Food Arthropod Abundance Associated with Rest-Rotation Livestock Grazing. Hayes B. Goosey. Department of Animal and Range Sciences

Transcription

1 Food Arthropod Aundnce Associted with Rest-Rottion Livestock Grzing Hyes B. Goosey Deprtment of Animl nd Rnge Sciences Montn Stte University We hve completed the second seson of investigtion into the response of food rthropods of sge-grouse to rest rottion grzing s implemented y the Sge-grouse Inititive (SGI) in centrl Montn. We collected oth pitfll trp nd sweep net smples to most ccurtely estimte oth ground nd vegettion dwelling rthropod undnces. These dt presented here represent n Order view nd were tulted from specimens collected using pitfll trps which represents the ctivity densities of ground dwelling tx. We did identify ll specimens to Fmily nd some to Species, which my dd necessry resolution to nlyses. Furthermore, we lso deployed sweep net smpling to collect weekly undnces of ove ground nd more vegettion dwelling rthropods. The tx collected using sweeps re more representtive of song-irds food items nd will help to complete the entire picture of rthropod undnce, diversity, nd ctivity in sgerush steppe hitts. We lso collected dt on vegettion structure nd species frequency t our trpping loctions. Anlyses of those dt re forthcoming. Sge-grouse chicks re nerly dependent on food rthropods s sole energy source during the first 21 to 28 dys of life (erly rooding period). Our initil reserch ojective ws to evlute if the SGI rest rottion grzing progrm influences the undnce nd diversity. Therefore, our pst two field sesons focused on smpling nd cpturing key food rthropods from pstures which were either rested/deferred or grzing y livestock during the erly rooding period of lte My to erly July of ech field seson. The rthropods we clssified s food for sge-grouses chicks re: Beetles (Coleopter) Butterfly nd Moth immtures (Lepidopter lrve) Grsshoppers nd Crickets (Orthopter) Spiders (Arnee) Ants (Hymenopter: Formicide) The report which follows in not comprehensive in wht will e our finl efforts to effectively summrize these dt; rther it is lrge picture view of the pst two field sesons. The intent of this report is to provide ll individuls nd entities oth privte nd pulic with scientific evidence on which to engge in dete on how to conserve sge-grouse nd sge-rush steppe hitts while keeping livestock on the lndscpe nd fmily rnches profitle. Without profitle rnch opertions on the lndscpe, sge-rush steppe hitts re highly thretened for conversion to frming opertion. To egin, verge rthropod ctches, cross ll tx, were gretest from trpping loctions locted in rested/deferred pstures when compred to ctches from loctions in pstures contining livestock during 12 (Fig. 1 A) nd 13 (Fig. 1 B). At this point it is uncler wht mechnism is driving this difference nd further nlyses our dt while incorporting vegettive structure nd diversity nd nnul environmentl fctors my elucidte further understnding. Although food rthropod ctches were gretest in rested/deferred pstures, discrepncies did

