【作者】 孙飞达；

【导师】 蒋文兰； 龙瑞军；

【作者基本信息】 甘肃农业大学 ， 草业科学， 2008， 博士

【摘要】 在三江源区(青海果洛)高寒草甸调查以高原鼠兔(Ochotona curzoniae)为主要鼠类的种群密度及其危害程度。以高原鼠兔有效鼠洞作为被调查的对象,最后确定4个不同鼠洞密度梯度的样地,对不同鼠洞密度下高寒草甸植物群落植物多样性、生产力、土壤理化性质等因子在生长季内(5～10月)的变化和特性进行了研究,取得了如下结论:1.不同鼠洞密度样地草地植物群落种类组成、数量特征及其多样性变化面积为25m×25m(1/16hm2)的四个不同鼠洞密度样地中,样地Ⅰ(AZP)主要植物有36种,小嵩草(0.151)、矮嵩草(0.1073)为群落优势种,平均优势度为0.028;样地Ⅱ(LP)主要植物有30种,小嵩草(0.1220)和早熟禾(0.1514)为群落优势种,平均优势度为0.0345;样地Ⅲ(MP)的主要植物有27种,铁棒棰(0.1134)等杂类草为群落优势种,平均优势度为0.037;样地Ⅳ(HP)主要植物有28种,鹅绒萎陵菜(0.1223)和多裂萎陵菜(0.1220)为群落优势种,平均优势度为0.036。物种多样性指数、均匀度指数随鼠洞密度的变化基本上与种的丰富度变化一致,但与优势度指数变化成相反趋势。鼠洞密度为54个时(样地Ⅲ,MP)各指标为最小值。鼠洞密度与植被盖度、物种数、多样性指数和均匀度指数之间的关系可以用二次函数y=ax2+bx+c来表示,其相关系数R2分别为0.96、0.9946、0.9815和0.9596。同样不同鼠洞密度样地植物群落盖度、物种丰富度、多样性和均匀度指数与其各自地上生物量之间的趋势也呈二次函数关系,其相关系数R2分别为0.9347,0.9858,0.8852,0.7。说明单峰式函数能较好地表达不同鼠洞密度样地植物群落盖度、物种丰富度、多样性和均匀度指数与有效鼠洞梯度和地上生物量的分布格局。2.不同鼠洞密度样地地上、地下、总生物量的变化及其相互关系地上生物量的峰值出现在8月底或9月份,4个不同鼠洞密度样地生物量最大值(g /m2)分别为444.6,135.1,150.7,179.1。各样地年生物量平均值排序为:样地Ⅰ(AZP) >样地Ⅲ(MP)>样地Ⅳ(HP)>样地Ⅱ(LP),说明生物量高低不能完全说明高原鼠兔的种群密度和危害程度。地下生物量最小值出现在8月份,4个不同鼠洞密度样地生物量最小值(g/m2)分别为5263.9,2830.7,1436.3,2280.2。各样地年生长量平均值排序为:样地Ⅰ(AZP) >样地Ⅱ(LP)>样地Ⅳ(HP)>样地Ⅲ(MP)。总生物量的趋势主要受地下生物量的支配,样地Ⅰ(AZP)地下生物量显著高于其它3个样地(P<0.01),各样地年总生物量平均值排序为:样地Ⅰ(AZP) >样地Ⅱ(LP)>样地Ⅳ(HP)>样地Ⅲ(MP)。4个不同鼠洞密度样地无论以生长季的平均值还是地上植物量达到极大值时其地下/地上植物量(R/T)比值均表明:样地Ⅱ(LP) R/T在各样地群落中比值最大,而样地Ⅲ(MP) R/T的比值最小,大小排序为样地Ⅱ(LP)>样地Ⅳ(HP)>样地Ⅰ(AZP) >样地Ⅲ(MP);地下生物量占总生物量的份额除样地Ⅲ(MP)外均超过95%,大小排序为:Ⅱ(LP)>样地Ⅳ(HP)>样地Ⅰ(AZP) >样地Ⅲ(MP)。生长季地上、地下和总生物量和不同鼠洞密度的变化曲线用二次函数关系式y=ax2+bx+c进行拟合,拟合效果良好,在鼠洞密度为54个(样地Ⅲ,MP)时各生物量达到最低点。地上和地下生物量的方差分析表明,地上生物量对鼠洞密度和月份的敏感程度要强于地下生物量的反应。3.不同鼠洞密度样地地上植物功能群组成及其失水率变化不同鼠洞密度样地生长季不同月份间各功能草群生物量和占有率均显示为差异显著(P<0.05),随着鼠洞密度的增加,以莎草、禾草为主的优良牧草减少,一些喜光和采食性较差的杂草出现,并比例增加。莎草类、禾草类、杂类草生物量在生长季5～10月期间呈“单峰”曲线变化,在8月或9月份达到峰值。而枯草却与前三类功能群草类的变化趋势恰恰相反,在8月或9月份其生物量为最小值,生长季初末期最大。4个不同鼠洞密度样地在牧草生长季的初期(5月份)、末期(10月份)失水率最低,6月份为最高,样地Ⅲ(MP) 7月份达到最大。4.不同鼠洞密度样地植物净初级生产力不同鼠洞密度样地地上净生产量、地下总净生产量、全群落净生产量均表现为差异极其显著(P<0.01)。地上部分的净生产量以样地Ⅲ(MP)最低,而样地Ⅰ(AZP)为最高达273.7 g /m2·a,比样地Ⅲ(MP)高出64.72%;地下部分与地上部分则相反。地下不同深度的净生产量在垂直高度上具有明显空间分布特征,0～10cm层最大,10～20cm和20～30cm层依次递减;5.不同鼠洞密度样地地下生物量分布特点地下部分根系的垂直分布十分明显,并随深度增加生物量急剧减少(P<0.01),呈“倒金字塔”分布。其地下植物量主要分布在0～10 cm的草层中, 0～20 cm层几乎占有了植物根系的全部,随鼠洞密度增加并有向地表层聚集的趋势。不同鼠洞密度样地生长季地下各层分布的平均植物量与土壤深度的关系用指数方程y=axb进行拟合(P<0.01),相关系数均达0.95以上;样地Ⅲ(MP)在7、8月份可以用幂函数y=aex进行拟合,相关系数达0.99以上。生长季不同月份地下生物量呈“V”字型曲线,但不同鼠洞密度样地间又存在显著差异(P<0.01),死根量的消长模式与活根大致相同,在8月份达到最低。不同样地在生长季不同月份根土比差异显著(P<0.05),且每个样地的不同层根土比差异及其显著(P<0.01)。土壤根土比随鼠洞密度的增大而减小至54个(Ⅲ,MP)时最小,到样地Ⅳ(HP)有所增加。不同鼠洞密度样地生长季不同月份根土比平均值分层变化,总的变化趋势是随着土壤深度的增加,根土比递减,并满足y=ax+b的线性关系(P<0.05)。样地各层总的变化趋势是样地Ⅰ(AZP) >样地Ⅳ(HP)>样地Ⅱ(LP)>样地Ⅲ(MP)。不同鼠洞密度样地各土层根土比随鼠洞密度变化的关系可以用y=ax2+bx+c(P<0.01)表示,R2=0.7271～0.9959。地下生物量和地上生物量的比值随鼠洞密度变化呈双峰曲线变化,在样地Ⅲ(MP)时为最小。总体是在近似零密度和中等密度时地下和地上生物量的比值达到波谷,在中等密度时最小,在低密度和高等密度时为波峰,特别是在低密度6月份时其比值达到最大。6.不同鼠洞密度对高寒草甸土壤层物理因子的影响不同鼠洞密度样地土壤地温随土层深度为“V”字型变化,在15 cm处地温达到最低,5 cm处和25 cm处地温相当。不同鼠洞密度和土壤含水量、容重、pH值没有直接的函数关系。但是含水量、容重、pH值均与其分层满足线性相关,符合y=±ax+b形式。含水量随深度增加而降低,表层(0～10cm)最高,样地Ⅰ(AZP)含水量为最高,样地Ⅲ(MP)为最低;容重随土层深度增加而增加,由于地下根主要积聚在第一层,8月份为生长旺盛期;土壤显弱碱性,pH值随土层深度增加而增加,而样地Ⅲ(MP)高于其他3个样地,这与该样地为重度退化阶段有关。7.不同鼠洞密度对土壤养分含量的影响4个不同鼠洞密度样地在生长季土壤养分含量随季节变化表现出多样性。不同样地的土壤有机质、全氮、全磷、碱解氮和速效钾含量均随土层增加而减少,即0～10cm>10～20cm>20～30cm。各养分因子含量和鼠洞密度的关系主要在0～10cm差异显著(P<0.05),与第2、3层差异不显著(P>0.05)。