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1.
闽南山地3种典型植被类型土壤分形与养分特征 总被引：1，自引：0，他引：1
[目的]探索闽南山地不同植被类型土壤分形特征及其与表层土壤颗粒组成、养分含量的相关关系,为评价闽南山地典型植被类型土壤质量,开展土地利用结构调整、土壤侵蚀防治及生态修复等提供参考。[方法]选取土壤颗粒体积分形维数模型对3种典型植被类型林地土壤的分形维数D值进行计算,并与土壤颗粒组成及土壤养分进行相关性分析。[结果]土壤颗粒体积分形维数D值从大到小依次为次生林马尾松林柑橘林;分形维数D值与土壤黏粒和粉粒体积百分数存在显著正相关关系,与砂粒体积百分含量呈显著负相关(p0.05);土壤pH值、全氮、全磷、全钾、水解性氮、有效磷、速效钾和有机碳含量从大到小均为:次生林马尾松林柑橘林;土壤容重为柑橘林马尾松林次生林;分形维数D值与柑橘林的土壤水解性氮含量呈显著正相关,与马尾松林的水解性氮含量、土壤全磷、全钾含量呈显著正相关,与次生林的土壤全磷含量、水解性氮含量呈显著正相关,与有机碳含量均呈显著负相关。[结论]闽南山地不同植被类型会显著影响表层土壤体积分形维数及养分含量,利用土壤体积分形维数可一定程度上反映不同植被类型的土壤颗粒组成及其养分含量。 相似文献
2.
[目的]探明森林类型对土壤碳氮含量和酶活性的影响,为亚热带针叶林改造过程中的树种选择和营林方式选择提供科学依据。[方法]研究相同海拔高度和相近环境条件下的亚热带常绿阔叶林(米槠林)、常绿—落叶阔叶混交林(闽桦—闽楠林)和针叶林(马尾松林)3种森林类型对土壤碳氮储量和酶活性的影响。[结果](1)马尾松林的土壤总有机碳含量显著高于其他两种林分类型,土壤全氮含量与闽桦—闽楠林无显著差异,但二者均显著高于米槠林,马尾松林和闽桦—闽楠林的土壤氮储量和碳储量显著高于米槠林;马尾松林和闽桦—闽楠林的土壤可溶性有机碳含量显著高于米槠林。马尾松林的土壤可溶性有机氮含量显著小于米槠林和闽桦—闽楠林,米槠林和马尾松林的土壤微生物量碳氮含量均显著高于闽桦—闽楠林,3种林分的土壤铵态氮含量无显著差异,而闽桦—闽楠林的土壤硝态氮含量显著高于其他两种林分;(2)米槠林的土壤脲酶活性显著高于闽桦—闽楠林。3种林分的土壤蔗糖酶活性差异显著,表现为：马尾松林>米槠林>闽桦—闽楠林,马尾松林和米槠林的土壤过氧化氢酶活性均显著高于闽桦—闽楠林。3种林分的土壤磷酸酶活性无显著差异,马尾松林的土壤β-葡糖糖苷酶活性显... 相似文献
3.
纳板河自然保护区土壤酶对不同海拔、坡向的响应 总被引：1，自引：0，他引：1
在纳板河自然保护区内分海拔和坡向采集土样,测定分析了尿酶、蛋白酶、蔗糖酶、过氧化氢酶4种主要土壤酶活性和主要养分指标的变化。结果表明:土壤有机质、水解氮含量随海拔升高显著增加;阳坡全氮含量随海拔升高呈现由中间向两端减小的趋势,阴坡全氮含量随海拔升高波动增加;土壤速效磷含量随海拔呈现由中间向两端减小趋势;蛋白酶活性高海拔 > 低海拔,海拔对表层过氧化氢酶活性影响较小,脲酶、蔗糖酶活性随海拔呈现波动。土壤有机质、全氮、水解氮、速效磷含量阳坡 > 阴坡;土壤蛋白酶、过氧化氢酶、蔗糖酶活性阴坡 > 阳坡,各土层土壤脲酶活性阳坡 > 阴坡。各养分含量及酶活性表层 > 中下层。土壤酶活性与各肥力因子间相关关系显著,各土壤酶活性间相关性显著。有机质、全氮、全磷是影响蛋白酶活性的主导因子,速效磷和水解氮为次要因子;全磷、速效磷、水解氮为影响脲酶活性的主要因子,有机质、全磷、速效钾为次要因子。主成分分析结果表明蛋白酶和脲酶活性作为保护区土壤肥力指标具有可行性。 相似文献
4.
