天目山不同海拔毛竹伐除区群落结构变化

以浙江天目山不同海拔(480、580、700和800 m)的毛竹伐除区森林植被为对象,基于群落生态学方法研究2017—2020年各海拔群落的结构变化。结果表明: 2017年所有样地木本植物有515株,隶属于27科43属50种。3 年间增加14科23属30种,个体数量增加116.9%,新增物种主要有毛竹、紫珠、山胡椒、山鸡椒、构树等,主要分布在海拔580和700 m处。2017和2020年海拔580、700和800 m的群落中重要值最大的树种不变,分别为杉木、臭椿和枫香树,而海拔480 m群落重要值最大的树种由杉木变为油茶。各海拔群落径阶分布变化明显。海拔480 m群落径阶分布由倒“J”型发展为单峰左偏态,海拔700 m群落径阶结构由倒“J”型发展为指数型,海拔800 m群落径级分布呈正态分布,峰值由24 cm移到30 cm。3年间各植物群落的Simpson优势度指数和Shannon多样性指数提高,均随海拔升高而显著下降。群落β多样性随海拔升高、海拔间距的增加而增大。2020年新增物种为群落天然更新提供了充足的幼苗幼树,但仍未演替到亚热带顶极群落。     

覆土栽培对高节竹笋品质的影响

为了生产高品质高节竹笋,提高竹林经济效益,该研究通过调查并测定了覆土1a、覆土2a和不覆土栽培的高节竹林竹笋外观形态和营养物质、呈味物质、氨基酸含量,分析了覆土栽培对高节竹笋品质与适口性的影响。结果表明:覆土栽培1a和2a的高节竹笋个体重量及可食率分别较未覆土栽培高节竹笋提高了107.58%、165.73%及8.77%、13.63%,而且高节竹笋个体重量及可食率覆土栽培年限之间差异显著;覆土栽培高节竹笋长度总体显著高于未覆土栽培高节竹笋,且覆土栽培年限之间并无显著差异;高节竹笋基茎则为覆土栽培1a与未覆土栽培之间无显著差异,且均显著低于覆土栽培2a的高节竹笋。覆土栽培高节竹笋蛋白质、单宁、草酸、总酸、纤维素、木质素和各类氨基酸含量及氨基酸总量总体上有明显降低,而脂肪、可溶性糖含量和糖酸比则明显提高;鲜味、甜味和芳香类氨基酸比例有所升高,而苦味氨基酸比例则有所降低。综合分析表明,覆土栽培能明显改善高节竹笋外观形态质量,增加香味和甜味,减少酸涩味和粗糙度,竹笋品质和适口性明显提高,且覆土栽培2a的影响作用更为明显。     

设施菜田水肥管理模式下蚯蚓和土壤肥力状况的变化

通过田间定位试验,研究了设施有机菜田不同水肥(有机肥)管理模式下土壤蚯蚓密度和土壤基本肥力的变化及其关系,为有机菜田的合理灌溉培肥提供科学依据。结果表明:土壤湿度、孔隙度、有机碳、全氮、速效磷和速效钾含量均随有机肥施用量的增多而增加,增加幅度分别为4%~27%、6%~9%、19%~27%、19%~26%、141%~230%和74%~91%;有机肥处理土壤蚯蚓密度比不施肥处理显著提高43%~110%;相关分析表明,土壤蚯蚓密度与土壤生产力、土壤有机碳、全氮、速效磷和土壤孔隙度之间均呈极显著的正相关关系;土壤蚯蚓能够有效指示设施菜田土壤肥力状况,发挥重要的土壤生态功能;减量灌溉常规施肥为设施有机菜田的最佳水肥管理模式。     

不同生境中柔毛淫羊藿形态特征及其有效成分差异分析

采用高效液相色谱法和紫外分光光度法分别测定了不同生境中柔毛淫羊藿的有效成分,并运用one-way ANOVA统计分析了不同生境中柔毛淫羊藿有效成分的差异以及形态参数和生物量的差异。结果表明:3个生境中,相对光照强度较低的生境,其形态参数和植株各个部位的生物量均要低于光照强度相对较强的生境,但3个生境中的整体叶形基本一致;三个生境中淫羊藿总黄酮和淫羊藿苷含量在光照强度较高的生境中要大于光照较低的生境;柔毛淫羊藿植株各个部位的有效成分大小为叶>根>茎;在不同生境中柔毛淫羊藿叶片的黄酮和淫羊藿苷含量都能达到用药标准,其余的部位则不能达到用药标准。因此在人工栽培柔毛淫羊藿时,应模拟野外生长条件,以期提高柔毛淫羊藿质量,替代和保护野生资源。     

Limitations on orchid recruitment: not a simple picture

Mycorrhizal fungi have substantial potential to influence plant distribution, especially in specialized orchids and mycoheterotrophic plants. However, little is known about environmental factors that influence the distribution of mycorrhizal fungi. Previous studies using seed packets have been unable to distinguish whether germination patterns resulted from the distribution of appropriate edaphic conditions or the distribution of host fungi, as these cannot be separated using seed packets alone. We used a combination of organic amendments, seed packets and molecular assessment of soil fungi required by three terrestrial orchid species to separate direct and indirect effects of fungi and environmental conditions on both seed germination and subsequent protocorm development. We found that locations with abundant mycorrhizal fungi were most likely to support seed germination and greater growth for all three orchids. Organic amendments affected germination primarily by affecting the abundance of appropriate mycorrhizal fungi. However, fungi associated with the three orchid species were affected differently by the organic amendments and by forest successional stage. The results of this study help contextualize the importance of fungal distribution and abundance to the population dynamics of plants with specific mycorrhizal requirements. Such phenomena may also be important for plants with more general mycorrhizal associations.     

