The role of climate and plant functional trade‐offs in shaping global biome and biodiversity patterns

Aim Two of the oldest observations in plant geography are the increase in plant diversity from the poles towards the tropics and the global geographic distribution of vegetation physiognomy (biomes). The objective of this paper is to use a process‐based vegetation model to evaluate the relationship between modelled and observed global patterns of plant diversity and the geographic distribution of biomes. Location The global terrestrial biosphere. Methods We implemented and tested a novel vegetation model aimed at identifying strategies that enable plants to grow and reproduce within particular climatic conditions across the globe. Our model simulates plant survival according to the fundamental ecophysiological processes of water uptake, photosynthesis, reproduction and phenology. We evaluated the survival of an ensemble of 10,000 plant growth strategies across the range of global climatic conditions. For the simulated regional plant assemblages we quantified functional richness, functional diversity and functional identity. Results A strong relationship was found (correlation coefficient of 0.75) between the modelled and the observed plant diversity. Our approach demonstrates that plant functional dissimilarity increases and then saturates with increasing plant diversity. Six of the major Earth biomes were reproduced by clustering grid cells according to their functional identity (mean functional traits of a regional plant assemblage). These biome clusters were in fair agreement with two other global vegetation schemes: a satellite image classification and a biogeography model (kappa statistics around 0.4). Main conclusions Our model reproduces the observed global patterns of plant diversity and vegetation physiognomy from the number and identity of simulated plant growth strategies. These plant growth strategies emerge from the first principles of climatic constraints and plant functional trade‐offs. Our study makes important contributions to furthering the understanding of how climate affects patterns of plant diversity and vegetation physiognomy from a process‐based rather than a phenomenological perspective.     

Functional trade‐offs increase species diversity in experimental plant communities

Functional trade‐offs have long been recognised as important mechanisms of species coexistence, but direct experimental evidence for such mechanisms is extremely rare. Here, we test the effect of one classical trade‐off – a negative correlation between seed size and seed number – by establishing microcosm plant communities with positive, negative and no correlation between seed size and seed number and analysing the effect of the seed size/number correlation on species richness. Consistent with theory, a negative correlation between seed size and seed number led to a higher number of species in the communities and a corresponding wider range of seed size (a measure of functional richness) by promoting coexistence of large‐ and small‐seeded species. Our study provides the first direct evidence that a seed size/number trade‐off may contribute to species coexistence, and at a wider context, demonstrates the potential role of functional trade‐offs in maintaining species diversity.     

西南山地红外相机监测网络建设进展

中国西南山地是全球生物多样性热点区。西南山地红外相机监测网络是我国生物多样性监测的区域性红外相机网络之一。该网络由北京大学牵头, 始建于2002年, 合作单位包括科研院所、高校、保护组织、政府部门、保护地管理机构等。网络主要覆盖青藏高原东缘大横断山区域的秦岭、岷山、邛崃山、相岭、凉山、沙鲁里山、云岭7大山系。网络内目前共有41个监测样区, 包括自然保护区、社区保护地、林场等多种类型。网络内监测样区均采用标准的网格化布设规程, 采取统一数据结构与数据库结构、建立离散式数据库进行分散管理的总体架构, 所有监测样区的数据库保持一致的结构和统一的核心字段, 由每个监测样区建立并维护各自独立的数据库。截至2019年12月, 网络内布设有效调查/监测位点5,738个, 已处理数据中调查工作量(以有效相机日计)合计约120.74万天, 积累红外相机照片/视频(删除连续空拍后) 302.59万份, 另有111.16万份待处理。共记录到分属7目21科的63种野生哺乳动物与分属10目35科的182种野生鸟类物种, 其中国家一、二级重点保护野生动物分别有18与39种。西南山地网络今后的重点工作方向包括: (1)基于通用元数据结构建立统一的在线数据库平台; (2)加强网络内保护地数据管理与分析能力建设; (3)为区域内生物多样性保护与保护地管理提供持续支持; (4)针对野生动物种间关系、群落构建机制以及大型食肉动物的生态功能开展深入的动物生态学研究。     

