"We are entering a new era in agriculture and resource management, one in which we actively design and create agro-ecosystems, forests, and watersheds, instead of depleting them. In the process of learning how to design, create and manage these new resource systems, we learn more and more about how to work with nature rather than against it." --Wilkinson and Elevitch, 2005
Many non-timber forest crops (NTFC) can be produced by forest farming. Some are more suitable for particular combinations of goals, site conditions, and markets. This Learning Unit will help you decide which crops are suitable for your circumstances. It focuses on opportunities and limitations created by climate, soils, vegetation and other environmental conditions of your property.
This Unit presents a strategy for determining what your environmental conditions are and using that information to select the crops best suited to your site. The strategy is organized around the following three sets of activity that are required in planning an integrated forest farming system:
The Sections of this Unit link to worksheets  examples , and other web resources .
In addition to the strategy that is presented in this unit for undertaking these overlapping sets of activity, you may wish to consult other valuable resources that deal with designing integrated land use systems. Some that are similar to forest farming include other agroforestry systems, permaculture, residential landscaping, and timber management. See Additional Design Resources, below.
Site assessment is a process of utilizing a set of tools and resources for determining the advantages and limitations of your site. The approach we have developed (HWWFF) is designed to help you make intelligent decisions about what crops you can realistically incorporate into your forest farming site design. It also directs you to tools and resources that will help you collect appropriate information about your site.
Light, water, temperature, nutrients, and biological organisms are the components of the biophysical environment that will determine if any potential NTFC is well adapted to your site. In practical terms, the availability of these resource are determined by
The scope of your site assessment depends on whether you intend to grow a single NTFC such as ginseng, or to manage a more complex mixture of forest crops such as fruits, nuts, medicinal herbs, mushrooms, ornamentals, and handicraft material. If you plan to grow only a single crop then “crop selection” is a relatively simple matter of finding out what conditions are required for that crop and determining if it is compatible with your site. You may decide to take advantage of the various environmental niches offered at different parts of your site and at different layers within the forest’s vertical profile (ground, middle understory, canopy) to achieve complementary interactions among different components of a multicrop forest farming system. The process of site assessment obviously becomes more complex if you choose this course, but also more informative and possibly more fun!
The resources in Learning Unit 2: Site Assessment and Non-Timber Forest Crop Selection include the following:
It is recommended that you print the Blank Site Assessment Workbook for recording data, an activity that usually takes place in the field. [Printable Blank Site Assessment Workbook].
The online text and guidelines serve as your course text, and instructions for moving through the course material. It provides background information while directing you to the worksheets and steering you through the assessment process.
The linked worksheets are a series of tables serving as your site assessment checklist and record. Printing this document is recommended [Printable Version] for ease of use and future reference.
The MacDaniel’s Nutgrove (MNG) Case Study Site Assessment Workbook and Supplements provide examples of how to complete the assessment worksheets by using information from a forest farming teaching, research and demonstration site at Cornell University, the MacDaniels Nut Grove.
Throughout the online text, workbook  & MNG icons link to the respective documents.
Workbook and Map Resources
Additional Design Resources
Why use maps? Unless your site is very small (<1 acre) it is unlikely to be completely uniform in terms of slope, aspect, soil composition, drainage, existing vegetation and other features. An analysis of a single location within your site could be minimally useful at best, and downright misleading at worst. It is important to sample your site at enough locations to develop a reasonable picture of the variation that exists. It is equally important to retain a clear record of the sampling location for each set of results you obtain. Maps are useful tools in sampling and recording variation within your site.
In Section 1 we introduced the idea that planning your forest farm involves a three-stage process: 1) gathering information about your site, 2) comparing your site characteristics with the requirements of potential NTFCs (candidate species) and, 3) integrating the two into a preliminary site design. Maps are helpful in visualizing and coordinating this process, and mapping is an important part of all three stages.
Consider the following three types of maps:
A good way to record variation within your site is to start with an accurate base map. Then add information arising from your assessment activities to create your site assessment map. In this way your base map becomes your site assessment map. Third, your crop selection/design map will locate where you will establish the different elements of your forest farming system.
The Workbook (page # 4) lists types of maps that can contribute to your map making process. Use this worksheet to keep track of types and sources of maps that you use to make your base map and build your site assessment maps.
See the corresponding pages in the MNG Case Study Workbook for examples maps and sources.
