我国东部温带植物群落的季相及其时空变化特征

 植物群落季相阶段的划分，对于诊断地方、区域和全球尺度上生态系统对气候变化的快速响应和进行遥感植被生长季节的地面检验，具有重要 的科学意义。该文利用物候累积频率拟合法对我国东部温带地区7个站点1982～1996年的植物群落季相阶段进行划分，并分析了植物群落季相的 空间差异和年际变化及其与气候因子的关系。结果表明：1）各站点多年平均变绿期和旺盛光合期初日随纬度的升高而推迟，凋落期和休眠期初 日随纬度的升高而提前；多年平均变绿期、旺盛光合期和凋落期长度随纬度的变化不甚明显，而休眠期则随纬度的升高明显延长；2）在研究期 间内，站点平均变绿期初日以0.6 d&;#8226;a^－1的平均速率显著提前，且长度以0.7 d&;#8226;a^－1的平均速率显著延长；旺盛光合期初日呈不显著推迟，长 度呈不显著缩短；凋落期初日呈微弱提前，长度呈微弱延长；休眠期初日呈微弱提前，但长度却以0.9 d&;#8226;a^－1的平均速率显著缩短；3）站点平 均变绿期初日与当月平均气温的负相关显著，平均气温每升高1 ℃，初日提前约4.3 d；站点平均旺盛光合期初日与初日前第二个月到初日当月 平均气温的负相关显著，平均气温每升高1 ℃，初日提前约4.4 d；站点平均凋落期和休眠期初日与气温的相关均不显著。

SEASONAL ASPECT STAGES OF PLANT COMMUNITIES AND ITS SPATIAL, TEMPORAL VARIATION IN TEMPERATE EASTERN CHINA

Aims Our objectives were to determine the seasonal aspect stages of plant communities at seven sites in the temperate area of eastern China and analyze spatial-temporal variation of the onset dates of seasonal aspect stages and its relation to climatic factors. Methods We developed a simulating method of phenological cumulative frequency to determine the seasonal aspect stages of plant communities. Basic ideas of the method were to establish a mixed data set composed of the occurrence dates of all phenophases of observed deciduous trees and shrubs for each site and each year , and then calculate the frequency and cumulative frequency of the occurrence dates of phenophases in every five-day period throughout each year and for each site. We used a logistic curve to simulate the phenological cumulative frequency and computed the corresponding dates of maximum changing rate of the curvature as the onset dates of seasonal aspect stages. Important findings The annual mean dates of greenup and active photosynthesis onsets were delayed with increased latitude, whereas the annual mean dates of senescence and dormancy onsets advanced with increased latitude. Other than the onset dates, the annual mean lengths of greenup, active photosynthesis and senescence periods did not change obviously with latitude but the annual mean length of dormancy period was apparently prolonged with increased latitude. From 1982 to 1996, the regional mean onset date and duration of greenup period significantly advanced at a rate of 0.6 d&;#8226;a^－1 and lengthened at a rate of 0.7 d&;#8226;a^－1; the mean onset date and duration of active photosunthesis period were insignificantly delayed and shortened; the mean onset date and duration of senescence period slightly advanced and lengthened; and the mean onset date and duration of dormancy period slightly advanced but significantly shortened at a rate of 0.9 d&;#8226;a^－1. The onset date of seasonal aspect stages generally correlates better with temperature than with precipitation. The regional mean greenup onset date shows a significantly negative correlation with mean temperature in the current month in a changing rate of 4 .3 d&;#8226;℃^-1, whereas the regional mean active photosynthesis onset date presents a significantly negative correlation with mean temperature during the former second month to the current month in a changing rate of 4.4 d&;#8226;℃^-1. However, the regional mean senescence and dormancy onset dates do not correlate significantly with mean temperatures.