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Types of Vegetation in the San Joaquín Valley of California and Their Relation to the Beet Leafhopper

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Types of Vegetation in the San Joaquín Valley of California and Their Relation to the Beet Leafhopper TECHNICAL BULLETIN NO. 557 JUNE 1937 TYPES OF VEGETATION IN THE SAN JOAQUÍN VALLEY OF CALIFORNIA AND THEIR RELATION TO THE BEET LEAFHOPPER By R. L. PIEMEISEL Physiologist Division of Sugar Plant Investigations Bureau of Plant Industry and F. R. LAWSON Junior Entomologist Division of Truck Crop and Garden Insects Bureau of Entomology and Plant Quarantine UNITED STATES DEPARTMENT OF AGRICULTURE, WASHINGTON, D. C. For lale by the Superintendent of Documenti. Washington, D. C Price 10 cenu Technical Bulletin No. 557 June 1937 UNITED STATES DEPARTMENT OF AGRICULTURE WASHINGTON, D. C. TYPES OF VEGETATION IN THE SAN JOAQUÍN VALLEY OF CALIFORNIA AND THEIR RELATION TO THE BEET LEAFHOPPER By R. L. PiEMEiSEL, physiologist, Division of Sugar Plant Investigations, Burean of Plant industry, and F. R. LAWSON, junior entomologist, Division of Truck Crop and Garden Insects, Bureau of Entomology and Plant Quarantine ^ CONTENTS Page Introduction 1 Types of vegetation—Continued. Definition of types of vegetation and their Plant communities along washes and relationships 3 stream beds 16 Relation of types of vegetation to climate and Plant communities of minor importance.. 17 topography 4 Changes in weedy plant cover _ 18 Types of vegetation ^ 6 Principal species of present plant cover 20 Tree savanna 6 Possibilities of reduction of weedy areas and Pacific grassland 8 the effect on leafhopper population and curly Desert saltbush 10 top damage 24 Spiny saltbush 13 Summary 27 Lowland types 14 Literature cited 28 INTRODUCTION Earlier studies by a number of investigators have determined that in the San Joaquin Valley of California the virus disease curly top causes damage every year to sugar beets, tomatoes, beans, melons, and squash, as well as to other truck crops and to ornamental plants, and that severe crop losses have occurred in years of high population of the beet leafhopper {Eutettix tenellus (Baker)), only known vector of the curly top disease. The life history and general movements of the leafhopper are also known. In the spring at the time of the drying of winter annuals on the range lands of the western side of the valley, the insect moves clown into the valley onto green summer annuals or onto crops, where it remains during the summer. In the fall, at the time of harvesting beets and when the summer annuals dry, the leafhopper moves back to the range lands onto 1 The authors are indebted to Eubanks Carsner, senior pathologist, Division of Sugar Plant Investigations, Bureau of Plant Industry, and W. C. Cook, entomologist, Division of Truck Crop and Garden Insects, Bureau of Entomology and Plant Quarantine, for suggestions during the course of the work and for their criticism of the manuscript ; also to the late A. S. Hitchcock, principal botanist, and Agnes Chase, associate botanist, Divi- sion of Plant Exploration and Introduction, Bureau of Plant Industry, for identification of the grasses, and to S. F. Blake, senior botanist, and Ivar Tidestrom, formerly assistant botanist, of the latter division, for identifying plants other than grasses. 112826°—37 1 1 2 TECHNICAL BULLETIN 5 5 7, U. S. DEPT. OF AGRICULTURE whatever host plants are green and feeds on these until the winter rains again bring on the growth of winter annuals. When this study was begun it was not known whether the present breeding grounds and food supplies of the beet leafhopper were static in loca- tion and area or whether they were temporary in nature and might be subject to great changes in both location and area. It has recently been shown by Piemeisel (8)- that the annuals serving as spring and summer hosts do not form a large part of the original vegetation in the southern Idaho area, that their great abundance is the result of overgrazing and abandonment of plowed lands, and that if abandonment ceased and grazing were restricted the host plants would be replaced by nonhost plants, chiefly grasses, and eventually by the original vegetation. A similar situation exists in the San Joaquín Valley. However, since the reestablishment of the original vegetation, and also to some extent the stands of host plants, depended on what the original type had been, it was neces- sary to know, insofar as possible, the extent and composition of the present vegetation and of the original types. This information was not available in published works. Jeps(}n (5) gives the zonal arrangement, a brief description, and the principal species of some of the types in California, but most of these are at a higher altitude than the area considered here. Other authors, mentioned later, discussed one or more of the types with the characteristic species. No detailed maps of the vegetation