Great Basin Naturalist

Volume 49 Number 4 Article 14

10-31-1989

Arthropod community dynamics in undisturbed and intensively managed mountain brush habitats

Tim A. Christiansen University of Wyoming, Laramie

Jeffrey A. Lockwood University of Wyoming, Laramie

Jeff Powell University of Wyoming, Laramie

Follow this and additional works at: https://scholarsarchive.byu.edu/gbn

Recommended Citation Christiansen, Tim A.; Lockwood, Jeffrey A.; and Powell, Jeff (1989) " community dynamics in undisturbed and intensively managed mountain brush habitats," Great Basin Naturalist: Vol. 49 : No. 4 , Article 14. Available at: https://scholarsarchive.byu.edu/gbn/vol49/iss4/14

This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. ARTHROPOD COMMUNITY DYNAMICS IN UNDISTURBED AND INTENSIVELY MANAGED MOUNTAIN BRUSH HABITATS

1 1 2 Christiansen A. Lockwood , and Jeff Powell Tim A. , Jeffrey

Abstract. —The population dynamics of litter and foliage in undisturbed and intensively managed sagebrush (Artemisia tridentata ) and bitterbrush (Purshia tridentata ) habitats in southeastern Wyoming were assessed bv the measurement of density and the determination of indices of diversity, richness, and evenness. Brush manage- ment consisted of either mowing to a 20-cm stubble or applying the herbicide 2,4-D butyl ester. A total of 63 arthropod species were found in foliage and 150 species in litter. Mowing and herbicide applications resulted in significant changes in the density of 16 of the 46 major arthropod foliage species and 56 of the 70 major litter species. Diversity increased, except in Hymenoptera and Coleoptera, in both mowed and herbicide-treated foliage. In foliage, richness generally increased in all orders following mowing, and evenness tracked diversity. In litter, the diversity of Coleoptera decreased following mowing and herbicide application in Collembola, Homoptera, and Diptera. Evenness followed diversity in trends in both treatments. Soil arthropods were absent in this habitat before and after treatments.

Although extensive studies of arthropod and succession, changes in plant diversity and ecology have been conducted in western resource availability affect diversities grasslands (Blocker et al. 1971, McDaniel (Murdoch et al. 1972, Southwood et al. 1979).

1971, and Kumar et al. 1976), virtually noth- Following a disturbance, early successional

ing is known concerning the role of arthropods stages usually include plants with greater in mountain brush habitats. Sagebrush (Arte- palatability than in either the original habitat misia spp.)-dominated grasslands of the west- or later successional stages (Cates and Orians ern United States cover more than 100 million 1975). The amount and type of litter is also ha (Beetle 1960). Sagebrush is considerably affected by abiotic and biotic factors that may less palatable to livestock than other range be drastically altered by rangeland manage- plants such as annual grasses. For this reason, ment practices. A number of factors influence burning, herbicide applications, and mowing arthropod response to habitat disturbance, in- are commonly used to rid an area of undesir- cluding dispersal, host selection, resource able range plants and have been used in at- availability, litter composition, and vegeta- tempts to eradicate sagebrush (Wright et al. tion recovery (Schowalter 1985). The objec- 1979, Powell 1970). tives of this study were to determine the nor- In addition to direct eradication efforts, ap- mal arthropod taxa and population dynamics proximately 10% of the sagebrush habitat in and to ascertain the immediate impacts of the western United States has been cleared mowing and herbicide application on arthro- habitat. for cultivation and forage production since the pod communities in a mountain brush early 1900s (Beetle 1960). To this end, arthropod populations were mon- itored in the baseline (1985), treatment (1986), Rangeland management practices may and recovery (1987) years in sites that were have significant effects on the arthropod com- either undisturbed or intensively managed. munities in grassland habitats (Morris 1973, Lloyd and Kumar 1977). While it is clear that such disturbances in sagebrush communities Materials and Methods enable economically more desirable annuals to populate range areas, nothing is known This study was conducted on a sagebrush regarding the impact on arthropod popu- (Artemisia tridentata) and bitterbrush (Pur- lations. Habitat disturbance can influence shia tridentata) habitat, located at an eleva- arthropod densities, species distribution, tion of 2,400 m, 12 km southeast of Saratoga, and community diversity. During disturbance Carbon County, Wyoming. The soil is North

'Department of Plant, Soil and Insect Sciences, University of Wyoming. Laramie, Wyoming 82071. 2 Department of Range Management, University of Wyoming, Laramie, Wyoming 82071.

