A set of simple decision matrices for prioritizing collection of rare plant species for ex situ conservation

Because it is virtually impossible to collect seed or tissue for ex situ conservation banks from every known population of rare plant species, it is important to rank populations systematically in terms of their priority for collection. The New England Wild Flower Society, which maintains a regional seed bank, developed a set of three complementary decision matrices in spreadsheet form by which to prioritize all occurrences of all state-listed rare plant species in New England in terms of their urgency and feasibility for collection. Data on 4333 occurrences, spanning 456 taxa, were collated from six state Natural Heritage Programs. The first decision matrix ranked taxa in terms of their amenability to storage or propagation at ex situ institutions, and determined whether any known New England occurrences were reproductive. The second matrix further ranked taxa in terms of their global and regional rarity and the viability and genetic and geographic representation of collections already present in the bank. The third matrix scored individual occurrences within each taxon in terms of the presence of imminent threat, reproductive status, vigor, protection status, potential genetic distance from other occurrences, availability of landowner permission, and their current status in the bank. Occurrences were then sorted in ascending order by total matrix score; those with low scores were at the top of the list for collection priority. 3743 occurrences were deemed eligible for collection. Scores ranged from 14.5 to 182, and were influenced most strongly by the number of occurrences per taxon. Clear breakpoints were apparent in the distribution of scores, with clusters of uncommon taxa at the low end of the scale and a long tail created by taxa with more numerous occurrences in New England. These breakpoints could potentially be used to prioritize groups of occurrences that should receive the first attention for collection, while postponing collection of higher-scoring groups. Fewer than 1% of occurrences were misclassified, according to post hoc inspection. This simple set of decision matrices can be adapted by a wide range of institutions involved in ex situ conservation.     

陕北安塞退耕地持久土壤种子库与地上植被的对应关系

通过研究陕北安塞退耕3~31 a的阴阳坡10个样地的持久土壤种子库特征及其与地上植被的关系,分析持久土壤种子库在植被恢复中的作用。结果表明：调查样地持久土壤种子库由15个科36个物种组成,种子密度在1 908~12 617粒/m2之间,1年生物种占80%,随着退耕演替的进行,种子库中1年生物种比例呈下降趋势,多年生物种比例呈上升趋势,地带性物种在持久种子库中的比例也随退耕时间的延长而增加,物种数和种子库密度均随退耕演替先增大后降低;持久土壤种子库与地上植被的相似性较低,Serensen相似性系数为0.21~0.42;通过对适宜物种的确限度及土壤种子库大小的分析,认为该区退耕地的持久土壤种子库具有一定的植被恢复潜力。     

Relation between soil microbial activity and the effect of seed inoculation with the rhizopseudomonad strain 7NSK2 on plant growth

Summary The relationship between the microbial activity in the soil and the effect of seed inoculation with the rhizopseudomonad strain 7NSK2 was evaluated in a series of pot experiments under greenhouse conditions. The microbial activity in plain soil, as measured by the respiratory activity, was significantly increased by the growth of the plants. Both the respiration rate of the microorganisms and the density of the bacteria and fungi in the bulk soil increased with increasing duration of the plant growth. Upon repeated short-term growth of plants on the same soil, a similar stimulation was noticed.The effect of seed inoculation on the growth of the maize cultivar Beaupré and the barley cultivar Iban was most pronounced in the microbiologically more active soils. The results suggest that the increase of the plant growth by seed inoculation is probably due to the inhibition of deleterious root microorganisms.     

Host status of 10 fungal isolates for two nematode species, Filenchus misellus and Aphelenchus avenae

