秦岭南北坡森林鼠类对板栗和锐齿栎种子扩散的影响

森林鼠类的种子贮藏行为对植物的扩散及更新会产生积极的影响。2012和2013年秋季,分别在秦岭北坡的周至国家级自然保护区和南坡的佛坪国家级自然保护区内,调查了森林鼠类对板栗(Castanea mollissima)和锐齿栎(Quercus aliena)种子的取食和扩散差异。结果显示:1)秦岭南北坡的环境因素,特别是植被因素,对鼠类扩散板栗和锐齿栎种子具有重要的影响。南坡较为丰富的壳斗科植被种类,导致2种种子在南坡存留时间均长于北坡,而北坡的扩散取食和丢失率均高于南坡。2)种子特征影响鼠类的取食或贮藏偏好。由于较高的蛋白、脂肪等营养含量,鼠类更喜好取食或搬运贮藏板栗种子。然而,低营养但高丹宁含量的锐齿栎种子仍然被鼠类大量贮藏。3)2种种子在南北坡的扩散历程在两个年份间有很大差异,在食物相对匮乏的年份(2012年),种子被扩散的速度更快且丢失的比率更高。这种差异反映了种子大小年现象对森林鼠类取食和贮藏策略的影响。4)无论在秦岭南坡还是北坡,营养价值含量(如蛋白和脂肪)较高的板栗种子的取食和贮藏距离都明显大于营养价值含量较低的锐齿栎种子,这与最优贮藏空间分布模型的预测一致。     

昆虫蛀蚀对鼠类介导下的锐齿槲栎种子扩散的影响

森林鼠类的种子贮藏行为对植物的扩散和自然更新有着非常重要的影响。然而,鼠类是否具有鉴别虫蛀种子的能力还存在一定的争议。此外,鼠类的鉴别能力是否受到食物丰富度变化的影响也未见相关报道。采用标签标记法,2011年秋季(9—11月,食物丰富季节)和2012年春季(4—6月,食物匮乏季节)分别在秦岭南坡的佛坪国家级自然保护区内,调查了森林鼠类对完好和虫蛀锐齿槲栎(Quercus aliena)种子的选择差异。结果显示:1)在秋季,尽管2种类型种子的存留动态没有显著差异,但是在后期虫蛀种子的存留时间相对更长;而在春季2种类型种子的存留动态则极为显著,几乎所有的完好种子(99%)在释放后的第3天就被鼠类全部扩散,虫蛀种子的存留时间则相对较长。2)在秋季,鼠类更喜好扩散后取食完好种子;而在春季,鼠类则喜好在原地取食绝大部分的种子,并且优先取食完好种子。3)在秋季,鼠类贮藏了更多的完好种子;而在春季,尽管完好种子在释放后第1天便达到贮藏高峰,然而由于后期的大量被捕食,2种类型种子在贮藏动态上没有显示出显著差异。研究结果表明秦岭地区森林鼠类可以准确区分完好与虫蛀种子,但是食物丰富度会影响鼠类对种子的选择策略。在食物丰富的秋季,鼠类更多地选择贮藏完好种子;而在食物相对匮乏的春季,鼠类更倾向于同时取食2种类型种子。森林鼠类通过对2种类型种子的鉴别和选择,影响不同种子的命运,从而可能对种子的扩散和自然更新产生重要影响。     

