An agent-based approach to model land-use change at a regional scale

Land-use/cover change (LUCC) is a complex process that includes actors and factors at different social and spatial levels. A common approach to analyse and simulate LUCC as the result of individual decisions is agent-based modelling (ABM). However, ABM is often applied to simulate processes at local scales, while its application in regional studies is limited. This paper describes first a conceptual framework for ABM to analyse and explore regional LUCC processes. Second, the conceptual framework is represented by combining different concepts including agent typologies, farm trajectories and probabilistic decision-making processes. Finally, the framework is illustrated through a case study in the Netherlands, where processes of farm cessation, farm expansion and farm diversification are shaping the structure of the landscape. The framework is a generic, straightforward approach to analyse and explore regional LUCC with an explicit link to empirical approaches for parameterization of ABM.     

Early ocean distribution of juvenile Chinook salmon in an upwelling ecosystem

Extreme variability in abundance of California salmon populations is often ascribed to ocean conditions, yet relatively little is known about their marine life history. To investigate which ocean conditions influence their distribution and abundance, we surveyed juvenile Chinook salmon (Oncorhynchus tshawytscha) within the California Current (central California [37°30′N) to Newport, Oregon (44°00′N]) for a 2‐week period over three summers (2010–2012). At each station, we measured chlorophyll‐a as an indicator of primary productivity, acoustic‐based metrics of zooplankton density as an indicator of potential prey availability and physical characteristics such as bottom depth, temperature and salinity. We also measured fork lengths and collected genetic samples from each salmon that was caught. Genetic stock identification revealed that the majority of juvenile salmon were from the Central Valley and the Klamath Basin (91–98%). We constructed generalized logistic‐linear negative binomial hurdle models and chose the best model(s) using Akaike's Information Criterion (AIC) to determine which covariates influenced the salmon presence and, at locations where salmon were present, determined the variables that influenced their abundance. The probability of salmon presence was highest in shallower waters with a high chlorophyll‐a concentration and close to an individual's natal river. Catch abundance was primarily influenced by year, mean fork length and proximity to natal rivers. At the scale of sampling stations, presence and abundance were not related to acoustic indices of zooplankton density. In the weeks to months after ocean entry, California's juvenile Chinook salmon population appears to be primarily constrained to coastal waters near natal river outlets.     

Nutrient efficacy of microalgae as aquafeed additives for the adult black tiger prawn,Penaeus monodon

This study used a small amount of several lyophilized microalgae (5% of dry weight in aquafeed) to feed adult black tiger prawns Penaeus monodon for 4 weeks, aiming to promote prawn health and nutritional level. Apart from slight increases in ash content, chlorophyll and β‐carotene in the microalgae‐added feeds, there was no difference from the commercial diet in their biochemical composition. After 28 days of feeding, prawn body length, body weight, condition index and also total amount of fatty acids and amino acids of the flesh (2nd abdominal segment) were not affected by microalgae additives as compared with the control commercial diet‐fed group (P > 0.05). Prawns fed the microalgae diets, however, had a relatively better survival rate than those fed the commercial control diet, although no statistical significance was detected in any except for the diatom Melosira sp. The elevated survival rate was concomitant with a higher phagocytosis rate and superoxide dismutase (SOD) activity in the immune response analysis, and significantly a higher astaxanthin content detected in the tail muscle of microalgae diet‐fed prawns (5.36–10.78 ng of astaxanthin per gram of muscle DW). These findings demonstrated that low‐inclusion microalgal additives in prawn diets over a short feeding period (4 weeks) can result in healthier adult prawn, and hence could contribute to the development of an optimized feeding strategy for prawn aquaculture close to harvesting.     

Roles of bootstrap resampling,measure of central tendency,and method for calculating thermal units when developing phenology models for pest management

The successful development of phenology models from field studies depends on many factors, some of which are entirely under the control of pest managers. For example, one such factor is the choice of method for calculating thermal units. In this study, we have demonstrated that four methods for calculating thermal units provided for acceptable predictions of one phenological event of one insect species, while another method for calculating thermal units did not. The measure of central tendency (mean or median) that is used to estimate lower developmental temperatures and required thermal summations is another factor that pest managers can control when developing phenology models from field studies. Here, we show that predictions that were made when using phenology models based on median lower developmental temperatures and median required thermal summations were superior to predictions that were made when using phenology models based on mean lower developmental temperatures and mean required thermal summations. The use of bootstrap vs. non-bootstrap estimates of lower developmental temperatures and required thermal summations is yet another factor that pest managers can control when developing phenology models from field studies. In this study, we found that calculating and using bootstrap estimates of lower developmental temperatures and required thermal summations in phenology models did not improve the predictions of one phenological event for one insect species. The implications of these and other findings are discussed.     