随季节变化最大值基本出现在8月或9月份。不同鼠洞密度的样地土壤有机质含量大小排序是:样地Ⅰ(AZP) >样地Ⅱ(LP)>样地Ⅳ(HP)>样地Ⅲ(MP)。不同样地土壤全氮含量排序为样地Ⅰ(AZP) >样地Ⅱ(LP)>样地Ⅳ(HP)>样地Ⅲ(MP)。随生长季节的变化趋势为“V”字型,在鼠洞密度是3个(Ⅰ,AZP)时含量最高,后随鼠洞密度增大含量急剧下降至最低点(Ⅱ,LP),后缓慢上升。生长季全磷含量除8月外其它月份含量变化不大,基本保持恒定。碱解氮含量0～10cm 8月份达到最大后下降,10～20cm、20～30cm两层土壤却在8月份为最小值。样地Ⅰ(AZP)、Ⅱ(LP)和样地Ⅲ(MP)速效钾含量季节动态变化一致,均在8月份达到最大后下降,样地Ⅳ(HP)除表层在6月份后下降并在8月份为最小值后缓慢上升。以生长季初期的6月和旺盛期的8月为例,鼠洞密度和土壤各层营养因子养分含量之间的关系建立关系式y=ax2+bx+c。式中y代表土壤各营养因子的含量,x为不同鼠洞密度,a、b、c为常数,反映草地的土壤营养状况。随着鼠洞密度的增加,土壤各营养因子养分含量反而降低,在由54个(MP)到85个(HP)的过程突然增加。从所选取的4个递增鼠洞梯度来看,54个(MP)有效鼠洞的样地各层各养分含量均为最小值。8.适宜鼠洞密度及种群的确立结合不同鼠洞密度样地植被及土壤状况可以判断,样地Ⅰ(AZP)、Ⅱ(LP)、Ⅲ(MP)和Ⅳ(HP)退化演替程度分别为未退化、轻度退化、重度退化和中度退化阶段,这也验证了中度退化草地鼠类种群最大的结论。结合前人研究成果可以得出,样地Ⅱ(LP)为鼠洞密度较适宜范围,即鼠洞密度为512个/hm2,结合洞口系数可以得出适宜的高原鼠兔种群密度范围为:70～110只/hm2。鼠类活动及其危害程度是草地退化和演替的衍生物和信号,只是加剧了草地退化的进程。实际上植被的局部性破坏及斑块状分布才是导致高原鼠兔迁入的重要原因。更多还原

【Abstract】 The relationship between rodents activities, taking the plateau pikas as example,and alpine meadow degraded degree has aroused considerable interest and controversy in recent ecological literstrue.The burrowing rodents in use were investigated in Guoluo Prefecture,Qinghai Province, the important part in source region of Yangtze and Yellow river. Then four different densities sampling sites were established in alpine meadow for current study. This research mainly includes two parts: (1)the effects of different burrowing rodents densities on aboveground vegetation factors mainly included plant diversity and primary productivity from May to October; (2) the effects of different burrowing rodents densities on belowground environment factors mainly included belowground biomass distribution and soil resource characteristics in plant growing season from May to October. Main results and conclusions from the research were summarized as follows:1.Composition of plant population,characteristics of species and variation of plant diversity at different burrowing rodents densities plots:PlotⅠ( AZP) with 3 burrows per 1/16hm2 has 36 kinds of species,Kobresia pygmaea and Kobresia humili are dominent species of theirs population.As same as PlotⅠ, PlotⅡ( LP) with 32 burrows has 30 kinds and Kobresia pygmaea and Poa annua are dominent species.PlotⅢ( MP) with 54 burrows has 27 kinds and Aconitum pendulum is dominent species. PlotⅣ( HP) with 85 burrows has 28 kinds,Potentilla anserina and Potentilla multifida are dominent species.Their average significant value are 0.028,0.0345,0.037 and 0.036 respectively.Species diversity and eveness indexes change with the same as the richness index variation tendency of plant communities, however, the dominance index changes the opposite tendency. When the burrows reaches 54 per 1/16hm2, every indexes decline to the smallest. The relationship between plant coverage,richness index,diversity index,eveness index and burrowing rodents density can be described with equation of y=ax2+bx+c,and the correlation coefficient are 0.96、0.9946、0.9815 and 0.9596 respectively. Similarly these plots aboveground biomass display the same relationship of quadratic equation with such diversity indexes, the correlation coefficient are 0.9347,0.9858,0.8852,0.7 respectively. From the above conclusions it can be considered that the unimodal curve function could elucidate the distribution pattern of such diversity indexes, burrowing rodents densities and theirs aboveground biomass better. 