济源太行山区鼠类对三种林木种子的扩散和贮藏

对取食种子的动物而言,种子的选择、扩散以及随后的处理是一个复杂的过程。为了解济源太行山区鼠类对不同种林木种子的选择和扩散策略的差异,于2011 年9 月10 日至11 月8 日,选取山杏、桃和栓皮栎3 种林木种子,将种子标记后,释放于次生林中,以5 d 间隔,调查并记录种子命运。结果表明: (1)大林姬鼠和岩松鼠是该地区主要的种子取食者和扩散者; (2)3 种种子的扩散速率明显不同,栓皮栎种子扩散速率最快(中位存留时间8. 6 d),其次为山杏种子(中位存留时间20. 9 d),桃种子扩散速率最慢(中位存留时间37. 5 d); (3)鼠类倾向于取食栓皮栎种子(55.0%) , 埋藏山杏种子(62. 0% ),但忽略桃种子(原地存留率99. 0% );(4)88. 6%的山杏和78. 8% 的栓皮栎种子被贮藏在灌丛下方、树干基部周围和石块旁边等生境中,而仅有4 3% 的山杏和9.1% 的栓皮栎种子被贮藏于裸地中;(5)鼠类将山杏种子搬运到更远(3. 4 ± 2. 1 m,mean± SE,n =63)处贮藏;而栓皮栎种子的搬运距离则相对较近(2. 5 ± 2. 4 m,n = 57)。结果显示:鼠类对不同种植物种子具有明显的取食、贮藏偏好和不同的贮藏策略。     

食物丰富度对鼠类鉴别和扩散虫蛀短柄枹栎种子的影响

时空因素和种子特征对森林鼠类扩散植物种子有着非常重要的影响。为了解食物丰富度对鼠类鉴别和扩散虫蛀种子的影响,于2012年春季(4—5月,食物匮乏季节)和2012年秋季(9—11月,食物丰盛季节),采用塑料片标记法,在秦岭南坡的佛坪国家级自然保护区内调查了森林鼠类对完好的和虫蛀的短柄枹栎Quercus glandulifera种子的扩散差异。结果显示:1)森林鼠类可以较为准确地区分完好种子和虫蛀种子。完好种子的扩散速度较快,而虫蛀种子在原地的存留时间相对较长。2)食物丰富度会对鼠类鉴别和扩散虫蛀种子产生一定的影响,但是这种影响并不显著,鼠类在春、秋季均倾向于优先取食或贮藏完好种子。3)完好种子在秋季被鼠类贮藏的比例(20%)显著高于春季(12.5%),说明种子在食物丰盛季节能够获得更大的利益。     

秦岭森林鼠类对华山松种子捕食及其扩散的影响

森林鼠类的种子贮藏行为对植物的扩散和自然更新有着非常重要的影响。通过塑料片标记法,2008和2009年的9月—11月分别在秦岭南坡的佛坪国家级自然保护区内调查了森林鼠类对华山松(Pinus armandii)种子的捕食和扩散,结果显示:森林鼠类对华山松种子有着非常大的捕食压力。在2008年,几乎所有的种子(96.4%)在第3天后就被全部取食,而在2009年,也有将近一半的种子(49.6%)在第3天后被取食。但与此同时,鼠类对华山松种子的扩散也起着非常重要的作用。尤其在2009年,第3天时鼠类最高分散贮藏了17.75%的种子,而且直到第19天后仍然有12.25%被贮藏的种子存活下来。华山松种子在两个年份间的扩散历程有很大差异。在2008年,几乎所有的种子都被鼠类取食,贮藏量非常小;而在2009年,种子被贮藏的比例显著的增加。这个结果可能与种子大小年现象有着十分紧密的联系。2008年是华山松种子的小年,产量非常低。鼠类为了满足其日常的能量需求,只能大量的取食有限的种子,而减少其贮藏量。而2009年是华山松种子的大年,产量非常高。鼠类在满足其日常能量需求的同时,还有大量剩余的种子供其贮藏。     

种子产量对鼠类扩散栓皮栎坚果的影响

为了解林木种子产量对鼠类种子扩散行为的影响,于2008 年和2009 年,在国有济源市愚公林场调查了栓皮栎的种子雨;在每年的种子雨结束后,选择次生林生境,研究了鼠类对人工释放栓皮栎坚果的扩散,旨在探讨种子产量与种子扩散间的关系。结果表明:1)取食栓皮栎坚果的鼠类主要有大林姬鼠、社鼠和岩松鼠,2008 年的鼠类捕获率(2% )低于2009 年(10%),其差异并未达到显著性水平;2)栓皮栎的种子雨构成和产量存在年际差异,2008 年以完好种子为主且产量高于2009 年,而2009 年以败育种子为主;3)2008 年人工释放栓皮栎坚果的中位存留时间显著高于2009 年;4)2008 年鼠类对栓皮栎坚果的平均扩散距离显著低于2009 年,且两年的搬运距离几乎都集中在9 m 以内;5)2008 年鼠类对栓皮栎坚果的埋藏比例显著高于2009 年。结果提示,在种子高产年份,可能有较多的种子逃脱动物的取食,从而增加种子萌发和幼苗建成的机会,最终促进植物的更新。     

