林地覆盖对雷竹林土壤碳氮磷化学计量特征的影响

林地覆盖措施可明显促进雷竹笋芽提早萌发,显著提高竹林经济效益,但长期连年覆盖会导致雷竹林退化为雷竹林。对不同覆盖年限(1、3、6 a)雷竹林和不覆盖雷竹林土壤C、N、P含量和化学计量比及相关性进行了研究。结果表明:不同覆盖年限雷竹林和不覆盖雷竹林土壤C、N、P含量均随土壤深度的增加而极显著降低。不同土层土壤C、N、P含量不同覆盖年限雷竹林极显著地高于不覆盖雷竹林。随覆盖年限的延长,雷竹林0～20 cm土壤C、N含量极显著提高。覆盖1 、3 a雷竹林和不覆盖雷竹林0～50 cm土壤P含量和20～50 cm土壤C、N含量差异均不显著,均显著地低于覆盖6 a雷竹林土壤。不同覆盖年限雷竹林各土层土壤C:N差异不显著,而C:P、N:P随覆盖年限的延长呈升高趋势。随覆盖年限的延长,土壤C、N、P间正相关关系减弱,C与N、P协同变化速率降低。研究表明:雷竹鞭根系统主要分布区0～20 cm土壤养分过量积累及引起的土壤养分失衡是林地覆盖雷竹林退化的主要原因。应实行轮闲覆盖和测土配方平衡施肥,并在雷竹自然出笋开始时(3月上旬)及时撤除有机覆盖物。为雷竹林可持续经营提供理论依据。     

林地覆盖经营雷竹林叶片养分特征及其与土壤养分的关系

探讨了短期覆盖经营(覆盖1 a)、休养式覆盖经营(覆盖3 a 后休养3 a)、长期覆盖经营(覆盖6 a)和不覆盖雷竹林(CK)2年生立竹叶片养分含量、化学计量比和再吸收率及其与土壤养分的关系。结果表明：(1)短期和休养式覆盖经营促使雷竹叶片养分含量和再吸收率总体上提高,而长期覆盖经营对雷竹叶片 P 含量和N、K 再吸收率会产生较为明显的影响,叶片 P 含量、N 再吸收率显著升高,K 再吸收率降低;(2)短期和休养式覆盖经营对雷竹林土壤、叶片养分化学计量比影响不明显,但长期覆盖经营使雷竹林土壤、叶片 N∶P、K∶P 显著降低;(3)短期覆盖经营能增强雷竹林土壤养分与叶片的养分含量、化学计量比和养分再吸收率的相关性,但随覆盖经营年限的延长,相关性总体上呈减弱趋势;(4)土壤养分含量及其平衡关系对林地覆盖经营雷竹林叶片养分特征影响明显;(5)长期覆盖经营雷竹林土壤、叶片养分间相关性明显减弱,竹子吸收利用养分的能力下降,生产中应实行雷竹林休养式覆盖经营方式。研究结果为林地覆盖经营雷竹林的可持续发展提供了理论参考。     

地表覆盖栽培对雷竹林凋落物养分及其化学计量特征的影响

为了解不同覆盖栽培年限雷竹林凋落物养分及其化学计量特征,分析了换叶期雷竹林凋落物的凋落量,C、N、P、K养分含量,养分季节归还量以及养分元素生态化学计量比值在不同覆盖年限之间的差异。结果表明:(1)雷竹林在连续覆盖3a后,叶凋落量极显著性提高(P＜0.01),在总凋落量中比例增加,但枝凋落量变化不明显。(2)连续3a覆盖对雷竹林凋落物中的养分含量影响极显著(P＜0.01),C、N养分含量极显著降低,P含量极显著升高,而K养分含量在覆盖2a时就出现了显著增加的变化响应;林地凋落物的养分归还量同时还受凋落量的影响,其伴随覆盖年限增长的变化趋势与养分含量并不一致。(3)覆盖2a内的雷竹林地凋落物表现出稳定的高N∶P以及低P含量,表明凋落物分解速率较低;连续覆盖3a的林地凋落物P含量极显著升高,N∶P极显著下降(P＜0.01),表明此时凋落物分解速率加快。(4)线性回归分析表明,凋落物中K元素随覆盖年限增长而消耗的规律与N、P元素无显著相关关系。     

