Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2021
Abstract
Management of Earth’s surface albedo is increasingly viewed as an important climate change mitigation strategy both on (Seneviratne et al., 2018) and off (Field et al., 2018; Kravitz et al., 2018) the land. Assessing the impact of a surface albedo change involves employing a measure like radiative forcing (RF) which can be challenging to digest for decision-makers who deal in the currency of CO2- equivalent emissions. As a result, many researchers express albedo change (1α) RFs in terms of their CO2-equivalent effects, despite the lack of a standard method for doing so, such as there is for emissions of well-mixed greenhouse gases (WMGHGs; e.g., IPCC AR5, Myhre et al., 2013). A major challenge for converting 1α RFs into their CO2-equivalent effects in a manner consistent with current IPCC emission metric approaches stems from the lack of a universal time dependency following the perturbation (perturbation “lifetime”). Here, we review existing methodologies based on the RF concept with the goal of highlighting the context(s) in which the resulting CO2-equivalent metrics may or may not have merit. To our knowledge this is the first review dedicated entirely to the topic since the first CO2-eq. metric for 1α surfaced 20 years ago. We find that, although there are some methods that sufficiently address the time-dependency issue, none address or sufficiently account for the spatial disparity between the climate response to CO2 emissions and 1α – a major critique of 1α metrics based on the RF concept (Jones et al., 2013). We conclude that considerable research efforts are needed to build consensus surrounding the RF “efficacy” of various surface forcing types associated with 1α (e.g., crop change, forest harvest), and the degree to which these are sensitive to the spatial pattern, extent, and magnitude of the underlying surface forcings.
Abstract
The decline of the Arctic cryosphere during recent decades has lowered the region’s surface albedo, reducing its ability to reflect solar radiation back to space. It is not clear what role the Antarctic cryosphere plays in this regard, but new remote-sensing-based techniques and datasets have recently opened the possibility to investigate its role. Here, we leverage these to show that the surface albedo reductions from sustained post-2000 losses in Arctic snow and ice cover equate to increasingly positive snow and ice albedo feedback relative to a 1982–1991 baseline period, with a decadal trend of +0.08 ± 0.04 W m–2 decade–1 between 1992 and 2015. During the same period, the expansion of the Antarctic sea-ice pack generated a negative feedback, with a decadal trend of −0.06 ± 0.02 W m–2 decade–1. However, substantial Antarctic sea-ice losses during 2016–2018 completely reversed the trend, increasing the three-year mean combined Arctic and Antarctic snow and ice albedo feedback to +0.26 ± 0.15 W m–2. This reversal highlights the importance of Antarctic sea-ice loss to the global snow and ice albedo feedback. The 1992–2018 mean feedback is equivalent to approximately 10% of anthropogenic CO2 emissions over the same period; the share may rise markedly should 2016–2018 snow and ice conditions become common, although increasing long-wave emissions will probably mediate the impact on the total radiative-energy budget.
Authors
Ricardo Ruiz-Peinado Hans Pretzsch Magnus Löf Michael Heym Kamil Bielak Jorge Aldea Ignacio Barbeito Gediminas Brazaitis Lars Drössler Kšištof Godvod Aksel Granhus Stig-Olof Holm Aris Jansons Ekaterina Makrickienė Marek Metslaid Sandra Metslaid Arne Nothdurft Ditlev Otto Juel Reventlow Roman Sitko Gintarė Stankevičienė Miren del RíoAbstract
Mixed-species stands have been found to be more productive than would be expected from the performance of their component species in monocultures due to facilitation and complementarity between species, although these interactions depend on the combination of species present. Our study focuses on monospecific and mixed-species stands of Scots pine and Norway spruce using 20 triplets established in nine countries along a climatic gradient across Europe. Differences in mean tree and stand characteristics, productivity and stand structure were assessed. Basal area increment in mixed stands was 8% higher than expected while volume increment was only 2% greater. Scots pine trees growing in mixed-species stands showed 11% larger quadratic mean diameter, 7% larger dominant diameter, 17% higher basal area and 25% higher stand volume than trees growing in monospecific stands. Norway spruce showed only a non-significant tendency to lower mean values of diameters, heights, basal area, as well standing volume in mixtures than monocultures. Stand structure indices differed between mixed stands and monocultures of Scots pine showing a greater stratification in mixed-species stands. Furthermore, the studied morphological traits showed little variability for trees growing in monospecific stands, except for diameter at breast height, crown length and crown length ratio. For trees growing in mixed stands, all the morphological traits of the trees were identified as different. Some of these morphological traits were associated with relative productivity. Nevertheless, relative productivity in mixed-species stands was not related to site conditions.
