Carl W. Mize

Design and placement of a multi-species riparian buffer strip system

A multi-species riparian buffer strip (MSRBS) system was designed and placed along a Central Iowa stream in 1990. Bear Creek, is typical of many streams in Central Iowa where the primary land use along the streams length is row crop (corn and soybeans) production agriculture or intensive riparian zone grazing. The Bear Creek watershed is long (∼ 35 km), narrow (3–6 km), and drains 7,661 ha of farmland. The MSRBS system is a 20 m wide filter strip consisting of four or five rows of fast-growing trees planted closest to the stream, then two shrub rows, and finally a 7 m wide strip of switchgrass established next to the agricultural fields. The 1.0 km long system, is located on an operational farm and is laid out in a split block design on both sides of Bear Creek. An integral part of this system is a streambank stabilization soil bioengineering component and a constructed wetland to intercept NPS pollutants in field drainage tile water flow. It is hypothesized that this system will function effectively as a nutrient, pesticide, and sediment sink for NPS pollutants coming from the upslope agricultural fields. Prior to establishment of the MSRBS system, the riparian zone along Bear Creek was grazed and row cropped to the stream edge. Since 1990 there has been dramatic alteration in the appearance and functioning of this riparian zone. After four growing seasons, the fast-growing tree species (cottonwood, silver maple, willow, and green ash) range in height from 2.4 m to over 5.5 m. Mean (four-year) biomass production of silver maple was 8.4 dry Mg ha−1, more than twice to seven times the yield from other silver maple research plots in Central Iowa. The shrub species, selected because of desired wildlife benefits, have done well in terms of survival and growth with ninebark, Nannyberry viburnum and Nanking cherry doing the best. The switchgrass grass has developed into a dense stand that effectively stops concentrated flow from the agriculture fields and allows for infiltration rates well above the field rate. Early root biomass data indicate significantly more roots below the MSRBS than agricultural fields. This suggests better soil stabilization, absorption of infiltrated water, and soil-root-microbe-NPS pollutant interaction characteristics within the MSRBS system than the cropped fields. Nitrate-nitrogen concentrations in the MSRBS never exceed 2 mg l−1 whereas the levels in the adjacent agricultural fields exceed 12 mg l−1. The water quality data collected suggest that the MSRBS is effective in reducing NPS pollutants in the vadose and saturated zone below the system. The soil bioengineering revetments have stabilized the streambank and minimized bank collapse. Initial results (from 4 months of operation) from the constructed wetland (built in summer 1994) indicate nitrate-nitrogen concentrations of the tile inflow water >15 mg l−1 whereas, the outflow water had a nitrate-nitrogen concentration of <3 mg l−1. Over time this wetland should become more effective in removing excess nitrogen moving with the tile flow from the agricultural fields because of the accumulation of organic matter from the cattails. Overall the MSRBS system seems to be functioning as expected. This MSRBS system offers farmers a way to intercept eroding soil, trap and transform NPS pollution, stabilize streambanks, provide wildlife habitat, produce biomass for on-farm use, produce high-quality hardwood in the future, and enhance the aesthetics of the agroecosystem. As a streamside best management practice (BMP), the MSRBS system complements upland BMPs and provides many valuable private and public market and non-market benefits.

Three-dimensional aerodynamic structure of a tree shelterbelt: Definition, characterization and working models