雷竹林土壤和叶片N、P化学计量特征对林地覆盖的响应

为摸清林地覆盖集约经营对雷竹林土壤和叶片氮(Nitrogen,N)、磷(Phosphorus,P)化学计量特征的影响,揭示雷竹林退化机理,为退化雷竹林恢复提供理论依据,对不同林地覆盖年限(CK,3 a和6 a)雷竹林土壤和立竹叶片的N、P含量和N∶P变化规律进行了分析。结果表明:不同林地覆盖年限雷竹林土壤N、P含量均随土层深度的增大而降低,随着林地覆盖年限的增加,各土层土壤N、P含量均提高。林地覆盖雷竹林0—20 cm土层土壤N、P累积现象明显,N∶P显著提高;林地覆盖雷竹林不同年龄立竹叶片N、P含量均较不覆盖雷竹林有显著或极显著降低,叶片N∶P随林地覆盖年限的增加总体上呈显著升高趋势;立竹叶片N∶P与土壤P含量极显著正相关,与立竹叶片P含量和土壤N∶P极显著负相关,而与土壤和立竹叶片N含量相关性不显著。随林地覆盖年限的增加,雷竹林土壤和立竹叶片N、P间相关性均减弱;研究表明林地覆盖会明显改变雷竹林土壤和立竹叶片的N、P化学计量特征,引起N、P养分失衡,P素对雷竹林生长的限制性作用增强,会导致雷竹林退化。     

林地覆盖经营对雷竹叶片非结构性碳水化合物与氮、磷关系的影响

为揭示雷竹生理生态对林地覆盖经营的响应与适应机制,测定了不同覆盖经营年限(CK、1、3和6年)雷竹林1~3年生立竹叶片可溶性糖、淀粉、氮(N)和磷(P)含量,分析了覆盖经营对雷竹林叶片非结构性碳水化合物(NSC)与N、P含量及其化学计量关系的影响.结果表明： 覆盖经营1年雷竹林叶片NSC及可溶性糖含量较CK显著升高,N/P显著降低,N限制作用增强;覆盖经营3年雷竹林叶片可溶性糖含量较CK显著降低,淀粉含量显著升高,而NSC含量变化不明显,单位质量N、P的NSC含量最高;覆盖经营6年雷竹林叶片NSC、可溶性糖含量较CK显著降低,淀粉含量和N/P显著升高,P限制作用增强.短期覆盖(≤3年)经营雷竹林叶片NSC含量与N、P含量呈显著正相关,与N/P呈显著负相关;长期覆盖(6年)经营雷竹林叶片淀粉含量与N、P含量呈显著负相关,与N/P呈显著正相关.研究表明,短期覆盖(≤3年)经营雷竹林叶片N/P的降低可促使叶片淀粉分解和可溶性糖积累,明显增强雷竹生长活性,而长期覆盖(6年)经营雷竹林叶片N/P升高则促进叶片淀粉积累,雷竹生长由N限制转变为P限制,立竹生长活性明显降低,引起雷竹林退化.因此建议雷竹林连续覆盖经营不宜超过3年.      

林地覆盖经营对雷竹鞭根主要养分内循环的影响

为了给林地覆盖经营雷竹(Phyllostachys violascens)林可持续经营提供理论参考,探讨了休养式覆盖经营(覆盖3a后休养3a)、长期覆盖经营(覆盖6a)和不覆盖雷竹林(CK)2年生壮龄竹鞭及其1级、2级根N、P、K、Mg、Ca、Fe浓度和养分迁移、内循环率的差异。结果表明:不同覆盖经营年限雷竹林N、P、K、Mg、Ca和Fe浓度总体上1级根显著高于2级根。1级根和2级根中均存在N、P、K、Mg的养分内循环,且1级根养分内循环率大于2级根,Fe、Ca内循环不明显。N、P、K、Mg养分浓度与养分迁移速率随时间的推延,1级根为持续降低,2级根为先升高后降低。与不覆盖雷竹林相比,休养式林地覆盖经营总体上提高了1级、2级根的N、P、K、Ca的浓度和P、K、Mg的迁移速率、N、P、K的迁移量、P、K的养分内循环率以及1级根Mg的浓度和迁移量、2级根N的迁移速率和Mg的内循环率;长期林地覆盖经营虽提高了雷竹1级根N、K的浓度和N的迁移量及2级根N的浓度和内循环率,但总体上降低了1级根P、K、Mg和2级根N、P、Mg的迁移量与1级、2级根P、Mg的迁移速率及P、K、Mg的养分内循环率。研究表明:雷竹林鞭根中存在明显的养分内循环,且1级根对养分内循环的贡献较大。休养式林地覆盖经营利于雷竹林对养分的循环利用,而长期覆盖经营阻碍了根系对养分的平衡吸收,减弱了根系养分的内循环,不利于雷竹林的生长更新。     

