Disturbance Effects on Xeric Oak Forests in Oklahoma and California

Transcription

1 Disturbance Effects on Xeric Oak Forests in Oklahoma and California Ryan DeSantis University of California Cooperative Extension Shasta, Trinity & Siskiyou Counties; Redding

2 1. Introduction 2. OK research (CT) a) Oak forest fire regime b) Fire effects on oak forest regeneration Drought and reduced fire effects on: c) Oak forest composition & structure d) Oak forest recruitment e) OK research conclusions 3. CA research (WCF)

3 1. Introduction Oak Abundant & widespread Highest abundance and basal area of any U.S. hardwood genus Keystone species Shade intolerant Relatively drought tolerant Deep rooting & xeromorphic leaves Fire adapted/tolerant Advance reproduction

4 Oak Fire adapted Perpetuates cycle of fire Flammable litter Fire tolerant Thick bark, scarring Sprouting ability: Fire- Kills aboveground parts Stimulates sprouting from dormant buds Decreases competition from fire-intolerant species Without disturbance (e.g. fire), less oak 1. Introduction

5 Climate in OK & CA oak woodlands Cross Timbers, OK Northwestern CA Ranges: cm ann precip, 15-19C mean ann temp Averages: 88 cm avg ann precip, 16C mean ann temp 1. Introduction

6 2a. Fire regime of an upland oak forest in Oklahoma Cross Timbers area fire history Assumption: Burned often in past, not present, however- Fire frequency changes: Abrams: KS (decrease) Clark: OK (increase) Guyette & Stambaugh: OK, MO, AR (increase, decrease & no change)

7 OGMA prescribed fire Wildlife habitat improvement Biodiversity maintenance Fire hazard reduction What is the appropriate: Fire frequency? Burn season? Burn weather? 2a. Fire regime of an upland oak forest in Oklahoma

8 95% of scars in dormant season position Fire Scar Pith Date Inner Date Outer Date Bark Date Recorder Years a. Fire regime of an upland oak forest in Oklahoma

9 SEA: no relationship between drought & fire occurrence Fire Scar Pith Date Inner Date Outer Date Bark Date Recorder Years a. Fire regime of an upland oak forest in Oklahoma

10 Mean Fire Interval Osage: 5.9 Creek: 3 } Pre-EAS: 4 Post-EAS: 2 Prescribed Burning: 1.8 (1989-) Fire Scar Pith Date Inner Date Outer Date Bark Date Recorder Years Osage ( ) Creek ( ) Post-EAS( ) a. Fire regime of an upland oak forest in Oklahoma

11 Discussion 18 th -20 th Centuries: more fire 20 th Century: larger/more intense fires? Prescribed burning: mimics post-eas but not pre-eas Humans played important role in fire history Settlement history Dormant season fire scars Little evidence of climatic effect (drought, lightning) on fire; mgt. implications? 2a. Fire regime of an upland oak forest in Oklahoma

12 2b. Effects of fire on upland oak forest regeneration Oak decline & decrease Poor regeneration Failure to recruit into overstory Decreased fire Promote fire-intolerants & decrease fire-tolerants

13 Study objectives Differential fire effects on oak subgenera? Post oak (white) & blackjack oak (red) Differing fire frequencies, years since last fire 2b. Fire regime of an upland oak forest in Oklahoma

14 Discussion Blackjack oak & post oak: regeneration under closed canopy even in absence of fire Periodic low-intensity dormant season burning encouraged regeneration of both species One fire/decade most favorable; more fire bad for oak sprouts 2b. Fire regime of an upland oak forest in Oklahoma

15 Ratio of blackjack oak clumps & sprouts to BA higher than expected Blackjack oak: 1299 (3467 sprouts/ha, 2.67 m 2 /ha BA) Post oak: 287 (5045 sprouts/ha, 17.6 m 2 /ha BA) Abundant blackjack oak sprout reproduction, high sprout mortality rate in understory, poor recruitment into canopy Periodic fire important for maintenance of oak reproduction, too much fire detrimental to oak 2b. Fire regime of an upland oak forest in Oklahoma

