Seedling Growth and Biomass Production under Different Light Availability Levels and Competition Types

Light availability is a crucial resource determining seedling survival, establishment, and growth. Competition for light is asymmetric, giving the taller individuals a competitive advantage for obtaining light resources. Species-specific traits, e.g., shade tolerance, rooting depth, and leaf morphology, determine their strategical growth response under limited resource availability and different competitive interactions. We established a controlled pot experiment using European beech, Norway spruce, and Douglas fir seedlings and applying three different light availability levels—10%, 20%, and 50%. The experiment’s main aim was to better understand the effects of light availability and competition type on the growth, growth allocation, and biomass production of recently planted seedlings. We planted four seedlings per pot in either monocultures or mixtures of two species. Relative height and diameter growth and aboveground woody biomass of seedlings increased with increasing light availability. All seedlings allocated more growth to height than diameter with decreasing light availability. Seedlings that reached on average greater height in the previous year allocated less growth to height in the following year. Additionally, there were general differences in growth allocation to the height between gymnosperms and angiosperms, but we did not find an effect of the competitor’s identity. Our mixture effect analysis trends suggested that mixtures of functionally dissimilar species are more likely to produce higher biomass than mixtures of more similar species such as the two studied conifers. This finding points towards increased productivity through complementarity

Height, diameter, biomass, leaf area, and relative height volume growth of European beech, Norway spruce, and Douglas fir grown in monospecific and mixed pots under different light availability levels

Light is an exceptionally important but often limited resource. Light availability determines seedling survival, establishment, and growth. Regardless of species identity, trees growing under high light availability produce more biomass and are generally larger than trees receiving less light. How stressed trees become under the conditions of limited light availability depends on species-specific factors like shade tolerance and plasticity as well as the competitive situation. Additionally, the taller individuals have the advantage to obtain more light since competition for the resource is asymmetric. In competitive environments, the niche complementarity of the coexisting species can reduce the competitive pressure and facilitate higher biomass production (i.e., positive mixing effect). We established a controlled pot experiment to study the effect of light availability and competition type on growth and its allocation, biomass production and allocation, and leaf morphology of European beech (Fagus sylvatica L.), Norway spruce (Picea abies L. Karst), and Douglas fir (Pseudotsuga menziesii Mirb. Franco) seedlings. The study site was located at the Experimental Botanical Garden of the University of Göttingen (51.55684392372871, 9.953489533796636). We planted four seedlings per pot, each pot being either monospecific or mixed (two seedlings per species) and exposed to one of three different light availability levels (10%, 20%, and 50%). We planted in a total of 576 pots – 6 species combinations (monocultures + mixtures) x 3 light treatment levels x 32 replicates. For planting, we used 1-year-old European beech and 2-year-old Norway spruce and Douglas fir seedlings that were not undercut or transplanted. The experiment lasted from April 2018 – November 2019. All seedlings received the same water treatment through an automatic dripping irrigation system. Nutrients were provided using a controlled release fertilizer (Osmocote Exact Hi.End with 12-14 month longevity (ICL SF))

Biomass Allocation and Leaf Morphology of Saplings Grown under Various Conditions of Light Availability and Competition Types

Plant growth is almost always limited by light availability and competition. However, plants are generally plastic and can change their morphology and biomass allocation to optimize growth under suboptimal conditions. We set up a controlled pot experiment with three light availability levels (10%, 20%, and 50%) to study the effect of light and competition on the biomass allocation and leaf morphology in monospecific and mixed pots of recently planted European beech (Fagus sylvatica L.), Norway spruce (Picea abies (L.) Karst.), and Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) saplings using a quantile regression model. Specific leaf area (SLA) showed the strongest reaction and increased with decreasing light availability. Woody aboveground mass fraction (AMF) increased with decreasing light availability, but the effect of light on biomass allocation was less pronounced than on SLA. The SLA, woody AMF, and root mass fraction (RMF) of the two conifer species and European beech varied greatly, with European beech having a higher SLA and RMF than the two conifer species. The associated effect of plant size on biomass allocation was small, and the strength of the association was not meaningful on a practical level. The competitor’s effect on biomass allocation was minor overall and only present for some species, suggesting that species’ functional dissimilarity does not greatly affect allocational patterns in early tree development stages