Workbook and Map Resources
A base map is a spatial representation of your property as it is at the present time, before you begin the process of site analysis and before you do any new site development. It should include property boundaries, drawn to scale, and oriented with respect to compass directions. Your base map should indicate major landforms including hills, valleys, ravines, wetlands, forest edges, streams, etc. It will also include the location of roads, bridges, buildings, utility rights of way and any other fixed features, natural or man made. An example baseline map may be found at the end of this section. [The MNG Case Study Workbook provides another example ].
The best starting point for a base map is the survey map associated with the legal deed to the property. In most cases boundaries, directional (compass) orientation, angles, etc. are accurately represented based on a professional survey. It may be advisable to walk your property lines to make sure your understanding of the boundaries corresponds to the survey map. The adjacent property owner should be in agreement, so there is no confusion or disagreement about the location of posted signs, fences, etc. Drawing on or otherwise altering your survey map is not recommended, so make several copies or tracings (at least 3) of the survey map. Use one for your base map, one for your site assessment map, and another for your design map. Be sure that your map includes a scale indicator such as “1 inch = 500 ft”. It should also include a directional indicator, such that N at the tip of an arrow points North relative to features on your map.
If no survey map is available, then it will be necessary to create your base map from scratch by walking your property lines and carefully measuring distances and directions with a compass. If a high level of accuracy is not critical then you can estimate distances by counting your paces and multiplying the number of paces by the average length of your pace. More specific guidelines for creating a base map may be found in the Toolbox below, Base Mapping Resources.
Base Mapping Resources
Topographic maps and aerial photographs are useful resources for adding landform and elevation data to your base map. We discuss each in turn.
A “topo” map, or “quad sheet” usually refers to a 7.5 minute (1:24,000) USGS topographic map. These maps exist for the entire USA. The USGS topographic map section corresponds to your site so you can “see” hills and valleys in relation to each other, and other topographic features such as lakes, streams, marshes, roadways, etc.
Topographic maps can be obtained from a variety of sources including outdoor-activities equipment stores, public libraries, or ordered online directly from the US government’s USGS web site, which is provided in the Topographic Map Resource Box below. Each map has a unique name which can be used for ordering it. The USGS “Map Locator” online resource, also described in the Resource Box, can be used to determine which map corresponds to your area.
There are also numerous commercial websites that will custom assemble a topographic map from any area you specify, and you download (for a fee) a digital copy of that map. This could include only part of one or parts of several official USGS maps. USGS Topographic maps are also available at some public libraries. It is important to remember that USGS topographic maps are at a much larger scale (1”= 50,000) than a typical property deed survey map (1 inch = ?). Interpretation of map symbols and other information about using a topographic map are explained by Jim Ochterski in Using Topographic Maps in the toolkit below.
Topographic Map Resources
If you are able to acquire aerial photographs of your site, they can be useful for estimating forest cover density and other visual features such as the location of buildings. According to Jim Ochterski, “Aerial photographs will help you get a bird’s eye view of your forest. With it, you will see features you’ve not seen before.” One option is to draw your property boundaries and other features directly on to a sufficiently high resolution aerial photograph of your site and use it as your base map. Aerial photos can be obtained from a number of commercial online or other sources. Several sources are listed on the USGS website, View Online USGS Maps and Aerial Photo Images.
Now that you have some understanding of the types of maps available that may be useful to you, notice that [ Workbook page 4 ] provides an opportunity to record those you wish to reference and from what sources you obtain the specific maps. [ See the MNG Case Study Workbook ].
Workbook and Map Resources
Aerial Photograph Resources
Because land is not homogenous and it is likely you will not want to manage your site uniformly, it is useful to delineate zones. Differences in topography; microclimate (temperature, precipitation, light and wind exposure), landscape features (ponds, gullies, clearings, older or younger forest stands) and vegetation type are useful considerations in zone delineation.
Past and present land use affect site characteristics and probably how you will develop your site. There are some parts that you may not want to manage at all, because of poor conditions, or obstacles, such as distance, flooding etc. Others may be worth investing in more heavily. As you “zone” your land, based on the information and activities described here, indicate the zones on your base map.
A little information about past land use, particularly past agricultural use can help you or an experienced agriculturalist make inferences about soil health, nutrients and possible contamination. Experienced foresters, naturalists and agriculturalists are 3 resources for determining how long ago your forested or un-forested land was used for agriculture. Past tax maps and neighbors are others.
As you learn or make inferences about past use of your site, enter the uses in Workbook page .
[The MNG Case Study Workbook illustrates some possibilities on page . ]
Current uses also inform a crop plan. Enter current land uses or obstructions in Workbook page .