西南喀斯特石漠化环境适生植物构树细根、根际土壤化学计量特征

为了解西南喀斯特石漠化适生植物构树(Broussonetia papyrifera)对贫瘠土壤养分环境的适应策略, 及其细根、根际土壤的化学计量特征对石漠化等级的响应, 该研究以西南喀斯特石漠化环境适生植物构树为研究对象, 运用生态化学计量学方法, 开展不同等级石漠化环境构树细根、根际土壤有机碳(C)、全氮(N)、全磷(P)、全钾(K)、全钙(Ca)及全镁(Mg)养分含量特征及C、N、P化学计量特征研究。结果表明, 除Ca含量外, 喀斯特石漠化环境适生植物构树细根、根际土壤的养分含量均处于较低水平; 细根N:P为12.59, 表明构树生长受N和P共同限制; 随着石漠化等级的增加, 细根C、N含量和C:N、C:P呈先降后升的变化趋势, K、P含量是则表现为先升后降, Ca、Mg含量和N:P无明显变化规律; 不同等级石漠化环境中的构树根际土壤N、P、K、Ca含量呈不同的变化趋势, 而C、Mg含量及C、N、P化学计量特征的变化较不显著; 细根与根际土壤的化学计量特征之间存在显著的相关性, 二者的C、P、Ca、Mg含量、C:N、C:P分别对应呈显著正相关关系, 而N含量呈极显著负相关关系; 细根的K含量则较为稳定, 几乎不受根际土壤养分的影响。     

林地覆盖经营对雷竹叶片营养质量及食叶害虫适口性的影响

为揭示冬季地表有机材料覆盖促进竹笋早出的林地覆盖经营措施对雷竹叶片营养质量的影响,并基于叶片的食叶害虫适口性分析林地覆盖经营对雷竹林食叶害虫发生与成灾的影响,探讨了休养式覆盖经营(覆盖3年休养3年)、长期覆盖经营(连续覆盖6年)和不覆盖雷竹林(CK)1~3年生立竹叶片C、N、P、可溶性糖、蔗糖、淀粉、纤维素、木质素、单宁、草酸和酚酸等含量的差异。结果表明:与不覆盖雷竹林相比,休养式林地覆盖经营雷竹林1~3年生立竹叶片C含量变化不明显,淀粉、纤维素、酚酸含量均显著降低。除上述指标外2、3年生立竹叶片其他指标均显著升高,1年生立竹叶片木质素、草酸含量显著升高;长期覆盖经营雷竹林1、2年生立竹叶片酚酸含量无显著变化,P、草酸、木质素含量显著升高,其他指标均显著降低;3年生立竹叶片P、蔗糖、木质素、草酸、酚酸含量显著升高,其他指标均显著降低;长期林地覆盖经营对雷竹叶片C、N、P养分平衡也产生了明显影响。林地覆盖经营对雷竹叶片的营养质量和食叶害虫适口性产生了较为明显的影响,其中,休养式覆盖经营雷竹林叶片营养质量和防御物质含量提高,叶片的食叶害虫适口性降低,抵御食叶害虫为害能力增强,而长期覆盖经营雷竹林相反,可能更易诱发食叶害虫的发生与成灾。     

