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Balancing indicators for sustainable intensification of crop production at field and river basin levels
No full textAdequate tools for evaluating sustainable intensification (SI) of crop production for agro-hydrological system are not readily available. Building on existing concepts, we propose a framework for evaluating SI at the field and river basin levels. The framework serves as a means to assess and visualise SI indicator values, including yield, water-use efficiency and nitrogen-use efficiency (NUE), alongside water and nitrogen surpluses and their effects on water quantity and quality. To demonstrate the SI assessment framework, we used empirical data for both the field level (the Static Fertilization Experiment at Bad Lauchstädt) and the river basin level (the Selke basin, 463 km2) in central Germany. Crop yield and resource use efficiency varied considerably from 1980 to 2014, but without clear trends. NUE frequently fell below the desirable range (80 kg N ha−1). For the catchment as a whole, the average nitrate-N concentration (3.6 mg L−1) was slightly higher than the threshold of 2.5 mg L−1 nitrate-N in surface water. However, weather and climate-related patterns, due to their effects on transport capacity and dilution, influenced water quantity and quality indicators more than agronomic practices. To achieve SI of crop production in the Selke basin, irrigation and soil moisture management are required to reduce yield variability and reduce N surpluses at field level. In addition, optimum application of fertiliser and manure could help to reduce the nitrate-N concentration below the set water quality standards in the Selke basin. In this way, there is scope for increase in yields and resource use efficiencies, and thus potential reduction of environmental impacts at basin level. We conclude that the framework is useful for assessing sustainable production, by simultaneously considering objectives related to crop production, resource-use efficiency and environmental quality, at both field and river basin levels.</p
Times are changing : Implications of climate change for the occurrence and predictability of tipping points
Get PDFComplex systems in ecology and the climate can have tipping points. The term ‘tipping point’ is loosely defined as a threshold point in the conditions after which runaway change brings the system to a new stable state. Such a transition can have long-term dire consequences, and therefore it is of critical importance to understand why and when these transitions occur. Under the ongoing climate change, these critical transitions are projected to increase. However, little is understood about how relative timescales of the rate of environmental change and variability affect the occurrence and detectability of these critical transitions in nature and society. The aim of this thesis is to provide some insights in how differences in these timescales may affect critical transitions. This thesis starts with the analysis of bistability of marine anoxic events in the Mediterranean Sea. Reconstructed time series have been used to detect changes in resilience indicators prior to several abrupt shifts in the past climate. This is, however, only possible under a limited set of conditions. For the past marine anoxic events in the Mediterranean Sea, these conditions are met. Recent technological advances made it possible to construct high-resolution and (almost) evenly spaced time series of past widespread anoxic events in the Mediterranean Sea. In Chapter 2, we analysed whether past transitions in the Mediterranean Sea could have been predicted using the resilience indicators autocorrelation and variance. We show that the repeated shifts into marine anoxia in the Mediterranean Sea had the character of critical transitions, because there was a gradual increase in the temporal autocorrelation and variance in the deep cores (>1600 meter depth) before the onset of most events. Our results imply that future widespread anoxia in marine systems might be recognizable using an appropriate statistical approach and high-resolution records. These shifts to an anoxic state occurred relatively fast, but not all shifts to an alternative stable state unfold rapidly. Slowly responding systems show a gradual shift to the alternative state, once the tipping point has been passed. As the rate of the current environmental change is unprecedented, more system respond relatively slow to changes in the environment. The current resilience indicators are based on the theoretical finding that the system slows down close to the tipping point. But in these relatively slow systems, the recovery rates are always slow. Therefore, it is the question whether these resilience indicators flag that a