IDENTIFICATION OF CHANGES IN STREAMFLOW CHARACTERISTICS1

ABSTRACT: A set of procedures for identifying changes in selected streamflow characteristics at sites having long‐term continuous streamflow records is illustrated by using streamflow data from the Waccamaw River at Freeland, North Carolina for the 55‐year period of 1940–1994. Data were evaluated and compared to streamflow in the adjacent Lumber River Basin to determine if changes in streamflow characteristics in the Waccamaw River were localized and possibly the result of some human activity, or consistent with regional variations. Following 1963, droughts in the Waccamaw Basin seem to have been less severe than in the Lumber Basin, and the annual one‐, seven‐, and 30‐day low flows exhibited a slightly increasing trend in the Waccamaw River. Mean daily flows in the Waccamaw River at the 90 percent exceedance level (low flows) during 1985–194, a relatively dry period, were very nearly equal to flows at the same exceedance level for 1970–1979, which represents the 10‐year period between 1940 and 1994 with the highest flows. Prior to the 1980s, flows per unit drainage area in the Waccamaw Basin were generally less than those in the Lumber Basin, but after 1980, the opposite was true. The ratio of base flow to runoff in the Waccamaw River may have changed relative to that in the Lumber River in the late 1970s. There was greater variability in Waccamaw River streamflow than in Lumber River flow, and flow variability in the Waccamaw River may have increased slightly during 1985–1994.     

Modeling of NO x Emissions from Oil Refinery Furnaces

The current paper investigates the possibility of establishing an empirically based model for predicting the emission rate of nitrogen oxides (NO _x ) from oil refinery furnaces, in order to continually track emissions with respect to environmental licence limits. Model input data were collected by direct stack monitoring using an electrochemical cell NO _x analyser, as well as a range of telemetry sensors to obtain refinery process parameters. Principal Component Analysis (PCA), in conjunction with Partial Least Squares (PLS) regression was then used to build a series of models able to predict NO _x emissions from the furnaces. The models produced were proven to be robust, with a relatively high accuracy, and are able to predict NO _x levels over the range of operating conditions which were sampled. It was found that due to structural/operational variations a separate model is usually required for each furnace. The models can be integrated with the refinery operating system to predict NO _x emission rates on a continuous basis. Two models representing structurally different furnaces are considered in this paper. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reduced planktotrophy in larvae of <Emphasis Type="Italic">Clypeaster</Emphasis><Emphasis Type="Italic">rosaceus</Emphasis> (Echinodermata,Echiniodea)

Phylogenetic analyses have demonstrated that nonfeeding larvae have evolved from feeding larvae many times among marine invertebrates. In light of this observation, it is surprising that an intermediate strategy, a larva that can feed but is provisioned with enough energy to metamorphose without acquiring exogenous food (i.e., facultative planktotrophy), is rare. A hypothesis for the lack of facultative planktotrophic species among marine invertebrates is that the transition from feeding to nonfeeding is rapid due to this intermediate stage being evolutionarily unstable. Evidence that would support this hypothesis is if species with facultative planktotrophy have reduced food assimilation when compared with obligate planktotrophs. We studied a species with facultative planktotrophic larvae, Clypeaster rosaceus, that is very near the boundary between facultative and obligatory planktotrophy, to answer two questions: (1) does feeding during the larval stage result in energy gains in larval or juvenile stages and (2) if not, are larvae capable of assimilating exogenous food at all. Our measurements of energetics in larval and juvenile stages show that C. rosaceus larvae accumulate very little if any energy when fed, but stable isotope data indicate that larvae are able to assimilate some food. Our results are consistent with similar studies on facultative planktotrophic larvae suggesting poor food assimilation and rapid loss of larval feeding after a population evolves the ability to reach metamorphosis without feeding (lecithotrophy).     

Experimental Assessment of Atmospheric Ammonia Dispersion and Short Range Dry Deposition in a Maize Canopy

In order to study the effect of thevegetation structure on atmospheric ammonia(NH₃) dispersion and deposition, anexperiment was set up near Paris, in July 1997.Between 12 and 162 m downwind of a 200 m line-source releasing 600 to 1200 g NH₃hr^-1placed at the top of a maize canopy, NH₃concentration was measured, within and above thecanopy, with a set of 30 active, acid-coateddenuders over periods of 2 to 3 hr. Eight datasets were collected over a one-month period.NH₃ concentration decreased sharply withdistance to the source, from up to800 g NH₃ m^-3 at 12 m, to lessthan 10 g NH₃ m^-3 at 162 m andshowed strong vertical gradients. Within thecanopy, the concentration scaled using thefriction velocity, the canopy height, and thesource strength, exhibited a universal power lawrelationship as a function of the normaliseddownwind distance from the source. A mass balancemethod and a resistance model approach were usedas independent estimates of the cumulateddeposition at 162 m downwind from the source,which range between 1 and 29% of the emittedNH₃. Both methods agreed approximately inmagnitude. A sensitivity analysis showed that thecuticular uptake and the compensation point aremajor parameters that needs to be bettercharacterised under high NH₃ concentrationif one wants to improve NH₃ short-rangedeposition modelling.     

Networking emergency teams in Jerusalem

With the recent upsurge in terrorism, more and more attention is being directed at examining the effectiveness and efficiency of emergency teams. These teams tend to focus on their areas of expertise without necessarily communicating, cooperating or coordinating their operations. Research suggests that improved interpersonal communication and coordination enhances the overall work of each emergency team, and that their combined effort is far in excess of the sum of their individual endeavours. This paper outlines attempts made in Jerusalem to improve the performance of emergency teams and to help the helpers by holding training workshops, setting up a forum of co‐workers and encouraging dialogue among various emergency teams in the city. A planned intervention programme was designed to enable informal networking between team leaders. The programme had an impact on team workers and resulted in a more coordinated and effective service delivery during emergencies.     