Differential ecophysiological responses to seasonal drought of three co-existing oak species in northern Greece

Oaks (Quercus spp.) represent the most important broadleaf genus with respect to forest-shaping tree species in the Mediterranean. Considering future climate scenarios (increased drought conditions), the identification of drought tolerant oak species is of great importance for future forest management in this region. The objective of the study was the comparison of physiological status of three economically and ecologically valuable oak species (Quercus ilex, Quercus frainetto and Quercus pubescens) co-existing in natural coppice stands in NE Greece, in response to seasonal drought stress. Measurements were conducted between June and September 2016, every 15–20 days until leaf falling. The parameters studied were predawn leaf water potential and fast chlorophyll fluorescence induction curves (OJIP test), chlorophyll content, and relative water content. Meteorological data from the area were also collected. Photosynthetic parameters such as performance indices (PI_abs and PI_tot) reacted to summer drought conditions, with Q. frainetto showing the lowest values. The discrepancy between species increased with duration of drought period. Q. frainetto revealed the lowest predawn water potential values. The results indicate that Q. frainetto is less suitable for future forestry applications in the studied climate/elevation zone than Q. pubescens and Q. ilex.     

Natural hybridisation between Quercus petraea (Matt.) Liebl. and Quercus pubescens Willd. within an Italian stand as revealed by microsatellite fingerprinting

Interspecific gene flow is frequently reported in the genus Quercus . However, interfertile oak species often seem to remain distinct, even within areas of sympatry. This study employed molecular markers to verify, at a fine scale, the presence of interspecific gene flow in a natural population of Quercus petraea and Quercus pubescens . Within a delimited area of 6 ha, all adult trees belonging to the studied oak complex and seeds from a subsample of such trees were collected and analysed using molecular microsatellite markers. A low interspecific genetic differentiation and a high level of interspecific genetic admixture suggested past hybridisation. Paternity inference of seeds allowed the estimation of pollination frequencies from the three groups of pollen donors ( Q. petraea, Q. pubescens , intermediate). We also assayed pollen viability and germinability of each species group. We observed natural hybridisation between Q. petraea and Q. pubescens, with a predominant component in the direction Q. petraea → Q. pubescens : Q. pubescens displayed a higher level of heterospecific pollination by Q. petraea (25.8%) and intermediate morphotypes (14.7%), compared to Q. petraea acting as pollen receptor (with less than 5% heterospecific pollinations). Intermediate 'mother trees' were pollinated in similar proportions by Q. petraea (23.1%), Q. pubescens (37.8%) and intermediate morphotypes (39.1%). The asymmetrical introgression observed for the studied generation may be caused, among other factors, by the relative abundance of trees from each species group in the studied area.     

Carotenoid composition and down regulation of photosystem II in three conifer species during the winter

Seedlings and coppice shoots of Betula pubescens Ehrh. were grown under controlled conditions designed to simulate the annual growth cycle, and a water stress was introduced during the short day (SD). Alleviation of hud dormancy after increasing periods at chilling temperatures was tested under long day (LD) conditions. Abscisic acid (ABA) was analysed in leaf and bud samples by gas chromatography-mass spectrometry using [²H₄]ABA as the internal standard. Elongation growth of coppice shoots was faster than that of seedlings under both LD and SD conditions, while the final growth cessation occurred in a similar manner and was not affected by water stress, which significantly reduced growth rate in both plant types. Bud dormancy gradually decreased with increasing length of chilling, starting from the basal parts of the plant axis. Water stress did not retard hudhurst. but rather improved it in the chilled coppice shoots and in the non-chilled and partially chilled seedlings. Water content of buds was higher in coppice shoots than in seedlings, but after exposure to SD. it gradually decreased to 45% in both plant types and was not affected by water stress or chilling. The ABA level in both leaves and buds increased during SD treatment and was" enhanced by water stress. No clear differences in bud ABA level were found between the seedlings and coppice shoots under SD conditions, although coppice shoots had less ABA during the preceding LD conditions. There was, in general, no clear effect of chilling on bud ABA level. Budbursl in chilled, single-node cuttings was inhibited by external ABA treatment, which raised the internal ABA levels 10 to 150 times above normal. The observed correlation between ABA level and water content in buds during induction of dormancy under SD and water stress conditions indicates a possible role for ABA in the regulation of dormancy.     

Causal analysis of the invasion of broad-leaved forest by bamboo in Japan

Abstract. In southwestern Tokyo the area covered by bamboo forest has expanded by a factor of 2.7 over the last 26 years. This has mainly been due to bamboo (Phyllostachyspubescens) invading secondary broad-leaved forests, probably after these were abandoned. In the first stage, bamboo sprouts develop from rhizomes at the periphery of the broad-leaved forest and then grow very quickly into young culms. In the next phase culm density increases annually, while the existing broad-leaved trees gradually lose their vitality and die. Finally, the broad-leaved forest is completely replaced by bamboo forest. The competitive ability of bamboo, based on its morphological and growth features, is suggested as the causal factor for the invasion: (1) bamboo can invade a neighboring broad-leaved forest by its vigorous rhizomes; (2) young bamboo culms can break through the canopy of broad-leaved trees; (3) bamboo quickly forms a crown in or above the canopy of the broad-leaved forest; (4) bamboo is very tolerant of strong wind and heavy snow accumulation; (5) bamboo culms, being very pliable during strong wind mechanically damage neighbouring broad-leaved trees.