[The MNG Case Study Workbook illustrates some of these. ]
Workbook and Map Resources
In section 3 you will learn about macroclimate and microclimate. Macroclimate refers to large scale regional weather conditions and long term trends in cloud cover, humidity and precipitation, and temperature. Microclimate is a function of short term, local fluctuations in light, temperature, and moisture at a particular site. These factors are affected by distinctive site conditions such as wind barriers and shade created by trees and other obstacles, the aspect (direction) and slope of a hillside, frost pockets, streams banks, etc. Both macroclimate and microclimate contribute to growing conditions, so knowledge of these factors should inform your selection of crops.
You have completed your base map and are ready to begin assessing climatic variables at your site. Workbook pages [8-12] designate specific data for your macroclimate and microclimate that we suggest you record and consider in planning. Weblinks to sources of historic macroclimatic data are provided in the resource boxes in sections [3.1-3.2]. Methods for estimating microclimatic differences between the zones in your site are described in section [3.3].
Use a copy of your base map to display the location of as much of the macroclimate and especially microclimate information from the workbook as is practical. Keep in mind, however, that not everything will fit on the map. For the section on microclimate [3.3] you will be referring to the zones that you designated based on topography or other visible features of your site [Section 2.1].
Workbook and Map Resources
Remember that the term macroclimate refers to large scale regional weather conditions and long term weather trends. We distinguish this from microclimate, which refers to shorter term, more localized fluctuations in weather. Since both affect the climate at your site, both are important in crop selection.
For this section become familiar with the resources below or find comparable information sources for the state your site is in. This and section 3.2 will help you complete workbook pages [8-10].
The most direct way to characterize macroclimate is to consider how each of its major components – temperature, precipitation, and light have behaved “historically” at least over the past 5 to 10 years. The National Weather Service and other organizations collect raw climatological data and make summaries available to the public regarding high, low and average temperatures, rainfall, number of frost free days, date of first and last frost, etc. Keep in mind that conditions at your particular site may vary from regional averages based on factors affecting microclimate. None the less, regional climate summaries from selected weather stations near you can be useful in the process of crop selection.
Availability of historical meterological records is uneven among Northeastern states. The most comprehensive information is available for Pennsylvania through the Penn State Climatologist. For New York and other Northeastern states it is more difficult to look up information for each of the categories in the table below.
Weather patterns at a regional scale (macroclimate) are at least somewhat similar from year to year. Different plant species are predictable in their ability to tolerate low winter temperatures, and in the length of the growing season and the amount of accumulated warmth they need to mature a crop. With this knowledge, plant scientists have developed two very important predictors of plant performance. Plant Hardiness Zones (PHZ) are based on the year to year predictability of minimum winter temperature. Growing Degree Days (GDD) are based on the heat requirements of different crop species. Plant Hardiness Zones (PHZ)
The length of the growing season (average number of frost free days) and the average precipitation play important roles in how various NTFC species will perform at your site. It is the extremes of temperature, however, and in particular the minimum low winter temperature that ultimately will limit your choices. If a given species cannot tolerate the lowest winter temperature that is likely to occur, then it does not matter what the average temperature or precipitation level is. It probably will be a waste of your time to try to grow that crop.
Below is a Plant Hardiness Zone Map developed by USDA from a national compilation of local weather records. It divides the US into 10 hardiness zones and each zone into 3 sub zones based on probable minimum winter temperatures. Information about the hardiness zone requirement (cold hardiness) is available for most species in the crop selection matrix developed for this course [link to matrix]. So knowing the plant hardiness zone for your site and the PHZ requirement for any species you wish to consider provides a good first cut in deciding what species are suitable to grow there.
Plant Hardiness Zone (PHZ) Resources
It is well known that a given crop takes longer to mature during a cool growing season than during a warm one. When the temperature drops below a certain critical temperature (usually assumed to be 50F) the crop will cease growing and not make any more progress towards maturation until the temperature again rises above that critical temperature. Growing Degree Days (GDD) are a measure of the total amount of heat above the critical 50F level, accumulated during the course of a growing season. This is a useful predictor of the time required to ripen many important agricultural crops.
GDD also have been used to predict outbreaks of insects and disease so farmers can adjust the timing of appropriate control measures. In some areas the accumulation of GDD are carefully monitored by weather stations or other agencies on a county by county basis. In other areas the GDD are not at a local level, and it is necessary to rely on more general regional data. . GDD requirements for specific crops have been estimated and published for a number of woody crops including tree fruits, nuts and berries. If GDD requirement is available for particular NTFCs we have included this information in the crop selection matrix.