鼠类对山杏和辽东栎种子的贮藏

在北京市东灵山地区,选择灌丛生境,人工释放山杏和辽东栎种子,对两种种子在释放处被鼠类就地取食、存留动态、种子被搬运和贮藏的距离、位置、状态、微生境等进行了分析比较。采用活捕饲喂和咬痕比较的方法,对野外取食山杏和辽东栎种子的鼠类进行了鉴定。结果表明：1)取食山杏和辽东栎种子的鼠类主要是大林姬鼠和岩松鼠;2)山杏种子被鼠类搬运的平均距离大于辽东栎种子,两种种子大多数被搬运至21m之内,在9m之内最为集中;3)山杏种子的中位存留时间较辽东栎种子长;4)在释放处,鼠类对辽东栎种子的就地取食强度(54．83％)大于对山杏种子的取食(0．17％);5)在搬运之后,大部分山杏种子被埋藏起来,仅有3粒被取食;而辽东栎种子大部分被取食;6)鼠类趋向于把种子搬运到灌丛下方或灌丛边缘进行贮藏或取食。山杏种子在贮藏点的数量为1—3粒,而辽东栎种子在贮藏点的数量均为1粒。     

种子大小对小泡巨鼠贮藏行为的影响

以小泡巨鼠为研究对象,在围栏条件下,测定小泡巨鼠对大小两种栓皮栎种子的贮藏行为差异,以检验最优贮藏空间模型的两个预测:(1)大种子(高价值食物)的贮藏率大于小种子(低价值食物);(2)大种子的贮藏距离远于小种子.结果表明:大种子的搬运比例(39%)多于小种子(21.5%),多数的小种子(53%)被取食,大种子的贮藏比率(16%)远大于小种子(7%),上述结果支持模型的预测(1).但是,不同大小种子在贮藏距离上没有显著差异,因而预测(2)没有被支持.实验结果表明种子价值对鼠类的取食和贮藏行为有十分重要的影响,但围栏空间可能影响对模型预测(2)的检验.     

种壳厚度对鼠类种子扩散行为及种子命运的影响

种子扩散是植物更新和扩大分布区的一种重要途径。鼠类采取不同的种子扩散和贮藏策略,以应对食物短缺,同时也促进了植物种子扩散。为应对鼠类对植物种子的过度取食,种子进化出了一系列物理、化学等防御特征。其中种壳厚度作为一种物理防御策略,是影响鼠类贮藏行为和种子命运的关键因素。本研究拟通过去除天然栓皮栎（Quercus variabilis）种子的外壳,再在种仁外包被1、2、4、6不同层数的聚乙烯薄膜,模拟种壳厚度,准确控制种壳厚度。2020年10月—2021年1月,在四川都江堰森林生境中释放人工种壳包被的种子,研究人工种壳厚度对鼠类介导的种子扩散和命运的影响。结果表明：（1）鼠类优先扩散种壳较薄（1层薄膜包被）的人工种子;随着种壳厚度的增加,扩散速率逐渐降低,种壳最厚（6层薄膜包被）的种子扩散最慢（P < 0.001）;（2）鼠类喜好分散贮藏1层、2层薄膜包被的种子;当种壳厚度增加至包被4层、6层薄膜时,分散贮藏比例显著降低（P < 0.05）;（3）鼠类偏好集中贮藏4层薄膜包被的种子（P < 0.05）;（4）不同种壳厚度的种子扩散距离无显著差异（P > 0.05）;（5）种壳较薄（1层薄膜包被）的种子分散贮藏率在3 m范围内比例较高。采用聚乙烯薄膜包被是模拟种子外壳的可行方法,并可用于评估种壳厚度对鼠类种子贮藏行为和种子命运的影响等相关研究。     

