International principles and standards for native seeds in ecological restoration

The growing demand for native seeds in ecological restoration and rehabilitation, whether for mining, forest, or ecosystem restoration, has resulted in a major global industry in the sourcing, supply, and sale of native seeds. However, there are no international guidance documents for ensuring that native seeds have the same standards of quality assurance that are regular practice in the crop and horticultural industries. Using the International Principles and Standards for the Practice of Ecological Restoration as a foundation document, we provide for the first time a synthesis of general practices in the native seed supply chain to derive the Principles and Standards for Native Seeds in Ecological Restoration (“Standards”). These practices and the underpinning science provide the basis for developing quality measures and guidance statements that are adaptable at the local, biome, or national scale. Importantly, these Standards define what is considered native seed in ecological restoration and highlight the differences between native seeds versus seeds of improved genetics. Seed testing approaches are provided within a logical framework that outline the many different dormancy states in native seed that can confound restoration outcomes. A “pro‐forma” template for a production label is included as a practical tool that can be customized for local needs and to standardize reporting to end‐users on the level of seed quality and germinability to be expected in a native seed batch. These Standards are not intended to be mandatory; however, the guidance statements provide the foundation upon which regulatory approaches can be developed by constituencies and jurisdictions.     

A comparative study of seed yield parameters in Arabidopsis thaliana mutants and transgenics

Because seed yield is the major factor determining the commercial success of grain crop cultivars, there is a large interest to obtain more understanding of the genetic factors underlying this trait. Despite many studies, mainly in the model plant Arabidopsis thaliana, have reported transgenes and mutants with effects on seed number and/or seed size, knowledge about seed yield parameters remains fragmented. This study investigated the effect of 46 genes, either in gain- and/or loss-of-function situations, with a total of 64 Arabidopsis lines being examined for seed phenotypes such as seed size, seed number per silique, number of inflorescences, number of branches on the main inflorescence and number of siliques. Sixteen of the 46 genes, examined in 14 Arabidopsis lines, were reported earlier to directly affect in seed size and/or seed number or to indirectly affect seed yield by their involvement in biomass production. Other genes involved in vegetative growth, flower or inflorescence development or cell division were hypothesized to potentially affect the final seed size and seed number. Analysis of this comprehensive data set shows that of the 14 lines previously described to be affected in seed size or seed number, only nine showed a comparable effect. Overall, this study provides the community with a useful resource for identifying genes with effects on seed yield and candidate genes underlying seed QTL. In addition, this study highlights the need for more thorough analysis of genes affecting seed yield.     

Foreword: International Standards for Native Seeds in Ecological Restoration

Restoration practitioners must increasingly incorporate seed procurement models and seed use planning early in project development, despite insufficient guidance about what are reasonable expectations for the sourcing and use of native seeds. This special issue presents a series of articles examining each key step in the native seed supply chain, and provides a framework for the “standards” that need to be applied to native seed batches if the native seed supply chain is to achieve the levels of reliability and transparency required. These Standards provide seed buyers, end users, and funding bodies with a level of confidence and reliability in the sourcing of quality native seeds, and a pathway toward global best practice in native seed use.     

Seed Rain in High-Altitude Restoration Plots in Switzerland

Seed rain was studied in restoration plots installed in 1985 and 1987, respectively, on an alpine downhill ski run at circa 2,500 m above sea level. The study was initiated in late autumn 1996 and completed in autumn 1998; it included temporal and spatial variation in density per m², as well as alpha diversity (species richness), and species composition of the seed rain versus that of the resident vegetation. This is the first report on post-restoration monitoring of seed rain above the timberline. Seed rain density and alpha diversity varied seasonally, with the first peak occurring immediately after spring snowmelt and the second in early autumn. The density of seed rain varied between plots and years (1,528–1,778 seeds per m² in one plot [RPF] versus 1,096–3,557 seeds per m² in another plot [RPG]). Total species number per plot was nearly twice as high in RPF as in RPG in both study years. Seed rain totaled 18 species; all but one represented either transplants introduced in restoration or colonizers established in the plots soon after restoration. Distribution of species in seed rain was largely asymmetric and only a few species provided substantial contributions. Composition of species and their respective contribution to seed rain differed between plots and was clearly influenced by performance of some species used in restoration as transplants; together they provided as much as 51% of the total seed rain. The results of the study demonstrate that restoration enhanced increase of species richness as well as seed rain in situ.     