2.Variation and relationship between alpine meadow aboveground biomass, belowground biomass,total biomass and different burrowing rodents densities each other:In plant growing season from May to October the aboveground biomass peak value appears in August or September, and the maximum biomass(g /m2)of four plots are 444.6,135.1,150.7,179.1 respectively. The order of annual average biomass is plotⅠ( AZP), plotⅢ(MP), plotⅣ( HP) and plotⅡ(LP). The minimum value of belowground biomass appears in August, and the minimum biomass(g/m2)of four plots are 5263.9,2830.7,1436.3,2280.2 respectively. The order of annual average belowground biomass is plotⅠ( AZP),plotⅡ( LP), plotⅣ( HP) and plotⅢ(MP). Total biomass variation trend is mainly dominated by belowground biomass for its large possession. The total biomass of plotⅠ(AZP)is significantly higher than others(P<0.01)and the order of annual average is plotⅠ(AZP), plotⅡ(LP), plotⅣ(HP) and plotⅢ(MP),which shows that only aboveground biomass can not reveal the plateau pikas population and its destroied extent.The ratio of belowground and aboveground biomass(R/T), although two both are the annual average or the belowground is the maximum value,indicates that the R/T of plotⅡ( LP)is most and plotⅢ(MP) is least. The R/T ratio order of four plots is plotⅡ( LP), plotⅣ( HP), plotⅠ(AZP) and plotⅢ(MP). The belowground biomass of total biomass proportion is bigger than 95% expcect plotⅢ,and the order is plotⅡ( LP),plotⅣ( HP), plotⅠ( AZP) and plotⅢ(MP).The relationship between aboveground, belowground, total biomass and burrows densities can be simulated by y=ax2+bx+c equation, and the correlation coefficient is from 0.8353 to1.0000. When the burrows density is 54(Ⅲ,MP) the biomass is least. The aboveground and belowground biomass variance analysis indicate that aboveground biomass is more sensitive to both different burrowing rodents densities and plant growing months than to belowground biomass.3.Composition of aboveground plant functional groups(PFGs) and variation of theirs water lose rate at different burrowing rodents densities plots:Every plots plant function group biomass and theirs percentage in growing season indicate the significant difference(P<0.05).With the burrows increasing,the sedges and grasses are decreasing gradually. Simultaneously some likly light and bad palatability forbs appear and the proportion increases.Sedges,grasses and forbs biomass change with unimodal curve in growing season and get the peak value in August or September. But residues biomass has the other way round,which decreases to the minimum in August or September and the peak value appears in May and October.Forage grasses water lose rate in May and October are least and in June is most in growing season. Of others plots, the largest water lose rate appear in July. 4.Net primary productivity at different burrowing rodents densities plots: The difference of net productivity of aboveground, all net productivity of belowground and net productivity of whole community is extremely