几个典型华南人工林土壤的养分状况和微生物特性研究 总被引：37，自引：1，他引：37
为了了解华南主要树种对土壤肥力的影响,分别用土壤化学分析方法、稀释平板法和酶分析法对相似立地条件的杉木林、马尾松林、湿地松林、马占相思林和尾叶桉林的凋落物养分、土壤养分、微生物数量及酶活性进行了研究。结果表明,5种林分中,杉木林的凋落物储量最大,凋落物的养分储量较大,为94.08kg hm-2。5种林地均呈强酸性。杉木林的土壤肥力较高,有机质、全氮、全磷、全钾、碱解氮、速效磷和速效钾含量分别为25.54 g kg-10、.96 g kg-1、0.37 g kg-11、2.04 mg kg-1、64.42 mg kg-1、1.87 mg kg-1、41.88 mg kg-1,但是土壤微生物数量小;马尾松林、湿地松林凋落物的养分储量小,土壤养分含量较低,土壤肥力低;马占相思林有效地改善了土壤化学性质,凋落物的养分储量在5种林分中最大,达106.2 kg hm-2,土壤肥力高,有机质、全氮、全磷、全钾、碱解氮、速效磷和速效钾含量分别为23.42 g kg-1、0.93 g kg-1、1.28 g kg-1、15.29 mg kg-1、69.32 mg kg-1、1.98 mg kg-1、76.88 mg kg-1,微生物数量大,酶活性强;尾叶桉林的土壤有机质、N和P含量低,K含量高,微生物数量小和酶的活性较低,土壤肥力低。 相似文献
5.
伊犁河谷不同造林模式土壤养分与酶活性的关系 总被引：1，自引：1，他引：0
[目的]研究伊犁河谷5种典型造林模式下土壤养分和酶活性空间特征,为伊犁河谷地区造林树种的搭配和布局提供依据。[方法]通过采样和室内测试分析,对0—20和20—40cm土壤的化学性质及酶活性等指标进行分析测定,并对其相关性进行研究。[结果]0—20的土层土壤酶活性更强,养分含量也更高;各模式土壤养分含量差异显著,榆树防护林土壤碱解氮和有效磷含量最高,全钾和有效钾处于较高水平,林草间作用材林土壤全氮、全磷和有机质含量最高,碱解氮也处于较高水平;土壤酶活性与土壤养分有一定的相关,其中脲酶与全磷、碱解氮、速效磷和有机质显著正相关,过氧化氢酶与全钾和速效钾呈显著正相关,与全氮、全磷、碱解氮和有机质呈显著负相关。[结论]土壤酶活性与土壤养分间关系紧密,并可较好表征土壤肥力水平,可广泛应用于森林土壤的肥力水平评价。 相似文献
6.