Lack of adequate seed supply is a major bottleneck for effective ecosystem restoration in Chile: friendly amendment to Bannister et al. (2018)

We argue that the need for a quality seed supply chain is a major bottleneck for the restoration of Chile's native ecosystems, thus supplementing the list of bottlenecks proposed by Bannister et al. in 2018. Specifically, there is a need for defining seed transfer zones, developing standards and capacities for properly collecting and storing seeds, reducing information gaps on seed physiology and longevity, and implementing an efficient seed supply chain with certification of seed origin and quality. Without such capacities, countries are unlikely to meet their restoration commitments. Although we focus on bottlenecks in Chile, the issues we raise are relevant to other countries and thus the global agenda for ecological restoration.     

Seed dynamics of resprouting shrubs in grassy woodlands: Seed rain,predators and seed loss constrain recruitment potential

Abstract Measuring the fate of seeds between seed production and seedling establishment is critical in understanding mechanisms of recruitment limitation of plants. We examined seed fates to better understand the recruitment dynamics of four resprouting shrubs from two families (Fabaceae and Epacridaceae) in temperate grassy woodlands. We tested whether: (i) pre‐dispersal seed predation affected seed rain; (ii) post‐dispersal seed predation limited seed bank accumulation; (iii) the size of the seed bank was related to seed size; and (iv) viable seeds accumulated in the soil after seed rain. There was a distinct difference in seed production per plant between plant families with the legumes producing significantly more seeds per individual than the epacrids. Seed viability ranged from 43% to 81% and all viable had seed or fruit coat dormancy broken by heat or scarification. Pre‐dispersal predation by Lepidopteran larvae removed a large proportion of seed from the legume seed rain but not the epacrids. Four species of ants (Notoncus ectatomoides, Pheidole sp., Rhytidoponera tasmaniensis and Iridomyrmex purpureus) were major post‐dispersal seed removers. Overall, a greater percentage of Hardenbergia (38%) and Pultenaea (59%) seeds were removed than the fleshy fruits of Lissanthe (14%) or Melichrus (0%). Seed bank sizes were small (<15 seeds m^?2) relative to the seed rain and no significant accumulation of seed in the soil was detected. Lack of accumulation was attributed to seed predation as seed decay was considered unlikely and no seed germination was observed in our study sites. Our study suggests that seed predation is a key factor contributing to seed‐limited recruitment in grassy woodland shrubs by reducing the number of seeds stored in the soil.     

壳斗科三种植物种子大小对昆虫寄生及种子存活率的影响

种子内的寄生昆虫可以严重影响种子的发育、损害种子活力。种子足余策略理论认为大种子有利于抵御和适应昆虫寄生取食,但动物最优觅食理论推测,大种子更易遭受昆虫寄生。为对这两种对立观点进行验证,本实验以青冈、苦槠和麻栎各2个种群的种子为材料,对昆虫寄生与完好种子间的体积和萌发率进行比较,并对寄生种子萌发率与种子体积的关系进行了分析。结果显示:(1)在6个种群的种子中,只有松阳麻栎和青冈种群的寄生种子体积大于完好种子,其余4个种群的寄生种子体积小于完好种子,但这种差异不显著;(2)所有寄生种子的整体萌发率(18%)显著低于完好种子(45.66%)(P<0.001),在不同种群内,寄生种子的萌发率也分别显著低于完好种子。(3)比较同种植物体积差异显著的寄生种子的萌发率发现,大种子总比小种子具有更高的萌发率,但差异不显著;在不同植物的寄生种子间比较时,体积最大的麻栎种子萌发率显著高于体积较小的青冈和苦槠种子。研究结果表明,象虫在种子上产卵时对大种子没有选择偏好,在昆虫寄生取食严重损害种子活力的压力下,大种子比小种子具有更强的耐受力。     

江西三清山濒危植物天女花种子特性研究

研究了江西三清山天女花种子的特性,结果表明：(1)三清山天女花种群种子雨自10月初开始,10月末结束,10月中旬强度达高峰,玉京峰地段天女花种子雨持续时间较短;(2)产种率受母树冠层影响,即上层>中层>下层;种子败育率高(49.4%～100.0%);(3)主成分分析表明,乔木层盖度、大气湿度、光照因子以及土壤含水量对天女花种子发育产生显著影响。     

