Uni vc l'sity of Califomia ; Dep a l'tm ent of Soil and Environme nt a l Sc ie nce, Univc l'sity ... more Uni vc l'sity of Califomia ; Dep a l'tm ent of Soil and Environme nt a l Sc ie nce, Univc l'sity of Califomi lt Summary P he nological studies concerning d ese r t pllmts h ave b een fe w especially In the case of phreato• phytic taxa. H e r e we r e port on a investiga tion of t h e season"l pl'ogress ion of phenologi cal cbarac• teristics on c urrent season shoots of ProsoJJi8 gtancltdo8o , a phreatophytic taxon found in t he sou thern Californi a d eserts. Growth ch a racteri sti cs a re divided into "Leaf pools" and "Flux Hates" a nd they are correlated with seasmml climatic conditions. R a t e of growth functions we l'e r a pid and of sh o l•t dumtion. T wo gl'Owth per' iods occurred with sf'veral different structur'al and phe nological ch " l'acte ri sti cs based on the clim atic conditions in which the shoots of each gl"Owth p e riod w e re produced. Maximum leaf a t'elt was maintained on the Prosopis trees throughout the most str essful p e riod o f t h e ye,u'. L ea r ab sc ission was a bmpt OCCUI " ring just b efore leaves of th e n e xt year 's g ro wth w ere pl'Oriu CE'd. Pro8opis phe nology was b est co r• r elated w ith water ava ilability a nd moisture stress. Pro8opis giancluto8a in Routhe m Califol'l1ia h its an unus ua l phen ological system in r ela tion to other d ese l't taxa which may re f! ct the ge neral phenolog y of p hl'eato phytic taxa. Research is cont inuing on Prosopis in a compamtive m a nn er with oth er ph,'eatophytic sp ecies.
A nematode, Scottnema lindsayae, is the dominant metazoan found in soils of the McMurdo Dry Valle... more A nematode, Scottnema lindsayae, is the dominant metazoan found in soils of the McMurdo Dry Valleys, Antarctica. The distribution of S. lindsayae is patchy within and between these dry valleys; nevertheless, it is unclear to what extent these populations are genetically isolated. We investigated genetic diversity in this nematode using nuclear and mitochondrial gene sequences that encode ribosomal RNA. In 169 nematodes surveyed, only one variable site was found in each of two different expansion segments of nuclear rRNA. While most nematodes have only one sequence type, some nematodes were found to contain a mixture of both sequences. No fixed differences in nuclear sequences were observed between populations. This pattern of nuclear variation is most consistent with a single species of nematode defined morphologically as S. lindsayae. For mitochondrial DNA sequences, we found 10 variable positions defining 12 haplotypes among 188 nematodes surveyed. While all observed haplotypes ar...
... Bonney Basin, Taylor Valley, 77°44′, 162°19′, 110, 0.19±0.06, 0.03±0.03, 0.28±0.03, 7598 e. ... more ... Bonney Basin, Taylor Valley, 77°44′, 162°19′, 110, 0.19±0.06, 0.03±0.03, 0.28±0.03, 7598 e. ... Sublimation of subsurface ice, ... Stable isotope composition of contemporary soil organic matter in these various systems reveals potential inputs of mixed source materials including lake ...
Passive open‐top devices have been proposed as a method to experimentally increase temperature in... more Passive open‐top devices have been proposed as a method to experimentally increase temperature in high‐latitude ecosystems. There is, however, little documentation on the efficacy of these devices. This paper examines the performance of four open‐top chambers for altering temperature at six sites in the Arctic and Antarctica. Most of the heating effect was due to daytime warming above ambient; occasional night‐time cooling below ambient, especially of air temperatures, depressed mean daily temperature. The mean daily temperatures at four arctic sites were generally increased by 1.2–1.8 °C; but occasionally, temperature depressions also occurred. Under optimal conditions at the antarctic site (dry soils, no vegetation, high radiation) mean daily soil temperatures were increased by +2.2 °C (–10 cm) to +5.2 °C (0 cm). Protection from wind may play a more important role than temperature per se in providing a favourable environment for plant growth within open‐top devices. Wind speed had...
