t site preparation effects on coastal plain sites: a … · preparation on disturbed soils....

Wet-Weather T ber Harvesting and Site Preparation Effects on

Coastal Plain Sites: A Review

Masato hliwa, Forest Hydrologist, International Paper Company, 719 Southland Road, Bainbridge, GA 31 717; W. Michael Aust, and James A. Burger, Department of Forestry (0324), 228 Cheatham Hall Virginia Tech, Blachburg, VA 24061; Steve C. Patterson, Forest Soil Scientist, Meamesh-laco, Forest Science Laboratory, Box W, 180 Westvaco Road, Summerville, SC 29483; and I3&iIy A. Carter, Soil Scientist, USDA Forest Service, Engineering Research Unit, 520 Devall Drive, Auburn, A..L 36849.

ABSTRACT: Increased interest in sustainable forestry has intenszjied the need for information on the interactions of forest soiZs, harvesting methods, site disturbances, and the eJgicaey of methods for amelio- rating disturbances. On wet pine flats, such as those commonly found in the Atlantic and Gulf Coastal Plains, conditiom such as frequent rairlfall, low relief, and poor internal soil drainage ofien predispose forest soils to harvest disturbances and potential damage. Typical forest operations use heuvy logging equipment, such as rubber-tired feller-bunchers and skidders. During dry soil conditions, these machines cause little soil disturbance, but under moist to saturated conditions, such operations nay compact soii3 and interfere with nonnal soil drainage. Many studies have been conducted to characterize soil disturbance and site preparation eflects on tree seedling survival and growth and to evaluate the amelioration effect of site preparation on disturbed soils. However, results are sometimes contradictory due to site specificity, and results have nut been summarized in the context of pine plantation management. This article summarizes previous research results of the wet-weather harvesting and bedding effects on soil properties as related to loblolly pine (Pulw taeda) productivity for a variety of Coastal PZain region sites types. South. J. Appl. For. 28(3):137-151.

Key Words: Timber harvesting impacts, site productivity, site preparation.

T h e majority of large wood-using facilities in the southeastern United States can feasibly maintain less than a %-week supply of wood. Within the Coastal Plain region, wet periods commonly occur for 3-6 months of the year. The wood supply and wet season combination ensures that some degree of wet-weather harvesting will occur during most years in the Coastal Plain. Fbthermore, modern forest harvesting operations use large machinery because of the efficient operability and economic feasibility. Traffic from these machines may cause locdtized and sometimes exten- sive soil disturbances such as soil compaction, shallow and deep rutting, puddlinglsme~g, and churning, particularly if operations are conducted during moist to saturated soil conditions (Pearson and Marsh 1935, Youngberg 1959, Hatchell et al. 1970, Mwhring and Rawb 1970, Davies et

Hare: W. Michael Aust can be reached at (540) 23 1-4523; Fax: (540) 231-3330; waust@vtedu. Copyright O 2004 by the Society of .Axncrim Foresters.

al. 1973, Greaten and Sands 1980, Hillel 1982, Gent et aI. 1983, 1984, Pritchett and Fisher 1987, Burger et al. 1989, Awt et al. 1993, 1995, Marshall et al. 1996). Such soil disturbances have been associated with increased bulk den- sities, lower organic matter levels, reduced air and water movement, and altered nutrient availability ("Youngberg 1959, Moehring and Rawls 1970, Gent et al. 1983, 1984, Aust et al. 1995). Additionally, research shows that these soil disturbances can decrease seedling survival and growth of commercially important plantation species such as Dou- glas-& (Pseudotsuga mew'esii (Mirb.) France) in the northwestern United States (Youngberg 1959) and loblolly pine (Pinus taeda L.) in the southeastern United States (Hatchelf et al. 1970). These results have led to concerns about how harvest disturbances may affect long-tkm. site productivity and to speculation about how such disturbances. could be ameliorated via natural or artificial means.

A wide variety of smdies have been conducted to characterize the soil disturbance and site p r e p d o n effects on

soil properties and on tree seedling survival and growth Ovfay et af. 1973, Terry and Hughes 1975, McKee and Hatchell 1986, Aust et al. 1995, Ke1tirig et al. 1999). How- ever, these results are generally site-specific, often of lim- ited duration, and have not k n s m of pine plantation management.

The objective of tbis article is to briefly review and sumraarize research results of wet-weather harvesting and bedding effects on soil properties and site prodtuctivity. The review concentrates on describing forest soil disturbance mechanisms and providing background of forest soil disturbance and the effect on forest productivity. The review also examines the amelioration effect of site preparation on.soil properties and the evidence for improved tree growth and nattxal soil recovery processes of intensively managed pine plantations in the southeastem United States, a~thou~h'less information is available for these topics. These review top ics are discussed, but also presented in tabular form, to provide a succinct some of liteiature for land managers and researchers.

Forest Soil Disturbance Mechanisms Mechanisms of Soil Compaction on Dry to Moist Soils

Tires on machines apply a compressive force to the soil's surface, which is a combination of nomd force and shear force (Davies et al. 1973, Greiicen and Sands 1980, Hillel 1982). Level of disturbance is a function of the equipment weight, driving system, traveling speed, traffic frequency, soil organic matter content, soil texture, and soil water content. Typically, the severest disturbance is produced by heavy equipment with small surface traction, such as a heavy tractor with narrow, sd-diameter, high-pressure tires, m h g multiple passes on the same area. Wet, loamy to chyey soils with low organic matter content are conditions under which a tractor of this type would cause severe soil disturbance. This section summarizes the effects of soil compaction and disturbance processes on soil physical properties. More detailed explanations of soil compaction are provided by Soehne (1958), Harris (1971)' Cohron (197f), Creacen and Sands (1980), and Hillel (1982), and severe soil disturbance is described in detail by Aust and Lea (1992).

