Evidence of Si–O–C bonds in cellulosic materials modified by sol–gel-derived silica

The present study contributes to the controversial discussion in the literature whether Si–O–C bonds in wood–silica–gel composites exist. ¹³C NMR is a suitable method to proof such bonds. Because of the low concentration of ¹³C isotopes in natural wood, ¹³C cellulose was used as ¹³C-enriched substitute. A tailored sol for the impregnation of that cellulose was chosen by liquid ²⁹Si NMR pre-investigations of various sols whose reactivity and stability were time-dependently analysed. It is based on a sub-stoichiometric hydrolysis of tetraethoxysilane (TEOS) with 1 mol water per mol TEOS. Thermal analyses were performed to show a comparability of the thermal behaviour of wood–silica–gel and cellulose–silica–gel composites. There are two strong hints of the existence of stable Si–O–C bonds: (1) by thermal analysis, a shift in the fire behaviour of 100 K can be observed with a change in pyrolysis behaviour of the composite and (2) the proof by REDOR NMR that a dipolar coupling between ²⁹Si and ¹³C nuclei exists.     

Spatially explicit assessment of carbon stocks of a managed forest area in eastern Germany

The Kyoto-protocol permits the accounting of changes in forest carbon stocks due to forestry. Therefore, forest owners are interested in a reproducible quantification of carbon stocks at the level of forest management units and the impact of management to these stocks or their changes. We calculated the carbon stocks in tree biomass and the organic layer including their uncertainties for several forest management units (Tharandt forest, Eastern Germany, 5,500 ha) spatially explicit at the scale of individual stands by using standard forest data sources. Additionally, soil carbon stocks along a catena were quantified. Finally, carbon stocks of spruce and beech dominated stands were compared and effects of thinning intensity and site conditions were assessed. We combined forest inventory and data of site conditions by using the spatial unions of the shapes (i.e., polygons) in the stand map and the site map. Area weighted means of carbon (C) stocks reached 10.0 kg/m2 in tree biomass, 3.0 kg/m2 in the organic layer and 7.3 kg/m2 in mineral soil. Spatially explicit error propagation yielded a precision of the relative error of carbon stocks at the total studied area of 1% for tree biomass, 45% for the organic layer, and 20% for mineral soil. Mature beech dominated stands at the Tharandt forest had higher tree biomass carbon stocks (13.4 kg/m2) and lower organic layer carbon stocks (1.8 kg/m2) compared to stands dominated by spruce (11.6, 3.0 kg/m2). The difference of tree biomass stocks was mainly due to differences in thinning intensity. The additional effect of site conditions on tree carbon stocks was very small. We conclude that the spatially explicit combination of stand scale inventory data with data on site conditions is suited to quantify carbon stocks in tree biomass and organic layer at operational scale.     

Ruling out genetic erosion in <Emphasis Type="Italic">Picea chihuahuana</Emphasis> Martínez

Genetic erosion has been variously defined as the loss of particular alleles, the reduction in richness of the total number of alleles, and the reduction in evenness of the frequencies of alleles in a given place within populations or across species. Picea chihuahuana Martínez is an endangered endemic species known to occur in at least 40 locations along the Sierra Madre Occidental, in the states of Durango and Chihuahua (Mexico), but covering a total area of no more than 300 ha. The total number of individuals has been estimated to be around 42,600, and the number of mature individuals may be <2500. The populations (including mature trees, saplings and seedlings) vary in size from 21 to 5546 individuals. It has been suggested that small populations may be more susceptible to loss of genetic variability via genetic erosion caused by genetic drift, endogamy depression and strong unidirectional selection. The predicted reduction and eventual disappearance of a suitable habitat for P. chihuahuana due to climatic change imposes an additional risk of extinction. The principal aim of this study was therefore to estimate genetic erosion in 14 populations of P. chihuahuana Martínez by comparing genetic diversity across diameter at breast height classes (as a proxy for age classes) by using AFLP markers and four indices of genetic diversity that are commonly applied in combination with dominant genetic markers. No evidence of genetic erosion was found in the 14 P. chihuahuana populations analyzed.     

High-resolution images and drone-based LiDAR reveal striking patterns of vegetation gaps in a wooded spinifex grassland of Western Australia

Landscape Ecology - Vegetation patterns in hummock grasslands of Australia’s arid interior can be very complex. Additionally, the grasslands are interspersed with variable amounts of trees...     

Capability of the ‘Ball-Berry’ model for predicting stomatal conductance and water use efficiency of potato leaves under different irrigation regimes

The capability of the ‘Ball-Berry’ model (BB-model) in predicting stomatal conductance (g_s) and water use efficiency (WUE) of potato (Solanum tuberosum L.) leaves under different irrigation regimes was tested using data from two independent pot experiments in 2004 and 2007. Data obtained from 2004 was used for model parameterization, where measurements of midday leaf gas exchange of potted potatoes were done during progressive soil drying for 2 weeks at tuber initiation and earlier bulking stages. The measured photosynthetic rate (A_n) was used as an input for the model. To account for the effects of soil water deficits on g_s, a simple equation modifying the slope (m) based on the mean soil water potential (Ψ_s) in the soil columns was incorporated into the original BB-model. Compared with the original BB-model, the modified BB-model showed better predictability for both g_s and WUE of potato leaves on the parameterization data set. The models were then tested using the data from 2007 where plants were subjected to four irrigation regimes: non-irrigation (NI), full irrigation (FI), partial root-zone drying (PRD), and deficit irrigation (DI) for 3 weeks during tuber initiation and earlier bulking stages. The simulation results showed that the modified BB-model better simulated g_s for the NI and DI treatments than the original BB-model, whilst the two models performed equally well for predicting g_s of the FI and PRD treatments. Although both models had poor predictability for WUE (0.47 < r² < 0.71) of potato leaves, the modified BB-model was able to distinguish the effects of the irrigation regimes on WUE being that the WUE was generally greater for PRD than for FI and DI plants. Conclusively, the modified BB-model is capable of predicting g_s and of accounting for the differential effects of irrigation regimes on WUE of potato leaves. This information is valuable for further simulating potato water use thereby optimizing WUE under field conditions.     

