粘型小麦雄性不育系减数分裂特征及育性恢复研究

调查了粘型1B／1R和非1B／1R小麦雄性不育系,保持系及其F2的花粉母细胞减数分裂中期Ⅰ染色体联会情况、后期Ⅰ出现落后染色体的细胞频率以及末期Ⅱ含有微核的四分体的频率,结果表明：（1）粘果山羊细胞质对1B／1R型不育系减数分裂染色体配对水平具有特异性降低作用;（2）粘型1B／1R不育系减数分裂中期Ⅰ出现单价体细胞频率与后期Ⅰ出现落后染色体细胞的频率呈正相关,也与含微核的四分体频率呈正相关,而对应保持系则没有相关性;（3）粘果山羊草细胞质对非1B／1R不育系减数分裂过程影响不大,5个1B／1R不育系减数分裂过程中,3个时期染色体行为变异率的差异是特定的1B／1R核型与粘果山羊草细胞质互作的结果;（4）粘型1B／1R不育系杂交R2单株减数分裂3个时期染色体行为变异率与其恢复度成反比,这类不育系减数分裂中染色体行为不同步是其恢复不高且变异较大的一重要原因。     

喀斯特槽谷区土地石漠化与综合治理技术研发

深入揭示流域尺度水-土-生资源格局和研发因地制宜的水-土-生治理技术是"十三五"石漠化治理工程的主要瓶颈。国家重点研发计划——"喀斯特槽谷区土地石漠化过程及综合治理技术研发与示范"项目(2016YFC0502300)针对槽谷区特点,锁定两个关键科学问题和五个关键技术,从过程机理研究-技术研发-应用示范3个层面解剖区域水/土/生物资源分布格局与地质地貌之间的关系,阐明石漠化过程中的相关生态变化机理,因地制宜地研发水土资源高效利用、土壤地上/下流/漏失阻控与生态恢复技术;研发野生砧木及经济树种互作效应与优化配套技术,构建槽谷区可持续的生态系统和生态产业模式并示范推广,为区域生态改善和贫困问题解决提供科技支撑。     

Applied nucleation is a straightforward,cost‐effective forest restoration approach: reply to Ramírez‐Soto et al. (2018)

We agree with Ramírez‐Soto and colleagues that applied nucleation can be an effective approach for tropical forest restoration both in lowland and higher elevation tropical forests. We also contend that it is cheaper than standard plantation‐style plantings and is straightforward to train personnel to implement this approach.     

Reproductive challenges of a rare grass,Calamagrostis porteri subsp. insperata (Swallen) C. Greene: implications for habitat restoration

Background: Habitat management for reproductively challenged rare species is a problem when there is insufficient knowledge of their autecology. This study investigated reproductive failure in the rare grass Calamagrostis porteri ssp. insperata (Swallen) C. Greene (Reed bentgrass). Does the management recommendation of high light stimulate clonal growth, flowering, and seed production? Location: Shawnee National Forest, IL, USA, and in a greenhouse and an experimental garden at Southern Illinois University, Carbondale, IL, USA. Methods: Clones obtained from the three known Illinois populations were grown in a glasshouse under experimental light and soil moisture treatments. After 3 years, plants from the high light treatment were planted outside in an experimental garden where the light treatments were maintained for two more years. In the field, vegetative and flowering tiller density, canopy cover, and associated biotic and abiotic variables including abundance of co‐occurring plant species were monitored for 5 years. The overhead tree canopy was cleared over a portion of one population. Results: In the glasshouse, plants increased in size under high light and moist soil, and there were size differences among populations. Sixty‐six per cent (20 of 30) of the genets flowered when planted outdoors under full sunlight but did not produce seed. In the field, flowering only occurred in Calamagrostis growing in the cleared area, but no seed were produced. The plants in the flowering population were smaller than plants in the other two populations. The herbaceous community associated with Calamagrostis in the open diverged from the communities remaining under the shade. Conclusions: This study highlights the difficulty of managing reproductively challenged rare species. Calamagrostis populations can be managed to enhance clonal growth, but establishment of new populations would require translocation of vegetative material as it is highly unlikely that seed can be obtained.     