relatively slow system is approaching a tipping point. In Chapter 3, we show that it is more difficult to quantify the resilience of a system that responds relatively slow. These results indicate that as the rates of environmental change keep increasing, it become more and more difficult to detect whether systems are approaching a tipping point. Another risk under current rates of environmental change is that the rate of change in the conditions triggers a shift to an alternative stable state, whereas a change of the same magnitude but at slower rates would not. Only few studies describe this so-called ‘rate-tipping’ in ecological systems, but understanding rate-tipping is needed to understand and predict ecosystem response to the ongoing rapid environmental change. Therefore, we show in Chapter 4 that there can be rate-induced tipping for a range of initial conditions in a model of cyanobacteria with realistic parameter settings. A pulse in the environmental conditions, for example as a result of an extreme event, can cause a temporary collapse, depending on both the rate and the duration of the pulse. In addition, we showed that the type of environmental variability can influence the probability of inducing rate-tipping. These results imply that we need to incorporate critical rates of change in our ecosystems assessment and management. In addition to affecting the probability of inducing rate-tipping, environmental variability itself can bring a system past a tipping point. The variability is different in different parts of the climate, but because of climate change, the climatic variability is changing systematically in different parts of the world. Therefore, we analysed in Chapter 5 what the effect of changes in the memory of the climatic variability is on the chance of undergoing a critical transition. We show that chances of invoking such critical transitions are strongly affected by the climate memory as measured for instance by temporal autocorrelation in climatic variables. We illustrate the implications of this prediction with evidence from forests, corals reefs, poverty traps, violent conflict and ice-sheet instability. In all of these examples, the duration of anomalous dry or warm events increases the chance of invoking a critical transition. Our results imply that understanding the effects of altered climate variability requires research on climate memory. In the Afterthoughts I conclude that fast rates of environmental change and changes in environmental variability can affect the detectability and predictability of critical transitions. While the exact impacts of climate change are likely system-specific, interacting timescales make it difficult to untangle system dynamics from external forcing. The relations I describe throughout this thesis, however, are relative. This means that it is impossible to make general rules about whether resilience indicators can be observed, or if the conditions can be restored. Therefore, we should not give up on a priori detecting and reversing critical transitions driven by climate change
Biochar promotes the reduction of N<sub>2</sub>O to N<sub>2</sub> and concurrently suppresses the production of N<sub>2</sub>O in calcareous soil
No full textBiochar additions may mitigate N2O emissions from soil. The mechanisms underpinning the mitigation of emissions remain to be elucidated. A series of incubation experiments were performed to investigate the effects of biochar on N2O production and reduction in columns with a low-fertility or high-fertility soil, with or without the injection of N2O in the subsoil and with and without glucose (to stimulate denitrification). Biochar was added to the calcareous soils in 0 and 1% (w/w) amounts and moisture was maintained at 70% water-filled pore space (WFPS) over the incubation period. The results revealed that biochar reduced the emissions of soil-produced N2O by 37–47% and those of injected N2O by 23–44%. The addition of glucose solution strongly increased N2O emissions, while biochar reduced total N2O emissions by as much as 64–81% and those of injected N2O alone by 29–51%. Differences between the low-fertility and high-fertility soils in the apparent N2O emission mitigation by biochar were relatively small, but tended to be larger for the low-fertility soil. The results suggest that biochar addition can suppress the production of N2O in soil and simultaneously stimulate the reduction of N2O to N2. Further studies are needed to elucidate the regulatory effects of biochar in soil.</p
Randomized interventions and “real” treatment effects : A cautionary tale and an example