For example, MacDaniels, 1981 (1) indicated that temperate nut crops (walnuts, hickory) require about 2250 GDD. From the GDD summary map provided in his publication Nut Growing in the Northeast, you can see in Ithaca, NY (center of Tompkins County shown on the map), that the MacDaniels Nut Grove lies on the isoline between 2250 and 2500 GDD. This means that it is highly likely that during cooler than average years nut crops will not have time to mature, but they would during higher than average years. Indeed this is the problem faced in cultivation of hickory nuts as a NTFC at that location. During cooler years nutmeats shrivel in the shell after post harvest drying because at the time of harvest, at the end of the growing season, they still have a relatively high moisture content and low oil content.
Using the links below or similar sources for the region your site is in, find GDD data to fill out as much of the GDD table on page [9-10 ] as is practical.
Growing Degree Day (GDD) Resources
Pennsylvania and the Northeast
1. MacDaniels, L.H. 1981. Nut Growing in the Northeast. Plant Science. Floriculture and Ornamental Horticulture. College of Life Sciences and Agricultural Sciences, Cornell University. Bulletin 71.
In addition to the effects of large scale regional climate patterns, conditions on your site are affected by local features that affect temperature, moisture and lighting. The most influential of these features are slope (steepness), aspect (direction), exposure, canopy coverage (light penetration) and air drainage (frost pockets).
As you begin to determine these attributes for your site, record your data and notes in Workbook pages [11&12]based on the example provided in the MNG Case Study pages [11-12]. Also document points (places within each zone) which appear to represent important differences in features that affect microclimate, as listed above.
You may decide to modify your zones based on what you learn about microclimate. As you read about these factors, note which monitoring methods you prefer for each.
Monitoring site temperature is a long term process that involves using one or more max/min thermometers to record daily temperature extremes. A reason for measuring temperature at one or more locations of your site is to estimate GDD if that information for your area is not published. This information is useful, also, if your site differs considerably in temperature or elevation from the nearest weather station from which GDD values are based. Additionally, by recording temperatures of several areas, you may find microclimatic differences in the zones you designated in [2.2]
According to Carl Davies, who was a forward thinking agroforestry expert in the Northeast, a difference in average temperature of 2.5 F between a hilltop and the frost pocket at the bottom of the hill would result in a difference of as much as 450 GDD over the growing season. Differences of this scale could significantly effect your crop selection. The figure below from his paper Microclimate Evaluation and Modification for Northern Nut Tree Plantings(1) illustrates a method for estimating GDD based on average annual and average July temperatures for a site.
To use the chart, locate your mean (average) annual Fahrenheit temperature at the bottom (35-65), draw a vertical line up until you reach the diagonal line which represents your mean July temperature (60-80). From that point, draw a horizontal line to the left to determine your mean annual growing degree days on the 400-5000 scale.
In Microclimate Evaluation and Modification for Northern Nut Tree Plantings, Davies also explains how to use the nomogram to estimate growing degree days using weather station and site temperature data from only a few months. This paper explains how GDD, Frost Free Days (FFD) and windbreaks effect nut tree growth and provides additional methods for estimating growing season temperatures for particular sites. [Download entire article]
Few potential forest farming sites in the Northeast are on flat ground. Slopes affect crop performance by influencing runoff and erosion potential, soil moisture content, soil composition, air drainage and the duration of exposure to direct sunlight. Ginseng, for example, is typically found in the wild on relatively steep slopes because they are better drained than flat land. Shagbark hickory is generally found on well-drained slopes, whereas shellbark hickory prefers moister flat valley bottoms. There are several different methods for measuring slope (the angle of a hill). One is the use of a forester’s instrument called a clinometer. Another is the “rise over run” method, and the third is simply the “eye ball” estimate.
A clinometer is a simple forester’s instrument used to measure either the slope of a hill or the height of a tree, in either % slope or in degrees. For instructions in how to use it see the Vegetation/Terrain Field Equipment Procedures, weblinked below.
If you do not want to invest in a clinometer you can measure the distance in height gained for a given horizontal distance across a hill side to calculate the percent slope using the following method.
The percent slope is distance B divided by distance A expressed as a percentage, or:
% Slope = (B/A) x 100
This method reveals that a 45° angle is the same as 100% slope.
