Modeling foundation species in food webs

Foundation species are basal species that play an important role in determining community composition by physically structuring ecosystems and modulating ecosystem processes. Foundation species largely operate via non-trophic interactions, presenting a challenge to incorporating them into food web models. Here, we used non-linear, bioenergetic predator-prey models to explore the role of foundation species and their non-trophic effects. We explored four types of models in which the foundation species reduced the metabolic rates of species in a specific trophic position. We examined the outcomes of each of these models for six metabolic rate “treatments” in which the foundation species altered the metabolic rates of associated species by one-tenth to ten times their allometric baseline metabolic rates. For each model simulation, we looked at how foundation species influenced food web structure during community assembly and the subsequent change in food web structure when the foundation species was removed. When a foundation species lowered the metabolic rate of only basal species, the resultant webs were complex, species-rich, and robust to foundation species removals. On the other hand, when a foundation species lowered the metabolic rate of only consumer species, all species, or no species, the resultant webs were species-poor and the subsequent removal of the foundation species resulted in the further loss of species and complexity. This suggests that in nature we should look for foundation species to predominantly facilitate basal species.Organismic and Evolutionary Biolog

The Effect of Two Planting Dates and Methods on Snap Bean (Phaseolus Vulgaris) Production in a Tunnel House

The study was conducted to evaluate the impact of two planting dates and methods on snap bean yields in a tunnel house. The main plots included planting dates March 17 and 31, 2016 for first and second plantings. The sub-plots consisted of planting Method 1 where one seed per hill was planted every 4” apart, and planting Method 2 where three seeds per hill were planted every 12” apart; each treatment combination was replicated four times. The results of the study showed that it took 55 days for the snap beans to be ready for harvest for both planting dates. Also, there were no significant differences in yields between planting dates, and there were no significant differences in yields between planting methods. This notwithstanding, it may appear that Method 2 would better for weed control because the plants will be well spaced compared to Method 1. Keywords: Tunnel House, Snap bean Planting Dates, Snap bean Planting Methods, Snap bean Yield

The Evaluation of Two Different Harvesting \u27Topbunch\u27 and \u27Hi-Crop\u27 Collards (Brassica Oleracea (L)) Leaves from Plants Grown in a Wiregrass Tunnel House

A study was conducted to determine if a 100% or 50% harvest intensity of ‘Topbunch’ collards leaves could be a recommended practice for Tunnel House producers. The experiment was conducted as a split-plot design with harvest dates as main plots, and harvesting intensity of 100% or 50% of leaves as sub-plots. All treatments were replicated three times, drip irrigated, and fertilized according to soil test recommendations. The results showed significant interactions between harvest methods and dates for number and weight of leaves harvested. There were also significant differences for the weight of leaves harvested and numbers. The leaf recovery rates were greater for plants that had 50% of their leaves harvested compared to those which had 100% of their leaves harvested. This higher recovery rate for the former suggests that the harvest interval could be reduced in the future from 21 to 15 or 18 days

Air and Soil Temperature Readings, Growing Degree Days, and Chilling Hours Recorded in Two Wiregrass Tunnel Houses Located in East Central Alabama

The study examined air and soil temperature readings, growing degree days, and chilling hours recorded in two Wiregrass tunnel houses during the 2018-2019 season. The monthly average ambient temperature, was 15OF warmer inside the Tunnel House (75/60OF) during the Cool/Cold months, and 17OF warmer inside (90/73OF) during the Warm/Hot seasons of 2018 and 2019. Growing Degree Days heat unit (HU) accumulations were higher inside than outside 4,154 vs. 3,153 HU for the Cool/Cold months and 5,134 vs. 4,800 HU for the Warm/Hot months. Chilling hour accumulations were lower inside the tunnel houses than outside the tunnel houses, 601vs. 671 hr. Utilizing the temperature data from this study, a planting guide consisting of a Cool/Cold (September-February) season and Warm/Hot (March-August) season was developed for a list of crops which producers could plant. The results of this study provides information for growers to better plan their crop choices and planting schedules

Yield Response of ‘Whatley-Loretan’ Sweetpotato (Ipomoea Batatas (L.)) Transplanted in Single And Double Row at Different Dates in A Wiregrass Tunnel House

A split-plot study was conducted to evaluate the yield response of ‘Whatley-Loretan’ sweetpotato when planted in single and double rows at four planting dates (March, April, May, and June) in a Wiregrass Tunnel House located at S&B Farm in Eufaula, Alabama. The main plots consisted of planting dates, sub-plots single, and double rows, with each treatment combination, replicated three times. The results showed a significant linear and quadratic effect for US#1 grade of sweetpotato and total marketable yields. Yields were highest at the first and second planting dates and declined at the two later planting dates. Single vs. double row planting significantly affected canner grade of sweetpotatoes, while the other grades were unaffected