探究土壤有机碳(SOC)矿化的激发效应(Priming effect, PE)对了解森林土壤碳吸存具有重要意义。凋落叶输入是调节激发效应的重要因素,其对激发效应的影响可能受到关键养分(如磷)的制约。在亚热带低磷土壤中,凋落叶和磷添加如何影响森林土壤碳矿化和激发效应目前仍不清楚。以马尾松林土壤为研究对象,探究三种凋落叶(马尾松(Pinus massoniana)、火力楠(Michelia macclurei)和枫香(Liquidambar formosana))和磷(KH2PO4)添加对土壤激发效应,土壤养分及微生物特性的影响。结果表明,三种凋落叶添加均显著增加了SOC矿化,产生了正激发效应,且马尾松凋落叶诱导的激发效应强度最大,火力楠凋落叶次之,枫香凋落叶诱导的激发最弱。此外,凋落叶添加整体上降低了速效氮 (AN)的含量,却增加了微生物生物量氮(MBN)和微生物生物量磷(MBP)的含量,提高了β-葡萄糖苷酶(βG)和酸性磷酸酶(ACP)的活性。单独添加磷显著增加了SOC矿化,且提高了土壤有效磷(AP)、可溶性有机碳(DOC)和微生物生物量碳(MBC)、MBN和MBP的含量。而与单独添加凋落叶相比,火力楠和枫香凋落叶与磷共同添加显著降低了土壤激发效应的强度和ACP的活性。回归分析结果表明,累积激发效应与AP、MBN和MBP含量显著负相关,与ACP活性呈显著正相关。综上,凋落叶添加刺激了微生物生长,产生了正激发效应,且激发强度与凋落叶质量有关;而磷添加可能会降低低质量凋落叶产生的土壤激发效应。 相似文献
7.
太湖上游西苕溪近岸森林土壤氮磷养分差异特征 总被引：5，自引：0，他引：5
近岸森林土壤受到河水涨落等自然侵蚀和人类活动的双重扰动,增加了土壤养分流失威胁,从而增大了下游河流和湖泊富营养化的风险,影响森林作为河岸缓冲带作用的发挥。对河岸森林土壤养分的研究,可为河岸森林树种的选取、河岸带建设、经营与管理等提供依据。以太湖上游的西苕溪两岸1km范围内的森林为研究对象,选择典型竹林、经济林、纯林和混交林样地34块,分层采集土壤样品,实验室测定有效磷、碱解氮、全氮和全磷等养分含量,利用变异系数分析不同森林类型和不同深度土层中养分含量的变异性,并且采用单因素方差分析和多重比较的方法分析土壤养分含量在不同森林类型间同一深度土层的差异性。结果表明,竹林土壤有效磷、碱解氮、全氮和全磷均具有较高的变异性,经济林土壤中的有效磷和全氮的变异较大,纯林和混交林土壤养分的变异性总体上较低;土壤有效磷、碱解氮和全氮平均含量在不同林型中都表现为0-10cm〉10-30cm〉30-50cm,即随着土层的加深养分含量降低;土壤有效磷含量竹林显著高于纯林,不同土层竹林与经济林的碱解氮含量显著高于纯林和混交林的;经济林的全氮含量较其他林型的较低,而全磷的含量却较高。 相似文献
8.
蕉园土壤养分和酶活性周年动态变化及对植被覆盖的响应 总被引：1，自引：0，他引：1
《土壤通报》2020,(3):677-685
本文拟研究了植被覆盖对香蕉土壤养分含量和土壤酶活性的影响,以期为覆盖植物对香蕉生产可持续发展性提供理论依据和技术支持。在亚热带干热河谷蕉园内,设置无覆盖、自然杂草和豆科覆盖3种植被覆盖方式,通过不同季节(春、夏、秋、冬)、不同土壤区域(种植区和覆盖区)的土壤养分含量和酶活性测定结果,分析植被覆盖对蕉园土壤质量的影响。结果表明,(1)蕉园土壤的理化性质和酶活性变化呈明显的周年动态特征,从秋季至翌年夏季,土壤pH值和有机质含量显著降低,土壤脲酶、蔗糖酶、过氧化氢酶、磷酸酶活性增加。(2)覆盖区土壤的养分含量和酶活性与种植区明显不同,前者土壤pH值、磷酸酶、过氧化氢酶活性相对较高而土壤养分和含量、有机质含量、蔗糖酶、脲酶活性相对较低,后者反之。(3)植被覆盖可显著改变蕉园土壤理化性质及酶活性;与无覆盖处理相比,豆科覆盖提升了覆盖区土壤的有效磷含量、过氧化氢酶、蔗糖酶、脲酶活性以及种植区土壤有机质和氮、磷含量;自然杂草区降低了土壤的pH值、有效磷和速效钾含量降低,尤其在种植区,而相应增加了土壤的磷酸酶活性升高。总体而言,蕉园豆科植物覆盖可显著提高土壤有机质、养分含量及酶活性,可作为改善蕉园土壤质量的有效方式。 相似文献
9.
