Detecting Plant Functional Traits of Grassland Vegetation Using Spectral Reflectance Measurements

Changes in climate and an intensified agricultural use threaten grassland ecosystems in many places. To allow an efficient conservation of grassland vegetation communities, ecologists monitor variations in their plant functional traits (FTs). FTs are morphological, physiological or phenological properties of plants, which are measured at the individual plant level. However, manual measurements of FTs are costly as well as time-consuming and often require destructive sampling techniques. Grassland ecologists and agronomists are thus seeking for novel methods to monitor and map grassland FTs. Remote sensing (RS) may provide a solution to the mentioned problems and allows to collect spatially contiguous and multitemporal information on FTs. To test the performance of RS systems for detecting FTs, the Rengen Grassland Experiment in Germany was selected as study site. Due to more than 70 years of constant fertilization along a gradient from limed only to fully fertilized (treated with lime, nitrogen, phosphorus and potassium), five different plant communities have developed, which differ in their FTs. The spectral reflectance of these plant communities was collected for a period of three years using an ASD Field Spec 3 (FS3) spectroradiometer. Furthermore, 23 different FTs were measured using manual sampling methods. Firstly, it was investigated if and how the five grassland communities can be distinguished using 15 different remotely sensed vegetation indices (VIs). It was found that the performance of single VIs for differentiating the studied plant canopies fluctuates over time. Consequently, it was not possible to distinguish the communities with high accuracy throughout all phases of their phenological development using one VI. To solve this problem, a multi-VI approach using the random forests algorithm is proposed, which automatically selects the ideal sets of VIs for distinguishing grasslands. This technique allows a stable and accurate classification of grassland communities for the entire growing season. Secondly, it was studied how well the FTs of the different grassland communities can be estimated based on FS3 data. Using partial least squares regression (PLSR) it was possible to create one single model for estimating one FT of all studied grassland canopies at all phenological stages based on the spectral reflectance. Among the 23 investigated FTs, nine were modelled with R squared in validation (R2val) larger than 0.6, four with R2val larger than 0.4 and 10 with R2val lower than 0.4. It is concluded that RS allows a cost-efficient, time-saving and non-destructive monitoring of many FTs for a range of plant communities. Thirdly, the potential of different RS systems for detecting FTs was assessed. Based on spectral reflectance data recorded with a full-range FS 3, the bands of two hyperspectral and three multispectral RS sensors were simulated. Using PLSR and hyperspectral RS, 13 FTs were modeled with R2val larger than 0.4 using FS 3, 11 using EnMAP and ten using ASD HandHeld 2 data. Based on multispectral information, R2val larger than 0.4 were reached with Sentinel-2 for nine, Landsat 7 for four and RapidEye for none of the 23 FTs. These results show that hyperspectral RS systems outperform multispectral systems in detecting the FTs of grassland vegetation. It is concluded that hyperspectral RS systems have the potential to collect spatio-temporal information on grassland FTs. Such information may support grassland scientists in adapting the management to changes in climate and land-use intensity and to secure a sustainable agricultural production

Laser time-transfer and space-time reference in orbit

A high performance Space-Time Reference in orbit could be realized using a stable atomic clock in a precisely defined orbit and linking that to high accuracy atomic clocks on the ground using a laser based time-transfer link. This would enhance performance of existing systems and provide unique capabilities in navigation, precise timing, earth sciences, geodesy and the same approach could provide a platform for testing fundamental physics in space. Precise laser time- and frequency-transfer from the ground to an orbiting satellite would make it possible to improve upon the current state of the art in timing (about 1 to 30 ns achieved with GPS) by roughly a factor of 1000 to the 1 ps level.Comment: Presented at the Sixth Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, June 17-21, 201

Observation of Large Atomic-Recoil Induced Asymmetries in Cold Atom Spectroscopy

The atomic recoil effect leads to large (25 %) asymmetries in simple spectroscopic investigations of Ca atoms that have been laser-cooled to 10 microkelvin. Starting with spectra from the more familiar Doppler-broadened domain, we show how the fundamental asymmetry between absorption and stimulated emission of light manifests itself when shorter spectroscopic pulses lead to the Fourier transform regime. These effects occur on frequency scales much larger than the size of the recoil shift itself, and have not been observed before in saturation spectroscopy. These results are relevant to state-of-the-art optical atomic clocks based on freely expanding neutral atoms.Comment: 4 pages, 3 figure

Evaluation of BIM-based LCA results for building design

Digital tools based on Building Information Modelling (BIM) provide the potential to facilitate environmental performance assessments of buildings. Various tools that use a BIM model for automatic quantity take-off as basis for Life Cycle Assessment (LCA) have been developed recently. This paper describes the first application of such a BIM-LCA tool to evaluate the embodied global warming potential (GWP) throughout the whole design process of a real building. 34 states of the BIM model are analysed weekly. The results show that the embodied GWP during the design phase is twice as high as for the final building. These changes can be mainly attributed to the designers\u27 approach of using placeholder materials that are refined later, besides other reasons. As such, the embodied GWP is highly overestimated and a BIM-based environmental assessment during the design process could be misleading and counterproductive. Finally, three alternatives to the established automatic quantity take-off are discussed for future developments