oí the valley were available. Accordingly, the types of original vegetation were reconstructed a« far as they could be from the studies made, and their probable bound- aries were mapped (fig. 1). The present vegetation was also mapped (figs. 2 and 3). In the following pages each of the principal orig- inal types, shown on the map, is briefly described. The derivation of present stands from the original, through modification or destruc- tion, is also discussed, as well as the relation of the present stands of each particular type to the beet leafhopper. To show these inter- relationships for the valley as a whole, a diagrammatic representa- tion was made (fig. 4). The more important relationships are dis- cussed in more detail later. To facilitate the use of figure 4, the names of the plants used are here given in full: Desert saltbush, also known as allscale {Atnplex folycarpa (Torr.) S. Wats.) ; spiny saltbush, also known as spine- scale (Atriplex spinifera Macbride) ; bract scale (A. hracteosa S. Wats.) ; saltgrass {DisticMis npicata (L.) Greene) ; Kussian-thistle {Salsola pestifer A. Neis.) ; seepweed, also known as alkali blite (Dondia moquini (Torr.) A. Neis.) ; alkali heath (Frankenia grandi- folia C. and S.) ; and pickleweed {AUenroIfea occidentalis (S. Wats.) Kuntze). The following treatment of the types of vegetation is far from complete from a broad ecological viewpoint, since features closely related to the beet leafhopper are stressed and others omitted. Never- theless it is hoped that the information given may be of use to future investigators of the plants and animals of the section and that it will fill a need such as that experienced by the writers when the present study was begun. 2 Italic numbers In parentheses refer to Literature Cited, p. 28. imuUITree Savanna ^3 Desert Soitbush E^Pacific Gross I ond ^S! Spiny Soltbush ES] Lowland Types Scale of mi les o 5 10 15 FiacBE 1,—Map showing jirinoipal oriKinal types of vegetation in the San Joaquín Valley» (Coiiilai-e with fig. 2.) 112Si:(i°—37 (!■"«<•'■ p. 2) No. 1 ^Winter Annuals ^Desert SoItbush QUID] Form Land ^ Spiny Soltbush ES Lowlond Types Scale of miles IIii'i I I 0 5 10 15 FiocRE 2.—Map of Togetation of the San Joaciuin Valley as it is at present. The boundary lines were drawn from surveys in addition to those made from the original vegetation types. Solid lines indicate boundaries actually surveyed. Dotted Unes show estimated boundaries Ijttwren parts surveyed. (Mapped by F. B. Lawson.) 112820=—37 -Far-ep. 2) X.,. 2 O FOGWEED C BRACT SCALE {Atriplex expanse) (A. bracfeosa) • RUSSIAN-THISTLE (Sa/so/c7 pesfifer) Each dof represents 500 ocres Scale of miles FiGCHE 3.—Map slio^iug tiistribution of su:!;nier weed hosT.s in 1933. 1128-0°^-37 iFa-,<'i'--) N'J. •; VEGETATION IN THE SAN JOAQUÍN VALLEY 3 DEFINITION OF TYPES OF VEGETATION AND THEIR RELATIONSHIPS Throughout this bulletin the common terms "weedy areas" and "types of original vegetation" are used. "Weedy areas" refers to the s !» aj OK ^ " ^ " ¿ •"* 'S 0^*^^ i- t*!? Í3 & S3 -t- OJ L- Oí a t" c: >i'^ Q; .-a [í " S ^ a> ;t; a = g 3¿ o .a SE '1' i ^ o :3 3.5 i 5 = £ ii^e M ■!», .g-,Sä'Ss o B^.g g a Î 1- „Sg"55ilo = « CO? »i~ ÏÏ.5 'ij -— M "íí — 'S y » O) «¿ 0 = »coas o^jWaj g O.S "a--j3^ Se csogoaS jojg ÏVo;'^*-'- t- t- ci; CÖ Q_A2?^g'Sï5£ I. î 3ï5oi-raS |='r£Î.S=Sco roi' c-::;c r-> NOI1V13D3A •^•- o'ïï a ? ^ o^; a >d3ddOHJV31 IVNßläO temporary plant communities, the early stages of secondary succes- sions, composed of annuals. The various stages (subseres) of the secondary successions and the deflecting or arresting of the develop- ment at a uarticular stage are discussed later (p. 18). The term "types of original vegetation" refers to the stabilized plant communities composed principally of perennials. "Original 4 TECHNICAL BULLETIN 5 5 7, U. S. DEPT. OF AGRICULTUEE vegetation" is used to designate the vegetation as it existed preceding the intensive disturbances caused by the white man. The "types' are tlie stabilized units that together formed the original vegetation. Their composition and extent are reconstructed insofar as possible for the period given above. The San Joaqnin Valley is a meeting place of the desert forma- tions of the interior, the Mohave and Colorado Deserts, and the grassland and broad sclerophyll formations of the Pacific slope. The outline given below shows the relation of the units of vegetation of this valley to the classifications made by previous investigators for the sections just mentioned. Cooper (5), who dealt chiefly with the Coast Eange area, divided the broad scleroplij-ll vegetation into the broad sclei'ophyll formation and the chaparral formation. The tree savanna of this bulletin is probably a nearly related, more arid form of his Qnei'(.'UH agrifolm-lohata association included in the broad sclerophyll formation. Clements {2) classifies the grassland as a Stipa-Poa association of the Stipa-Bouteloua formation.
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