For most purposes it is sufficient to describe your slope in relative terms – slight, moderate, steep or very steep. Remember that a 100% slope (very steep) is equal to a 45° angle. See the figure below for examples.
Slope Measurement Resources
Aspect is the compass direction that the slope of a hill faces. Generally, north and northeast facing slopes get less total sunlight during the course of a day than south or southeast facing slopes, which are consequently hotter and dryer. This can have a major impact on NTFC compatibility. For example, ginseng typically grows best on north or northeast facing slopes because it prefers cooler, moister conditions. Aspect can be determined either by standing on the slope with a compass or from a topographic map. The compass direction from top to bottom is the aspect.
If you have a topographical map of your site you can mark slope aspects in your workbook and map without going into the field. Primary (N,E,S,W) and secondary (NE,NW,SE,SW) cardinal directions are sufficient. If you are disappointed that your slopes generally face the wrong direction for particular crops, go into the field and look for smaller raised or depressed areas that face a more favorable direction for crops you are interested in growing.
Forest Farming, by definition, is a system for growing NTFCs under the canopy of an established forest or wood lot. Hence, forest farming crops grown in the mid or understory are exposed to full or partial shade. This is an important difference between forest farming and most conventional agriculture. NTFCs tend to be shade adapted, low light requiring or at least low light tolerant species. Light influences plant growth directly because of its influence on photosynthesis. It has an indirect effect due to its influence on temperature, soil moisture, and humidity. For example, light affects forest cultivated mushrooms because even partial sunlight can cause heating and drying of substrate logs.
“Canopy cover” refers to the amount of the open sky blocked out by the leafy overstory of forest trees, as seen from below. It can be expressed most simply as percent canopy cover. Sophisticated hemispherical photography combined with computer image analysis can be used to accurately quantify canopy cover at different times of year. A rough visual estimate, however, is sufficient for most forest farming purposes.
Light Measurement Resources
Think of the adage, “warm air rises”, and the converse “cold air sinks”. In the outdoors this is particularly true at night and can have significant effects on the performance of forest farming crops especially if they are growing near the limits of their winter cold hardiness. As Carl Davies pointed out, a difference in elevation between a hill top and adjacent valley bottom of only a hundred feet or so can result in a nighttime temperature difference of 2.5 degrees F and a difference of more than 400 GDD over the course of a growing season. You can predict the existence of cold air pockets from a topographic map, but the best way is to walk your site frequently during all times of year.
Frost Pockets and Air Drainage Resources
1) A Guide to Agroforestry in British Columbia (Small Woodlands Program of British Colombia). Illustration developed by R. Terry and G. Chillinger. Published by the Society of Economic Paleontologist and Mineralogist in the Journal of Sedimentary Petrology 25(3): 229–234, September 1955.
The macroclimate and microclimate factors discussed in the previous section determine the above-ground environmental conditions that affect the performance of NTFCs. These factors also have profound effects on the below ground environment. Long term rainfall and temperature patterns affect the cycling of mineral nutrients and organic matter that are important components of the soil environment.
Unlike in conventional agricultural systems, it is not practical to intensively manage forest soils by plowing, cultivating, irrigating, fertilizing, or otherwise amending them. Nevertheless, understanding the soil characteristics and limitations on your forest site is important in the design of your forest farming system. Therefore evaluating the characteristics of your soils is a key component of the site assessment process.
Before conducting the various soil assessment exercises that we recommend, it is important to understand that soils are very complex associations of organic and inorganic components. They are not uniform from top to bottom. Soil scientists speak of soil horizons which are layers of differing “age” and composition. The figure below illustrates this concept. Keep in mind that horizonation varies considerably in different soil types.
Soil characteristics can help to predict crop performance, therefore it is useful to classify soils. The basis of soil classification is that environments that share comparable soil forming factors produce similar types of soil. The soil type at a given site is the long term consequence of all of the environmental factors, including geological ones, which have prevailed at that site. Knowing the soil type, therefore, gives us information about the above ground environment at the site as well as the substrate for plant growth.
Soils are classified by a taxonomic system, like plant taxonomy, based on relationships between soil types. Soil taxonomy has six hierarchical levels of classification as follows: orders, suborders, great groups, subgroups, families, and series.
Note the Workbook section on soils, p [13-15] . The remainder of Section 4.1 will help you complete p .
The MNG Case Study Site Assessment Workbook  provides example soil survey information.