Habitat‐related seed germination traits in alpine habitats

Understanding the key aspects of plant regeneration from seeds is crucial in assessing species assembly to their habitats. However, the regenerative traits of seed dormancy and germination are underrepresented in this context. In the alpine zone, the large species and microhabitat diversity provide an ideal context to assess habitat‐related regenerative strategies. To this end, seeds of 53 species growing in alpine siliceous and calcareous habitats (6230 and 6170 of EU Directive 92/43, respectively) were exposed to different temperature treatments under controlled laboratory conditions. Germination strategies in each habitat were identified by clustering with k‐means. Then, phylogenetic least squares correlations (PGLS) were fitted to assess germination and dormancy differences between species’ main habitat (calcareous and siliceous), microhabitat (grasslands, heaths, rocky, and species with no specific microhabitats), and chorology (arctic–alpine and continental). Calcareous and siliceous grasslands significantly differ in their germination behaviour with a slow, mostly overwinter germination and high germination under all conditions, respectively. Species with high overwinter germination occurs mostly in heaths and have an arctic–alpine distribution. Meanwhile, species with low or high germinability in general inhabit in grasslands or have no specific microhabitat (they belong to generalist), respectively. Alpine species use different germination strategies depending on habitat provenance, species’ main microhabitat, and chorotype. Such differences may reflect adaptations to local environmental conditions and highlight the functional role of germination and dormancy in community ecology.     

Loss of adaptation following reversion suggests trade‐offs in host use by a seed beetle

Experimental evolution has provided little support for the hypothesis that the narrow diets of herbivorous insects reflect trade‐offs in performance across hosts; selection lines can sometimes adapt to an inferior novel host without a decline in performance on the ancestral host. An alternative approach for detecting trade‐offs would be to measure adaptation decay after selection is relaxed, that is, when populations newly adapted to a novel host are reverted to the ancestral one. Lines of the seed beetle Callosobruchus maculatus rapidly adapted to a poor host (lentil); survival in lentil seeds increased from 2% to > 90% in < 30 generations. After the lines had reached a plateau with respect to survival in lentil, sublines were reverted to the ancestral host, mung bean. Twelve generations of reversion had little effect on performance in lentil, but after 25–35 generations, the reverted lines exhibited lower survival, slower development and smaller size. The most divergent pair of lines was then assayed on both lentil and mung bean. Performance on lentil was again much poorer in the reverted line than in the nonreverted one, but the lines performed equally well on mung bean. Moreover, the performance of the nonreverted line on mung bean remained comparable to that of the original mung‐bean population. Our results thus present a paradox: loss of adaptation to lentil following reversion implies a trade‐off, but the continued strong performance of lentil‐adapted lines on mung bean does not. Genomic comparisons of the reverted, nonreverted and ancestral lines may resolve this paradox and determine the importance of selection vs. drift in causing a loss of adaptation following reversion.     

Seeds of future past: climate change and the thermal memory of plant reproductive traits

Plant persistence and migration in face of climate change depends on successful reproduction by seed, a central aspect of plant life that drives population dynamics, community assembly and species distributions. Plant reproduction by seed is a chain of physiological processes, the rates of which are a function of temperature, and can be modelled using thermal time models. Importantly, while seed reproduction responds to its instantaneous thermal environment, there is also evidence of phenotypic plasticity in response to the thermal history experienced by the plant's recent ancestors, by the reproducing plant since seedling establishment, and by its seeds both before and after their release. This phenotypic plasticity enables a thermal memory of plant reproduction, which allows individuals to acclimatise to their surroundings. This review synthesises current knowledge on the thermal memory of plant reproduction by seed, and highlights its importance for modelling approaches based on physiological thermal time. We performed a comprehensive search in the Web of Science and analysed 533 relevant articles, of which 81 provided material for a meta‐analysis of thermal memory in reproductive functional traits based on the effect size Zr. The articles encompassed the topics of seed development, seed yield (mass and number), seed dormancy (physiological, morphological and physical), germination, and seedling establishment. The results of the meta‐analysis provide evidence for a thermal memory of seed yield, physiological dormancy and germination. Seed mass and physiological dormancy appear to be the central hubs of this memory. We argue for integrating thermal memory into a predictive framework based on physiological time modelling. This will provide a quantitative assessment of plant reproduction, a complex system that integrates past and present thermal inputs to achieve successful reproduction in changing environments. The effects of a warming environment on plant reproduction cannot be reduced to a qualitative interpretation of absolute positives and negatives. Rather, these effects need to be understood in terms of changing rates and thresholds for the physiological process that underlie reproduction by seed.     