Conservation cornerstones: Capitalising on the endeavours of long-term monitoring projects

Ecological monitoring is widely used to measure change through time in ecosystems. The current extinction crisis has resulted in a wealth of monitoring programs focussed on tracking the status of threatened species, and the perceived importance of monitoring has seen it become the cornerstone of many biodiversity conservation programs. However, many monitoring programs fail to produce useful outcomes due to inherent flaws. Here we use a monitoring program from south-eastern Australia as a case study to illustrate the potential of such endeavours. The threatened carnivorous marsupial, the brush-tailed phascogale (Phascogale tapoatafa), has been monitored at various locations between 2000 and 2010. We present strong evidence for a decline in relative abundance during this period, and also describe relationships with environmental variables. These results provide insights likely to be valuable in guiding future management of the species. In the absence of the monitoring program, informed management would not be possible. While early detection of population declines is important, knowledge of the processes driving such declines is required for effective intervention. We argue that monitoring programs will be most effective as a tool for enhanced conservation management if they test specific hypotheses relating to changes in population trajectories. Greater emphasis should be placed on rigorous statistical analysis of monitoring datasets in order to capitalise on the resources devoted to monitoring activities. Many datasets are likely to exist for which careful analysis of results would have benefits for determining management directions.     

The versatile,changing, and advancing roles of fish in sediment toxicity assessment—a review

Purpose  

Sediments serve as integral and dynamic parts of our aquatic systems. Within the last 15 to 20 years, however, the scientific community has begun noticing deterioration of sediment quality at an alarming rate worldwide. Sediments are now harboring hazardous pollutants that can directly influence water quality, thereby creating very stressful conditions for aquatic life. As a consequence, global efforts were initiated in the early 1970s, to find ways to assess sediment quality. Because of their obvious ecological and economic significance, fish have remained a major taxonomic group for appraising the general quality of aquatic systems. However, for sediment risk assessment, fish have lagged behind invertebrates due to their mobility and generally, pelagic lifestyle. To our knowledge, this is the first paper that comprehensively presents and reviews the versatile role of fish in assessing the state of health of aquatic sediments.     

Mineral nutrient and amino acid composition of certain tropical cultivars of soybean

Mineral nutrient and amino acid composition of twelve varieties of soybean grown in an alluvial soil under tropical climate of Assam, India, were studied. On a dry weight basis, Ca and K contents were between 0.35 to 0.46% and 1.66 to 2.11%, respectively, which were relatively high compared with those in temperate varieties. Protein content of the soybeans varied between 40 to 48%. SL‐96 showed the highest amounts of K, Zn, Mn, and B; DS‐37 contained the maximum total amino acids and protein. On the basis of nutrient contents, SL‐96 and DS‐37 are recommended for cultivation in Assam.     

Der einfluss von grundwasser und witterung auf den trockenmasseertrag eines grasmischbestandes (lysimeterergebnis)

In einem Langzeitversuch von 18 Jahren wurde in einer Lysimeterserie mit unterschiedlichen Grundwasserständen die Ertragsleistung von Grasmischbeständen untersucht. In einer multiplen linearen Regressionsanalyse konnte ermittelt werden, daß Grundwassertiefe, Niederschlag, Zusatzwasserangebot, Globalstrahlung, Lufttemperatur und das Sättigungsdefizit Einfluß auf den Ertrag haben. Die Zunahme der Globalstrahlung, des Niederschlages und des Zusatzwassers führen zur Ertragserhöhung. Negativ auf den Ertrag wirken sich zunehmende Grundwassertiefe und Lufttemperatur sowie zunehmendes Sättigungsdefizit aus. Es wurde ein Vergleich zwischen gemessenen und errechneten Erträgen vorgenommen, wobei teils sehr gute Übereinstimmungen vorliegen, in einzelnen Jahren auch größere Abweichungen festzustellen sind.     

THE EFFECT OF PHYSIOLOGICAL STATUS ON DIET SELECTION BY GRAZING EWES

The effect of the physiological status of grazing ewes on diet selection was studied, using ewes with oesophageal fistulae. The diets of dry ewes grazing Phalaris annual grasses and subterranean clover pastures, over a range of availabilities, were compared with those of ewes in various stages of pregnancy and lactation. There were no significant differences at any stage of reproduction in the botanical composition of the diets. However, small differences in diet digestibility, soluble carbohydrate and nitrogen content were found during pregnancy and lactation. These occurred at all levels of availability of pasture. The differences did not appear to have nutritional significance in the particular pasture ecosystems studied because levels of N, soluble carbohydrates and digestibility of the diet were such that selection for survival was unlikely to be necessary.
It is concluded that dry fistulated ewes can be used to obtain samples for assessing diet N and soluble carbohydrate contents for ewes in other physiological states. The use of in vitro digestibility tests of diets of dry ewes to assess diet digestibility for ewes in other physiological states may be subject to error.