Beginning early in the 20th Century, the US Soil Conservation Service (now the Natural Resource Conservation Service, NRCS) began an extensive process of classifying and characterizing agricultural and other soils throughout the US. According to the NRCS, a soil survey is a “detailed report on the soils of an area”. NRCS soil surveys are available in print from local NRCS offices, local conservation offices and other sources described in the Soil Survey Resource box, below. A NRCS soil survey consists of:
Surveys for your site may be available on the NRCS website  . If it is not, use the list of surveys by state to find out where you can obtain a print or CD version of the survey for your location  .
To use a published NRCS (SCS) soil survey (print or online):
Adapted from How to use Soil Surveys and Aerials Photos in Logging Operations, by Jim Ochterski, full text in resource box below.
Soil Survey Resources
Soil Survey Resources from Natural Resource Conservation Service (NRCS)
Soil Fertility refers to the level of mineral nutrients essential for plant growth and development, and the chemical characteristics that affect nutrient availability to plants. Those nutrients listed in the table below are the ones that are most often limiting to plants in agricultural and to a lesser extent to forestry land management systems. Although managing soil fertility by the application of inorganic fertilizers and/or organic matter are common agricultural practices, the use of fertilizers and nutrient management practices are far less common in forestry and forest farming applications. None the less, understanding soil fertility-related limitations on your forest farming site is an important aspect of selecting appropriate non-timber forest crops.
|Soil nutrient element||Avaialable (ionic) form||Soil pH and other chemical characteristics that affect nutrient ion availability (see Table below)|
|Nitrogen (N)||NH4+ (ammonium)
|NO3- readily leached; NH4+ retention increase on soils with high CEC (high organic matter, and/or high clay content)|
|Phosphorous (P)||H2PO4- or
|Unavailable (fixed) at low pH, and in clayey soils|
|Calcium (Ca)||Ca+2||More abundant in high pH soils|
|Iron (Fe)||Fe-2 (ferrous)
|Red soil color (uniform or mottling) indicates ferric (oxidized) Fe, and blue/green indicates ferrous (reduced) iron|
Although test kits for soil pH are available from garden centers, etc. complete soil chemical analysis is generally performed by a private, university or other soil analysis laboratory. Soil analysis usually includes levels of mineral nutrients (P, K, Ca, Mg, Zn, Fe, Al, Mn, and nitrate), pH and organic matter. Soil test kits can be obtained from the official testing laboratory in your state. It is important to follow instructions for collecting and submitting soil samples in order to obtain reliable results. Soil analysis reports include the results of the chemical analyses, often compared to a “normal” range for each nutrient. In some cases fertilizer recommendations are included if you have specified a particular crops with your application form. It is recommended that you should consult your local cooperative extension agent for complete interpretation of the results. Ultimately, because fertilizing forest soils is not often practiced, the most useful information you are likely to gain from soil analysis pH and OM content of your soil.
pH refers to the level of acidity or alkalinity of a soil based on the concentration of hydrogen ions (H+) in water, or
Chemically speaking, pH = -log [H+], where square brackets refer to concentration; thus [H+] = hydrogen ion concentration. When measuring pH, [H+] is in units of moles of H+ per liter of solution. pH 7 is defined as neutral
When referring to soils, pH values lower that 6 are generally referred to as “acidic” (sometimes called “sour”) soils, while pH values greater than 6 are considered neutral or alkaline ( basic) soils. Most plant species of interest in forest farming perform best in the pH range from 5-7, but a few are “acidophiles” (acid loving) such as blueberries which prefer pH in the range of 4-5. Although H+ ion (pH) is not a nutrient per se, soil pH has important effects on availability of soil nutrients, as illustrated in the figure below. The effects of pH on availability of Fe and Ca in particular are of greatest consequence for Forest Farming. As pH increases, the availability of Fe declines. In sensitive species this causes interveinal chlorosis (yellowing) (e.g. pin oak, silver maple). Availability of Ca on the other hand increases as soil pH increases from acidic to alkaline.
In field agricultural systems, the pH of acidic soils are often increased by addition of lime [Ca(CO3)2] and the pH of alkaline soils is sometimes deliberately decreased (acidified) by addition of acidic organic matter such as peat moss, or elemental sulfur (soil bacterial convert it to sulfuric acid). Deliberate alteration of soil pH is rarely practical in forest farming, but the ambient soil pH is worth knowing since it can affect your choice of non- timber forest crops. If your site is topographically variable (hilly) be sure to test pH in multiple locations since it can vary considerably between bottomland and upland soils.