不同植被覆盖对养分在土壤水稳性团聚体中分布特征的影响 总被引：5，自引：2，他引：5
研究了重庆缙云山不同植被覆盖下土壤结构的稳定性,以及土壤有机碳和养分在水稳性团聚体中的分布特征.结果表明:不同植被覆盖对土壤水稳性团聚体的分布和土壤结构稳定性有显著影响.竹林土壤>0.25 mm水稳性团聚体含量以及土壤结构的稳定性显著低于马尾松林和草地土壤.植被覆盖对养分在土壤水稳性团聚体中的分布模式没有显著影响,在>2mm水稳性团聚体和<0.053 mm粒级的粉砂与粘粒组分中,有机碳、全氮、全磷以及交换性K~+、Na~+、Ca~(2+)、Mg~(2+)的浓度最高;地表植被覆盖的变化对有机碳、全氮、全磷和交换性盐基离子在各粒级水稳性团聚体中的含量产生显著影响,草地和竹林土壤有机碳和全氮显著高于马尾松林土壤,主要表现在0.25-0.053 mm粒级水稳性团聚体中有机碳和全氮含量,草地和竹林土壤显著高于马尾松林土壤;而草地土壤>2 mm水稳性团聚体和<0.053 mm粒级的粉砂与粘粒组分中的磷显著高于马尾松林和草地土壤.不同植被覆盖下土壤水稳性团聚体中交换性盐基离子均以Ca~(2+)、Mg~(2+)为主,占交换性盐基总量(Total exchangeable bases TEB)的91.8%～92.9%.草地土壤各个粒级的TEB都要大于其他两种植被覆盖下的土壤. 相似文献
10.
林分密度对马尾松林下土壤养分及酶活性的影响 总被引：4，自引：0，他引：4
以退化马尾松林下土壤为对象,通过调查我国红壤丘陵区典型林分密度的马尾松人工林,研究林分密度对土壤养分和土壤酶活性的影响。3种林分密度中,1 560株/hm2 左右中等林分密度的马尾松土壤有机质、全氮、全钾、速效钾、全磷、交换性钙和交换性镁等较高,但土壤酸化也较严重;同时,1 560株/hm2 左右马尾松林的土壤转化酶活性、脲酶活性和多酚氧化酶活性均较高,但过氧化氢酶活性表现最低;林分密度对马尾松土壤酸性磷酸酶活性影响不明显。因此,适宜林分密度的马尾松人工林一定程度上可改善该区林下土壤肥力及生化强度。 相似文献
11.
