啮齿动物对秦岭松栎混交林建群种种子扩散格局的影响

森林群落中的啮齿动物对林木种子存在着一定的取食偏好性,这种偏好性会使啮齿动物形成不同的捕食和贮藏策略,从而导致林木种子形成不同的扩散格局。以秦岭中段松栎混交林建群种锐齿槲栎、油松、华山松为研究对象,采用塑料标签标记种子方法,研究啮齿动物对种子传播和扩散格局的影响。结果表明:(1)种子特征是影响啮齿动物对其进行扩散的重要因子,油松种子以其质量小、种皮薄等特点吸引啮齿动物大量捕食,其原地取食率达到83.33%,显著高于华山松和锐齿槲栎种子。(2)锐齿槲栎和华山松种子大部分被搬运一定距离后再被取食和埋藏,其中,扩散距离在1 m以内、1—3 m和5—8 m的锐齿槲栎种子分别占59.12%、18.23%和13.26%,最远扩散距离达12 m处;华山松种子扩散距离主要介于在1—3 m(37.85%)和3—5 m(23.73%),在距离5—8 m(13.56%)、8—10 m(11.86%)和大于10 m(11.30%)区间也有一定的分布,最大扩散距离为12 m。(3)啮齿动物倾向于将锐齿槲栎种子搬运至松林内取食,而将华山松种子搬运至栎林内埋藏,说明不同林分类型及其环境因素对林木种子扩散后的分布格局具有重要影响。(4)3种类型种子被啮齿动物捕食的比例以油松最大(96.90%),锐齿槲栎次之(73.57%),华山松最小(50%);次年调查时,未被捕食的种子大部分已经被取食,仅有极少数锐齿槲栎种子萌发成幼苗(1.67%)。啮齿动物的捕食和贮藏行为对林木种子扩散及其成功更新都至关重要。     

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。     

不同干扰强度生境中啮齿动物对苦槠种子的取食和扩散

在浙江省千岛湖地区,选择了受人类活动干扰较轻、中度和严重的3个生境,采用金属片标记法研究了啮齿动物对苦槠种子的取食和扩散.结果表明:在研究点捕获的取食种子的啮齿动物为针毛鼠( Niviventer fulvescens),尽管捕获的数量少,但种子被取食和扩散的速率很快,3个样地内的种子均在2d内被取食或扩散完毕;中等干扰强度的生境中,被就地取食的种子最多,占鉴别种子总数的37.8%.种子扩散距离大多<5m,最大扩散距离为24.76m,3个样地种子扩散均符合负指数分布,且样地间没有显著差异;饱满种子与虫蛀种子被就地取食与搬运后取食的命运没有显著差异,但饱满种子的最大扩散距离均显著大于虫蛀种子(P<0.05),除中等干扰样地中饱满种子与虫蛀种子平均扩散距离没有显著差异外,其余2个样地中饱满种子的平均扩散距离均显著大于虫蛀种子,显示啮齿动物对饱满种子与虫蛀种子有一定的区分能力.     

围栏条件下同域分布三种鼠对两种种子的贮藏行为差异

种子贮藏是啮齿动物利用食物资源的一种适应性行为。同域分布的啮齿动物可能进化出不同的贮藏方式和策略。为了解同域分布的啮齿动物的贮藏策略及种子特征在动物贮藏行为决策中的作用,于2014年10-12月,通过半自然围栏实验,在秦岭南坡的佛坪国家级自然保护区内调查了同域分布社鼠、中华姬鼠和甘肃仓鼠对板栗和锐齿槲栎种子的贮藏策略差异,并探讨了2种种子特征在鼠类贮藏行为决策中的作用。结果显示：1）社鼠主要集中贮藏板栗种子,未分散贮藏任何种子;中华姬鼠未贮藏板栗种子,对锐齿槲栎种子同时表现出集中和分散贮藏行为,以集中贮藏为主;甘肃仓鼠对2种种子均表现出集中贮藏行为,未表现分散贮藏行为。2）社鼠和甘肃仓鼠均倾向于集中贮藏有较高营养价值（高蛋白和脂肪）且单宁含量较低的板栗种子;中华姬鼠倾向于分散贮藏单宁含量高的锐齿槲栎种子。3）3种鼠均喜好取食有较高营养价值且单宁含量低的板栗种子,很少取食单宁含量高的锐齿槲栎种子。结果表明同域分布鼠类对不同种子的贮藏方式有所不同,种子特征影响鼠类的取食和贮藏策略。     

