Landscape Mulch Research Articles

Carbon dioxide and oxygen exchange at the soil-atmosphere boundary as affected by various mulch materials

Mulching is a common soil management technique used in agricultural, nursery, and landscape settings. Despite multiple benefits, such as reducing weeds and evaporation, some mulches can also hinder gas exchange across the soil-atmosphere interface, and thus may have negative impacts on plant growth. The objective of this study was to determine to what degree commonly used landscape mulches will affect carbon dioxide and oxygen concentrations in the root zone and gas exchange across the soil-atmosphere interface in a controlled greenhouse environment. We used mesocosms filled with a soil-compost mix and covered the surface with different mulches. The experimental treatments included no mulch (control), arborist wood chip mulch, cardboard mulch, landscape fabric mulch, and polyethylene film mulch. The flux of CO2 across the soil-atmosphere boundary was measured with the dynamic closed chamber method. Concentrations of CO2 and O2 were measured in the mesocosms at two depths (6.5 and 13.5 cm) for a total of 16 days after covering the mesocosms with the mulches. Diffusion coefficients of CO2 through mulch materials were of the order of >10−3, 10−4, 10−5, and 10−6 cm2 s−1 for wood chips, cardboard, landscape fabric, and polyethylene film, respectively. Despite the different diffusion coefficients of the different mulches, CO2 and O2 concentrations in the soil under the various mulches were not significantly different as compared to the control, except for the polyethylene treatment. The orders of magnitude differences in diffusion coefficients among the mulch materials, however, could negatively impact a diverse soil environment such as those found in biologically rich landscapes with higher oxygen demands. Among the mulches tested, wood chips are a preferred method of mulching in terms of providing best gas permeability, particularly in landscape conditions.

Resolving two‐dimensional flow structure in rivers using large‐scale particle image velocimetry: An example from a stream confluence

AbstractLarge‐scale particle image velocimetry (LSPIV) has emerged as a valuable tool for measuring surface velocity in a variety of fluvial systems. LSPIV has typically been used in the field to obtain velocity or discharge measurements in relatively simple one‐dimensional flow. Detailed two‐dimensional or three‐dimensional characterization of flow structure has been relegated to laboratory settings because of the difficulty in controlling PIV limiting factors such as poor particle seeding, the need for camera rectification, and challenging field conditions. In this study we implement a low‐cost LSPIV setup using a high‐resolution action camera mounted above a stream confluence and water seeded with recycled landscape mulch. Time‐averaged 2‐D velocities derived from LSPIV are compared with those measured with an acoustic Doppler velocimeter (ADV) in the camera's field of view. We also assess the capabilities of this setup to resolve turbulent and time‐averaged flow structures at a stream confluence. Our results reveal that even in challenging field conditions a basic LSPIV setup can yield accurate data on velocity and resolve in detail the temporal evolution of flow structures on the surface of rivers. The resulting dataset contains velocity information at high spatial and temporal resolution, a significant advance in understanding flow processes at stream confluences. Our LSPIV analysis provides support for previous numerical modeling studies that have distinguished between Kelvin‐Helmholtz and wake modes of turbulent behavior within the mixing interface at confluences. This study shows that LSPIV can provide unprecedented levels of resolution of surface velocity patterns on rivers. Detailed velocity data derived from LSPIV can be used to evaluate numerical predictions of flow structure in complex fluvial environments.

Exotic Eucalyptus plantations in the southeastern US: risk assessment, management and policy approaches

As eucalyptus cultivation increases in the southeastern United States to provide feedstock for pulpwood, landscape mulch and an emerging bioenergy market, there is concern regarding potential invasiveness. Recently, models to predict the likelihood of invasiveness have produced conflicting results. Our uncertainty about invasion risk and the relative values we hold for environmental and industry protection will influence which management options and policies are pursued. Here we synthesize the essential practices and barriers to potential eucalyptus spread relative to different stages of the invasion process. Additionally, we offer a discussion of social and economic implications of the possible policies and regulatory techniques for mitigating future problems, with an emphasis on the often-recommended precautionary approach. We highlight future research needs and emphasize a landscape level, collaborative adaptive management approach.