A normal force, which is also called a static force, is a downward directional pressure that is produced by gravita- tional acceleration acting on a mass. The vertical stress is distributed in a soil in a vertically elongated radial direction, and the greater the force the deeper will be its effects. Therefore, decreasing the weight per unit area reduces the soil stress. Reduced weight per anit area can be achieved by decreasing loads (Soehne 19581, inamsing the track-soil. contact area (Reaves and Cooper 1960), and reducing tire inflation pressure (Vanden Berg and Gill 1962).

Soil shearing stress is a madirectional force that is produced by tire lugs, wheel rotation, and vibration (Hillel 1982). The tire-soil contact face is usually not a flat plain because of tire lugs. Tire lugs apply concentrated, downward pressure directly under the flat top of the lug and less

concentrated angled forces from the sides of the lugs. This produces uneven stresses on the soil (Trabbic et al. 1959, W e 1 1982). The wheel. rotation causes circular movernett of surface soil (Yong and Osler 1966). 'When a wheel moves forward, soil just in front of the wheel is pushed forward and upwad As the wheel rotates, this so2 is pressed downward. Then, as the wheel moves across the soil, the compressed soil is pushed backward. Vibration produced by equipment b& contacts between soil particles and reorganizes them into more compacted structures. This process is especially common in dry to slightly moist soils (H;ueI 1982).

Soil compaction occurs when the compressive force ei- ceeds the soil resistance force among the soil particles (H& 1971, Greacen and Sands 1980, Hillel 1982). The ability of a soil to resist compressive forces is a function of soil texture, soil organic matter content, and soil water content. Soil water content is the most widely fluctuating variable, and its fkquent variations cause soil compaction and rutting to be common phenomena Burger (1994) de- tennined the trafficability hazard index for the A horizon of typical wet pine flat soils (Typic Ochraqualfs) based on the volumetric soil moisture content and showed that the m a - imum soil strengh widely varied depending on soil water content. For instance, soils with 19% water content could withstand approximately 2,230 kPa of adjusted equipment ground presslue, but soils with 28% water content could only withstand approximately 1,115 kPa ground pressure (i.e., adjusted equipment ground pressure of a medium sized skidder (10,000 kg) with 58-cm wide tire ranges fkom 1,115 to 2,230 kPa).

Soil water commonly exists as a thin wata film around soil particles, aggregates, and connecting structures, such as clay bridges. When soil is dry, soil compaction is caused by the collapse of larger pores, but most aggregates do not change their shape because intra-aggregate resistance forces are usually larger than %hose of inter-aggregate forces. As soil moisture content increases, water f* gradually cover the entire soil particle, and the thickness of the water film increases (diffuse double-layer expansion). This water h weakens the soil structure and decreases frictiondl forces between the soil particles. Therefore, moist soil aggregates are more susceptible to deformation, and the soil is more easily compacted, especially when soil water content is between the plastic and liquid firnits (Greaten and Sands 1980, IIillel 1982). Consequently, moist soil compaction reduces soil porosity and increases bulk density more than dry soil compaction.

Mechanislns of Soit Smearing (Puddling) and C h d g for Moist to Wet Soils

'Wheel slip also causes smearing on the soil surface and causes additional soil compaction (Davies et al. 1973). Wheel slipping is traosfomed as shear forces on a moist to wet soil, which deform and reorients soil particles and forms horizontal platy structures, a process commonly re- f e d to as puddling. Soil disturbances produced by the

138 SJAF 28(3) 2004

combination of static stresses and dynamic shear forces on moist to wet soils generally achieve higher levels of compaction than is caused by the static stresses alone on dryer soils eodrnan and Rubin 1948). Davies et aI. (1973) reported that increases in wheel slippage subsequently resulted in higher shear strengths, soil compaction, and higher bulk density values. Higher bulk density values also were associated with lower porosity arid water permeability and higher soil mecWcal resistance and moisture content.

Under complete or near soil saturation, soil compaction levels may actually decrease, although soil churning usually increases (Soehne 1958). m e n the soil water content ex- ceeds the liquid limit, actual soil compaction decreases because the water-fi.lled soil pores are not compressible (Aust and Lea 1992). Under this condition, traffic-induced shearing stresses reorganize soil structures. The reorganization usually causes clay-polyphte slippage, soil-particle- bound breakage, and abrades colloidal coating materials Erorn sand grains (Koenigs 1963). Multi-directional force produced by tires on large equipment moves large soil particles and flocculates fine soil particles in excess soil water. Soil rutting, churning, and plastic mud are the result of heavy machines operating on the hydrated soils.

Localized severe soil disturbance may also alter site hydrology. Aust et al. (1993) observed localized high water tables and an alteration of site hydrology following wet- weather harvesting on a gently sloping wet pine flat forest in eastern South Carolina. They found that severe soil disturbance on primary skid trails increased bulk density and decreased macro-porosity and saturated hydraulic conductivity, which increased soil saturation in the affected areas. Additionally, the altered soil physical properties and rough soil surfaces caused by wet-weather harvesting restricted s d a c e and subsurface water flow. This further indicates that a detailed investigation of localized severe soil disturbance is critically important to evaluate site hydrology and long-term forest productivity.

Early Observations Regarding Harvest Disturbances Early awareness of forest soil disturbance was raised in

the northwestern United States in the late 1930s when heavy equipment became commonly used for forest harvesting (Table 1). Pearson and Marsh (1935) recognized that trarn- plhg by livestock and logging operations by steam skidders and tractors on clay-textured soils under wet conditions reduced soil water and air permeability and created adverse soil conditions for ponderosa p i . (P. ponderosa Dougl. ex Laws.) seedling root growth. Steinbrenner and Cessel (1955) compared soil physical properties of tractor roads and undismbed areas in. southwestern Washington and found that bulk density was 15% higher, macroporosity was 53% lower, and soil permeability was 93% lower in the tractor road. Lull (1959) concluded in a soil compaction review article that compaction decreased soil hydraulic properties, and the subsequent infiltration decrease increased suface mof f and erosion.

