Conservation ecology of endangered species Paphiopedilum armeniacum (Orchidaceae)

Paphiopedilum armeniacum is an endangered orchid species, endemic to China. During the period of April 2000 to October 2005, 66 observation sites were selected in Luoshapo of Nushan Mountains in Yunnan, China, to carry out the conservation ecological research on P. armeniacum. A total of 443 genets (1302 ramets in total) of P. armeniacum were sampled, their biological characteristics such as reproductive pattern, phenology, and life cycle were observed, and the ecological habits of the species such as the habitat and the structure of communities were studied. Experiments on ex-situ conservation were conducted, and the cloned ramets were replanted to their original habitat after ex-situ reproduction in Shenzhen, Guangdong, China. The relationships between P. armeniacum and climate, vegetation, other environmental factors in the original habitat, and the biological characteristics of asexual offsprings of P. armeniacum, which were replanted to the original habitat after ex-situ cultivation and reproduction, were investigated. The studies show that P. armeniacum in Luoshapo grows very well in secondary shrub boskets or in tussocks on limestone hills. It has both sexual and asexual reproduction. Asexual reproduction serves to complete the sexual reproduction and to extend the lifetime of genets, while it does not reduce sexual reproduction. There are two modes of asexual reproduction-by tillering or by producing rhizomes. The litter of shrub boskets or tussocks provides P. armeniacum with humus, and the rhizome reproduction of P. armeniacum is an adaptation to the litter-covered condition, i.e. to escape from the unfavorable environment. Blooming rate of ramets is 7.39% 1.02%, and fruit set rate from the blooming ramets is 32.23% 12.08%. P. armeniacum is able to invade the moderately destroyed forests and those in early restoring but is unable to grow in large dense forests. P. armeniacum also grows very well in artificial spare woods in Shenzhen and can reproduce many cloned ramets, which can normally bloom and yield fruits after being replanted to the original habitat. The results of this study show that P. armeniacum can be conserved by ex-situ conservation and by replanting the ex-situ reproduced ramets to original habitat. On the basis of the analysis of endangered mechanisms of P. armeniacum, it can be concluded that P. armeniacum has strong capability of both asexual and sexual reproductions, and an emergency mechanism consisted of massive production of rhizomes to cope with damage. Because highly effective pollinating insects that facilitate pollination in P. armeniacum are present in the habitat, flowering ramets produce fruits with large quantity of seeds, many of which in turn grow into new genets that can reproduce many cloned ramets. P. armeniacum makes very effective use of its environment and has distinct characteristics of enduring harsh environmental conditions; therefore, rather than its own inherent biological defects, the main threats facing this species are the destruction of its survival space and the wipe-out collecting of the plants as a result of trading. Based on the analysis mentioned above, certain appropriate strategies have been proposed for the conservation of P. armeniacum.     

Citrus replant problem in Iraq II. Possible role of allelopathy

The role of allelopathy in citrus replant problems was investigated in Iraq. The failure of citrus seedlings to grow normally in old citrus orchards was not caused by differences between old and non-citrus soils in electrical conductivity, pH, organic matter, soil texture and those minerals tested. Extracts of soil collected from old citrus orchards significantly reduced the growth of sour orange seedlings. Extracts and decaying sour orange roots reduced the growth of sour orange seedlings as did extracts of non-senescent sour orange leaves and decaying senescent leaves. Thus it appears that allelopathy is at least partly involved in the citrus replant problem.     

连栽土壤对杉木幼苗生长影响的研究

连栽土壤对杉木幼苗生长影响的研究马越强廖利平杨跃军汪思龙高洪陈楚莹（中国科学院沈阳应用生态研究所,１１００１５）刘更有（湖南省会同县林科所,４１８３０７）ＥｆｅｃｔｓｏｆＲｅｐｌａｎｔＳｏｉｌｏｎｔｈｅＧｒｏｗｔｈｏｆＣ．ｌａｎｃｅｏｌａｔａＳｅｄｌ...     