干热河谷植物叶片,树高和种子功能性状比较

植物功能性状 (plant functional trait)是近年来生态学研究的热点。以云南怒江和澜沧江干热河谷36种木本植物为研究对象,选取比叶面积 (SLA)、植株高 (H) 和种子干重 (SM) 3个功能性状,研究它们的相互关系,比较其在河谷间、河谷内的差异。结果表明:1)两个河谷内36种木本植物的以上3种功能性状间没有显著的相关性 (P值分别为0.8739,0.5763,0.5517);2)河谷间的比叶面积存在显著差异 (P=0.02944),植株高和种子干重无显著差异 (P分别为0.4070, 0.8867);3)两个河谷内木本植物功能性状中,种子干重差异最大,植株高次之,比叶面积最小。     

Interspecific variation in persistence of buried weed seeds follows trade‐offs among physiological,chemical, and physical seed defenses

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Multiple trade‐offs regulate the effects of woody plant removal on biodiversity and ecosystem functions in global rangelands

Woody plant encroachment is a major land management issue. Woody removal often aims to restore the original grassy ecosystem, but few studies have assessed the role of woody removal on ecosystem functions and biodiversity at global scales. We collected data from 140 global studies and evaluated how different woody plant removal methods affected biodiversity (plant and animal diversity) and ecosystem functions (plant production, hydrological function, soil carbon) across global rangelands. Our results indicate that the impact of removal is strongly context dependent, varying with the specific response variable, removal method, and traits of the target species. Over all treatments, woody plant removal increased grass biomass and total groundstorey diversity. Physical and chemical removal methods increased grass biomass and total groundstorey biomass (i.e., non‐woody plants, including grass biomass), but burning reduced animal diversity. The impact of different treatment methods declined with time since removal, particularly for total groundstorey biomass. Removing pyramid‐shaped woody plants increased total groundstorey biomass and hydrological function but reduced total groundstorey diversity. Environmental context (e.g., aridity and soil texture) indirectly controlled the effect of removal on biomass and biodiversity by influencing plant traits such as plant shape, allelopathic, or roots types. Our study demonstrates that a one‐size‐fits‐all approach to woody plant removal is not appropriate, and that consideration of woody plant identity, removal method, and environmental context is critical for optimizing removal outcomes. Applying this knowledge is fundamental for maintaining diverse and functional rangeland ecosystems as we move toward a drier and more variable climate.     

Functional trait trade‐off and species abundance: insights from a multi‐decadal study

Phylogenetically informed trait comparisons across entire communities show promise in advancing community ecology. We use this approach to better understand the composition of a community of winter annual plants with multiple decades of monitoring and detailed morphological, phenological and physiological measurements. Previous research on this system revealed a physiological trade‐off among dominant species that accurately predicts population and community dynamics. Here we expanded our investigation to 51 species, representing 96% of individual plants recorded over 30 years, and analysed trait relationships in the context of species abundance and phylogenetic relationships. We found that the functional‐trait trade‐off scales to the entire community, albeit with diminished strength. It is strongest for dominant species and weakens as progressively rarer species are included. The trade‐off has been consistently expressed over three decades of environmental change despite some turnover in the identity of dominant species.     