2 occur etween smpling yers nd tx within smpling yer. For exmple, in 12, Beetle (Coleopter) ctches were gretest in rested/deferred pstures (Fig. 1 C); however no differences were recorded in 13 (Fig. 1 D). In contrst, ctches of Butterfly nd Moth immtures (Lepidopter lrve) from loctions in rested/deferred nd grzed pstures did not differ in 12 (Fig. 1 E); however more Butterfly nd Moth immtures were collected from loctions in rested/deferred pstures in 13 (Fig. 1 F). The undnce of Grsshoppers nd Crickets etween rested/deferred nd grzed loctions did not differ in either yer of investigtion (Fig. 1 G & H). The undnces of Spiders (Arnee) nd Ants (Hymenopter: Formicide) did not differ etween rested/deferred nd grzed loctions in 12 (Fig. 1 I; Fig. 1 K); however more spiders nd nts were collected from loctions in rested/deferred pstures in 13 (Fig. 1 J; Fig. 1 L). Polynomil regressions suggest tht the gretest food rthropod undnce is ssocited with live grss heights etween pproximtely 13 nd 32 cm (Fig. 2 A), sge-rush heights of 3 to 52 cm (Fig. 2 B), nd res with less thn percent re ground (Fig. 2 C). Incresed sgerush height lso correltes significntly nd positively with rthropod undnce. Tller vegettive structure correlting with incresed rthropod undnce could e due to oth grsses nd rthropods eing ectothermic nd develop sed on ccumulte het; with wrmer tempertures producing more rpid spring time development nd growth when compred to reltively cooler tempertures. Alterntively, tller vegettive structure, in generl, should produce fvorle microclimtes grdients t the site level llowing rthropods to more effectively thermo-regulte. Also, vegettive structure could indicte chnge in one or severl life cycle events of ground dwelling rthropods including, ut not limited to, reproductive, predtor voidnce, or food cquisition requirements. Soil nutrient differences, should they exist, could lso ply significnt role with res of reltively greter nutrients or incresed nutrient vilility producing incresed plnt nd susequent rthropod diversities nd undnces. The percentge of re ground on the lndscpe is lso significnt prt of rthropod undnce in tht s re ground increses ove %, rthropod undnce decreses. Liner regressions suggest similr reltionships exist etween totl rthropod ctches nd live grss height (Fig. 3 A) nd live sgerush height (Fig. 3 B); however R 2 vlues re lower thn reported for polynomil reltionships. To the contrry, liner reltionship does not exist etween totl ctches nd the percent re ground t ech smpling loction (Fig. 3 C). From livestock production perspective, no grzing system hs een shown to e universlly superior to ny other in terms of its ility to enhnce livestock production. As results, grzing systems like rest rottion cn e eneficil to rnge conditions nd livestock opertions if the percentge of re ground is decresed. This not only increses the crrying cpcity (AUMs) nd potentil net returns for livestock enterprises ut s evidenced in this report it ppers to potentilly increse the conservtion vlue for selected food rthropods of sge-grouse chicks. These results suggest tht rested/deferred pstures hror n incresed undnce of food rthropods nd given tht rested pstures lso exhiit tller residul vegettive structure it is possile tht deferment during erly rooding my increse chick survivorship. On lndscpe scle, however, pstures which re either grzed or rested/deferred during the erly rooding period represent vrying percentges of the totl lndscpe. How rthropod undnces in pstures which re neither rested/deferred nor grzed during erly rood rering remins unknown t this time. Lstly, nlyzing the rthropod diversities etween pstures my provide dditionl evidence on which sound lnd mngement decisions cn e mde.

3 All Tx A. Grzed Pstures Rested Pstures 3 Grzed pstures Rested pstures B. ) 3 Yer Men p =.2 28-My July-13 Yer Men p <.1 Coleopter (Beetles) C. D Yer Men p <.1 28-My July-13 Yer Men p =.44 Lepidopter Lrve (Butterfly nd Moth Cterpillrs) E. F. 8 8 Yer Men p =.2 28-My July-13 Yer Men P <.1

4 Orthopter (Grsshoppers nd Crickets) G. H Grzed Pstures Rested Pstures Grzed Pstures Rested Pstures Yer Men p = My July-13 Yer Men p =.91 Arnee (Spiders) I. J. 8 8 es Yer Men p = My July-13 Yer Men p =.2 Hymenopter: Formicide (Ants) K. L Yer Men p = July-13 Yer Men p <.2 Fig. 1. Averged ctches cross ll tx (A & B), Coleopter (C & D), Lepidopter (E & F), Orthopter (G & H), Arnee (I & J), nd Hymenopter: Formicide (K & L) during 12 (left column) nd 13 (right column) in pstures which were either rested/deferred or grzed during the erly rooding period of lte My to erly July. Lines represent the verge weekly ctches, rs represent the verged ctch for the smpling yer, nd error rs represent the SEM.

5 A. 3 2 Totl Ctches 1 R 2 =.27 p <.1 3 Grss Height (cm) B. 3 2 Totl Ctches 1 R 2 =.19 p < Sge rush height (cm) C. 3 2 Totl Ctches 1 R 2 =. p < Bre Ground (%) Fig. 2. Polynomil reltionships (solid lines), with 95% confidence intervls (dshed lines), etween the totl pitfll trp ctches collected cross ll dtes nd A) live grss height, B) live sgerush height, nd C) percent re ground from smpling loctions locted in rested/deferred nd livestock grzed pstures. The reltionship of ech regression is highly significnt (p-vlue); however the predictive cpility (R 2 ) of ech eqution is low.

6 A. 3 2 Totl Ctches 1 R 2 =.21 p <.1 3 Grss Height (cm) B. 3 2 Totl Ctches 1 R 2 =.14 p < Sgerush Height (cm) C. 3 2 Totl Ctches 1 R 2 =.2 p =.13 8 Breground (%) Fig. 3. Liner reltionships (solid lines), with 95% confidence intervls (dshed lines), etween the totl pitfll trp ctches cross ll dtes nd A) live grss height, B) live sgerush height, nd C) percent re ground t ech of the smpling loctions collected from oth rested/deferred nd livestock grzed pstures. The liner reltionships etween live grss nd sgerush heights nd totl rthropods ctches re highly significnt (p-vlue); however the predictive cpility (R 2 ) of ech regression eqution is low. The liner reltionship etween the percentge of re ground nd the totl sesonl ctches is not significnt.