In order to identify key adaptive traits which affect productivity in Mediterranean grain and forage legumes and simultaneously determine the agricultural potential of a wide range of Vicia species, germplasm collected from the wild throughout the eastern Mediterranean was grown under semi-arid conditions in Tel Hadya, Syria (313 mm growing season rainfall). These included species currently in use in Mediterranean agriculture, such as V. sativa L., as well as those more widely used in the past-such as V. ervilia L., but also a broad selection from Section Narbonensis (B. Fedtsch. ex Radzhi) Maxted, including V. narbonensis L, V. johannis Tamamsch., V. hyaeniscyamus Mout., V. serratifolia Jacq., and V. kalakhensis Khattab et al. V. faba, a near relative of the taxa in Section Narbonensis, was included as a domesticated control. Where applicable, a representative range of subspecies was used. Accessions were chosen from a wide range of habitats in terms of latitude (31.02–40.72 decimalo), longitude (27.1–43.17 decimalo), altitude (20–1510 m), rainfall (180–1700 mm/yr) and soil depth (5–50 cm) in order to maximise diversity within species. Agricultural potential was determined by measuring seed, hay and biological yield, as well as agronomic traits such as harvest index, standing crop height, and seed size. The comparative influence of phenology and key agronomic traits such as plant habit and seed size on productivity varied tremendously between species, depending on their reproductive strategies. In V. sativa and V. ervilia, the smaller seed species which rely on long vegetative phases and growing seasons to accumulate sufficient biomass to set seed, and in which there was comparatively little agronomic variation, phenology had a large impact on yield. In early emerging taxa such as V. ervilia and V. s. subsp. sativa, with built-in long vegetative phases and growing seasons, seed yield was negatively correlated with flower ing (r = –0.86 to –0.88), whereas the opposite was the case for later emerging taxa such as V. s. subsp. nigra (L.) Ehrh. (r = 0.95). Within V. narbonensis and relatives, the larger seeded Vicia species which rely on more conservative reproductive strategies where high seedling vigour associated with large seeds enables the species to enter reproductive phases relatively early, phenology had a much smaller impact on yield than did variation of key traits such as seed weight, plant habit and pod shattering. Among the undomesticated germplasm harvest indices ranged from 0.09–0.31, hay yields from 0.1–3.4 t/ha, seed yield from 0–2.0 t/ha, and dry matter at maturity from 1.6–6.5 t/ha. Sub-specific taxonomy was crucial in determining agronomic potential. V. narbonensis var. aegyptiaca Kornhuber ex Asch. et Schweinf. showed the most potential, combining an upright habit, large seeds (212 mg) and tendency to retain intact pods after maturity, with the highest yield, harvest index and crop height of all the wild Vicia species. V. sativa subsp. sativa, V. ervilia and V. narbonensis var. narbonensis were less productive, but still showed agricultural potential. The smaller seeded V. narbonensis, var. affinis, var. jordanica H. Schäf. and var. salmonea (Mout.) H. Schäf., and their close relatives V. johannis, V. hyaeniscyamus, V. serratifolia and V. kalakhensis have little to offer Mediterranean agriculture on the basis of poor agronomy. 相似文献
12.
The difficulty and problems encountered in the study of cultivated plants, in general and sugarcane, in particular has been
indicated. In order to understand these problems, a brief review on the taxonomy of Saccharum and closely related taxa, namely, Erianthus, Sclerostachya, Narenga and Miscanthus (generally known as ‘Saccharum complex’) has been given. A short account on the important morphological features that are specific to sugarcane has also
been stated as classification is commonly based on such morphological characters. A note has been added on the chromosome
number, origin, and distribution of the species of ‘Saccharum complex’ members. Taxonomic keys have been devised for identification of the genera of Saccharinae and for the species of
Saccharum and Erianthus occurring in India. A new combination, Sclerostachya fallax (Balansa) Amalraj et Balasundaram, has also been proposed. 相似文献
13.
14.
M. Rodríguez-Quijano M.T. Nieto-Taladriz J.M. Carrillo 《Genetic Resources and Crop Evolution》2001,48(6):599-607
A collection of 136 accessions of Aegilops umbellulata (39), Ae. comosa (75) and Ae. markgrafii (22) was analysed for high-molecular-weight (HMW) glutenin subunits composition. The homogeneity of the accessions was studied and 55.1% of the collection was homogeneous for HMW glutenin subunits (29 Ae. umbellulata, 33 Ae. comosa and 14 Ae. markgrafii). The HMW glutenin subunits of Ae. umbellulata are encoded by the Glu-U1 locus; in Ae. comosa results showed that this proteins are encoded at the 1M chromosome, and the locus was named Glu-M1. In Ae. markgrafii it was assumed that HMW glutenin subunits were encoded by an homoeologous locus and it was named Glu-C1. All the accessions of Ae. umbellulata and Ae. markgrafii expressed both, x-type and y-type subunits. Among the Ae. comosa accessions, only one expressed an x-type subunit alone. All the accessions of Ae. umbellulata and some of Ae. comosa had x-type glutenins of higher molecular weights than those commonly present in bread wheat. A total of 8 alleles were detected at the Glu-U1 locus, 11 at the Glu-M1 and 4 at the Glu-C1. The new HMW glutenin variation found in this work suggests their possible utilisation in breeding for wheat quality. 相似文献
15.