Authors
Jorge Aldea Ricardo Ruiz-Peinado Miren del Río Hans Pretzsch Michael Heym Gediminas Brazaitis Aris Jansons Marek Metslaid Ignacio Barbeito Kamil Bielak Aksel Granhus Stig-Olof Holm Arne Nothdurft Roman Sitko Magnus LöfAbstract
Mixed forests are suggested as a strategic adaptation of forest management to climate change. Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) are tree species of high economic and ecological value for European forestry. Both species coexist naturally in a large part of their distributions but there is a lack of knowledge on the ecological functioning of mixtures of these species and how to manage such stands. This paper analyses these species' intra-and inter-specific competition, including size-symmetric vs. size-asymmetric competition, and explore the effect of weather conditions on tree growth and competition. We studied basal area growth at tree level for Scots pine and Norway spruce in mixed versus pure stands in 22 triplets of fully-stocked plots along a broad range of ecological conditions across Europe. Stand inventory and increment cores provided insights into how species mixing modifies tree growth compared with neighbouring pure stands. Five different competition indices, weather variables and their interactions were included and checked in basal area growth models using a linear mixed model approach. Interspecific size-asymmetric competition strongly influenced growth for both tree species, and was modulated by weather conditions. However, species height stratification in mixed stands resulted in a greater tree basal area growth of Scots pine (10.5 cm 2 year − 1) than in pure stands (9.3 cm 2 year − 1), as this species occupies the upper canopy layer. Scots pine growth depended on temperature and drought, whereas Norway spruce growth was influenced only by drought. Interspecific site-asymmetric competition increased in cold winters for Scots pine, and decreased after a drought year for Nor-way spruce. Although mixtures of these species may reduce tree size for Norway spruce, our results suggest that this could be offset by faster growth in Scots pine. How inter-specific competition and weather conditions alter tree growth may have strong implications for the management of Scots pine-Norway spruce mixtures along the rotation period into the ongoing climate change scenario.
Abstract
Spondylosis deformans is a spinal disease common to several dog breeds, and several treatments including veterinary chiropractic may be used to treat affected dogs. Little is known, however, about the efficacy of chiropractic treatment as precautionary measure, aiming to reduce the probability of spondylosis development. We performed a randomized study where one half of the Boxer puppies from 17 litters were given veterinary chiropractic treatment at monthly intervals from eight weeks of age until they were one year old, while the other half were given no treatment (treated: n = 44, controls: n = 43). At an age of one year, spondylosis occurrence was recorded based on a scoring of X-ray images of the spine. The frequency of occurrence was significantly lower (p = 0.0478) in the treated dogs (25.0%) than in the controls (46.5%). We also tested if spondylosis occurrence in the treated dogs correlated with the average number of spinal joints with decreased mobility found per chiropractic treatment. No such effect was found, however. In summary, our results suggest that veterinary chiropractic treatment may be successfully used to reduce the probability of early development of spondylosis in young Boxers.
Abstract
In the Bramke valley (western Harz mountains, North Germany), three forested headwater catchments have been monitored since decades. A broad range of observables relevant to forestry, hydrology, hydrochemistry and ecosystem research allows to compare different approaches to environmental monitoring; each of them has its own set of relevant observables. The basic temporal resolution is daily for hydrometeorology and bi-weekly for streamwater chemistry; standing biomass of the Norway spruce stands is measured every couple of years. Tree growth (site index) has changed between and within rotation periods (of up to 129 years); changes in soil nutrient pools are typical variables used to explain this nonstationary forest growth when the spatial-temporal scales match. In hydrology, transport mechanisms of water and solutes through catchment soils are used to model and predict runoff and its chemistry. Given the homogeneity of the area in terms of geology, soils and topography as well as climate, differences between the catchments in the Bramke valley are mostly related to forestry variables. The catchments exhibit long-term changes and spatial gradients related to atmospheric deposition, management and changing climate. After providing a short multivariate summary of the dataset, we present several nonlinear metrics suitable to detect and quantify subtle changes and to describe different behavior, both between different variables from the same catchment, as well as for the same variable across catchments. Soil water potential and solution chemistry are further links between forestry and hydrology. However, at Lange Bramke, similar to other catchment studies, the evaluation of these data sets has not converged to a consistent, realistic model at the catchment scale. We hypothesize that this lack of model integration is due to theoretical rather than technical limits. A possible representation of these limits might be phrased in a category theory approach. How to cite: Hauhs, M., Meesenburg, H., and Lange, H.: Long-term monitoring of vegetation and hydrology in headwater catchments and the difficulties to embrace data-oriented and process-oriented approaches, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7684, https://doi.org/10.5194/egusphere-egu21-7684, 2021.