Seroprevalence of Taenia saginata cysticercosis in the federal state of Lower Saxony in Germany

Based on ELISA results from randomly selected serum samples taken from 128 cattle from different administrative and urban districts in the federal state of Lower Saxony in Germany a seroprevalence estimate of Taenia saginata cysticercosis in this area was derived. This estimate was subsequently used to calculate the sample size required in an epidemiological study to determine the actual prevalence of this infection in the cattle population (n = 2 604 767) in this federal state. The sample size was calculated as 1518 and the samples were collected according to the distribution of cattle among the 48 administrative and urban districts in Lower Saxony. The samples were tested with an evaluated antibody ELISA. The results showed a positive antibody titre rate of 8.83% from the total tested samples.     

Comparing different forest zoning options for landscape-scale management of the boreal forest: Possible benefits of the TRIAD

Forest management has been criticised in the last 20 years for its negative impact on the native species, structures and functions of the forest. Of many possible alternatives proposed to minimize these effects, the functional zoning (or TRIAD) approach is gaining popularity in North America. The goal of this approach is to minimize the negative environmental impacts of forestry while maintain timber supply by dividing the forest into three broad land-use zones: (1) conservation, (2) ecosystem management, and (3) wood production. In this study, we used a spatially explicit landscape model to simulate the effects of fire and six different forest management scenarios on a boreal mixedwood forest management unit in central Quebec. The management scenarios examined included the current practices scenario, a scenario proposed by the provincial government, and four TRIAD scenarios varying in the amount of forest allocated to each of the three zones. For each scenario, we examined the harvest volume, percentage old-growth forest or old forest managed to favour old-growth attributes, and effective mesh size of forest patches by 20-year age classes. With more area set aside for conservation and high-retention partial cut harvesting techniques designed to maintain the attributes of old-growth stands, all TRIAD scenarios resulted in higher percentages of stands with old-growth attributes than the current practices scenario and the government proposed scenario, and two of the four TRIAD scenarios also resulted in higher harvest volume over the long term. All forest management scenarios resulted in significantly lower effective mesh size than the fire-only scenario, but this difference was not as pronounced for the four TRIAD scenarios as for the current practice and government proposed scenarios. We conclude that the TRIAD approach has the potential to minimize some of the negative impacts of forestry on the landscape, while maintaining timber supply over the long term.     

The Viability of Metapopulations: Individual Dispersal Behaviour Matters

Metapopulation models are frequently used for analysing species–landscape interactions and their effect on structure and dynamic of populations in fragmented landscapes. They especially support a better understanding of the viability of metapopulations. In such models, the processes determining metapopulation viability are often modelled in a simple way. Animals’ dispersal between habitat fragments is mostly taken into account by using a simple dispersal function that assumes the underlying process of dispersal to be random movement. Species-specific dispersal behaviour such as a systematic search for habitat patches is likely to influence the viability of a metapopulation. Using a model for metapopulation viability analysis, we investigate whether such specific dispersal behaviour affects the predictions of ranking orders among alternative landscape configurations rated regarding their ability to carry viable metapopulations. To incorporate dispersal behaviour in the model, we use a submodel for the colonisation rates which allows different movement patterns to be considered (uncorrelated random walk, correlated random walk with various degrees of correlation, and loops). For each movement pattern, the landscape order is determined by comparing the resulting mean metapopulation lifetime T_m of different landscape configurations. Results show that landscape orders can change considerably between different movement patterns. We analyse whether and under what circumstances dispersal behaviour influences the ranking orders of landscapes. We find that the ‘competition between patches for migrants’ – i.e. the fact that dispersers immigrating into one patch are not longer available as colonisers for other patches – is an important factor driving the change in landscape ranks. The implications of our results for metapopulation modelling, planning and conservation are discussed.     

Improving contract design and management for urban green-space maintenance through action research

The provision of services related to green-space maintenance, such as grass cutting, tree pruning, litter collection, or weed control, is an integrated part of urban green-space management. Since contracting out has become common practice in urban green-space management, it is now a key challenge to develop well-functioning frameworks for managing the provision of outsourced green-space maintenance. With the public sector reform of the New Public Management, an emphasis on the four tenets of specification, pricing, monitoring, and enforcement of service provisions is now pervasive in the ‘standard framework’ for contract design and management. Based on an action research intervention, this paper puts forward an ‘extended’ framework for the design and management of green-space maintenance contracts that can help managers of urban green space to devise contract designs and management practices better adapted for green-space maintenance. The action research intervention took place as a part of efforts by the Danish Palaces and Properties Agency to improve green-space maintenance contracting in historic parks and gardens by implementing a performance management scheme. In addition to assessing the merits of the performance management scheme, the paper focuses on a new set of tenets related to the role of coordination, communication, motivation, and restraint of power.