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Abstract: The monitoring of tree diversity and forest structure is a key pre-requisite for understanding and managing forest ecosystems. This paper addresses the question whether and how tree diversity measures can be estimated as extensions of existing forest resource inventories. The sampling simulator Crancod was employed to compare the precision of angle count and fixed radius plot sampling with respect to nine representative diversity indices. The sampling methods were compared (a) in their overall precision in terms of estimating diversity indices and (b) in their ability to provide precise estimations for three different forest types independent of the spatial inventory scale, e.g. inventories at stand or enterprises level or national forest inventories. The results indicated that most of the spatially explicit indices are more precisely estimated by fixed radius plots. Interestingly the superiority of fixed radius plot sampling to angle count sampling increases significantly with increasing diameter differentiation of forests. However, basal area, basal area related diversity indices and Pielou’s segregation index can be estimated by angle count sampling with at least the same precision as from fixed radius plots. This provides options for situations where discarding angle count sampling is not possible because permanent sampling designs are in place or the importance of forestry summary statistics exceeds that of tree diversity by far. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we present estimated ranges in carbon (C) sequestration per kg nitrogen (N) addition in above-ground biomass and in soil organic matter for forests and heathlands, based on: (i) empirical relations between spatial patterns of carbon uptake and influencing environmental factors including nitrogen deposition (forests only), (ii) 15N field experiments, (iii) long-term low-dose N fertilizer experiments and (iv) results from ecosystem models. The results of the various studies are in close agreement and show that above-ground accumulation of carbon in forests is generally within the range 15–40kgC/kgN. For heathlands, a range of 5–15kgC/kgN has been observed based on low-dose N fertilizer experiments. The uncertainty in C sequestration per kgN addition in soils is larger than for above-ground biomass and varies on average between 5 and 35kgC/kgN for both forests and heathlands. All together these data indicate a total carbon sequestration range of 5–75kgC/kgN deposition for forest and heathlands, with a most common range of 20–40kgC/kgN. Results cannot be extrapolated to systems with very high N inputs, nor to other ecosystems, such as peatlands, where the impact of N is much more variable, and may range from C sequestration to C losses. [Copyright &y& Elsevier]

Abstract: The effects of forest fertilization and Sirococcus shoot blight on growth of mature Norway spruce (Picea abies (L.) Karst.) were studied in a field experiment. The single tree fertilization experiment was established with 144 sample trees in the year 2000. These trees were selected among the dominant and co-dominant trees of the stand in a way that half of the trees exhibited symptoms of Sirococcus shoot blight and the other half did not. One-third of the sample trees were fertilized with dolomitic lime, one-third with kieserite and gypsum and one-third were left unfertilized as control. The treatments were randomly assigned to the sample trees. As the experimental design became unbalanced due to tree mortality caused by bark beetle infestation final analyses were performed with the volume growth data of 125 sample trees only. An analysis of covariance was used to evaluate the effect of fertilization and Sirococcus shoot blight on volume growth. The average volume increment of the period 1977–1980 was used as a covariate attribute, assuming that during this period growth was not yet affected by Sirococcus shoot blight. Indeed an effect of Sirococcus shoot blight on growth turned out to start after 1980 and the analysis revealed that over the whole period 1981–2006 trees with shoot blight symptoms had a significantly lower increment. The increment reduction of the nonfertilized trees by Sirococcus was % in 1981 and was continuously increasing with time to % by the year 2000. A significant positive effect of fertilization was only found for the variant from 2002 to 2006, with the highest surplus increment in 2004 with %, calculated as average over the diseased and healthy group. However, a mitigation of the Sirococcus-caused increment loss via fertilization with kieserite and gypsum was statistically significant only for the year 2003. A moderate relationship between basal area increment and disease severity was found, indicating decreasing basal area increment with increasing disease severity. [Copyright &y& Elsevier]

Sampling procedures within stands for species and diversity indices have been widely discussed. However, little attention has been paid to the assessment of such indices within the framework of forest inventories on the management district level. This study deals with such an inventory comprising 245 angle counts in a 750-ha forest management district at the northern fringe of the Austrian Alps. To calculate spatially explicit indices, the nearest neighbours of the angle count in-trees have to be assessed, The distributions of the indices, their correlations and their ability to discriminate between different stand classes are discussed. It is concluded that these indices are meaningful, because they describe the species composition and the structure of the forest district in the expected way and differ significantly and meaningfully among stand classes which have been classified for silvicultural purposes. [ABSTRACT FROM AUTHOR]