Can mobile sandy land be vegetated in the cold and dry Tibetan Plateau in China?

Desertification has taken place in the overgrazed grassland of the Tibetan Plateau,China,and the area of mobile sandy land has increased in recent decades.The challenging problem about desertification control is how to restore the vegetation of mobile sandy lands caused by severe desertification.Sand drifting is now regarded as the limiting factor of vegetation restoration in such lands.The initial phase of vegetation restoration is plant colonization,but it is often aborted due to sand drifting,and then vegetation restoration fails to proceed.For the sake of revegetation,the first step is to stop sand drifting to ensure plant colonization.In the northeastern Tibetan Plateau,China,feasible approaches have been found through long-term experiments,and the vegetation is being restored satisfactorily with these approaches in experimental sandy lands.The approaches comprise three types:enclosure,mechanical barriers and biological barriers.Different sandy lands require dissimilar combinations of these approaches.Enclosures may be adequate to revegetate inter-dunes or degraded grassland even in cold regions like the Tibetan Plateau,China,but it is deficient for revegetation of the shifting sand dunes unless mechanical and biological barriers are established simultaneously.     

Testing the Performance of Fourteen Native Tropical Tree Species in Two Abandoned Pastures of the Lacandon Rainforest Region of Chiapas,Mexico

The rainforest of Mexico has been degraded and severely fragmented, and urgently require restoration. However, the practice of restoration has been limited by the lack of species‐specific data on survival and growth responses to local environmental variation. This study explores the differential performance of 14 wet tropical early‐, mid‐ or late‐successional tree species that were grown in two abandoned pastures with contrasting land‐use histories. After 18 months, seedling survival and growth of at least 7 of the 14 tree species studied were significantly higher in the site with a much longer history of land use (site 2). Saplings of the three early‐successional species showed exceptional growth rates. However, differences in performance were noted in relation to the differential soil properties between the experimental sites. Mid‐successional species generally showed slow growth rates but high seedling survival, whereas late‐successional species exhibited poor seedling survival at both the study sites. Stepwise linear regressions revealed that the species integrated response index combining survivorship and growth measurements, was influenced mostly by differences in soil pH between the two abandoned pastures. Our results suggest that local environmental variation among abandoned pastures of contrasting land‐use histories influences sapling survival and growth. Furthermore, the similarity of responses among species with the same successional status allowed us to make some preliminary site and species‐specific silvicultural recommendations. Future field experiments should extend the number of species and the range of environmental conditions to identify site “generalists” or more narrowly adapted species, that we would call “sensitive.”     

The efficiency and effectiveness of different sea urchin removal methods for kelp forest restoration

Sea urchin overgrazing has caused widespread phase shifts from kelp forests to “urchin barrens” on many temperate reefs, reducing habitat complexity, productivity, and biodiversity. Sea urchin removal is increasingly used for kelp restoration; however, few studies have quantified the efficiency and effectiveness of different removal methods, resulting in limited understanding of their practicality. In this study, the efficiency (removal rate) and effectiveness (proportion removed) of four removal methods were evaluated in northeastern New Zealand. We compared culling or collecting sea urchins by either SCUBA or freediving in 128 small-scale plots (25 m²). We also evaluated the efficiency and effectiveness of culling in four large (1.6–2 ha) barren areas, scales relevant for restoration. On average, culling sea urchins was 1.9–4.4 times faster than collecting, and SCUBA was 1.5–3.3 times faster than freediving. Removal rates increased with sea urchin density, especially for culling on SCUBA, while freediving removal rates increased with experience. Effectiveness was lower in large-scale removals (86–93% of sea urchins ≥40 mm removed) compared to small-scale removals (98–99%), but sufficient for restoration objectives. Estimated time per area (using SCUBA culling) was similar across large-scale removals (49–57 hours/ha), despite an almost 2-fold variation in initial sea urchin densities (approximately 4–8 urchins/m²), suggesting area may better predict total removal time than simply number of sea urchins across low-density ranges. While sea urchin removal provides a rapid, feasible, and effective approach to restoring kelp in urchin barrens, restoration plans need to also address the causes of sea urchin overpopulation to ensure long-term benefits.     