A Pathway to Climate Neutral Buildings：Definitions, Policy and Stakeholder Understanding in Sweden and China

In recent years, \u27climate neutral buildings\u27 has become one of the most popular emerging terms in the context of global warming and the built environment. However, due to a vague definition, the term still lacks real-world uptake in practice. While initial research focuses on \u27climate neutral buildings\u27, few have discussed this term from the perspective of different countries or stakeholders. To address this gap, this paper explores the current understanding and future development of the term \u27climate neutral buildings\u27 in Sweden and China. Through a literature review of related definitions, an investigation of current regulations, and stakeholder interviews in both countries, we find that Sweden and China are in different stages of development towards climate neutral buildings. Sweden seems to surpass China in terms of theoretical research, regulation development and stakeholder understanding. Despite this, the two countries share similar issues regarding the future development of climate neutral buildings. Both countries lack an official interpretation of \u27climate neutral buildings\u27, sufficient regulations, and collaborations among different stakeholders. This paper suggests a foundation for the future development of climate neutral buildings

Stable isotopic analysis of atmospheric methane by infrared spectroscopy by use of diode laser difference-frequency generation

An infrared absorption spectrometer has been constructed to measure the stable isotopic composition of atmospheric methane samples. The spectrometer employs periodically poled lithium niobate to generate 15 μW of tunable difference-frequency radiation from two near-infrared diode lasers that probe the ν3 rotational-vibrational band of methane at 3.4 μm. To enhance the signal, methane is extracted from 25 l of air by use of a cryogenic chromatographic column and is expanded into the multipass cell for analysis. A measurement precision of 12‰ is demonstrated for both δ13C and δD

Effects of Sustainability Policy – Evaluating Social Consequences of Carbon Targets using Trip Completion Rates

Sustainability is widely recognised as having social, economic, and environmental dimensions. Strategies to combat global climate change inherently have an environmental focus. However, in line with the sustainability agenda, the social and economic dimensions must also be addressed. Evaluating the social consequences of decisions is often challenging due to a lack of relevant tools and indicators to measure and track them. This paper presents the Trip Completion Rate (TCR) as an indicator currently under development to evaluate the social consequences of climate change policies such as Personal Carbon Allowances (PCA). TCR is an accessibility indicator that evaluates the proportion of a population that can perform their daily activities against a performance metric. Two examples demonstrate the sensitivity of social impacts based on the geographic and demographic variations in different locations, one at the region level and another at the municipal level, through a national household travel survey (NHTS). The V\ue4stra G\uf6taland region of Sweden is taken as a test case to illustrate how the indicator may be used, comparing TCR on the entire region and then comparing it to TCRscalculated at the municipal level. The greenhouse gas emissions of the trips are calculated based on assumptions for different modes of transport. Finally, the results are evaluated against a hypothetical PCA based on the climate goals for the city of Gothenburg, Sweden. The results show that the ability to satisfy one\u27s daily travel needs depends on individual characteristics such as behavioural patterns of travel, travel mode choices and access to local amenities. We find that PCAs may disproportionately affect certain groups more than others. Policymakers must understand who is most affected by sustainability targets to ensure that disproportionately affected groups have an equal opportunity to achieve their daily needs and that adequatemeasures are taken to mitigate the local policy effects on social equity

Procedural digital twin generation for co-creating in VR focusing on vegetation

An early-stage development of a Digital Twin (DT) in Virtual Reality (VR) is presented, aiming for civic engagement in a new urban development located in an area that is a forest today. The area is presently used for recreation. For the developer, it is important both to communicate how the new development will affect the forest and allow for feedback from the citizen. High quality DT models are time-consuming to generate, especially for VR. Current model generation methods require the model developer to manually design the virtual environment. Furthermore, they are not scalable when multiple scenarios are required as a project progresses. This study aimed to create an automated, procedural workflow to generate DT models and visualize large-scale data in VR with a focus on existing green structures as a basis for participatory approaches. Two versions of the VR prototype were developed in close cooperation with the urban developer and evaluated in two user tests. A procedural workflow was developed for generating DT models and integrated into the VR application. For the green structures, efforts focused on the vegetation, such as realistic representation and placement of different types of trees and bushes. Only navigation functions were enabled in the first user test with practitioners (9 participants). Interactive functions were enabled in the second user test with pupils (age 15, 9 participants). In both tests, the researchers observed the participants and carried out short reflective interviews. The user test evaluation focussed on the perception of the vegetation, general perception of the VR environment, interaction, and navigation. The results show that the workflow is effective, and the users appreciate green structure representations in VR environments in both user tests. Based on the workflow, similar scenes can be created for any location in Sweden. Future development needs to concentrate on the refinement of buildings and information content. A challenge will be balancing the level of detail for communication with residents