How policies constrain native seed supply for restoration in Brazil

Large‐scale ecological restoration programs across the world involve a voluminous demand for native seeds of diverse native plant species. In this article, we explore how institutional systems have operated and impacted native seed supply in Brazil. Native seed supply for restoration is essentially a community‐based activity which faces broad barriers to operating within regulations because of requirements for excessive and costly technical documentation, scarcity of seed laboratories, and lack of instructions for native seed quality testing. Although decentralized seed networks have stimulated arrangements for local organizations to promote seed supply, policies constrain the development of local capacities and the ongoing sustainability of these organizations. These conditions have resulted in a vast network of informal collectors and producers who are largely “invisible” and unknown to the regulatory authorities. Policies have decentralized responsibilities from the state without devolving decision‐making power to the multiple stakeholders engaged in policy elaboration. The policies maintain the centralized regulation of native seed supply. After examining Brazilian seed networks' experiences and conducting discussions with stakeholders and experts, we suggest adapting the current regulations to more local level contexts, encompassing the following strategies: (1) ensuring native seed origin and identity; (2) relaxation of the laboratory accreditation process for native seed quality assurance; (3) fostering seed markets for restoration; (4) research to provide technological innovation; (5) supporting local, diverse, and small seed‐based businesses.     

香果树(Emmenopterys henryi)种群种子雨、种子库及 实生苗数量的海拔梯度变化

香果树为我国Ⅱ级野生保护植物,由于原生境中香果树种群的数量迅速减少,目前已濒临灭绝,种群亟待恢复。研究了武夷山不同海拔的香果树种群种子雨、种子库及其幼苗存活现状,目的是阐明不同海拔地区的香果树种群自然更新的动态过程,寻找其更新脆弱的环节及其影响因素,为香果树自然种群的恢复提供理论依据。以分布于不同海拔高度（819、980、1 140及1 301 m）的香果树母树为中心,在其周围（东、南、西、北四个方位）布设种子雨收集框和土壤种子库样方,连续观测种子雨和种子库的动态,并对不同地表覆盖物中种子萌发及幼苗数量进行观测和记录。结果表明,武夷山香果树种群种子雨持续时间近2个月,尤其是11月底至12月中旬为种子雨高峰期;随着海拔的上升,香果树种子总密度以及虫蛀种子密度均显著降低,但千粒重以及饱满种子密度则有所增加;香果树土壤种子库为瞬时种子库,其水平分布以母树南侧和西侧种子密度较大,母树北侧种子密度最小。香果树种子的垂直分布主要集中于枯落物和苔藓层;3月时香果树土壤种子库中存留的饱满种子仅占种子散布后1.80%,而1年实生苗存活率为6.18%,土壤种子库的损耗是其种群自然更新困难的主要原因;不同地表覆盖物对香果树幼苗的存活产生显著影响,枯落物及苔藓层的幼苗死亡率显著高于土壤表面。建议清理林内枯落物及苔藓,增加林内裸露土壤的面积,减小地上草本的盖度,以减少种子霉烂、虫蛀的几率,增加香果树实生苗胚根与土壤接触的几率以及改善光照条件,促进香果树自然更新。     

Spatial distribution and population dynamics of Striga hermonthica seeds in naturally infested farm soils

Densities and spatial distribution in soil of seeds of Striga hermonthica were analysed for four naturally infested farm fields in Western Kenya. A revised method for extraction of Striga seeds from soil was used, combining centrifugation with existing techniques based on flotation. Tests showed that 85% of Striga seeds were retrieved from soil samples. In all fields the majority of seeds were found in the plough layer (0 – 20 cm). New seeds entering the soil from the surface after seed shedding created a strong gradient with depth. Downward penetration from the soil surface was larger in sandy soil than in clay soil. In tilled soils no significant vertical density gradient was found within the plough layer. At a fine scale (0.2 m) seed densities showed little horizontal variation, but significant differences in seed densities in the horizontal plane were found at larger scale distances (several m) between locations in all fields. At 125 days after sowing the estimated average number of seeds produced per emerged Striga shoot was 4,827, excluding an approximately similar amount of seeds present in maturing capsules. The estimated average number of seeds produced per mature Striga seed capsule was 1188. Large seasonal fluctuations in the Striga seedbank were measured. An average net increase of 88,825 Striga seeds m^-2 (equivalent to 340%) was calculated from seedbank analyses in 16 sorghum plots. The level of Striga infestation in one field had decreased by 62% from 34,250 seeds m^-2 to 13,125 seeds m^-2 after keeping it fallow for a year. A sharp decline in Striga seed density was found in samples taken at increasing distances from highly infested fields, irrespective of wind direction or slope, suggesting very limited dispersal of Striga seeds by wind or water. Parasite emergence was non-linearly related to initial Striga seed densities in the soil, but this relationship was only observable at the scale of individual plant holes. Seed production was also non-linearly related to numbers of emerged parasites, when measured at plot scale (25 m²), but not at the scale of individual plant holes. In the fields we studied, seed densities below levels of 13,000 Striga seeds m^-2 could be considered to suppress the number of emerging parasites. However, if two or three emerged Striga plants per m^-2 were left to seed, enough seeds would be produced to keep the seedbank in balance.     