No full textThe experimental approach has revolutionized development economics. Nonetheless, randomization cannot do everything. We discuss challenges to RCTs, paying special attention to internal validity. Randomized interventions in social sciences are not double-blind and do not, in general, hold all relevant covariates constant. Treated and untreated subjects adjust their behavior in response to treatment status. Disentangling the treatment effect into its behavioral component and the direct effect of the intervention is difficult, and implies a return to the toolkit of observational studies. This is illustrated using improved seed distribution in African farming. While standard RCTs found large treatment effects, double-blind RCTs revealed that a large share of this impact is due to farmers allocating extra effort and their best plots to the cultivation of new seeds.</p
Climate conditions and spray treatments induce shifts in health promoting compounds in cherry (Prunus avium L.) fruits
No full textEffects of repeated sprayings expected to affect phenolic, anthocyanin, carotenoid and ascorbic acid content in ‘Skeena’ and ‘Sweetheart’ cherries were observed during two years (without addition of calcium (Ca) in 2015, and with Ca in 2016). A shift in phytonutrients, with higher phenolic and carotenoid- and lower ascorbic acid content was observed when comparing Ca and the control (water) treatments in 2016 compared to 2015. Higher radiation, higher temperatures and less precipitation in 2015 compared to 2016 likely contributed to this shift. Gibberellic acid (GA3), abscisic acid (ABA), salicylic acid (SA) and glycine betaine (GB) sprays increased anthocyanin content in 2015 and for ‘Skeena’ cherries in 2016. GA3 and GB induced lower carotenoid content for ‘Skeena’- in 2015 and for ‘Sweetheart’ cherries in 2016 and lowered ascorbic acid content for ‘Sweetheart’ cherries. GA3 sprays induced the largest changes, increasing anthocyanin- (42 %), lowering carotenoid (19 %) and ascorbic acid content (53 %) compared to control. Ascophyllum nodosum, one of the novel spray treatments next to GB, appears to induce an effect opposite to GB, increasing carotenoid and ascorbic acid, but lowering phenolic content. Whether these phytonutrient shifts, due to climate conditions or to spray treatments, are beneficial to consumer health is unclear.</p
Impact of water degumming and enzymatic degumming on gum mesostructure formation in crude soybean oil
No full textPhospholipid gum mesostructures formed in crude soybean oil after water degumming (WD) and enzymatic degumming (ED) were studied at a range of phospholipid and water concentrations. For ED, phospholipase C (PLC), phospholipase A2 (PLA2) and a mixture of phospholipases Purifine 3G (3G) were used. Both WD and ED resulted in lamellar liquid-crystalline phases, however, of different topology. The dependence of the bilayer spacings (as observed by SANS and SAXS) on the ratio between amount of water and amphiphilic lipids differed for WD and PLA2 ED vs PLC and 3G ED. This difference was also observed for dynamics at molecular scale as observed by time-domain (TD) NMR and attributed to partial incorporation of diglycerides and free fatty acids into gum bilayers after PLC and 3G ED. Feasibility of using TD-NMR relaxometry for quantification of the gum phase and estimation of degumming efficiency was demonstrated.</p
Green and White Asparagus (Asparagus officinalis): A Source of Developmental, Chemical and Urinary Intrigue
No full textAsparagus (Asparagus officinalis) is one of the world’s top 20 vegetable crops. Both green and white shoots (spears) are produced; the latter being harvested before becoming exposed to light. The crop is grown in nearly all areas of the world, with the largest production regions being China, Western Europe, North America and Peru. Successful production demands high farmer input and specific environmental conditions and cultivation practices. Asparagus materials have also been used for centuries as herbal medicine. Despite this widespread cultivation and consumption, we still know relatively little about the biochemistry of this crop and how this relates to the nutritional, flavour, and neutra-pharmaceutical properties of the materials used. To date, no-one has directly compared the contrasting compositions of the green and white crops. In this short review, we have summarised most of the literature to illustrate the chemical richness of the crop and how this might relate to key quality parameters. Asparagus has excellent nutritional properties and its flavour/fragrance is attributed to a set of volatile components including pyrazines and sulphur-containing compounds. More detailed research, however, is needed and we propose that (untargeted) metabolomics should have a more prominent role to play in these investigations
Cellular RNA Hubs: Friends and Foes of Plant Viruses
