NWIPB OpenIR
高原鼠兔种群时空动态的元胞自动机模拟
其他题名The simulation of spatio-temporal dynamics of the plateau pika population using a cellular-automata model
刘汉武
学位类型博士
导师周立
2008-06-07
学位授予单位中国科学院西北高原生物研究所
学位授予地点西北高原生物研究所
关键词高原鼠兔 高寒草甸 元胞自动机 模拟 放牧 管理 全球变暖
摘要高原鼠兔是一种主要分布于青藏高原的小型哺乳动物,也是高寒草甸的关键物种。草甸的退化及食物链的断裂促其数量激增,不仅与家畜抢食牧草,而且掘土打洞破坏植被和草皮层及土壤结构,造成水土流失,又加剧草甸的退化。庞大的高原鼠兔种群对高寒草甸造成了极大的破坏,导致优良牧草剧减和土壤退化,牧草繁茂的草甸最终演变为寸草不生的“黑土滩”。根据最新普查结果,三江源区“黑土滩”退化草地面积达到7363.42万亩,占可利用草地面积(2.89亿亩)的25.48%,铲除鼠害已成为三江源生态保护和建设的紧迫任务。为了有效控制高原鼠兔的种群规模和抑制其扩散,必须深入研究高原鼠兔的生态特性和扩散规律,从而为治理鼠害提供科学依据。 2006年——2007年,笔者在青海省果洛藏族自治州进行了多项野外试验,观察高原鼠兔的生态特征、监测扩散数据,在此基础上,建立了模拟高原鼠兔扩散规律的元胞自动机模型,进而模拟不同环境条件下高原鼠兔种群时空动态,从中揭示其扩散规律。 元胞自动机是一时间、空间和状态都离散的动力系统。散布在规则格网中的每一元胞取有限的离散状态,遵循同样的作用规则作同步更新。大量元胞通过相互作用而构成动态系统的演化。不同于一般的动力学模型,元胞自动机不是由严格定义的物理方程或函数确定,而是用一系列模型构造的规则构成。 本文构建的元胞自动机模型,以高原鼠兔种群的密度阻滞增长机制为基础,同时考虑植被状态对其种群发展和迁移的制约,定量地描述高原鼠兔的扩散过程。元胞为正方形,边长17.4m,采用周期边界,八邻居,时间步长为一个月。简单说来其扩散机制如下:以C=每一元胞高原鼠兔有效洞口数量/环境容纳量,表示该元胞高原鼠兔生存的环境压力,以 表示鼠兔个体对原生存地的留恋指数。当环境压力C超过留恋指数 时,就产生了鼠兔迁移的动力。周围的元胞中如果存在生存压力较小者,且生存压力差大于留恋指数 时,于是鼠兔就向这些元胞扩散。模型在每一时间步长点上扫描所有的元胞,从而根据迁移规则确定下一时刻元胞的状态。 扩散力定义为所有元胞与所有邻居间大于 的 值差的和。有效洞口的扩散数量与扩散力的变化趋势基本上是一致的。扩散可以通过稀释作用减轻高原鼠兔对草甸的危害(数量上和/或程度上), 对高原鼠兔的扩散有着重要的影响, 越小高原鼠兔越容易扩散。 大的植被高度(生物量)能供养更多的高原鼠兔,但随着高度的增加,由于视觉受限高原鼠兔将不能有效地发现捕食者,因此高原鼠兔不选择植被过高的生境生活,所以元胞 内在时刻 的环境容纳量 (有效洞口数)先随植被增高而增大,然后减小,直至为零。由于元胞的大小为 ,这里 为 随放牧强度的加大植被变矮。当放牧强度较小时,植被高度受放牧制度的影响表现为:夏场(4--9月放牧)、连续放牧(全年放牧)、轮牧(偶数月放牧)、冬场(10--3月放牧)的植被依次降低。当放牧强度比较大时,连续放牧的草场植被最低。因而放牧对高原鼠兔种群的环境容纳量产生影响,进而促进或制约鼠兔的扩散。 在放牧的高寒草甸上鼠兔扩散的基本规律是:非退化高寒草甸上高原鼠兔迅速占据所有元胞,被危害的元胞数、被栖息元胞的平均有效洞口数在时间上有逐渐减小或保持不变的趋势。退化高寒草甸上高原鼠兔的扩散比较缓慢,被危害的元胞数、被栖息元胞的平均有效洞口数在时间上有逐渐增多的趋势。在退化高寒草甸上如果没有外界的干涉,高原鼠兔的危害会越来越严重,不能自行消失。 在高原鼠兔种群比较大的地方,人们常使用的控制办法就是利用药物杀死高原鼠兔。种群随灭杀比例的增大而减小,并且高寒草甸受高原鼠兔危害的时间也会随灭杀比例的增大而减少。在灭鼠实践中应力求空间上的均匀性。单次灭鼠是不能永久控制鼠害的,最好选择依情况脉冲式灭鼠(多次实施灭鼠)。 如果在高原鼠兔的非繁殖季节的固定时间灭鼠,若不考虑鼠兔对毒饵的采食,则在任何时间灭鼠对种群的长远动态不会产生影响。但若考虑毒饵的采食效果,则冬、春季灭鼠更好。如果在高原鼠兔的繁殖季节的固定时间灭鼠,从长远看,灭杀时间越晚越能压制种群规模。 不育控制一般有两种方式:一次性产生不育个体和不育个体不断产生。 采用第一种不育方式时,均匀式的空间方式效果要好;不育率越大,控制效果越好;如果采取固定时间脉冲方式,需要花费很长的时间才能消除危害,而采用依情况脉冲方式实施不育时,可以很快消除害鼠,但是实施不育的次数比较多;如果在固定时间实施不育,在繁殖季节实施要有更好一些的效果;如果在高原鼠兔的非繁殖季节实施不育,则不育实施的时间对种群以后的规模的影响没有差别。 采用第二种不育方式时,新的不育个体不断产生。用均匀式的空间方式时效果要好;不育率越高控制效果越好;如果在高原鼠兔的繁殖季节实施不育,实施的时间越早效果越好,而如果在非繁殖季节实施不育,则不育实施的时间对种群以后的规模的影响没有差别。 第一种不育方式是不能根除鼠害的,而第二种不育方式的实施,能够根除鼠害。 对直接灭杀和不育控制进行简单的比较可以得出:第二种不育控制具有良好的控制效果;第一种不育控制与直接灭杀相比,种群变化较为平稳,在刚实施控制后种群规模不能很快降到很低的水平,但从长远看效果要好一些;在采用依条件控制时,在后期三种控制(灭杀及两种不育控制)方式没有明显的区别。 灭鼠后对高寒草甸的恢复会直接影响灭鼠的效果。如果植被状况没有改变,高原鼠兔种群会快速恢复。如果植被有所恢复,残余种群恢复的速度会比较慢。当植被恢复到一定水平,高原鼠兔种群会长期得到抑制,不产生危害。 治理后的高寒草甸和退化的高寒草甸之间具有漫长的边界线,退化高寒草甸内的高原鼠兔就会逐渐向治理后的高寒草甸内入侵。当退化草甸上高原鼠兔密度比较大时,在相同的时间内入侵治理草地的距离也就比较远。恢复后的植被低矮时,入侵距离短,危害重;植被比较高时,入侵距离远,危害轻。 全球气候变暖使高寒植被生长期延长,气候的暖干化有可能使植物生产力降低。升温后如果高原鼠兔的繁殖期不延长,则在增温后与增温前,种群动态几乎没有区别。如果增温后高原鼠兔的繁殖期延长,在非退化高寒草甸上,增温前后种群动态差别不大;在退化高寒草甸上,高原鼠兔种群将迅速增大。
其他摘要The plateau pika (Ochotona curzoniae) is one small mammal, whose distribution largely coincides with the high alpine grassland of the Qinghai-Xizang plateau of China. The degradation of the alpine grassland increases its abundance, and at the same time, the increase of its abundance aggravates the degradation of the alpine grassland. Overabundance of Ochotona curzoniae damages the vegetation of the alpine grassland severely and this results in not only a decline in herbage yield but also a deterioration in the ecological environment. In order to