Silviculture & Sustainable Forest Management
CATEGORY 4 RESEARCH TOPICS
- Enhancing productivity of forest plantations while recycling carbon
- Estimating above ground carbon stocks and carbon changes in forests – an error analysis for the optimization of assessment schemes
- Forest restoration using direct seeding
- Gap dynamics and litter decomposition of unmanaged European beech forests
- Towards a new tropical silviculture: thresholds for sustainable production, carbon storage and biodiversity
- Transformation and functions of low molecular weight organic substances in forest soils
There is growing evidence of the effectiveness of adding biochar, produced by pyrolysis of biomass, to soils as one means of reducing atmospheric CO2 concentration, thereby contributing to climate change mitigation. This is primarily due to the highly recalcitrant nature of biochar that slows the rate at which photosynthetically-fixed carbon is returned to the atmosphere as a result of total combustion. Biochar also offers several co-benefits such as improving agricultural productivity in low-fertility soils, and improving the water-holding capacity of soils. Biochar use is limited or absent in forest plantations, which are often established on marginal infertile lands that would benefit from soil amendment measures. Key research questions are: (i) Which feedstock types or combinations can be used sustainably for producing high quality biochar, (ii) What is the optimal biochar level for enhancing productivity of plantations and how does this vary with soil properties, (iii) How does the effect of biochar application vary amongst plantation species with different functional traits (e.g. mycorrhizal and N-fixation symbioses), and (iv) How could the properties and effectiveness of biochar be assessed rapidly (e.g. Near Infrared Spectroscopy). The project will provide new evidence on how biochar can best be selected and used to enhance plantation productivity while recycling carbon back to the terrestrial ecosystem.
Principal supervisor at Swedish University of Agricultural Sciences
Co-supervisor at Bangor University
Currently discussed payment schemes for forest carbon enhancement are based on the reliable and verifiable estimation of carbon stocks and carbon stock changes. However, carbon stocks in forests cannot be directly measured. Their assessment is a complex blend of measurements, model based predictions and sample based estimates that results from various different data sources of varying quality. The eventual residual variability of the final results is an outcome of many error components which occur at all stages of the estimation process. The structure of this error propagation is not yet well understood. If, however, an optimal resource allocation is at stake with the aim to achieve the best marginal improvement of overall precision per additional Euro invested, we need to know how the single sources of variability contribute to the total error.
The candidate will work on that topic (i) with simulated data, and (ii) with real data of a carbon stock inventory. The research question is of methodological character and is on the identification, quantification and analysis of all error sources in carbon stock inventories, which includes errors in measurements of tree and forest variables, model errors of biomass models, classification errors and co-registration errors in remote sensing, modelling errors when linking remotely sensed data to field observations and errors from sampling. The successful applicant should have (i) a strong interest and background in quantitative methods, and (ii) be successfully graduated a field related to the management of natural resources (e.g. forestry). Knowledge and some skills in descriptive statistics, sampling statistics, statistical modelling, computer programming are expected.
Principal Supervisor at University of Göttingen
Co-supervisor at Swedish University of Agricultural Sciences
4.3 Forest restoration using direct seeding
In response to changing climate and to threats against biodiversity, forest restoration has become increasingly common during the past decades. However, in spite of much interest in forest restoration, little research has been done on cost-efficient alternatives to planting. Enrichment planting of valuable tree species, the most commonly used method, is expensive and alternative methods are needed. When successful, direct seeding may reduce the regeneration cost by half compared to planting. At present this method seems to suffer from disadvantages, the main two being predation on seeds by granivorous rodents and competition from herbaceous vegetation during seedling establishment. The aim of this interdisciplinary research project is to find non-harmful countermeasures against seed predation and competition from natural vegetation. The following hypotheses will be tested: (i) Seed predation by granivorous rodents can be controlled using environmentally friendly repellents. (ii) Vegetation control during direct seeding can be achieved without herbicides. The results will help to develop new and less expensive regeneration methods and is important for sustainable forest management. Our results are of particular interest for forest restoration in the temperate and tropical zones.