季节变化对锐齿栎种子扩散的影响

季节变化是影响鼠类扩散植物种子的一个主要环境因素.2008年9-11月(秋季)和2009年3-4月(春季)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锐齿栎种子的扩散,并与种子大小年假说的预测进行了比较分析.结果表明:春季锐齿栎种子的扩散速度比秋季快,平均扩散距离(取食距离和贮藏距离)也比秋季远,该结果与种子...     

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。     

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。     

锐齿槲栎林的天然更新——坚果、幼苗库和径级结构

对四川茂县地区的锐齿槲栎(Quercus aliena var.acuteserrata)天然次生林进行研究,发现(1)坚果完好比例约在14%～26%之间,完好坚果的发芽率和发芽势都比较高,但在天然状况下能够留存到隔年5月的坚果几乎没有.因此,实生幼苗的天然补充就受到了严重的限制.(2)林缘的幼苗密度低于所有其它生境的(p＜0.05),林中的幼苗密度最高,和林窗的比较有显著差异(p＜0.05),而和灌丛的比较则没有差异.在灌丛幼苗密度和林中以及林窗的比较都没有差异.动物对坚果的取食速度则是林中的最慢(10.0%),林窗和林缘的相同(分别为61.1%和66.5%),都比较快(p＜0.01).(3)林中的幼苗在小于100 cm的各高度内都有大量分布,说明在林中树冠下幼苗是可以长期存在的,在幼苗和种子阶段的锐齿槲栎可能是耐荫的.(4)在林中缺失幼树,在林缘则有包括幼树在内的完整的更新大小系列,表明林缘也可以成为更新的关键地点.(5)在栎林的每一个大小级别上,萌生个体和实生个体都按各种比例伴生,说明导致萌生的干扰一直在发生,并可能在森林的更新中扮演重要角色;也说明该地区的锐齿槲栎林由萌生和实生起源的个体混合组成.     

啮齿动物对印度栲种子扩散的效率

从2007 年11 月到2009 年11 月,在西双版纳热带雨林中选取三棵母树,在每棵树下每年释放标记印度栲种子200 粒(三年共计1 800 粒),并追踪其命运。通过调查啮齿动物搬运和分散贮藏印度栲种子的比例,以及
查贮藏种子的微生境、贮藏点大小和扩散距离,分析贮藏种子的存活情况,进而评估啮齿动物对印度栲种子扩散的效率。结果表明,啮齿动物搬运了69.3% 的印度栲种子,被搬运的种子中18% 被分散贮藏。所有被分散贮藏的种子均被埋于落叶下或埋于土壤表层,并且大部分贮藏点仅含一粒种子。种子的扩散距离从0.5 m 到43.8 m,平均距离为7.1 m,扩散距离在年间没有显著差异。2007 年(种子密度低,啮齿动物密度高) 没有种能最终存活到实验结束,而2008 和2009 年(种子密度高,啮齿动物密度低)分别有0.3% 和1.5% 的种子存活。研究表明,啮齿动物是印度栲有效的种子扩散者,但其扩散效率很大程度上取决于森林中种子的密度和啮齿动物的丰富度。     