570 October 1989 Christiansen et al. : Arthropod Community Dynamics 571

Park Formation of brown, sandy loams devel- taken from both open and closed areas. Sepa- oped of loess, limestone, sandstone, and tuff. ration of arthropods from the soil was accom- The average yearly precipitation is 48 cm, plished by flotation in a 20% dilute magne- with most of the moisture being provided by sium sulfate solution (Salt and Hollick 1944) or snow. The mean annual temperature is 10.2 a heptane solution (Walter et al. 1987). Also, C, with a range of 21.0 to 27.0 C during the each sample was subdivided and examined sampling period of this study. under a dissecting microscope at 20X to detect Habitat manipulation consisted of either soil arthropods. mowing to a 20-cm stubble height or applying Samples were pooled between seasons and 2,4-D butyl ester in water at a rate of 0.91 kg blocks to provide estimates of ecological in- per acre in June of 1986. Within each treat- dices and the density of each major species ment and control, four blocks of at least 8 ha (i.e., those that accounted for at least 5% of were randomly chosen from sites with similar an order) in foliage, litter, or soil in each vegetation and soil characteristics. treatment and control site. The densities Arthropod samples from foliage, litter, and across treatments were compared using the soil in the control and treatment blocks were protected least significant difference post- collected every 10 days from the end of May ANOVA test. Differences were considered through mid-September in 1985, 1986, and significant at P < .05. Diversity was expressed 1987. Samples were taken along three 100-m using the natural logarithm form of the Shan- transects in each block. The location of the non-Weaver index; evenness was calculated first transect in each block was randomly de- using Pielou's J, and richness was expressed as termined, and the other two transects were the number of species present (Poole 1974). placed 70 m from and parallel to the first transect. The sequence of sampling each Results block was also randomly determined in every sampling period in order to eliminate any The brush management procedures re- chance of systematic errors as a consequence sulted in significant decreases in the total of block location and time of day. shrub cover. Herbicide application reduced Five samples of foliage arthropods were shrub cover to 59% and 57% of the baseline collected from both closed (canopy/shrub- level (which was 30% of the total area before covered) and open (grass-covered) areas along treatment) in the treatment and recovery each transect. Arthropods were collected by years, respectively. Mowing reduced shrub enclosing foliage in a 114 1 plastic container cover to 75% and 72% of the baseline level into which carbon dioxide was released for (which was 32% of the total area before treat- several minutes. A D-vac was then used to ment) in the treatment and recovery years, collect the specimens, which were subse- respectively. Sagebrush was generally re- quently stored at —5 C. duced to a greater extent than bitterbrush. Litter arthropods were collected on the A total of 150 arthropod species were col- same days as foliage arthropods. Five open lected in litter, of which 70 were considered areas and five closed areas were sampled major species (Table 1). Mowing and herbi- along the same transects as were used for cide applications resulted in significant chang- foliage samples. Sampling consisted of collect- es in the density of 57 of these 70 species in the ing all loose litter in a 0.5-m" quadrant. The treatment year. Following mowing, 17 spe- arthropods were separated from the litter in cies significantly decreased and 22 species the laboratory by use of Berlese funnels and significantly increased in density. After herbi- then stored in 70% ethanol. cide treatment, 16 species significantly de- Soil cores for each treatment and block creased and 27 species significantly increased were taken along the same transects as foliage in density. All orders included species that and litter collections. These cores were taken were significantly impacted by management. several days before foliage and litter collec- A total of 63 arthropod species were found tions so that the arthropods would not be dis- in foliage, of which 46 were considered major turbed for foliage collection. A core 10 cm species (Table 2). Mowing and herbicide ap- deep and 5 cm in diameter was taken every 10 plication resulted in significant changes in the m along each transect. Five samples were density of 16 of these 46 species during the 572 Great Basin Naturalist Vol. 49, No. 4

Table 1. Effects of sagebrush/bitterbrush control on litter arthropods. October 1989 574 Great Basin Naturalist Vol. 49, No. 4

Table 1 continued.

Phoridae Megaselia sp. 1985

Chironomidae Chironomus sp.

