全新世早期中国长江下游地区橡子和水稻的开发利用

最近发掘的浙江上山和小黄山遗址(11400—8000cal BP)是长江下游地区迄今发现最早的村落遗址。这两个遗址均出土有大量磨石, 而有机物遗存保存很少。本文对7件石器进行了淀粉粒、植硅体以及矿物残留物的初步分析, 以便检验这些方法在复原古代生计形态和器物功能研究中的可行性。鉴定出的淀粉粒包括橡子、根茎类、薏苡以及疑似菱角等, 但是没有发现水稻。在发现的水稻植硅体中, 来自茎杆和叶的密度较高, 而来自颖壳的密度较低。矿物分析表明残留物来自工具的使用以及周围的土壤基质。结果显示这些磨石曾经用于加工富含淀粉的植物和制陶用的羼和料。我们认为, 对富含淀粉并且适于长期贮存的植物特别是橡子的大量开发利用是全新世早期长江下游地区生计形态中采集策略的特征。本研究显示了淀粉粒和植硅体分析在古代生计重建中的巨大潜力。对这些遗址残留物的进一步研究将有助于我们更好地理解这一地区从采集经济到定居农耕经济的转变。     

Acorns containing deeper plumule survive better: how white oaks counter embryo excision by rodents

Several squirrel species excise the embryo of acorns of most white oak species to arrest germination for long‐term storage. However, it is not clear how these acorns counter embryo excision and survive in the arms race of coevolution. In this study, we simulated the embryo excision behavior of squirrels by removing 4 mm of cotyledon from the apical end of white oak acorns differing in embryo depths to investigate the effects of embryo excision on acorn germination and seedling performance of white oak species. The embryo depth in the cotyledons was significantly different among white oak acorns, with Quercus mongolica containing the embryo most deeply in the acorns. We found that artificial embryo excision significantly decreased acorn germination rates of Quercus variabilis, Quercus acutissima, Quercus aliena, Quercus aliena var. acutiserrata, Quercus serrata. var. brevipetiolata but not Q. mongolica. Artificial embryo excision exerted significant negative impacts on seedling performance of all oak species except Quercus aliena. Our study demonstrates the role of embryo depth of acorns in countering embryo excision by squirrels and may explain the fact that squirrels do not perform embryo excision in acorns of Q. mongolica with deeper embryos. This apparent adaptation of acorns sheds light on the coevolutionary dynamics between oaks and their seed predators.     

Removal of water turbidity by natural coagulants obtained from chestnut and acorn

The ability of seed extracts of several species of chestnut and acorn to act as natural coagulants was tested using a synthetic turbid water. Active components were extracted from ground seeds of Horse chestnut and acorns of some species of family Fagaceae: Common oak, Turkey oak, Northern red oak and European chestnut. All investigated extracts had coagulation capabilities and their amounts depended on pH values and initial turbidities. The seed extracts from European chestnut and Common oak acorn were the most efficient expressing the highest coagulation activities, about 80% and 70%, respectively, in both low and medium investigated water turbidities at the lowest coagulant dose 0.5 ml/L.     

Context dependence of acorn handling by the Algerian mouse (Mus spretus)

Perceived predation risk and competition for acorns are expected to affect scatter-hoarding decisions by Algerian mice (Mus spretus). We manipulated both factors by means of predator fecal scents and ungulate exclosures. We hypothesized that high-risk perception and ungulate presence would promote acorn dispersal. In the former case, it would stimulate acorn mobilization to safe microhabitats rather than in situ consumption. In the latter, increased competition for acorns would promote their storage for later consumption. We also expected that mice would adapt their foraging behavior to previous experience modulating the strength of these effects.In the presence of ungulates, mice focused their foraging activities on food acquisition at the expenses of vigilant behaviors. However, a more efficient foraging did not entail enhanced dispersal services. Lack of anti-predatory cover in tree surroundings may have deterred mice from transporting seeds outside canopies. Increased risk interacted with previous experience. In control trees (no predator odor), mice confidence increased throughout the night resulting in decreased vigilance and enhanced acorn mobilization rates. In contrast, in risky conditions (trees with predator odor) mice maintained a base-line vigilant behavior. Contrary to our expectations, increased risk did not result in higher acorn mobilization, but the opposite. Again, the scarcity of safe microhabitats for mobilization may have been the underlying cause of this behavior.Our results show that successful acorn dispersal depends, at least partly, on plant-animal relationships that are beyond the oak-rodent mutualism. Thus, any conservation policy aimed at restoring natural regeneration of oaks should take into account the interaction network in which oak-rodent encounters are embedded. In addition, they suggest that mice incorporate direct and indirect cues of risks (habitat structure) through recent experience. A better understanding of this process will improve our ability to incorporate such temporal and spatial variability in models of acorn dispersal.     