种子特征和结实量对啮齿动物取食和扩散种子行为的影响

为了深入了解啮齿动物在不同种子丰富度条件下对不同大小和单宁含量种子的觅食行为策略及其与植物种群更新的关系,在宁夏六盘山区的华北落叶松人工林,研究了不同大小和单宁含量[0%Tannin(T)、2%T、8%T和15%T]的人工种子在模拟结实小年和结实大年对啮齿动物取食和扩散行为的影响.结果表明: 啮齿动物消耗种子速度在结实小年更快,结实大年的种子消耗速度相对缓慢. 种子就地取食率(ISPR)在不同结实年份间无显著差异,扩散后取食率(PRAD)在结实小年显著高于结实大年,但前者的扩散后贮藏率(HRAD)显著低于后者;种子扩散后的取食距离(PDAD)和贮藏距离(HDAD)在结实小年均显著大于结实大年.在结实小年,大种子的PDAD和HDAD均大于小种子,前者在不同大小种子间均差异显著,而后者仅在2%T和15%T的不同大小种子间差异显著;在结实大年,除0%T外的其他单宁含量种子的PDAD和HDAD在不同大小种子间均差异显著.ISPR在中等单宁含量种子最大,高单宁含量种子最小;PRAD分别在结实小年的高单宁含量种子和结实大年的无单宁种子最大;不论在结实大年还是结实小年,HRAD均在高单宁含量种子最大,中等单宁含量种子最小.这说明结实大年可延缓啮齿动物对种子的消耗速率,提高种子的HRAD,但种子扩散距离减小;啮齿动物在结实大年和小年均表现出对大种子的扩散偏好,且大种子被扩散的距离更远;啮齿动物在不同结实年份均偏好于就地取食中等单宁含量种子,而扩散高单宁含量种子.     

小果野芭蕉种子散布和不同时空尺度上种子被捕食格局

 以分布在云南西双版纳地区的大型先锋草本植物小果野芭蕉(Musa acuminata)为研究材料,研究其种子初次散布过程和不同时空尺度上种子被 捕食格局。小果野芭蕉的成熟果实有75%在夜间被取食和传播,在白天消失的果实则占25%。蝙蝠是其最主要的种子传播者,鸟类在其种子传播 过程中也起到一定的作用。人工摆放种子试验结果显示小果野芭蕉种子的主要转移者是小型啮齿类(鼠类)和蚁类：在开放处理下3 d后转移率为 86%,排除蚁类(鼠类可进入)处理下种子转移率为69%以及排除鼠类(蚂蚁可进入)处理下种子被转移率为56%。季节、地点和生境均显著影响人工 摆放种子被转移强度：雨季显著高于旱季(p<0.001), 野芭蕉生境显著高于与其相连的自然森林和荒地(p<0.001),在人为干扰较少的补蚌自然 保护区显著低于西双版纳热带植物园和新山,而后两者之间并无显著差异(p>0.05)。同时,地点和生境以及季节、地点和生境都有显著的交互 作用。与相邻的森林和荒地相比,野芭蕉群落中种子被鼠类捕食的强度最大且受蚁类二次转移的比例最少,森林和荒地中种子被鼠类捕食的强 度相对较小且蚁类对种子的二次转移比例较高,从而更好地帮助种子逃避鼠类捕食。因此,依赖于食果动物(主要是蝙蝠, 也包括鸟类)的初次 散布是小果野芭蕉种子逃避捕食的关键。     

浙江天童山鼠类对栲树种子的捕食和扩散

在浙江天童山国家森林公园,研究了鼠类在常绿阔叶林、马尾松林和灌丛几种生境内对栲树（Castanopsis fargesii）种子的捕食和扩散的影响.结果表明,社鼠（Niviventer confucianus）和针毛鼠（N.fulvescens）是栲树种子的主要捕食者.种子在刚布下后的几天内消失的最快,随后其日消失率便逐渐降低,在不同生境中,其日消失率也有所不同,在灌丛中日消失率最高（7.54%）,其次是马尾松林（7.29%）,而常绿阔叶林中3条样带的日消失率较低.在损失的种子中,各种种子命运所占比例在样带中存在着差异,灌丛中失踪的种子比例最高,占97.77%,而样带2的则最低,只占8.91%.这与不同样带中的植被组成密切相关.同时,鼠类对栲树种子扩散的距离比较近,观察到的最远扩散距离为12.7 m.     