16 2c. Upland oak forest composition and structure 209 intact forests sampled by E.L. Rice & W.T. Penfound to characterize Oklahoma s upland forests 1959 Findings published in Ecology

17 Forests Sampled c. Upland oak forest composition and structure

18 2c. Upland oak forest composition and structure

19 2c. Upland oak forest composition and structure

20 Study objectives How have species composition, basal area, tree density and sapling density changed? What factors control patterns of change? Have different regions experienced different changes? How have the dominant and subdominant species changed? 2c. Upland oak forest composition and structure

21 m 2 ha -1 (BA only) stems ha -1 (TD & SD only) Results Total basal area increased by nearly 98% and total tree density by nearly 84% s 2000s 1950s 2000s 1950s 2000s 0 0 Basal Area (BA)* Tree Density (TD)* Sapling Density (SD) Asterisks indicate statistically significant changes (P<0.05 from paired Student's t-tests). 2c. Upland oak forest composition and structure

22 2000s 1950s Species richness and eastern redcedar increased Blackjack oak & post oak: majority of trees and saplings in the 1950s but not in the 2000s Basal Area Tree Density Sapling Density 16% 13% 5% 40% 22% 50% 48% 6% 34% 34% Other (species <5%) 32% Black hickory Eastern redcedar Blackjack oak 53% 13% 7% 13% 46% 16% 7% 16% 15% 11% 9% 33% Post oak Winged elm 14% 15% 21% 11% 2c. Upland oak forest composition and structure

23 Basal Area JUVI QUST QUMA 2c. Upland oak forest composition and structure

24 Tree Density QUMA QUST JUVI 2c. Upland oak forest composition and structure

25 Sapling Density QUMA QUST JUVI 2c. Upland oak forest composition and structure

26 Discussion/conclusions Absence of fire Eastern redcedar encroachment, decreased oak Decrease in fire; changes in stand structure Savanna to closed-canopy forest 2c. Upland oak forest composition and structure

27 Fire Importance Fire suppression; canopy closure; increased shade Dramatic increase of shade-tolerant, mesophytic trees Decreased flammability due to mesophytic litter & cool, humid microclimate Pre-1900 Mid-1900s Early 2000s Foreseeable future Mesophication Source: Nowacki & Abrams c. Upland oak forest composition and structure

28 Source: Nowacki & Abrams c. Upland oak forest composition and structure

29 2d. Upland oak forest woody species recruitment Major influences on plant community species composition: Climate Fire Both can predispose oak establishment, however- Severe drought (& decreased fire) could decrease oak

30 South-central North American fire regime: Anthropogenic Promoted oaks Limited eastern redcedar Decreased frequency during 20 th Century? Severe 1950s drought in Oklahoma 2d. Upland oak forest composition and structure

31 Study objectives Establish timing of dominant woody species recruitment in OK upland forests Eastern redcedar, blackjack oak, post oak Determine links between changes in woody species recruitment & drought and decreased fire Determine trends in recruitment 2d. Upland oak forest composition and structure

32 2d. Upland oak forest composition and structure

33 2d. Upland oak forest composition and structure

34 2d. Upland oak forest composition and structure

35 2d. Upland oak forest composition and structure

36 Discussion/conclusions Evidence for decreased fire 1950s & current analyses Less fire-tolerant species, more fire-intolerant species Oak regeneration vs. eastern redcedar regeneration Sprouting vs. rapid seed dispersal Rapid eastern redcedar growth and reproduction: Recruitment into canopy gaps Reducing recruitment of shade-intolerant oaks 2d. Upland oak forest composition and structure

37 2e. OK research conclusions Mostly anthropogenic fire, increased since EAS, little connection to climate Fire of low intensity AND frequency favors oak regeneration (sprouting), some advance reproduction can persist without fire

38 Drought and decreasing fire frequency: Led to changes in composition and structure Less oak, more mesic/invasive species Led to changes in dominant woody species recruitment Total recruitment increased after 1950s drought, followed by- Increased eastern redcedar recruitment Decreased oak recruitment 2e. OK research conclusions

