Comparison of tree size structure and growth for partially harvested and even-aged hemlock-spruce stands in southeast Alaska

The effects of partial cutting on tree size structure and stand growth were evaluated in 52 plots in 13 stands in southeast Alaska that were partially harvested 53–96 years ago and compared with 50-year-old even-aged stands that developed after clearcutting. The net basal-area growth was greater in the partially cut plots than in the uncut plots, and basal-area growth generally increased with increasing cutting intensity. However, the basal-area growth of all of the partially harvested stands was significantly less than the growth of 50-year-old even-aged stands, and net basal area growth over the 50 year period since partial harvesting was about 33–43% of the growth of the even-aged stands. Partial cutting maintained stand structures similar to uncut old-growth stands, and the cutting had no significant effect on tree species composition. The tree size distribution of the partially harvested stands was far more complex and well distributed in comparison with the 50-year-old even-aged stands, and included the presence of several trees with diameters of more than 100 cm. These trees included both large-diameter spruce and hemlock trees and were a distinctive structural feature that was noticeably lacking in the even-aged stands.     

Ingrowth model for pyrenean oak stands in north-western Spain using continuous forest inventory data

In this paper, a two stage ingrowth model is presented for predicting periodic, 10 years ingrowth for pyrenean oak (Quercus pyrenaica Willd.) grown in medium to fully stocked coppice stands in north-western Spain. Data from the Spanish National Forest Inventory was used to develop the model, extracting the information from two inventories taken in 222 permanent plots. The first stage of the model predicts the probability of ingrowth occurrence, and in the second stage, the number of recruits is predicted using a conditional model. Both models were biologically realistic and presented logical behaviour. The ingrowth occurrence probability model was dependent on quadratic mean diameter and average height. The recruitment quantification model included stand density and average diameter as explanatory variables. Although the occurrence probability of ingrowth was predicted correctly in 71.7% of cases, the predictions of the number of recruitment are poorer, yielding a coefficient of determination of 0.358. The evaluation criteria included qualitative and quantitative examinations and a testing with independent data from another region. The proposed ingrowth model is the first to be developed for mediterranean oak species in Spain and is an essential feature in any stand growth system.     

Sediment deposition in streams adjacent to upland clearcuts and partially harvested riparian buffers in boreal forest catchments

The rates of fine sediment deposition were compared among three logged and three reference stream reaches 2–3 years before and 3–4 years after logging to assess the environmental impacts of partial harvesting as a novel riparian management strategy for boreal forest streams. The partial-harvest logging resulted in 10, 21 and 28% average basal area removal from riparian buffers at the three logged sites, adjacent to upland clearcut areas. No significant differences from pre-logging or reference-site sedimentation patterns were detected for two of the three logged sites. At the site with the most intense riparian logging (WR2), significant increases of 3–5 times higher than pre-logging or reference levels were detected in fine inorganic sediment (250–1000 μm) load and accumulation in the first year after logging, but no significant change was detected in fine organic sediments or very fine sediments (0.5–250 μm). The increased inorganic sediment deposition at WR2 was temporary with no significant differences from reference or pre-logging levels detectable by summer of the second post-logging year. Logging impacts on fine sedimentation in streams appeared to have been mitigated by careful logging practices including winter harvesting in riparian areas to reduce ground disturbance, and a tendency to avoid immediate (within 3–5 m) stream-side areas. Where it is feasible and advisable to conduct partial harvesting in riparian buffers of boreal forest streams, the logging can be conducted without posing significant risk of increased sediment inputs to streams when careful logging practices are followed.     

Stemflow determination in forest stands

A stemflow measurement technique is described, based on: (1) correlations between stemflow volume and tree diameters at breast height (DBH), determined on the basis of a relatively low number of tree samplings; (2) the distribution of trees in the stand relative to their DBH. Stemflow for trees in a stand (mm) can thus be determined from total rainfall (mm). The results were compared to those obtained with two other stemflow determination techniques. The proposed method was found to be more reliable, precise and easier to apply than the standard methods.     

新造未成林兔害几种防治方法的效果初探

选择兔害危害较重的造林地块,依草兔的生活习性,采取不同的几种环保型防治技术方法,对实施的方法进行效果调查对比和评估,找出操作简便、适用、防治效果好的兔害防治技术方法,以此指导新造未成林兔害防治技术的应用。     

Simplified inference about dominance in forest stands

In a series of papers, Binkley and coauthors suggested dominance curves as a framework for understanding growth dominance and resource use efficiency in forest stands. Constructing a dominance curve requires three major supporting components: an appropriate allometric equation for biomass, sufficient data to characterize the size distribution of trees in the stand, and data on growth from a sufficient number of trees to characterize the relationship between tree size and growth across the entire size distribution. These components are not always available. Here, I propose a simplified approach to inference that can be used to diagnoze positive, neutral, and reverse dominance when the conditions for constructing a full dominance curve cannot be met. I illustrate the approach with published data from an old-growth kauri (Agathis australis) stand, which shows clear evidence of reverse dominance.     

