Model-based analysis of the influence of ecological processes on forest point pattern formation—A case study

Many different spatio-temporal individual-based models (IBM) for forests have been developed for studying the development of trees in space and time. Such models typically depend on various numerical parameters that represent the ecological processes of growth (G), inter-plant competition (C) and birth-and-death (B&D; also called regeneration and mortality). Until now little work has been done to systematically trace the influence of these processes and their model parameters on the spatial structure of forest ecosystems.This paper attempts to fill this gap by addressing an important aspect of forest structure, spatial variability, characterised by the mark variogram as a summary characteristic. The model used was inspired by components of various well-established IBMs including a shot-noise competition field. Time series data from monospecies forests in three different countries of the northern hemisphere provided ecological reference scenarios. Though a case study, the paper's methodology is rather general and can be applied to any model and forest ecosystem.Methods of sensitivity analysis revealed that only a small number of model parameters is crucial for forming spatial variability. Particularly important is the range of competition between trees; with increasing range the variability increases. Growth processes have considerable importance particularly with short observation periods and in young forests, whereas mortality processes become more influential in the long-term. Naturally, these statements depend upon the initial structure and on the length of the observation period.     

Development and modelling of realistic retrofitted Nature-based Solution scenarios to reduce flood occurrence at the catchment scale

Decentralized Nature-based Solutions such as Urban Green Infrastructures (UGI) are increasingly promoted to reduce flooding in urban areas. Many studies have shown the effectiveness of flood control of UGI at a plot or neighbourhood level. Modelling approaches that extrapolate their flood reducing impact to larger catchment scales are often based on a simplistic assumption of different percentages of UGI implementation. Additionally, such approaches typically do not consider the suitable space for UGI and potential implementation constraints. This study proposes a scenario development and modelling approach for a more realistic upscaling of UGI based on empirical insights from a representative neighbourhood. The results from this study, conducted in the metropolitan area of Costa Rica, show that upscaling the full potential for UGI could significantly reduce surface runoff, peak flows, and flood volumes. In particular, the permeable pavement has the highest potential for flood reducing in public space while cisterns perform best at the property level. These results can guide the formation of policies that promote UGI.Supplementary InformationThe online version of this article (10.1007/s13280-020-01493-8) contains supplementary material, which is available to authorized users.     

Agricultural land use efficiency and food crop production in Ghana

Despite the low productivity of the extensive agriculture system, Ghana recorded the largest reduction of undernourishment in the past two decades. We used biophysical analysis to determine the efficiency and potentials of the extensive system and its future sustainability. The results indicate that food production in Ghana has increased steadily over the past two decades and correlated highly with cropped area and population (R ² < 0.85 and 0.82), but not with fertilizer (R ² = 0.06). Sufficient food production could be sustained in the short term. In the longer term, however, the food situation in Ghana appears precarious if population growth continues while land remains the same.     

Fish school density and volume

All the fish in a school occupy a volume estimated as N·BL³, where N is the number of fish and BL is their mean body length. We present extensive data from our experiments on cruising schools of saithe (Pollachius virens), herring (Clupea harengus) and cod (Gadus morhua) to validate this formula. Two methods of calculating the volumes of schools are described. One method is aggregative and depends on measuring the envelope of free space around a schooling fish, whereas the other is based on the dimensions of the school as a whole. The whole-school method is more reliable since it includes lacunae between the sub-units which exist in schools. For this method, we derive a computation which eliminates bias from outliers. The most realistic theoretical aggregative packing model predicts a volume per fish of 0.6 BL³. In saithe, the envelope of free space is approximately an ellipsoid, which, although it becomes more compressed at higher swimming speeds, yields a volume close to 0.7 BL³. From the whole-school method we calculate average volumes of 1.4 BL³ for saithe and 0.7 BL³ for herring. Increase in swimming speed produces more compact schools in saithe, but changes in arousal level can generate equally large differences. Changes in volume were not adequately explained by changes in nearest neighbour distance, giving support to the whole-school method.     

The effect of perceived female parasite load on post-copulatory male choice in a sex-role-reversed pipefish

The last several decades of research in behavioral ecology have resulted in a deeper appreciation of post-mating processes and sexual conflict in sexual selection. One of the most controversial aspects of sexual selection is cryptic mate choice. Here, we take advantage of male pregnancy in a sex-role-reversed pipefish (Syngnathus typhle) to quantify cryptic choice based on perceived parasite load and other sources of variance in female fitness. Studies have shown that S. typhle males preferentially mate with females with lower parasite loads and that a male’s perception of female parasite load can be altered by tattooing females. We manipulated the apparent parasite load of females in controlled mating experiments to test the hypothesis that post-copulatory sexual selection is dependent on a male’s perception of female parasite load in pipefish. Our results provided no evidence for cryptic male choice based on perceived female parasite load. However, we found evidence that eggs from larger females were more likely to result in viable offspring than eggs from smaller females and that the first female to mate with a male transferred more eggs per copulation on average. Overall, our results show that potential for post-copulatory sexual selection does exist in pipefish, but the male’s perception of female parasite load does not play a major role in this process.     

Estimating the Impact of Temperature and Rainfall on Malaria Incidence in Ghana from 2012 to 2017

Environmental Modeling & Assessment - Malaria has a significant impact on the lives of many in Ghana. It is one of the key causes of mortality and morbidity, resulting in 32.5% of outpatient...