Moss functioning in different taiga ecosystems in interior Alaska

Skre, O.; Oechel, Walter C.

doi:10.1007/bf00346987

Cited by 133 publications

(47 citation statements)

References 19 publications

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“…This result is consistent with the absence of a significant interaction between treatment and DOY for SGR (Table 3). In both treated and untreated plots, Sphagnum growth was stimulated by elevated soil temperatures and dry conditions, a result that has been documented previously (Skre and Oechel 1981;Sonesson et al 2002;Dorrepaal et al 2004Dorrepaal et al , 2006Gunnarsson 2005;Breeuwer et al 2008;Lang et al 2009). However, we did not see a significant difference in soil moisture between treatments.…”

Section: Discussionsupporting

confidence: 73%

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Growth responses of Sphagnum hollows to a growing season lengthening manipulation in Alaskan Arctic tundra

et al. 2012

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The global increase in surface air temperature has produced an overall lengthening of the growing season by 3-5 days/decade in the Northern Hemisphere during the last 30 years. The direct impact of a longer growing season has not been well documented for Sphagnum moss communities in the Arctic. We hypothesized that an increase in the growing season length may be detrimental to Sphagnum growth as a result of photoinhibition caused by the plants emerging from snow near the seasonal peak of solar irradiance. We conducted an experiment from 1999 to 2002, lengthening the growing season in arctic Alaska, to determine the effects that this simulation of climate change had on the growth of hollows dominated by Sphagnum angustifolium. The lengthened growing season was associated with a decrease in annual moss height increment of 78 and 69 % for 1999 and 2000, respectively. These growth reductions may be related to freeze/thaw episodes and prolonged periods of cold in those years. The growth of individuals exposed to snow removal was also reduced by high global radiation. Overall, snow removal did not significantly affect the seasonal dynamics of growth, but seasonal patterns of growth strongly differed among years. These differences in seasonal dynamics suggest that Sphagnum growth is driven by opportunistic responses to favorable conditions rather than ontogenetic drivers. In addition, we compared environmental variation and growth between control and snow removal plots. Growth of Sphagnum in both treatments was stimulated by warmer soil temperatures and drier conditions. With earlier snowmelt as a result of warmer temperatures, it is likely that S. angustifolium will be subjected to higher levels of radiation and possibly greater photoinhibition which may lead to lower growth rates and significant implications for moss production in tussock tundra.

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Section: Discussionsupporting

confidence: 73%

“…Previous studies from interior Alaska have shown that the positive effect of a rain event depends on the length of the preceding dry period (Skre and Oechel 1981). Therefore, the proportion of dry days (PDD), that is, days without precipitation, was computed.…”

Section: Environmental Datamentioning

confidence: 99%

Growth responses of Sphagnum hollows to a growing season lengthening manipulation in Alaskan Arctic tundra

et al. 2012

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“…Such knowledge is important in view of the consequences of possible future climatic changes : higher atmospheric CO # concentrations will be followed by from desiccation ; and in response to repeated desiccation. Earlier studies (Skre & Oechel, 1981 ;Titus, Wagner & Stephens, 1983 ;Silvola & Aaltonen, 1984 ;Rydin & McDonald, 1985 b ;Murray et al, 1989) showed no general differences in photosynthetic response to low tissue water contents between hummock and hollow species, and differences in desiccation tolerance seemed not to be related to the natural microhabitat of the species (Clymo, 1973 ;Sagot & Rochefort, 1996). This study concentrates on the effects of repeated desiccation.…”

Section: mentioning

confidence: 93%

“…Recovery of net photosynthesis after repeated desiccation (1997) Recovery was rather poor in Experiment 1, so a different design was used to test the effect of repeated desiccation. To imitate alternating wetting-drying cycles, the complete moss carpet in the plastic cylinders in the growth chamber was allowed to dry out several times for 60 h and in between was rewetted for 12 h. The capitula were cut before rewetting and gas exchange measurements were made (Skre & Oechel, 1981). New capitula from the moss-cylinders were used for each measurement.…”

Section: Experiments 1 Recovery Of Net Photosynthesis After Repeated mentioning

confidence: 99%

Response of photosynthesis of Sphagnum species from contrasting microhabitats to tissue water content and repeated desiccation

