European Mixed Forests: definition and research perspectives

peer-reviewedAim of study: We aim at (i) developing a reference definition of mixed forests in order to harmonize comparative research in mixed forests and (ii) briefly review the research perspectives in mixed forests. Area of study: The definition is developed in Europe but can be tested worldwide. Material and methods: Review of existent definitions of mixed forests based and literature review encompassing dynamics, management and economic valuation of mixed forests. Main results: A mixed forest is defined as a forest unit, excluding linear formations, where at least two tree species coexist at any developmental stage, sharing common resources (light, water, and/or soil nutrients). The presence of each of the component species is normally quantified as a proportion of the number of stems or of basal area, although volume, biomass or canopy cover as well as proportions by occupied stand area may be used for specific objectives. A variety of structures and patterns of mixtures can occur, and the interactions between the component species and their relative proportions may change over time. The research perspectives identified are (i) species interactions and responses to hazards, (ii) the concept of maximum density in mixed forests, (iii) conversion of monocultures to mixed-species forest and (iv) economic valuation of ecosystem services provided by mixed forests. Research highlights: The definition is considered a high-level one which encompasses previous attempts to define mixed forests. Current fields of research indicate that gradient studies, experimental design approaches, and model simulations are key topics providing new research opportunities.The networking in this study has been supported by COST Action FP1206 EuMIXFOR

Ecological studies of the aquatic soil invertebrates in three inundation forests of Central Amazonia

From January 1971 till August 1972 ecological studies were carried out on the aquatic macroinvertebrates of the benthos community of three Central-Amazonian inundation forests. The three investigated forests were chosen according to the influence of different water types. These forests were: 1. a site with an inflow of whitewater on Ilha de Curarí, 2. a site in a mixed water area at Lago Janauarí, and 3. a site in a black water area at Rio Tarumã Mirím. The annual water level fluctuations caused similar ecological conditions concerning seasonal changes, whereas the differences between the forests depended on the inflow of the different water types. The benthos composition differs according to the inundation forest type. Stenecious species, occurring only in one of the three forests, as well as euryecious species, inhabiting the three forests, were found. In addition many species were obtained which live either in white and mixed water or in mixed and black water. The soil invertebrates adapted to the annual water level fluctuations. The most common adaptation may be seasonal dispersal, being developed as a migration or a translocation. Migrations could be detected for Campsurus notatus and Eupera simoni in white respectively mixed water. In black waters numerous species show a translocation, caused by the oxygen deficit of the deep water. A diapause stage can be assumed for Eupera simoni. This dormant stage enables the bivalve to persist in the forest during the dry period. Brasilocaenís irmleri assumingly transports its eggs by the current in optimal habitats, where it develops rapidly in 14-21 days. A dependence on the forest habitat was detected for some species of the mixed and black water. Other species of the inundation area, particularly of the white water area, are not dependent on the forest habitat. In addition to seasonal changes in the benthos composition, a vertical stratification was found. The inundation forest can be subdivided in a river or lake near part, a central part, and a terra firme near part. The intestinal content studies on the soil invertebrates and the oxygen conditions in the three inundation forests indicate the probable different breakdown of the litter in the forest of the várzea on the one hand and the igapó on the other hand. Secondary productions could be estimated for the white water area with 10-15 g/m2 and year and for the mixed water area with 90-110 g/m2 and year. In the inundation forest of the mixed water, having the highest production of the three forests, environmental factors like oxygen concentration, sedimentation etc. and trophic factors offer favourable conditions for the inhabitation of the benthos

Clearwing Moths Captured by Ultraviolet Light Traps in Southern Ohio (Lepidoptera: Sesiidae)

Trapping with ultraviolet light in mixed-oak forests of Lawrence and Vinton Counties, Ohio in 1995 and 1996 yielded 46 Synanthedon acerni and four Synanthedon arkansasensis, a clearwing moth record new for the state

Invasion of winter moth in New England: Effects of defoliation and site quality on tree mortality.

Abstract Widespread and prolonged defoliation by the European winter moth, Operophtera brumata L., has occurred in forests of eastern Massachusetts for more than a decade and populations of winter moth continue to invade new areas of New England. This study characterized the forests of eastern Massachusetts invaded by winter moth and related the duration of winter moth defoliation estimated using dendrochronology to observed levels of tree mortality and understory woody plant density. Quercus basal area mortality in mixed Quercus and mixed Quercus-Pinus strobus forests in eastern Massachusetts ranged from 0-30%; mortality of Quercus in these forests was related to site quality and the number of winter moth defoliation events. In addition, winter moth defoliation events lead to a subsequent increase in understory woody plant density. Our results indicate that winter moth defoliation has been an important disturbance in New England forests that may have lasting impacts

Working paper 28: Southwestern mixed conifer forests: Evaluating reference conditions to guide ecological restoration treatments.