Termite Behavior: Measuring the Postanoxic Consumption Rates of Landscape Mulches by Eastern Subterranean Termites

Populations of the Eastern subterranean termite, Reticulitermes flavipes, are widespread throughout most of the eastern United States. Subterranean termites have the ability to survive flooding conditions by lowering their metabolism. This lesson investigates the connection between the ability of termites to lower their metabolism to survive floods and their feeding behavior. Using an incubator, Petri dishes, and different types of mulch, termite consumption can be measured and compared. These results can be analyzed with a simple statistical test to look for significance.

Economical sustainability of pinestraw raking in slash pine stands in the southeastern United States

Raking pinestraw for use as landscape mulch has gained popularity over the last two decades in the southern U.S. as an intermediate income source for forest landowners, despite uncertainties associated with its long term impact on soil fertility. A Reed model was utilized to ascertain the effects of pinestraw raking on the profitability of slash pine stands. A model that estimates yearly needlefall was employed to determine the nutrient removals due to pinestraw raking. The land expectation value (LEV) for the intensively yearly raked unthinned and thinned stands was $6091ha−1 and $5142ha−1, respectively. Corresponding removals of carbon (C) and nitrogen (N) were 12Mgha−1 and 233kgha−1, and 11Mgha−1 and 182kgha−1 for unthinned and thinned stands, respectively. Stands intensively managed for pinestraw raking were more profitable than those extensively managed, although nutrient removals were greater under the intensive management scenario. Extensively managed and raked stands were more efficient in terms of nutrient removal and economic revenues. From a land stewardship perspective, managing for pinestraw on higher productivity stands may be more efficient in terms of realizing increased economic returns for similar levels of nutrient removal.

Development of Test Methods for Assessing the Fire Hazards of Landscaping Mulch

Landscape mulches are widely used adjacent to buildings and represent a potential fire threat to the building. To date, relatively limited research has been conducted to characterize the ignition and flame spread potential of the various types of commercially available landscaping mulches. Consequently, ignition and flame spread test protocols were developed to evaluate candidate mulch products based upon the scientific research involving mulches and forest litters. The ignition protocol used brands from the ASTM E108 test to determine the minimum brand size required for reliable burning of the mulch to the border of the 0.6 m square mulch bed. The flame spread on mulches was assessed for a mulch bed 0.46 m wide by 1.8 m long. The initiating source for the flame spread testing was a gas-fired line burner with an intensity of 108 kW/m. The ability of the mulch bed to propagate flame remote from the initiation source was determined and the resulting flame spread rate was measured. The protocols were exercised in using various types of landscaping mulch (pine bark, hardwood, pine bark nugget, and pine straw mulch). The test protocol is found to be a viable method to provide quantitative measures of the hazards of landscape mulches. Further potential areas of test method development are identified.

Market Demands and Characteristic Preferences for Pine Straw in Alabama

Pine straw is a popular landscape mulch material used by landowners and homeowners throughout the southeastern United States. Pine straw is collected, transported, and sold through an informal network of landowners, harvesters, forest labor contractors, and dealers. Quality varies widely, depending on factors such as species of pines, land management practices, and harvesting techniques. A mail survey of landscapers, retailers, and lawn maintenance specialists was used to assess market demand and characteristic preferences of those buying and selling pine straw in Alabama. Purchase volumes varied widely among buyers, both annually and for single-time purchases. Buyers placed high importance on straw free from weeds and foreign material. There were differences in species of pine straw purchased among respondents, some of which appear attributable to location of the buyer. While there was a strong preference for longleaf pine straw, those who reported purchasing loblolly and slash were more likely to prefer those species. Responses from buyers who know their pine straw's origin reveal differences in the distance from which they purchase pine straw, with many buying straw from more than 150 miles away. Results also show that many do not know where their pine straw comes from or what species it is.

