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Grow slowly, persist, dominate-Explaining beech dominance in a primeval forest.

ABSTRACT: Being able to persist in deep shade is an important characteristic of juvenile trees, often leading to a strong dominance of shade-tolerant species in forests with low canopy turnover and a low disturbance rate. While leaf, growth, and storage traits are known to be key components of shade tolerance, their interplay during regeneration development and their influence on juveniles' survival time remains unclear. We assessed the ontogenetic effects of these three traits on the survival time of beech (Fagus sylvatica), and Norway and sycamore maples (Acer pseudoplatanus, Acer platanoides) in a primeval beech forest. Biomass allocation, age, and content of nonstructural carbohydrates (NSC) were measured in the stems and roots of 289 seedlings and saplings in high- and low-vitality classes. Saplings experienced a trade-off between absolute growth rate (AGR) and storage (NSC) as the leaf area ratio (LAR) decreases with biomass development. High LAR but low AGR and low NSC corresponded to beech with a marked ability to persist in deep shade while awaiting canopy release. In turn, a comparably small LAR in combination with a high AGR and higher storage (NSC), as observed in Norway maple and sycamore maple, reduced sapling survival time, thus offering an explanation for beech dominance and maple disappearance in the undergrowth of old-growth beech forests.

SUBMITTER: Petrovska R

PROVIDER: S-EPMC8328449 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND:Old-growth and primeval forests are passing through a natural development cycle with recurring stages of forest development. Several methods for assigning patches of different structure and size to forest development stages or phases do exist. All currently existing classification methods have in common that a priori assumptions about the characteristics of certain stand structural attributes such as deadwood amount are made. We tested the hypothesis that multivariate datasets of primeval beech forest stand structure possess an inherent, aggregated configuration of data points with individual clusters representing forest development stages. From two completely mapped primeval beech forests in Albania, seven ecologically important stand structural attributes characterizing stand density, regeneration, stem diameter variation and amount of deadwood are derived at 8216 and 9666 virtual sampling points (moving window, focal filtering). K-means clustering is used to detect clusters in the datasets (number of clusters (k) between 2 and 5). The quality of the single clustering solutions is analyzed with average silhouette width as a measure for clustering quality. In a sensitivity analysis, clustering is done with datasets of four different spatial scales of observation (200, 500, 1000 and 1500 m2, circular virtual plot area around sampling points) and with two different kernels (equal weighting of all objects within a plot vs. weighting by distance to the virtual plot center). RESULTS:The clustering solutions succeeded in detecting and mapping areas with homogeneous stand structure. The areas had extensions of more than 200 m2, but differences between clusters were very small with average silhouette widths of less than 0.28. The obtained datasets had a homogeneous configuration with only very weak trends for clustering. CONCLUSIONS:Our results imply that forest development takes place on a continuous scale and that discrimination between development stages in primeval beech forests is splitting continuous datasets at selected thresholds. For the analysis of the forest development cycle, direct quantification of relevant structural features or processes might be more appropriate than classification. If, however, the study design demands classification, our results can justify the application of conventional forest development stage classification schemes rather than clustering.

Project description:IntroductionTobacco production continues to increase in low- and middle-income countries creating complications for tobacco control efforts. There is the need to understand and address the global tobacco leaf supply as a means of decreasing tobacco consumption and improving farmers livelihoods in line with Article 17 of the WHO Framework Convention on Tobacco Control. This study aims to understand the reasons why farmers grow tobacco and identify factors that influence these reasons.MethodsPrimary survey data (N = 1770) collected in Kenya, Malawi, and Zambia in the 2013-2014 farming season. Data analysis uses both descriptive and multinomial logistical regression methods.ResultsMajority of farmers started and are currently growing tobacco because they believed it was the only economically viable crop. Compared with Malawi, farmers in Kenya and Zambia have a 0.2 and 0.4 lower probability of growing tobacco, respectively because they perceive it as the only economically viable crop, but a 0.04 and 0.2 higher probability of growing tobacco, respectively because they believe it is highly lucrative. There are district/county differences in the reasons provided with some districts having a majority of the farmers citing the existence of a ready market or incentives from the tobacco industry. Statistically significant factors influencing these reasons are the educational level and age of the household head, land allocated to tobacco and debts.ConclusionThere is the need to address the unique features of each district to increase successful uptake of alternative livelihoods. One consistent finding is that farmers' perceived economic viability contributes to tobacco growing.ImplicationsThis study finds that perceived economic viability of tobacco is the dominant factor in the decisions to grow tobacco by smallholder farmers in Malawi, Kenya, and Zambia. There is the need to more deeply understand what contributes to farmers' perceived viability of a crop. Understanding and addressing these factors may increase the successful uptake of alternative livelihoods to tobacco. Furthermore, this study demonstrates that a one-size fits all alternative livelihood intervention is less likely to be effective as each district has unique features affecting farmers' decisions on growing tobacco.

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Grow slowly, persist, dominate-Explaining beech dominance in a primeval forest.

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