effectively control the population size of Ochotona curzoniae, the physiological and ecological rules of Ochotona curzoniae should be sufficiently understood. A cellular-automata model is developed based on the ecological characteristics of Ochotona curzoniae and performed with date obtained from field experiments. The spatio–temporal dynamics of Ochotona curzoniae population is obtained through simulating experiments. The dispersal force is defined as the sum of the difference of C that is large than , between all cells and their all neighbourhood. The variation of amount of migratory live holes is approximately consistent with the variation of dispersal force. The dilution effect of dispersal can reduce damage (in amount and/or in degree) to the alpine grassland caused by overabundance of Ochotona curzoniae. The is an important parameter in dispersal. It is easy for Ochotona curzoniae to disperse when is small. The height of vegetation decreases with the increase of grazing intensity. When the grazing intensity is less, the effect of grazing systems on the height of vegetation is as below. The heights of vegetation under summer grazing, continuous grazing, rotational grazing and winter grazing are decreased in turn. When the grazing intensity is greater, the vegetation height of continuous grazing is the shortest. At certain time, the carrying capacity of Ochotona curzoniae has no significant relationship with grazing intensity and grazing system. The Ochotona curzoniae occupies all cells speedily through dispersal at the un-degraded alpine grassland. The amount of damaged cells and the average amount of live holes in occupied cells decrease or hold the line on spatial dimension. The dispersal of Ochotona curzoniae is restrained at the degraded alpine grassland. The amount of damaged cells and the average amount of live holes in occupied cells increase on spatial dimension. In areas where the densitiy of Ochotona curzoniae is high, rodenticides were always used to annihilate this small mammal. The population size of Ochotona curzoniae decreases and the damaged time of alpine grassland shortens with the increase of killing rate. In the lethal control practice, the uniformity in space is strongly commanded. Single lethal control can not root up the damage of Ochotona curzoniae. The best strategy to control Ochotona curzoniae is pulse lethal control based damage. If lethal control at fixed time in non-growing season of Ochotona curzoniae is implemented, the implementing time has no different effect on the long-range development of population. If lethal control at fixed time in growing season of Ochotona curzoniae is implemented, the later implementing time implies better effects on suppressing the Ochotona curzoniae population. In general, the contraception control falls into two modes: non-disseminating and self-disseminating. For the first mode, the uniformity in space and the greater contraception rate conduces better controlling effect. Pulse contraception control at fixed time can remove the damage of Ochotona curzonia after a long time and pulse contraception control based damage can remove the damage of Ochotona curzonia rapidly, but more implements of contraception control are needed. If the contraception control at fixed time is carryed out, the time in growing season