For plant populations to persist,seedling recruitment is essential,requiring seed germination,seedling survival and growth.Drought and grazing potentially reduce seedling recruitment via increased mortality and reduce...For plant populations to persist,seedling recruitment is essential,requiring seed germination,seedling survival and growth.Drought and grazing potentially reduce seedling recruitment via increased mortality and reduced growth.We studied these seederelated processes for two species indigenous to the Pamir Mountains of Xinjiang in northwestern China:Saussurea glacialis and Plantago lessingii.Seeds collected from Taxkorgan,Xinjiang,had a viability rate of 15.8%for S.glacialis but 100%for P.lessingii.Of the viable seeds,the highest germination rates were 62.9%for S.glacialis and 45.6%for P.lessingii.In a greenhouse experiment,we imposed a series of stressful conditions,involving a combination of simulated grazing and drought events.These had the most severe impact on younger seedlings.Modelling showed that 89%of S.glacialis mortality was due to early simulated grazing,whereas 80%of P.lessingii mortality was due to early simulated drought.Physiological differences could contribute to their differing resilience.S.glacialis may rely on water storage in leaves to survive drought events,but showed no shifts in biomass allocation that would improve grazing tolerance.P.lessingii appears more reliant on its root system to survive grazing,but the root reserves of younger plants could be insufficient to grow deeper in response to drought.After applying all mortality factors,17.7 seedlings/parent of P.lessingii survived,while only<0.1 seedlings/parent of S.glacialis survived,raising concerns for its capacity to persist in the Pamirs.Inherent genetic differences may underlie the two species’contrasting grazing and drought responses.Thus,differing conservation strategies are required for their utilization and protection.展开更多
Mercury（Hg） remains a key contaminant of concern in Arctic biota, and monitoring of Hg concentrations in seabird tissues will be an effective approach to track the effects of implementing the Minamata Convention. We...Mercury（Hg） remains a key contaminant of concern in Arctic biota, and monitoring of Hg concentrations in seabird tissues will be an effective approach to track the effects of implementing the Minamata Convention. We examined trends in total Hg（THg） in liver and egg tissues of two Arctic seabirds, thick-billed murres（Uria lomvia） and northern fulmars（Fulmarus glacialis）, between 1976 and 2013 to assess whether both tissues showed similar patterns of Hg change. Hepatic THg was consistently higher than egg THg, and both species had similar egg THg concentrations, but fulmars had higher hepatic THg than murres.Murre THg concentrations showed more relative variation through time than fulmars.We suggest that egg THg better reflects exposure of birds to THg in local, Arctic prey,whereas liver THg may incorporate longer term, year-round THg exposure. Additional analysis of THg distribution in Arctic seabirds post-laying would help inform interpretation of long-term trends.展开更多
基金a Yunnan Provincial Human Resources and Social Security Bureau Post-Doctoral GrantChinese Academy of Sciences President’s International Fellowship Initiative grant[grant number 2020FYC0003]+1 种基金the National Sciences Foundation China[grant number 41661144001]the Key Research Program of Frontier Sciences[grant number QYZDY-SSW-SMC014].
文摘For plant populations to persist,seedling recruitment is essential,requiring seed germination,seedling survival and growth.Drought and grazing potentially reduce seedling recruitment via increased mortality and reduced growth.We studied these seederelated processes for two species indigenous to the Pamir Mountains of Xinjiang in northwestern China:Saussurea glacialis and Plantago lessingii.Seeds collected from Taxkorgan,Xinjiang,had a viability rate of 15.8%for S.glacialis but 100%for P.lessingii.Of the viable seeds,the highest germination rates were 62.9%for S.glacialis and 45.6%for P.lessingii.In a greenhouse experiment,we imposed a series of stressful conditions,involving a combination of simulated grazing and drought events.These had the most severe impact on younger seedlings.Modelling showed that 89%of S.glacialis mortality was due to early simulated grazing,whereas 80%of P.lessingii mortality was due to early simulated drought.Physiological differences could contribute to their differing resilience.S.glacialis may rely on water storage in leaves to survive drought events,but showed no shifts in biomass allocation that would improve grazing tolerance.P.lessingii appears more reliant on its root system to survive grazing,but the root reserves of younger plants could be insufficient to grow deeper in response to drought.After applying all mortality factors,17.7 seedlings/parent of P.lessingii survived,while only<0.1 seedlings/parent of S.glacialis survived,raising concerns for its capacity to persist in the Pamirs.Inherent genetic differences may underlie the two species’contrasting grazing and drought responses.Thus,differing conservation strategies are required for their utilization and protection.
基金provided by Environment and Climate Change Canadathe Northern Contaminants Program of IndigenousNorthern Affairs Canada (1617-HQ-000221)
文摘Mercury（Hg） remains a key contaminant of concern in Arctic biota, and monitoring of Hg concentrations in seabird tissues will be an effective approach to track the effects of implementing the Minamata Convention. We examined trends in total Hg（THg） in liver and egg tissues of two Arctic seabirds, thick-billed murres（Uria lomvia） and northern fulmars（Fulmarus glacialis）, between 1976 and 2013 to assess whether both tissues showed similar patterns of Hg change. Hepatic THg was consistently higher than egg THg, and both species had similar egg THg concentrations, but fulmars had higher hepatic THg than murres.Murre THg concentrations showed more relative variation through time than fulmars.We suggest that egg THg better reflects exposure of birds to THg in local, Arctic prey,whereas liver THg may incorporate longer term, year-round THg exposure. Additional analysis of THg distribution in Arctic seabirds post-laying would help inform interpretation of long-term trends.
