Silviculture Upland Hardwood


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General information on growing hardwood forests, with an emphasis on the oaks.

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Silviculture Upland Hardwood

  1. 1. silviculture tim berland associates UPLAND HARDW OOD Upland hardwood (UH), in this Plan, refers to those species that occupy m inor stream bottom s, upland drainages, side slopes and ridge tops. These sites represent two different m oisture gradients - Xeric and Mesic. Trees occurring on xeric (dry) sites include: Post, Scarlet, Southern Red, Black and W hite Oak; Pignut and Red Hickory; Black Gum ; Red (Slippery) Elm ; and Shortleaf Pine. Trees occurring on m esic sites (m oist or north and east slopes) include: Black, W hite, Southern Red, Northern Red, and W ater Oak; Bitternut, Shagbark and Mockernut Hickory; Yellow Poplar; Sweet Gum ; Red and Sugar Maple; Black Cherry; Red (Slippery) and Am erican Elm ; Am erican Beech; Black Gum ; W alnut and Sycam ore. Associated sm all trees, shrubs and herbaceous plants include: Eastern Hophornbeam ; Flowering Dogwood; Sourwood; W inged Elm ; Blackjack and Bluejack Oak; Beaked Hazlenut; Bluebeech; Huckleberry; Red Bud; Blackberry and Dewberry; Hawthorne; Mayapple; False Solom ons Seal; Fire Pink; Trillium s; Dwarf Crested Iris; Brom esage and other native warm season grasses (NW SG’s); Virginia Creeper; Sm ilax sp; W ild Grapes; Cinnam on, Maiden Hair and Braken Fern; and Ebony Spleenwort. The above list is not all inclusive. A m ore com plete listing is included in the Appendix, along with their scientific nam es. Most of the desirable upland species, both for wildlife and tim ber production, are intolerant to interm ediate in their tolerance of shade (Burns and Honkala 1990b). Any cutting system prescribed m ust allow 25 to 50 percent of full sunlight to reach the forest floor in order for oak to becom e established and grow adequately (Kram er and Decker 1944, Hodges 1987, Crow 1988, Hodges and Gardiner 1993, Gardiner 2002). However, attem pts to obtain the correct am ount of sunlight for oak establishm ent also allows faster growing com petitors to becom e early dom inants. Once over-topped, the oaks never recover (Loftis 1970 1982 1988 1990a, Oliver 1976, Kittredge 1988, Shostak and others 2002). This situation is quite prevalent on m esic (m oist) sites, but not on xeric (dry) sites. Therefore, the cutting system s discussed will differentiate between xeric and m esic sites. Oaks are particularly difficult to regenerate on m esic sites due to the types and abundance of their com petitors (Beck 1970, Sm ith and Linnartz 1980, Sanders and others 1983, Graney 1989, Loftis 1989 1990a, Abram s 1992, Van Lear and W att 1993). The m ain com petition to oaks for sunlight, nutrients and water are the fast growing intolerants such as Yellow Poplar, Black Cherry and Elm , along with stum p sprouts (or root suckers) from tolerant species such as Black Gum , Eastern Hophornbeam , Flowering Dogwood and Red Maple. Oaks spend the first ~3 to ~ 5 years developing their root system and increasing their root collar diam eter (Aust and others 1985, Nix 1989, Nix and Lafaye 1993), whereas Yellow Poplar and Black Cherry, their m ain com petitors, begin im m ediate height growth. This enables the oaks to survive and grow in dry (xeric) conditions (Crow 1988,Johnson and others 2002) while their com petitors languish. On m esic sites where m oisture is not a lim iting factor, this delay in height growth puts the oaks at a com petitive disadvantage to Poplar and Cherry. Because of this trait in oaks, it is im portant to have large advance oak regeneration before the overstory is com pletely rem oved in a harvest cut. Methods have been developed for evaluating the adequacy of this regeneration (Beck 1970, Johnson 1977, Sander and others 1984, W aldrop and others 1986, Lowell and others 1987, Johnson and Sander 1988, Loftis 1988 1989 1990a 2004, Marquis and others 1992, Sm ith 1993) and , on m esic sites, there should be from ~400 to ~700 seedlings per acre that are greater than 3 feet in height. Loftis (1989 2004) and Schweitzer and others (2004) added an index to evaluate the types (stum p sprout or seedling) and kinds (Poplar, Cherry, vines) of com petition, which is very im portant to the success in establishing dom inant and codom inant oaks in the next stand (Kitteredge 1988). Page -40-