Crawler Tractor-Induced Soil Disturbance Effects on Seedkg Growth

Disturbance effects of crawler tractors on forest so2s and the relatioDship with decreased tree growth or seedling survival were described in various reports published during the tbree-decade period between 1950 and 1980 (Tables 1 and 2). Youngberg (1959) reported that significant increases in soil bulk density and decreases of organic matter content in the surface soil (0-30 cm) on crawler tractor roads reduced soil aeration and created a nitrogen deficiency. Although subsequent survival of Douglas-fx seedlings was not affected, seedling height growth was significantly loaer within the crawler tractor trails.

Similar relationships were found in eastern pine forests. Moehring and Rawls (1970) found that wet-weather thin- ning operations in the CoastaI Plain of Arkansas increased bulk density from 1.24 Mg mW3 to 1.4 Mg m-3 (13% increase), and Hatchell et al. (1970) found that primary skid trails and log decks in the low-lying, wet, Coastal Plain soils had signdicantly altered soil physical properties (increased bulk density and soil strength, and decreased infiltration rate and porosity). Furthermore, Perry (1964) found that water infiltration in 26-year-old ruts in the North Carolina Pied- mont was significantly lower than that of undisturbed soils. These disturbed soil properties decreased tree height and diameter growth.

Simmons and EzeU. (1983) also evaluated the effect of tractor passes on the physical properties of different soil texture classes and subsequent loblolly pine seedling survival and growth responses. They found that surface soil bulk density increased about 10% after the k t tractor pass, but the second pass only increased the bulk density an additional 1%. Seedling survival in a sandy loam soil that was compacted by one-pass was 100%, and root growth in the soil was promoted; apparently the compaction of sandy loam soil increased soil water retention capacity. However, seedling response on a 'sandy loam soil that was compacted by two passes, and a loamy sand soil that was compacted by one and two passes, decreased seedling survival md root growth. These results clearly showed that soil compaction of fmer textured soils by a crawler tfactor during wet conditions decreased seedling survival and growth.

Rubber-Tired Skidder-Induced Soil Disturbance Effects on See- Survival and Growth

fn the 1960s, rubber-tired skidders began replacing crawler tractors in logging operations because of their su- perior maneuverability, speed, and economics (Stenzel et d. 1985). This shifted the focus of soil disturbances from crawler tractors to rubber-tired skidders. Contact pressure (normal static pressure) of rubber-tired skidders is generally higher than that of crawler tractors w a u s e crawler tractors have larger soil contact areas (Greacen and Sqds 1980). Therefore, rubber-tired skidders potentially create greater soil disturbances. Lockaby and Vidrine (1984) evaluated different disturbance levels of northeastern Louisiana fine loamy soils (undisturbed, primary and secondary skid trails,

SJAF 28(3) 2004 139

'F"aBfs 7 , Summary af wet- and dywesa~er timber" b-rssvasting EREG~S on wlE prapsejes, --a&, , ---A- ----".La

S h S W t V p e Soil yl

General G e n d Soil disturbance reduced water and air perm&ility.

Eastern Oregon and Ponderosa pine W e l l - w & 26% of the total area W*gton Basaltic origin, was disturbed by

clayey soils; tractor logging, of pumice origin, which 58% was coarse loamy deeply distuibed. sand soils; and Cable and horse gl-aniites origin, logging d&twbed 30 loams to sandy and 1796, loa~ns respectively, of which

2% was deeply disturbed.

Wet-weather tractor Cascade Mountains 'Old-growth Sedbentay shale Soil property change logging: deep (southwestern Douglas-fu and sandstone between control and soil Washington) origin, silty clay cutover site was displacement, loam; basalt small. Significant compaction, and origin, silty clay aecmm of ~ud*g to clay loam; permeability and

and pumice macroporosity and origin, clay increase of bulk soils density in skid roads.

26% of area was disturbed by skidding,

Tractor logging: Cascade Mountains Old-growth Reddish-brown On tractor road, b& deep distlxbance (we~tem Oregon) Douglas-fir Oxisols, well- density was increased,

aggregattxl, and aeration, organic friable clayey matter, and nitrogen surface soil on level were decreased. basalts

Rutting: in and out Piedmont (central Loblolly pine Clayey B horizon, 26 yr after the soit ruts North Carolina) plantation typical upland disturbance, water

Piedmont so2 infiltration rate in ruts was signifimtly lower than out of ruts.

Wet- and dry- Coastal PIain 4- even- Poorly drained silt Dry soils were not weatherthinning (southeastern aged lobfolly ham loess soils affected by the by crawler Arkansas) pine with fragipan at operation. In wet tractor: puddling 45-60 cm depth disturbed soils, q d smearing surface soil bulk

density in the skid trails was 13% 13;teater than undisturbed, and macro porosity was decreased 49%.

Tractor and skidder Lower Coastal LobloIly pine Loamy sand to Total average disturbed logging: primary Plain (South sandy loam area was about 40%. and secondary Carolina and surface soil and Logging disturbance, skid traits and Virginia) sandy loam to especially on log log decks clay loam desks, increased bulls

subsurface soil density and soil strength and decreased infiltration rate and aeration porosity.

Wet logging by Upper Coastal Plain Pine-hardwood h a m sand to silty Wheel-rutting increased rubber-tired (northern clay loam soils bulk density 20% and skiddm Mississippi) decreased macro compaction and porosity and ruts infiltration 66% and

90%, res@veIy. Compaction by site Coastal Plain LobloUy pine Sandy loam Surface soil bulk density

preparation: one (eastern Texas) surface soil and increased about 10% and two tractor loam to sandy in the k t tractor P== loam subsurface pass, and the second

soil pass increased 1% additionally.