Spruce forest stands in a stationary state

We present stationarity criteria for forest stands,and establish embodiments using a Norwegian empirical stand development model.The natural stationary states only slightly differ from the outcome of long-term simulations previously implemented using the same empirical model.Human interference in terms of diameter-limit cutting is introduced.Consequently,stationary states differing from the natural one appear.Standing volume,growth and monetary value appear low but the financial return rate may be significant.Volume yield and financial return clearly contradict each other,the former arising from harvesting large trees,the latter from frequent removal of small trees.An exponential tree size distribution does not appear to comply with the stationarity criterion.     

Thinning inventory technique and its application in forest resource inventory

IntroductionForestpIanningrequiresinformationabouttheCurrentstateoftheforestresource.Themostcom-monstock-takingactivitiesarestandbasedinvento-riesscubascompartmentsamplingandsystematicsampIingschemesforforeststratainvoIvingpIots.ThesecIassicaIstock-takingactivitiesarescheduIedtotakepIaceatperiodictimeintervaIs.WiththeabandonmentofcIearfelIing,standstructureandcomplexitiesinthevariablesusedtodescribeforeststatushaveaccordinglyincurredchanges,sonewfactorsandtechniquesmustbeintroducedandadde…     

Modeling diameter distributions of mixed-species forest stands

This study compares three diameter distribution models to fit mixed-species forest stands using four example plots with two or three species components in Daxing'an Mountain, PR China. The methods include (1) a finite mixture model (FMM) to fit two or three species components simultaneously, (2) a single Weibull function to fit the whole plot only, and (3) a single Weibull function to fit each species component separately and the summation of the individual species produced the whole plot. Our results indicated that Method 2 is only suitable to regular and unimodal diameter distributions with a balanced reversed J-shape. Method 3 may be able to fit each species component well if its frequency distribution is known and available in the data. However, Method 3 ignores the interspecies relationships within a given plot. Thus, the summation of the species components may not produce a good fit for the whole plot. In contrast, Method 1 (FMM) fits the species component distributions simultaneously with the constraint that the individual components add up to the whole plot, without requiring the observed frequencies for each species across the diameter classes. The FMM models are more flexible to describe highly skewed and irregular diameter distributions for the whole plot, as well as provide the acceptable estimation for each species component and the mixing proportions. Thus, the FMM models can be a useful tool for effectively managing mixed-species forest stands.     

Estimating biomass in northern lower Michigan forest stands

Forest biomass data are now being sought by many forest managers and specialists. These data have been accumulating rapidly in recent years, but numerous gaps remain for various forest types, locations, and site quality levels. This paper illustrates how available information was carefully synthesized to generate biomass data for the evaluation and management of forest stands in northern lower Michigan. The basic approach involved the integration of published specific gravity and biomass distribution data with bolewood volumes predicted from regression equations relating these volumes to stand height and basal area. Preliminary evaluations of the data thus generated indicate that the approach should produce reasonable estimates of stand biomass in this region.     

Estimating leaf area index in different types of mature forest stands in Switzerland: a comparison of methods

Leaf area index (LAI) was estimated at 15 sites in the Swiss Long-Term Forest Ecosystem Research Programme (LWF) in 2004–2005 using two indirect techniques: the LAI-2000 plant canopy analyzer (Licor Inc.) and digital hemispherical photography, applying several exposure settings. Hemispherical photographs of the canopy were analysed using Hemisfer, a software package that offers several new features, which were tested here: (1) automatic thresholding taking the gamma value of the picture into account; (2) implementation of several equations to solve the gap-fraction inversion model from which LAI estimates are derived; (3) correction for ground slope effects, and (4) correction for clumped canopies. In seven broadleaved stands in our sample set, LAI was also estimated semi-directly from litterfall. The various equations used to solve the gap-fraction inversion model generated significantly different estimates for the LAI-2000 measurements. In contrast, the same equations applied in Hemisfer did not produce significantly different estimates. The best relationship between the LAI-2000 and the Hemisfer estimates was obtained when the hemispherical photographs were overexposed by one to two stops compared with the exposure setting derived from the reading of a spotmeter in a canopy gap. There was no clear general relationship between the litterfall and the LAI-2000 or the hemispherical photographs estimates. This was probably due to the heterogeneity of the canopy, or to biased litterfall collection at sites on steep slopes or sites subject to strong winds. This study introduces new arguments into the comparison of the advantages and drawbacks of the LAI-2000 and hemispherical photography in terms of applicability and accuracy.     

