Belowground perspectives in southern California grassland restoration

Transcription

1 Belowground perspectives in southern Cliforni grsslnd restortion Sr Jo M. Dickens Deprtment of Environmentl Science, Policy nd Mngement, University of Cliforni, Berkeley Edith B. llen Deprtment of Botny nd Plnt Sciences, Center for Conservtion Biology, University of Cliforni, Riverside

2 The impct n exotic plnt hs on n ecosystem depends on how different it is from the dominnt ntive plnt species. (Ehrenfeld 23; Wrdle et l 24) Exotic Ntive ltered litter qulity nd quntity Type conversion Incresed fire frequency Loss of hbitt nd diversity ltered wter infiltrtion ltered nutrient pools nd cycling ltered soil microbil community Modified from Wolfe nd Klironomos 25 Bioscience

3 Objectives Determine chnges in soil ecology (mycorrhize, nutrients, soil seedbnk) cused by invsive species, nd bility to restore soil biologicl nd chemicl chrcteristics Restore grsslnds nd forblnds historiclly grzed nd frmed, currently with high exotic grss cover Test vrious techniques: mulch, herbicide, grzing, dethtching, mowing, solriztion, fire

4 Costl Grsslnd Inlnd Grsslnd PC1 PC PC1: P=.1 Restored 2 Invded Microbil community composition ws ltered by invsion PC2: P=.41 PC F:B rtio ws ltered by invsion, but the direction depended on seson. PC1

5 SPORES/ 5g SOIL SPORES/ 5g SOIL Mycorrhizl inocultion experiment 3. VEN PLNTS G. GEOSPORUM G. LBIDUM ven roots hve dominnt Glomus geosporum spores, Stip roots hve equl bundnce of three species. Five months fter inocultion, both grss species recovered their mycorrhizl species composition, showing rpid response by the fungi. (Nelson & llen 1993) VEN GRSSLND STIP INOC VEN INOC B. STIP PLNTS G. DESERTICOL UNINOC G. GEOSPORUM G. LBIDUM 2 G. DESERTICOL 1 Glomus deserticol STIP GRSSLND STIP INOC VEN INOC UNINOC

6 Estblishing Stip requires control of ven, even with mycorrhizl inoculum ven domintes in mixture, Stip dies Stip monoculture

7 Invsion lters Nitrogen vilbility ug N/g soil ug N/g soil NH 4 NO 3 C D E C E F F D B B IN REB IN REB IN REB D C B B IN REW IN REW IN REW Germintion Pek Senescence B Invded soils hd reduced extrctble nitrogen. Nitrogen cycling rtes were incresed by invsion. IN = Invded REB = Restored by burn REW = Restored by weeding

8 nthropogenic nitrogen deposition elevtes soil minerl N, cusing incresed biomss of exotic grsses reltive to ntive species Riverside-Perris Plin

9 % cover % cover Nitrogen fertiliztion incresed exotic grss cover nd reduced ntive cover EXOTIC GRSSES P =.1 plus N Plus N 1 control 8 6 * * * * 4 * * * NTIVE FORBS 1 8 P =.25 (minus 1994) plus N control * Control 6 4 * * * * * Vegettion response following the 1993 fire t Lke Skinner plus N fertiliztion nd control (no fertiliztion). p is repeted mesures probbility, * is p =.5 by yer.

10 Mulch cn be used to: immobilize excess N decrese exotic grss cover increse estblishment of ntive plnts brk ws more effective thn strw

11 Seedbnk of exotic grsslnd, ntive CSS with grss understory, nd djcent burned nd unburned sites fter the October 23 fire, Shipley Reserve. verge Seedlings per m 2 Species Grsslnd Shrublnd Unburned Burned Exotic Grsses Exotic Forbs Ntive Forbs Ntive shrubs Exotic seeds overwhelm ntive seedbnk. Fire reduces exotic grss seedbnk, providing window of opportunity for restortion (Cox nd llen 28).

12 Limited Soil Seedbnks Non-ntive richness per.5m 2 Ntive richness per.5m Unburned Burned Burned + Weed B B B B B B B B B B B Fire nd weeding incresed ntive richness nd cover, but not substntilly. Seedbnk germintion experiments show limited ntive species richness, indicting the need for seeding.

