Recent changes in forest productivity: An analysis of national forest inventory data for common beech (Fagus sylvatica L.) in north-eastern France

Changes in forest growth have been found in European forests and worldwide. However most observations have been derived from samples of restricted size, whose representativeness at a regional forest scale is questionable. National forest inventories provide an interesting perspective for both regional scale assessment of these trends and the investigation of their variations over environmental gradients, but have been little used.     

Abiotic factors related to the incidence of the Austrocedrus chilensis disease syndrome at a landscape scale

In this paper, the incidence of the A. chilensis disease syndrome in the “16 de Octubre” Valley (Chubut, Argentinean Patagonia) was related to landscape climatic, topographic and edaphic attributes, using remote sensing, geographic information systems and statistical methods. A strong relationship between the occurrence and incidence of the A. chilensis disease syndrome and site variables related to poor soil drainage was found. Non-allophanized soils with fine textures on flat and wavy soil phases, geomorphologies associated to alluvial processes, and low elevations and gentle slopes were positively related to the incidence of the disease. These relationships at a landscape scale agree with previous studies carried out at the stand level. A logistic predictive model of diseased occurrence was developed for the study area considering aspect, elevation, slope, mean annual precipitation and soil phase (classified according to predominant slopes).     

The response of the pseudoannual species Trientalis europaea L. to forest gap dynamics in a near-natural spruce forest

The objective of this study was to test relationships between gap size, gap age and performance of the pseudoannual forest herb layer species Trientalis europaea. We also tested for a potential covariation of performance variables with light as the putative driving factor of gap size and gap age effects. The study took place in the core zone of the Harz National Park in a near-natural spruce forest at Mt. Brocken, Germany. We established 70 randomly distributed plots of three different gap age classes (<15 years, >15 and <60 years, >60 years) and undisturbed forest stands. We recorded growth variables of Trientalis (e.g. height of ramets, number of flowers and fruits per ramet and number of daughter tubers per ramet) and measured PPFD (photosynthetic photon flux density). Gap sizes were assessed with GPS, ranged from 131 m² to 16400 m² and were independent from gap age. Population density of T. europaea was neither affected by gap size nor by gap age. However, gap age had an effect on the fitness of Trientalis ramets. In gaps, the species produced a higher number of flowers and fruits. In general, the average proportion of flowering and fruiting was very low, with 13% and 4%, respectively. In contrast, light intensity had a significant positive effect on ramet density, while the number of daughter tubers differed between 0.8 and 0.5 tubers per individual under lowest light and full light intensity, respectively. The general conclusion is that gap size had no effects on the performance of T. europaea, while gap age had both direct effects and indirect effects mediated by light.     

Conversion of native forest to exotic Pinus radiata plantation: Response of understorey plant composition using a plant functional trait approach

This study aimed to determine the response of native plant species to changed growing conditions, especially increased shade, following establishment of exotic Pinus radiata plantation on cleared native eucalypt forest. In the Northern Hemisphere, species tolerant to shading are typically herbaceous perennials, with large seeds, no obvious mechanism of seed dispersal, and spread by clonal means. We investigated whether life form, mode of seed dispersal, leaf area, specific leaf area (SLA), nutrient uptake strategy, seed mass, fire response, plant height, and clonal spread differed between understorey species of pine plantation and native forest. Further, we asked whether plant functional traits that confer tolerance to stress through shading differ from those in other floras. The study was conducted on the Delatite Peninsula in north-eastern Victoria, Australia. Vegetation of adjacent native forest and pine plantation were surveyed using eight 7 m × 7 m plots per site, randomly located within five paired sites. Differences in plant traits between land-use types were tested by Non-metric Multi-dimensional Scaling (NMDS), analysis of similarity (ANOSIM) and paired t-tests. Cluster analysis of the nine plant traits was used to define emergent groups, with differences between land-use types examined by ANOSIM and indicator species analysis. There was a significant change in the composition of understorey vegetation following conversion to pine plantation that included a decline in the richness of native species. NMDS of plant attributes showed a clear separation of native forest from pine plantation with land use strongly correlated in ordination space (r² = 0.611). Cluster analysis produced seven emergent groups of plant functional traits for 78 identified plant species. Phanerophytes split into two groups (myrmecochorous trees and shrubs; myrmecochorous shrubs), perennial herbs into four groups (upright herbs, myrmecochorous herbs, barochorous herbs, flat rosette herbs) with one group representing therophytes and anemochorous perennials. Perennial herbs with intermediate SLA and clonal spread were tolerant of the shaded conditions in pine plantation while the two groups of phanerophytes and the myrmecochorous herbs were largely excluded. Shared traits of excluded emergent groups included those that provided an over-riding adaptation to mineral nutrient stress, including myrmecochory, low SLA, ectomycorrhizal and ericoid mycorrhizal associations and N₂-fixation. These plant traits could not provide tolerance to stress through shading, which is better explained by the open canopied nature of the native forest.     