植冠与土壤种子库储存种子的萌发特性及策略

为明确黄土丘陵沟壑区植物种子库如何调控种子萌发来提高个体适合度,选择研究区7种具有种子库的主要物种为研究对象,以刚成熟和室内储存种子为对照,比较植冠宿存(5个宿存期)和土壤埋藏(5a埋藏期)对植物种子萌发特性的影响,探讨植冠种子库与土壤种子库储存下的种子萌发策略。结果表明:7种植物种子经过不同种子库储存后萌发特性表现出明显的种间差异,黄刺玫(Rosa xanthina)和水栒子(Cotoneaster multiflorus)种子萌发力表现为植冠宿存不变型、土壤储存增强型,土壤储存明显提高水栒子种子萌发速率;达乌里胡枝子(Lespedeza davurica)和狼牙刺(Sophora davidii)种子萌发力表现为植冠宿存增强型、土壤储存减弱型,种子萌发历时表现为植冠宿存延长型,土壤种子库储存还可加快达乌里胡枝子萌发速率、缩短萌发历时;茭蒿(Artemisia giralaii)和铁杆蒿(Artemisia gmelinii),种子萌发率随植冠宿存时间先升高后降低,随土壤储存时间先降低后升高,土壤储存可推迟其萌发,铁杆蒿种子萌发速率在植冠与土壤储存后均加快;紫丁香(Syringa oblata)种子萌发率随植冠宿存先升高后降低,土壤储存明显加快其种子启动萌发与速率。在黄土丘陵沟壑区,植物种子经过植冠或土壤种子库储存,或增加、加快、提早萌发充分利用有利条件提高占据性,或减少、减缓、推迟萌发分摊不利条件的风险;而且该区植物植冠与土壤储存后种子萌发特性间的关系,体现各自适应环境与应对干扰的分工与协作策略,主要表现为:单一主导型和相辅相成型。     

Long-term variation in seed mass and seed production in populations of Paris quadrifolia

Seed production of the perennial herb Paris quadrifolia L. (Liliaceae) was investigated in five populations in northern Poland. The long-term seed production per square metre differed significantly among populations and years. Moreover, throughout the 7-year study period, 30% of both whole ripe fruits and seeds alone were predated. Variation in seed mass per fruit in both space and time was significant. Throughout the 7-year study, nearly all the marked individuals produced fruits once every 2 years. The most frequent break between fruiting was 2 years and the longest was 5 years. Only the mean seed mass in fruits of the same individual varied significantly over subsequent years. In the five populations, the number of ovules, number of seeds in the fruit and seed mass varied significantly between populations. However seed/ovule ratio did not differ in fruits in the five populations. The seed mass/number trade-off in fruits was strongly partially correlated when the effect of total seed mass was considered. Breeding experiments suggest that P. quadrifolia has a substantial capacity for both inbreeding and outbreeding. There were no significant differences in the seed/ovule ratio, seed number or seed mass in fruits produced from bagged or control flowers. However, both seed/ovule ratio and number of seeds were significantly lower in fruits from emasculated flowers.     