3种功能型林木幼苗叶片与细根碳氮磷化学计量特征及其异速关系

为了比较不同功能型林木叶片与细根碳氮磷化学计量特征及其异速关系的差异,本研究以刨花楠(常绿阔叶)、福建山樱花(落叶阔叶)和福建柏(常绿针叶)的幼苗为对象,对其叶片和细根的碳(C)、氮(N)、磷(P)含量及其计量比关系进行分析。结果表明: 3种树木幼苗的叶片与细根的C、N、P含量及其计量比存在显著差异,其中,叶片与细根的C含量及C/N、C/P均以刨花楠最高,N含量和N/P以福建山樱花最高,P含量以福建柏最高;3种幼苗叶片的C、N、P含量和C/P、N/P均高于细根。叶片的C、N、P含量及其计量比之间的异速关系与细根不同,且受功能型差异的影响;3种幼苗叶片的C/P与N/P之间存在着指数明显不同的异速关系,但其细根的N、P含量均为等速关系。3种幼苗叶片和细根的C、N、P含量及其计量比关系也存在差异;刨花楠叶片和细根的关系主要显示为叶片C含量与细根P含量的异速关系,福建山樱花则主要显示在叶片C、N含量及C/N、N/P与细根C/N、N/P间的异速或等速关系,而福建柏主要是叶片C含量与细根C、N、P含量间的异速关系,福建山樱花叶片与细根的养分分配更具协调性。3种幼苗叶片和细根对P的投资策略具有相似性。研究结果为实施林木苗期精准养分管理与高效培育技术等提供了科学依据。     

长白山北坡不同林分类型细根-土壤C、N、P化学计量特征

细根是植物吸收养分和水分的主要器官,也是土壤养分归还的重要途径。研究细根的化学计量特征对了解森林生态系统植物-土壤养分循环具有重要意义。以吉林省八家子林业局蒙古栎天然林、天然阔叶混交林和落叶松人工林中龄林为对象,基于15块30 m×30 m样地的林分调查数据以及细根和土壤样品的测定数据,研究了不同林分类型细根和土壤的C、N、P化学计量特征以及两者的关系。结果表明：不同林分的细根和土壤C、N、P化学计量特征差异显著(P<0.05)。3种林分类型细根均受N限制,天然阔叶混交林土壤养分丰富,但蒙古栎天然林土壤P较贫乏。落叶松人工林和天然阔叶混交林的细根化学计量特征与土壤化学计量特征的相关程度明显高于蒙古栎天然林。3种林分的细根C∶N、C∶P和C含量受土壤化学计量特征影响较大。土壤C∶P是影响3种林分细根化学计量特征的最主要因素。研究结果可为长白山林区蒙古栎天然林、天然阔叶混交林和落叶松人工林的土壤养分管理和森林可持续经营提供一定的理论依据。     

Further studies of the sieve-element plastids of theCaryophyllales includingBarbeuia,Corrigiola, Lyallia,Microtea, Sarcobatus,andTelephium

The sieve-element plastids of 69 species of theCaryophyllales were investigated by transmission electron microscopy. All contained the specific subtype-P3 plastids characterized by a peripheral ring of protein filaments. The presence or absence of an additional central protein crystal and their shape being either polygonal or globular as well as the average sizes of the sieve-element plastids are useful features in the characterization of some families.—Barbeuia contains sieve-element plastids that confirm its placement within thePhytolaccaceae. Lyallia differs fromHectorella by including small starch grains in their sieve-element plastids, which otherwise by their globular crystals negate a closer connection to theCaryophyllaceae. The lack of a central protein crystal in its form-P3fs plastids placesMicrotea best within theChenopodiaceae. Sarcobatus, a so far uncontested member of theChenopodiaceae, contains form-P3cf plastids, i.e., including a central crystal not found elsewhere in this family.Telephium andCorrigiola, shifted back and forth betweenMolluginaceae andCaryophyllaceae, have form-P3cf(s) plastids with a polygonal crystal which favor their placement within theCaryophyllaceae.     

