纳罗克非洲狗尾草种子产量构成因子分析

为了解纳罗克非洲狗尾草单株种子产量构成因子,探索提高种子产量的解决途径,试验选择7个纳罗克非洲狗尾草单株种子产量构成因子;另取4个单株穗子10等分,从基部依次编为1-10号,试验中脱落的种子为11号。单株种子产量构成因子相关性分析结果表明,纳罗克非洲狗尾草单株种子产量(W)与生殖枝数(X₃)呈极显著正相关(P<0.01),与分蘖数(X₂)呈显著正相关(P<0.05);多元逐步回归单株种子产量W=-16.59156+0.42479X₃-0.03082X₅+0.04923X₆。对穗子不同部位的种子分析结果表明,试验中脱落的种子11号质量最好,其次为7号种子。不同部位的种子产量以1、3、8号种子产量较高,而9、10号种子产量最低。提示,纳罗克非洲狗尾草穗子中部的种子产量较为稳定,产量也较高,而穗尾1/3部的产量最低,收种时应确定以穗子中部的种子成熟为最佳收种时机。     

Rodent abundance triggered switch between the relative mutualism and predation in a rodent–seed system of the subtropical island forest

Density-dependent non-monotonic species interactions are important in maintaining ecosystem stability and function, but empirical evidences are still rare. Rodents, as both seed dispersers and seed predators, have dual effects on plant regeneration and may result in non-monotonic rodent-plant interactions. According to the non-monotonic models, the relative positive or negative effects of rodents on seedling establishment can be measured based on the positive or negative association of seedling recruitment rate and rodent abundance. In this study, we investigated the fates of acorns of Quercus serrata by tracking tagged seeds on 21 fragmented subtropical islands in the Thousand Island Lake, China. We found that the proportion of germinated seeds of all released seeds showed a dome-shaped association with rodent abundance per seed. The proportion of removed seeds and cached seeds showed a saturated- and a weak dome-shaped association with rodent abundance per seed, respectively. Our results demonstrated a clear empirical evidence that rodent abundance per seed triggered a switch between the relative mutualism and predation in a rodent–seed system. Our study implied that the observed non-monotonic interactions between plants and animals may play a significant role in maintaining biodiversity and ecosystem function. We appeal for more investigations of the complex non-monotonic interactions in various ecosystems.     

不同生境下柠条种子出苗及幼苗生长特征

为了揭示柠条种群实生更新的机制及其影响因素,在宁夏白芨滩自然保护区的人工柠条灌丛群落,设置不同的灌丛(柠条灌丛、沙蒿灌丛和裸露沙地)基部生境、不同坡位(底部、中部和顶部)的沙丘生境和柠条灌丛植株基部不同距离(0.5,1.5m和丛间沙地)生境,研究了柠条种子在不同生境下的出苗和幼苗生长特征。结果表明,1)不同生境(柠条灌丛、沙蒿灌丛和裸露沙地)和沙埋处理对柠条种子出苗率和留存率均具有显著影响(P0.05);在沙蒿灌丛,沙埋种子的早期出苗率显著高于地表种子(P0.05),且显著高于裸露沙地和柠条灌丛的沙埋种子(P0.05);种子的出苗率在沙蒿灌丛的沙埋处理最高,但不同生境间、沙埋和非沙埋种子间的差异均未达到显著水平。2)沙丘底部的种子出苗率显著大于沙丘顶部(P0.01),试验结束时约为沙丘顶部的20倍;各时期出苗率均在距柠条灌丛基部1.5m处最大,灌丛间沙地最小,沙丘不同部位生境的出苗率均在7月18日最高,整个试验期间的出苗率和出苗速率在不同生境间均无显著差异。3)幼苗株高、基径、主根长、根茎比和总干质量均在沙丘底部最大,而根冠比在沙丘顶部最大;距灌丛基部0.5m处幼苗的株高显著大于1.5m处幼苗(P0.05),幼苗主根长、根茎比和根冠比均随距灌丛距离的增大而增大,而总干质量随灌丛距离的增大而减小。     

去除果皮和晒种处理对红豆草种子萌发特性的影响

试验研究了去除果皮和晒种处理对红豆草种子(荚果)萌发特性的影响。结果表明:和对照相比,去除果皮处理显著缩短了红豆草种子的初次发芽时间,且显著提高了发芽率、发芽指数、活力指数和根、芽生长,显著降低了发霉率;晒种处理能显著促进未去掉果皮红豆草种子(荚果)的萌发。晒种1~3d对去掉果皮的红豆草种子的发芽率和发霉率无显著影响(P0.05)。去掉果皮晒种2、3d处理红豆草种子的发芽率显著高于未去皮晒种0d(对照),发霉率显著低于对照(P0.05),发芽指数和活力指数显著高于去掉果皮晒种0d和1d,初次发芽时间比对照提前2d,其根长和芽长显著高于对照(P0.05);经过去掉果皮和晒种的红豆草种子在室内贮存75d后其发芽指数、根长、芽长均有所降低,而发芽率却有所增加。试验得出,去除红豆草种子(荚果)果皮并晒种2~3d能显著促进其萌发、降低发霉率,而且短期(75d)贮藏后其发芽率未降低。     

Exclusion of interspecific competition reduces scatter‐hoarding of Siberian chipmunk Tamias sibiricus: A field study