Ganison and Rmel l (1951)

Steinbremer and Gessel (1955)

Youngberg (1959)

Hatch& et al. (1 970)

Dickerson (1976)

Simmons and EzeU(1983)

140 SJAF 28(3) 2004

Moist soil logging Piedmont (Noah Loblolly pine Clayey, kaolinitic, by rubber-tired Cmlina) phtation therinic, Typic skidder: whole- HapIudults tree and skid trails

Logging by skidder: Coastal Plain P- and (northern secondary trails Louisiana) and logging decks

Loblolly pine Fine loamy, plantation siliceous,

thermic Typic Paleudults

Wet-weather Lower Coastal 70-yr tupelo- Vertic fluvaquent, b x i n g by Plain "ypress very wet, skidder and (southwestern swamp shrink-swell helicopter Alabama) clay soils

Table 1. (continued] "-A. A*-.,,, " A - " * - * " A w - - - - - - - * - ----

Site S W t V p e Soil EBmf Refeteact: - - - Bulk density, saturated

hydraulic conductivity, an aeration porosity were decrtased in all dism-bfxi surface soils. Bulk density was decreased to depth of 30 m in skid trails.

BuUr density, hydraulic Gent et al, (19%) conductivity, an aeration porosity were decreasedinall disturbed surface soils to depth of 15 cm. Bulk density and aeration porosity were decreased to depth of 23 crn in skid trails.

Surface soil bulk density b k a b y and was significantly Vidrine (1984) Iower in primary roads and decks than the other area. Soil strength was significantly higher in the all disturbed areas, especially on primary road and decks.

Skidding treatment Aust et al. (1989), decreased saturated Aust and L m hydraulic conductivity (1 992) and redox potential sigruficantly. Soil resistance was no different among the treatments.

60-yr natural Clayey, mixed, Ail measured soil Aust et al. (1993) loblolly pine t h e d c m i c physical properties

Paleaquult, were altered poorly drained significantly in the loamy surface disturbed area. Water soil table was increased in

severely disturbed area.

Wet-weather Lower Coastal Natural Moderately well to In the compacted and Aust et 4.-(1995) logging by Plain wet pine loblolly pine poorly drained, rutted soils, bulk skidder: flat (South coarse loamy density was compaction and Carolina) sand to loam signifhntly higher, rutting surface soils and and macro porosity

fine sandy clay and hydraulic loam to clay conductivity were subsurface soils significantly lower

than untrafEcked area. v

Harv&g cffcct on soil; negatiyc (-).

Wet-weather Lower Coastal by Plain (South

skiddm dismbed Carolina) and htted

and logging decks) and direct-seeded loblolly pine seeding responses to the disturbed soils (Tables 1 and 2). They found that soil bulk density was about 10-14% higher in primary skidding roads and logging decks compared to undisturbed areas, and seedling survival and height growth in the disturbed areas were 88-91% and 39-59% lower, respectively, than those of the undisturbed areas.

Rubber-tired skidders also caused severe soil disturbances such as soil smearing, rutting, and churning in wet, fine-textured soils in the Southeastern h w e r Coastal Plain

(Hatchell 1981, McKee and Hatchell 1986). These severe soil disturbances are commonly associated with the breakage of soil aggregates, realignment of soil particles, fonna- tion of water and air impmeable layers which often pro- lbngs so2 saturation period, decreased decomposition rate of incorporated organic matter, and decreased seedwg survival and growth (Shoulders and Terry 1978). Scheem et al. (1994) compared planted loblolly pine seedling growth within rutted and undisturbed sites in a wet pine flat in. South Carolina. They found higher mortality and lower

SJAF 28(3) 2004 141

We-weather lo%ging by skidder. c-tioa and rutting

Table 2. Summary of wet- and dry-weather timber harvesting effects on subsequent tree growth.

Site Trp;~: 73xe Tree l&~n ageD V d b growth -

Old R e b o r n Seedling s&vd in 1st g r o h Oxisofs, Douglas-fir well-

amf 2nd growing seasons were same

aggregated, across the £riable treatments. S e e d k g clayey growth was tfie mface soil lowest in tmctor on Miocene mads and the highest bas& in nomqacted

area Rutting: in Piedmont Lob!olly Clayey 3 Tree height, diameter, and out ruts peny (mw Pine horizon, and volume in the

Nore plantation typical (1964)

ruts were less than. -&I

8 2 L t those out of ruts.

soil Wet- and dry- Coastal @-Y Poorly drained 40 Trees which were ~ & h r i n ~ weather Plain even- silt loam disturbed 3 to 4 and dinning by (southeastem loesssoik - sides of mting area Rawls crawler -1 y with deumxd basal area tractor. pine FA=,"' growth.

(1970)

puddling and sm&g

depth

Tractor and Lower Loblolly Loamy sand to 1 Stocking of naturally Hatchell skidder Coastal Pine sandy loam seeded sfxdkgs was et at bg&g: ' Plain surface soil lower in the primary (1970)

(South and sandy skid trairS and higher secondary Carob loam to clay in the secondary skid skid trails and loam subsoil trails than and log Virginia) undisturbedaraa decks Seedling height on

tfie skid mi ls was gemsally lower than undisturbed area

Compaction Costa1 Loblolly Sandy bam to +Z One-pass compaction Si~n~nons by site Plain pine loamy sand on sandy loam soil and preparation: (eastem surface soii showed 10095 EzeB one and Texas) and laam to survival and (1983) two tramx sandy loam in& seedting Passes w-ce root growth, but

soil compaction on h y sand so3 decreased survival and inhibited seedLing root growth.

All dhubed area -&seedling s m v a l aml helm Vi- gmwth, es@~ (1984) the decrease was Ggnikmt in primary roads and decks.