外果皮厚度和种子大小对五种栎属橡子扩散的影响

动物对种子的扩散和贮藏是一个复杂的生态学过程,常常受到种子特征的影响。有关种子特征如何影响动物对种子扩散,许多研究结果并非完全一致。我们于2009 年9 月在黑龙江东方红林场野外和围栏内释放五种栎属橡子(Quercus mongolica,Q.serrata var. brevipetiolata,Q. aliena,Q.variabilis 和Q. liaotungensis),研究种子特征对鼠类(Apodemus peninsulae, Clethrionomys rufocanus 和Tamias sibiricus)扩散和埋藏橡子的影响。野外释放结果表明:橡子大小和外果皮厚度显著影响鼠类对橡子的扩散和埋藏。鼠类偏向扩散和埋藏种皮厚的大橡子,种皮薄的小橡子则多被原地取食。种皮厚的大橡子扩散距离显著高于种皮薄的小橡子。然而,只有外果皮的厚度显著影响围栏内花鼠对橡子的扩散和埋藏,橡子大小并非主要的影响因素。种子特征影响种子扩散的效应可能在种群和群落水平上存在差异。     

啮齿动物对不同林木种子的搬运和取食微生境选择机制

不同植物种子依靠不同的方式实现扩散,啮齿动物对林木种子搬运后在取食点微生境和贮藏方式的选择存在偏好,研究其贮藏行为与微生境的关系是探究幼苗建成的关键。在秦岭中段火地塘林区,采用标签标记法,以锐齿槲栎、华山松和油松种子为材料,探究了小型啮齿动物对松栎混交林建群种种子扩散过程的影响。结果表明:1)油松种子原地取食率显著高于锐齿槲栎和华山松种子,且啮齿动物更倾向于搬运后取食(60%)和埋藏(4.33%)华山松种子,搬运后取食距离也为华山松最大(2.49 m);锐齿槲栎小种子被搬运后埋藏的距离最大(4.92 m)。2)除华山松种子外,其他类型种子被搬运后单个取食的比例均在85%以上;油松种子不存在埋藏点,而其他类型种子90%以上均以单个形式被埋藏。3)大部分种子被啮齿动物搬运后选择在裸地丢弃;锐齿槲栎大种子(87.5%)、小种子(78.57%)和华山松种子(53.33%)较大比例被啮齿动物埋藏在灌丛下方,埋藏在裸地的种子较少。4)大部分种子在灌丛下方被取食,仅华山松种子被啮齿动物搬运到洞穴取食;除油松种子被大量原地取食外,其他类型种子被搬运到取食点的种子比例基本呈现由微生境植被复杂到简单(灌丛—草丛—灌丛边缘—裸地)而逐渐减小的趋势。种子的营养价值及取食和搬运过程中啮齿动物付出的成本是影响种子命运的关键性因子,且啮齿动物对种子埋藏和取食地点的微生境存在较明显的选择性。     

Scatter‐hoarding and cache pilfering of rodents in response to seed abundance

Seed caching and reciprocal cache pilferage play an important role in the coexistence of food‐hoarding animals. Understanding what affects seed caching and how cache pilferage occurs is an important question in seed dispersal ecology. However, tracking seed fate and cache pilferage presents substantial practical difficulties. Siberian chipmunks Tamias sibiricus always remove the entire pericarp when scatter‐hoarding acorns of Mongolian oak Quercus mongolica, whereas wood mice Apodemus peninsulae often store whole acorns in their caches. These differences in behavior provide an opportunity to investigate unilateral cache pilferage of T. sibiricus from A. peninsulae in response to seed abundance. In this study, tagged acorns were released at the peak and end periods of seed rain from Q. mongolica. This allowed us to investigate seed caching and unilateral cache pilferage at different seed abundances. We found that a higher proportion of acorns were cached at lower level of seed abundance (toward the end of seed rain), mainly because T. sibiricus rather than A. peninsulae scatter‐hoarded significantly more acorns at this time. Cache distances decreased with increasing seed abundance, indicating that acorns were cached further away and into smaller caches at lower seed abundance. Unexpectedly, unilateral cache pilferage by T. sibiricus was not significantly influenced by seed abundance—remaining at around 28% during both periods of high and low seed abundance.     