Although food availability and the abundance of seed predators have been postulated to affect seed dispersal, it is not clear how seed‐eating animals modify their scatter‐hoarding strategies in response to different levels of interspecific competition. We placed paired germinated and ungerminated acorns of Quercus mongolica on 30‐cm high platforms to exclude potential interspecific competition of the predominant larder hoarders Apodemus peninsulae and Myodes rufocanus, to investigate seed dispersal by a predominant scatter‐hoarder, Tamias sibiricus, in the field in north‐eastern China. Our results showed that T. sibiricus ate more acorns in situ in the absence of interspecific competition. In the presence of interspecific competition of A. peninsulae and C. rufocanus, however, more acorns were scatter‐hoarded by T. sibiricus. Regardless of interspecific competition, germination of acorns showed no significant effects on seed dispersal patterns, inconsistent with the “seed perishability hypothesis” that animals avoid hoarding seeds with high perishability. Exclusion of interspecific competition, though relatively increasing the per capita seed abundance, appears to reduce seed dispersal, scatter‐hoarding and seedling establishment. Therefore, we propose that moderate interspecific competition rather than competition exclusion may benefit seed scatter‐hoarding and seedling establishment.     

赤霉素及机械处理的相互作用对破除Sandersonia aurantiaca种子休眠的研究

在预备试验的基础上，选用了21种促进种子发芽的方法，结果显示，完整的s．aurantiaca种子对任何处理都无响应，砂纸磨擦 近胚根处切除小部分可使种子发芽率提高至11％。以上处理结合300mg／L GA3溶液的使用可破除种子休眠，使种子发芽率提高到69％以上。结果还表明，S．aurantiaca种子发芽的适宜温度为20℃；25℃ 16h／d光照及30℃的条件可降低种子的发芽率。研究还对S．aurantiaca种子的吸胀能力以及所含抑制物对生菜种子发芽的影响进行了比较。初步得出，S．aurantiaca种子具有种皮限制和种胚休眠的双重休眠机制，GA3和机械处理的相互作用可破除种子休眠。     

施氮肥对高羊茅种子质量和产量组成的影响

2000-2001年在新疆塔里木农垦大学牧草试验站进行了施氮肥对交战高羊茅种子质量和产量组成影响的研究。结果表明,施氮可以明显提高种子的活力和质量,并增加了单位面积的生殖枝数和小花数／小穗;施氮肥提高了种子产量,其中以秋季60kg／hm^2 春季120kg／hm^2施氮量为最好,种子产量可达1653．9kg／hm^2。     

Dispersal of invasive Phytolacca americana seeds by birds in an urban garden in China

Although seed dispersal is a key process determining the regeneration and spread of invasive plant populations, few studies have explicitly addressed the link between dispersal vector behavior and seedling recruitment to gain insight into the invasion process within an urban garden context. We evaluated the role of bird vectors in the dispersal of pokeweed (Phytolacca americana), a North American herb that is invasive in urban gardens in China. Fruiting P. americana attracted both generalist and specialist bird species that fed on and dispersed its seeds. The generalist species Pycnonotus sinensis and Urocissa erythrorhyncha were the most frequent dispersers. Seedling numbers of P. americana were strongly associated with the perching behavior of frugivorous birds. If newly recruited bird species use seedling‐safe perching sites, the P. americana will regenerate faster, which would enhance its invasive potential. Based on our observations, we conclude that the 2 main bird vectors, P. sinensis and U. erythrorhyncha, provide potential effective dispersal agents for P. americana. Our results highlight the role of native birds in seed dispersal of invasive plants in urban gardens.     

土壤种子库中棘豆属种子的密度、寿命和活力测定

在青海湖地区的不同样地上,对甘肃棘豆、宽苞棘豆和黄花棘豆3种棘豆土壤种子库的密度进行了测定,种子密度随着植被中种群分盖度的大小而变化幅度很大,每平方80～2 220粒;同时采用四脞法对土壤种子库中的棘豆种子进行种子活力测定,其中77%的种子具有活力;用尼龙袋法测定甘肃棘豆种子在土壤种子库中的寿命,5年后埋置在土壤环境中的甘肃棘豆种子有50%的还存在,其中5%的种子具有活力;暴露在土壤表面环境中的种子有33%的种子存在;5年期间,埋置的种子和暴露在土壤表面的种子每年分别约有5%和14%的种子在发芽。     

碱茅种子发芽检测标准方法的研究

于2008年以碱茅(Puccinellia distans Parl)种子为材料,研究在10-25℃、10-30℃、15-25℃、15-30℃、20-30℃变温处理和15℃、20℃、25℃、30℃恒温以及预处理条件下,筛选确定碱茅种子发芽的最适温度和光照条件条件,为碱茅种子质量检测的标准化提供参考依据。结果表明:碱茅种子在20-30℃ 8h高温光照16h低温黑暗条件下发芽率最高,预处理对碱茅种子发芽无显著影响。碱茅种子发芽计数时间确定为第7d进行初次计数,第14d进行末次计数。并在此温度条件下选用5个碱茅种子样品进行发芽测定,可以反映碱茅种子的发芽水平,而且硝酸钾和预先冷冻处理对碱茅种子发芽促进作用不明显。