1998

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The response of photosynthetic CO # exchange to tissue water content in five spp. of Sphagnum from contrasting microhabitats (S. fuscum (Schimp.) Klinggr., S. papillosum H. Lindb., S. magellanicum Brid., S. balticum (Russ.) C. Jens. and S. cuspidatum Ehrh. ex Hoffm.) was measured in the laboratory using an infrared gas analyser technique. Experiments were designed to test recovery of net photosynthesis after periodic and long lasting desiccation.The contact between capitula and basal parts of the mosses seems to be important for survival. Isolated capitula cut off from any contact with the water table were not able to recover after complete desiccation (at 15 mC for 2-4 d). When contact with the water table is lost, e.g. during long periods of desiccation, recovery of net photosynthesis can take place but only if the water content of the capitula does not fall too far below c. 10-20 % of the water content at compensation point.There was no relationship between the ability of net photosynthesis to recover from desiccation and the wetness of the natural microhabitat. Sphagna survive dry periods by avoidance of drying out by high capillarity or dense growth form (as in S. fuscum). Key words : CO# exchange, photosynthesis, desiccation, recovery, Sphagnum. Peat mosses (Sphagnum) cover large areas in the boreal regions, especially on bogs (ombrotrophic mires). Bogs are characterized by a conspicuous microtopography, consisting of hummocks and hollows, formed by the mosses. Different species occupy different levels above the water table. Earlier studies on the interactions among hollow and hummockinhabiting Sphagnum spp. were reviewed by Rydin (1993 a). The present study aims to give an understanding of water relations and desiccation tolerance among different Sphagnum spp. in ecophysiological terms. Such knowledge is important in view of the consequences of possible future climatic changes : higher atmospheric CO # concentrations will be followed by

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“…Though Robroek et al (2007b) did find greater height increment and production at 20°C than at 15°C for several Sphagnum species, their experiment lasted for only 6 months. Harley et al (1989) and Skre and Oechel (1981) showed that photosynthesis in Sphagnum increases with temperature up to an optimum around 20-25°C. The absence of a response to temperature in our experiment may indicate that the maximum photosynthetic rates of Sphagnum were already reached at the average temperatures of 17.4 and 21.7°C we used.…”

Section: Temperaturementioning

confidence: 99%

Response of Sphagnum species mixtures to increased temperature and nitrogen availability

et al. 2009

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To predict the role of ombrotrophic bogs as carbon sinks in the future, it is crucial to understand how Sphagnum vegetation in bogs will respond to global change. We performed a greenhouse experiment to study the effects of two temperature treatments (17.5 and 21.7°C) and two N addition treatments (0 and 4 g N m -2 year -1 ) on the growth of four Sphagnum species from three geographically interspersed regions: S. fuscum, S. balticum (northern and central Sweden), S. magellanicum and S. cuspidatum (southern Sweden). We studied the growth and cover change in four combinations of these Sphagnum species during two growing seasons. Sphagnum height increment and production were affected negatively by high temperature and high N addition. However, the northern species were more affected by temperature, while the southern species were more affected by N addition. High temperature depressed the cover of the 'wet' species, S. balticum and S. cuspidatum. Nitrogen concentrations increased with high N addition. N:P and N:K ratios indicated P-limited growth in all treatments and co-limitation of P and K in the high N treatments. In the second year of the experiment, several containers suffered from a severe fungal infection, particularly affecting the 'wet' species and the high N treatment. Our findings suggest that global change can have negative consequences for the production of Sphagnum species in bogs, with important implications for the carbon sequestration in these ecosystems.

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Moss functioning in different taiga ecosystems in interior Alaska

Cited by 133 publications

References 19 publications

Growth responses of Sphagnum hollows to a growing season lengthening manipulation in Alaskan Arctic tundra

Growth responses of Sphagnum hollows to a growing season lengthening manipulation in Alaskan Arctic tundra

Response of photosynthesis of Sphagnum species from contrasting microhabitats to tissue water content and repeated desiccation

Response of Sphagnum species mixtures to increased temperature and nitrogen availability

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