The majority of the worlds forests has undergone some form of management, such as clear-cut or thinning. This management has direct relevance for global climate: Studies estimate that forest management emissions add a third to those from deforestation, while enhanced productivity in managed forests increases the capacity of the terrestrial biosphere to act as a sink for carbon dioxide emissions. However, uncertainties in the assessment of these fluxes are large. Moreover, forests influence climate also by altering the energy and water balance of the land surface. In many regions of historical deforestation, such biogeophysical effects have substantially counteracted warming due to carbon dioxide emissions. However, the effect of management on biogeophysical effects is largely unknown beyond local case studies. While the effects of climate on forest productivity is well established in forestry models, the effects of forest management on climate is less understood. Closing this feedback cycle is crucial to understand the driving forces behind past climate changes to be able to predict future climate responses and thus the required effort to adapt to it or avert it. To investigate the role of forest management in the climate system I propose to integrate a forest management module into a comprehensive Earth system model. The resulting model will be able to simultaneously address both directions of the interactions between climate and the managed land surface. My proposed work includes model development and implementation for key forest management processes, determining the growth and stock of living biomass, soil carbon cycle, and biophysical land surface properties. With this unique tool I will be able to improve estimates of terrestrial carbon source and sink terms and to assess the susceptibility of past and future climate to combined carbon cycle and biophysical effects of forest management. Furthermore, representing feedbacks between forest management and climate in a global climate model could advance efforts to combat climate change. Changes in forest management are inevitable to adapt to future climate change. In this process, is it possible to identify win-win strategies for which local management changes do not only help adaptation, but at the same time mitigate global warming by presenting favorable effects on climate? The proposed work opens a range of long-term research paths, with the aim of strengthening the climate perspective in the economic considerations of forest management and helping to improve local decisionmaking with respect to adaptation and mitigation.
Subproject 3 will investigate the effect of shifting from continuously flooded rice cropping to crop rotation (including non-flooded systems) and diversified crops on the soil fauna communities and associated ecosystem functions. In both flooded and non-flooded systems, functional groups with a major impact on soil functions will be identified and their response to changing management regimes as well as their re-colonization capability after crop rotation will be quantified. Soil functions corresponding to specific functional groups, i.e. biogenic structural damage of the puddle layer, water loss and nutrient leaching, will be determined by correlating soil fauna data with soil service data of SP4, SP5 and SP7 and with data collected within this subproject (SP3). In addition to the field data acquired directly at the IRRI, microcosm experiments covering the broader range of environmental conditions expected under future climate conditions will be set up to determine the compositional and functional robustness of major components of the local soil fauna. Food webs will be modeled based on the soil animal data available to gain a thorough understanding of i) the factors shaping biological communities in rice cropping systems, and ii) C- and N-flow mediated by soil communities in rice fields. Advanced statistical modeling for quantification of species - environment relationships integrating all data subsets will specify the impact of crop diversification in rice agro-ecosystems on soil biota and on the related ecosystem services.
For surface soils, the mechanisms controlling soil organic C turnover have been thoroughly investigated. The database on subsoil C dynamics, however, is scarce, although greater than 50 percent of SOC stocks are stored in deeper soil horizons. The transfer of results obtained from surface soil studies to deeper soil horizons is limited, because soil organic matter (SOM) in deeper soil layers is exposed to contrasting environmental conditions (e.g. more constant temperature and moisture regime, higher CO2 and lower O2 concentrations, increasing N and P limitation to C mineralization with soil depth) and differs in composition compared to SOM of the surface layer, which in turn entails differences in its decomposition. For a quantitative analysis of subsoil SOC dynamics, it is necessary to trace the origins of the soil organic compounds and the pathways of their transformations. Since SOM is composed of various C pools which turn over on different time scales, from hours to millennia, bulk measurements do not reflect the response of specific pools to both transient and long-term change and may significantly underestimate CO2 fluxes. More detailed information can be gained from the fractionation of subsoil SOM into different functional pools in combination with the use of stable and radioactive isotopes. Additionally, soil-respired CO2 isotopic signatures can be used to understand the role of environmental factors on the rate of SOM decomposition and the magnitude and source of CO2 fluxes. The aims of this study are to (i) determine CO2 production and subsoil C mineralization in situ, (ii) investigate the vertical distribution and origin of CO2 in the soil profile using 14CO2 and 13CO2 analyses in the Grinderwald, and to (iii) determine the effect of environmental controls (temperature, oxygen) on subsoil C turnover. We hypothesize that in-situ CO2 production in subsoils is mainly controlled by root distribution and activity and that CO2 produced in deeper soil depth derives to a large part from the mineralization of fresh root derived C inputs. Further, we hypothesize that a large part of the subsoil C is potentially degradable, but is mineralized slower compared with the surface soil due to possible temperature or oxygen limitation.
