Researching into changes in thermal growing season has been one of the most important scientific issues in studies of the impact of global climate change on terrestrial ecosystems. However, few studies investigated th...Researching into changes in thermal growing season has been one of the most important scientific issues in studies of the impact of global climate change on terrestrial ecosystems. However, few studies investigated the differences under various definitions of thermal growing season and compared the trends of thermal growing season in different parts of China. Based on the daily mean air temperatures collected from 877 meteorological stations over northern China from 1961 to 2015, we investigated the variations of the thermal growing season parameters including the onset, ending and duration of the growing season using the methods of differential analysis, trend analysis, comparative analysis, and Kriging interpolation technique. Results indicate that the differences of the maximum values of those indices for the thermal growing season were significant, while they were insignificant for the mean values. For indices with the same length of the spells exceeding 5°C, frost criterion had a significant effect on the differences of the maximum values. The differences of the mean values between frost and non-frost indices were also slight, even smaller than those from the different lengths of the spells. Temporally, the starting date of the thermal growing season advanced by 10.0–11.0 days, while the ending dates delayed by 5.0–6.0 days during the period 1961–2015. Consequently, the duration of the thermal growing season was prolonged 15.0–16.0 days. Spatially, the advanced onset of the thermal growing season occurred in the southwestern, eastern, and northeastern parts of northern China, whereas the delayed ending of the thermal growing season appeared in the western part, and the length of the thermal growing season was prolonged significantly in the vast majority of northern China. The trend values of the thermal growing season were affected by altitude. The magnitude of the earlier onset of the thermal growing season decreased, and that of the later ending increased rapidly as the altitude increased, causing the magnitude of the prolonged growing season increased correspondingly. Comparing the applicability of selected indices and considering the impacts of frost on the definitions are important and necessary for determining the timing and length of the thermal growing season in northern China.展开更多
Given the short duration of growing season in the Arctic, a strong correlation between plant productivity and growing season length (GSL) is conventionally assumed. Will this assumption hold true under a warming clima...Given the short duration of growing season in the Arctic, a strong correlation between plant productivity and growing season length (GSL) is conventionally assumed. Will this assumption hold true under a warming climate? In this study, we addressed the question by investigating the relationship between net primary productivity of leaves (NPP<sub>leaf</sub>) and GSL for various tundra ecosystems. We quantified NPP<sub>leaf</sub> and GSL using long-term satellite data and field measurements. Our results indicated that the relationship was not significant (i.e., decoupled) for 44% to 64% of tundra classes in the southern Canadian Arctic, but significant for all classes in the northern Canadian Arctic. To better understand the causes of the decoupling, we further decomposed the relationship into two components: the correspondence of interannual variations and the agreement of long- term trends. We found that the longer the mean GSL for a tundra class, the poorer the correspondence between their interannual variations. Soil moisture limitation further decoupled the relationship by deteriorating the agreement of long-term trends. Consequently, the decoupling between NPP<sub>leaf</sub> and GSL would be more likely to occur under a warming climate if the tundra class had a mean GSL > 116 (or 123) days with a dry (or moist) soil moisture regime.展开更多
The climate change in Alaska has caused earlier spring snowmelt and the growing season expanded. However, the effect of climate change on crop phenological stages, heading (BBCH 55) and maturity (BBCH 85), is unknown....The climate change in Alaska has caused earlier spring snowmelt and the growing season expanded. However, the effect of climate change on crop phenological stages, heading (BBCH 55) and maturity (BBCH 85), is unknown. In this study, the trends of growing-season length (GSL), phenological stages of crops and climatic parameters, and the correlations between climatic parameters and the phenological stages were analyzed using the climate data and crop data over the period of 1978 to 2016. The longer GSL was found in Fairbanks (64.83<span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span></span>N, 