Directed seed dispersal towards areas with low conspecific tree density by a scatter‐hoarding rodent

Scatter‐hoarding animals spread out cached seeds to reduce density‐dependent theft of their food reserves. This behaviour could lead to directed dispersal into areas with lower densities of conspecific trees, where seed and seedling survival are higher, and could profoundly affect the spatial structure of plant communities. We tested this hypothesis with Central American agoutis and Astrocaryum standleyanum palm seeds on Barro Colorado Island, Panama. We radio‐tracked seeds as they were cached and re‐cached by agoutis, calculated the density of adult Astrocaryum trees surrounding each cache, and tested whether the observed number of trees around seed caches declined more than expected under random dispersal. Seedling establishment success was negatively dependent on seed density, and agoutis carried seeds towards locations with lower conspecific tree densities, thus facilitating the escape of seeds from natural enemies. This behaviour may be a widespread mechanism leading to highly effective seed dispersal by scatter‐hoarding animals.     

Survival and Scatterhoarding of Frugivores-Dispersed Seeds as a Function of Forest Disturbance

The effect of forest disturbance on survival and secondary dispersal of an artificial seed shadow (N= 800) was studied at Brownsberg Natural Park, Suriname, South America. We scattered single seeds of the frugivore‐dispersed tree Virola kwatae (Myristicaceae), simulating loose dispersal by frugivores, in undisturbed and disturbed secondary forest habitats. Seed survival rate aboveground was high (69%) within 2 wk and was negatively correlated with scatterhoarding rate by rodents, the latter being significantly lower in the undisturbed forest (9%) than in the disturbed forest (20%). Postdispersal seed predation by vertebrates was low (3%) and infestation of seeds by invertebrates was almost zero in all instances. Therefore, secondary seed dispersal by rodents in forest is not as critical for recruitment as observed among other bruchid‐infested large‐seeded species. Secondary seed dispersal by rodents may, however, facilitate seedling recruitment whether cached seeds experience greater survival than seeds remaining above ground surface.     

贮藏种子的啮齿动物对油茶种子沉积形式的影响

种子沉积的质量常常涉及种子扩散作用者(如鸟类和小型啮齿动物)对生境和微生境的选择以及种子沉积的形式(如种子埋藏)。然而,很少的研究涉及到种子在离开母树后被这些动物沉积在何处。在四川省都江堰一个实验林场的2个林分(次生林和原生林)内,通过追踪用带编号的金属薄片标记的油茶(CamelliaoleiferaAbel.)种子的命运,研究了贮藏种子的啮齿动物对种子沉积的影响。研究发现在2个林分内,80%以上的种子被很好地埋藏在0~60mm深的土壤中,而小部分种子则被放置在地表(但有少量落叶遮盖)。小型啮齿动物喜好在灌丛下或灌丛边缘贮藏和取食种子,可能是在这样的微生境下它们在觅食时将遭遇较小的捕食风险。研究还发现,贮藏点的微生境分布随贮藏点等级而逐渐变化在两个林分内较高等级的贮藏点(如次贮藏点和三级贮藏点)比初级贮藏点有更多的种子被贮藏在灌丛下或灌丛边缘。这表明,啮齿动物对油茶种子的埋藏可能更有益于种子的存活、萌发以及幼苗的建成。啮齿动物将散落在母树下或其附近的油茶种子扩散到不同的微生境,这可能有利于他们遭遇到更多的适宜环境而萌发,实现幼苗补充。     

Effects of mast seeding and rodent abundance on seed predation and dispersal of <Emphasis Type="Italic">Quercus aliena</Emphasis> (Fagaceae) in Qinling Mountains,Central China