Background and Objectives: The project area is located in the Ashanti Region of Ghana / West Africa in the transition zone of the moist semideciduous forest and tropical savannah zone. Main land use in this region is subsistence agriculture with large fallow areas. As an alternative land-use, forest plantations are under development by the Ghanaian wood processing company DuPaul Wood Treatment Ltd. Labourers from the surrounding villages are employed as permanent or casual plantation workers. Within three forest plantation projects of approximately 6,000 ha, DuPaul offers an area of 164 ha (referred to as Papasi Plantation) - which is mainly planted with Teak (Tectona grandis) - for research purposes. In return, the company expects consultations to improve the management for sustainable timber and pole production with exotic and native tree species. Results: In a first research approach, the Papasi Plantation was assessed in terms of vegetation classification, timber resources (in qualitative and quantitative terms) and soil and site conditions. A permanent sampling plot system was established to enable long-term monitoring of stand dynamics including observation of stand response to silvicultural treatments. Site conditions are ideally suited for Teak and some stands show exceptionally good growth performances. However, poor weed management and a lack of fire control and silvicultural management led to high mortality and poor growth performance of some stands, resulting in relative low overall growth averages. In a second step, a social baseline study was carried out in the surrounding villages and identified landowner conflicts between some villagers and DuPaul, which could be one reason for the fire damages. However, the study also revealed a general interest for collaboration in agroforestry on DuPaul land on both sides. Thirdly, a silvicultural management concept was elaborated and an improved integration of the rural population into DuPaul's forest plantation projects is already initiated. If landowner conflicts can be solved, the development of forest plantations can contribute significantly to the economic income of rural households while environmental benefits provide long-term opportunities for sustainable development of the region. Funding: GTZ supported PPP-Measure, Foundation
The project aims at achieving a better understanding of the processes that drive or limit the response of grassland systems in a world of increasing atmospheric pCO2. We will test the hypothesis that the previously shown increase in below-ground allocation of C under elevated pCO2 provides the necessary energy excess and will stimulate free-living N2 fixers in a low N grassland environment. The project thus aims at assessing the occurrence and importance of free-living N2 fixers under elevated pCO2 and identify the associated microbial communities involved in order to better understand ecosystems response and sustainability of grassland systems. This project had the last opportunity to obtain soil samples from a grassland ecosystem adapted to long-term (10 year) elevated atmospheric pCO2 as the Swiss FACE experiment. The project aims to identify the relevant components of free-living diazotrophs of the microbial community using 15N stable isotope - DNA probing.
The nature of the microbial communities inhabiting the deeper soil horizons is largely unknown. It is also not clear why subsurface microorganisms do not make faster use of organic compounds under field conditions. The answer could be provided by a reciprocal soil transfer experiment studying the response of transferred soils to fluctuations in microclimate, organic inputs, and soil biota. The subproject P9 will be responsible for the establishment of reciprocal transfer experiments offering a strong link between subgroups interested in organic matter quality, transport of organic substances, as well as functions of the soil microbial community. A single, high molecular weight substrate (13C labelled cellulose) will be applied at two different levels in the pre-experiment to understand the dose-dependent reaction of soil microorganisms in transferred surface and sub-soils. Uniformly 13C labelled beech roots - representing complex substrates - will be used for the main reciprocal soil transfer experiment. We hypothesize that transferring soil cores between subsoil and surface soil as well as addition of labelled cellulose or roots will allow us to evaluate the relative impact of surface/subsurface habitat conditions and resource availability on abundance, function, and diversity of the soil microbial community. The second objective of the subproject is to understand whether minerals buried within different soil compartments (topsoil vs. subsoil) in the field contribute to creation of hot spots of microbial abundance and activity within a period of two to five years. We hypothesize that soil microorganisms colonize organo-mineral complexes depending on their nutritional composition and substrate availability. The existence of micro-habitat specific microbial communities could be important for short term carbon storage (1 to 6 years). The third objective is to understand the biogeography and function of soil microorganisms in different subsoils. Parent material as well as mineral composition might control niche differentiation during soil development. Depending on size and interconnectedness of niches, colonization and survival of soil microbial communities might be different in soils derived from loess, sand, terra fusca, or sandstone. From the methodological point of view, our specific interest is to place community composition into context with soil microbial functions in subsoils. Our subgroup will be responsible for determining the abundance, diversity, und function of soil microorganisms (13C microbial biomass, 13C PLFA, enzyme activities, DNA extraction followed by quantitative PCR). Quantitative PCR will be used to estimate total abundances of bacteria, archaea and fungi as well as abundances of specific groups of bacteria at high taxonomic levels. We will apply taxa specific bacterial primers because classes or phyla might be differentiated into ecological categories on the basis of their life strategies.