Synergies and trade‐offs between renewable energy expansion and biodiversity conservation – a cross‐national multifactor analysis

Increased deployment of renewable energy can contribute towards mitigating climate change and improving air quality, wealth and development. However, renewable energy technologies are not free of environmental impacts; thus, it is important to identify opportunities and potential threats from the expansion of renewable energy deployment. Currently, there is no cross‐national comprehensive analysis linking renewable energy potential simultaneously to socio‐economic and political factors and biodiversity priority locations. Here, we quantify the relationship between the fraction of land‐based renewable energy (including solar photovoltaic, wind and bioenergy) potential available outside the top biodiversity areas (i.e. outside the highest ranked 30% priority areas for biodiversity conservation) within each country, with selected socio‐economic and geopolitical factors as well as biodiversity assets. We do so for two scenarios that identify priority areas for biodiversity conservation alternatively in a globally coordinated manner vs. separately for individual countries. We show that very different opportunities and challenges emerge if the priority areas for biodiversity protection are identified globally or designated nationally. In the former scenario, potential for solar, wind and bioenergy outside the top biodiversity areas is highest in developing countries, in sparsely populated countries and in countries of low biodiversity potential but with high air pollution mortality. Conversely, when priority areas for biodiversity protection are designated nationally, renewable energy potential outside the top biodiversity areas is highest in countries with good governance but also in countries with high biodiversity potential and population density. Overall, these results identify both clear opportunities but also risks that should be considered carefully when making decisions about renewable energy policies.     

珍稀植物连香树在其中国分布区北缘的种子性状及幼苗更新限制

连香树(Cercidiphyllum japonicum)是第三纪孑遗植物, 存在严重的幼苗更新限制。为验证生活史早期(种子萌发)限制中国分布区北缘连香树种群幼苗更新, 并探讨其主要成因, 本研究在秦岭和太行山脉采集不同种源地的种子, 测定其形态性状、营养元素含量和质量、不同贮存时间的活力及不同温度条件下的萌发性状, 通过方差分析、相关分析等方法对不同种源地的种子性状进行分析。结果表明: 在中国分布区北缘, 其种子长度(P < 0.001)、萌发率(P < 0.001)、平均萌发时间(P < 0.001)、氮(P < 0.05)和磷含量(P < 0.001)在不同种源间存在显著差异; 而在区域尺度上(秦岭与太行山), 仅种子碳含量存在显著差异(P < 0.01)。天水种群的种子萌发率最高(21.77%), 平均萌发时间最长(11.12 d); 栾川的萌发率最低(1.38%), 平均萌发时间最短(3.47 d)。在25℃条件下, 济源种群的种子萌发率显著高于10℃、15℃和20℃条件下(P < 0.05), 而其他种源地的萌发率在不同温度条件下无显著差异。在4个温度条件下, 栾川种群种子的初始萌发时间无显著差异, 而其他4个种源地的初始萌发时间都随温度升高而缩短。相关分析结果表明, 种子萌发率与种子活力密切相关, 而种子活力与种子质量、种子的氮和磷含量显著相关。在中国分布区北缘, 连香树种子的自身属性(质量、氮和磷含量)通过影响种子活力间接影响萌发率; 且种子萌发对温度的响应主要表现在萌发时间上。本研究证实种子萌发是限制连香树种群幼苗更新的关键阶段, 主要原因如下: (1)连香树种子在9月成熟后, 10月的温度仍适宜种子萌发, 但较短生长期的幼苗在冬季低温下不能存活; (2)连香树种子萌发率低(14.4%); (3)第二年春天种子活力骤降。     