147.77<span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span></span>W) and in Delta Junction (64.05<span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span>N, 145.60<span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span>W) but not in Palmer (61.60<span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span>N, 149.11<span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span>W). Sowing dates did not change significantly in three locations. The decreasing trends of heading and maturity of crops were observed but varied with location. Heading of barley and oat significantly advanced 3 and 3.1 d decade<sup>-1</sup>, respectively from 1989 to 2016 in Fairbanks while no change of heading was observed in Delta Junction and Palmer. Maturity of barley, oat and wheat significantly advanced 2.6, 3.8 and 3.9 d decade<sup>-1</sup>, respectively from 1978 to 2016 in Fairbanks (<em>P</em> < 0.05);maturity of oat and wheat significantly advanced 4.4 and 3.4 d decade<sup>-1</sup> from 1978 to 2015, respectively in Delta Junction (<em>P</em> < 0.05). The increasing temperature trends and decreasing precipitation trends were found in Fairbanks and Delta Junction but varied with phenological stages of crops. Sowing was more important for heading than for maturity of crops. The effect of climate change on heading was less important than that on maturity. Earlier maturity of crops in Fairbanks may be attributed to increased temperatures, that in Delta Junction to both increased minimum temperature and decreased precipitation and that in Palmer to temperature and precipitation.展开更多
草地广泛分布于干旱区和半干旱区,对季节性气候变化的响应十分敏感,但目前针对草地物候对季节性气候变化响应的研究仍较为薄弱。文章以内蒙古为例,基于不同草地类型的NDVI数据,辅以动态阈值、趋势分析和偏相关方法研究了2001—2020年草...草地广泛分布于干旱区和半干旱区,对季节性气候变化的响应十分敏感,但目前针对草地物候对季节性气候变化响应的研究仍较为薄弱。文章以内蒙古为例,基于不同草地类型的NDVI数据,辅以动态阈值、趋势分析和偏相关方法研究了2001—2020年草地物候时空动态、变化趋势及其随海拔梯度、气温和降水变化特征。结果表明内蒙古地区:(1)随纬度、海拔升高,草地生长季始期(start of growing season,SOS)逐渐推迟,生长季末期(end of growing season,EOS)缓慢推迟,生长季长度(length of growing season,LOS)呈不规律性变化趋势。(2)SOS集中在4月上旬到5月下旬,71.3%呈显著提前趋势,速率为0~2.0 d/a。EOS集中在9月下旬到10月中旬,69.98%呈推迟趋势。LOS持续在110~230 d,50.31%呈变长趋势。(3)在海拔500~2500 m的区域,随海拔上升,SOS推迟、EOS提前、LOS延长。(4)SOS与夏、秋、冬的气温为显著负相关关系,与春、秋、冬降水为显著负相关关系,与春季气温和夏季降水呈显著的正相关关系。EOS与春、夏、秋降水以不显著负相关性为主,与冬季降水以不显著正相关为主,与四季气温以负相关关系为主。LOS与春、夏、冬气温以负相关为主,秋季气温与LOS的正负相关参半。以上研究结果对内蒙古草地生长监测和应对气候异常提出保护策略、制定行之有效的防灾减灾措施、构建稳定的生态屏障具有指导意义。展开更多
基金supported by the National Natural Science Foundation of China(41571044,41401661,41001283)the Climate Change Special Fund of the China Meteorological Administration(CCSF201716)the China Clean Development Mechanism(CDM)Fund Project(2012043)
文摘Researching into changes in thermal growing season has been one of the most important scientific issues in studies of the impact of global climate change on terrestrial ecosystems. However, few studies investigated the differences under various definitions of thermal growing season and compared the trends of thermal growing season in different parts of China. Based on the daily mean air temperatures collected from 877 meteorological stations over northern China from 1961 to 2015, we investigated the variations of the thermal growing season parameters including the onset, ending and duration of the growing season using the methods of differential analysis, trend analysis, comparative analysis, and Kriging interpolation technique. Results indicate that the differences of the maximum values of those indices for the thermal growing season were significant, while they were insignificant for the mean values. For indices with the same length of the spells exceeding 5°C, frost criterion had a significant effect on the differences of the maximum values. The differences of the mean values between frost and non-frost indices were also slight, even smaller than those from the different lengths of the spells. Temporally, the starting date of the thermal growing season advanced by 10.0–11.0 days, while the ending dates delayed by 5.0–6.0 days during the period 1961–2015. Consequently, the duration of the thermal growing season was prolonged 15.0–16.0 days. Spatially, the advanced onset of the thermal growing season occurred in the southwestern, eastern, and northeastern parts of northern China, whereas the delayed ending of the thermal growing season appeared in the western part, and the length of the thermal growing season was prolonged significantly in the vast majority of northern China. The trend values of the thermal growing season were affected by altitude. The magnitude of the earlier onset of the thermal growing season decreased, and that of the later ending increased rapidly as the altitude increased, causing the magnitude of the prolonged growing season increased correspondingly. Comparing the applicability of selected indices and considering the impacts of frost on the definitions are important and necessary for determining the timing and length of the thermal growing season in northern China.