Forests play a relevant role in mitigation of climate change. A major issue, however, is the scientifically well founded, transparent and verifyable monitoring of achievements in forest carbon sequestration through reduction of deforestation and forest degradation, and through fostering sustainable forest management. Monitoring is particularly difficult in diverse and inaccessible humid tropical forest areas. The proposed research will contribute to the improvement of forest carbon monitoring under the challenging conditions of humid tropical forests. Sample based field observations and model based biomass predictions will be linked to area-wide satellite remote sensing imagery (RapidEye) and to strip samples of LiDAR imagery. Techniques of linking these data sources will be further developed and analysed with respect to (1) precision of carbon estimation and (2) accuracy of carbon regionalization. The proposed project implies research on methodological improvements of both sample based forest inventories (resampling techniques for biomass, imputation of non-response) and remote sensing application to forest monitoring (regionalization, sample based application of LiDAR data). At the core of this research is the analysis of the error variance components that each data source brings into the system. Such error analysis will allow identifying optimal resource allocation for the efficient improvement of forest carbon monitoring systems.
Biogeochemical interfaces shape microbial community function in soil. On the other hand microbial communities influence the properties of biogeochemical interfaces. Despite the importance of this interplay, basic understanding of the role of biogeochemical interfaces for microbial performance is still missing. We postulate that biogeochemical interfaces in soil are important for the formation of functional consortia of microorganisms, which are able to shape their own microenvironment and therefore influence the properties of interfaces in soil. Furthermore biogeochemical interfaces act as genetic memory of soils, as they can store DNA from dead microbes and protect it from degradation. We propose that for the formation of functional biogeochemical interfaces microbial dispersal (e.g. along fungal networks) in response to quality and quantity of bioavailable carbon and/or water availability plays a major role, as the development of functional guilds of microbes requires energy and depends on the redox state of the habitat.To address these questions, hexadecane degradation will be studied in differently developed artificial and natural soils. To answer the question on the role of carbon quantity and quality, experiments will be performed with and without litter material at different water contents of the soil. Experiments will be performed with intact soil columns as well as soil samples where the developed interface structure has been artificially destroyed. Molecular analysis of hexadecane degrading microbial communties will be done in vitro as well as in situ. The corresponding toolbox has been successfully developed in the first phase of the priority program including methods for genome, transcriptome and proteome analysis.
In many plant species, FLOWERING LOCUS T and related proteins are the mobile signal that communicates information on photoperiod from the leaves to the shoots, where the transition to flowering is realized. FT expression is tightly controlled at the transcriptional level so that it is restricted to leaves, occurs only in appropriate photoperiods, and integrates ambient temperature and developmental cues, as well as information on biotic and abiotic stress. We previously established that FT transcription in the model plant Arabidopsis thaliana requires proximal promoter cis-elements and a distal enhancer, both evolutionary conserved among Brassicacea species. In addition, FT transcription is blocked prior vernalization in biannual accessions and vernalization-dependency of FT is controlled through a CArG-box located in the first intron that binds the transcriptional repressor FLOWERING LOCUS C (FLC). Chromatin-mediated repression by the Polycomb Group (PcG) pathway is required for photoperiod-dependent FT regulation and participates in FT expression level modulation in response to other cues.In this project, I propose to explore the available sequence data from the 1001 genome project in Arabidopsis to evaluate how often changes in regulatory cis-elements at FT have occurred and how these translate into an adaptive value. Allele-specific FT expression pattern will be measured in F1 hybrids of different accessions in response to varying environmental conditions. FT alleles that show cis-regulatory variation will be further analyzed to pinpoint the causal regulatory changes and study their effect in more detail. The allotetrapolyploid species Brassica napus is a hybrid of two Brassiceae species belonging to the A- and C-type genome, which are in turn mesopolyploid due to a genome triplication that occurred ca. 10x106 years ago. We will determine allele-specific expression of FT paralogs from both genomes of a collection of B. napus accessions. The plants will be grown in the field in changing environmental conditions to maximize the chance to detect expression variation of the paralogs. We will compare the contribution of the founder genomes to the regulation of flowering time and asses variation in this contribution. A particular focus will be to study the impact of chromatin-mediated repression on allele selection in B. napus.
In hydrology, the relationship between water storage and flow is still fundamental in characterizing and modeling hydrological systems. However, this simplification neglects important aspects of the variability of the hydrological system, such as stable or instable states, tipping points, connectivity, etc. and influences the predictability of hydrological systems, both for extreme events as well as long-term changes. We still lack appropriate data to develop theory linking internal pattern dynamics and integral responses and therefore to identify functionally similar hydrological areas and link this to structural features. We plan to investigate the similarities and differences of the dynamic patterns of state variables and the integral response in replicas of distinct landscape units. A strategic and systematic monitoring network is planned in this project, which contributes the essential dynamic datasets to the research group to characterize EFUs and DFUs and thus significantly improving the usual approach of subdividing the landscape into static entities such as the traditional HRUs. The planned monitoring network is unique and highly innovative in its linkage of surface and subsurface observations and its spatial and temporal resolution and the centerpiece of CAOS.
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