recording site, was observed for the object memory but not for the spatial memory task. Between-tasks differences were also obtained for P300 scalp distribution. Moreover, ERPs evoked by objects that were remembered later were more positive than ERPs to objects that were not remembered, starting at 400 msec postsimulus. The PCA analysis suggest that P300 and a slow wave following P300 at the frontal recordings contribute to these differences. A similar differential effect was not found between positions remembered or not remembered later. Post hoc analyses revealed that the absence of such effects in the spatial memory task could be due to less elaborated mnemonic strategies used in the spatial task compared to the object memory task. In the face of two additional behavioral experiments showing that subjects exclusively encode object features in the object memory task and spatial stimulus features in the spatial memory task, the present data provide evidence that encoding and rehearsal of object and spatial information in working memory are subserved by functionally and anatomically different subsystems.