Authors
Jan-Peter George Wei Yang Hideki Kobayashi Tobias Biermann Arnaud Carrara Edoardo Cremonese Matthias Cuntz Silvano Fares Giacomo Gerosa Thomas Grünwald Niklas Hase Michael Heliasz Andreas Ibrom Alexander Knohl Bart Kruijt Holger Lange Jean-Marc Limousin Denis Loustau Petr Lukeš Riccardo Marzuoli Meelis Mölder Leonardo Montagnani Johan Neirynck Matthias Peichl Corinna Rebmann Marius Schmidt Francisco Ramon Lopez Serrano Kamel Soudani Caroline Vincke Jan PisekAbstract
Leaf area index (LAI) is a key ecological indicator for describing the structure of canopies and for modelling energy exchange between atmosphere and biosphere. While LAI of the forest overstory can be accurately assessed over large spatial scales via remote sensing, LAI of the forest understory (LAIu) is still largely ignored in ecological studies and ecosystem modelling due to the fact that it is often too complex to be destructively sampled or approximated by other site parameters. Additionally, so far only few attempts have been made to retrieve understory LAI via remote sensing, because dense canopies with high LAI are often hindering retrieval algorithms to produce meaningful estimates for understory LAI. Consequently, the forest understory still constitutes a poorly investigated research realm impeding ecological studies to properly account for its contribution to the energy absorption capacity of forest stands. This study aims to compare three conceptually different indirect retrieval methodologies for LAIu over a diverse panel of forest understory types distributed across Europe. For this we carried out near-to-surface measurements of understory reflectance spectra as well as digital surface photography over the extended network of Integrated Carbon Observation System (ICOS) forest ecosystem sites. LAIu was assessed by exploiting the empirical relationship between vegetation cover and light absorption (Beer-Lambert- Bouguer law) as well as by utilizing proposed relationships with two prominent vegetation indices: normalized difference vegetation index (NDVI) and simple ratio (SR). Retrievals from the three methods were significantly correlated with each other (r = 0.63–0.99, RMSE = 0.53–0.72), but exhibited also significant bias depending on the LAI scale. The NDVI based retrieval approach most likely overestimates LAI at productive sites when LAIu > 2, while the simple ratio algorithm overestimates LAIu at sites with sparse understory vegetation and presence of litter or bare soil. The purely empirical method based on the Beer-Lambert law of light absorption seems to offer a good compromise, since it provides reasonable LAIu values at both low and higher LAI ranges. Surprisingly, LAIu variation among sites seems to be largely decoupled from differences in climate and light permeability of the overstory, but significantly increased with vegetation diversity (expressed as species richness) and hence proposes new applications of LAIu in ecological modelling.
Abstract
Computer models use symbols in various ways adapted from mathematics, computer science, engineering and the natural sciences. Model applications in ecology often seek to represent future states of ecosystems, a task that has been difficult to achieve. Reflection upon the role of symbols in these models may help to disentangle the various sources and contributions to these perceptions of the environment. The modi of time (past, present, future) are here represented by corresponding forms of modelling as narration, performance, and simulation. All three occur in ecological modelling, and transitions between them may be indicative of modelling limits. Given the difficulties of representing the future of ecosystems and finding relevant analogies in the history of ecosystem use, the most challenging task for contemporary ecological models is to perform appropriately with respect to (Big) monitoring Data. We use an analogy between an environmental crisis in natural history and the current Anthropocene to demonstrate the limits of symbols in modelling which are intended to provide an abstract representation. A shift in emphasis on the engineering and computational aspect is proposed for organizing a sustainable human-environment relationship in the Anthropocene.
Authors
Jan Pisek Angela Erb Lauri Korhonen Tobias Biermann Arnaud Carrara Edoardo Cremonese Matthias Cuntz Silvano Fares Giacomo Gerosa Thomas Grünwald Niklas Hase Michal Heliasz Andreas Ibrom Alexander Knohl Johannes Kobler Bart Kruijt Holger Lange Leena Leppänen Jean-Marc Limousin Francisco Ramon Lopez Serrano Denis Loustau Petr Lukes Lars Lundin Riccardo Marzuoli Meelis Mölder Leonardo Montagnani Johan Neirynck Matthias Peichl Corinna Rebmann Eva Rubio Margarida Santos-Reis Crystal Schaaf Marius Schmidt Guillaume Simioni Kamel Soudani Caroline VinckeAbstract
Information about forest background reflectance is needed for accurate biophysical parameter retrieval from forest canopies (overstory) with remote sensing. Separating under- and overstory signals would enable more accurate modeling of forest carbon and energy fluxes. We retrieved values of the normalized difference vegetation index (NDVI) of the forest understory with the multi-angular Moderate Resolution Imaging Spectroradiometer (MODIS) bidirectional reflectance distribution function (BRDF)/albedo data (gridded 500 m daily Collection 6 product), using a method originally developed for boreal forests. The forest floor background reflectance estimates from the MODIS data were compared with in situ understory reflectance measurements carried out at an extensive set of forest ecosystem experimental sites across Europe. The reflectance estimates from MODIS data were, hence, tested across diverse forest conditions and phenological phases during the growing season to examine their applicability for ecosystems other than boreal forests. Here we report that the method can deliver good retrievals, especially over different forest types with open canopies (low foliage cover). The performance of the method was found to be limited over forests with closed canopies (high foliage cover), where the signal from understory becomes too attenuated. The spatial heterogeneity of individual field sites and the limitations and documented quality of the MODIS BRDF product are shown to be important for the correct assessment and validation of the retrievals obtained with remote sensing.
Authors
Holger LangeAbstract
No abstract has been registered