文摘Given the short duration of growing season in the Arctic, a strong correlation between plant productivity and growing season length (GSL) is conventionally assumed. Will this assumption hold true under a warming climate? In this study, we addressed the question by investigating the relationship between net primary productivity of leaves (NPP<sub>leaf</sub>) and GSL for various tundra ecosystems. We quantified NPP<sub>leaf</sub> and GSL using long-term satellite data and field measurements. Our results indicated that the relationship was not significant (i.e., decoupled) for 44% to 64% of tundra classes in the southern Canadian Arctic, but significant for all classes in the northern Canadian Arctic. To better understand the causes of the decoupling, we further decomposed the relationship into two components: the correspondence of interannual variations and the agreement of long- term trends. We found that the longer the mean GSL for a tundra class, the poorer the correspondence between their interannual variations. Soil moisture limitation further decoupled the relationship by deteriorating the agreement of long-term trends. Consequently, the decoupling between NPP<sub>leaf</sub> and GSL would be more likely to occur under a warming climate if the tundra class had a mean GSL > 116 (or 123) days with a dry (or moist) soil moisture regime.
文摘The climate change in Alaska has caused earlier spring snowmelt and the growing season expanded. However, the effect of climate change on crop phenological stages, heading (BBCH 55) and maturity (BBCH 85), is unknown. In this study, the trends of growing-season length (GSL), phenological stages of crops and climatic parameters, and the correlations between climatic parameters and the phenological stages were analyzed using the climate data and crop data over the period of 1978 to 2016. The longer GSL was found in Fairbanks (64.83<span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span></span>N, 147.77<span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span></span>W) and in Delta Junction (64.05<span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span>N, 145.60<span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span>W) but not in Palmer (61.60<span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span>N, 149.11<span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">˚</span></span></span>W). Sowing dates did not change significantly in three locations. The decreasing trends of heading and maturity of crops were observed but varied with location. Heading of barley and oat significantly advanced 3 and 3.1 d decade<sup>-1</sup>, respectively from 1989 to 2016 in Fairbanks while no change of heading was observed in Delta Junction and Palmer. Maturity of barley, oat and wheat significantly advanced 2.6, 3.8 and 3.9 d decade<sup>-1</sup>, respectively from 1978 to 2016 in Fairbanks (<em>P</em> < 0.05);maturity of oat and wheat significantly advanced 4.4 and 3.4 d decade<sup>-1</sup> from 1978 to 2015, respectively in Delta Junction (<em>P</em> < 0.05). The increasing temperature trends and decreasing precipitation trends were found in Fairbanks and Delta Junction but varied with phenological stages of crops. Sowing was more important for heading than for maturity of crops. The effect of climate change on heading was less important than that on maturity. Earlier maturity of crops in Fairbanks may be attributed to increased temperatures, that in Delta Junction to both increased minimum temperature and decreased precipitation and that in Palmer to temperature and precipitation.
文摘草地广泛分布于干旱区和半干旱区,对季节性气候变化的响应十分敏感,但目前针对草地物候对季节性气候变化响应的研究仍较为薄弱。文章以内蒙古为例,基于不同草地类型的NDVI数据,辅以动态阈值、趋势分析和偏相关方法研究了2001—2020年草地物候时空动态、变化趋势及其随海拔梯度、气温和降水变化特征。结果表明内蒙古地区:(1)随纬度、海拔升高,草地生长季始期(start of growing season,SOS)逐渐推迟,生长季末期(end of growing season,EOS)缓慢推迟,生长季长度(length of growing season,LOS)呈不规律性变化趋势。(2)SOS集中在4月上旬到5月下旬,71.3%呈显著提前趋势,速率为0~2.0 d/a。EOS集中在9月下旬到10月中旬,69.98%呈推迟趋势。LOS持续在110~230 d,50.31%呈变长趋势。(3)在海拔500~2500 m的区域,随海拔上升,SOS推迟、EOS提前、LOS延长。(4)SOS与夏、秋、冬的气温为显著负相关关系,与春、秋、冬降水为显著负相关关系,与春季气温和夏季降水呈显著的正相关关系。EOS与春、夏、秋降水以不显著负相关性为主,与冬季降水以不显著正相关为主,与四季气温以负相关关系为主。LOS与春、夏、冬气温以负相关为主,秋季气温与LOS的正负相关参半。以上研究结果对内蒙古草地生长监测和应对气候异常提出保护策略、制定行之有效的防灾减灾措施、构建稳定的生态屏障具有指导意义。
