毕节吞天井边缘地带不同郁闭度环境对泥炭藓叶绿素荧光特性及蓄水量的影响

为了丰富对泥炭藓的生长环境认识,探究其对冲蚀型喀斯特天坑形成的可能影响,并寻找对其更适合的生长条件,采用梯度划分法,以采自毕节吞天井边缘地带不同郁闭度环境下生长的泥炭藓(Sphagnum palus?tre)为实验材料,分别测出其叶绿素荧光参数及蓄水量,探究不同郁闭度环境下泥炭藓的光合能力和持水能力。结果显示:①随着郁闭度的增大,泥炭藓的初始荧光(F^o)和最大荧光(F^m)均显著增大,分别由224.67上升至264,716上升至785.33。PSⅡ最大光化学效率(F^v/F^m)先降低后趋于平稳,光化学淬灭系数(qP)显著增大,由0.17上升至0.46。非光化学淬灭系数(NPQ)显著减小,由1.57下降至0.8。光合电子传递速率(ETR)显著增大,由5.72上升至9.68。②随着光照减弱,泥炭藓的吸水率和蓄水量显著升高,其中,自然吸水率由14.36上升至26.37,饱和吸水率由21.7上升至27.01;自然蓄水量由3032.97上升至12816.01,饱和蓄水量由4576.34上升至13175.97。③泥炭藓虽具有良好的耐光性,但高郁闭度环境,更有利于其叶绿素的积累,增强光合作用,提高生物量的积累,进而获得更强的蓄水能力。此外,不同植物种群之间的竞争会抑制泥炭藓的生长,分享土壤水分,而充足的水分是泥炭藓生存极为重要的条件。④泥炭藓良好的持水特性和吸水作用,在减缓地表径流上具有重要作用,在地质过程中起减慢的作用。而不同郁闭度环境下泥炭藓持水性的不同,也在一定程度上影响了水流的分配规律,从而对冲蚀型天坑的形成产生影响。

Effects of Different Canopy Density on the Chlorophyll Fluorescence and Water Storage Capacity of Sphagnum palustre in the Edge of the Tuntianjing Sinkhole in Bijie City

In order to enrich the understanding of the growth environment of Sphagnum,explore its possible impact on the formation of erosional karst tiankeng,and find more suitable growth conditions for it,we used gradient method,with S.palustre of different canopy density environments in the edge of the Tuntianjing sinkhole in Bijie City,to definite the chlorophyll fluorescence parameters and water storage capacity.Results showed:①The initial fluorescence(F^o)and maximum fluorescence(F^m)of S.palustre increased significantly with increasing canopy density(Fo:224.67-264;Fm:716-785.33).The maximum photochemical efficiency(F^v/F^m)of PSⅡdecreased firstly and then became constant;photochemical quenching coefficient(qP)and photosynthetic electron transport rate(ETR)increased significantly(qP:0.17-0.46;ETR:5.72-9.68)with increasing canopy density;non-photochemical quenching coefficien(t NPQ)decreased significantly from 1.57-0.8.②With canopy density increased,the rate of water absorption and water storage capacity of S.palustre were significantly increased,the natural water absorption and the saturated water absorption increased from 14.36-26.37 and from 21.7-27.01,respectively;the natural water storage increased from 3032.97-12816.01,and the saturated water storage increased from 4576.34-13175.97.③Although S.palustre has a good sunproof,they are more suitable for living in the low light conditions.As canopy density increased,it was beneficial to accumulate chlorophyll,promote photosynthesis and increase the accumulation of biomass,leading to a stronger water storage capacity.Competition can inhibit the growth of S.palustre,share soil moisture,and a certain moisture was very important for the growth of S.palustre.④The good water-holding properties and water absorption of S.palustre have an important role in slowing surface runoff that slowing down in geological processes.The difference in water holding capacity of S.palustre under different canopy densities can affect the distribution of water flow to a certain extent,thus affecting the formation of erosion-type sinkholes.