Big plants—do they limit species coexistence?

Aims According to conventional theory, larger plant species are likely to inflict more intense competition on other (smaller) species. We tested a deducible prediction from this: that a larger species should generally be expected to impose greater limits on the number of species that can coexist with it.Methods Species richness was sampled under plant canopies for a selection of woody species ('host' species) that display a wide range of adult sizes (from small shrubs to large trees), growing within natural vegetation of the Interior Douglas-fir zone of southern British Columbia, Canada. These data were compared with species richness levels sampled within randomly placed plots within the host species habitat.Important findings A prominent host species size effect on species richness was detected but only narrowly at the small end of the species size range. Across most (90%) of the increasing size range of host species, the number of species residing under the host canopy showed no significant decrease relative to the number expected by random assembly, based on species richness within randomly defined equivalent areas within the habitat of the host species. This apparent 'null effect', we suggest, is explained not because these larger species have no effect on community assembly. We postulate that larger species are indeed likely to be more effective in causing competitive exclusion of some smaller species (as expected from conventional theory), but that any potential limitation effect of this on resident species richness is offset for two reasons: (i) larger species also generate niche spaces that they cannot exploit under their own canopies and so have minimal impact (as competitors) on smaller species that can occupy these niches and (ii) certain other small species—despite small size—have effective competitive abilities under the severe competition that occurs within host neighbourhoods of larger species. These and other recent studies call for re-evaluation of traditional views on the role of plant size in affecting competitive ability and community assembly.     

The relationship between individual seed quality and maternal plant body size in crowded herbaceous vegetation

Aims In most natural plant populations, there is a strong right-skewed distribution of body sizes for reproductive plants—i.e. the vast majority are relatively small, suppressed weaklings that manage not just to survive effects of crowding/competition and other hazards but also to produce offspring. Recent research has shown that because of their relatively large numbers, these relatively small resident plants collectively contribute most of the seed offspring production available for the population in the next generation. However, the success of these offspring will depend in part on their quality, e.g. reflected by seed size and resource content. Accordingly, in the present study, we used material from natural populations of herbaceous species to test the null hypothesis that there is no significant relationship between body size variation in resident plants—resulting from between-site variation in the intensity of crowding/competition—and variation in the mass or N content of their individual seeds.Methods Using populations of 56 herbaceous species common in eastern Ontario, total above-ground dry plant mass, mean mass per seed and mean nitrogen (N) content per seed were recorded for a sample of the largest resident plants and also for the smallest reproductive plants growing in local neighbourhoods with the most severe crowding/competition from near neighbours.Important findings Mass per seed was numerically smaller from the smallest resident plants for most study species, but with few exceptions, this was not significantly different (P> 0.05) from mass per seed from the largest resident plants. The results therefore showed no general effect of maternal plant body size on individual seed mass, or N content. This suggests that the reproductive output of the smaller half of the resident plant size distribution within these populations is likely to contribute not just most of the seed production available for the next generation but also seed offspring that are just as likely—on a per individual basis—to achieve seedling/juvenile recruitment success as the seed offspring produced by the largest resident plants. This conflicts with the traditional 'size-advantage' hypothesis for predicting plant fitness under severe competition, and instead supports the recent 'reproductive-economy-advantage' hypothesis, where competitive fitness is promoted by capacity to produce offspring that—despite severe body size suppression imposed by neighbour effects—in turn have capacity to produce grand-offspring.     

长白山次生针阔混交林叶凋落物中有机物分解与碳、氮和磷释放的关系

采用分解袋法,研究了长白山次生针阔混交林内9种树种叶凋落物34个月的分解过程.结果表明:在次生针阔混交林中,不同树种叶凋落物的初始N和P浓度存在很大差异,叶凋落物分解速率(k)与初始N浓度和C/N显著相关.有机物剩余百分率与C剩余百分率呈显著的线性正相关关系,与N和P剩余百分率之间呈显著的二项式回归关系. N和P剩余百分率在初期阶段随有机物分解而增加,达到峰值后逐渐降低. 随着有机物剩余百分率的下降,C/N和C/P均呈逐渐降低趋势,各种叶凋落物之间C/N和C/P的差异逐渐减小,分解末期分别趋近于23和350. 随有机物剩余百分率的降低, N/P变化不明显,当有机物剩余百分率低于25%时,不同树种叶凋落物之间N/P差异显著下降. 有机物剩余百分率可用来预测C、N和P的剩余百分率.      

Enhanced Performance of the Eurostat Method for Comprehensive Assessment of Urban Metabolism: A Material Flow Analysis of Amsterdam

Sustainable urban resource management depends essentially on a sound understanding of a city's resource flows. One established method for analyzing the urban metabolism (UM) is the Eurostat material flow analysis (MFA). However, for a comprehensive assessment of the UM, this method has its limitations. It does not account for all relevant resource flows, such as locally sourced resources, and it does not differentiate between flows that are associated with the city's resource consumption and resources that only pass through the city. This research sought to gain insights into the UM of Amsterdam by performing an MFA employing the Eurostat method. Modifications to that method were made to enhance its performance for comprehensive UM analyses. A case study of Amsterdam for the year 2012 was conducted and the results of the Eurostat and the modified Eurostat method were compared. The results show that Amsterdam's metabolism is dominated by water flows and by port‐related throughput of fossil fuels. The modified Eurostat method provides a deeper understanding of the UM than the urban Eurostat MFA attributed to three major benefits of the proposed modifications. First, the MFA presents a more complete image of the flows in the UM. Second, the modified resource classification presents findings in more detail. Third, explicating throughput flows yields a much‐improved insight into the nature of a city's imports, exports, and stock. Overall, these advancements provide a deeper understanding of the UM and make the MFA method more useful for sustainable urban resource management.     