In order to make recommendations to landowners with regard to the design and management of tree shelterbelts, it is necessary to understand and predict the wind flow patterns associated with shelterbelt structure. A structural description is a prerequisite for any prediction of wind flow. Optical porosity (percentage of open spaces on the side view of a shelterbelt) has been used as a structural descriptor of a shelterbelt; however, it is a 2-dimensional measure unable to fully represent the aerodynamic influence of a tree shelterbelt. Based on numerous studies observing the wind fields associated with shelterbelt structure, the overall aerodynamic structure of a tree shelterbelt in three dimensions is defined by its external structural characteristics (length, height, width, and crosssectional shape) and by its internal structural components (amounts and arrangements of vegetative surface area and volume, and geometric shape of individual vegetative elements). In order to associate the defined structure with wind speed, turbulent stress, and pressure, it is characterized using two structural descriptors the spatial functions of vegetative surface area density (vegetative surface area per unit canopy volume) and cubic density (vegetative volume per unit canopy volume). For field estimation, the two structural descriptors are expressed in three dimensions using two working models in terms of 1- or 2- dimensional sub-functions capable of being defined with field measurements. This paper discusses the rationale behind the definition, characterization, and working models for the 3-dimensional aerodynamic structure of a tree shelterbelt.

Analysing treatment means in plant tissue culture research

Many researchers set up an experiment, make measurements, do an analysis of variance, calculate the mean response for each treatment, and then try to decide if the treatment means are significantly different and why. Much too frequently, Duncans multiple range test is used to test differences among means. It is only one of a number of techniques that can be used to examine treatment means. Some researchers are unaware of the different techniques and that the interpretation of the results of an experiment is strongly influenced by the technique used i.e. using two different techniques might produce two different interpretations of the results. Selection of the appropriate technique to use for a particular experiment depends upon the nature of the treatments and the objectives of the research. This paper discusses four techniques (ranking treatment means, multiple comparison procedures, fitting response models, and using contrasts to make planned comparisons) that can be used to examine treatment means and presents examples of the use of each one for plant tissue culture research.

Ecological Development and function of Shelterbelts in Temperate North America

As the world’s population continues to expand, the pressure on farmland, both from expansion of urban areas (United Nations, 2002) and from a need to produce more food and fiber (Hewitt and Smith, 1995; Gardner, 1996), will increase. In direct competition with the increasing demand for more food and fiber is a growing public desire for conservation of natural systems and a focus on quality of life issues (Matson et al., 1997; Jackson and Jackson, 2002; Pimentel et al., 2004). These two societal needs are clearly linked. Unfortunately, they are antagonistic, not complementary. The impacts of intensive agriculture, needed to increase food and fiber production, extend well beyond the field border (CAST, 1999). Similarly, many species found in natural systems, both flora and fauna, do not remain within protected reserves provided for their benefit and are impacted by land-use decisions in surrounding areas. A challenge to resource managers is to develop management strategies that support both sets of needs and lead to the “right compromise” between production agriculture, sustainability, and conservation of native floral and fauna (Mineau and McLaughlin, 1996; Swift et al., 2004). Shelterbelts and other types of linear forest systems, such as riparian buffer strips (Benton et al., 2003), can support both sets of needs and be a link between production agriculture and protection of biodiversity. These systems, both planted and naturally occurring, provide various ecosystem services (Guertin et al., 1997). While this review focuses on shelterbelts, many of the principles discussed apply to other linear forest systems.

Estimation of the three-dimensional aerodynamic structure of a green ash shelterbelt

The three-dimensional aerodynamic structure of a tree shelterbelt is described by two structural descriptors: vegetative surface area density (vegetative surface area per unit canopy volume) and cubic density (vegetative volume per unit canopy volume). Based on destructive measurements, estimates of both descriptors for a two-row 31-year-old green ash (Fraxinus pennsylvanica Marsh.) shelterbelt are developed. In order to estimate the structural descriptors in three dimensions based on data measured in two dimensions, equations to predict vegetative surface area and volume, their marginal distribution with height, and their marginal distribution across width at a given height are derived for each tree component: trunk, branches, leaves and seeds. The procedure to use these equations to estimate the structure of the green ash shelterbelt either in three dimensions or in the width and height dimensions is demonstrated. The estimated structure can be used to test current models of turbulence through a tree shelterbelt under a field conditions, and to simulate the wind fields as influenced by the actual structure of a tree shelterbelt. The developed equation can be used to generate the three-dimensional structure of a shelterbelt with a design similar to the sampled shelterbelts or a shelterbelt of green ash mixed with other species similar to those in the sampled shelterbelts. Thus, the boundary-layer flows as influenced by the overall structure of tree shelterbelts with different designs can be numerically simulated. These simulated results can provide guidance for shelterbelt design.