Fresh Recycled Mushroom Compost Suppresses Artillery Fungi Sporulation: A 4-Year Field Study

Abstract Artillery fungi (Sphaerobolus spp.) have recently emerged from an interesting mycological curiosity that grow in landscape mulch, to a problem of emotional stress and financial concern to homeowners, as well as insurance companies, mulch producers, and landscape contractors. Artillery fungi shoot their spore masses (gleba) towards sunlight and/or reflective objects such as light-colored house siding or automobiles, peppering the surface with small sticky tar-like black specks. Once dry, gleba are very difficult to remove from surfaces such as vinyl siding. If they can be removed, gleba usually leave a brown stain that is extremely difficult to clean. We previously reported that aged (weathered or composted outside) mushroom compost (MC), when blended with landscape mulch at ≥ 40% by volume, suppressed artillery fungi sporulation in the mulch. In this paper, we report that fresh MC, taken directly from the mushroom house and blended with landscape mulch without aging, also reduces artillery fungi sporulation as follows: 0% MC (control = 0% reduction), 10% MC (62%), 20% MC (80%), 40% MC (95%), and 100% MC (97% reduction in sporulation). Landscape companies using fresh MC, rather than aged MC, need not invest time and money in additional MC aging, composting, and processing.

Recycled Mushroom Compost Suppresses Bird's Nest Fungi in Landscape Mulch

Abstract Mushroom compost blended into landscape mulch has been reported to suppress sporulation of artillery fungi (Sphaerobolus spp). In this paper, mushroom compost is also shown to inhibit growth and sporulation of a common bird's nest fungus in landscape mulch. Field plots containing 0, 10, 20, 40, or 100% (by volume) mushroom compost blended with a common landscape mulch were naturally infested with a bird's nest fungus (Cyathus stercoreus (Schweinitz) de Toni). Compost at percentages ≥ 40% significantly reduced growth and sporulation of the bird's nest fungus. It is likely that mushroom compost contains populations of beneficial microbes that are antagonistic to, or feed on, various species of fungi.

Effect of Landscape Mulches and Drip Irrigation on Transplant Establishment and Growth of Three North American Desert Native Plants

Abstract A two-year experiment was conducted to determine growth responses of three North American desert native plants, brittle bush (Encelia farinosa), four wing salt bush (Atriplex canescens), and Santa Rita prickly pear cactus (Opuntia santa rita) to four landscape mulch treatments (shredded landscape tree trimmings, composted ponderosa pine residue, decomposing granite, or a no mulch control). In addition, brittle bush and four wing salt bush plants were drip irrigated with either 1275 liters (337 gal) or 2550 liters (674 gal) of water-plant−1year−1. Santa Rita prickly pear cacti were not irrigated. Transplant survivability of brittle bush was differentially affected by mulch treatment. In contrast, mulch treatments had no impact on survivability of four wing salt bush or Santa Rita prickly pear. Mulch treatments also had no effect on growth indices of all plants. Compared to the no mulch control treatment, shredded tree trimming mulch increased relative water content of Santa Rita prickly pear padded stems. Shoot dry weights were greatest for non-irrigated four wing salt bush and brittle bush. These findings suggest that supplemental drip irrigation and inorganic mulches might not be needed to grow some North American desert plants in southwest urban landscapes.

In Vitro Screening of Fungicides to Control Artillery Fungi

Abstract We evaluated the influence of 26 fungicides at four different concentrations (0.1, 1.0, 10.0, and 100.0 a.i.) on in vitro growth of an artillery fungus (Sphaerobolus stellatus isolate SS8) in Petri plate culture. The most effective fungicides, as determined by comparison of mean EC50 values, were polyoxin-D and azoxystrobin, followed by pyraclostrobin, triademifon, tebuconazole, propiconazole, thiophante-methyl, triticonazole, thiram, and fludioxonil. These in vitro laboratory findings need to be evaluated in the field before specific fungicides can be recommended to control artillery fungi in landscape mulch.