The Effect of Two Different Harvesting Methods on the Yield of \u27Topbunch\u27 and \u27Hi-Crop\u27 Collards (Brassica Oleracea (L)) When Grown in a Wiregrass Tunnel House

A study was conducted to determine if 100% or 50% harvesting of collard leaves was a suitable recommendation for Tunnel House producers. The experiment was conducted as a split-split plot design with varieties as the main plots, harvesting 100% or 50% of leaves as the sub-plots, and days after transplanting as the subplots. All treatments were replicated three times, drip irrigated, and fertilized according to soil test recommendations. The results showed significant interactions between varieties and method of harvest, for leaf numbers and weight. Conversely, the varieties showed significant differences for yield but not leaf numbers. Both varieties showed significant increases in leaf numbers and yield at each harvest period when 50% of the leaves were harvested, instead of 100%. This approach led to higher leaf recovery rates suggesting that a 50% leaf harvest would result in higher yields, and reduce the harvest intervals from the present 21 to 12 or 18 days

The Effect of A Fifty Percent Leaf Harvest From Three Varieties of Collards (Brassica Oleracea(L)/Cultivar Group Acephala) Cropped at Selected Intervals When Grown in A Wiregrass Tunnel House

A study was conducted to determine the effects of a 50% leaf harvest from ‘Heirloom’, ‘Georgia’, and ‘Hi-Crop Hybrid’ collards on yield, when leaves were removed at 18-, 21-, and 25- day intervals, over four harvest periods of 102, 127, 152, and 177 days after transplanting in a Wiregrass Tunnel House. The experimental design used was a split-split plot with three replications, where harvest periods were main plots, cropping intervals (3) were sub-plots, and varieties were sub-sub-plots. Yield data (lbs./acre) showed significant interactions between harvest periods x cropping intervals for leaf numbers and yield, harvest periods x varieties, and cropping intervals x varieties. The 18-day cropping interval had the highest yields over all harvest periods; while varieties responded differently for each harvest period, and cropping intervals. ‘Hi-Crop Hybrid’ had the highest yield over all harvest periods and cropping intervals, followed by ‘Georgia ‘and ‘Heirloom.

Predicting coastal cliff erosion using a Bayesian probabilistic model

This paper is not subject to U.S. copyright. The definitive version was published in Marine Geology 278 (2010): 140-149, doi:10.1016/j.margeo.2010.10.001.Regional coastal cliff retreat is difficult to model due to the episodic nature of failures and the along-shore variability of retreat events. There is a growing demand, however, for predictive models that can be used to forecast areas vulnerable to coastal erosion hazards. Increasingly, probabilistic models are being employed that require data sets of high temporal density to define the joint probability density function that relates forcing variables (e.g. wave conditions) and initial conditions (e.g. cliff geometry) to erosion events. In this study we use a multi-parameter Bayesian network to investigate correlations between key variables that control and influence variations in cliff retreat processes. The network uses Bayesian statistical methods to estimate event probabilities using existing observations. Within this framework, we forecast the spatial distribution of cliff retreat along two stretches of cliffed coast in Southern California. The input parameters are the height and slope of the cliff, a descriptor of material strength based on the dominant cliff-forming lithology, and the long-term cliff erosion rate that represents prior behavior. The model is forced using predicted wave impact hours. Results demonstrate that the Bayesian approach is well-suited to the forward modeling of coastal cliff retreat, with the correct outcomes forecast in 70–90% of the modeled transects. The model also performs well in identifying specific locations of high cliff erosion, thus providing a foundation for hazard mapping. This approach can be employed to predict cliff erosion at time-scales ranging from storm events to the impacts of sea-level rise at the century-scale

Footprint evidence of early hominin locomotor diversity at Laetoli, Tanzania

Bipedal trackways discovered in 1978 at Laetoli site G, Tanzania and dated to 3.66 million years ago are widely accepted as the oldest unequivocal evidence of obligate bipedalism in the human lineage1-3. Another trackway discovered two years earlier at nearby site A was partially excavated and attributed to a hominin, but curious affinities with bears (ursids) marginalized its importance to the paleoanthropological community, and the location of these footprints fell into obscurity3-5. In 2019, we located, excavated and cleaned the site A trackway, producing a digital archive using 3D photogrammetry and laser scanning. Here we compare the footprints at this site with those of American black bears, chimpanzees and humans, and we show that they resemble those of hominins more than ursids. In fact, the narrow step width corroborates the original interpretation of a small, cross-stepping bipedal hominin. However, the inferred foot proportions, gait parameters and 3D morphologies of footprints at site A are readily distinguished from those at site G, indicating that a minimum of two hominin taxa with different feet and gaits coexisted at Laetoli