Sarcophagidae Sarcophaga haemorrhoidalis (Fallen)

Taxigramma heteroneura (Meigen)

Simuliidae Simuliumxum nigricoxum Stone

Otitadae unknown

Scatophagidae Scatophaga stercoraria (L.)

Empididae Platypalpus sutor Rjelander

Hymenoptera

Formicidae Amblypone sp.

Camponotus astus Forel

Cyphomynmex rimosus (Spinola)

Monomorium carbonarium (L.)

Paratrechina vividula (Nylander)

Ponera trigona Mayr.

Solenopsis sp.

Acari Haplozetidae Peloribates europacus William

Peloribates sp. A

Peloribates sp. B October 1989 Christiansen etal.: Arthropod Community Dynamics 575

Table 1 continued.

Orbatulidae 576 Great Basin Naturalist Vol. 49, No. 4

Table 1 continued.

Misumenoides sp. 1985

Misumenoides asperatus (Hentz)

Thomisidae Oxyptila sp. October 1989 Christiansen etal.: Arthropod Community Dynamics 577

Table 2. Effects of sagebrush/bitterbrush control on foliage arthropods.

Density (no./m") a Order/Fami Genus Species Year 578 October 1989 Christiansen etal. ; Arthropod Community Dynamics 579

Table 2 continued.

Formicidae 580 Great Basin Naturalist Vol. 49, No. 4

Table 2 continued.

Oxyopidae Oxyopes

Salticidae

The idae October 1989 Christiansen et al. ; Arthropod Community Dynamics 581

significantly increasing and only one species ment and recovery. Foliage homopteran di- significantly decreasing during the year of dis- versity was greater in treated sites than in turbance. The recovery year had eight litter unmanaged sites but returned to pretreat-

species with significant increases in density ment levels by the recovery year (Table 4). and four species with significant decreases in Richness significantly increased during the density compared with unmanaged sites. treatment year in both herbicide-treated and Aranae included 15% of the litter arthropod mowed sites and significantly decreased in the species. Herbicide application significantly recovery year. decreased density in one of the 10 litter spe- Mowing decreased coleopteran diversity in cies (Table 1). During the recovery year, litter for the disturbance year; however, by three species significantly increased in the recovery year diversity in mowed sites density in both mowed and herbicide-treated was 100% greater than in unmanaged sites (Table sites. Foliage spider densities were not signif- 3). Richness decreased significantly in control icantly affected by mowing until increases oc- and herbicide-treated sites in the re- covery year. In curred in four of the nine major foliage species foliage, coleopteran diversity decreased markedly in herbicide-treated sites during the recovery year (Table 2). Herbicide in the recovery application significantly increased three of the year. Dipteran diversity in litter increased in nine major species during the recovery year. mowed sites in the year of disturbance Diversity, richness, and evenness of Col- but decreased in the other sites. Herbicide- lembola in unmanaged sites increased over treated sites had an increase in diversity by the three-year study (Table 3). Herbicide ap- the recovery year (Table 3). Foliage dipteran plication decreased diversity during the treat- diversity was increased nearly fourfold in the ment year; however, by the recovery year year of mowing but by the recovery year had diversity had surpassed the baseline level. declined to the undisturbed level (Table 4). Likewise, evenness declined during the first Hymenopteran richness, evenness, and year of disturbance but then increased to the diversity in litter decreased in mowed sites in level of unmanaged sites. Mowing increased the recovery year (Table 3). Foliage hy- diversity of springtails during the disturbance menopteran richness increased significantly year and increased both diversity and even- in both mowed and herbicide-treated sites ness during the recovery year. during the year of disturbance. In the recov- Psocoptera appeared in litter in the treat- ery year, richness decreased and diversity in- ment year and diversity decreased markedly creased in mowed and herbicide-treated sites in all sites between the treatment and recov- (Table 4). ery years (Table 3). Diversity and richness of litter Acari de- Thysanuran diversity, richness, and even- clined in all sites in the recovery year (Table ness in sites unmanaged decreased in the 3). The brush management practices had little treatment year but increased in the recovery effect on foliage Acari, relative to changes in year (Table 3). Application of herbicide in- unmanaged sites (Table 4). creased diversity and richness in litter in both Litter populations of Aranea were very the treatment and recovery years. Mowing labile in all sites (Table 3). The diversity of significantly increased richness in the recov- decreased in control and herbicide- ery year. treated sites in the treatment year and then Hemipteran populations did not have suffi- increased markedly in the recovery year. The cient densities for analysis until the recovery decrease in diversity in the treatment year year. Diversity in litter in unmanaged sites was associated with an increase in evenness in was twofold greater than in herbicide-treated herbicide-treated sites but a decrease in even- sites and over threefold greater than in ness in unmanaged sites. The foliage Aranea mowed sites (Table 3). were generally more stabile, although diver- Diversity of homopteran species in litter sity increased in all sites in the recovery year. was increased with mowing and herbicide ap- Richness significantly increased in managed plication in both the treatment and recovery sites in the treatment year. years, compared with the baseline year (Table No arthropods were found in the soil 3). Richness was relatively higher than in the cores below the litter layer in either control or unmanaged sites during the years of treat- treated plots. 582 Great Basin Naturalist Vol. 49, No. 4