ENGINEERING FOR RURAL DEVELOPMENT TECHNOLOGICAL PROCESS OF SEWAGE SLUDGE DE-WATERING BY IMPULSE METHOD AND ASSESMENT OF OPTIONS TO USE DRIED MATERIAL

Abstract. Waste water sewage sludge is one of municipal waste materials that could be used for nutrient recycling in agriculture, plantation forestry or re-cultivated areas. Sewage sludge contains at least 80 % of water and nutrient rich organic materials what could be used for fertilization of bare soils or for energy production instead of landing on landfills. The de-watering process of sludge by using the impulse method has less energy consumption and higher content of dry matter in the final product is reached in comparison with traditional drying. The aim of the study is to elaborate a method for sewage sludge drying, which allows saving the biological value of final organic material. Impulse interval, frequency, air pressure and temperature in the camera are the key factors for an economically effective process and reaching of qualitative final product. The product could be used for fertilization of non-food products, tree planting, perennial grasses for seed production etc. If sludge contains too high concentration of heavy metals, it could be burned for energy production, and just ashes deponent on landfills. The technological and energy consumption aspects of the methods were analyzed. For sewage sludge containing a low content of heavy metals. Drying is more sustainable after -and pretreatment methods before recycling of plant nutrient elements included in sludge organic material for farming. Transport of dried material is more economical as fresh mass, as well dry material does not smell. The barriers for implementation of these technologies into common practice are more political than technical. Keywords: waste water sewage sludge, pneumatic pulse method. Introduction Sewage sludge is one of municipal waste materials that could be used for nutrient recycling in agriculture, plantation forestry or re-cultivated areas. Sewage sludge contains at least 80 % of water and nutrient rich organic materials what could be used for fertilization of bare soils or for energy production instead of landing on landfills Three methods are mainly applied: convective drying, conductive drying and solar drying, each one presenting different characteristics For sustainable management of municipal sewage sludge not only available technologies should be taken into account, but also other parameters, such as policy regulations and socio-economic issues. Some authors think that drying is too simple solution and the next generation technologies should be used, for example, pyrolysis seems to be the optimal thermochemical treatment option compared to incineration and gasification. Pyrolysis of a deposit of sewage favors to energy saving, restoration of materials and production of high-grade materials, providing the decision "without a wastage". Pyrolysis of ooze is an innovative process, which can transform both the crude and digested ooze to useful bioenergy in the form of naphtha and gas, forming biochar as by-product, which is ecologically steady and has the capacity for binding of carbon and conditioning of the soil, and also for the absorptive production Successful seeding and planting efforts on degraded sites, after fertilization and soil cultivation are reasons to believe that natural seeding can supplement or even replace artificial stand establishment [1; 5]. Organic residues contain plant nutrient elements and after adequate treatment are suitable for using as fertilizer

Examination of aboveground attributes to predict belowground biomass of young trees

International audienceJust as the aboveground tree organs represent the interface between trees and the atmosphere, roots act as the interface between trees and the soil. In this function, roots take-up water and nutrients, facilitate interactions with soil microflora, anchor trees, and also contribute to the gross primary production of forests. However, in comparison to aboveground plant organs, the biomass of roots is much more difficult to study. In this study, we analyzed 19 European datasets on above- and belowground biomass of juvenile trees of 14 species to identify generalizable estimators of root biomass based on tree sapling dimensions (e.g. height, diameter, aboveground biomass). Such estimations are essential growth and sequestration modelling. In addition, the intention was to study the effect of sapling dimension and light availability on biomass allocation to roots. All aboveground variables were significant predictors for root biomass. But, among aboveground predictors of root biomass plant height performed poorest. When comparing conifer and broadleaf species, the latter tended to have a higher root biomass at a given dimension. Also, with increasing size, the share of belowground biomass tended to increase for the sapling dimensions considered. In most species, there was a trend of increasing relative belowground biomass with increasing light availability. Finally, the height to diameter ratio (H/D) was negatively correlated to relative belowground biomass. This indicates that trees with a high H/D are not only more unstable owing to the unfavorable bending stress resistance, but also because they are comparatively less well anchored in the ground. Thus, single tree stability may be improved through increasing light availability to increase the share of belowground biomass