Dr. Greg Bruland NREM 461

Transcription

1 Pasture, Rangeland, Forest Management Dr. Greg Bruland NREM 461 1

2 Soil conservation strategies for non-cultivated land (El-Swaify et al. 1982, Morgan 2005) 2

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4 I. Pasture, Rangeland & Forest Mgmt A. Pasture, rangeland, forests gen. have high infiltr., low erosion 1. When altered by ygrazing, g, logging, g, etc., they are so steep, shallow, sandy, otherwise limited, that their cover is damaged & 4

5 B. Pasture Def., Dist., Mgmt 1. pasture: intensively-managed grazing areas in humid climates or similar irrigated areas in arid/semiarid climates a. tillage when b. Water erosion at this site? 5

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7 2. Systems of Pasture Mgmt a. Continuous: allow livestock access to pasture during grazing season, w/ little to no recovery i. w/ low-mod. stocking, suitable for bermudagrass, Kent. bluegrass, ryegrass, & tall fescue 7

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9 b. Rotational: placing fences so livestock graze only part of pasture at a time i. used for smooth bromegrass, inter. wheat grass ii. grazing season extended by using cool-season grass (i.e. ) in 1 pasture, switching to another w/ diff. spp (i.e ) for midsummer 9

10 Rotational grazing pasture system 10

11 c. Deferred: delay start of grazing beyond normal period i. Why? ii. deferred & rotational 11

12 C. Rangeland Def., Dist., Mgmt 1. Rangeland (RL): areas where native grasses, shrubs, trees used for forage. Some may be fertilized or reseeded. a. seldom or never plowed b. 12

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14 2. Silvopasture (SP): combines trees w/ forage & livestock prod. Trees managed for timber & provide shade, shelter for livestock, stress & sometimes forage prod. a. In conifer & hardwood plantations, grazing provides added b. Silvopastoral system with cows, slash pine, & bahia grass 14

15 Other silvopasture examples 15

16 3. RL & SP Mgmt a. Best way to control erosion is to limit stocking rate so that adeq. veg. cover present b. Effective Mgmt. practices: i. delay spring grazing so grasses can establish ii. adjust stocking rate by season, precip. iii. leave 50% of forage for reserve & residue iv. v. 16

17 D. Forestland Def., Dist., Mgmt. 1. Well-managed forests make best cover for watersheds a. trees provide protection only after uniform cover of leaves, needles accumulates on soil surface; 17

18 3. Forestland (FL): area w/ growing trees or soil capable of supporting trees a. Tree: any woody plant >15 ft (4.5 m) in height, supported by a single stem 18

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20 2. Much of erosion on managed FLs assoc. w/ logging roads 20

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22 a. Maintaining forest roads i. annual maintenance ii. clear culverts & ditches of debris iii. check for signs of instability 22

23 3. Main methods of harvesting trees (least to greatest impact): a. Selection: removing individual or small groups of trees 23

24 b. Shelterwood: remove all mature trees in a series of cuts several e years apart, while new stand develops e in understory i. mimics natural disturb. 24

25 c. Seed Tree: leave only enough trees to bear seed for natural a regen. 25

26 d. Clearcutting: remove all trees & understory from logged area 26

27 4. Specialized Timber Harvesting Equipment (initially teams of oxen) a. Goals: compaction, erosion b. feller-bunchers: cut trees at but & transport them vert. for short dist. to pile for skidding i. 27

28 c. various other types of tractors, skidders used i. tires? 28

29 d. track-type tread vs tires e. tractors, t skidders, etc. used when slope 29

30 5. Specialized Log Transport Systems to compaction & erosion in steep slopes a. High lead cable: only front end of logs lifted to clear obstacles i. logs make skid trails 30

31 b. Skyline cable: used as early as 1915 in remote, steep, unstable sites i. when done properly, 31

32 c. Balloon cable: use balloon to lift & transport logs in steep slopes i. adapted for selective logging, 32

33 d. Helicopter: use helicopter to lift & transport logs i. very low impact, requires fewer roads, $$$ ii. 33

34 Comparison of environ. impacts between helicopter & tractor logging in Sarawakian dipterocarp forests, Malaysia (Sarawak Forest Department) Metric Helicopter No. trees felled & extracted ha No. trees damaged per tree extracted 3.1 Open space created by canopy openings & 4.2 skid trails as % of logging area Dry day stream turbidity (NTUs) Wet day stream turbidity (NTUs) 2.1 Tractor (Bulldozer) 34