Seedfing survival, sc- height growth, and et aL volume in ruts are (1%)- signiscantxy lower Aust than non-td%cM et al. area. (1995)

Coastal Loblolly Fine loamy, 5 Plain pine silicews, (northern plantation h h c , Louisiana) 2Elwts

Lower Coastal Plain wet pine

Natual Moderately loblolly well to pine poorly

M e d , flat - coarse (South loamy sand cadha) to loam

&ace soils adf ine sandy clay loam to clay subsurface soils

a Tree age &ears) since the establi-t. Harv-g effect an treG (8-8) swival and gmwrh; positive f +), negative (-), no (=), and not av&k (N/A].

seedling growth in the rutted sites regardless of site preparation, a-ad concluded that the rutting had negative conse- quences for seedling survival and growth because it decreased site drainage and aeration.

These field experimentdl results were fuaher supported by greenhouse experiments. Fog and Ralston (1967) tested loblolly pine seedling growth response to experimentally compacted sandy, loamy, and clayey soils. They observed that root lengths decreased when noncapillary porosity be-

came less than 1096, which was achieved by a 3.5 kg static pressure. Mitchell et al, (1982) conducted a similar loblolly pine growth response study by analyzing the inau- ence of different levels of compaction on a typical sandy loam Piedmont surface soif. They found that seedling root mass decreased linearly as bulk density increased from 1.2 to 2.0 Mg mm3, and root adsorbing capacity decreased sigruficatltly when bulk density exceeded 1.4 Mg m-3. These studies clearly indicated that rubber-tired skidders

142 SJAF 28(3) 2004

2uyz10gaa.W (5) : u o p q p a ~ 170s pW ~ % W S OOqm3 pOS -am mOpA '(~861 xarlS!d pm T)QQ~* pd 334 Pm 9-q 4 p s w e p s q DWXU ap?Eto B ~ w o c k 0 3 ~ (p) PAWS 2lpaas r o ~ moppow QOS anoldp 01 papuatq :nogaqma8 xagaq 303 EOS ~ J Q - 3qsodxa (c) :uoggad s! pw spos a3epns m ~ p l d ~ uopt?mdard 8:s ~ W J O \ ~ J

-mo:, anpqaf3a~ Sfq3npar lo f3~01qum (2) fsfrqap mmq P~WaW: qW=daJd q?S 8 a 3- Sqsradqp 30 % s m 3 a p (I) m uogeseda~d q s JO saf3~ma nopereda~d ags jo s+paga nog~ro~au?v -PV *nopmdaxd aqs IOJ pasn uaaq Q A E ~ 3-13 aa~dmoa p w 6%qunom '3- ' g q s q ' 3 - q '8qosqns -q)~o;ffj pm PAWS

%qddoq:, ' % ~ d p ~ s '8-q w q3ns szuaaowa p p q a 8ol[paes pa3npax imp oog3edmo3 pos ~ I W ~ ~ ~ S pasnea

Table 4. Summary of site preparation effects on t r e e growth for the Florida Penisula.

B & w FL s PD (1963)

Haines and FL PD Pritchitf (1 964)

McMinn (1969)

LeMartz and McMinn (1973)

Mann and McGilmy (1 974)

Schdtz (1976)

Pritchett (1979)

Wilhite and Jones (1981)

Slash 4 chop, Cbop w o w , ClhopBed, and Clear- Harrow

FL PD Slash 5 Bm,Chop, Double chop, Clear, and Bed

FL s PI3 Slash 10 Burn, Chop, Double chop, Clear, and Bed

FL s - Some Slash 8 Burn, Disk, PD wet Low bed, and

High bed FL s PD Slash 4 Control, Burn,

Bum-Disk, and B m Disk-Bed

FL sl PD Wet Slash 8 Burn, Burn- Disk; and Bum-Bed

FL s PD Wet Slash 35 Non-bed and Bum-Bed

Burger and FL PD Wet Slash 2 Bum-chop and fitchett Bum-Blade- (1988) Harrow-Bed

- Bedding increased seedling survival

and height growth signis~atltly in old field and forested land.

+ Bedding inawed setdling height significantly.

+ Clear-how was the highest tree growth, but bedding was the most cost efficient. Higher the site preparation intensity was the better the soil properties, root development, and tree growth were.

+ Mechanical site preparation might clecmse survival but increased tree height, Bedding was the highest tree growth.

+ All mechanical treatments increased tree growth between age 5-10 by controuing competing vegetation.

+ High bed in wet sites and low bed in dry sites increased seedling heights,

3. Bedding improved survival. S e d h g height growth increase were same in the bedding and didsing.

+ Bedding increased seedling survival and tree height growth.

+ = Bedding had the highest average total height on age 35, but its annual growth became the lowest after age 1 8.

+ Seedling height, diameter, and volume in bedded area were significandy higher than chopped area Bedding k d foIiar N level but did not change P and K levels.

Soil classes. s = sandy, 1 = loam, sil silt loam, and scl = sandy clay loam. Soil drainage class. WD = well drained, MWD = moderately well &ed, PD = p d y drained, and VPD = very poorly drained. Soil moisture class during growing season. Tree age (year) since the establishment

* Btdding site preparation effect on seedling survival a d growth; positive (+), negative (-), w (=). and not available (NIA):'

disturbed soil to improve seedting root growth; and (6) raising seedl&i~s a ~ w a @ l r s a ~ ~ ~ E a c ~ ~ ment has different benefits. For instance, burning, scalping, and clearing remove organic matter and coarse debris and expose mineral soil, while chopping breaks down coarse woody debris and accelerates the decomposition process. However, none of these site treatments ameliorate disturbed surface soil. Subsoiling exposes mineral soil and ameliorates disturbed surface and subsurface soils, and harrowing and &king incorporate organic matter into surface soil and ameliorate disturbed surface soil. Bedding and mounding are the only methods that can incorporate organic matter, expose minerdl soil, ameliorate disturbed surface soil, and raise the seedbed above the water table to provide aerated soil. Bedding as an Ameliorative Practice for Wet-Weather Harvest Dambances

