Localized Augmentation of Net Precipitation to Shrubs: A Case Study of Stemflow Funneling to Hummocks in a Salinity-Intruded Swamp

The interception of precipitation by plant canopies can alter the amount and spatial distribution of water inputs to ecosystems. We asked whether canopy interception could locally augment water inputs to shrubs by their crowns funneling (freshwater) precipitation as stemflow to their bases, in a wetland where relict overstory trees are dying and persisting shrubs only grow on small hummocks that sit above mesohaline floodwaters. Precipitation, throughfall, and stemflow were measured across 69 events over a 15-months period in a salinity-degraded freshwater swamp in coastal South Carolina, United States. Evaporation of intercepted water from the overstory and shrub canopies reduced net precipitation (stemflow plus throughfall) across the site to 91% of gross (open) precipitation amounts. However, interception by the shrub layer resulted in increased routing of precipitation down the shrub stems to hummocks – this stemflow yielded depths that were over 14 times larger than that of gross precipitation across an area equal to the shrub stem cross-sectional areas. Through dimensional analysis, we inferred that stemflow resulted in local augmentation of net precipitation, with effective precipitation inputs to hummocks equaling 100–135% of gross precipitation. Given that these shrubs (wax myrtle, Morella cerifera) are sensitive to mesohaline salinities, our novel findings prompt the hypothesis that stemflow funneling is an ecophysiologically important mechanism that increases freshwater availability and facilitates shrub persistence in this otherwise stressful environment.

Intracanopy Lighting in Phytocenoses and Photobiological Efficiency of Radiation in Photoculture Conditions

The review is devoted to the study of the internal radiation regime in the canopies cultivated under controlled environmental conditions. The expediency of using canopies as an object of research for evaluating the photobiological efficiency of radiation in light culture conditions is justified. The appropriateness of light measurements in multi-tiered canopies is shown, taking into account the role of leaves of different tiers in the formation of an economically useful crop. The main requirements for light devices for their use in measuring artificial radiation in light culture conditions are considered, and a brief analysis of the existing instrument base for performing these studies is given. A number of examples show the complexity and ambiguity of the internal structure of the light field that is forming within canopies in light culture conditions. Conceptual approaches to the choice of spectral and energy characteristics of artificial irradiation for plant light culture are proposed and justified. The necessity of taking into account the light conditions of leaves of different tiers when choosing the spectral and energy characteristics of light sources for the cultivation of multi-tiered canopies is justified. Techniques, methods, and light sources used for additional intracanopy lighting are analysed. The efficiency of using side illumination of plant canopies and conditions for its implementation are considered. The advantages of the volume distribution of canopies on the most common multi-tiered lighting installations are discussed. Based on the presented material, we consider ways to improve methodological approaches for evaluating the photobiological effectiveness of artificial radiation in light culture conditions for canopies of cultivated plants, taking into account the features of their architectonics and internal radiation regime.

Landsat thermal infrared to detect sub-canopy riparian flooding

<p>Satellite based flood detection can enhance understanding of risk to humans and infrastructures, geomorphic processes, and ecological effects.  Such application of optical satellite imagery has been mostly limited to the detection of water exposed to sky, as plant canopies tend to obstruct water visibility in short electromagnetic wavelengths.  This case study evaluates the utility in multi-temporal thermal infrared observations from Landsat 8 as a basis for detecting sub-canopy fluvial inundation resulting in ambient temperature change.</p><p>We selected three flood events of 2016 and 2019 along sections of the Mississippi, Cedar, and Wapsipinicon Rivers located in Iowa, Minnesota, and Wisconsin, United States.  Classification of sub-canopy water involved logical, threshold-exceedance criteria to capture thermal decline within channel-adjacent vegetated zones.  Open water extent in the floods was mapped based on short-wave infrared thresholds determined parametrically from baseline (non-flooded) observations.  Map accuracy was evaluated using higher-resolution (0.5–5.0 m) synchronic optical imagery.</p><p>Results demonstrate improved ability to detect sub-canopy inundation when thermal infrared change is incorporated: sub-canopy flood class accuracy was comparable to that of open water in previous studies.  The multi-temporal open-water mapping technique yielded high accuracy as compared to similar studies.  This research highlights the utility of Landsat thermal infrared data for monitoring riparian inundation and for validating other remotely sensed and simulated flood maps.</p>

Estimating the quantum requirements for plant growth and related electricity demand for LED lighting systems