Area-level analysis of forest inventory variables

Small-area estimation is a subject area of growing importance in forest inventories. Modelling the link between a study variable Y and auxiliary variables X—in pursuit of an improved accuracy in estimators—is typically done at the level of a sampling unit. However, for various reasons, it may only be possible to formulate a linking model at the level of an area of interest (AOI). Area-level models and their potential have rarely been explored in forestry. This study demonstrates, with data (Y = stem volume per ha) from four actual inventories aided by aerial laser scanner data (3 cases) or photogrammetric point clouds (1 case), application of three distinct models representing the currency of area-level modelling. The studied AOIs varied in size from forest management units to forest districts, and municipalities. The variance explained by X declined sharply with the average size of an AOI. In comparison with a direct estimate mean of Y in an AOI, all three models achieved practically important reduction in the relative root-mean-squared error of an AOI mean. In terms of the reduction in mean-squared errors, a model with a spatial location effect was overall most attractive. We recommend the pursuit of a spatial model component in area-level modelling as promising within the context of a forest inventory.     

国家网络森林医院中建立林木健康卡构想

为了适应林改形势,强化公共服务,完善服务功能,建议在国家网络森林医院中,针对具有林权证的用户建立林木健康卡,记录林地的基本信息、林木防治活动以及用户在网院的咨询与专家的解答等信息,实现网院"服务社会、服务林改、服务现代林业"的宗旨。本文系统地探讨了建立林木健康卡的可行性、设计原则、实现方法与使用方法。     

Development and activity of early saproxylic fungal communities in harvested and unmanaged boreal mixedwood stands

Limited scientific information is currently available regarding saproxylic fungal communities in the boreal forest of North America. We aimed to characterize the community development, richness and activity of saproxylic fungi on fresh wood in harvested and unmanaged boreal mixedwood stands of northwestern Québec (Canada). Fresh wood blocks (n = 480) of balsam fir (Abies balsamea (L.) Mill.) and trembling aspen (Populus tremuloides Michx.) were placed on the forest floor in a range of stand conditions (n = 24). Blocks were harvested every 6 months for up to 30 months and characterized for species composition and richness (PCR–DGGE, DNA sequencing), respiration, wood density and lignin and cellulose content. Colonization by a wide range of functional groups proceeded rapidly under different stand conditions. We detected a total of 35 different fungal operational taxonomic units, with the highest species richness at the wood block level being observed within the first 12 months. No differences in community composition were found between wood host species or among stand conditions. However, the variability in fungal communities among blocks (β diversity) was lower on trembling aspen wood compared with balsam fir and decreased over time on trembling aspen wood. Also, fungal activity (respiration and wood decomposition) increased on trembling aspen wood blocks and species richness decreased on balsam fir wood over time in partial-cut sites. The overlap in tree composition among stands, the high volume of logs and the recent management history of these stands may have contributed to the similarity of the saproxylic fungal community among stand types and disturbances.     

EPSFM系统在森林资源调查中的应用

本文在简要介绍EPSFM(森林资源地理信息系统)的基础上，结合森林资源调查的第一信息基本特点，阐述了FPSFM系统在森林资源调查中应用的基本技术和方法，并给出了详尽的实例说明。     

First report of Phytophthora cinnamomi in forest stands in Germany

Phytophthora cinnamomi was repeatedly isolated from the rhizosphere of recently dead sweet chestnut trees in the upper Rhine valley. Identification was genetically confirmed by RFLP and sequencing of the ITS‐region. This is the first record of P. cinnamomi on forest land in Germany. Mode of introduction of this invasive species and potential factors favouring establishment are discussed.     

天保工程中的低效益林经营

实施天然林保护工程绝不能单纯地理解为是对现有天然林进行封山育林。黑龙江省现存的天然林绝大多数为原始林经过采伐后形成的各类型天然次生林 ,这些次生林 ,由于受不同采伐次数和采伐强度的影响 ,在林分组成、林分结构上都存在着巨大的差异 ,且已不能正常发挥其效能 ,被称之为低效益林。对这部分森林必须施以人为的经营活动 ,才能使其在有效的时间内 ,恢复成高质量的林分或与原生林相类似的林分。1　低效益林形成的原因低效益林主要由林分组成、林分密度、林木分布等林分特征来决定。决定林分特征的主要因素有自然因素和人为因素。自然因…