Studies of lignin degradation in mound material of the termite Nasutitermes exitiosus

Soil Research ◽  
1992 ◽  
Vol 30 (2) ◽  
pp. 189 ◽  
Author(s):  
LJ Cookson
Keyword(s):  
Populus Tremuloides ◽  
Lignin Degradation ◽  
Co2 Evolution ◽  
Adjacent Soil ◽  
Moisture Conditions

Lignin degradation in the mound material of the enteric lignin degrading termite Nasutitermes exitiosus (Hill) was studied under normal and wet moisture conditions during incubation with C-14-(lignin)-Populus tremuloides Michx. There was negligible 14(CO2) evolution from mound material incubated for five weeks. However, adjacent soil when wet produced a 6.8% degradation of the 14C-(lignin)-lignocellulose.

Aspen and pine leaf litter decomposition in laboratory microcosms. I. Linear versus exponential models of decay

1988 ◽  
Vol 66 (10) ◽  
pp. 1960-1965 ◽  
Author(s):  
Barry R. Taylor ◽  
Dennis Parkinson
Keyword(s):  
Mass Loss ◽  
Leaf Litter ◽  
Populus Tremuloides ◽  
Pinus Contorta ◽  
Exponential Model ◽  
Plant Litter ◽  
Adverse Conditions ◽  
Negative Exponential Model ◽  
Negative Exponential ◽  
Moisture Conditions

Leaf litter of trembling aspen (Populus tremuloides Michx.) and lodgepole–jack pine (Pinus contorta Loud, × P. banksiana Lamb.) was decomposed in laboratory microcosms at 2, 10, 18, or 26 °C and three watering rates (15, 30, or 60 mL∙week−1) for 16 weeks. Aspen litter lost 5.0–37.3% of original mass, and pine litter lost 7.8–14.9%. Decay curves fit a sample linear model equally as well as the negative exponential model regardless of temperature or moisture conditions or species of litter. A general explanation of circumstances promoting apparently linear mass loss from decaying plant litter is derived from these data, a survey of the literature, and the assumption that all decay curves are ultimately curvilinear. Mass loss rates are expected to appear linear from slowly decaying substrates such as bole wood or when decay of rapidly decomposing substrates is not followed past the inflection point of the curve. Climatic variables that favour decomposer activity are hypothesized to increase the concavity of decay curves, while adverse conditions do the opposite.

Root connections can trigger physiological responses to defoliation in nondefoliated aspen suckers

Botany ◽  
2011 ◽  
Vol 89 (11) ◽  
pp. 753-761 ◽  
Author(s):  
Matthieu Baret ◽  
Annie DesRochers
Keyword(s):  
Stomatal Conductance ◽  
Populus Tremuloides ◽  
Forest Dynamics ◽  
Physiological Responses ◽  
Stand Dynamics ◽  
High Humidity ◽  
High Moisture ◽  
Maximum Capacity ◽  
Root Suckering ◽  
Moisture Conditions

In species such as aspen ( Populus tremuloides Michx.), trees are interconnected through their root system owing to their regeneration mode by root suckering. These root connections challenge classic notions of forest dynamics that consider trees as individuals competing for resources, because root connections allow trees to share water, minerals, and carbohydrates. The purpose of this study was to demonstrate that trees can directly influence the physiology of other nearby trees through root connections. In the summers of 2007 and 2008, pairs of aspen suckers (i.e., two suckers connected by a parental root) were selected and divided into three height classes and compared with each other (dominant, codominant, suppressed). Suckers distally positioned on the parental root were manually defoliated, and the effects of defoliation on photosynthesis, stomatal conductance, and specific leaf area (SLA) were measured on connected but nondefoliated suckers. Results showed that defoliation caused physiological responses in the interconnected trees in summer 2007, which was drier than summer 2008. Defoliation of a connected sucker had a greater effect on suppressed suckers, for which mean photosynthesis rate increased by 17% compared with that of controls. The effect was less important for codominant (14% increase) and dominant (12%) trees. SLA of suppressed suckers also increased, while the increase in SLA values was smaller for codominant and dominant suckers. In summer 2008, no defoliation effect was observed, probably owing to high moisture conditions that resulted in much higher stomatal conductance values compared with those in 2007 (+55%). Under high humidity conditions, leaf specific hydraulic conductance does not constrain stomatal conductance, so the rate of CO2 assimilation was probably at its maximum capacity. This study demonstrated that trees could physiologically interact through root connections, and these interactions should thus be considered in studies of stand dynamics.

Modeling snowpack and soil temperature and moisture conditions in a jack pine, black spruce and aspen forest stand in central Saskatchewan (BOREAS SSA)

2006 ◽  
Vol 86 (Special Issue) ◽  
pp. 203-217 ◽  
Author(s):  
Vincent Balland, Jagtar Bhatti ◽  
Ruth Errington, Mark Castonguay ◽  
Paul A. Arp
Keyword(s):  
Soil Moisture ◽  
Soil Temperature ◽  
Populus Tremuloides ◽  
Forest Floor ◽  
Black Spruce ◽  
Jack Pine ◽  
Soil Freezing ◽  
Moisture Retention ◽  
Frost Penetration ◽  
Moisture Conditions