Weed Control and Organic Mulches Affect Physiology and Growth of Landscape Shrubs

Landscape mulches are widely promoted to improve soil moisture retention, suppress weeds, and improve the growth of landscape plants. The objective of this project was to determine the effect of common landscape mulches (pine bark, hardwood fines, cypress mulch, color-enhanced ground pallets) on soil moisture, soil pH, weed control, and physiology and growth of landscape shrubs. Two additional treatments were not mulched: no mulch + no weed control and no mulch + weed control. Growth was measured on eight taxa (Euonymus alatus ‘Compactus’, Spiraea ×bumalda ‘Goldflame’, Weigela florida ‘Java red’, Taxus ×media ‘Runyan’, Thuja occidentalis ‘Golden Globe’, Hydrangea paniculata ‘Tardiva’, Viburnum dentatum ‘Synnestvedt’, Viburnum trilobum ‘Compactum’). Leaf gas exchange [net photosynthesis and stomatal conductance (g s)] were measured on Hydrangea paniculata, V. dentatum, and V. trilobum only. All mulches increased soil moisture compared with no mulch + weed control. There was no difference in soil pH or foliar nitrogen among treatments. All mulches, except cypress mulch, increased plant growth of most shrub taxa compared with no mulch without weed control. Mulches increased g S relative to no mulch without weed control. Photosynthetic rates of plants mulched with cypress mulch were less than the other mulches and not different from no mulch. Overall, the result suggests that, except for cypress mulch, the organic mulches tested are equally effective in improving growth of landscape plants. Reduced photosynthetic efficiency and growth of shrubs with cypress mulch suggest potential allelopathic effects.

Effect of Landscape Mulches on Desert Landscape Microclimates

Effects of three landscape mulches: 1) composted ponderosa pine residue; 2) uncomposted shredded landscape tree trimmings; and 3) screened decomposing granite, were compared over the course of 2 years (2004 to 2005) for their ability to modify air and soil landscape microclimates in Phoenix, Arizona, U.S. Temperatures at the surface of the two organic mulches were generally higher during the day and lower at night than at the surface of either decomposing granite or soil without a mulch cover. During nighttime hours, decomposing granite mulch or soil without a mulch cover emitted more long wave radiation than the two organic mulches. Conductive heat transfer through the organic mulches was generally lower than through decomposing granite. Daytime temperatures of soil at 5 and 30 cm (2 and 12 in) depths were generally lower beneath the two organic mulches than under decomposing granite mulch or soil without any landscape mulch cover. Soil covered with organic mulch evaporated less water than soil without mulch. Under desert conditions, the two organic mulches were more effective at moderating heat gain and water loss from soil than decomposing granite mulch because of an increased resistance to heat transfer and evaporation.

Impact of Mulches on Landscape Plants and the Environment — A Review

Abstract Mulches provide aesthetic, economic and environmental benefits to urban landscapes. Mulching is especially useful in the establishment of trees in landscapes that receive minimal care, such as restoration sites. In general, mulches improve soil health, creating healthy populations of plants and associated animals. These biodiverse, stable landscapes are more resistant to stress, are more aesthetically pleasing, require fewer applications of pesticides and fertilizers, and are ultimately more sustainable than those without mulch cover. All mulches are not created equally, however, and this review compares the costs and benefits of landscape mulches as reported in the scientific literature. It also presents real and perceived problems associated with various landscape mulches.