Comparison of Forest Inventory and Analysis surveys, basal area models, and fitting methods for the aspen forest type in Minnesota

The Forest Inventory and Analysis (FIA) unit of the U.S. Forest Service has collected, compiled, and made available plot data from three measurement periods (identified as 1977, 1990, and 2003, respectively) within Minnesota. Yet little if any research has compared the relative utility of these datasets for developing empirical yield models. This paper compares these and other subdatasets in the context of fitting a basal area (B) yield model to plot data from the aspen (Populus tremuloides Michx.) forest type. In addition, several models and fitting methods are compared for their applicability and stability over time. Results suggest that the three parent datasets, along with their subdatasets, provide very similar three parameter B yield model prediction capability, but as model complexity increases, variability in coefficient estimates increases between datasets. The absence of data for older aspen stands and the inherent noise within B data prevented the exact determination of an overall best model. However, the model B = b₁S^b₂(1 − exp( − b₃A)) with site index (S) and stand age (A) as predictors was found consistently among the highest in precision and stability. Additionally, nonlinear least squares and nonlinear mixed-effects fitting procedures produced similar model fits, but the latter is preferred for its potential to improve model projections. The results indicate little practical difference between datasets from different time periods and different sizes when used for fitting the models. Additionally, these results will likely extend to other states or regions with similar remeasurement data on aspen and other forest types, thus facilitating the development of other ecological models focused on forest management.     

南雄青嶂山常绿阔叶林优势物种组成与结构分析

基于1 hm2的固定样地数据,对粤北南雄小流坑—青嶂山保护区亚热带常绿阔叶林的物种多样性及优势植物种群的年龄、高度结构等特征进行了分析,以探讨森林群落的稳定性与演替进程.结果表明,样地中出现胸径≥1.0 cm的植物38科58属74种,个体总数1621株,建群种为木荷(Schima su-perba)和红锥(Castanopsis hystrix),重要值分别为16.56和12.00;优势种为赤皮青冈(Cyclobalanopsis gilva)、黄樟(Cinnamomum porrectum)、华润楠(Machilus chinensis)、青冈(Cyclobalanopsis glauca);群落优势科为山茶科、壳斗科、樟科、茜草科;群落整体上处于稳定阶段,其中木荷和青冈为稳定至早衰种群,红锥和赤皮青冈为基本稳定种群,华润楠为稳定种群,黄樟为衰老种群;各植物种群高度结构各具特色,其中木荷、华润楠和青冈对整个群落的高度结构影响较大.     

Modeling the effects of alternative management strategies on forest carbon in the Nothofagus forests of Tierra del Fuego,Chile

The impact of forest management activities on the ability of forest ecosystems to sequester and store atmospheric carbon is of increasing scientific and social concern. The nature of these impacts varies among forest ecosystems, and spatially and temporally explicit ecosystem models are useful for quantifying the impacts of a number of alternative management regimes for the same forest landscape. The LANDIS-II forest dynamics simulation model is used to quantify changes to the live overstory and coarse woody debris pools under several forest management scenarios in a high-latitude South American forest landscape dominated by two species of southern beech, Nothofagus betuloides and N. pumilio. Both harvest type (clearcutting vs. partial overstory retention) and rotation length (100 years vs. 200 years) were significant predictors of carbon storage in the simulation models. The prompt regeneration of harvest units greatly enhanced carbon storage in clearcutting scenarios. The woody debris pool was particularly sensitive to both harvest type and rotation length, with large decreases noted under short rotation clearcutting. The roles of extended rotations and partial overstory retention are noted for enhancing net carbon storage on the forest landscape.     

