海北高寒草甸辐射能量的收支及植物生物量季节变化

The Seasonal Variations of Radiation Budget and of CommunityBiomass in the Haibei Alpine Meadows

高寒草甸植物生长,可用Logistic方程描述。生物量的瞬时增长率过程是一个先缓慢增大,后快速增大,逐渐达到最大值,然后快速降低,最后缓慢下降,逐渐逼近零;生物量达到最大时需累积78d左右;根据生物量的变化,将生长过程划分为返青期、茂盛期和枯黄期。枯黄期的反射率明显高于返青期和茂盛期,而返青期与茂盛期的反射率之间没有差异;返青期与茂盛期的日均辐射能量差异不显著(日均总辐射:Z=0.64,P=0.81=0.05;日均辐射净:Z=0.87,P=0.44=0.05;日均有效辐射:Z=0.92,P=0.37=0.05);返青期和茂盛期的日均辐射能量均显著地高于枯黄期(日均总辐射:H=45.36,df=2,P<0.01;日均辐射净:H=32.41,df=2,P<0.01;日均有效辐射:H=12.69,df=2,P<0.01)。有效辐射和反射辐射是影响地上生物量最重要的两个变量,但两个变量对地上生物量的作用效应各异,有效辐射是正效应,而反射辐射则是负效应。

The growth of plants in the alpine meadows,similar to the process of growth of all plants of other different areas,could be described by logistic equations the variable process of instantaneous growth rate of above-biomass starts to rise gradually,then rapidly until reaching the maximum point and then begins to decline rapidly and gradually down to zero point.It takes approximately 78 days for the instantaneous growth rate of above-biomass to hit the maximum point,generally around the 14th of July.Based on the variations of biomass and the instantaneous growth rate,the process of development could be divided into bourgeoning-turning green period(BGP),vigorous-growth period(VGP),and scorching period(SP).The albedo of SP is much more powerful than both the albedo of BGP and of VGP,though there is scant difference between the albedo of the last two.There is neither much differentce between the diurnal mean radiant energy of BGF and VGP(daily mean global radiation:Z=0.64,P=0.81=0.05;daily mean net global radiation:Z=0.87,P=0.44=0.05;daily mean effective radiation:Z=0.92,P=0.37=0.05),whereas,the diurnal mean radiant energy of SP is much less than that of BGP and VGP(daily global radiation:H=45.36,df=2,P<0.01;daily net global radiation:H=32.41,df=2,P<0.01;daily mean effective radiation:H=12.69,df=2,P<0.05).Effective radiation and reflective radiation are two highly important variables affecting the above ground biomass,though the former is positive,while the latter negative.