Prediction of desiccation sensitivity in seeds of woody species: a probabilistic model based on two seed traits and 104 species

BACKGROUND AND AIMS: Seed desiccation sensitivity limits the ex situ conservation of up to 47 % of plant species, dependent on habitat. Whilst desirable, empirically determining desiccation tolerance levels in seeds of all species is unrealistic. A probabilistic model for the rapid identification of woody species at high risk of displaying seed desiccation sensitivity is presented. METHODS: The model was developed using binary logistic regression on seed trait data [seed mass, moisture content, seed coat ratio (SCR) and rainfall in the month of seed dispersal] for 104 species from 37 families from a semi-deciduous tropical forest in Panamá. KEY RESULTS: For the Panamanian species, only seed mass and SCR were significantly related to the response to desiccation, with the desiccation-sensitive seeds being large and having a relatively low SCR (i.e. thin 'seed' coats). Application of this model to a further 38 species, of known seed storage behaviour, from two additional continents and differing vegetation types (dryland Africa and temperate Europe) correctly predicted the response to desiccation in all cases, and resolved conflicting published data for two species (Acer pseudoplatanus and Azadirachta indica). CONCLUSIONS: This model may have application as a decision-making tool in the handling of species of unknown seed storage behaviour in species from three disparate habitats.     

Temporal and spatial patterns of seed dispersal in two Cistus species (Cistaceae)

Cistus species are obligate seeding, early colonizers that follow disturbance, particularly fire, in Mediterranean ecosystems. We studied seed release, seed dispersal and soil seed populations in stands of Cistus ladanifer and C. libanotis. Seed release started in mid- to late summer (C. ladanifer) or in early autumn (C libanotis), and continued for a very extended period: 8-10 months in C. ladanifer, and for a mean of 16 months in C. libanotis. The xerochastic capsules of both species released seeds by successive dehiscence of the locules. All capsules begin to dehisce simultaneously at the start of the seed release period, but in C. libanotis capsule fragmentation replaced dehiscence early in the seed release period. In plants of both species, seed shadows were characterized by a peak of density beneath the plant canopy and a very short tail of much lower densities, indicating that seeds are concentrated beneath mother plants when dispersed. Nevertheless, in late May, at the onset of the fire season, soil seed densities beneath plant canopies were low compared with densities expected from seed shadows, but were apparently high enough to allow recovery of the stands if a disturbance, such as fire, had taken place. Seed-eating Bruchidae in summer and granivorous ants during the seed release period were apparently the main causes of seed losses. Results suggest that in both Cistus species, the staggered seed release could constitute an efficient risk-reducing trait. The plant pool of seeds existing throughout most of the year could be a relevant component of Cistus seed banks.     

土壤种子库的分类系统和种子在土壤中的持久性

对国际上已经发表的10个土壤种子库分类系统的内容进行了总结和阐述,并对土壤种子库分类系统进行了评述,其中Thompson ＆ Grime在1979年提出的把土壤种子库分为短暂土壤种子库（Transient soil seed bank）和持久土壤种子库（Persistent seed bank）的二元分类系统以及Thompson等人提出的把土壤种子库分为（1）短暂土壤种子库,（2）短期持久土壤种子库（Short term persistent seed bank）,（3）长期土壤种子库（Long termp ersistent seed bank）的三元分类系统在生态学文献中已被广泛采用。在此分类的基础上产生了植物种子在土壤中的持久性（Persistence）概念,持久性是指植物的一种特性,是指植物的种子在土壤中能够存活超过1a的特性;植物种子的持久性被认为是一种对环境的进化适应,它可以在多个生长季节萌发从而分担环境震荡的风险,持久土壤种子库不仅在不稳定的环境里占有优势;即使在稳定的环境里,也被认为能够减少种内和种间的竞争;造成持久性的原因可分为环境因子和种子本身的特性比如休眠等两个方面,持久土壤种子库的出现使得土壤种子库的研究与进化生物学结合起来,使得土壤种子库的研究进入一个新的领域,更易激发人们的兴趣。关于种子的大小、形状及持久性的关系问题已经引起了相当的争论,基本上有4种格局：一是种子大小和形状与种子在土壤中的持久性有关,小而圆或扁的种子在土壤易存活持久;二是种子大小与种子在土壤中的持久性有关,小种子在土壤中易存活持久,但种子形状与持久性无关;三是种子大小、形状与种子在土壤中的持久性无关;四为较大的种子在土壤易存活持久,而种子形状与种子在土壤中的持久性无关。影响种子在土壤中的持久性因子比较复杂,总结过去的文献发现主要有以下几个因子：①种子的散布方式,②捕食,③植被的物种组成,④风,⑤土壤基质,⑥火,⑦干扰等。通过比较分析和研究,提出影响种子大小和在土壤中的持久性关系格局的关键因子是气候,特别是生态系统所在地的雨量;湿润气候下容易产生前两种格局,而干旱环境下的生境容易产生后两种格局。