Rodents act as seed predators and dispersers and play an important role in the regeneration of plants. Seed production and rodent abundance may influence caching rodents’ decision to consume or cache seeds. We studied how did seed production and rodent abundance co-influence seed predation and dispersal by rodents in the mast seed years (2011 and 2013) and non-mast seed years (2012 and 2014) in the Qinling Mountains of Shaanxi Province, Central China. We found that: (1) The seed removal rates were much faster in the non-mast seed years than in the mast seed years. (2) Although the total number of seeds consumed (including eaten in situ and after removal) was higher in the non-mast seed years than in the mast seed years, no significant differences were found in the seeds that were eaten in situ and after removal among the 4 years. (3) Significant differences were observed in seeds that were cached among the 4 years, and more seeds were cached in the non-mast seed years than in the mast seed years. (4) The primary and secondary seed dispersal distances (including cached and eaten) were all longer in the non-mast seed years than in the mast seed years. Overall, these results indicate that non-mast seeding with low per capita seed availability could increase both seeds consumption and caching by rodents. Our results are partially supporting the predator satiation hypothesis.     

Unravelling the process of weed seed predation: Developing options for better weed control

Seed predation can cause significant losses of weed seeds in agricultural systems and can, thus, contribute to weed control. The removal of Lolium multiflorum and Vicia villosa seeds by harvester ants, Messor barbarus, and granivorous rodents, Mus spretus, in six cereal fields in NE Spain was separated into three sequential processes, namely (1) the probability of finding a seed cache (cache encounter rate), (2) the percentage of seeds utilized once a seed cache has been found (seed exploitation rate) and (3) seed selection if multiple species are present (preference). Identifying the most important behavioural component and factors that drive it may help to better understand and manage seed predation.Seed cache encounter rate correlated well with overall seed removal rate caused by harvester ants (r² = 0.91), or rodents (r² = 0.82). Once found, seed exploitation rates were high and fairly constant from spring to autumn for harvester ants, and low throughout the season for rodents. Harvester ants removed almost all L. multiflorum seeds from caches found, while the exploitation of V. villosa seeds varied across the season. In the case of rodents, cache encounter rate, but not exploitation rate, could be explained by canopy cover provided by the crop. L. multiflorum seemed to be preferred in early 2007, whereas V. villosa was in 2008.The adoption of no-till or minimum tillage systems together with the establishment of field edge vegetation are likely to encourage seed cache encounter and exploitation rates by both harvester ants and rodents, thus leading to increased weed control in semi-arid cereals.     

Post-dispersal predation and scatterhoarding of Dipteryx panamensis (Papilionaceae) seeds by rodents in Panama

In tropical rain forests of Central America, the canopy tree Dipteryx panamensis (Papilionaceae) fruits when overall fruit biomass is low for mammals. Flying and arboreal consumers feed on D. panamensis and drop seeds under the parent or disperse them farther away. Seeds on the ground attract many vertebrate seed-eaters, some of them potential secondary seed dispersers. The fate of seeds artificially distributed to simulate bat dispersal was studied in relation to fruitfall periodicity and the visiting frequency of diurnal rodents at Barro Colorado Island (BCI), Panama. The frequency of visits by agoutis is very high at the beginning of fruitfall, but in the area close (<50 m) to fruiting trees (Dipteryx-rich area) it declines throughout fruiting, whereas it remains unchanged farther (>50 m) away (Dipteryx-poor and Gustavia-rich area). Squirrels were usually observed in the Dipteryx-rich area. Along with intense post-dispersal seed predation by rodents in the Dipteryx-rich area, a significant proportion of seeds were cached by rodents in the Dipteryx-poor area. Post-dispersal seed predation rate was inversely related to hoarding rate. A significantly greater proportion of seeds was cached in March, especially more than 100 m from the nearest fruiting tree. This correlates with the mid-fruiting period, i.e. during the height of D. panamensis fruiting, when rodents seem to be temporarily satiated with the food supply at parent trees. Hoarding remained high toward April, i.e. late in the fruiting season of D. panamensis. Low survival of scatterhoarded seeds suggests that the alternative food supply over the animal's home-ranges in May–June 1990 was too low to promote survival of cached seeds. Seedlings are assumed to establish in the less-used area of the rodents' home-range when overall food supply is sufficient to satiate post-dispersal predators.