  2. 2. silviculture tim berland associates The Clearcut (Sm ith 1986, Beck 1988) system can be appropriate for dry sites where Owner objectives are to m anage the natural hardwoods (m ost often these sites are converted to Loblolly Pine for econom ic reasons). The understory should be evaluated for potential problem s (high num bers of shrubs) before harvest, and treated with a forestry herbicide (Arsenal®, Garlon®, Velpar®) as necessary. Fire can also be used to prom ote oak establishm ent and growth (Brown 1960, Brose and Van Lear 1999 2004, Brose and others 1999a 1999b), due to their large deep root collar which m akes them less susceptible to fire than either Yellow Poplar, Black Cherry or Red Maple. The clearcut system is not appropriate for regenerating oak on m esic sites (unless there are adequate num bers of large advance regeneration), as previously noted. The disadvantage to the clearcut system is m ainly aesthetic because it does not “look good”. W ildlife, however, do not seem to m ind. In fact, m any of the neotropical m igratory songbirds (Indigo Bunting, Goldfinch, Rufous-sided Towhee), whose populations have been declining, actually prefer this type of early successional habitat. A traditional Shelterw ood or a Shelterw ood w ith Reserves (Tw o-aged)(Sm ith 1986, Miller and others 1995, Stringer 1998) system is well suited for the establishm ent and growth of oak (Loftis 1990b, Graney 1999). These system s rem ove the overstory in increm ents by em ploying one or two partial cuts. Evaluating the m idstory and understory is the critical first step. Rem oving the understory (with forestry herbicides by individual stem injection) m ay be necessary (Loftis 1978, Janzen and Hodges 1985, Graney 1989, Graney and Murphy 1995). If there are few oak seedlings present, or they are of insufficient size, the first cutting should leave a residual basal area per acre of ~80 sq ft, with all Yellow Poplar being rem oved in the preparatory cut (to reduce the seed source). As the num bers of advance oak regeneration increase, m ore of the stand can be rem oved in subsequent cuts. Once the new seedlings reach 3 feet in height, or m ore, (and com petition is not severe), the rem aining overstory can be harvested. If a Two-aged system is being im plem ented, ~20 sq ft of basal area per acre should be left uncut, with these residuals being selected either for their ability to increase in value, for their value as wildlife habitat or for their aesthetic value. These system s can be used on xeric and m esic sites (Johnson and others 1989). The disadvantages to a shelterwood system are: allowing the proper am ount of sunlight to reach the forest floor in the initial cutting (enough to allow establishm ent of oak, but not Yellow Poplar); the proper tim ing of the final cut to release the oak reproduction; and the need to enter the stand m ultiple tim es which can dam age sm all reproduction of the desirable oak seedlings and saplings. The Group Selection (Sm ith 1986) system has lim ited use in oak regeneration. Norm ally, sm all openings that range from 0.5 acres to 2.0 acres are m ade in the stand. However, openings as sm all as 0.2 acres have resulted in the sam e type of stand structure as m uch larger clearcuts (Della-Bianca and Beck 1985, Beck 1988). Rem oval of the understory, m idstory and Yellow Poplar m ay prove m ore successful. This system creates the m ost com plex stand structure and species diversity. It is applicable to xeric sites and, if proper steps are taken, to m esic sites as well. The Single Tree Selection system is not appropriate on either site (Della-Bianca and Beck 1985). The disadvantages of the Group Selection system are: the need to enter the stand m ultiple tim es; obtaining sufficient num bers and sizes of oak regeneration; and the difficulty of m anaging m any sm all scattered areas. After a tim ber harvest or other disturbance (wind, fire), the stand progresses through five distinct stages of growth and developm ent (Oliver 1981, Johnson and others 2002): stand initiation; stem exclusion; understory reinitiation; com plex stage; and m ixed stage. Managed stands on private lands rarely reach the com plex or m ixed stage, so they will not be considered here. The stand initiation stage is characterized by a rapid increase in the num ber of trees (stum p sprouts and seedlings) and a rapid increase in the herbaceous plant cover. Thinning sprout clum ps of desirable species to a single stem at ~yr 3 to ~yr 5 can increase their diam eter growth by 30 to 60 percent (Johnson Page -41-
  3. 3. silviculture tim berland associates and Rogers 1984, Johnson and others 2002, Naka and Cannon 2004). Other silvicultural activities are not recom m ended at this tim e, due to the rapid growth of all stem s (Shifley 2004). However, one study of thinning and fertilizing in a yr 7 stand showed a 16 percent increase in diam eter growth at yr 10, with annual growth of 179 cubic feet per acre per year (versus 89 cubic feet per acre per year in the untreated control stand)(Newton and others 2002). During stem exclusion, num bers of trees per acre are quickly decreasing as the canopy closes and intolerants are succum bing to the shade (and com petition from roots and lim bs of neighboring trees). The stand develops an overstory, m idstory and understory. It is at this tim e that a thinning or im provem ent cut can help m aintain the num ber of oaks in the stand and thereby