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Accueil du site → Doctorat → États-Unis → 1974 → The significance of the subterranean termite, Heterotermes aureus (Snyder), as a detritivore in a desert grassland ecosystem

University of Arizona (1974)

The significance of the subterranean termite, Heterotermes aureus (Snyder), as a detritivore in a desert grassland ecosystem

Haverty, Michael Irving

Titre : The significance of the subterranean termite, Heterotermes aureus (Snyder), as a detritivore in a desert grassland ecosystem

Auteur : Haverty, Michael Irving

Université de soutenance : University of Arizona

Grade : Doctor of Philosophy (PhD) 1974

Résumé partiel
To evaluate the efficien cy of the subterranean term ite, Heterotermes aureus (Snyder), in removing sup erficial dead wood from a desert grassland ecosystem the follow ing parameters were examined : 1) size and dispersion of foraging populations, 2) production and a v a ila b ility of wood, 3) wood consumption rates, 4) preferences in selection of wood and 5) environmental control of foraging a c tiv ity . Field experiments were carried out in a shrub-invaded desert grassland ecotone on the Santa Rita Experimental Range, ca. 40 km south of Tucson, Arizona. F ifty randomly located c irc u la r quadrats were sampled to study relationships between term ite populations and wood abundance. A b a it sampling technique provided inform ation on environmental control of term ite foraging a c tiv ity , number of foragers, colony density and foraging te rrito rie s . Laboratory wood consumption rates were established using six constant temperatures and four wood species. A simple computer model was developed to synthesize results and to evaluate th is term ite’s ro le as a d e tritiv o re in th is ecosystem. From c irc le d ra t data i t is estimated th at there were 160 foraging groups or colonies per hectare and an average of 68,918 foraging term ites per hectare at any given moment during the year of study. There were an estimated 181 colonies and an average o f 37,800 foraging term ites per hectare as determined by the b a it samplingtechnique. Average colony foraging te rrito ry was 13.14 m . Foraging groups consisted of 97.2 percent larva-w orkers, 1.5 percent soldiers and 1.3 percent nymphs, larvae and pre-soldiers. Numbers or biomass of term ites was generally not correlated with amount of wood availab le. Standing crop biomass of superficial dead wood on the study s ite is 2127 kg per hectare. Five plant species represent 97.6 per cent of the biomass. Six plant species account fo r 96.4 percent of the 450 kg per hectare of sup erficial dead wood produced annually. Wood consumption by H. aureus is best described as a lin e a r or quadratic function re la tiv e to temperature. Maximum consumption occurred between 28 and 32°C regardless of wood species and a s ig n ific a n tly greater amount of blue palo verde, C. floridum , was con sumed than the other three wood species. H. aureus is a general feeder yet appears to prefer ch o lla, mesquite and catclaw over blue palo verde and other less abundant woods. This contrasts with its a b ility to consume s ig n ific a n tly greater amounts o f C. floridum in compulsory feeding tr ia ls . Surface foraging occurs throughout the year between 7 and 47°C, extreme temperatures between the food-soil interface and 15 cm in the s o il. Increased soil moisture increases foraging in te n s ity . Number of foragers on the b a it sampling grid at a given point in time may be predicted by the equation : In Y = -0.985 - 0.0761 T + 2.928 In T + 0.327 In R where Y = number of foragers at th at tim e, T = d aily mean temperature at food-soil interface and R = d aily r a in fa ll.


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