亚热带林区啮齿动物对樱桃种子捕食和搬运的作用格局

在都江堰林区,通过在原生林、次生林和灌丛3类生境释放野生和栽培樱桃(Cerasus pseudocerasus)的种子,研究了啮齿动物对樱桃种子的捕食及其对樱桃种群更新的作用。结果表明,啮齿动物对樱桃两类种子的搬运无显著差异,而啮齿动物对野生樱桃种子的收获则明显快于栽培樱桃种子,且在3类生境均有类似的趋势。这说明啮齿动物偏爱于收获具有较高收益(种仁重/种子重)的野生樱桃种子。啮齿动物在小于10 d的时间尺度收获了所有释放的樱桃种子,其中,70%以上为啮齿动物所搬运。春季食物的匮乏可能是导致啮齿动物对樱桃种子有较大捕食压力的主要原因,而生境类型间的差异较小。因此,啮齿动物是都江堰林区樱桃地表种子的主要捕食者,它们对野生樱桃种子的选择性捕食和搬运能影响樱桃种子/果实的进化及其种群更新。     

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.     

The effects of seed abundance on seed predation and dispersal by rodents in <Emphasis Type="Italic">Castanopsis fargesii</Emphasis> (Fagaceae)

Based on the animal dispersal hypothesis and the predator satiation hypothesis, we examined the effects of seed abundance at both population (i.e., mast seeding) and community levels on seed predation and dispersal of Castanopsis fargesii (Fagaceae), a rodent-dispersed mast species in Eastern Asia. In a subtropical evergreen broadleaved forest in the Dujiangyan region of Sichuan Province, China, individual seeds with coded tin tags were tracked in two contrasting stands (seed-poor and seed-rich) over two years (2000, a low-seed year; 2001, a high-seed year). Our results showed that: (1) small rodents did not harvest the tagged seeds of C. fargesii more rapid in the high-seed year than in the low-seed year in either stand. But, seed harvest was significantly faster in the seed-rich stand than in the seed-poor stand. (2) The removal proportion was significantly lower in the high-seed year than in the low-seed year for either stand, but the removal proportion was slightly higher in the seed-poor stand than in the seed-poor stand. This indicates that high seed abundance decreases seed removal (predator satiation hypothesis). (3) There were only small differences about seed caching, seed survival and seedling establishment of C. fargesii between years and stands. During the survey, no cached seeds survived to geminate in the spring for both stands and years. (4) Mean dispersal distances of the cached seeds are much shorter in the high-seed year (3.1 m) than in the low-seed year (8.1 m) in the seed-rich stand, though similar trend is not examined in the seed-poor stand. Our results indicate that seed predation and dispersal of C. fargesii are influenced by both mast seeding and community-level seed abundance, which is not completely consistent with either the animal dispersal hypothesis or the predator satiation hypothesis, but seems more related to the predator satiation hypothesis.     

Multiple stages of tree seedling recruitment are altered in tropical forests degraded by selective logging

