a Guide to Management - USGS National Wetlands Research Center

More documents

Recommendations

Info

Table 7. Nutrient and sediment export in runoff from forested and clearcut wetlands in the southeastern coastal plain. Forest Year description of Concentration, mgll Flux, kglhalyear (dominant sama- trees) lini Treatment N03 NH4 P K Ca Mg Ss* N& NH4 P K Ca Mg Ss* Mixed hardwood Control 0.47 0.047 0.80 5.5 2.7 2.5 - swampa (bald Drain 0.94 0.074 0.87 10.8 3.5 50.0 cypress, tupelo, Drain, log, prepare 0.20 0.026 1.6 6.Q 2.2 8.0 sweetgum, red Drain, log, prepare, 0.05 0.022 2.0 5.3 2.3 14.0 maple) plant Wet savanna 1 Control 0.01 0.02 0.03 6.0 0.09 0.22 0.22 44.0 forestb 1 Log, chop, burn, 0.05 0.43 0.28 - 137.0 0.20 1.75 0.81 - 550.0 (slash pine) bed, plant 2 Log, chop, burn, 0.02 0.07 0.03 28.0 0.13 0.44 0.21 178.0 bed, plant Poorly drained 1 Control 0.04 0.22 0.02 0.18 0.26 0.98 2.7 0.04 0.23 0.02 0.19 0.28 1.06 2.8 flatwoodsC 1 Minimum site 0.03 0.05 0.02 0.55 0.37 1.13 5.0 0.05 0.07 0.03 0.78 0.53 1.60 7.1 (slash pine) preparation 1 Maximum site 0.07 0.12 0.02 0.90 0.94 1.05 14.4 0.17 0.30 0.04 2.25 2.53 2.6436.0 preparation 2 Control 0.02 0.07 0.02 0.05 0.37 0.53 2.7 0.03 0.08 0.03 0.06 0.44 0.62 3.1 2 Minimum site 0.04 0.06 0.05 0.25 0.38 0.77 3.7 0.04 0.06 0.05 0.26 0.40 0.82 3.9 preparation 2 Maximum site 0.03 0.08 0.02 0.45 0.89 0.66 11.4 0.02 0.04 0.01 0.25 0.49 0.37 6.4 preparation *Suspended sediment. aAskew and Williams (1984; 1986). Water quality of all treatment sitts was measured over the same period, but the sites were of different ages Sites were logged and prepared two years after drainage. Loblolly pine was planted one year later. b~ollis eta/. (1978). 'Riekerk (1982). Minimum site preparation consisted of manually harvesting, chopping, bedding, and planting. Maximum site preparation was mechanized logging, stumping, burning, windrowing, discing, bedding, and planting.
preparatlon. Ihe magnitude of nutrient and sediment loss is positively correlated with the intensity of site preparation (Riekerk 1982). Only suspended sediment and potassium levels in runoff were consis- tently elevated by harvesting and site preparation in coastal plain wetlands (Tab1 e 7). Concentrations of phosphate in water draining undisturbed and 1 ogged hardwood wet1 and forests were too low to be measured (Askew and Williams 1986). Neither phosphate nor total-phosphorus levels were increased by harvesting or site preparation in flatwoods. Concentrations of nitrogen compounds, also of concern to downstream water qua1 i ty, were signi f i - cantly raised only by drainage of forested wetlands (Table 7). Like hydric hammocks, these forested wetlands occur on flat coastal soils and sup- port rapid growth of planted pines. Maximum nutrient losses occur when the soil is bared, especially when mechan- ically disturbed, and before estab- lishment of new vegetation. Ditch in- stallation prior to harvesting, a common practice in swamps and pocosins (Ash et a]. 1983), also releases nutrients, but drainage is generally not practiced in hydric hammocks. Har- vesting systems that are less severe than clearcutting are likely to have little impact on nutrient loss from hydric hammocks. A far greater drain on the essential nutrients of hydric hammocks is their direct removal in the products that are harvested and in the debris and top soil that is pushed into windrows. If removals are averaged over the ro- tation length, a loblolly pine planta- tion might produce 7.2 t/ha of stem- wood annually and result in an annual removal of 6.5 kg/ha of nitrogen, 0.9 kg/ha of phosphorus, 5.0 kg/ha of potassium, and 6.4 kg/ha of calcium (Jorgensen and We1 1 s 1986) . When whole trees are harvested, such as biomass harvests for fuel, the biomass removal is increased by about 60%, and the nutrient removals are more than doubled (Jorgensen and We1 1 s 1986). Displacement of nutrients into windrows can be more than double the amounts lost to stem harvest (Morris et a]. 