Mixed-conifer forests of the Southwest are variable and complex, covering approximately 2.5-million acres scattered across the region (Dieterich 1983, Korb et al. 2013; Figure 1). Mixed-conifer forests contain a diverse mix of tree species (Table 1) and typically occur between, but do not include, the lower-elevation warmer, drier ponderosa pine forests and the highest-elevation cooler, wetter spruce-fir forests. Because mixed-conifer forests have diverse stand structures, forest composition and disturbance regimes, it is often difficult to generalize about reference conditions and historical fire regimes that can be used to guide management for specific locations. In this working paper, we 1) describe the current knowledge of mixed-conifer historical reference conditions for fire regimes, stand structure, and species composition in the Southwest (Arizona, New Mexico and adjacent areas); 2) provide field diagnostics to assess reference conditions; and 3) offer land managers restoration-related guidance to promote resilient mixed-conifer forests in the Southwest

Fir-dominated forests in Bavaria, Germany

The map of “Regional natural forest composition by main tree species” (WALENTOWSKI et al. 2001) depicts Bavaria as a region largely predominated by the European beech (Fagus sylvatica). Analyses of climatope, hygrotope and trophotope of fir-dominated regional natural units make evident that the reasons for the preponderance of the European silver fir (Abies alba) are edaphic. In terms of regeneration vigour, growth and yield the fir particularly dominates in habitats with a combination of humus cover, acid-oligotrophic topsoils and clayey or waterlogged subsoils, where the beech usually exhibits stunted and malformed growth forms. This ecological preference has the effect that Bavarian Abies alba-forests are restricted to small patches within a matrix of potential natural vegetation formed by mixed deciduous-coniferous mountain forests. Within European Natura 2000 areas Abies- forests should be recorded carefully as special habitats. Their transitional character between temperate beech forests (habitat type 9130) and boreal spruce forests (habitat type 9410), the ecological preference of Abies alba as an endangered tree species and their sensitivity against environmental stressors, including changes in forest structure, air quality, and climate, make them important objects for nature conservation

Information Forests

We describe Information Forests, an approach to classification that generalizes Random Forests by replacing the splitting criterion of non-leaf nodes from a discriminative one -- based on the entropy of the label distribution -- to a generative one -- based on maximizing the information divergence between the class-conditional distributions in the resulting partitions. The basic idea consists of deferring classification until a measure of "classification confidence" is sufficiently high, and instead breaking down the data so as to maximize this measure. In an alternative interpretation, Information Forests attempt to partition the data into subsets that are "as informative as possible" for the purpose of the task, which is to classify the data. Classification confidence, or informative content of the subsets, is quantified by the Information Divergence. Our approach relates to active learning, semi-supervised learning, mixed generative/discriminative learning.Comment: Proceedings of the Information Theory and Applications (ITA) Workshop, 2/7/201

Can we set a global threshold age to define mature forests?

Globally, mature forests appear to be increasing in biomass density (BD). There is disagreement whether these increases are the result of increases in atmospheric CO2 concentrations or a legacy effect of previous land-use. Recently, it was suggested that a threshold of 450 years should be used to define mature forests and that many forests increasing in BD may be younger than this. However, the study making these suggestions failed to account for the interactions between forest age and climate. Here we revisit the issue to identify: (1) how climate and forest age control global forest BD and (2) whether we can set a threshold age for mature forests. Using data from previously published studies we modelled the impacts of forest age and climate on BD using linear mixed effects models. We examined the potential biases in the dataset by comparing how representative it was of global mature forests in terms of its distribution, the climate space it occupied, and the ages of the forests used. BD increased with forest age, mean annual temperature and annual precipitation. Importantly, the effect of forest age increased with increasing temperature, but the effect of precipitation decreased with increasing temperatures. The dataset was biased towards northern hemisphere forests in relatively dry, cold climates. The dataset was also clearly biased towards forests <250 years of age. Our analysis suggests that there is not a single threshold age for forest maturity. Since climate interacts with forest age to determine BD, a threshold age at which they reach equilibrium can only be determined locally. We caution against using BD as the only determinant of forest maturity since this ignores forest biodiversity and tree size structure which may take longer to recover. Future research should address the utility and cost-effectiveness of different methods for determining whether forests should be classified as mature

Non-L\'evy mobility patterns of Mexican Me'Phaa peasants searching for fuelwood

We measured mobility patterns that describe walking trajectories of individual Me'Phaa peasants searching and collecting fuelwood in the forests of "La Monta\~na de Guerrero" in Mexico. These one-day excursions typically follow a mixed pattern of nearly-constant steps when individuals displace from their homes towards potential collecting sites and a mixed pattern of steps of different lengths when actually searching for fallen wood in the forest. Displacements in the searching phase seem not to be compatible with L\'evy flights described by power-laws with optimal scaling exponents. These findings however can be interpreted in the light of deterministic searching on heavily degraded landscapes where the interaction of the individuals with their scarce environment produces alternative searching strategies than the expected L\'evy flights. These results have important implications for future management and restoration of degraded forests and the improvement of the ecological services they may provide to their inhabitants.Comment: 15 pages, 4 figures. First version submitted to Human Ecology. The final publication will be available at http://www.springerlink.co