No full textRNA granules are dynamic cellular foci that are widely spread in eukaryotic cells and play essential roles in cell growth and development, and immune and stress responses. Different types of granules can be distinguished, each with a specific function and playing a role in, for example, RNA transcription, modification, processing, decay, translation, and arrest. By means of communication and exchange of (shared) components, they form a large regulatory network in cells. Viruses have been reported to interact with one or more of these either cytoplasmic or nuclear granules, and act either proviral, to enable and support viral infection and facilitate viral movement, or antiviral, protecting or clearing hosts from viral infection. This review describes an overview and recent progress on cytoplasmic and nuclear RNA granules and their interplay with virus infection, first in animal systems and as a prelude to the status and current developments on plant viruses, which have been less well studied on this thus far
Effects of an artificial hay aroma and compound feed formulation on feed intake pattern, rumen function and milk production in lactating dairy cows
No full textThe Kempen system is a dairy feeding system in which diet is provided in the form of a compound feed (CF) and hay offered ad libitum. Ad libitum access to CF and hay allows cows in this system to achieve a high DM intake (DMI). Out of physiological concerns, the voluntary hay intake could be increased and the consumption pattern of CF could be manipulated to maintain proper rumen functioning and health. This study investigated the effects of an artificial hay aroma and CF formulation on feed intake pattern, rumen function and milk production in mid- to late-lactating dairy cows. Twenty Holstein–Friesian cows were assigned to four treatments in a 4 × 4 Latin square design. Diet consisted of CF and grass hay (GH), fed separately, and both offered ad libitum, although CF supply was restricted in maximum meal size and speed of supply by an electronic system. Treatments were the combination of two CF formulations – high in starch (CHS) and fibre (CHF); and two GH – untreated (UGH) and the same hay treated with an artificial aroma (TGH). Meal criteria were determined using three-population Gaussian–Gaussian–Weibull density functions. No GH × CF interaction effects on feed intake pattern characteristics were found. Total DMI and CF intake, but not GH intake, were greater (P < 0.01) in TGH treatment, and feed intake was not affected by type of CF. Total visits to feeders per day, visits to the GH feeder, visits to the CF feeder and CF eating time (all P < 0.01) were significantly greater in cows fed with TGH. Meal frequency, meal size and meal duration were unaffected by treatments. Cows fed CHF had a greater milk fat (P = 0.02), milk urea content (P < 0.01) and a greater milk fat yield (P < 0.01). Cows fed TGH had a greater milk lactose content and lactose yield (P < 0.05), and milk urea content (P < 0.01). Cows fed TGH had smaller molar proportions of acetic acid and greater molar proportions of propionic acid compared with UGH. In conclusion, treatment of GH with an artificial aroma increased CF intake and total DMI, but did not affect hay intake. Additionally, GH treatment increased the frequency of visits to both feeders, and affected rumen volatile fatty acid profile. Type of CF did not affect meal patterns, ruminal pH, nor fermentation profiles
Self-organization for everyday peacebuilding: The Guardia Indígena from Northern Cauca, Colombia
No full textThe Nasa indigenous group’s Guardia Indígena, whose primary goal is to protect indigenous people and their territories from all types of armed groups, is a nonviolent self-protection organization in Northern Cauca, Colombia. On 5 November 2014, while peace talks were ongoing between the Revolutionary Armed Forces of Colombia (FARC) and the Colombian government, two Guardia Indígena members were shot dead by FARC guerrillas. Without guns or physical violence, indigenous guards captured seven guerrillas responsible for the crime, and, four days later, indigenous organizations held a trial and sentenced the rebels to imprisonment. This article describes those events and investigates how the unarmed guards managed to capture the guerrillas and bring them to trial. The self-organization concept is used to gain insights into the mechanisms and strategies deployed. The mechanisms of the Guardia Indígena include constructing and applying specific social norms and values, developing a common goal, and applying a flexible mix of centralized and decentralized ways of organizing. By combining and activating these mechanisms at carefully chosen moments, indigenous people have succeeded in organizing themselves as a collective movement that is powerful enough to confront armed groups without using violence.</p