1983). The nutrient levels in hardwood timber are higher than in pine, so losses from clearcutting hardwood-dominated hydric hammocks are likely to be somewhat higher. Al- though hydric hammock soils are usually rather fertile, successive harvests of timber could lead to a decline in productivity. A transient impact of clearcutting is the elevation of the water table due to reduced transpiration. The ex- tent and duration of the rise depend on the size of the clearcut and the rate of revegetation, respectively. Increased water table height may alter the species composition of the regen- erating forest (Riekerk 1983) and may also result in greater number and size of stormwater peaks (Williams 1979). While the increased runoff is likely to be transient, the potential impact on downstream water bodies is great since many hydric hammocks adjoin marsh or estuarine systems. 4.4 LIVESTOCK GRAZING Cattle grazing of hydric hammocks is still a common practice, although not as extensive or as important as in the past. Beef cattle outnumber dairy cattle but are on the decline, whereas dairy cattle are generally on the increase in Fl orida. However, because of differences in grazing strategies, beef cattle are far more commonly grazed in hydric hammocks than dairy cattle (George W. Tanner, Department of Wildlife and Range Sciences, Uni- versity of Florida; pers. comm.). Hy- dric hammocks usually supplement larger areas of other kinds of pasture
Page 2 and 3: t ,blzrnry Na'jonal Wetlands Resear
Page 4 and 5: f$c 3piniccs and rec~mendations exp
Page 6 and 7: CONVERSION TABLE Metric to U.S. Cus
Page 8 and 9: 5.4 WATER MANAGEMENT . . . . . . .
Page 10 and 11: 28 Effects of forest thinning on th
Page 12 and 13: ACKNOWLEDGMENTS We are grateful to
Page 14 and 15: SAN FELASCO ORANGE LAKE SILVER SPRI
Page 16 and 17: sweetgum timber, with values reachi
Page 18 and 19: temperate-zone di stpi butions that
Page 20 and 21: Table 2. (Continued). Scientific na
Page 22 and 23: from numerous field trips and consu
Page 24 and 25: Species Table 3. Endangered or thre
Page 26 and 27: coast is particularly important for
Page 28 and 29: along creeks in flatwoods and sand-
Page 30 and 31: 3.4 PRE-COLUMBIAN HUNiiNG AND GATHE
Page 32 and 33: Figure 4. Hog pen in coastal hydric
Page 34 and 35: were heavily looted, and most of th
Page 36 and 37: 4.1 OWNERSHIP CHAPTER 4. PRESENT US
Page 38 and 39: Figure 8. Limerock pit in inland hy
Page 40 and 41: still proceeds in these areas and c
Page 42 and 43: Figure 11. An extensive clearcut of
Page 44 and 45: Figure 14. Bedding rows for pine se
Page 46 and 47: Figure 16. Two-year-old loblolly pi
Page 50 and 51: such as pine flatwoods, prairie, or
Page 52 and 53: . loo/: 90 0. virginiano Q. @ incon
Page 54 and 55: volume and will hold all the runoff
Page 56 and 57: experiment, seed7 ing density was s
Page 58 and 59: canoeing (on adjacent rivers and in
Page 60 and 61: 9 1940 1980 2020 2060 YEAR Figure 2
Page 62 and 63: In prehistoric times, periodic fire
Page 64 and 65: Figure 24. lnvasion of hydric hamnx
Page 66 and 67: 14. Is recreational use important a
Page 68 and 69: the canopy, health, and straightnes
Page 70 and 71: a1 though there is considerable var
Page 72 and 73: oots to which it is root-grafted, b
Page 74 and 75: cattle. Prescribed burns often are
Page 76 and 77: eftluent wniie returnir~y Ii~e whta
Page 78 and 79: - the mesic hammock upslope also ha
Page 80 and 81: arred owl, flycatchers, tufted titm
Page 82 and 83: Figure 29. Debris pile on a hydric
Page 84 and 85: . -.... 1 IYGL), wi~iit~ iire an ef
Page 86 and 87: FE r~t, si-iliai i ar.eas itray not
Page 88 and 89: in order to protect watershed, wi l
Page 90 and 91: management efforts that can benefit
Page 92 and 93: Bryant, W.C., editor. 1872. Davjs,
Page 94 and 95: Harlow, R.F. 1959. An evaluation of
Page 96 and 97: I S F n A understanding . American
Page 98 and 99:
Soil Sci. Soc. Amer. Proc. 47:591-
Page 100 and 101:
Tuschall , J.R., P.L. Brezoni k, an
Page 102:
Hvdrick Hammocks: a Guide to Manage
show all

a Guide to Management - USGS National Wetlands Research Center

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?