OM is another important component of soil fertility and soil health. Although OM is not taken up directly and used by plants as a nutrient per se, it has important effects on soil fertility. Positively charged nutrient ions including the ammonium form of nitrogen (NH4+), potassium (K+), calcium (Ca+2), Magnesium (Mg+2) and others are attracted by the abundant negative electrical charges on the surface of OM particles (especially humus), and prevented from being leached away as water moves through the soil profile. Organic matter also has an important role to play in maintaining the structure and tilth of soils.
Soil Fertility Testing (Nutrient Analysis) Resources
Soil fertility, pH and organic matter are especially important attributes of soils for forest farming. Other soil properties that make a difference in the performance of crops include:
Information about each of these factors and how they are evaluated is available in the Additional Soil Analysis Resources box, below. Among them, soil texture and drainage are particularly useful indicators of plant performance
The Soils section of the Site Assessment Workbook provides a table for; pH, Organic Mater, Mineral Analysis, Depth, Texture, Moisture, Drainage and Compaction for several of your zones. Look at the table and take notes as you work through this section. Also note examples in the MNG Case Study Site Assessment Worksheet, Soils
Soil texture refers to the relative portions of different particle sizes that make up soil, including sand (large), silt (medium) and clay (fine). The mixture and distribution of these 3 size classes determines important properties like drainage and water holding capacity, and affects fertility. Soil texture classes include: sand, loamy sands, sandy loams, loam, silt loam, silt, sandy clay loam, clay loam, silty clay loam, sandy clay, silty clay, and clay. These categories are named based on % content of silt, sand and clay as shown below in the “classic” soil texture triangle.
As clay (and/or organic matter) content increases, soils have higher cation-exchange capacity (they retard the loss of cationic nutrients including nitrogen in the ammonium (NH3+) form), and higher levels of calcium, (Ca+2), magnesium (Mg+2), and potassium (K+). An extremely important consequence of soil texture is its effect on the amount of water that is available to plants. The range of soil drying is from full saturation (field capacity) to the “permanent wilting point” (death due to drought stress). Soils that are sandy have less water available for plants than silty soils, and silty soils have less available water than clayey soils. This relationship is shown in the figure below where the greater the distance between the lines for field capacity and permanent wilting point, the greater the amount of water available to plants. Clearly a silt loam, and to a lesser extent more clayey soils, have more available water than sandy or loamy soils with lower clay content.Use the Soil Texture Resources in the box below to determine soil texture for your sampling points:
Soil Texture Resources
Water is one of the most import soil-related resources necessary for plant growth and development. Soils affect and are affected by the movement of water in the following three ways:
A percolation test described below is one way to assess drainage. For the most reproducible and meaningful results it should be performed after soil has been pre-wetted. A drawback to the percolation test is that it usually takes many hours to perform, and the results depend on how deep the hole is dug, as subsurface water flow (percolation) may differ among different soil horizons in the same soil profile. Consequently, interpreting the results may be complicated.
Alternatively soil color, especially mottling may be used as an indirect indicator of soil drainage. This is because the upper portion of a soil profile that is well drained will rarely be saturated for long, and will remain well oxygenated most of the time. On the other hand, a poorly drained soil will go through repeated cycles of wetting to the point of saturation for prolonged periods of time followed by periods of drying, as the saturated water table moves up and down. This repeated cycle of raising and lowering of the upper margin of a perched subsurface water table, over a long period, will cause localized zones of red oxidized iron (insoluable) and/or blue/green reduced (soluable) iron (“leopard spots”) described as mottling, as shown in the photograph below.
If the zone of mottling is found near the soil surface it can be assumed that the surface layer is poorly drained and frequently saturated with water. If the zone of mottling is deeper, this indicates a well drained surface layer, which is rarely if ever completely saturated. Soil scientists have used depth-of-mottling zone as a means of dividing soils into different drainage classes as shown in the figure below.
Soil Drainage Resources
Additional Soil Assessment Resources
A vegetation inventory is an estimation of plant biodiversity within a defined area. Determining what mixture of trees, shrubs, and non-woody species already grow on your forest property will assist you in the process of site design and planning in two ways:
One of the most important issues related to conducting a non-timber forest inventory is the question of how thorough it should be. Should you take a complete census of each tree and non- woody plant that occurs in your forest? If you have more than an acre or two of forest that would be impossible, or at least impractical. If you are not going to include every plant in your inventory then how should you choose which to include?