increase their percent of total stocking at final harvest. Precom m ercial thinning at ~yr 15 can increase diam eters by 2 inches and heights by 5 feet over unthinned stands after 7 years (Blackburn and others 1999, Meadows and Goelz 1999), with this difference still m easurable at yr 30. Tim ely thinnings can also double the volum e of usable wood by final harvest (Gingrich 1971, Clatterbuck 2002, Shifley 2004) over that of unthinned stands. Recom m ended m inim um residual stocking levels necessary to m aintain satisfactory stand growth and insure full occupancy of the site are 46 to 65 percent in upland oaks (Schnur 1937, Gingrich 1971, Hilt 1979). Thinnings and Im provem ent cuts are designed to m anipulate species com position, stocking, form and quality of the residual stand. Trees are considered either crop trees, growing stock, reserve growing stock or cull, as described below. -Crop Trees - potential sawtim ber trees of the desirable species (as defined by Owner objectives) that are of good form and quality, and in the dom inant or codom inant crown class (Sonderm an and Rast 1988, Meadows 1995, Meadows and Goelz 1999). Trees to favor as crop trees (ranked from m ost desirable to least desirable) are: Northern Red, W hite, Black and Southern Red Oak; Shagbark Hickory; Shortleaf Pine; Yellow Poplar; and Sweet Gum . -Growing Stock Trees - potential sawtim ber trees not necessarily of the desired species, but of good form and quality. These are chosen so as not to reduce stand density below ~50 to ~55 percent of full stocking (Schnur 1937, Gingrich 1971, Newton and others 2002). -Reserve Growing Stock Trees - are capable of becom ing sawtim ber or pulpwood when retained until the expected final harvest. They m ay be in the codom inant or interm ediate crown class. Sawtim ber potential is preferred over pulpwood, regardless of the species desirability. These are retained only to m eet stocking guidelines or m aintain uniform spacing between trees. -Cull Trees (Cutting Stock Trees) - these are in the interm ediate and suppressed crown classes, and of poor form and quality. There is no econom ic reason for their retention and they should be the first trees rem oved from the stand. If these culls are old standards left from a previous disturbance (tim ber harvest, wind, fire), they m ay be retained for wildlife purposes (nesting and roosting sites for turkey, owls, woodpeckers, and bats; or den sites for squirrels, racoons, and black bears) if they do not occupy needed growing space (Kellison and others 2002). Thinnings and Im provem ent cuts are two of the m ost cost effective silvicultural practices that can be applied to forest stands. Regardless of the am ount of stum page received (or lack thereof), by concentrating annual growth on the best and m ost desirable stem s, the stand value nearly doubles im m ediately (Sonderm an 1984, Kochenderfer and others 2001)(see also Forest Management section). And, although the recruitm ent of new oak seedlings is not a stated objective of these cuttings (perhaps it should be), som e reproduction will alm ost certainly becom e established on the area. This advance oak regeneration should be encouraged and nurtured whenever and wherever possible (Hodges 1987, Lockhart and others 2004). In the understory reinitiation stage the dom inants and codom inants can be considered m ature sawtim ber trees. As natural m ortality occurs there are gaps created in the canopy which allows increasing light levels to the forest floor. There is a greater diversity of shrubs and herbaceous cover, and the tolerant Page -42-
  4. 4. silviculture tim berland associates species are able to expand their crowns. In m anaged stands, this is when planning for advance oak regeneration (and the next stand) begins. Forestry herbicides can be used to reduce (it is im possible to elim inate) the num bers of undesirable species (as defined by Owner objectives) in the subcanopy. Fire could also be used to reduce undesirables and prom ote large advanced oak regeneration (Van Lear and W att 1993, Brose and Van Lear 1998, Sykes 1999, Brose and others 2001). Oaks as a group are considered a keystone species (Meffe and Carroll 1991, Fralish 2004), which is the reason m ost of the silvics discussed concerns their growth and developm ent. In addition to being of greater econom ic value than “m ixed wood”, their acorns are a food source for som e 44 different anim als and birds. However, they can be difficult to regenerate following a harvest, as described above. Because of that difficulty, it is critical to inventory the upland stand (including the understory, m idstory, overstory and vegetative cover on the forest floor) ~5 to ~10 years before any harvest. This will reveal any deficiencies in advance oak regeneration or other areas that m ight need attention. Copyright © 2009. Tom Busch, timberland associates. Contact us at 662 791-9443 or e-mail to Page -43-