Indoor plant production systems with artificial lighting are considered an emerging technology contributing to biomass-based value webs. The viability of this concept greatly relies on the energy requirements (ER, Watt) for lighting. We estimated the ER for plant growth by calculating the conversion efficiency of electricity to light of solid-state light-emitting diodes (LED) and the quantum requirements for plant growth of a fictional plant stand producing 2500 g of dry weight per m2 of ground during 100 days, representing a high productivity benchmark of field crops. The quantum output (µmol s−1 W−1) of eight LEDs of different colours varied between 0.78 for green and 2.54 for deep red. Uncertainty in the H+ demand for ATP synthesis during photosynthesis, the relative portion of photorespiration and the fraction of light intercepted by plant canopies (fabs) were considered in a pessimistic (PA) and optimistic (OA) approach of calculation of ER. Cumulative ER were 606 and 265 kWh m−2 for the PA and OA scenarios. The energy conversion efficiencies in the PA and OA scenarios were 2.07 and 4.72%. Estimates of energy savings by suppressing photorespiration and increasing fabs vary between 24 and 38%. The peak daily ER were 9.44 and 4.14 kWh in the PA and OA scenarios. Results are discussed in the context of the design of lighting in indoor plant production systems and commercial greenhouses where natural fluctuation in solar radiation could be balanced by dimmable LED panels.

Living Particulate Fluxes in Throughfall and Stemflow During a Pollen Event

Pollen shedding can produce rapid, abundant exchanges of nutrient-rich biomass 9 from plant canopies to the surface. When pollen deposits onto understory plants, it can be 10 washed off during storms via throughfall (a drip flux) and stemflow (a flux down plant stems). 11 Pollen deposition may also alter the organismal community on plant surfaces, changing other 12 biological particulates transported by throughfall and stemflow. We report concentrations and 13 fluxes of pollen and other biological particulates (flagellate cells, nematodes, rotifers, mites and 14 hexapodans) in throughfall and stemflow from an understory forb, Eupatorium capillifolium 15 (Lam. dogfennel), during a Pinus palustris (Mill. longleaf pine) pollen shedding event, then 16 compare these results to observations collected when pollen was absent. Pollen flux was 95.6 x 17 106 grains ha-1 season-1 from dogfennel canopies (63% and 37% transported by throughfall and 18 stemflow, respectively), representing 0.1-3.2 g ha-1. Median concentrations in flagellates, 19 nematodes and rotifers for throughfall and stemflow were higher during pollen shedding; 20 however, mites and hexapodan concentrations were similar regardless of pollen presence. This 21 is the first report of flagellate and hexapodan concentrations in canopy drainage waters. 22 Flagellate concentrations were higher than for other organisms—being similar to those 23 reported for streams, 105-107 cells L-1—and hexapodan fluxes were ~50 individuals m-2 per 1 cm 24 of rainfall. These results indicate that throughfall and stemflow can (i) transport ecologically 25 relevant amounts of pollen and organisms from the phyllosphere to the surface, and (ii) that 26 the composition and flux of biological particulates can change markedly during pollen shedding.

Effect of Imidacloprid and Acephate for Tobacco Thrips (Thysonaptera: Thripidae) Management on Flumioxazin Injured Peanut

Experiments were conducted in 2016 and 2017 in Stoneville, MS and Starkville, MS to determine the impact of different insecticide management options for thrips on herbicide injured peanut. Insecticide treatments included imidacloprid in-furrow at-planting, one or two foliar applications of acephate, and an untreated control with and without an application of flumioxazin. In Stoneville, herbicide applications were made immediately following planting, and in Starkville, applications were made as plants were emerging to maximize herbicide injury. The Stoneville experiment also had an additional factor in which plots were flooded or not flooded to simulate a heavy rainfall in order to maximize herbicide injury and also to give added stress from saturated soils. Thrips counts, thrips injury ratings, plant vigor ratings, plant biomass, width between plant canopies, and yield were recorded. Few interactions were observed, but temporary flooding, herbicide injury, and thrips injury affected peanut growth as measured by biomass and canopy. Imidacloprid was the most consistent insecticide treatment for reducing thrips numbers and injury, but acephate provided some protection. Temporary flooding during the seedling stage, flumioxazin injury, and thrips injury all reduced peanut pod yield. Based on these results, every attempt should be made to minimize early season stress in peanuts including the use of an effective in-furrow insecticide.

Shrub canopy interception of diaspores dispersed by wind

Interception by plant canopies during wind dispersal can affect the final destination of diaspores. However, how the interaction of wind speed, canopy type and diaspore attributes affects interception of diaspores by the plant canopy has rarely been studied. We investigated canopy interception for 29 species with different diaspore attributes, six canopy types and six wind speeds in controlled experiments in a wind tunnel. Shrub canopy interception of diaspores were controlled by wind speed and diaspore attributes, but the latter had a greater influence on canopy interception than the former. At low wind speed, diaspore wing loading had a large influence on canopy interception, whereas at high wind speed, diaspore projection area had a large influence. The chance of canopy interception at a particular wind speed was additionally affected by the type of canopy. This study increases our knowledge of the dispersal process, corrects the previous understanding of diaspore dispersal potential and improves the theoretical basis for predicting spatial pattern and dynamics of plant populations.