Central Asia,located in the innermost part of the Eurasian continent,has experienced“warming and humidification”in recent decades,with potentially important implications for tree growth in alpine forests,which are c...Central Asia,located in the innermost part of the Eurasian continent,has experienced“warming and humidification”in recent decades,with potentially important implications for tree growth in alpine forests,which are critical for regional water reserves.We use nested principal component analysis to assess tree radial growth patterns and reveal significant positive trends since the 20th century across Central Asian alpine forests(0.076 per decade during 1900-2021,p=0.003).Regional hydroclimatic variations affect the greening of these alpine forests,especially with extreme droughts being the most damaging.Growth acceleration is driven by low-latitude warming,which enhances regional temperatures and precipitation.The warming ocean centers alter atmospheric circulation patterns,leading to more moisture being transported to the Central Asian alpine forests,thereby increasing regional precipitation and promoting tree growth.Our model projections indicate that growth rates will continue to rise in the future.However,unprecedented warming may eventually lead to growth deterioration if negative effects,such as insufficient precipitation,occur due to breakdown signs of positive feedback mechanisms,such as moisture transport driven by low-latitude warming.Our study highlights the beneficial,but not unlimited,influences of climate warming on tree growth in Central Asian alpine forests,with implications for the sustainability of water resources.However,as urban and agricultural demands escalate,a holistic,long-term perspective is recommended to mitigate the adverse effects of temperature increases.展开更多
Correlating tree-ring parameters with daily resolved climate data is becoming increasingly common for understanding the complex relationships between tree growth and the surrounding environment.However,with an increas...Correlating tree-ring parameters with daily resolved climate data is becoming increasingly common for understanding the complex relationships between tree growth and the surrounding environment.However,with an increased number of calculated correlations,there is an inherent risk of spurious significance.In this study,we present an analysis using synthetic weather and tree-ring data mimicking the statistical properties of ten real-world sites across Europe to quantify the extent to which numerous comparisons may inflate maximum correlations.Comparisons of different tree-ring proxies,considering varying overlapping period lengths and seasons,revealed 95th percentile correlation differences reaching 0.25 by chance.Using synthetic tree-ring chronologies with an assigned non-signal(r=0.00),spurious correlations can reach statistical significance in over 60%of tests.Correlation inflation is greater when:(1)the climate-proxy relationship is weaker;(2)comparison periods are shorter;and(3)the length of seasonal windows is longer.Autocorrelation in the proxy records does not appear to have a major effect.These findings indicate that caution should be exercised when computing high numbers of correlations with limited observations.We provide tables listing correlation inflations for precipitation-and temperature-sensitive tree-ring chronologies that can inform interpretations of significance.展开更多
基金supported by Excellent Research Group Program for Tibetan Plateau Earth System(continuation grant NSFC project No.41988101)the National Natural Science Foundation of China(Nos.U1803341 and 32061123008)+1 种基金the National Key R&D Program of China(No.2018YFA0606401)the National Youth Talent Support Program.
文摘Central Asia,located in the innermost part of the Eurasian continent,has experienced“warming and humidification”in recent decades,with potentially important implications for tree growth in alpine forests,which are critical for regional water reserves.We use nested principal component analysis to assess tree radial growth patterns and reveal significant positive trends since the 20th century across Central Asian alpine forests(0.076 per decade during 1900-2021,p=0.003).Regional hydroclimatic variations affect the greening of these alpine forests,especially with extreme droughts being the most damaging.Growth acceleration is driven by low-latitude warming,which enhances regional temperatures and precipitation.The warming ocean centers alter atmospheric circulation patterns,leading to more moisture being transported to the Central Asian alpine forests,thereby increasing regional precipitation and promoting tree growth.Our model projections indicate that growth rates will continue to rise in the future.However,unprecedented warming may eventually lead to growth deterioration if negative effects,such as insufficient precipitation,occur due to breakdown signs of positive feedback mechanisms,such as moisture transport driven by low-latitude warming.Our study highlights the beneficial,but not unlimited,influences of climate warming on tree growth in Central Asian alpine forests,with implications for the sustainability of water resources.However,as urban and agricultural demands escalate,a holistic,long-term perspective is recommended to mitigate the adverse effects of temperature increases.
基金supported partly by the ERC Advanced Grant Monostar(AdG 882727)the co funded EU project AdAgriF(CZ.02.01.01/00/22_008/0004635).
文摘Correlating tree-ring parameters with daily resolved climate data is becoming increasingly common for understanding the complex relationships between tree growth and the surrounding environment.However,with an increased number of calculated correlations,there is an inherent risk of spurious significance.In this study,we present an analysis using synthetic weather and tree-ring data mimicking the statistical properties of ten real-world sites across Europe to quantify the extent to which numerous comparisons may inflate maximum correlations.Comparisons of different tree-ring proxies,considering varying overlapping period lengths and seasons,revealed 95th percentile correlation differences reaching 0.25 by chance.Using synthetic tree-ring chronologies with an assigned non-signal(r=0.00),spurious correlations can reach statistical significance in over 60%of tests.Correlation inflation is greater when:(1)the climate-proxy relationship is weaker;(2)comparison periods are shorter;and(3)the length of seasonal windows is longer.Autocorrelation in the proxy records does not appear to have a major effect.These findings indicate that caution should be exercised when computing high numbers of correlations with limited observations.We provide tables listing correlation inflations for precipitation-and temperature-sensitive tree-ring chronologies that can inform interpretations of significance.