Once thought of as inert, ice has been increasingly recognized as a habitat suitable for life. Th... more Once thought of as inert, ice has been increasingly recognized as a habitat suitable for life. The landscape of the MCMurdo Dry Valleys (MCM) of Antarctica is dominated by glaciers, and glacier melt is the primary water source for life in soils, streams, and lakes. The glaciers, despite their cold and lifeless appearance, offer functioning habitats for life. The major objective of this study was to examine biogeochemical characteristics of miniecosystems present in cryoconite holes and to determine links to other components (soils, streams, and lakes) of the dry valley landscape. We examined cryoconite holes from 5 glaciers spanning the length of Taylor Valley, one of many valleys in the MCM. Cryoconite biotic communities were composed of the same species observed in streams and lakes, namely, cyanobacteria (Chlorococcus, Chroococcus, Crinalium, Oscillatoria, Nostoc, and Sprirulina), rotifers (Philodina gregaria and Cephalodella catellina), tardigrades (Acutuncus antarcticus and Hypsibius spp.), and ciliates. Biotic communities did not reflect the composition of the immediately surrounding environments, suggesting the effects of eolian mixing and transport of sediments and biota across the valley. Gradients of chemistry and biotic abundance in cryoconite holes reflected the position of each glacier in the valley. Nitrogen and organic carbon concentration patterns across glaciers potentially resulted from biological activities in cryoconite holes. Properties of holes were stable from one to the next sampling season, suggesting that changes of cryoconite hole properties develop on longer than yearly time scales. water to streams and perennially ice-covered lakes. Taylor Valley, the site of the MCM Long-Term Ecological Research (LTER) project, is approximately 34 km long and 12 km wide. About one-third of the valley is covered by glaciers, which supply the water to the ephemeral streams and perennially ice-covered lakes (Fountain et al., 1999). Three lake basins (Fryxell, Hoare, and Bonney)
Abstract This report describes the general behaviour patterns, spacing patterns and alarm vocaliz... more Abstract This report describes the general behaviour patterns, spacing patterns and alarm vocalizations of California ground squirrels ( Spermophilus beecheyi ) as observed in three successive springs of research. Functions are suggested for most behaviour patterns. Males maintain home ranges relatively exclusive of other males via site-specific aggression. Female home ranges overlap extensively with those of other females, and defence is confined to the immediate vicinity of the burrow. Both sexes respond to avian and mammalian predators with relatively predator-specific vocalizations.
Ensuring the accuracy of age estimation in fisheries science through validation is an essential s... more Ensuring the accuracy of age estimation in fisheries science through validation is an essential step in managing species for long-term sustainable harvest. The current study used Δ14 C in direct validation of age estimation for queen triggerfish Balistes vetula and conclusively documented that triggerfish sagittal otoliths provide more accurate and precise age estimates relative to dorsal spines. Caribbean fish samples (n = 2045) ranged in size from 67–473 mm fork length (FL); 23 fish from waters of the southeastern U.S. (SEUS) Atlantic coast ranged in size from 355–525 mm FL. Otolith-based age estimates from Caribbean fish range from 0–23 y, dorsal spine-based age estimates ranged from 1–14 y. Otolith-based age estimates for fish from the SEUS ranged from 8–40 y. Growth function estimates from otoliths in the current study (L∞ = 444, K = 0.13, t0 = -1.12) differed from spined-derived estimates in the literature. Our work indicates that previously reported maximum ages for Balistes ...
Uni vc l'sity of Califomia ; Dep a l'tm ent of Soil and Environme nt a l Sc ie nce, Univc l'sity ... more Uni vc l'sity of Califomia ; Dep a l'tm ent of Soil and Environme nt a l Sc ie nce, Univc l'sity of Califomi lt Summary P he nological studies concerning d ese r t pllmts h ave b een fe w especially In the case of phreato• phytic taxa. H e r e we r e port on a investiga tion of t h e season"l pl'ogress ion of phenologi cal cbarac• teristics on c urrent season shoots of ProsoJJi8 gtancltdo8o , a phreatophytic taxon found in t he sou thern Californi a d eserts. Growth ch a racteri sti cs a re divided into "Leaf pools" and "Flux Hates" a nd they are correlated with seasmml climatic conditions. R a t e of growth functions we l'e r a pid and of sh o l•t dumtion. T wo gl'Owth per' iods occurred with sf'veral different structur'al and phe nological ch " l'acte ri sti cs based on the clim atic conditions in which the shoots of each gl"Owth p e riod w e re produced. Maximum leaf a t'elt was maintained on the Prosopis trees throughout the most str essful p e riod o f t h e ye,u'. L ea r ab sc ission was a bmpt OCCUI " ring just b efore leaves of th e n e xt year 's g ro wth w ere pl'Oriu CE'd. Pro8opis phe nology was b est co r• r elated w ith water ava ilability a nd moisture stress. Pro8opis giancluto8a in Routhe m Califol'l1ia h its an unus ua l phen ological system in r ela tion to other d ese l't taxa which may re f! ct the ge neral phenolog y of p hl'eato phytic taxa. Research is cont inuing on Prosopis in a compamtive m a nn er with oth er ph,'eatophytic sp ecies.
A nematode, Scottnema lindsayae, is the dominant metazoan found in soils of the McMurdo Dry Valle... more A nematode, Scottnema lindsayae, is the dominant metazoan found in soils of the McMurdo Dry Valleys, Antarctica. The distribution of S. lindsayae is patchy within and between these dry valleys; nevertheless, it is unclear to what extent these populations are genetically isolated. We investigated genetic diversity in this nematode using nuclear and mitochondrial gene sequences that encode ribosomal RNA. In 169 nematodes surveyed, only one variable site was found in each of two different expansion segments of nuclear rRNA. While most nematodes have only one sequence type, some nematodes were found to contain a mixture of both sequences. No fixed differences in nuclear sequences were observed between populations. This pattern of nuclear variation is most consistent with a single species of nematode defined morphologically as S. lindsayae. For mitochondrial DNA sequences, we found 10 variable positions defining 12 haplotypes among 188 nematodes surveyed. While all observed haplotypes ar...