significant(P<0.01). Net productivity of aboveground in plotⅢ(MP) is least of all,while plotⅠ( AZP) is 273.7 g /m2·a,which is higher 64.72% than plotⅢ. Net productivity of belowground is contrary to aboveground. Net productivity of belowground of every soil layers has obvious spatial distribution characteristics in vertical height. Soil layers of 0～10cm,10～20cm and 20～30cm depth are decreased in turn.5.Distribution characteristics of belowground biomass at different burrowing rodents densities plots:The belowground biomass distributes vertical pattern obviously and with soil depth increasing, the biomass reduces suddenly(P<0.01), which is described as contrary Pyramid pattern. The belowground biomass is distributed at a scale of 0～10 cm, and plant roots are trended together in soil surface layer with burrows increasing, especially in August.The relationship between the annual average belowground biomass in erery layers and soil depths is simulated by exponential equation y=axb(P<0.01) , the correlation coefficient is over 0.95, except that plotⅢ(MP) can be described with power function y=aex in July and August, and the correlation coefficient is over 0.99.Belowground biomass variation trend can be described with“V”model , firstly declines sharply and then rises slowly. Although it has significant difference with burrowing rodents densities. Dead roots change approximately same as living roots variation trend and the minimum value appears in August. The ratio of roots and soil weight in growing season with every soil layers difference is significant(P<0.05).With the burrows increasing,the ratio of roots and soil reduces gradully to plotⅢ( MP), 54 burrows per 1/16hm2, then increases to plotⅣ(HP),85 burrows per 1/16hm2.Generally speaking, with the soil depth deepening,the annual average of ratio of roots and soil weight is decreasing, which can be described with linear equation y=ax+b(P<0.05). As a whole the trend in every soil layers of four plots is plotⅠ( AZP)>plotⅣ( HP)>plotⅡ( LP)>plotⅢ(MP).Also the relationship between ratio of every layers roots and soil and burrowing rodents densities is simulated by quadratic equation y=ax2+bx+c(P<0.01), and the correlation coefficient is from 0.7271 to 0.9959.The ratio of belowground and aboveground biomass varies with burrowing rodents increasing by bimodal curve and reduces to the minimum value of 54 burrows per 1/16hm2(MP).General the burrowing rodents in use lies in the approximate zero density(AZP) or medium density(MP) the ratio reduces to lower and lowest. At the low density(LP)or high density (HP)the ratio ascends to higher and highest in June. 6.Effects of different burrowing rodents densities on soil layers physical factors:Soil temperature changes with soil layer deepening of“V”modle at different burrowing rodents densities plots. The temperarture at 15cm depth is lowest and at 5cm depth it is equal to 25cm depth. Soil moisture,bulk density and pH value have no function relationship directly with burrowing rodents increasing, but has linear correlation with soil layers by y=±ax+b equation.The top soil layer moisture is highest and it decreases with soil layer deepening.The soil moisture