39 3. Weaverville Community Forest Oak woodland monitoring project

40 13,000 acres of federal land managed as a community forest Partnership Bureau of Land Management U.S. Forest Service Trinity County Resource Conservation District 3. WCF

41 3. WCF

42 Uses: Trail system Firewood sales Logging Provides: Timber for the town mill, educational and historical venues for local and tourist populations High visual quality for residents 3. WCF

43 Objectives: Protect viewsheds Timber harvesting and products to the local mill Salmon habitat protection Invasive weed eradication Recreation and education Fuels reduction projects Forest thinning projects Firewood collection Improve forest health 3. WCF

44 WCF oak woodland Background Ecological Douglas-fir, ponderosa pine Oregon white oak (Garry oak, Oregon oak) Oak woodlands increasingly rare Conifer encroachment, lack of fire & lack of thinning Housing development Pests & diseases (SOD, goldspotted oak borer, etc.) Most CA oak research on blue oak Forest management Stand too dense; thin Bring fire back to landscape 3. WCF

45 Fire and oak Scarring Sprouting 3. WCF

46 Oak: wound response to fire 3. WCF

47 WCF oak woodland Project objectives Decrease competition from conifers Thin & burn one oak woodland Improve oak woodland health, growth, regeneration Firewood Research questions How will thinning and fire affect growth & regeneration of oaks? Tree recruitment history? Fire history? 3. WCF

48 WCF oak woodland Conifers removed Spring-Summer 2013 Permanent plots installed July 2013 Local RPFs, BLM, TCRCD, UCCE 3. WCF

49 WCF oak woodland Plots: Twelve 1/20 ac circular plots, buffers between each Treatments (number of plots/replicates): 1. Control; no-thin & no-burn (3) 2. Thin only (3) 3. Burn only (3) 4. Thin+burn (3) 3. WCF

50 3. WCF

51 3. WCF

52 WCF oak woodland Plots measured August 2013 Local RPF, TCRCD, UCCE Pre-treatment measurements: Species DBH Height Crown position Live crown ratio Age (all trees >6 DBH cored) Dead top? Leaning? Other observations? Regeneration (<1 DBH, >6 height) 3. WCF

53 WCF oak woodland Garry oak Average (std. err.) Basal area/ac (sq. ft.) 82.7 (11) Mean DBH (in.) 4.5 Volume/ac (cu. ft.) (329.8) Trees/ac (>5" DBH) (39.4) Saplings/ac (1-4.9" DBH) (72.9) All trees Total Garry oak Ponderosa pine Douglas-fir Seedlings/ac (<1" DBH, >6" height) 420 (87.2) (78.3) 145 (50.4) 13.3 (6.2) 3. WCF

54 WCF oak woodland Trees marked December 2013 Oaks cut February 2014 Only trees <6 DBH cut; all trees >6 DBH tagged for repeat measurements Residual oaks average 15 spacing Disks removed from cut trees for fire history and tree-ring chronology development No existing Garry oak chronologies on ITRDB; closest ITRDB chronologies from South Fork Cottonwood Creek blue oak 3. WCF

55 WCF oak woodland Cut trees used as firewood Logging residue piled off-site Prescribed burning April 2014 Trinity County RCD July 2014 daycamp Post-treatment measurements (Summer 2015): Same, with cores taken to determine annual increment (tree-ring) growth 3. WCF

56 WCF oak woodland Data collection will allow us to characterize: Stand structure, composition & age Tree growth (DBH & MAI) Regeneration Future: WCF oak woodlands field day? WCF oak woodlands monitoring project interpretive trail & plot signage? Publications? 3. WCF

57 Ryan DeSantis Forestry Advisor Shasta, Trinity & Siskiyou Counties University of California Cooperative Extension (530)

58 Fire Index 2a. Fire regime of an upland oak forest in Oklahoma

59 SEA a SEA: -0.6 All fires (a) All fires >2 trees scarred (b) PDSI grid points 179 & b Lag in years from fire year (Fire = 0) =0.05 =0.01 2a. Fire regime of an upland oak forest in Oklahoma