Relations between grapevine replant disease and root colonization of grapevine (Vitis sp.) by fluorescent pseudomonads and endomycorrhizal fungi

In pot experiments cuttings of grapevine rootstock cultivar 5C were grown on a soil from a grapevine nursery affected with replant disease (replant soil) and on a similar soil that had not been planted with grapevines before (non-replant soil). Plants were also inoculated with the vesicular-arbuscular (VA) mycorrhizal fungus,Glomus mosseae, or left without mycorrhizal fungus inoculation. Shoot and root growth, mycorrhization of roots and numbers of total aerobic bacteria and fluorescent pseudomonads on the rhizoplane of grapevines were determined at several sampling dates. On replant soil, numbers of fluorescent pseudomonads on the rhizoplane were higher compared to non-replant soil, before differences in shoot and root weight between replant and non-replant soil occurred. Without inoculation withG. mosseae, the mycorrhization of roots was much lower on replant soil (13%) than on non-replant soil (51%). On replant soil, inoculation withG. mosseae increased mycorrhization to 39% and increased shoot length, leaf area and shoot weight. The beneficial effect of VA-fungus inoculation on replant soil was not due to increased nutrient concentrations in leaves. On replant soil, the inoculation withG. mosseae reduced the number of fluorescent pseudomonads on rhizoplane of grapevine, while the numbers of total aerobic bacteria were not influenced by inoculation withG. mosseae. These results suggest a direct or indirect role of fluorescent pseudomonads in replant disease of grapevine.     

Evaluation of monoammonium phosphate and bacterial strains to increase tree growth and fruit yield in apple replant problem soil

The long-term effects of biological agents alone and in combination with monoammonium phosphate on tree growth and fruit production of apple trees planted on apple replant soil was studied for five years. Application of monoammonium phosphate (MAP) in the year of planting increased shoot growth, cross-sectional trunk area and fruit yield of McIntosh on M.26 rootstock for the first two years. The application of bacterial agents alone were not effective in increasing young tree growth except BACT-1 in 1987. None of the bacterial agents increased fruit yield when applied alone. The addition of certain bacterial agents to MAP application increased young tree growth in various years. The combination of bacterial agent B-10 and MAP reduced young tree growth and yield compared with the MAP treatment alone. These results suggest that the application of MAP alone may be sufficient to alleviate the replant problem and the addition of BACT-1, EBW-4 or B8 bacterial agents to this treatment may be beneficial to increase tree growth in some years. Contribution number 822. Contribution number 822.     

芽孢杆菌菌肥和菌剂对连作条件下桃幼树生长和土壤环境的影响

研究向桃树连作土壤中添加芽孢杆菌菌肥和菌剂对再植幼树生长、土壤养分、酶活性和真菌群落的影响,可为缓解桃树连作障碍提供理论依据.在盆栽条件下,以一年生普通桃'圆梦'和连作10年的桃园土壤为试材,设置8个处理,即连作土常规处理(RS)、客土常规处理(NS)、连作土常规处理基础上分别添加1％、4％、8％的芽孢杆菌菌肥(BF1...     

环渤海湾苹果产区老果园与连作果园土壤线虫群落特征

应用类群多样性、类群丰富度、个体密度和功能类群指数等群落参数,于2009年5-10月分3次对环渤海湾苹果栽植区老果园不同位置和连作果园取样研究了土壤线虫群落特征。结果表明:苹果连作对果园土壤生物环境具有明显的恶化作用,连作果园土壤环境条件恶劣;对功能类群指数的统计表明,苹果连作明显改变了果园土壤中植物寄生性线虫r-选择和k-选择的比例,与自由生活线虫比较,连作对植物寄生线虫影响更明显;连作提高了果园的土壤线虫PPI/MI,说明连作对果园土壤健康的扰动最大;土壤不同食性线虫数量统计结果显示,环渤海湾苹果栽植区植食性线虫数量未达线虫伤害阈值,线虫不是引起环渤海湾地区苹果连作障碍的主要原因。     

有机物料发酵流体和堆肥对苹果连作土壤环境及平邑甜茶幼苗生物量的影响

为探讨不同有机物料的发酵流体(厌氧发酵产物)和堆肥(有氧发酵产物)对苹果连作土壤环境的影响,以盆栽平邑甜茶幼苗为试验材料,分别设置猪粪+秸秆、鸡粪+秸秆、羊粪+秸秆、猪粪+鸡粪+羊粪+秸秆4个不同有机物料组合并进行厌氧发酵和有氧发酵,并将发酵产物分别施入连作土中,研究其对平邑甜茶幼苗生物量、连作土壤中微生物、土壤酶活性、土壤酚酸等的影响。结果表明:与有机物料堆肥相比,各有机物料发酵流体处理的平邑甜茶幼苗干重、鲜重较高,其中猪粪发酵流体处理显著提高了幼苗干、鲜重,7月份为对照的1.57、1.26倍,9月份为CK的1.55、1.86倍;两类发酵产物均增加了土壤微生物的数量,且发酵流体处理显著增加了土壤中细菌和放线菌的数量,其中羊粪发酵流体效果最明显,分别为CK的2.95倍和2.37倍,在堆肥处理中,真菌数量显著增高;两类发酵产物也影响了土壤中酚酸总量,表现为猪粪、鸡粪发酵流体和猪粪堆肥处理含量下降,至9月份分别下降到CK的0.45、0.39倍和0.36倍。     