Use of climatic data to assess the effect of insect harassment on the autumn weight of reindeer (Rangifer tarandus) calves

Considerable behavioural evidence supports harassment by insects as the most important causal link between warm summer temperatures and low body condition of reindeer Rangifer tarandus , and that insect activity is influenced by weather condition. However, much less is known about the effect of insect harassment on individual performance, measured as reduced weight gain during summer, and the related consequences on both the reindeer pastoral economy and reindeer as a biological resource. Using climatic data, this paper develops a simple index for the analysis of insect harassment that takes into consideration weather variables known to significantly affect insect activity and/or the level of insect harassment. The insect harassment index, which is based on mid-day ambient temperature ≥13 °C, wind speed <6 m/s and cloud cover <40%, is further used to test the hypothesis that insect harassment has a negative effect on reindeer performance during summer in three Norwegian populations. Results show that harassment by insects negatively affects the autumn weight of reindeer calves, most probably through reduced grazing time and increased energy expenditure, but also indirectly by negatively influencing milk production of the dam. Moreover, female calves were more vulnerable to insect harassment than males. Insect harassment may have consequences on future reproductive performance, calving time, calf birth weight and hence neonatal mortality, and thus affect reindeer productivity. The presented index is easy to estimate and may be used to quantify and compare harassment levels on various reindeer summer grazing areas for management purposes. Our results also suggest that the expected temperature increase in the course of global warming may increase the insect-related stress on reindeer.     

岛礁型海洋生物保护区（IMPA）的设计和管理：理论和实例研究

本文提出和论述了岛礁型海洋生物保护区（ＩＭＰＡ）设计和管理的７条原则;生物多样性和稀缺性,生境典型性和完整性,物种－面积关系,海－陆生态交错带,人工自然化,生态脆弱性和自养型经济。并且结合我国第一个国家级海洋生物保护区－南麂列岛自然保护区（ＮＩＮＲ）设计和规划的实践,说明如何实施这些原则。     

城子崖遗址植硅体反映的生业经济模式

龙山文化是中国史前社会形态演进的关键阶段,亦是农业强化生产的关键时期。城子崖遗址是鲁北平原史前区域中心城址,其生业经济研究有助于理解该地区社会复杂化及文明进程。本文对城子崖遗址龙山时期不同遗迹单位的15份土样进行了系统的植硅体分析,尝试探讨了该遗址龙山文化时期的社会发展和生业经济水平、农作物生产和加工方式、野生植物资源利用情况以及各遗迹堆积及其所反映的人类行为活动信息。结果显示,该遗址龙山文化时期已形成粟、黍、稻、小麦、稗(可能)的农作物组合方式;同时,广泛采集利用聚落周边的自然植物资源,是农业与采集业并存发展的生业经济模式。先民在作物栽培中进行了锄草、灌溉等较为精细的管理,其中,黍较粟更具耐旱抗病特性,加上田间管理需求较低而被优先选择栽培。先民在收获作物时,采用类似割穗、掐穗等方法以减少作物茎秆及杂草混入,随后在户外进行小规模地脱壳、扬场工作。此外,根据灰坑中植硅体的组合特征可将其分为生活垃圾、谷物加工、蓄水淘米三个类型,水井和墓葬内的植硅体则分别与生活环境和丧葬环节等信息相关。     

中国区域生态经济水平与区域竞争力的关联性与实证研究

通过生态意义下区域竞争力的研究,提出了经济自由空间的概念.在进行模型静态和动态的分析后,得出科技的进步对区域潜在竞争力具有决定性作用的结论.在实证研究方面,运用因子分析的方法,根据生态水平、人均国内生产总值和生态科技进步等13个指标,对全国31个省（自治区、直辖市）的生态经济水平以及区域竞争力进行了排名.结果发现,由于经济发展水平和自然生态环境等原因,在生态意义下我国各个区域的区域竞争力也成空间上的东、中、西分布格局.在上述理论和实证探讨的基础上,还分别就生态条件下区域发展的公平和效率以及生态条件下有关不发达地区的区域政策进行了探讨.认为生态条件下,如果政策制定不得当,不发达地区会处于更加不平等的地位,所以政策制定者应该重新认识传统的区域理论和区域政策.     

中国产业共生发展模式的国际比较及对策

产业共生和生态工业园区已经成为世界范围内产业生态化转型的重要手段之一。在厘清产业共生发展模式内涵的基础上,借鉴商业模式的划分准则辨识了世界范围内6种产业共生模式:丹麦卡伦堡模式、美国模式、英国模式、日本模式、韩国模式和中国模式。从关键参与者、核心能力以及资金流3个维度对这些模式进行了辨识,重点比较了我国产业共生与其他模式的差别。研究表明,我国产业共生实践数量众多,在关键参与主体、核心能力培育和资金流等方面存在丰富的多样化,虽然形成了一定的中国特色,但并没有形成固定的"中国模式"。可以说,我国的产业共生实践还停留在初级阶段,下一步可持续的发展必须要建立合理的管制架构、形成稳定的资金支持机制和培育核心竞争能力。初级提出了我国产业共生和生态工业园区建设的政策建议。