Statistical considerations for in vitro research: II — Data to presentation

SummaryThe paper is the second of two papers about statistical considerations that researchers should make while doing in vitro plant biology research. The first paper focused on aspects from developing a plan to do research through the collection of data. This paper continues with information about editing data, handling outliers, analyzing quantitative and qualitative data, comparing treatment means, preparing graphs and tables, and presenting results.

Effects of partial overstory removal on the natural regeneration of a tropical forest in Quintana Roo, Mexico

Abstract In a tropical, semi-evergreen forest in Quintana Roo, Mexico, a study was conducted to observe the effects of partial overstory removal (creation of multiple gaps) on natural regeneration, with special attention to commercially valuable tree species. Five 0.5-ha plots were subjected to different levels of overstory removal of 0%, 8%, 28%, 45% and 55%. The regeneration population 3 years after overstory removal was similar in density and composition to the population before overstory removal except for an unidentified liana that was not found in 1986 but was moderately abundant in 1989. Regeneration of commercial tree species (tolerant and intolerant), noncommercial tree species, and nontree species was compared with the residual basal area and percentage of basal area removed. Frequency of intolerant commercial species increased as residual basal area decreased. Frequency of tolerant commercial species was not affected by residual basal area or percentage of basal area reduced.

Agroforestry and forestry-related practices in the Midwestern United States

A survey, conducted in 1990–1991 on agroforestry and forestry-related systems in eight Midwestern states, showed that three traditional and three nontraditional agroforestry systems are practiced in the region. Of 46 traditional systems reported, most common was agrisilviculture (28), then silvipasture (12) and agrisilvipasture (6). These systems often involved corn, soybeans, and hay planted with tree species for nut, timber, or Christmas tree production, and cattle. Non-traditional agroforestry systems were field windbreaks/shelterbelts (29), treeshrub intercropping systems (21), and boundary plantings (11). These systems involved a variety of northern hardwood species evergreens, and shrubs. There was also a preponderance of specialized systems (97) of growing trees with the production of mushrooms, nuts, syrup, wildlife, and other nonwood products. The survey is exploratory in nature and, although the results may not represent a complete count of people involved with agroforestry in the region, the numbers reported may indicate where a practice may be prevalent. The results reflect the fact that much work still needs to be done by agroforesters in this region. They also provide some basis for further research on more suitable systems, and for identifying other researchable questions on agroforestry for the region. The methodology also made possible a bigger nucleus for networking of agroforesters and other interested people in the Midwest. Finally, although not normally considered as agroforestry, the significance of the other specialized systems reported in this survey is that they offer varied ways of connecting forestry with other activities in a largely agricultural landscape, and that they may even be seen as opportunities for easier transition into agroforestry.

Willingness of Iowa agricultural landowners to allow fee hunting associated with in-field shelterbelts

In 2004, four focus groups consisting of agricultural landowners were organized in Northcentral Iowa to assess opportunities for hunting along in-field shelterbelts and on adjacent lands. A majority of respondents (95%) allowed/practiced some hunting on their lands. About 55% of respondents indicated that the potential existed for developing a fee hunting market associated with in-field shelterbelts. Intangible features of hunting, such as recreation/enjoyment and better land stewardship, were ranked higher than tangible ones—additional income and provision of economic opportunities for local communities. Respondents were highly concerned with negative consequences of hunting—trespassing and hunter misconduct. On average, agricultural landowners were willing to accept (WTA) US

SBELTS: A model of soybean production under tree shelter

30 per visit per party of four hunters to allow hunting of ring-necked pheasants (Phasianus colchicus) on their land. About 33% would grant access to hunters free of charge. Those who lived in urban areas would require five times the monetary compensation (US