Synopsis of the tribe Bocageeae (Annonaceae), with revisions of Cardiopetalum,Froesiodendron, Trigynaea,Bocagea, and Hornschuchia

The tribal name Bocageeae Endlicher is reestablished and the tribe is circumscribed on the basis of solitary internodal ebracteate pedicels that are articulated at the base, and pollen shed in polyads of eight or more grains. Septate anther locules, large pollen size, and seed appendages are prevalent in the tribe. Intectate pollen with free-standing columellae, rare in Annonaceae, occurs not only in the genusTrigynaea but also in some species ofBocagea andHornschuchia. As defined here, the Bocageeae include seven neotropical genera:Cymbopetalum, Porcelia, Bocagea, Cardiopetalum, Froesiodendron, Hornschuchia, andTrigynaea. The latter five genera are revised and the treatments include ten new species:Cardiopetalum plicatum, Froesiodendron urceocalyx, Hornschuchia lianarum, H. santosii, H. leptandra, Trigynaea cinnamomea, T. lanceipetala, T. triplinervis, T. lagaropoda, andT. axilliflora, all from tropical South America. A new combination,Froesiodendron longicuspe, changes the rank of that taxon from subspecies to species.Cardiopetalum surinamense is removed fromFroesiodendron and reassigned toCardiopetalum on the basis of its connate petals, dehiscent monocarps, and seeds with bilobed arils. A cladogram provides an explicit hypothesis of intergeneric relationships in the tribe. The new combinationOnychopetalum periquino, based onTrigynaea periquino, is made.     

A reconsideration of the genusRabdosiella (Lamiaceae,Nepetoideae, Ocimeae)

The two generaPlectranthus andIsodon are compared and found to be very dissimilar.Isodon ist considered to be misplaced inOcimeae subtribePlectranthinae and apparently is more closely related to subtribeHyptidinae. The disjunct genusRabdosiella is compared to these two genera and regarded to be polyphyletic. The AfricanR. calycina (Benth.)Codd is returned toPlectranthus and calledP. calycinus Benth., while the AsianR. ternifolia (D. Don)Codd is placed inIsodon sect.Pyramidium and calledI. ternifolius (D. Don)Kudo.     

Antibiotic Susceptibility as a Taxonomic Characteristic of Proteobacteria of the Genera Alteromonas, Pseudoalteromonas, Marinomonas, and Marinobacter

Type strains of bacteria of the genera Alteromonas, Pseudoalteromonas, Marinomonas, and Marinobacterand symbiotrophic bacteria isolated from the Far Eastern bivalve mollusks Crenomytilus grayanusand Mizuhopecten yessoensisand identified as Pseudoalteromonas nigrifaciensand P. citreawere tested for susceptibility to antibiotics. Of the ten antibiotics used in this study, benzylpenicillin, polymyxin, lincomycin, and oleandomycin were valuable for the polyphasic taxonomy of marine aerobic proteobacteria. Marine bacteria of the genera studied exhibited characteristic antibiotic susceptibility profiles, which were useful for the differentiation of the genera.     

Enhancement of sporulation in species of Bipolaris, Curvularia, Drechslera, and Exserohilum by growth on cellulose-containing substrates

Nine species of Bipolaris, Curvularia, Drechslera, and Exserohilum were compared for sporulation on agar media and for enhancement of sporulation by growth on four cellulose-containing substrates (index card, filter paper, cheesecloth, cotton fabric). On two natural and one synthetic agar media, sporulation varied from profuse to nonexistent among three isolates of each species. Growth of all species on cellulose substrates resulted in large and significant increases in sporulation. Growth on index card pieces often provided the greatest increases, but no single substrate was superior for all species, and significant substrate × isolate interactions were observed within species. Overlay of filter paper onto whole colonies in agar plates resulted in 2 to 18-fold increases in sporulation for eight of nine species and production of spores in sufficient quantity for most experimental purposes. Overlay of soil dilution plates with filter paper to promote sporulation of colonies enabled detection of B. spicifera, B. hawaiiensis, C. lunata, and E. rostratum at relatively low population levels (≤1.3 × 10³ colony-forming units per gram of soil) in samples of a naturally infested soil. Results indicate that enhancement of sporulation by growth of species of Bipolaris, Curvularia, Drechslera, and Exserohilum on cellulose substrates may facilitate (i) their identification in culture, (ii) production of spores at relatively high concentrations, and (iii) detection and enumeration of these fungi in soil.     