Table 3. Diversity, richness, and evenness of arthropod populations in litter and their changes hetween years due to treatments (N 360 samples). October 1989 Christiansen et al.: Arthropod Community Dynamics 583

Table 4. Diversity, richness, and evenness ofarthropod populations in litter and their changes between years due to treatments (N = 360 samples). 584 Great Basin Naturalist Vol. 49, No. 4 degradation of 2,4-D has been shown to in- of the total hemipteran fauna. These crease fungal growth (Klingman and Ashton have been associated with regulating bitter- 1982), and the increased food resources for brush seed production (Basile et al. 1964). collembolan fungivores may have aided popu- Homoptera had peak densities in midsum- lation growth (Poole 1959). Reproductive mer, as was seen in grassland studies by Evans increases of food re- rates can increase when and Murdoch (1968) and McDanief (1971). available (Emilen 1984). sources are made The decrease in population evenness by mid- showed that intense competi- Longstaff (1976) summer indicated that a few species reached tion can change a collembolan system to the relatively high population densities. This in- point that only a few species will become dom- dicated a significant homopteran population Greater competition may have oc- inant. restructuring during peak plant biomass. Fo- curred when the densities of decomposer liage population densities decreased signifi- collembolan species increased through the cantly with disturbance; however, diversity, summer. The recovery year began with a high richness, and evenness all increased. These density, possibly due to either a carryover data indicate that effects from habitat distur- from the treatment year or high reproduction bance may have created more niches in this in spring. Increases in population densities in habitat. Homopteran diversity data from this mowed sites may have resulted from the in- study agreed with results of a study by South- flux of detritus available to litter-inhabiting wood et al. (1979), which showed that insect and litter-consuming springtails. diversity declined after 16 months during sec- Psocopterans were not a major part of the ondary succession in most habitats. arthropod fauna until the third year of the species study in either unmanaged or managed sites. Several predatory coleopteran were litter of sites dur- The increase at the end of the treatment year dominant in the unmanaged loss of hiding was reflected in the recovery year by a high ing most of each summer. The in den- density in unmanaged sites, with a population places in foliage or the decrease prey disturbance have decreased peak in midsummer. This order of arthropods sity due to may feeds upon fungi and small remains of other coleopteran richness. There was only one beetle species in the foliage component after arthropods (Borror et al. 1981). The popula- habi- tion increase by the third year may have been mowing, as compared with seven before enhanced by an increase of fungi resulting tats were disturbed. However, by the end of from 2,4-D degradation. the treatment year, richness and density Thysanura had low population densities greatly increased. Richness nearly reached and richness throughout the three-year study the level of pretreatment, and density in- sixfold. This would indicate that in unmanaged sites. Populations did not re- creased by reestab- spond to herbicide treatment until the recov- foliage coleopteran populations can ery year. The rate of population growth may lish in a short period of time. Reestablishment recovery have increased as more fungal resources be- persisted until late summer of the came available via 2,4-D degradation. year, after which time density and diversity Hemipteran populations were not a major again declined. part of the fauna until the third year. The low Dipteran populations peaked when both diversity and density of Hemiptera for the prey and plant resources were at a maximum,

first two years is difficult to explain, inasmuch as has been found in other studies (Southwood as Kraft (1960) showed a large diversity of this et al. 1979, Lawton 1978). Litter dipteran order occurring in a sagebrush community. populations were affected in herbicide- However, Kraft's (1960) study site was several treated sites. This was also seen in a study by thousand feet lower than our site, and this Ripper (1956) in which pesticides destabilized discrepancy in elevation may have accounted systems. Populations from the foliage compo- for the difference in population parameters. nent appeared to have moved into the litter Although seed production was not assessed, during the treatment year. By the recovery this may also have been a reason for low year, species richness in foliage returned to hemipteran density. There were several spe- the level found in the baseline year, although cies of seed-eating pentatomids within each density remained lower than in any previous treatment, but populations did not exceed 5% vear. —