Tropical forest degradation is a global environmental issue. In degraded forests, seedling recruitment of canopy trees is vital for forest regeneration and recovery. We investigated how selective logging, a pervasive driver of tropical forest degradation, impacts canopy tree seedling recruitment, focusing on an endemic dipterocarp Dryobalanops lanceolata in Sabah, Borneo. During a mast‐fruiting event in intensively logged and nearby unlogged forest, we examined four stages of the seedling recruitment process: seed production, seed predation, and negative density‐dependent germination and seedling survival. Our results suggest that each stage of the seedling recruitment process is altered in logged forest. The seed crop of D. lanceolata trees in logged forest was one‐third smaller than that produced by trees in unlogged forest. The functional role of vertebrates in seed predation increased in logged forest while that of non‐vertebrates declined. Seeds in logged forest were less likely to germinate than those in unlogged forest. Germination increased with local‐scale conspecific seed density in unlogged forest, but seedling survival tended to decline. However, both germination and seedling survival increased with local‐scale conspecific seed density in logged forest. Notably, seed crop size, germination, and seedling survival tended to increase for larger trees in both unlogged and logged forests, suggesting that sustainable timber extraction and silvicultural practices designed to minimize damage to the residual stand are important to prevent seedling recruitment failure. Overall, these impacts sustained by several aspects of seedling recruitment in a mast‐fruiting year suggest that intensive selective logging may affect long‐term population dynamics of D. lanceolata. It is necessary to establish if other dipterocarp species, many of which are threatened by the timber trade, are similarly affected in tropical forests degraded by intensive selective logging.     

The Interplay of Habitat and Seed Type on Scatterhoarding Behavior in a Fragmented Afromontane Forest Landscape

Scatterhoarding by rodents, whereby seeds are collected and stored for later consumption, can result in seed dispersal. Seeds may be covered in litter on the forest floor (cached) or buried. This is particularly so in the Neotropics for large, nutritious seeds, and where primary dispersers are rare or missing. In African forests, contemporary anthropogenic pressures such as hunting, forest degradation, and fragmentation are contributing toward major declines in large frugivores, yet the potential for scatterhoarding to mitigate this loss is largely unknown. In this study, we used thread‐marked seed to explore the balance between seed predation and dispersal by rodents in Afromontane forest. We studied two tree species in three habitats: (1) continuous forest; (2) continuous forest edge, and (3) small, degraded riparian forest patches. We found that seed removal rates were high and almost the same in all three habitats for both tree species, but that the predation/dispersal balance differed among habitats. In continuous forest, more seeds of each species were scatterhoarded than depredated, and rates of scatterhoarding differed between the two species. In all habitats, burying seeds up to 2 cm belowground was more common than caching. Distances seeds were moved was approximately five times greater in continuous forest than in forest edge or riparian patches. We found strong evidence to suggest that the African pouched rat, Cricetomys sp. nov was responsible for the scatterhoarding.     

Effects of Logging on the Genetic Diversity of Quercus tiaoloshanica Chun et Ko in a Tropical Montane Forest of Hainan Island, Southern China

Quercus tiaoloshanica Chun et Ko, which has a narrow range of distribution, is one of the important endemic species of the tropical montane rain forest on Hainan Island, southern China. Long-term logging and habitat destruction have resulted in population decline and distribution retreat of Q. tiaoloshanica. To determine the impact of logging on the genetic diversity of Q. tiaoloshanica, the authors investigated the genetic structures using amplified fragment length polymorphism markers in four regenerated stands after logging and in one unlogged stand. Compared with the unlogged stand, the effective number of alleles per locus dropped by 1.0% in selective logging stands and by 2.0% in clear logging stands, corresponding to reductions of 3.8% and 5.2%, respectively, in mean Nei＇s gene diversity and 2.9% and 3.5%, respectively, in mean Shannon diversity index. No substantial genetic erosion was detected in any of the regenerated stands owing to the high tree density and high heterogeneity of the Q. tiaoloshanica stands investigated. Meanwhile, there was no natural regeneration of the species observed in a Dacrydium pierrei Hickel plantation 700 m away from the regenerated stands, suggesting the limited ability of seed dispersal of Q. tiaoloshanica. Clear logging should be undertaken cautiously because the total number of plant species dropped by 15.2% in the clear-logged stands compared with the unlogged stand. To conserve the genetic diversity of this species, as well as the plant biodiversity of tropical forests, the habitats of Q. tiaoloshanica should be protected against exploitation in terms of agricultural or other forms of land use, and some mature trees should be preserved as seed sources to maintain an adequate regeneration base for this species in the management of logging.