The classification of nematodes in the family Tylenchidae into plant parasites, plant associates or fungal-feeders for community analyses, have been much discussed by nematode ecologists. For an appropriate classification, fungal-feeding habits in the family need to be studied. To evaluate the host status of 10 fungal isolates for Filenchus misellus (Tylenchidae) and Aphelenchus avenae (Aphelenchida, Aphelenchidae), population growth rates, body length and width and sex ratios of the nematodes were measured after 40-day culture on fungal colonies at 25 °C. For F. misellus, the fungi determined as good hosts were two Basidiomycota fungi (Agaricus bisporus, Coprinus cinereus), three Ascomycota fungi (Chaetomium cochlioides, Chaetomium funicola, Chaetomium globosum) and a plant-pathogenic fungus (Rhizoctonia solani) on the basis of nematode population growth rate and female body length. Interestingly Pleurotus ostreatus, known as a predaceous fungus for the other nematodes, was also a good host for F. misellus. While, for A. avenae, good hosts were four plant-pathogenic fungi (Fusarium oxysporum f. sp. conglutinans, F. oxysporum f. sp. cucumerinum, Pythium ultimum, R. solani) and A. bisporus. A. avenae was trapped and preyed upon by Pleurotus hyphae. In F. misellus, males were 7-21% of adults, but the ratio did not correlate significantly with the population growth rate. In A. avenae, no male occurred. Differences in habitat preference between Filenchus and Aphelenchus were explained on the basis of the host status and habitat preferences of the tested fungi.     

Natural N abundance of plant and soil inorganic-N as evidence for over-fertilization with compost

To test the hypothesis that N isotope composition can be used as evidence of excessive compost application, we measured variation in patterns of N concentrations and corresponding δ¹⁵N values of plants and soil after compost application. To do so, a pot experiment with Chinese cabbage (Brassica campestris L. cv. Maeryok) was conducted for 42 days. Compost was applied at rates of 0 (SC0), 500 (SC1), 1000 (SC2), and 1500 mg N kg⁻¹ soil (SC3). Plant-N uptake linearly increased with compost application (r² = 0.956, P < 0.05) with an uptake efficiency of 76 g N kg⁻¹ of compost-N at 42 days after application, while dry-mass accumulation did not show such linear increases. Net N mineralized from compost-N increased linearly (r² = 0.998, P < 0.01) with a slope of 122 g N kg⁻¹ of compost-N. Plant-δ¹⁵N increased curvilinearly with increasing compost application, but this increase was insignificant between SC2 and SC3 treatments. The δ¹⁵N of soil inorganic-N (particularly NO₃⁻-N) increased with compost application. We found that plant-δ¹⁵N reflected the N isotope signal of soil NO₃⁻-N at each measurement during plant growth, and that δ¹⁵N of inner leaves and soil NO₃⁻-N was similar when initial NO₃⁻ in the compost was abundant. Therefore, we concluded that δ¹⁵N of whole plant (more obviously in newer plant parts) and soil NO₃⁻-N could reveal whether compost application was excessive, suggesting a possible use of δ¹⁵N in plants and soil as evidence of excess compost application.     

Morphological characterization of seeds of three Australian wild Citrus species (Rutaceae): Citrus australasica F. Muell., C. inodora F.M. Bailey and C. garrawayi F.M. Bailey

The comparative morphology of the seeds of three Australian Citrus species, C. australasica C. inodora and C. garrawayi, was studied. Their seed characteristics were broadly similar to those of the cultivated species of the genus, when observed under light and scanning electron microscopy. Citrus garrawayi differed in seed shape (rounded to triangular) and seed coat morphology (i.e., thicker with longer epidermal protrusions) from C. australasica and C. inodora (rounded surface with flat underside in shape). The well-developed minute epidermal protrusions on the seed coat of C. garrawayi were more similar to those in the cultivated species, C. × sinensis and C. × aurantium. In contrast, the surface topography of C. australasica and C. inodora seeds was more like that of the cultivated species, C. × aurantifolia and C. × limon. Seed morphology, especially surface topography, was found to be a useful tool for taxonomic identification in Australian wild citrus.     

Hay strewing, brush harvesting of seed and soil disturbance as tools for the enhancement of botanical diversity in grasslands

Since the middle of the last century agricultural intensification within Europe has led to a drastic decline in the extent of botanically diverse grasslands. Whilst measures to enhance the diversity of agriculturally-improved grasslands are in place, success has often been limited. One of the primary factors limiting success is the paucity of sources of propagules of desirable species in the surrounding landscape. The restoration of two contrasting grassland types (lowland hay meadow and chalk grassland) was examined using a replicated block experiment to assess the effectiveness of two methods of seed application (hay strewing and brush harvesting) and two methods of pre-treatment disturbance (power harrowing and turf stripping). The resulting changes in botanical composition were monitored for 4 years. Seed addition by both methods resulted in significant temporal trends in plant species composition and increases in plant species richness, which were further enhanced by disturbance. Power harrowing increased the effectiveness of the seed addition treatments at the lowland hay meadow site. At the chalk grassland site a more severe disturbance created by turf stripping was used and shown to be preferable. Whilst both hay strewing and brush harvesting increased plant species richness, hay strewing was more effective at creating a sward similar to that of the donor site. Soil disturbance and seed application rate at the recipient site and timing of the hay cut at the donor site are all factors to be considered prior to the commencement of restoration management.     