October 1989 Christiansen etal.: Arthropod Com m unity Dynamics 585

The general decline in density of foliage habitats, and new species of orbatids also ap- Hymenoptera following brush management peared in disturbed sites. This type of colo-

may have been due to a reduction in resources nization was seen by Dindal et al. (1975) in available to ants. Ant species are primarily disturbed old-field habitats. seed gatherers, and, following treatment, Populations of Aranae in foliage fluctuated seeds were not readily available. There was in density, diversity, and richness. One possi- also a decline in the diversity of ant species in ble explanation is the normal fluctuation that midsummer. A phenology study in Wyoming occurs as predator populations track prey pop- by Fisser (1984) showed that plants in sage- ulations (Emilen 1984). brush habitats produce seed in either early or late summer. Ant species present in midsum- Acknowledgments mer were composed of generalist feeders and honeydew-feeding species. The increase in We thank J. C. Burne for assistance with honeydew-feeding ant species coincided with taxonomic identifications, C. C. Burkhardt an increase of aphids. Mowing was more dis- for assistance with pesticide applications, and ruptive than herbicide applications to plant P. Lew for field and laboratory assistance. structure (i.e., protective sites declined This project was partially funded bv USDA- [Juniper and Southwood 1986]), and the re- CSBS Grant 85-CSRS-2-2702. sultant decline in homopteran densities was reflected by decreases in ant populations. In Literature Cited the recovery year, plant regrowth was seen throughout the sites, with a concomi- mowed Basile J v.R H Ferguson vnd M. M. Furniss. 1964. tant increase in ant population indices in Six-legged seed eaters. Idaho Wildlife Review Nov -Dee): 5-7. foliage and a decrease in litter. Thus, ant BEETLE, A A. I960. A study of sagebrush. Wyoming populations apparently moved back into the Agric. Expt. Sta. Bull. .368. 83 pp. foliage component of disturbed sites. Blocker, H D R Reed, and C. E Mason 1971. The order Acari comprised the highest per- Leafhoppers studied at the Osage site (Ho- centage of individuals in the litter component. moptera: Cicadellidae). U.S. IBP Grassland Bioiue Tech. Rept. No. 124. Colorado State Uni- Evenness decreased only slightly while rich- versity, Fort Collins. 25 pp. ness decreased markedly in the recovery year Borror. D J . D M Delong, and C. A. Triplehorn. in unmanaged sites, indicating that with fewer 1981. An introduction to the study of insects. Holt, species in the habitat, there was a more bal- Rhinehart and Winston, New York. 827 pp. anced distribution of individuals among spe- Bi i.anC. A. andC W Barret. 1971. The effects of two acute stresses on the arthropod component of an cies. Herbicide-treated sites had an increase experimental grassland ecosystem. Ecology 52: of mite populations within a month of habitat 597-605. spraying. This density increase may have Cates. R. C. andC H. ORIANS. 1975. Successional status resulted, as in other fungivorous arthro- and the palatability of plants to generalized herbi- vores. Ecology 56: 410-418. pods, from the consequences of 2,4- D degra-

Dindal, D L . D P Schwert, and R. A. Norton 1975. dation. Dindal et al. saw a decrease in (1975) Effects of sewage effluent disposal on community richness of mites when a grassland habitat was structure of soil invertebrates. Pages 391-427 in disturbed. Their work with orbatid mites indi- J. Vanek, ed., Progress in soil zoology. Junk, The Hague. 630 cated, as did this study, that simplification pp. Emilen. M 1984. Population biology: the coevolution within the acarine community resulted from J of population dynamics and behavior. MacMillan, reduction to of richness due management New York. 547 pp. practices. The recovery year had increases in Evans. F. C, and W. W. Murdoch 1968. Taxonomic ecological parameters of foliage mites, which composition, trophic structure and seasonal occur- rence in a grassland insect community. may have been initiated by overcrowding in J. Ecol. 37: 259-273. litter, to the point that mites began to move Fisser. H. G. 1984. Biology and ecology of sagebrush in toward areas of low density. Movement of Wyoming. Pages 314-319 in E. D. McArthurand mites from a high-density to a lower-density B. L. Welch, eds.. III. Phenology. Proceedings Symposium on the biology of Artemisia and habitat has been shown to occur in other sys- Chrysothamnus. Provo, Utah. 398 pp. tems (Morris 1971, Varley et al. 1973). Or- Juniper. B , and R Southwood. 1986. Insects and batid mites, which comprised a large portion the plant surface. Edward Arnold, Great Britain. of the mite community, colonized disturbed 360 pp. 586 Great Basin Naturalist Vol. 49, No. 4

