Aims Boreal forest is the largest and contains the most soil carbon among global terrestrial biomes.Soil respiration during the prolonged winter period may play an important role in the carbon cycles in boreal forests...Aims Boreal forest is the largest and contains the most soil carbon among global terrestrial biomes.Soil respiration during the prolonged winter period may play an important role in the carbon cycles in boreal forests.This study aims to explore the characteristics of winter soil respiration in the boreal forest and to show how it is regulated by environmental factors,such as soil temperature,soil moisture and snowpack.Methods Soil respiration in an old-growth larch forest(Larix gmelinii Ruppr.)in Northeast China was intensively measured during the winter soilfreezing process in 2011 using an automated soil CO_(2) flux system.The effects of soil temperature,soil moisture and thin snowpack on soil respiration and its temperature sensitivity were investigated.Important Findings Total soil respiration and heterotrophic respiration both showed a declining trend during the observation period,and no significant difference was found between soil respiration and heterotrophic respiration until the snowpack exceeded 20cm.Soil respiration was exponentially correlated with soil temperature and its temperature sensitivity(Q10 value)for the entire measurement duration was 10.5.Snow depth and soil moisture both showed positive effects on the temperature sensitivity of soil respiration.Based on the change in the Q10 value,we proposed a‘freeze–thaw critical point’hypothesis,which states that the Q10 value above freeze–thaw critical point is much higher than that below it(16.0 vs.3.5),and this was probably regulated by the abrupt change in soil water availability during the soil-freezing process.Our findings suggest interactive effects of multiple environmental factors on winter soil respiration and recommend adopting the freeze–thaw critical point to model soil respiration in a changing winter climate.展开更多
Population responses to envir on mental extremes often dictate the bounds to species' distributions. However, population dynamics at, or near, those range limits may also be affected by sublethal effects. We expos...Population responses to envir on mental extremes often dictate the bounds to species' distributions. However, population dynamics at, or near, those range limits may also be affected by sublethal effects. We exposed late instars and pupae of an invasive leafroller, Epiphyaspostvittana (Walker)(Lepidoptera: Tortricidae), to cold temperatures and measured the effects of exposure on subsequent survivorship, development, and reproduction. Cold temperature was applied as acute exposure to -10 °C (a low, but not immediately lethal temperature for this species) or the onset of freezing (the peak of the supercooling point exotherm). Survival was defined as the ability to successfully eclose as an adult. We measured immature development times, pupal mass, and adult longevity as proxies of fitness in survivors. Additionally, surviving insects were mated with individuals that had not been exposed to cold to measure fertility. There was no difference between the proportion of larvae or pupae that survived acute exposure to -10 °C and those exposed to the control temperature. Approximately 17% of larvae and 8% of pupae survived brief periods with internal ice formation and continued development to become reproductively viable adults. Importantly, surviving the onset of freezing came with significant fitness costs but not to exposure to -10 °C;most insects that survived partial freezing had lower fertility and shorter adult lifespans than either the -10 °C or control group. These results are discussed within the context of forecasting invasive in sect distributions.展开更多
基金National Natural Science Foundation of China(31021001)National Basic Research Program of China on Global Change(2010CB950600)Ministry of Science and Technology(2010DFA31290).
文摘Aims Boreal forest is the largest and contains the most soil carbon among global terrestrial biomes.Soil respiration during the prolonged winter period may play an important role in the carbon cycles in boreal forests.This study aims to explore the characteristics of winter soil respiration in the boreal forest and to show how it is regulated by environmental factors,such as soil temperature,soil moisture and snowpack.Methods Soil respiration in an old-growth larch forest(Larix gmelinii Ruppr.)in Northeast China was intensively measured during the winter soilfreezing process in 2011 using an automated soil CO_(2) flux system.The effects of soil temperature,soil moisture and thin snowpack on soil respiration and its temperature sensitivity were investigated.Important Findings Total soil respiration and heterotrophic respiration both showed a declining trend during the observation period,and no significant difference was found between soil respiration and heterotrophic respiration until the snowpack exceeded 20cm.Soil respiration was exponentially correlated with soil temperature and its temperature sensitivity(Q10 value)for the entire measurement duration was 10.5.Snow depth and soil moisture both showed positive effects on the temperature sensitivity of soil respiration.Based on the change in the Q10 value,we proposed a‘freeze–thaw critical point’hypothesis,which states that the Q10 value above freeze–thaw critical point is much higher than that below it(16.0 vs.3.5),and this was probably regulated by the abrupt change in soil water availability during the soil-freezing process.Our findings suggest interactive effects of multiple environmental factors on winter soil respiration and recommend adopting the freeze–thaw critical point to model soil respiration in a changing winter climate.
基金the National Science Foundation-Integrative Graduate Education and Research Traineeship on Introduced Species and Genotypes program at the University of Minnesota (DGE-0653827)the US Department of Agriculture-Forest Service. We thank Dr.N. Caruthers (USDA-APH1S)providing insect egg masses and the MAES-MDA Biosafety Level 2 staff for quarantine facility support.
文摘Population responses to envir on mental extremes often dictate the bounds to species' distributions. However, population dynamics at, or near, those range limits may also be affected by sublethal effects. We exposed late instars and pupae of an invasive leafroller, Epiphyaspostvittana (Walker)(Lepidoptera: Tortricidae), to cold temperatures and measured the effects of exposure on subsequent survivorship, development, and reproduction. Cold temperature was applied as acute exposure to -10 °C (a low, but not immediately lethal temperature for this species) or the onset of freezing (the peak of the supercooling point exotherm). Survival was defined as the ability to successfully eclose as an adult. We measured immature development times, pupal mass, and adult longevity as proxies of fitness in survivors. Additionally, surviving insects were mated with individuals that had not been exposed to cold to measure fertility. There was no difference between the proportion of larvae or pupae that survived acute exposure to -10 °C and those exposed to the control temperature. Approximately 17% of larvae and 8% of pupae survived brief periods with internal ice formation and continued development to become reproductively viable adults. Importantly, surviving the onset of freezing came with significant fitness costs but not to exposure to -10 °C;most insects that survived partial freezing had lower fertility and shorter adult lifespans than either the -10 °C or control group. These results are discussed within the context of forecasting invasive in sect distributions.