Yield vs. Quality trade‐offs for wheat in response to carbon dioxide and ozone

Although it is established that there exist potential trade‐offs between grain yield and grain quality in wheat exposed to elevated carbon dioxide (CO₂) and ozone (O₃), their underlying causes remain poorly explored. To investigate the processes affecting grain quality under altered CO₂ and O₃, we analysed 57 experiments with CO₂ or O₃ exposure in different exposure systems. The study covered 24 cultivars studied in 112 experimental treatments from 11 countries. A significant growth dilution effect on grain protein was found: a change in grain yield of 10% by O₃ was associated with a change in grain protein yield of 8.1% (R² = 0.96), whereas a change in yield effect of 10% by CO₂ was linked to a change in grain protein yield effect of 7.5% (R² = 0.74). Superimposed on this effect, elevated CO₂, but not O₃, had a significant negative effect on grain protein yield also in the absence of effects on grain yield, indicating that there exists a process by which CO₂ restricts grain protein accumulation, which is absent for O₃. Grain mass, another quality trait, was more strongly affected by O₃ than grain number, whereas the opposite was true for CO₂. Harvest index was strongly and negatively influenced by O₃, but was unaffected by CO₂. We conclude that yield vs. protein trade‐offs for wheat in response to CO₂ and O₃ are constrained by close relationships between effects on grain biomass and less than proportional effects on grain protein. An important and novel finding was that elevated CO₂ has a direct negative effect on grain protein accumulation independent of the yield effect, supporting recent evidence of CO₂‐induced impairment of nitrate uptake/assimilation. Finally, our results demonstrated that processes underlying responses of grain yield vs. quality trade‐offs are very different in wheat exposed to elevated O₃ compared with elevated CO₂.     

不同居群准噶尔无叶豆果实和种子特性及种子萌发差异

研究准噶尔无叶豆(Eremosparton songoricum) 6个居群间果实和种子特性及种子萌发差异, 以揭示异质生境下准噶尔无叶豆果实和种子的生态适应机制。结果显示: 居群间准噶尔无叶豆的植株距离(F = 2.34, p = 0.03)和植株冠幅(F = 8.49, p < 0.01)存在显著差异, 沙漠北缘E、F居群和沙漠腹地C居群(受人类干扰剧烈)的植株距离和植株冠幅高于沙漠腹地A、B、D居群; 居群间准噶尔无叶豆果实和种子的长度、宽度、厚度、重量存在显著差异, 居群E、F和C的大部分参数显著高于其他沙漠腹地居群; 居群间果实多子性(F = 6.96, p < 0.01)也存在显著差异, 居群C的果实多子性最高((32.50 ± 4.79)%); 萌发结果表明, 居群间新鲜的成熟种子萌发不存在显著差异, 且萌发率都低于15%; 所有居群的大部分种子都存在物理性休眠现象, 人为划破种皮能显著提高种子萌发率, 但在低温(15/5 ℃)条件下, 所有居群的种子萌发率都较低, 说明低温抑制了种子萌发; 经人为划破种皮解除物理休眠后, 种子的休眠没有完全释放, 居群C、E和F (大种子居群)的种子萌发率显著高于居群A、B和D (小种子居群) (F = 30.77, p < 0.01), 说明准噶尔无叶豆种子不仅存在物理性休眠现象, 也可能存在生理休眠现象。不同程度的种子复合休眠可能是准噶尔无叶豆不同居群适应古尔班通古特沙漠的重要生存策略。     

高黎贡山南段种子植物区系的特有现象

高黎贡山南段是全球生物多样性研究热点地区之一,迄今计有野生种子植物192科878属2 807种.这一区域不仅植物的种类丰富,而且特有现象较为显著.其中东亚特有科8个、中国特有属17个、中国特有种1 085个、云南特有种305个、高黎贡山南段特有种82个.特殊地质历史和生态环境,使得高黎贡山南段既保留了许多古老特有成分,又孕育了许多新生特有成分.     

天山云杉种子形态性状的地理变异

以新疆天山山脉从西到东不同经度3个地点(昭苏、天池和奇台)的天山云杉林为对象,沿海拔梯度采集不同地点的天山云杉球果,分析其种子性状(种鳞长、种鳞宽、种鳞长宽比、种翅长、种翅宽、种翅长宽比、种子长、种子宽和种子长宽比)的变化.结果表明: 随海拔的升高,天山云杉种子性状(种子宽除外)总体呈现下降的趋势;除种翅宽、种子宽和种子长宽比与海拔的相关性不显著外,种子其他性状与海拔均呈显著负相关;种鳞长、种鳞宽、种鳞长宽比与经度呈现显著正相关;种鳞长、种鳞长宽比、种翅长宽比与坡度呈显著负相关;除种翅宽外,种子其他性状与坡向相关性均不显著.海拔是影响天山云杉种子的种鳞长、种鳞长宽比和种翅长宽比的主要因子.