刺萼龙葵土壤种子库特征及其对替代控制的响应

土壤种子库在退化生态系统植被的恢复和演替中起重要作用,为明确外来入侵植物刺萼龙葵（Solanum rostratum Dunal.）土壤种子库特征,评价植物替代控制刺萼龙葵的效果,调查了河滩及农田边缘两个典型生境中的刺萼龙葵土壤种子库特征,分析了刺萼龙葵种子在土壤中的垂直分布与季节变化动态,并利用多种多年生禾本科与豆科牧草对刺萼龙葵进行替代控制研究,以期为刺萼龙葵生态调控提供理论依据。结果表明：1）两个生境中共鉴定出23种植物,禾本科和菊科为优势科;河滩及农田边缘刺萼龙葵种子总储量分别达347粒·m^-2和2 600粒·m^-2,占整个种子库的2.46%及35.16%。2）河滩生境中刺萼龙葵种子多集中于表层（0~2 cm）土壤,占种子总量的64.3%,且随土层深度的增加而减少;而农田边缘生境0~2 cm、2~5 cm和5~10 cm 3层种子数量差异不大（P>0.05）,分别占种子总量的32.7%、38.2%及29.1%。3）两个生境中刺萼龙葵种子主要集中于4月份采集的土样中,分别为273粒·m^-2（河滩）和1 970粒·m^-2（农田边缘）,显著高于6月份与8月份采集的土样种子数（P<0.05）;4）从替代控制第2年起,刺萼龙葵的密度、生物量及土壤种子储量即被控制在较低水平,均显著低于同期对照（P<0.05）,沙打旺+苇状羊茅+冰草+羊草组合对刺萼龙葵控制效果最佳,同时还可获得牧草鲜重20 396.1 kg·hm^-2,干重7 710.6 kg·hm^-2（2017年）,经济效益可观。5）刺萼龙葵种子库与刺萼龙葵密度（P<0.01）、生物量（P<0.05）呈正相关,牧草产量与刺萼龙葵种子库储量、密度、生物量均呈负相关,但相关性不显著（P>0.05）;降雨显著影响刺萼龙葵种子库储量（P<0.05）,可用幂函数模型y=2.619x^0.001（R²=0.822,F=18.486,P=0.013）描述二者之间的关系。     

Large-scale changes in the abundance of common higher plant species across Britain between 1978, 1990 and 1998 as a consequence of human activity: Tests of hypothesised changes in trait representation

Presence of higher plant species was recorded in 1455 permanently marked quadrats located across Britain in 1978, 1990 and 1998 in a stratified, random sample of 259 1 km squares. Significant increases and decreases in frequency of each species were summarised as changes in the representation of simple traits, each of which had an established relationship with varying levels of fertility or disturbance. By testing the null hypothesis that the trait values represented among increasing or decreasing species were a random draw from the 1978 species pool, we determined the consistency of botanical change with changes in land-use in different vegetation types and landscape locations across Britain.Overall, 63% of significant changes in species occupancy were decreases and 37% increases. Trait changes were largely consistent with the impact of increased nutrient availability across vegetation types associated with inherently low fertility, such as infertile grassland, heath, bog and moorland. Linear habitats in lowland Britain saw trait changes consistent with secondary succession. Although trait changes were highly consistent with eutrophication in upland vegetation, the identity of the changing species left open the possibility that increased N deposition, sheep grazing intensity and local improvement could all have played a part.Recent changes in common plant species across Britain suggest that objectives for large-scale restoration and maintenance of plant communities must address four problems: (a) the increasing scarcity of stress-tolerant species in lowland species pools, (b) exploitation and maintenance of species populations on habitat fragments and linear features in the lowlands, (c) the spread and persistence of generalist species in upland Britain, (d) systemic nutrient enrichment in both lowland and upland environments.