Silvicultural practices in the restoration of degraded ecosystems

Transcription

1 Silvicultural practices in the restoration of degraded ecosystems

2 Current conditions reflect site history and physical environment Altered fire regimes, including exclusion Forest management, including plantation establishment Agricultural use Conversions

3 Restoration DEGRADED Perturbation ORIGINAL Time

4 Restoration DEGRADED Perturbation ORIGINAL Time

5 Restoration DEGRADED Restoration Perturbation ORIGINAL Undisturbed trajectory CURRENT Time

6 To develop restoration prescriptions Current conditions Objectives for restoration (often measured as difference from some reference) A path from start to mission accomplished

7 Understanding process Model (Structural Equation Model) Understand factors that control Species Richness Data from sampling over 300 sites in 3 locations Fire, Agricultural history, Tree Abundance

8 A simple framework

9 Silvicultural practices Canopy Removal Harvest system: even-aged, group-selection Horizontal structure Influences seedling growth; sub-canopy vegetation structure and fire management Release ground-layer (+); also hardwood midstory (-) Alter fuel distribution (Gaps in pine needle carpet) Artificial Regeneration Spacing, density future forest and need for additional actions Underplanting as long as seedlings have sufficient resources to escape grass stage

10 Silvicultural practices Mechanical treatments To improve seedling establishment, modify vegetation structure, competition, fuels At the surface- chopping, mowing, mulching Below the surface- ripping, disking, bedding, mounding Herbicide applications To improve seedling establishment, shift from woody to herbaceous dominance, remove woody midstory species, alter fuels Non-specific to specific chemicals Various application methods

11 Silvicultural practices Prescribed fire To maintain desirable structure; accelerate recovery especially combined with mechanical or herbicide treatments but what if we cannot burn? Species additions To restore richness when local propagules are gone

12 A simple framework

13 So how well do these tools work for midstory reduction or as surrogates for fire? Menges and Gordon 2010 Should mechanical treatments and herbicides be used as fire surrogates to manage Florida s uplands? A review Florida Scientist Restoration goals in Florida uplands Sandhills: Open canopy, reduce midstory, increase herbaceous layer Scrub: increase bare sand; scrub size and age Flatwoods, prairie: reduce palmetto (but it spreads fire ) Landscape pattern?

14 Florida Ecosystems Florida Scrub Sandhill Flatwoods Dry Prairie Pine Rockland

15 General conclusions Mechanical treatments speed structural changes (discontinuous or high fuels; reducing hardwoods, palmetto; Mechanical and chemical treatments best used with fire (accelerate recovery; benefit herbaceous recovery) Potential risks, discussed but not usually documented (invasive species, soil compaction) Recommendations: use early in restoration process, and then transition to fire

16 Need to know Effects of long-term use of surrogates Irreplaceable fire effects? (like heat or smoke stimulated germination) Uncertainty of site quality effects (e.g. are moist sites different than xeric sites?) Recognize when fire alone can restore site (Indicators? Thresholds?)

17 Recommendations More studies of repeated treatments Use mechanical and chemical treatments in early phases of restoration, then burn Use of fire should be first choice Do not us single species focus; spatial and temporal heterogeneity = bethedging strategy for dealing with unknown effects, provide for diversity of organisms

18 Pause to consider Under what conditions will fire work to restore Florida ecosystems? What are your most pressing habitat restoration needs? What is working where you work? Your biggest success? Your biggest frustration with habitat restoration?