Landscape Mulches and Termite Nutritional Ecology: Growth and Survival of Incipient Colonies of <I>Coptotermes formosanus</I> (Isoptera: Rhinotermitidae)

Alate swarms are one of the major visible signs of the expansion of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), in an area. Successful establishment of an incipient colony is thought to mainly rely on available food resources and moisture. The large-scale use of tree-based mulches in landscapes may inadvertently contribute to local establishment and growth of C. formosanus colonies. This research investigated the nutritional ecology of incipient colonies of C. formosanus feeding on seven tree-based, weathered, and nonweathered landscape mulches: pine straw, pine bark, cedar wood, water oak, eucalyptus, cypress, and melaleuca. Incipient colonies of C. formosanus feeding on pine straw, either weathered or nonweathered, produced significantly more progeny over the course of 1-yr feeding than colonies feeding on the other mulches tested. Regardless of weathered or not, the incipient colonies feeding on pine straw, eucalyptus, bald cypress, and water oak mulches had significantly greater survival rates after 360 d (53-77%) than colonies feeding on the other mulches tested (0-13%), but colonies feeding on nonweathered water oak had significantly lower survival (8%) than those kept on weathered water oak (58%). Colony fitness values were significantly different between the weathering treatment groups and among the different types of mulches. With regard to colony growth characteristics, three distinct growth patterns were identified: a high number of progeny (>100) with high colony survival rate (>50%), a medium number of progeny (12-50) with high colony survival rate (>50%), and a small number of progeny (0-10) with low colony survival rate (<5%). These findings suggest that different types of mulch substrates could significantly impact the nutritional ecology of the founding pairs and the successful establishment of incipient colonies during the swarming season.

American Crow Caches Rabbit Kits

For corvids, the decision to cache is a complex behavior likely influenced by many interacting factors. On 8 April 2004, I observed an American Crow (Corvus brachyrhynchos) caching eastern cottontail (Sylvilagus floridanus) kits taken from a rabbit nest on the Missouri State University campus in Springfield, Missouri. The crow cached at least three kits and flew away with at least one other. Caches were covered with dead leaves and landscape mulch. During the ensuing 3-day period, some caches disappeared, were partially eaten, or were moved to a different nearby location. To my knowledge, this is the first documented case of caching numerous rabbit kits from a single nest, and it is one of the few documented cases of cache-moving by American Crows.

Use of Mushroom Compost to Suppress Artillery Fungi

Abstract Mushroom compost (spent mushroom substrate, SMS, mushroom soil) exhibits suppressive characteristics against various fungi, as well as against plant diseases caused by fungi. In addition, mushroom compost has physical and chemical characteristics that make it ideal for blending with landscape mulch to enhance growth of horticultural plants. There is currently an oversupply of used compost in mushroom-growing areas, where it represents a major disposal and regulatory problem. Concurrently, artillery fungi (Sphaerobolus spp.), which commonly live in landscape mulch, have recently become a plague for many homeowners due to the sticky spore masses they expel onto houses and cars. There is increasing interest among homeowners to control artillery fungi without the use of chemical fungicides. Therefore, we have explored the use of aged mushroom compost as a biocontrol agent for artillery fungi. The abundance of mushroom compost, as well as its antagonistic nature to fungi, made it an ideal candidate to blend with landscape mulch to suppress artillery fungi without the use of fungicides. We previously reported that 100% aged mushroom compost suppressed artillery fungi. In the current 3-year field study, we examined the suppressive nature of lower percentages of aged mushroom compost blended with wood landscape mulch. Lower percentages of compost did suppress artillery fungi, but the high variability in the data precluded detailed statistical analyses. Nevertheless, blending mushroom compost with landscape mulch may yield a possible solution for both the compost disposal and the artillery fungi problems.