16.
The effects of five agroforestry woody species (Dactyladenia barteri, Gliricidia sepium, Leucaena leucocephala, Senna siamea andTreculia africana) on the surface aasting activity ofHyperiodrilus africanus were studied in an Alfisol (Oxic Paleustalf) in southwestern Nigeria. Casting activity under the woody species decreased in the following order:Dactyladenia sp. (26.4 Mg ha-1 year-1)>Gliricidia sp. (24.4 Mg ha-1 year-1)>Treculia sp. (22.9 Mg ha-1 year-1)>Leucaena sp. (18.6 Mg ha-1 year-1)>Senna sp. (18.3 Mg ha-1 year-1). These differences in casting activity were partly explained by microclimatic effects. Irrespective of the woody species, the worm casts were higher in clay and silt contents, bulk density, water-stable aggregates, pH, organic C, exchangeable cations, effective cation exchange capacity, and extractable P levels than the corresponding surface soils. The woody species did affect the physicochemical properties and P sorption of the worm casts. The content of water-stable aggregates of worm casts decreased in the following order:Dactyladenia sp.>Treculia sp.>Senna sp.>Leucaena sp.>Gliricidia sp. Large differences in extractable P levels were observed.Senna sp. was associated with the highest extractable P level (11.5 mg kg-1) andTreculia sp. the lowest (4.9 mg kg-1). P sorption was highest on worm casts underDactyladenia sp. and lowest on those underTreculia sp. Without fertilizer application, there were no significant differences in the dry weight of maize grown in the different worm casts. With NPK applications, the dry weight of maize grown in worm casts associated withTreculia sp. was significantly lower than that of maize grown in the other worm casts, mainly due to the low extractable P level. Despite a high organic C and exchangeable K status, maize grown in the worm casts still responded significantly to N and K applications. The N uptake by maize grown in worm casts associated withTreculia sp. was lower than that in the other treatments. 相似文献
17.
Sofie E. De Meyer Koenraad Van Hoorde Bram Vekeman Tamara Braeckman Anne Willems 《Soil biology & biochemistry》2011,43(12):2384-2396
We investigated the diversity of rhizobia isolated from different indigenous legumes in Flanders (Belgium). A total of 3810 bacterial strains were analysed originating from 43 plant species. Based on rep-PCR clustering, 16S rRNA gene and recA gene sequence analysis, these isolates belonged to Bradyrhizobium, Ensifer (Sinorhizobium), Mesorhizobium and Rhizobium. Of the genera encountered, Rhizobium was the most abundant (62%) and especially the species Rhizobiumleguminosarum, followed by Ensifer (19%), Bradyrhizobium (14%) and finally Mesorhizobium (5%). For two rep-clusters only low similarity values with other genera were found for both the 16S rRNA and recA genes, suggesting that these may represent a new genus with close relationship to Rhodopseudomonas and Bradyrhizobium. Primers for the symbiotic genes nodC and nifH were optimized and a phylogenetic sequence analysis revealed the presence of different symbiovars including genistearum, glycinearum, loti, meliloti, officinalis, trifolii and viciae. Moreover, three new nodC types were assigned to strains originating from Ononis, Robinia and Wisteria, respectively. Discriminant and MANOVA analysis confirmed the correlation of symbiosis genes with certain bacterial genera and less with the host plant. Multiple symbiovars can be present within the same host plant, suggesting the promiscuity of these plants. Moreover, the ecoregion did not contribute to the separation of the bacterial endosymbionts. Our results reveal a large diversity of rhizobia associated with indigenous legumes in Flanders. Most of the legumes harboured more than one rhizobial endosymbiont in their root nodules indicating the importance of including sufficient isolates per plant in diversity studies. 相似文献
18.