Experimental manipulation of seed shadows of an Afrotropical tree determines drivers of recruitment

The loss of animals in tropical forests may alter seed dispersal patterns and reduce seedling recruitment of tree species, but direct experimental evidence is scarce. We manipulated dispersal patterns of Manilkara mabokeensis, a monkey-dispersed tree, to assess the extent to which spatial distributions of seeds drive seedling recruitment. Based on the natural seed shadow, we created seed distributions with seeds deposited under the canopy ("no dispersal"), with declining density from the tree ("natural dispersal"), and at uniform densities ("good dispersal"). These distributions mimicked dispersal patterns that could occur with the extirpation of monkeys, low levels of hunting, and high rates of seed dispersal. We monitored seedling emergence and survival for 18 months and recorded the number of leaves and damage to leaves. "Good dispersal" increased seedling survival by 26%, and "no dispersal" decreased survival by 78%, relative to "natural dispersal." Using a mixed-effects survival model, we decoupled the distance and density components of the seed shadow: seedling survival depended on the seed density, but not on the distance from the tree. Although community seedling diversity tended to decrease with longer dispersal distances, we found no conclusive evidence that patterns of seed dispersal influence the diversity of the seedling community. Local seed dispersal does affect seedling recruitment and survival, with better dispersal resulting in higher seedling recruitment; hence the loss of dispersal services that comes with the reduction or extirpation of seed dispersers will decrease regeneration of some tree species.     

Soil microbes drive the classic plant diversity-productivity pattern

Ecosystem productivity commonly increases asymptotically with plant species diversity, and determining the mechanisms responsible for this well-known pattern is essential to predict potential changes in ecosystem productivity with ongoing species loss. Previous studies attributed the asymptotic diversity-productivity pattern to plant competition and differential resource use (e.g., niche complementarity). Using an analytical model and a series of experiments, we demonstrate theoretically and empirically that host-specific soil microbes can be major determinants of the diversity-productivity relationship in grasslands. In the presence of soil microbes, plant disease decreased with increasing diversity, and productivity increased nearly 500%, primarily because of the strong effect of density-dependent disease on productivity at low diversity. Correspondingly, disease was higher in plants grown in conspecific-trained soils than heterospecific-trained soils (demonstrating host-specificity), and productivity increased and host-specific disease decreased with increasing community diversity, suggesting that disease was the primary cause of reduced productivity in species-poor treatments. In sterilized, microbe-free soils, the increase in productivity with increasing plant species number was markedly lower than the increase measured in the presence of soil microbes, suggesting that niche complementarity was a weaker determinant of the diversity-productivity relationship. Our results demonstrate that soil microbes play an integral role as determinants of the diversity-productivity relationship.     

Testing for relationships between individual crab behavior and metabolic rate across ecological contexts

Two classes of explanations for covariation between activity level and metabolic rate among conspecifics have been proposed. First, individual-level variation in activity exhibited during the measurement of metabolic rate should covary with routine metabolic rate because movement increases respiration (a methodological relationship). Second, energetic-based hypotheses posit relationships between individual activity measured under more natural conditions and baseline measures of metabolic rate, among other behavioral, physiological, and life-history traits (functional relationships). Here, we examined these potential relationships between individual behavior and metabolic rate in the mud crab (Panopeus herbstii). Specifically, we tested for (1) an effect of crab activity in metabolic chambers (activity_chamber) on routine metabolic rate (RMR), and (2) an effect of crab activity in mesocosms that mimicked field conditions (activity_mesocosm) on standard metabolic rate (SMR). To test for context dependence, we assessed both activity-metabolic rate relationships in the absence and presence of predation threat from toadfish (Opsanus tau) in the form of waterborne chemical cues. Individual variation in activity_mesocosm and RMR was repeatable over time. In support of a methodological relationship, individual differences in RMR were partially explained by crab activity_chamber. After accounting for this methodological relationship, individual SMR was inversely related to activity_mesocosm, supporting an allocation model that predicts behavior and baseline metabolic rate compete for finite energy reserves. We found no evidence of context dependence in either activity-metabolic rate relationship. Thus, our study emphasizes the importance of considering methodological artifacts in elucidating functional relationships between individual behavior and energetics.     

Exploring future agricultural development and biodiversity in Uganda,Rwanda and Burundi: a spatially explicit scenario-based assessment

Regional Environmental Change - Competition for land is increasing as a consequence of the growing demands for food and other commodities and the need to conserve biodiversity and ecosystem...     

Ecological risk as a tool for evaluating the effects of offshore wind farm construction in the North Sea

Offshore wind power generation represents a chance to supply energy in a more sustainable way; however, the ecological risks associated with the construction and operation of offshore wind farms are still largely unknown. This paper uses the concept of ecological risk for analysing ecological changes during construction of offshore wind farms. “Ecological risk” is defined as the potentially reduced ability of providing ecosystem services. The ERSEM ecosystem model allows assessing ecological risk based on a number of selected variables (integrity indicators) and under the assumption that increased suspended matter concentration during construction of wind farms affects ecosystem functioning. We conclude that ecological risk is adequate to describe the effects of wind farm constructions, although the computation procedure still needs to be refined and the choice of indicators further optimised. In this context, the choice of indicators available in modelling as well as in monitoring time-series may offer the way forward.