D h g the last few decades, bedding has been recom- mended over other site preparation techniques for poorly

drained and a severely disturbed areas as a potential ame- -krativepmtice~us~l994~Sincethe-l97Os;-manystsd- ies have been conducted to evaluate the effects of bedding compared to the other common site preparation techniques in the southeastern pine flatwoods (Tables 3-6). Overall, results from the Southeas&m Lower Coastal Plain indicate that bedding effectively ameliorates disturbed soil properties and improves seedlting survival and growth for moderately to poorly drained silt foam or sandy soifs. Improved survival and early seedling growth are attributed to increased aerated rooting volume ch/llcX;ee and Shoulders 1970, 1974, Mann and Mccilvray 1974, Andrews 1993), improved soil physical properties (Scheerer et al. 1994, Aust et al. 1998), better vegetation control by mechanical site prepkition (PYlann and Den 19f54, Derr and Mann 1970), increased available soil nutrients caused by increased mineralization rates purger and Mtchett 1988), and con- centrating organic matter in the planting row (Terry and Hughes 1975, Schultz 1976).

Table 5. Summary of site preparation effects on tree growth for the Gulf Coastal Plain. t

Soil Tree & ! & ~ 8 > ~ 2 ? ";~2 kt.d &wtfs

"--- SPP a~~

stm& 6 t2~cmI.~ Ds-&. 3!!$i - - CTE 5~~&2: %S p % g f % \ & ~ %xi %& ~0~~~~~ w?h &p& &

R~&X j ~ ~ ~ k t t aa>3 wxw tzhte-

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a ~ ~ i ~ ~ ~ ~ s = s a o r t y , 1 = l ~ s i l = s i 1 t l & ~ d s c l = s a n d ~ c t a y l m Soil m e class. WD = well drained, MWD = xmdwate1y well drained, PD = poorly drained, and VPD = nry poorly drained.

= Soil moisams. clasp muing growing -n. Tree age (year) since the estabLishxmL Bedding site p@m effect on seedling survival and growdz; positive (+), negative (-), no (=), and not available (WA).

Terry and Hughes (1975), however, observed negative effects of bedding on seedling survival. They reported that bedding sandy dry sites, windrows, and sites with heavy root-mats caused droughty soil conditions that resulted in low seedling survival. Poorly formed and unsettled beds on clayey soils often cause large air pockets that lower seedling survival @err and Mann 1977).

Several studies have shown that bedding has positive effects on seedling survival and growth and early tree development, but long-term effect of bedding may not be positive. Enhanced seedling growth usually occurs on bedded and other mechanical prepared sites until age 8-13 years, but the growth rate converges after age 14, and tree

diameter in control plots exceed those in the treated sites after age 15 (Cain 1978, Tiarks 1983, Haywood 1983, Allen and Campbell 1988). Fttrthermore, these studies showed that seeding height was actually lower in the second-rotation bedded areas (Tiarks and Haywood 1996) as compared to nonbedded treatments. Thrks and Haywood attributed this negative effect of bedding in the second rotation to nutrient depletion during the first rotation because soil nutrient levels in the second rotation were near critical levels.

Natural Recovery of Disturbed Soils Natural soil recovery processes are complex and gradual.

Previous studies show that complete recovery of disturbed

SJAF %(3) 2004 145

Table 6. Summary of site preparation effects on soil properties.

Startdtppe 2'3~3 Site prep."

Logging Coastal Plain pine 8-yr slash pine flatwoods plantation (central Louisiana)

Control, Disk, and Bed

Logging Coastal Plain pine 1 I-yr, 2nd Fine-silty, siliceous, Burn, W o w , flatwoods rotation slash thermic and Bed (rn.t=?t @e PIinthquic Lourstana) plantation Paleudults or

Typic GIossaqualfs, moderateIy weLI to poorly drained, low fertile soils, mostly not wet

Logging Atlantic Coastal 4-yr slash pine Aeric Haplaquods, Control, Burn, Hain flat woods plantation Burn-Disk, (northern Rorida)

= % andBum- with spodic Di&-Bed horizon in depth of 30-40 an

Wet weather logging

ZddC compaction and h g

coastal PIain flat woods (narthwestern Florida)

Lower coastk Plain wet pine flat (South Carolina)

Lower Coastal Plain wet pine flat and pmasb (North CarOIina)

8-yr slash pine plantation.

2-yr loblolly pine plantation

3-yr loblolly P& plantation

Typic Paleaquult, ~ 1 ~ ? " 4

textured, thick, dark d a c e , savanna soils

Somewhat-poorly to ~W-P~J.Y drained, coarse loamy sand to loam surface soils and fine sandy clay loam to clay subsurface soils

Paleaquults, somewhat poorly ckaindfine loamy, siliceous soils or Typic A l b W t s , p r l y wed, g~v? ""

Burn, Burn- Disk and BumBed

control, Disk, Bed, and Disk-Bed

KG-Rake, and Rake-Bed

Mechanical McKee and Shoulders treatolenrs decreased

( 1 974)

organic matm content in surface soils significantly and generally decreased soil nutrients and B C . Bedding improved surface soil aeration, but &king bad no effect

OriglnaI site Tiarb and Haywood preparation was (1996) p-"4 and the site was burned prior to planting. Soil strength was significantly high in the mechanical treatment plots, and soil nutrients were slightly low in the 2nd rotation.

Bedding in- Schulk (1976) available soil nutrients by mounding nutrient rich surface soit, decreased woody vegetation, and altered mi-wte by exposing mined soif.