Impacts of climate change on above- and below-ground heat and moisture conditions were modeled so that other impacts on, e.g., local carbon (C) and C-based pools for nutrients and pollutants such as Hg can be predicted reliably. This paper shows how the 199–-2003 data for the jack pine (jp; Pinus banksiana Lamb.), black spruce (bs; Picea mariana) and aspen (ta; Populus tremuloides) sites of the Southern Study Area of the BOREAS project were used to estimate some of the hydrothermal soil responses at these locations to daily variations in precipitation and air temperature. This was done by initializing and calibrating a forest hydrology model that has the capacity to simulate flow and retention of moisture and heat, as modified by canopy closure, ground cover, forest-floor depth, and soil composition. The calculations and data revealed strong but predictable site-specific differences in soil temperature and frost penetration (jp: 1–2 m > ta: 0.5–1 m > bs: 0–0.5 m), in soil moisture freezing (ta < bs < jp), and in moisture retention (jp < ta < bs). Apart from daily weather, these differences depended on soil texture (loamy/sandy texture impeded/encouraged soil freezing, respectively), and on the thermal insulation and moisture retention of the combined forest floor, moss and lichens layers (ta < jp < bs). Key words: Jack pine, aspen, black spruce, soil moisture, soil temperature, frost penetration, snowpack, boreal conditions

Aging of polymer composite materials under loading. (See Beginning in #10-2020)

2020 ◽  
pp. 2-12
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Polymer Composite ◽  
Polymer Composite Materials ◽  
Cyclic Loads ◽  
Reinforced Plastics ◽  
Water Exposure ◽  
Laboratory Conditions ◽  
Bending Loads ◽  
Moisture Conditions

A study review of aging polymer composite materials (PCM) under different heat-moisture conditions or water exposure with the sequential or parallel influence of static or cyclic loads in laboratory conditions is presented. The influence of tension and bending loads is compared. Conditions of the different load influence on parameters of carbon-reinforced plastics and glass-reinforced plastics are discussed. Equipment and units for climatic tests of PCM under loading are described. Simulation examples of indices of mechanical properties of PCM under the influence of environment and loads are shown.

Aging of polymer composite materials under loading

2020 ◽  
pp. 7-18
Keyword(s):  
Mechanical Properties ◽  
Composite Materials ◽  
Polymer Composite ◽  
Polymer Composite Materials ◽  
Cyclic Loads ◽  
Reinforced Plastics ◽  
Water Exposure ◽  
Laboratory Conditions ◽  
Bending Loads ◽  
Moisture Conditions

A study review of aging polymer composite materials (PCM) under different heat-moisture conditions or water exposure with the sequential or parallel influence of static or cyclic loads in laboratory conditions is presented. The influence of tension and bending loads is compared. Conditions of the different load influence on parameters of carbon-reinforced plastics and glass-reinforced plastics are discussed. Equipment and units for climatic tests of PCM under loading are described. Simulation examples of indices of mechanical properties of PCM under the influence of environment and loads are shown.

Evaluation of Presswheels and Seed Coverers for Direct Seeding of Brassica

HortScience ◽  
1997 ◽  
Vol 32 (4) ◽  
pp. 599E-600
Author(s):  
Regina P. Bracy ◽  
Richard L. Parish
Keyword(s):  
Soil Moisture ◽  
Sandy Loam ◽  
Visual Observation ◽  
Mustard Seed ◽  
High Soil Moisture ◽  
Loam Soil ◽  
Direct Seeded ◽  
Plant Emergence ◽  
Moisture Conditions ◽  
Determine Effect

Improved stand establishment of direct-seeded crops has usually involved seed treatment and/or seed covers. Planters have been evaluated for seed/plant spacing uniformity, singulation, furrow openers, and presswheel design; however, effects of presswheels and seed coverers on plant establishment have not been widely investigated. Five experiments were conducted in a fine sandy loam soil to determine effect of presswheels and seed coverers on emergence of direct-seeded cabbage and mustard. Seed were planted with Stanhay 870 seeder equipped with one of four presswheels and seed coverers. Presswheels included smooth, mesh, concave split, and flat split types. Seed coverers included standard drag, light drag, paired knives, and no coverer. Soil moisture at planting ranged from 8% to 19% in the top 5 cm of bed. Differences in plant counts taken 2 weeks after planting were minimal with any presswheel or seed coverer. Visual observation indicated the seed furrow was more completely closed with the knife coverer in high soil moisture conditions. All tests received at least 14 mm of precipitation within 6 days from planting, which may account for lack of differences in plant emergence.

Determining the Performance of Five Ornamental Grasses under Reduced Moisture Conditions

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 491a-491
Author(s):  
James T. Cole ◽  
Janet C. Cole
Keyword(s):  
Leaf Area ◽  
Stomatal Resistance ◽  
Time Domain Reflectometry ◽  
Grass Species ◽  
Drought Period ◽  
Shoot Ratio ◽  
Relative Water ◽  
Moisture Conditions ◽  
Water Treatments ◽  
Potential Transpiration

An experiment was conducted to evaluate the performance of five ornamental grass species under reduced moisture. This experiment was conducted in the greenhouse with three water treatments for each species: 1) Well-watered plants were irrigated daily throughout the experiment, 2) acclimated-plants were exposed to four drought cycles prior to a final drought period in which measurements were taken, and 3) non-acclimated plants received daily irrigation until undergoing a drought cycle in which measurements were taken. A drought cycle was defined as the time from irrigation until Time Domain Reflectometry (TDR) measured 0 (zero). Preliminary observations determined the plants to be under severe stress, but capable of recovering at TDR measurements of 0. All plants were established from tillers of a single parent for each species. Two plants of each species for the three treatments were established in five blocks. Leaf water potential, osmotic potential, transpiration, stomatal resistance, and relative water content were measured during the drought cycle. At the end of the experiment the leaf area and root and shoot dry weights were determined, root to shoot ratio and leaf area ratio were calculated, and the plants were analyzed for macronutrient and micronutrient contents.

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