Multiscale spatial variation of the bark beetle Ips sexdentatus damage in a pine plantation forest (Landes de Gascogne,Southwestern France)

Bark beetles are notorious pests of natural and planted forests causing extensive damage. These insects depend on dead or weakened trees but can switch to healthy trees during an outbreak as mass-attacks allow the beetle to overwhelm tree defences. Climatic events like windstorms are known to favour bark beetle outbreaks because they create a large number of breeding sites, i.e., weakened trees and for this reason, windthrown timber is generally preventively harvested and removed. In December 1999, the southwest of France was struck by a devastating windstorm that felled more that 27 million m³of timber. This event offered the opportunity to study large-scale spatial pattern of trees attacked by the bark beetle Ips sexdentatus and its relationship with the spatial location of pine logs that were temporally stored in piles along stand edges during the post-storm process of fallen tree removal. The study was undertaken in a pure maritime pine forest of 1300 ha in 2001 and 2002. We developed a landscape approach based on a GIS and a complete inventory of attacked trees. During this study more than 70% of the investigated stands had at least one tree attacked by I. sexdentatus  . Spatial aggregation prevailed in stands with n≥15$n\ge 15$ attacked trees. Patches of attacked trees were identified using a kernel estimation procedure coupled with randomization tests. Attacked trees formed patches of 500–700 m² on average which displayed a clumped spatial distribution. Log piles stemming from the sanitation removals were mainly distributed along the large access roads and showed an aggregated spatial pattern as well. The spatial relationship between patches of attacked trees and log pile storage areas was analyzed by means of the Ripley’s statistic that revealed a strong association at the scale of the studied forest. Our results indicated that bark beetle attacks were facilitated in the vicinity of areas where pine logs were stored. The spatial extent of this relationship was >1000 m. Similar results were obtained in 2001 and 2002 despite differences in the number and spatial distribution of attacked trees. The presence of a strong “facilitation effect” suggests that log piles should be removed quickly in order to prevent outbreaks of bark beetles.     

Effects of forest structure and microhabitat on the distribution and flowering of a rare understory plant, Actaea elata

Knowing which environmental characteristics constrain forest understory species’ distribution and reproduction can inform conservation decisions about habitat management and locations for reintroduction efforts. Differential plant performance is common in varying environmental conditions, such as levels of canopy closure. Actaea elata (tall bugbane) is a rare, perennial, forest understory herb found from Oregon to British Columbia. Populations throughout this species’ range commonly occur in managed forests. We assessed the importance of environmental variation on the distribution and flowering of A. elata at both microhabitat and site-level scales. At four sites encompassing a variety of forest types, we measured several biotic and abiotic variables at vegetative and reproductive plants, as well as at random points. We measured these same variables at three sites where A. elata has been extirpated. Within occupied sites, reproductive plants were more likely to be located in canopy gaps than were vegetative plants. Both vegetative and reproductive plants were more likely to be found in areas of high herb cover compared to random points. These results indicate that gaps in the canopy may be critical for this species’ ability to reproduce, but survival may be possible in a broader range of forest understory conditions (similar to other co-occurring herb species). Random points at extirpated and occupied sites both tended to be located in areas of lower canopy openness and moisture availability than points in occupied sites where A. elata was present. Extirpated sites were either densely forested or clearcut, while occupied sites contained stands of intermediate density. Circaea alpina, Geranium robertianum, and Lactuca muralis were indicator species for A. elata and normally indicate moist soils, with Circaea alpina being a strong indicator of the presence of flowering A. elata. Taken together, our results suggest that maintenance of canopy gaps is important to promote flowering, and understory species that indicate moist sites, particularly Circaea alpina, can be used as aids to locate new populations of A. elata.     

Effects of a bio-assay guided fraction from Polygonum cuspidatum root on the viability,acid production and glucosyltranferase of mutans streptococci

Polygonum cuspidatum root has been traditionally used for the treatment of dental diseases in Korea. The purpose of this study was to evaluate effects of P. cuspidatum root on the development of dental caries, especially its effects against bacterial viability and caries-inducing factors of Strptococcus mutans and Strptococcus sobrinus. Among methanol extract of P. cuspidatum root and its fraction tested, ethyl acetate fraction, composed of polydatin, resveratrol, anthraglycoside B, and emodin, showed inhibitory effects on glycolytic acid production and glucosyltransferase activity of S. mutans and S. sobrinus in addition to antibacterial activities.