A novel nest‐monitoring camera system using a Raspberry Pi micro‐computer

The utility, availability, cost‐effectiveness, and reliability of prefabricated video systems designed to monitor wildlife have lagged behind the unique and varied needs of many researchers. Many systems are limited by inflexible video settings, lack of adequate data storage, and cannot be programmed by the user. More sophisticated systems can be cost prohibitive, and the literature describing remote wildlife video monitoring has, for the most part, not incorporated advances in camera and computer technology. Here, we present details of a pilot study to design and construct a lower cost (US $340) nest camera system to record the behavior of Acorn Woodpeckers (Melanerpes formicivorus) in artificial tree cavity nests. This system incorporates a Raspberry Pi micro‐computer, Pi NoIR infrared camera, a wireless adapter to transmit video over the Internet, and Deka rechargeable gel batteries for power. We programmed the system to motion‐sense, to record exclusively during daylight hours, and to automatically upload videos to the cloud over wireless Internet. The Raspberry Pi micro‐computer does not require advanced programming or electrical engineering skills to build and configure and, because it is programmable, provides unprecedented flexibility for field researchers who wish to configure the system to the specific needs of their study.     

Acorn preference under field and laboratory conditions by two flightless Iberian dung beetle species (Thorectes baraudi and Jekelius nitidus): implications for recruitment and management of oak forests in central Spain

1. Recently, a mutualistic relationship has been described between some dung beetles (Thorectes lusitanicus and Mycotrupes lethroides) and oak species (Quercus suber, Q. canariensis, and Q. rubra), which could be crucial for ensuring seedling recruitment and sustaining the equilibrium of oak populations. For T. lusitanicus, a diet based on acorns during the reproductive period improved resistance to low‐temperature conditions and improved ovarian development. 2. In this paper, we conducted field and laboratory experiments to investigate the interaction between two potential acorn‐eating beetles, Thorectes baraudi and Jekelius nitidus, with Quercus suber. We determined the feeding preferences of both beetle species and estimated the rates of acorn manipulation by beetles according to habitat structure and several characteristics of the acorn, such as seed size and acorn infestation by weevils. 3. Results demonstrated the positive interaction between the dung beetle Thorectes baraudi and Quercus trees. Thorectes baraudi was clearly more attracted to volatiles of acorns than to dung. Jekelius nitidus, on the contrary, was either not or anecdotally attracted to acorns. On the contrary, in the case of Jekelius nitidus, the acorn attraction could be considered anecdotal or even accidental. Our field results demonstrated the acorn burying behaviour of T. baraudi in the oak forests of the Cabañeros National Park (Spain), suggesting a potential role of this beetle species as an active secondary acorn disperser. 4. This unexpected behaviour could be particularly important in Mediterranean oak forests and savannahs, where most Quercus species are strongly recruitment limited because of serious overgrazing problems.     

Quantitative analysis of acorn transportation by rodents using magnetic locator

Transported distance and mortality of acorns scattered by rodents were investigated with magnets inserted into acorns (40 of Quercus serrata and 20 of Quercus acutissima) and a magnetic locator in a natural forest stand. All the treated acorns were transported, and 60% of them were discovered again with a magnetic locator from autumn to the next spring. Most transported acorns suffered predation within one month after the start of the experiment. Several acorns were rehoarded at least two or three times. Average transported distance of scattered acorns was 22.1±8.9 m (max=38.5 m) and the survival rate was 3.0%. The magnet method is one of the most effective methods for tracking acorns through the winter.     

Oaks, acorns, and the geographical ecology of acorn woodpeckers

We investigated the geographical ecology of acorn woodpeckers (Melanerpes formicivorus) using 30 years of Audubon Christmas Bird Counts and data on the diversity and abundance of oaks. Spatial autocorrelation in acorn woodpecker population densities is not significantly greater than zero both in either the southwestern United States, where populations are often locally isolated, or along the Pacific Coast, where they are more evenly distributed. In both regions, the effective distributional limit of acorn woodpeckers is set not by the limits of oaks but by sites where oak diversity drops to a single species. This result is consistent with acorn production patterns in central coastal California demonstrating that variability in overall acorn production and the probability of acorn crop failure decline with increasing oak species number but drop most markedly when two, compared to one, species of oaks are present together. Along the Pacific Coast, acorn woodpecker densities increase and population variability decreases with increasing abundance and diversity of oaks; however, analyses indicate that overall population size in this region is primarily determined by resource abundance while population stability is determined by resource diversity. Comparable patterns are not obvious in the Southwest, where acorn woodpecker densities are much lower than along the Pacific Coast. This may be due to a combination of greater competition for resources and oak communities that differ both qualitatively and quantitatively in their productivity compared to those along the Pacific Coast.