Coupling growth and mortality models to detect climate drivers of tropical forest dynamics

Climate models for the coming century predict rainfall reduction in the Amazonian region, including deep changes in water availability for tropical rainforests. Here, we develop an integrated modeling framework in order test the extent to which climate variables related to water regime, temperature and irradiance shape the long-term dynamics of neotropical forests. In a first step, a Bayesian hierarchical model was built to couple tree growth and tree mortality processes into a single modeling framework. Coupling a longitudinal growth model with a punctual mortality model was not an easy task. Past growth, related to the expected growth, was used as an indicator of the individual tree vigor, which is supposed to play a key role in the mortality process. A MCMC approach is used to estimate all the parameters simultaneously. The individual-centered model was explicitly designed to deal with diverse sources of uncertainty, including the complexity of the mortality process itself and the field data, especially historical data for which taxonomic determinations were uncertain. Functional traits are integrated as proxies of the ecological strategies of the trees and permit generalization among all species in the forest community. Data used to parameterize the model were collected at Paracou study site, a tropical rain forest in French Guiana, where 20,408 trees have been yearly censured over 18 years. Climate covariates were finally added as external drivers of the forest dynamics. These drivers are selected in a list of climate variables for which future predictions are available thanks to the IPCC scenario. Amongst climate variables, we highlight the predominant role of water availability in determining interannual variation in the dynamic of neotropical forests. And we stressed the need to include these relationships into forest simulators to test, in silico, the impact of different climate scenarios on the future dynamics of the rainforest. (Texte intégral

Survival, Abundance, and Relative Predation of Wild Rainbow Trout in the Deerfield Reservoir System, South Dakota

Rainbow Trout Oncorhynchus mykiss are routinely stocked in Black Hills streams and reservoirs to enhance angling opportunities for the public, however in most cases, hatchery-reared Rainbow Trout do not successfully recruit to establish natural populations. One exception is the Deerfield Reservoir system, where it is estimated that up to 25% of the Rainbow Trout population consists of naturally produced, wild Rainbow Trout. While recruitment of wild Rainbow Trout to the Deerfield Reservoir fishery does occur, annual stockings of 12,000 hatchery Rainbow Trout have continued. In recent years, adipose fin clips were used to identify hatchery Rainbow Trout stocked into Deerfield Reservoir, however the personnel and time requirements of fin clipping resulted in the termination of fin clips in May 2014. An elimination or reduction of hatchery stockings may be considered in the future management of the Deerfield Reservoir Rainbow Trout population, however a lack of knowledge regarding factors such as predation, movement and emigration patterns, relative abundance, and apparent survival of wild Rainbow Trout has generated a need for additional research in order to help guide future management decisions. In addition, the termination of fin clipping requires the identification and evaluation of new techniques for the classification of wild and hatchery Rainbow Trout in Deerfield Reservoir. Thus the objectives of our research were to 1) investigate the predation on young Rainbow Trout and the diet composition of fishes in Deerfield Reservoir, 2) quantify the relative abundance, growth, and apparent survival of wild Rainbow Trout in the Deerfield Reservoir system, 3) describe the movement patterns and emigration rates of wild Rainbow Trout from tributary streams into Deerfield Reservoir, and 4) evaluate the use of stable isotope analysis and otolith microchemistry for the classification of wild and hatchery Rainbow Trout origins. Juvenile Rainbow Trout were not found in the diets of Rock Bass Ambloplites rupestris, Yellow Perch Perca flavescens, and adult (\u3e200 mm) Rainbow Trout in Deerfield Reservoir and indicated that the risk of predation upon Rainbow Trout is negligible. The diet composition of all species consisted primarily of aquatic invertebrates and dietary overlap did exist among Rainbow Trout, Yellow Perch, and Rock Bass. While diets were similar among species with regard to aquatic invertebrate prey, the degree of diet overlap with Rainbow Trout was generally low (range 0.2- 0.57). We found that the relative abundance of wild Rainbow Trout in tributary streams was greater in South Fork Castle Creek than in Castle Creek. Rainbow Trout movement and emigration from tributaries into Deerfield Reservoir was monitored in both tributaries using 12 mm passive integrated transponder (PIT) tags which showed that within and among stream movement was minimal throughout our study. We tagged 380 Rainbow Trout and in subsequent sampling events recaptured 81 unique fish using backpack electrofishing. Of these 81 fish only 3 were recaptured outside of the 100 m site in which they were tagged, resulting in 96% fidelity to original tagging site. Out of the total 380 tagged Rainbow Trout, another 73 (19%) unique fish were detected by an instream passive PIT tag reader emigrating from tributary streams into Deerfield Reservoir. We constructed a Von Bertalanffy growth model for wild Rainbow Trout in Deerfield Reservoir based on length frequency analysis and found that growth of fish up to age 4 was relatively slow in comparison to other populations, reaching only 210 mm by age 4. Using the growth parameters from the Von Bertalanffy growth model, we estimated survival of wild Rainbow Trout in the Deerfield Reservoir system to be as low as 3% during the first year of life. However, survival increased with each year of life, with relatively high survival (up to 66%) by age 4. In the absence of fin clips, identifying future trends in the wild Rainbow Trout population in Deerfield Reservoir requires the accurate classification of both wild and hatchery origins. Using stable isotope analysis we found that wild Rainbow Trout can be classified with greater than 75% accuracy using pectoral fin tissue, and greater than 85% accuracy using dorsal muscle tissue. We also used otolith microchemistry to identify the natal tributary stream origins of 9 wild Rainbow Trout collected in Deerfield Reservoir. Our results showed that 56% of wild Rainbow Trout in Deerfield Reservoir were classified to Castle Creek, while 44% were classified to South Fork Castle Creek. These results indicate that Castle Creek likely contributes a slightly greater number of wild Rainbow Trout recruits to the Deerfield Reservoir population than South Fork Castle Creek. Overall our results indicate a healthy, sustainable population of wild Rainbow Trout in Deerfield Reservoir. Our analysis of survival, abundance, and emigration data, as well as low risks of predation suggest that management of Deerfield Reservoir for wild Rainbow Trout in the absence of stocking or at reduced stocking rates is likely sustainable. Managing Deerfield Reservoir primarily for wild Rainbow Trout may be viable, however fisheries managers should consider the impact of reduced stockings on angler catch rates. In addition, a reduction or elimination of hatchery stockings would likely have positive impacts on the wild Rainbow Trout population and monitoring changes in the population dynamics of wild Rainbow Trout would be beneficial to the assessment of any stocking changes