... Bonney Basin, Taylor Valley, 77°44′, 162°19′, 110, 0.19±0.06, 0.03±0.03, 0.28±0.03, 7598 e. ... more ... Bonney Basin, Taylor Valley, 77°44′, 162°19′, 110, 0.19±0.06, 0.03±0.03, 0.28±0.03, 7598 e. ... Sublimation of subsurface ice, ... Stable isotope composition of contemporary soil organic matter in these various systems reveals potential inputs of mixed source materials including lake ...
Passive open‐top devices have been proposed as a method to experimentally increase temperature in... more Passive open‐top devices have been proposed as a method to experimentally increase temperature in high‐latitude ecosystems. There is, however, little documentation on the efficacy of these devices. This paper examines the performance of four open‐top chambers for altering temperature at six sites in the Arctic and Antarctica. Most of the heating effect was due to daytime warming above ambient; occasional night‐time cooling below ambient, especially of air temperatures, depressed mean daily temperature. The mean daily temperatures at four arctic sites were generally increased by 1.2–1.8 °C; but occasionally, temperature depressions also occurred. Under optimal conditions at the antarctic site (dry soils, no vegetation, high radiation) mean daily soil temperatures were increased by +2.2 °C (–10 cm) to +5.2 °C (0 cm). Protection from wind may play a more important role than temperature per se in providing a favourable environment for plant growth within open‐top devices. Wind speed had...
Once thought of as inert, ice has been increasingly recognized as a habitat suitable for life. Th... more Once thought of as inert, ice has been increasingly recognized as a habitat suitable for life. The landscape of the MCMurdo Dry Valleys (MCM) of Antarctica is dominated by glaciers, and glacier melt is the primary water source for life in soils, streams, and lakes. The glaciers, despite their cold and lifeless appearance, offer functioning habitats for life. The major objective of this study was to examine biogeochemical characteristics of miniecosystems present in cryoconite holes and to determine links to other components (soils, streams, and lakes) of the dry valley landscape. We examined cryoconite holes from 5 glaciers spanning the length of Taylor Valley, one of many valleys in the MCM. Cryoconite biotic communities were composed of the same species observed in streams and lakes, namely, cyanobacteria (Chlorococcus, Chroococcus, Crinalium, Oscillatoria, Nostoc, and Sprirulina), rotifers (Philodina gregaria and Cephalodella catellina), tardigrades (Acutuncus antarcticus and Hypsibius spp.), and ciliates. Biotic communities did not reflect the composition of the immediately surrounding environments, suggesting the effects of eolian mixing and transport of sediments and biota across the valley. Gradients of chemistry and biotic abundance in cryoconite holes reflected the position of each glacier in the valley. Nitrogen and organic carbon concentration patterns across glaciers potentially resulted from biological activities in cryoconite holes. Properties of holes were stable from one to the next sampling season, suggesting that changes of cryoconite hole properties develop on longer than yearly time scales. water to streams and perennially ice-covered lakes. Taylor Valley, the site of the MCM Long-Term Ecological Research (LTER) project, is approximately 34 km long and 12 km wide. About one-third of the valley is covered by glaciers, which supply the water to the ephemeral streams and perennially ice-covered lakes (Fountain et al., 1999). Three lake basins (Fryxell, Hoare, and Bonney)
Abstract This report describes the general behaviour patterns, spacing patterns and alarm vocaliz... more Abstract This report describes the general behaviour patterns, spacing patterns and alarm vocalizations of California ground squirrels ( Spermophilus beecheyi ) as observed in three successive springs of research. Functions are suggested for most behaviour patterns. Males maintain home ranges relatively exclusive of other males via site-specific aggression. Female home ranges overlap extensively with those of other females, and defence is confined to the immediate vicinity of the burrow. Both sexes respond to avian and mammalian predators with relatively predator-specific vocalizations.
Ensuring the accuracy of age estimation in fisheries science through validation is an essential s... more Ensuring the accuracy of age estimation in fisheries science through validation is an essential step in managing species for long-term sustainable harvest. The current study used Δ14 C in direct validation of age estimation for queen triggerfish Balistes vetula and conclusively documented that triggerfish sagittal otoliths provide more accurate and precise age estimates relative to dorsal spines. Caribbean fish samples (n = 2045) ranged in size from 67–473 mm fork length (FL); 23 fish from waters of the southeastern U.S. (SEUS) Atlantic coast ranged in size from 355–525 mm FL. Otolith-based age estimates from Caribbean fish range from 0–23 y, dorsal spine-based age estimates ranged from 1–14 y. Otolith-based age estimates for fish from the SEUS ranged from 8–40 y. Growth function estimates from otoliths in the current study (L∞ = 444, K = 0.13, t0 = -1.12) differed from spined-derived estimates in the literature. Our work indicates that previously reported maximum ages for Balistes ...
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