Lawrence KUNGMAN, C C, AND F. M Ashton 1982. Weed science: Ovington, J. D., D. Heitkamp, and D R principles and practices. Wiley-Interscience, 1963. Plant biomass and productivity of prairie, New York. 431 pp. savanna, oakwood and maize field ecosystems in 52-63. Kraft, G F 1960. Insects affecting bitterbrush and other central Minnesota. Ecology 44: quantitative range plants. Unpublished office report, Oregon Poole, R W 1974. An introduction to ecol- ogy. McGraw-Hill, New York. 532 State College. 56 pp. pp. Lloyd, and R E Pfadt. Poole, T R 1959. Studies on the food of Collembola in a Kumar, R , R J Lavigne, J E Douglas-fir plantation. Proc. Zool. Soc. London 1976. Insects of the Central Plains Experimental 132:71-81. Range, Pawnee National Grassland. Agric. Expt. Powell, 1970. Site factor relationships with volatile Sta. Sci. Monogr. 32. University of Wyoming. J oils in big sagebrush. Range Manage. 23: 42-46. 74 pp. J. Ripper. E. 1956. Effect of pesticides on balance of influences on insect W Lawton, J H. 1978. Host-plant arthropod populations. Ann. Rev. Entomol. 1: diversity: the effects of time and space. Pages 403-438. 105-126 in L. A. Mound and N. Waloff eds., Salt, G ., and F. S Hollick. 1944. Studies of wireworm Diversity of insect faunas. Proceedings of the J populations. Ann. Appl. Riol. 31: 53-64. Royal Entomological Society of London. 220 pp. Schowalter, T, D 1986. Adaptations of insects to distur- Lloyd. E., and R Kumar. 1977. Root feeding insects of J. bance. Pages 235-251 in S. T. A. Pickett and P. S. a shortgrass prairie and their responses to grazing White, eds., The ecology of natural disturbance pressure and ecosystem stresses. Pages 267-272 and patch dynamics. Academic Press, New York. in K. Marshall, ed.. The belowground ecosys- J. 472 pp. tem: a synthesis of plant-associated processes. Southwood, T. R E , V K Rrown, and P M Reader Range Sci. Dept. Sci. Series No. 26. 351 pp. 1979. The relationships of plant and insect diversi- Longstaff, R. C. 1976. The dynamics of collembolan ties in succession. Riol. J. Linn. Soc. 12: 327-348. relationships in an ex- populations: competitive 1979. Varley, G C , G R Gradwell, and M. P Reader perimental system. Canadian Zool. 54: 948- J. Insect population ecology: an analytical approach. 962. Rlackwell, Oxford. 212 pp. McDaniel, R. 1971. Studies of populations of adult and 1987. hep- Walter, D E , J Kethly, and J. C Moore. A immature insects and mites from two treatments tane flotation method for recovering micro- at Cottonwood, South Dakota. U.S. IRP Grass- arthropods from semiarid soils, with comparison land Riome Tech. Rept. No. 112. Colorado State to the Merchant-Crossely high-gradient method University, Fort Collins. 79 pp. and estimates of microarthropod biomass. Pedobi- Morris. M. G. 1973. The effects of seasonal grazing on the ologia 30: 221-232. (Hemiptera) Rrit- Heteroptera and Auchenorrhvncha Wright, H A , L F Neuenschwander, andC M 761-780. of chalk grassland. J. Appl. Ecol. 10: tan 1979. The role and use of fire in sagebrush- grass and pinyon-juniper plant communities. A Murdoch. W W , F C Evans, and C H Peterson 1972. Diversity and patterns in plants and insects. state of the art review. USDA Forest Service Gen. Ecology 53: 819-829. Tech. Rept. Int. 178 pp.