The best approach is to intensively and thoroughly sample one or more smaller areas (plots) of uniform size that are typical of the biodiversity on your entire site. Most likely your site is not uniform in terms of elevation, aspect, soil type, vegetation community, etc.. Therefore you should sample one or more representative plots from each different ecological niche within your heterogeneous forest. This sampling strategy can be “seat of the pants” – what seems to you to be representative of the whole or some subdivision. Or, it can involve a systematic, randomized plot selection methodology. The former may involve simply recording what you already know about vegetation types and associations on your land, especially if it is relatively small and you know it well. The latter is particularly well suited for large blocks of forested land that have a great deal of plant variation and a wide range of slopes, elevations, aspects, and microclimates.
Beginning to identify and inventory the plants on your property can be a daunting task if you’re not familiar with the local species and haven’t used botanical guides. This section should help you get started. It is not necessary to identify every plant at your sampling points. The aim of sampling is to learn more about site characteristics as can be deduced from what is already growing there.
To help you get started identifying plants, photos and descriptions of common trees, shrubs and herbaceous plants have been compiled in the [ HWWFF Plant Photo Catalog]. This resource was originally developed for ginseng site assessment, but it applies to other crops as well. Not every species in the catalog will inform your crop selection, but it should expedite your site knowledge.
Additional Web Resources
There are many other web resources for tree id. A few highly recommended sources are:
Printed Botanical Guides
The following are recommended for beginner to intermediate users in New York and Pennsylvania:
Intermediate Botanical Guides
This HWWFF site provides two tools to help you select crops that will fit characteristics of your site that have been determined by conducting your Site Assessment. These are the [Crop Matrix Tool] and the [Crop Filter Tool]. You may access these tools through links in this section, or the Tool Tab of the HWWFF Resource Center homepage.
The [Crop Matrix Tool] identifies possible forest farming crops for the Northeastern US, and allows you to view the characteristics of each crop. This tool is especially useful if you have certain crops in mind for your site. You can view their characteristics and site requirements to determine if it is an appropriate match for your site.
For example, you may have an idea that you would like to grow raspberries in your forest. To learn something about the plant, its site requirements and what would be involved in cultivating it, click on the [Crop Matrix Tool] and scroll down the alphabetical list of plants. You will find three types of raspberry listed; black, purple and red. Click on each, then read and take notes so you can compare and choose.
Another way to use the matrix is to click on [Show List of all Available Crops]. The first category of crops is Fruits, and under fruits is a sub-category, Brambles. The three types of raspberry are listed there. You can also see two other types of brambles listed, which may stimulate your curiosity, so click on them and have a look at their characteristics and requirements as well. And so on, explore any other crops of interest in the same way.
The [Crop Filter Tool] allows you to choose a specific characteristic and see what the value of that characteristic is for each possible crop. This is useful if you have a limiting factor on your site, such as a very high or low soil pH. You can easily see which crops can tolerate your soil pH and filter out any crops that are not applicable. The information that these tools offer is based on scientific literature on plant species that the scientists, educators and practitioners who have contributed to developing the HWWFF curriculum believe could be grown as forest crops.
HWWFF Crop Selection Tools
By now you have undergone a detailed process of site evaluation and crop selection. As discussed in the previous section we know only enough about the site preferences for non timber forest crops to make educated guesses about what should to grow where. The “what” is the process of crop selection and the “where” is the process of site design. “What goes where” implies that they are closely interrelated processes. Both depend on the site assessment process you have conducted.
Recall that our approach to site assessment has been to guide you through the development of two different kinds of maps:
The base map where you recorded current land uses, land forms (topography) and features (roads, streams, etc.)
The site assessment map and workbook where you have recorded site characteristics (soils, climate, vegetation, etc.) that will affect your choice of crops. We anticipate that by now you have given some thought to what crops are appropriate for your site considering the advantages and limitations found there. And so it is time for design, i.e what goes where?
Once again we encourage you to take a map-based approach. Refer to your site assessment maps to locate areas on your base map that appear to indicate the fewest constraints, and are therefore most conducive for growing the crops of your choice.
Along the way your goal will be to “tame” or synthesize all the information you have accumulated into a spatial map representing your vision for the site.
Page 30 of the MacDaniels Nut Grove Case Study shows a [design map] created in 2003. Today, many of the crops that we envisioned are more or less in the locations as you see them on that map, but some of the crops have been evaluated and ruled out or repositioned and new crops have been added. Crop selection and design are ongoing and dynamic. The design map is a way to begin.
Keep in mind that when you are designing a forest farming system, the key elements of this and any agroforestry system are:
HWWFF Design Resources