The phylogenetic relationships within the genus Actinidia and among 3 allied genera Clematoclethra, Saurauia, and Sladenia have been very controversial. In order to understand the systematic implication of foliar trichomes in those genera, the micromorphological characteristics of foliar trichomes from 34 taxa were examined by means of light microscopy and scanning electron microscopy (SEM). The observed micromorphological characteristics were classified into eight main types. A phylogenetic analysis of Actinidia and related genera based on 15 micromorphological characters of foliar trichomes was conducted using Wagner parsimony method and Sladenia celastrifolia, Rhododendron hybridum and R. simsii as a complex outgroup. In the resulting phylogenetic tree, Actinidia is shown to be a monophyletic group, and Clematoclethra and Saurauia form another monophyletic group. This study also presents the phylogenetic relationships among 4 sections within the genus Actinidia: the monophyly of sect. Leiocarpae and of sect. Strigosae, and polyphyly of sect. Maculatae and of sect. Stellatae. 相似文献
19.
Diversity of native rice (Oryza Poaceae:) species of Costa Rica 总被引：1，自引：0，他引：1
Alejandro Zamora Cynthia Barboza Jorge Lobo Ana M. Espinoza 《Genetic Resources and Crop Evolution》2003,50(8):855-870
We found several populations of wild Oryza species in the lowlands of Costa Rica. The plants showed extensive morphological variation, suggesting the presence of several species. In the morphologic study, 33 traits were scored for plants of all the species. A principal component analysis revealed the significant morphological separation of the different species. The analyses indicated that there are three species, O. grandiglumis, O. latifolia and O. glumaepatula. Two putative hybrid types were found, both significantly differing in their morphology from the known species and intermediate at several traits. O. grandiglumis is a new record for Costa Rican flora. Its main population is located in Caño Negro Wildlife Refuge, Los Chiles, Alajuela. O. latifolia is distributed throughout the lowlands of the country and the plants of the Atlantic slope are significantly bigger in general habit than those of the Guanacaste area. During this study a population of O. glumaepatula of hundreds of thousands of plants was discovered in the Medio Queso River wetland, Los Chiles, Alajuela. This population is the most important source of genes for cultivar's improvement from the primary gene pool of rice in Costa Rica. The small ligule and the wide flag leaf characteristic of the two CCDD species separated them from the AA diploid O. glumaepatula. Seed size, ligule size, number of branches in the panicle, plant height and sterile lemma length are all bigger in O. grandiglumis, and influenced the second factor that separated the CCDD species in two discrete clusters. The species found offer great possibilities for the improvement of rice cultivars and they should be thoroughly studied and appropriately protected. 相似文献
20.
Laboratory experiments were carried out to investigate the fate of bacteria during and after passage through the intestinal tract of detritivore earthworms. Earthworms (Lumbricus spp.) were fed with cattle dung inoculated 7 days previously with one of five different Gram-negative bacteria. Bacterial concentrations were determined 2 days later in dung and soil, and in gut material from different parts of the earthworm intestinal tract. A high percentage (28–82%) of the total bacteria (epifluorescence direct counts) in the earthworm gut content was culturable. The concentration of total heterotrophic aerobic bacteria did not vary significantly among the five different bacterial additions and the non-inoculated control. In earthworm casts the number of total heterotrophs per gram dry matter (2.1×109) was higher than in soil (1.7×108), but lower than in the dung (1.5×1010). The test-bacteria, however, showed different survival patterns along the earthworm intestinal tract. The concentrations of Escherichia coli BJ 18 and Pseudomonas putida MM 1 and MM 11 in earthworm casts were lower than in the ingested dung, while concentrations of Enterobacter cloacae A 107 and Aeromonas hydrophila DMU 115 in dung and casts were similar. Ent. cloacae, and to aminor extent E. coli, were reduced in numbers by several orders of magnitude in the pharynx and/or crop. In the hind gut, however, the concentration of Ent. cloacae had increased to the same level as in the ingested dung, while the concentration of E. coli remained low. Our observations indicate that the bacterial flora of ingested food materials changes qualitatively and quantitatively during gut transit. 相似文献