+ Bedding increased Pritchett (1979) OM, N, CEC, and extractable nutrients.

+ Pret weather Scheerer et al. (1994)+ harvesting Aust et al. (1998) created m. In t r m c w area, bedding increased hydraulic conductivity and macro porosity significantly. Dishg decseased hydranIic conductivity and m%ro porosity =- M c M or not

f Bedding T q and Hughes con^^ organic matter,

(1975)

P, K; Ca, Mg. and Mn.

SJAF 28(3) 2004

Table 6. (continued) -- -

ha&% Lower Coastal 1- and 2-yr Plain pine slash pine flatwoods pIantation (north- ELorida)

-w35N3 Lower Coastal 23-yr l0bI.oI.I~ Typic Ochquults Control mop- Plain pine or Palequutts, or Burn, Scalp- (southeastern plantation Aerie Bed, and Virginia) pal-&, Ditch

poorly drained, fine loamy, siliceous soils

Wet-weather Lower Coastal 7-yr IobloIIy Somewhat poorly and dry- Rain (South pine drained to very weather Carolina) pIantation P O O ~ Y dra i?d bgglng folzowed

aqualfs

" Site Preparation kafmmts. Site pieparation effcd on soil; positive (f) and negative (-).

soils can take 40 years in the North Carolina Piedmont (Perry 1964), 18 years in the Atlantic Coaststal Plain (Hatch- ell et al. 1970), and 8-12 years in the northern Mississippi Coastal Plain (r>ickerson 1976). Soil recovery process can be described with an exponential recovery curve (Webb et al. 1983). This suggests that initial recovery is fast, but a long periqd would be required for complete recovery. These studies suggest that soil recovery processes may vary by soil mineralogy, regional climate, and type of disturbance; however, the detailed recovery processes are not well-known.

The most important natural soil recovery process axe shrinking and swelling caused by 2:l-expanding clay con- tents, biorurbation by soil fauna and flora, and soil expansion and contraction due to freezing-thawing cycles (Koe- nigs 1963, Larson and Allmaras 1971, Gracen and Sands 1980, Webb et at. 1983). SM-swe l l clay content and soil fauna and flora populations are especially hportatlt in the Southeastern Coastal Plain because of its alluvial soil parent material, with mixed mineralogy and warm temperature c w .

Soil Recovery by Shrink-Swell Ctay Montmorillonite, a common clay mineral in soils of the

Southeastern Coastal Plain, is responsible for soil shrinking and swelling (Koenigs 1963). Soil shridkage occurs when

Control, Burn- + - Intensive site Burgs aKt chop, and preparation Pilitchett B w - B M - increased N, P, (1988) Hanow-Bed and K in the soil

solution, but di5cmSed total N because of bwnkg, organic matter removal, and high mineralization.

Bedding resulted Andrews the lowest soil (1993) nutrients among the trearments because of scalping. Ditching was the highest nutrient availability because of better soil aeration and mineralization.

Wet log and No significant Eisenbies et al. P ~ G dry difference log and between wet and

(2004)

plant, wet dry logging Iog and bed, where bedding dry log and was used. Wet bed harvest with no

bedding had lower tree heights at age 5. .-.-- ''

aggregates lose inter- and intra-aggregate water. Inter-aggregate water loss causes a decrease in the double di£fuse layer (the reverse process of swelling), and inha-aggregate water loss causes reorganization of the soil particles and redyction of the aggregate intra-pore space &arson and Allamas 1971, Brown 1977). Therefore, shrinking and swelling processes are affected by: (1) the shrink-swell clay content: (2) structural balance among soil particles (Koenigs 1963); (3) the cation concentration of the water (Bob et al. 1985); and (4) soil water content.

Many researchers have studied soil shrink-swell behavior and the effect on soil physical promes. McCowan et al. (1983), Pillai-McCarry and Collis-George (1990), and Sannah et aL (1996) found that disturbed soil structure improved with repeated wet-dry cycles. FWai-McCanry and Collis-Ceorge (19%) compared expanding and nonexpanhg clayey soils under dBmnt mechanical treatments (ponded and puddled) and wetting cycles. They found that multiple wet* cycles produced a polygonal cracking pattern and small crumb aggregates. Repeated shrinking and swelling broke weaker soil @cIe bounds and caused contraction of strongly bound soil particles as finer and stable aggregates. In the m e c f i d ttraiment comparison, they found that the puddled treatolent prodaced larger and more angular-shaped aggregates than the

ponded treatment, Puddling broke soil -gates and homog- eniztxr soil structure; therefore, the strength. of soil particle bounds became relatively d o n a , and s-g-swelling was less effective io ptoduchg d e r and more stable aggregates. 'They also found that extended dry @ads did not have a s i m m t effect on soil cracking. mwa et aL (1999) fomd that deeply rutted and churned skid trails in the Sou& G a r o h Coastal Plain had partially recover$ within 2 years of disturbance due to the positive effects of s-g and swelling.

Soil Recovery by Biological Activities Soil biological activities also contribute to soil recovery

(Webb et al. 1983). Among the diverse soil organisms, exuthworms, bacteria, and h g i are especially important for initial breakdown of coarse organic debris (logging slash) and litter (Gosz 1984, Waring and Schlesinger 1985, Priteh- ett and Fisher 1987). The primary effect of initial fragmen- tation of large organic debris is the physical increase of surface area and the chemical breakdown of stable soil organic matter cellular structures for M e r microbial decomposition ('Waring and Schfesinger 1985).

Earthworms are probably the most important soil mac- rofauna in temperate forests because they: (1) are abundant in the forest system; (2) fragment litter and mix partially decomposed organic materials with mineral soil; (3) enhance soil structure; and (4) create continuous macropore space, which improves water permeability and soil gas exchange (Gosz 1984, Warkg and Schlesinger 1985, Pritchett and Fisher 1 987).