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Individual tree mortality models were developed for the six major forest species of Austria: Norway spruce (Picea abies), white fir (Abies alba), European larch (Larix decidua), Scots pine (Pinus sylvestris), European beech (Fagus silvatica), and oak (Quercus spp.); a joint model for the remaining broadleaf species was also developed. Data came from 5-year re-measurements of the permanent plot network of the Austrian National Forest Inventory. Parameters of the logistic equation were estimated using maximum likelihood methods. For all species, we found the hyperbolic transformation of diameter (D-1) tobe highly significant in predicting the high mortality rates for small diameter trees and decreasing mortality rates for larger diameters. For spruce. a quadratic transformation in D was needed to accurately model the increase in mortality observed for large, low-vigor treeswith diameter >70 cm, which resulted in a U-shaped distribution. Crown ratio was also consistently significant, except for oak. We likewise found basal-area-in-larger-trees (BAL) to be a highly significant predictor of mortality rate for all species except fir and oak. Predicted mortality rate increases as the basal area in larger trees increases and as crown ratio decreases. The resulting logistic mortality model had the same general form for all species, with the signs of allparameters conforming to expectations. In general, chi-square statistics indicate that the most important variable is D-1, thesecond most important is crown ratio, and the third most important predictor is BAL. The relative importance of crown ratio appears to begreater for shade tolerant species (fir, beech, spruce) than for shade intolerant species (larch, Scots pine, oak). Examination of graphsof observed vs. predicted mortality rates reveals that the species-specific mortality models are all well behaved, and match the observedmortality rates quite well. The D-1 transformation is flexible, [ABSTRACT FROM AUTHOR]

In the absence of reliable and representative data on the frequency of seed years, seed amounts, germination and survival of seeds, the data of the observation period 1992--1996 of the permanent national forest inventory of Austria are used to develop a model describing the probability for the occurrence, density and height of Norway spruce (Picea abies (L.) Karst) natural regeneration in the forests of Austria. The forest inventory provided data on natural regeneration (saplings between 10 and 130 cm height) on clusters within a 3.89 km square sampling grid. A logistic equation is used to predict the probabilityfor natural regeneration occurrence. Input parameters for this equation are the variables that describe the site, with slope and azimuth as continuous variables, and growth districts and vegetation types asdiscrete variables; the crown competition factor describes density and the quadratic mean diameter describes the stage of development of the stand. The same equation type is used to predict the probability for the occurrence of Norway spruce, conditional on the occurrence ofsome regeneration. An additional variable in this species specific model is a dummy variable which is set to 1 if Norway spruce occurs inthe overstory and otherwise zero. Additional site variables enteringthis model are elevation and vegetation types characterizing soil fertility and moisture. Because the density and height of spruce regeneration depends on the stand's susceptibility to browsing, the probability for browsing is also modelled as a logistic equation depending on elevation, vegetation type, and stand density. Finally the probability distribution for height and density of the regeneration is described by two bivariate Weibull-distributions. each one describing browsed and unbrowsed Norway spruce regeneration respectively. [ABSTRACT FROM AUTHOR]

In Europe yield tables are frequently used to get information on future total crops as well as on current and future increments per hectare and thus the database for forest valuations, decisions on allowable cut and other management decisions. These yield tables usually claim to describe potential growth and yield per hectare of even-aged pure species stands. As a prerequisite to the use of these yield tables in mixed species, even-aged stands, the area to which every species has to be related needs to be known. The way to calculate this area isto split up the area of the mixed stand into areas each of which is occupied by a 'fully stocked' pure stand of one species. Stocking is measured in terms of observed basal area versus basal area given by the yield tables. Thus the species proportion by area is calculated from the ratios between the observed and the respective yield table basal areas. In order to obtain the necessary sample size for a given precision of the species proportion by area, its variance is calculatedfrom Gauss's law of error propagation with the species proportion bybasal area and the ratio between the respective basal area as they are given by an appropriate yield table as independent variables. Estimates of these variables indicate that 3 to 12 angle counts per stand(basal area factor BAF = 4 m2 ha-1) are sufficient for a standard error of +-10 per cent for the species proportion by area, and 9 to 50 angle counts for one of +-5 per cent. [ABSTRACT FROM AUTHOR]