of plotⅠ(AZP) is highest and plotⅢ(MP) is lowest of four different plots. Also soil bulk density increases with soil layer deepening for the roots mainly assembles in the first layer and plant peak appears in August. Usually soil reveals reak alkalinity and pH value increases with soil layer deepening, too. PlotⅢ(MP) pH value is more than others, whih is decided by the specific characteristics of heavy degraded meadow.7.Effects of different burrowing rodents densities on soil nutrient variation: Soil nutrient content displays the multiplicity with the seasonal variation at different burrowing rodents densities plots. General the content of SOM,TN,TP,AN and AK decreases with soil layer deepening, 0～10cm>10～20cm>20～30cm.The relationship between every nutrient factors content and burrowing rodents densities is significant difference in 0～10cm layer(P<0.05),while it has no significant difference in the second and the third layers. In plant growing season the most content appears in August or September. The order of SOM content is plotⅠ( AZP),plotⅡ(LP), plotⅣ( HP) and plotⅢ( MP), TN content sequence is plotⅠ( AZP),plotⅡ(LP),plotⅣ(HP) and plotⅢ(MP) of four plots. These two factors content change with“V’modle and theirs minimum values appear at 32 burrows per 1/16hm2(LP). TP content maintains invariable in growing season except for in August and AN content of 0～10cm layer is highest than others layers,but 10～20cm and 20～30cm layers are lowest in August. The seasonal dynamic of AK content of plotⅠ(AZP),Ⅱ( LP) andⅢ( MP) is consistent, reaching maximum in August then decreasing .While plotⅣ(HP) is an exception that the minimum value appears in August. Taking the growth initial and growth boom period as the example, separately in June and in August. The relationship between soil nutrient factors content and soil layers, burrowing rodents densities separately both can be described with the equation of y=ax2+bx+c.With the burrowing rodents increasing soil factors nutrient content is decreasing reversly, but the burrows from 54(MP) to 85(HP) the content climbs up suddenly.The lowest content of every nutrient factors is in plotⅢ( LP) of four plots.8. Establishment of suitable burrowing rodents and population density scope: Fully combinated the vegetation and environment of four different burrowing rodents densities plots, it can be deduced that four plots are non-degraded(AZP), lightly degraded(LP), heavily degraded (MP) and moderately degraded(HP) grassland respectively from vegetation succession. Simultaneously it also can be confirmed that the existing conclusion of moderately degraded grassland having the most rodents popolation. From all of above analysis and deduction that 512 burrows in use per 1hm2 is a suitable value and the plateau pikas population scope is from 70 to 110 per 1hm2 from the investigated burrows coefficient. And the conclusion, rodents activities and theirs harm extent are derivative and signal but aggravates the advancement to alpine meadow degradation and succession phase, therefore, only vegetation partial destruction and spot massive distribution lead to the massive plateau pikas moving into, is summarized of this study.更多还原