Among the diverse soil microflora, bacteria and fungi are .,specially important for initial breakdown of coarse organic iebris and litter because of their ability to decompose plant ;elldose and lignin (Waring and Schlesinger 1985,FYitchett md Fisher 1987). Although many different types of bacteria ue actbe under diverse environments, bacterial activity is ;enedy affected by soil moisture, temperature, litter quan- ity, and litter decomposition stage (Lundgren 1982, Berg :t al. 1998).

Although activity and abundance of fungi are a function tf soil envjroment, fungal activity is less susceptible to hanging levels of soil moisture and temperature (Baath and ;oderstom 1982, Berg et al. 1998). Fungal activity is more ffected by litter nutrient content and the decomposition tage. Dexter (1978) found that fungal activity decreased ue to high earthworm activity because earthworms physi- ally disrupted mycelium and predigested stable carbon for acterial utilization.

Soil acidity has a large influence on soil biological ctivities (Pritchett and Fisher 1987). An acidic forest floor, 3ch as that found in warm temperate forests, inhibits earth- ?om and bacteria activity (Uranhg and Schlesinger 1985) ecause an optimum soil pH for earthworm activity is :tween 6.0 and 8.0, and many aerobic cellulose-decorn- ~ s h g bacteria are active above a soil pH of 5.5. Although )me earthwom species are active in acidic soils (McLean id Parkinson 1997), the primary decomposers in acidic lrrest floors are fungi and microfauna, such as Protozoa,

Nemtoda, and Enchytraeid (Gosz 1984, Waring and Schlesinger 1985), and lisopoda (Soma and Saito 1979).

The Effect of Silvicdtural Practices on Soit Naturai Recovery Processes

Typical site preparation techniques on Coastal Plain flats are intended to ameliora* disturbed surface soils by loos- ening the soils and elevating them above the water table. These elevated soils are exposed to M e r abiotic and biotic weathering processes. The soil recovery process is acceler- ated. However, disturbed subsurface soil horizons that can sigtuficantly affect site hydrology are not ameliorated by common site preparation techniques because most teoh- niques do not aerate and loosen subsurface soils. Therefore, bedding does not improve internal soil percolation and normal water table fluctuations (Blake et al. 1976, Bullock et d.1985).

Si lvicul~al practices may enhance natural soil recovery processes. Because a principal natural soil recovery mech- anism in the Southeastern Lower Coastal Plain is soil sluhking and swelling, a silvicultural practice that causes water table fluctuations (wet-dry cycle) would enhance the recovery process. Bedding, mole plowing (Spoor et al. 1982), subsofig, drainage, and establishment of vegetation are examples of practices that influence the water table.

Forest operations also have significant effects on soil biological activities because the operations alter the forest soil environment. Forest harvesting typically leaves large amomts of organic debris, and the large debris is often chopped and mixed with surface soils during site preparation. Since forest harvesting increases soil surfaCe temperature and surface water table, the post site preparation soil environment is conducive for soil biological activities.

Summary and Conclusions Wet-weather harvesting is almost certain to occur on

some sites within the CoastdI Plain region due to the combination of extended periods of rainfall, low relief, and slow drainage. Wood consumers commonly attempt to ;"minimize the impact of extended wet-weather by increasing wood inventories, but the humid conditions of the southeast, costs of wood storage, and uncertainty of the need for storage in a particular year reduce the feasibility of this option (Loving 1991, k b e l 1993). Overall, the effects of wet-weather harvesting on site productivity in the Coastal Plain are mixed because the subsequent effect. are very site- and soil-de- pendent. Site productivity may be reduced by wet-weather harvesting on some types of sites while others are much more resistant andlor resilient to disturbance. Sites that appear to be the least susceptible to losses in IoGg-term productivity are those that have some combination' of the natural andlor artificial ameliorative properties. Important natural ameliorative properties include factors such as shrink-swell or freeze-thaw soils, natual high fertility levels, active soil fauna, andlor sediment inputs. Artificial ameliorative amendments include such common practices as mechanical site preparation, maintenance of minor drainage, or fertikation. Sites that would appear to have the

48 SJAF 28(3) 2004

greatest potential for loag-term site productivity losses are those having the potential for soil erosion, little or no shrink-swell activity, and low fertility and organic matter levels. If possible, severe so2 disturbances should be avoided on such sites. Over the past decade, a variety of low-hpact harvesting systems and techniques, such as shovel-logging, creation of skid& corridors that use slash for reduced ground pressures, u m o n of low-ground pressure forwarders and skidders, and aerial harvests, have been effectively used to minimize site disturbanew on coastal plain sites (Stokes and Schilling 1997, Sloan 2001). These techniques should be considered for particdarly sensitive sites or unusually wet conditions. If these sensitive sites are severely rutted and churned then artificial amelioration should be considered. Traditional site preparation practices such as bedding and fertilization have proven effective on numerous sites. In the past decade, a few land managers have implemented mounding on coastal plain sites. This technique has been widely used in the L&e States, Canada, and Scandinavia (Akerstrom and Hanell 1997), yet little data has been published regarding its effi- cacy on coastal plain sites. Overall, a synthesis of the research indicates that forest managers should minimize wet-weather harvesting on potentially sensitive sites, con- centrate wet-weather harvesting on sites that have natural ameliorative properties, and be prepared to use additional site preparation measures as ameliorative techniques.

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AUST, W.M, J.A. BURGEE, G.A. S- m W.H. M6KEE, JR 1998. Amelioration of compacted and rutted skid trails on wet pine flats: Fourth-year results. P. 386-391 in Proc. 9th Biena South. Silvic. Rcs. Conf. USDA For. Serv. Gee Tech, Rep. SRS-20.

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SOUTI IERN Volume 28, Number 3 August 2004

t site preparation effects on coastal plain sites: a … · preparation on disturbed soils....

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