13 Controlling the Exotic Grss Seedbnk Methods Grzing Grss-specific herbicide Mowing Dethtching Solriztion

14 Prescribed Fire Properly timed prescribed burns cn removl 9% of exotic seed input nd reduce thtch. (Hervey 1949; Gillespie & llen 24; Moyes et l. 25; White et l. 26 )

15 Sheep grzing to control exotic grss 2 sheep per hectre for 2 dys in Mr/pr Grss-specific herbicide (Fusilde) Dethtching tretment to remove stnding litter

16 b b b b Exotic Grss %Cover Control Fusilde b c c Thtched Fusilde Grzing b b b b bb Exotic grss nd exotic forb cover fter two yers of Fusilde ppliction ( 99, ) nd 3 yers of sheep grzing ( 99,, 1). 1. Grzing ws not effective until the third yer becuse of drought 2. Ntive forbs were consumed by sheep, but recovered from seedbnk 3. Thtch removl hd no positive effect. 4. Grsses begn to recover from grzing nd herbicide fter 2 yers 5. Ntive forb response to herbicide still positive fter 4 yers Ntive Forbs %Cover Control Thtched Fusilde Fusilde Grzing b b b c c

17 Solriztion in bndoned griculturl Lnd 6 x 6 m sheets pplied Nov. 24 Removed Jn. 25 nd ntive forb seed mix pplied (tidy tips dominte) Nov. 24 Feb. 25 pr. 25

18 % Cover Solriztion ws the most effective method for exotic seedbnk control b bc Nonntive spp. Ntive spp. C Herbicide cd cd B B B B d Unplowed Plowed Control Mnul Herbicide Solrize Tretment Control Mowed Solrized

19 Conclusions Mycorrhizl fungi spore species composition recovered within 5 months of revegettion with Stip pulchr, however, inocultion with mycorrhizl fungi did not overcome negtive completive effects of exotic nnul grsses on Stip growth. Extrctble nitrogen, nitrogen cycling rtes nd microbil community composition lso recovered within growing seson following exotic grss removl. Nitrogen deposition nd elevted soil N from pst fertiliztion increses productivity of exotic nnul grsses, with concomitnt reduction in ntive forb productivity. Mulches to immobilize soil N nd control of exotic grsses re effective, but the best lrge scle solution is to control N deposition.

20 Conclusions (continued) Seed bnk control of exotic grss is the most urgent need. Solriztion is the most effective method, but works only in tilled, level lnd nd moist soil (bndoned griculture in winter-spring months) Grzing is only effective in yers with sufficient grss productivity. Grzed ntive forbs recover from the seedbnk nd exotic grsses recover from grzing fter 2 yers. Fusilde is n effective tretment for control of Bromus, ven nd Schismus but not Vulpi. It lso controls Erodium spp.

21 Conclusions (continued) Erly seson mowing nd disking cn be used to control exotic grsses. Spring fire is most effective to control the seed bnk, but fll fire is lso effective especilly if combined with seeding. ny of these exotic grss control methods will require reppliction t intervls of 2-5 yers depending on effectiveness of the initil tretment.

22 Cittions llen, E. B., S.. Elison, V. J. Mrquez, G. P. Schultz, N. K. Storms, C. D. Stylinski, T.. Zink, nd M. F. llen. 2. Wht re the limits to restortion of costl sge scrub in Southern Cliforni. Pges in J. E. Keeley, M. Ber- Keeley, nd C. J. Fotheringhm, editors. 2nd Interfce between ecology nd lnd development in Cliforni. US Geologicl Survey. llen, E.B., R. D. Cox, T. Tennnt, S. N. Kee nd D. H. Deutschmn. 25. Lndscpe restortion in southern Cliforni forblnds: Response of bndoned frmlnd to invsive nnul grss control. Isrel Journl of Plnt Sciences 53: Cione, N. K., P. E. Pdgett, nd E. B. llen. 22. Restortion of ntive shrublnd impcted by exotic grsses, frequent fire, nd nitrogen deposition in southern Cliforni. Restortion Ecology 1: Cox, R.D. nd E.B. llen. 28. Composition of soil seed bnks in southern Cliforni costl sge scrub nd djcent exotic grsslnd. Plnt Ecology 198: Cox, R.D. nd E.B. llen. 28. Stbility of exotic nnul grsses following restortion efforts in southern Cliforni costl sge scrub. Journl of pplied Ecology 45: Cox, R.D. nd E.B. llen The roles of exotic grsses nd forbs when restoring ntive species to highly invded southern Cliforni nnul grsslnd. Plnt Ecology 212: Dickens, S.J.M. 21. Invsive plnt-soil feedbcks nd ecosystem resistnce nd resilience: comprison of three vegettion types in Cliforni. PhD disserttion, University of Cliforni Riverside. Gillespie I.G., nd E.B. llen. 24. Fire nd competition in southern Cliforni grsslnd: impcts on the rre forb Erodium mcrophyllum. Journl of pplied Ecology. 41: Gillespie, I.G. nd E.B. llen. 26. Effects of soil type nd mycorrhize from ntive nd invded vegettion on rre Cliforni forb. pplied Soil Ecology 32:6-12. Gillespie, I.G. nd E.B. llen. 28. Restoring the rre forb Erodium mcrophyllum to exotic grsslnd in southern Cliforni. Endngered Species Reserch 5: Mrushi, R.G. nd E.B. llen Control of exotic nnuls to restore ntive forbs in bndoned griculturl lnds. Restortion Ecology 19: Nelson, L. L., nd E. B. llen Restortion of Stip pulchr grsslnds: effects of mycorrhize nd competition from ven brbt. Restortion Ecology 1:4-5.