中国温带地区植被物候期时空变化特征及对总初级生产力的影响

陆地表面物候(Land Surface Phenology,LSP)被定义为陆地表面植被的生命周期事件在区域或全球尺度上的各季节时间,对于中国温带地区的植被物候,已有研究大多仅针对某一地区的单一植被类型,对长时间、大尺度的陆表物候时空变化的研究较为少见,植被物候对总初级生产力(Gross Primary Productivity,GPP)的影响也有待明确。采用2001～2014年中等分辨率成像光谱仪MODIS的MCD12Q2数据以及MOD17A3 GPP数据,利用回归分析以及相关分析的方法对中国温带地区(>30°N)植被物候期时空变化特征进行分析,并研究物候变化对GPP的影响。结果表明:我国温带地区整体植被生长季开始日期(Start of the Season,SOS)、结束日期(End of the Season,EOS)和生长季长度(Length of the Season,LOS)的14 a平均值和标准差分别为第121±10 d、第270±12 d和153±12 d;SOS提前趋势(r=-0.36,p=0.21)、EOS滞后趋势(r=0.41,p=0.15)与LOS增长趋势(r=0.51,p=0.06)均不明显;但是年均LOS与GPP相关性显著(r=0.74,p=0.002 5),且呈正相关关系。2001～2014年LOS与GPP年均值的空间分布均呈现出由西北向东南增加的趋势;研究区SOS、EOS与LOS的年际变化呈现显著变化(p<0.05)的地区分别占研究区的13%、21%、13.2%。SOS、EOS、LOS与GPP显著相关(p<0.05)的地区分别占研究区的8.31%、9.33%、8.72%,三者与GPP的相关关系均以中度相关为主(p<0.05,0.5<|r|<0.8),二者高度相关(p<0.05,|r|≥0.8)的地区很少。研究区植被物候期变化显著影响(p<0.05)植被年均GPP的地区仅有4.29%。

Genetic Parameters for Yields and Reproductive Traits of Chinese Holstein Cows in Heilongjiang Province

[Objective] This study aimed to estimate the genetic parameters for milk yield, fat percentage, fat yield and age at first freshening of Chinese Holsteins first lactation cows in Heilongjiang under frigid-temperature and temperature zone. [Method] Records of yield and reproduction from 8 868 Chinese Holstein first lacta- tion cows from 21 herds were utilized to evaluate genetic parameters for Hei- Iongjiangs＇ Chinese Holsteins. Restricted maximum likelihood （REML） method was used with an animal model. [Result] The heritabilities were 0.16 to 0.34 for yields and fat percentage, 0.38 for reproduction （age at the first freshening）, which were similar to estimates for temperate areas from similar methods, except for constituent percentage. Also, the estimates of genetic correlation were high between milk yield and fat yield （0.97）, but were low between milk yield and fat percentage （-0.24）, age at the first freshening （-0.29） and generally antagonistic. [Conclusion] Thus, es- timates of genetic parameters in this frigid and frigid-temperate environment did not differ appreciably from those that occur in temperate dairy areas.

Holocene vegetation succession and responses to climate change in the northern sector of Northeast China

Sediment pollen samples from the Huola Basin in the northern sector of northeast China, and surface pollen samples from its environs, were analyzed to reconstruct accurately the historical response of vegetation to climate change since 9100 cal yr BP. Pollen analysis of the Huola Section indicates that vegetation experienced a transformation from early-mid Holocene warm-cold mixed vegetation to late Holocene cold-temperate vegetation. From 9100 to 6000 cal yr BP, the study area was warmer and moister than at present, developing Corylus, Carpinus, Pinus, Picea, Betula and Larix-dominated forests. Two cooling events at 6000–5000 and 3500–2500 cal yr BP led to a decrease in Corylus, Carpinus and other warmth-loving vegetation, whereas cold temperate forests composed of Larix and Betula expanded. After 2500 cal yr BP, Larix and Betula dominated cold-temperate vegetated landscapes. The Holocene warm period in NE China(9100–6000 cal yr BP) suggests that such warming could have resulted in a strengthening of the influence from East Asian Summer Monsoon on northernmost NE China and would have benefited the development of warm-temperate forest vegetation and an improved plant load, which also provides the similarity model for the possible global warming in the future.