of Ochotona curzonia is better. When the contraception control is carried out in non-growing season of Ochotona curzonia, the implementing time has no different effect on the population development. New sterile individuals are produced continually at the second mode of contraception control. The uniformity in space and the greater contraception rate will conduces better control effect. If the contraception control is conducted during growing season of Ochotona curzonia, the earlier implementing time implies better control effect. When the contraception control is carried out in non-growing season of Ochotona curzonia, the implementing time has no different effect on the population development. Our experiment proved that the first mode of contraception control could not uproot the damage of Ochotona curzoniae, but the second mode could. After comparing the lethal control and the contraception control, their characteristics could be stand out. Affirmatively, the second mode of contraception control is more effective in controlling the Ochotona curzoniae population. Comparing with the lethal control, the first mode of contraception control has better control effect in long views and after the non-disseminating contraception control, the Ochotona curzoniae population gradually, not abruptly, declines to small size. Under the pulse control based damage, the obvious distinction among these three control strategies dies away. The restoration degree of degraded alpine grassland after lethal control to Ochotona curzoniae would affect the control effect. If the vegetation condition did not change, the Ochotona curzoniae population would recover rapidly. If some restoration was made to the vegetation, the remanet Ochotona curzoniae population would recover at slow speed. When the vegetation was restored to certain degree, the Ochotona curzoniae population would be suppressed timelessly and the damage caused by Ochotona curzoniae would vanish. There are endless borderline between the degraded alpine grassland and the restored alpine grassland in our field sites. The Ochotona curzoniae inhabiting in degraded alpine grassland would invade the restored glassland. If the density of Ochotona curzoniae inhabiting in degraded grassland is high, the Ochotona curzoniae invade far. When the restored vegetation is low, the invading distance is short and the damage is heavy. Contrarily, when the restored vegetation is high, the invading distance is long and the damage is light. Global warming prolongs the growing season of alpine vegetation and reduces production of alpine grassland. If the growing season of Ochotona curzoniae did not prolong after global warming, the population dynamics of Ochotona curzoniae almost had no difference before and after warming. If the growing season of Ochotona curzoniae prolonged after global warming, the population dynamics of Ochotona curzoniae inhabiting in undegraded grassland almost had no difference before and after warming and the population of Ochotona curzoniae inhabiting in degraded grassland would swell up.
页数105
语种中文
文献类型学位论文
条目标识符http://210.75.249.4/handle/363003/3160
专题中国科学院西北高原生物研究所
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刘汉武. 高原鼠兔种群时空动态的元胞自动机模拟[D]. 西北高原生物研究所. 中国科学院西北高原生物研究所,2008.
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