Citrus replant problem in Iraq I. Possible role of soil fungi and nematodes

The role of soil fungi and nematodes in citrus replant problems was investigated. Several pathogenic and non-pathogenic fungi and the nematodeTylenchulus semipenetrans were isolated in about equal abundance from soils which displayed or did not display replant problems. However, in almost all trees showing evidence of decline, infection by the fungusPhytophthora citrophthora had advanced through the roots until it had reached the tree crown. Fumigation of old citrus soil with methyl bromide greatly increased the growth of sour organe. The application of Nemacure, Benomyl and Ridomil 5G confirmed the important role of pathogenic and non-pathogenic fungi and nematodes in the citrus replant problem. Inoculation of methyl bromide-treated soil with the pathogenic and non-pathogenic fungi separately or in combination further confirmed the previous experiments and also revealed an important role ofP. citrophthora andFusarium solani when replanting citrus in old citrus orchards.     

Long-term orchard groundcover management systems affect soil microbial communities and apple replant disease severity

Apple replant disease (ARD) is a soil-disease syndrome of complex etiology that affects apple tree roots in replanted orchards, resulting in stunted tree growth and reduced yields. To investigate whether different groundcover management systems (GMSs) influence subsequent ARD severity, we grew apple seedlings in an outdoor nursery in pots containing orchard soil from field plots where four GMSs had been maintained for 14 years in an orchard near Ithaca, NY, USA. The GMS treatments were: (1) pre-emergence herbicide (Pre-H), bare soil strips maintained by applying tank-mixed glyphosate, norflurazon and diuron herbicides annually; (2) post-emergence herbicide (Post-H), sparse weed cover maintained by applying glyphosate in May and July each year; (3) mowed sod grass (Mowed Sod); and (4) bark mulch (Mulch). Soils were also sampled from the grass drive lane maintained between the trees in the orchard (Grass Lane). Sampled soils (Orchard soil) were either pasteurized or left untreated, placed into 4-L pots, and planted with one apple seedling per pot. After 3 months of growth, soil (Bioassay soil) and apple tree roots (Bioassay roots) were sampled from each pot and microbial populations colonizing samples were characterized. Seedling growth was reduced in soils sampled from all four GMS treatments compared to the Grass Lane soils. Among the GMS treatments, seedling biomass was greater in Pre-H than in the Post-H soil. Soil microbial communities and nutrient availability differed among all four GMS treatments and the Grass Lane. Root-lesion (Pratylenchus sp.) nematode populations were higher in the Mowed Sod than in the other GMS treatments. Soil bacterial and fungal community composition was assessed in Orchard and Bioassay soils and Bioassay roots with a DNA fingerprinting method (T-RFLP). Redundancy analysis indicated that soils sampled from the different GMS treatments differentially influenced seedling biomass. A clone library of 267 soil bacteria was developed from sampled Orchard soils and Bioassay roots. These communities were dominated by Acidobacteria (25% of sequences), Actinobacteria (19%), δ-Proteobacteria (12%), β-Proteobacteria (10%), and these ratios differed among the GMS soils. Members of the family Comamonadaceae were detected only in tree-row soil, not in the Grass Lanes. The dominant sequences among 145 cloned fungi associated with apple seedling roots were Fusarium oxysporum (16% of sequences), an uncultured soil fungus submitted under DQ420986 (12%), and Rhodotorula mucilaginosa (9%). In a redundancy analysis, factors including fungal and oomycete community compositions, soil respiration rates, population sizes of culturable bacteria and fungi, soil organic matter content, and nutrient availability, were not significant predictors of apple seedling biomass in these soils. Different GMS treatments used by apple growers may influence subsequent ARD severity in replanted trees, but edaphic factors commonly associated with soil fertility may not reliably predict tree-root health and successful establishment of replanted orchards.