A Comparison of Surface Mulch Type on Patterns of Above- and Below-ground Temperature and Surface Net Radiation in a Drip-irrigated Desert Landscape

Mulches applied to landscape surfaces can moderate soil temperatures by changing the surface heat energy balance and conserve soil water by reducing evaporation rates. In the Southwest, decomposing granite is commonly used as landscape mulch. However, organic mulches, such as pine residue mulch and shredded tree trimmings, are becoming more available as industry by-products. Recent impetus toward water conservation and recycling forest and urban tree waste into urban landscapes has increased the need to better understand how such mulch types effect the temperature, moisture. and light quality of drip-irrigated landscapes typically found in the Southwest. We compared effects of three mulches, two organic (composted ponderosa pine residue and shredded urban tree trimmings) and one inorganic (Red Mountain Coral decomposing granite), turf grass, and bare soil applied to 14 drip-irrigated landscape research plots on below-ground soil temperatures at depths of 5 cm and 30 cm, temperatures at the mulch-soil interface, mulch surface temperatures, diel mulch surface net radiation, and albedo. Below-ground soil temperatures were more buffered by organic mulches, and mulch-soil interface temperatures were lower under organic mulch than inorganic mulches. Inorganic mulch daytime surface temperatures were lower than organic mulch surface temperatures. Nighttime net radiation values were less negative over organic mulches than inorganic mulches and albedo was significantly higher for the inorganic mulch and bare soil treatments. These results provide evidence to show that organic surface mulches have higher resistances to heat transfer than inorganic mulches, which could improve landscape plant water and nutrient use efficiencies by lowering high summer root zone temperatures.

Artillery Fungus Sporulation on 27 Different Mulches — A Field Study

Abstract During the last decade, the ‘artillery fungus’ has emerged from an interesting mycological curiosity that grows in landscape mulch to a problem of major financial concern to homeowners, insurance companies, mulch producers, and landscape contractors. This common inhabitant of landscape mulch produces sticky spore masses (gleba) that it shoots towards the light or towards reflective objects such as light-colored automobiles or house siding. We evaluated 27 different mulches in the field to determine their ability to support growth and sporulation of the artillery fungus. Each mulch type was inoculated in 1998 with the artillery fungus and the amount of sporulation (number of spore masses on targets) determined annually until 2002, approximately 4 years after inoculation. We grouped the 27 mulches into nine general categories that had common characteristics: mulches that originated from large piles of bark and wood mixtures, mulches blended with 5% compost, cedar mulch, mulches commercially designated as ‘bark’ but containing considerable wood, dyed wood chips, non-dyed wood chips, cypress mulch, large bark nuggets, and 100% spent mushroom substrate. The mulches obtained from large piles shredded blends of bark and wood supported significantly greater levels of artillery fungus sporulation than did other mulches. Such highly susceptible mulches should be avoided if the artillery fungus is to be minimized. In contrast, large bark nuggets, cypress mulch, and 100% spent mushroom substrate supported less artillery fungus. Other mulches supported intermediate levels of sporulation. All wood/bark landscape mulches will eventually support the artillery fungus over extended time periods (i.e., 34 years), and even more tolerant mulches should be replaced or covered with a fresh layer of mulch on a regular basis.

Tree Pathogen Survival in Chipped Wood Mulch

Uncomposted wood chips are often used as landscape mulches. Chips are commonly derived from landscape trees removed because they were in poor health and often contained plant pests. Chips are also derived from pallets and other wood packing materials that may harbor indigenous and exotic plant pathogens. A study was initiated to determine how long a fungal plant pathogen could survive in uncomposted wood chip mulch in an urban landscape. Thyronectria austroamericana, the causal agent of Thyronectria canker in honeylocust (Gleditsia triacanthos) trees, was used to inoculate branches of honeylocust trees. Cankered branch pieces were placed into mulched areas surrounding honeylocust trees growing under two irrigation regimes. Thyronectria austroamericana recovered from cankered wood pieces after 98 weeks produced cankers when inoculated into branches of honeylocust trees. Irrigation regimes did not affect recovery of the fungus. Cankered wood pieces remained a source of inoculum for 143 weeks after placement in the mulched areas. Due to the longevity of pathogen survival, uncomposted mulch derived from honeylocust trees infected with T. austroamericana should not be placed around honeylocust trees in urban landscapes. Using uncomposted wood chips derived from wood packing materials could increase the risk of introducing exotic plant pathogens to urban landscapes.