Identification of b,c, and d cytochromes in the membrane of Vitreoscilla

Cytochromes b, c, d, and o were identified by spectroscopic analysis of respiratory membrane fragments from Vitreoscilla sp., strain C1. Carbon monoxide difference spectra of the reduced membranes had absorption maxima at 416, 534, and 571 nm (ascribed to cytochrome o) and 632 nm (cytochrome d). Derivative spectra of the pyridine hemochromogen spectra of the membranes identified the presence of b- and c-type cytochromes in Vitreoscilla. The cyanide binding curve of the membranes was biphasic with dissociation constants of 2.14 mM and 10.7 mM which were assigned to cytochrome o and cytochrome d, respectively. Membranes bound carbon monoxide with dissociation constant 3.9 M, which was assigned to cytochrome o. Cytochrome c ₅₅₆ and a NADH-p-iodonitrotetrazolium violet reductase component were partially purified from Vitreoscilla membranes.Abbreviations INT p-iodonitrotetrazolium violet - RMF respiratory membrane fragments - K _d dissociation constant - CHAPS 3-[(3-cholamido propyl) dimethylammonio]-1-propanesulfonate - DOC sodium deoxycholate - PAGE polyacrylamide gel electrophoresis - SDS sodium dodecyl sulfate     

Introduction,distribution, spread,and impacts of exotic freshwater gastropods in Texas

We examined the patterns of distribution, vectors of introduction, and potential ecological impacts of freshwater exotic species in Texas over the last 45 years. Currently, five species of exotic gastropods are established: channeled-type applesnail (Pomacea insularum), red-rim melania (Melanoides tuberculatus), quilted melania (Tarebia granifera), giant rams-horn snail (Marisa cornuarietis), and Chinese mysterysnail (Cipangopaludina chinensis). In contrast to the northern part of the US, where shipping appears to be the most important vector for the introduction of aquatic invasive species, aquarium and ornamental trade dominated among unintentional vectors of introduction of all freshwater exotics in Texas, resulting in different patterns of distribution, spread, and ecological impacts. The rate of spread of exotic gastropods in Texas varied from 39 waterbodies colonized over 18 years for P. insularum to only three waterbodies during last 45 years for C. chinensis. Four of five exotic gastropods were found in highly vulnerable aquifer-fed springs and rivers, which contain numerous endemic and endangered species. The fifth species, Pomacea insularum, is an agricultural pest. Potential negative ecological effects of exotic gastropods include impacts on wetlands and wetland restoration, competitive exclusion of native snails, and the introduction of exotic parasites, trematodes, which could infect fish and waterfowl, including federally protected species. Aquifer springs with stable temperature regimes are refuges for both cold and warm intolerant species. Handling editor: D. Dudgeon     

Lack of relationship between gliding cyanobacteria and filamentous gliding heterotrophic eubacteria: comparison of 16S rRNA catalogues of Spirulina,Saprospira, Vitreoscilla,Leucothrix, and Herpetosiphon

Spirulina platensis and Spirulina maxima were characterized by 16S ribosomal RNA oligonucleotide cataloguing. Both species are highly related. They fall into the main group of the cyanobacteria, showing a remote relationship to Nostoc, Fischerella, Aphanocapsa, and also to Prochloron. Low similarity coefficients were found between the Spirulina species and certain organotrophic and sulfide oxidizing bacteria, viz. Saprospira grandis, Vitreoscilla stercoraria, Leucothrix mucor, Herpetosiphon aurantiacus, and Beggiatoa leptomitiformis, respectively. This result does not support the classical hypothesis that certain filamentous gliding bacteria are apochlorotic cyanobacteria.     

Isolation,Biological Properties,and Spatial Structure of Antibiotic Loloatin A

A peptide antibiotic with cyanolytic activity was isolated from the IGM52 strain of the Brevibacillus laterosporus Gram-positive spore-forming bacteria. By ¹H NMR spectroscopy, this antibiotic was identified as loloatin A, a cyclic decapeptide cyclo(-Asn-Asp-Tyr-Val-Orn-Leu-D-Tyr-Pro-Phe-D-Phe-). The spatial structure of loloatin A in solution was determined.