Principal Supervisor at Swedish University of Agricultural Sciences
Co-supervisor at University of Göttingen
4.4 Gap dynamics and litter decomposition of unmanaged European beech forests
Canopy gaps are an important aspect of the disturbance dynamics of many different forest types. Therefore gap dynamics has increasingly received importance for alternative approaches of forest management to create structural diverse forests. Canopy disturbance does not only provide different light conditions, but can also facilitate litter decomposition. At present the relationship between gap size and litter decomposition is not clear. Few studies have studied the long-term effects of gap dynamics on litter decomposition. At an experimental site a European beech forest where the silvicultural management had ceased in 1967, the following research questions should be answered: (i) how has gap size changed during the last 20 years, (ii) how has litter decomposition changed over time and how does it vary spatially, and (iii) how does tree regeneration diversity impact litter decomposition.
Principal Supervisor at University of Göttingen
Co-supervisor at University of Copenhagen
4.5 Towards a new tropical silviculture: thresholds for sustainable production, carbon storage and biodiversity
The sustainable management of forest resources for timber production has been seen as a potential tool for the conservation of large areas of tropical forest. However, there is widespread concern about the impact of forest ‘degradation’ through logging on ecosystem services such as carbon storage and biodiversity. For a given set of site conditions, it is essential to better understand the impacts of the intensity, spatial scale and selectivity of logging, and the wider disturbance regime, on the subsequent dynamics of timber species, biomass accumulation and biodiversity. This knowledge is required to define new and practical silvicultural recommendations that maintain productivity, tree diversity, viable habitat and ecological functions of forest ecosystems. These recommendations can make a full contribution to mitigating climate change, e.g. through REDD+ programmes. The main research questions of this study are (i) how do responses of timber stock and forest ecosystem services vary across gradients of logging intensity; i.e., do thresholds in response exist, and (ii) Are there trade-offs in management practices to prioritize timber yield and forest ecosystem services; do threshold points differ among them. The project could utilize existing networks of permanent sample plots which have been subject to a range of different logging impacts in either Amazon basin in Brazil, French Guiana, in South East Asia (Indonesia) or Central Africa.
Principal Supervisor at AgroParisTech
Co-supervisor at Bangor University
4.6 Transformation and functions of low molecular weight organic substances in forest soils
Transformation of low molecular weight organic substances (LMWOS) in soil is one of the most important processes because all high molecular substances released by decomposition of litter or by rhizodeposition pass the stage of LMWOS during their decomposition. Based on the unique feature of isotope applications, we will reveal transformation of LMWOS in soil for representatives of three main substance groups: sugars, amino acids and carboxylic acids. These LMWOS will be labelled with 14C, 13C and 15N and their fate in forest soils will be investigated including sorption, decomposition, utilization by microorganisms, as well as incorporation into soil organic matter. 13C enrichment of PLFA of microorganisms after application of 13C labelled LMWOS will show the use efficiency by various microbial groups. Mean residence times of C from individual substances in SOM will be estimated under field conditions and the stabilization of C will be compared. The results will allow specification and generalization of the fate of LMWOS in soils and are relevant for studies on SOM, microbial biomass, sorption of LMWOS and studies based on 13C natural abundance. The candidate will work on transformation studies and will investigate the rates of turnover processes in forest soils. The studies are of methodological character and are partly focused on the identification, quantification and analysis of transformation products of LMWOS and their stabilization in soils. We will evaluate differences between forest soils concerning the fate and transformation rates of LMWOS and so, will access their contribution to C stabilization in soil. The successful applicant should have (i) a strong interest and background in quantitative analytical methods, and (ii) be successfully graduated a field related to the geoecology, soil science, biogeochemistry and/or nutrient cycles. Knowledge and some skills in isotopic applications, statistics, and experience of work in laboratory and field are expected.
Principal Supervisor at University of Göttingen
Co-supervisor at Bangor University
Erasmus Mundus Secretariat, - last update:17 May 2011