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Forest biomass has become a viable alternative energy source for replacing fossil fuels, particularly after the European Union acknowledged its sustainability status. To reach zero net greenhouse gas emissions by 2045 in Sweden, new efficient methods of biomass extraction, such as geometrical biomass thinnings, are being explored and tested. These machine-based methods involve the extraction of above-ground biomass in narrow, 1–2 m-wide strips between extraction racks. While evidence-based optimization of biomass extraction mostly focuses on time- and cost-efficiency and on stand growth, criteria such as tree diversity are often overlooked. However, with ongoing climate change, tree diversity is crucial to strengthening the resilience and productivity of future forests, which also enhance the provision of ecosystem services and overall biological diversity. Therefore, we studied the effects of different biomass thinning strategies on spatial tree diversity in southern Sweden using nearest-neighbour summary statistics. We found scientific evidence that different geometrical designs of biomass thinning, especially in 1 or 2 m-wide strips, resulted in higher spatial tree diversity compared to conventional biomass thinning. Hence, in mixed conifer-broadleaved forests, biomass thinning in 1 or 2 m-wide strips is recommended for maintaining spatial tree diversity. [ABSTRACT FROM AUTHOR]

The epidemiology and severity of ash dieback (ADB), the disease caused by the ascomycete fungus Hymenoscyphus fraxineus, has been linked to a variety of site conditions; however, there has been a lack of analysis at an individual tree scale.Symptoms of ADB were scored on ca. 400 trees of Fraxinus excelsior (ash) in permanent sample plots during two successive years in a UK natural woodland reserve. Using comprehensive plot records maintained since 1945, and detailed spatial records updated since 1977, we assembled an array of potential explanatory variables, including site environment factors, ash tree density, previous and present tree condition and near neighbourhood summary statistics (NNSS), such as species mingling and size dominance. Their impact on the severity of ADB of focal ash trees was tested with generalised linear mixed effects models (GLMM).The severity of ADB was much greater in the lower slope parts of the site with moister soils and least in a managed area subject to tree thinning in the previous 35 years. Severity of ADB had a negative association with focal ash tree prior relative growth rate over a period of a decade immediately before the disease was detected at the site. Greater ADB severity was also significantly associated with smaller diameter at breast height of ash trees. Additionally, ADB was significantly positively associated with a greater proportion of heterospecific trees amongst the six nearest neighbours of the focal tree.Synthesis. The relationship of the severity of ADB disease with site environment, tree condition and neighbourhood is complex but nevertheless important in the progression of the disease. The findings suggest some silvicultural interventions, such as thinning to increase the vigour of retained ash trees, might reduce the impact of ADB. [ABSTRACT FROM AUTHOR]

• Spatial species mingling was extended to better describe species-rich forest ecosystems. • We demonstrated the value of the new species segregation function through cluster analysis. • Evidence of improvement was obtained from applying the innovative spatial reconstruction method. • The new characteristic is robust and effective in monitoring species-rich plant communities. Species rich woodland communities play an important role in ecosystem functioning at local, regional and global scale. With ongoing climate change and an ever-increasing human world population we certainly cannot take high species diversity for granted. In fact species diversity is a precious and threatened commodity that requires monitoring and conservation. China has a wealth of natural woodlands with high species diversity that stretch over several climate zones and even in the temperate zone tree diversity is considerable in this country. For monitoring species diversity it is crucial to rely on meaningful summary characteristics that offer sufficient information to make correct decisions in conservation. We analysed large, fully mapped plots from ten species-rich temperate forest sites with the new species segregation function as a significantly more meaningful extension of the traditional spatial species mingling index. The new characteristic is a function of distance and we defined a number of auxiliary measures describing its shape for a more effective analysis of spatial species diversity. We could show that these auxiliary characteristics helped to classify species-rich forests as part of a cluster analysis, which supports the view that the species segregation function provides high quality information. We also successfully applied non-parametric modelling through spatial reconstruction for testing the contribution of the species segregation function to a synthesis of observed spatial species diversity patterns. The results demonstrated that the new characteristic described the complex diversity patterns well and has the potential of being a robust and effective characteristic in monitoring species-rich woodland communities. [ABSTRACT FROM AUTHOR]

The application of gap dynamics theory appears to be a promising option for tropical forest management and conservation. In the present study of a tree species-rich and old-growth Ecuadorian Neotropical forest, we assessed the spatial distribution of gaps and gap size in relation to: i) tree number at the gap edge, ii) number of tree species at the gap edge, iii) number of tree species per stem at the gap edge, iv) species similarity, v) species evenness at the gap edge, vi) size differentiation at the gap edge, vii) gap isolation and viii) species mingling at the gap edge. Our results demonstrated that the spatial distribution of gaps was random. Various gap attributes were strongly associated with gap size. The number of tree species per stem at the gap edge was negatively correlated to the gap size. Gap sizes up to 50 m2 were mostly sufficient to generate tree species-rich forest stands. Assuming that our results were representative for an old-growth neotropical rainforest in Ecuador, our study remarks the following management recommendations: 1) Rainforests have a very complex spatial and diversity structure and logging activities should preferably be omitted because of adverse effects. 2) If logging is inevitable, this should mimic a random choice of trees and tree species, to prevent special selection of tree dimension and species; and a random distribution of trees to be logged, to produce gaps smaller than 50 m2 and never larger than 400 m2. Additionally, we suggest cutting not more than 5 % of the tree biomass per 10-20 years period, to preclude stronger alterations of ecosystem processes, and the reduction of existing dead wood from the ecosystem. Rev. Biol. Trop. 66(1): 149-163. Epub 2018 March 01. [ABSTRACT FROM AUTHOR]

Neighborhood-based indices such as mingling index and diameter differentiation are a set of diversity measures that are based on the relationship between a reference tree and a certain number of nearest neighbors (i.e., trees to which it has the lowest horizontal distance). Using stem-mapped data from eight headwater sites, we compared the relative bias and relative root mean square error (relative to the true mean of each site) of several different methods of choosing reference trees for calculation of diameter differentiation () and species mingling () index. Indices were defined using two, three, and four neighbors and methods for selection of the reference tree were random selection of a tree in a fixed-radius plot (FI), random selection of a tree in a variable-radius plot (VA), azimuth selection method (AZ), and nearest tree selection (NT). In general, the relative bias was lower than ±2.5% for and lower than ±10% for regardless of the method. The FI method consistently had the lowest relative bias and relative root mean squared error. The NT and AZ methods were second in terms of relative root mean squared error for and , respectively. Simplicity of these two methods might outweigh their slightly worse performance. [ABSTRACT FROM AUTHOR]