Woody plant encroachment in granite barrens on the Frontenac Arch,eastern Ontario,Canada

Aims

Woody plant encroachment is a widespread phenomenon affecting treeless or sparsely treed habitats. We aimed to determine the extent and timing of tree and shrub encroachment into rock barrens of eastern Ontario over the last century, and to assess implications for their ongoing management.

Location

Queen's University Biological Station in the Frontenac Arch ecoregion.

Methods

We quantified the extent of change in woody vegetation in 290 rock barrens using aerial photography from 1925, 1965, and 2008. Composition and structure of woody plant communities in 10 barrens was subsequently quantified in the field using plot-based sampling. Cores or cross-sections were obtained from individuals >1.5 m height and dendrochronological techniques were used to determine their age and identify temporal patterns of any woody encroachment.

Results

Aerial photography indicated that the mean proportion of woody plant cover in barrens increased 22.5% from 1925 to 2008. Dendroecological analysis supported this. Few trees were present prior to 1900 and most established since 1960. Fraxinus americana, Juniperus virginiana, and Juniperus communis were the most common woody species colonizing the barrens. Remnants of large Pinus strobus stumps with extensive charring were found in 90% of the sampled barrens at a mean density of 22.6 stumps ha⁻¹.

Conclusions

Rock barrens on the Frontenac Arch have changed substantially over the past century; gradually being colonized by trees and shrubs and losing their distinctly open character. Active management — including prescribed fire and mechanical thinning — may be necessary if there is a desire to maintain these barrens and the rare species they support as components of the region's biodiversity. However, identification of a reference state for restoration is complicated by the fact that the structure and composition of these habitats were undoubtedly altered by European land clearance in the 19th century, and that some of these areas likely existed as pine woodlands before that.     

Environmental restoration effects of Ranunculus sceleratus L. in a eutrophic sewage system

This study investigated the environmental restoration effects of Ranunculus sceleratus in a sewage system microcosm trial, including the removal of pollutants and algal inhibition. We compared the removal of pollutants by R. sceleratus in a eutrophic sewage system in the presence and the absence of algae. The rate of removal without algae was 16.2–20.5% of that with algae. ${\text{NH}}_4^{+}–\text{N}$ was removed most readily by R. sceleratus. The effects of R. sceleratus on the growth of Microcystis aeruginosa were also investigated in two allelopathic modes. The level of algal inhibition after the addition of an extract of Ranunculus scleratus was 57.1–78.9% greater than that in a co-culture test. To understand the role of allelopathy interference with algal development, we also determined the total flavonoid contents of plants, which ranged from 3.57 g to 20.19 g per plant. The cell density of Microcystis aeruginosa was negatively correlated with the total flavonoids in R. sceleratus, although aquatic macrophytes may contain other allelochemicals involved with algal inhibition in addition to flavonoid compounds. The environmental effects of R. sceleratus were significantly correlated with its growth stage (or water retention time), plant height, and biomass. This study suggests that R. sceleratus has potential for the low-effort and sustainable management of freshwaters, particularly the removal of nutrient pollutants and the reduction of excessive algal growth, which may be attributable to allelochemicals such as flavonoids. The in situ environmental restoration effects of R. sceleratus require further investigation at the ecosystem level.     

科尔沁沙地不同地形小叶锦鸡儿灌丛土壤水分动态

根据科尔沁沙地广泛分布的小叶锦鸡儿灌丛的植被调查和土壤水分监测数据,分析了沙地人工固沙灌丛的土壤水分时空动态和土壤储水量变化,并应用水量平衡法测定了灌丛蒸散发.结果表明:丘间地的土壤水分条件最好,丘中次之,丘上最低;灌丛区的土壤水分含量随深度增加而增加,在生长季内不会发生水分胁迫.灌丛区土壤水分与降雨过程高度相关,深层(50～180 cm)土壤水分同降雨的相关性高于表层(0～50 cm)土壤,并且深层土壤水分的变异也大于表层.整个生长期内,小叶锦鸡儿灌丛土壤储水量增加,土壤水分处于积累中,估算蒸散量占同期降雨量的64%以上.