Mobile robot for uneven terrain

This paper outlines the details of the development of a mobile robot than can navigate uneven terrain. The robot incorporates a combination of wheels and legs. The legs are based on a parallel-drive 2-R linkage that allows the motors to be located on the robot frame. The legs are driven through servo motors while the wheels are powered through DC motors. A PIC microcontroller is used to control the system, while a novel IR-based communication module allows the user to remotely control the device. In the proof-of-concept prototype, a human operator can control the approximately 6x9x4 inches (15.24x22.86x10.16 cm) and approximately 8 lb. (3.63 kgs) robot (with onboard electronics and control systems) to climb and descend steps. Future versions can be expected to be autonomous and equipped with cameras and ad hoc networking cards for field operations

The two-stage least squares method of estimation

Call number: LD2668 .R4 1968 K5

Reproductive Characteristics of Landlocked Fall Chinook Salmon from Lake Oahe, South Dakota

Lake Oahe, South Dakota, USA, landlocked fall Chinook salmon (Oncorhynchus tshawytscha) reproductive characteristics were examined over a 27 year period, from 1988 to 2015. Mean total lengths of spawning females ranged from 665 mm (1995) to 812 mm (2015) with considerable year-to-year variation. Post-spawn female weights varied, ranging from 2.02 kg (2000) to 5.55 kg (2015), with an overall mean of 3.04 kg. Fecundity peaked at 4,555 eggs per female in 2003, which was just 3 years after a low of 2,011 eggs per female in 2000. Relative fecundity based on female weight was greatest at 1,211 eggs/kg in 2006 and lowest at 631 eggs/kg in 2015, while relative fecundity based on female length peaked in 2003 at 5.64 eggs/mm with the lowest value of 2.93 eggs/mm in 2000. Mean egg size for all years combined was 5.33 eggs/mL of water displaced, but was extremely variable, with the smallest eggs in 1998 and largest in 2015. Survival to the eyed-egg stage of development ranged from 0 to 100% for individual spawns, with an overall mean of 31.2%. Total fecundity was significantly correlated with both length and weight, and linear relationships between fecundity and female length, fecundity and egg size, and female length and egg size were observed. Egg survival was not significantly correlated to female length, weight, fecundity, or egg size. The information from this study will increase the efficiencies of salmon spawning operations, particularly with regard to the duration and intensity of egg collection efforts, as well as provide the foundation to evaluate possible management changes to improve Lake Oahe Chinook salmon reproductive success