Edge effects on soil seed banks and understory vegetation in subtropical and tropical forests in Yunnan,SW China

Human-induced forest edges are common in many forest landscapes throughout the world. Forest management requires an understanding of their ecological consequences. This study addressed the responses of three ecological groups (non-forest species, secondary forest species and primary forest species) in edge soil seed banks and edge understory vegetation, and explored the relationship between the invasion of non-forest species in edge understory vegetation and the accumulation of their seeds in edge soil seed banks. The soil seed banks and understory vegetation were sampled along transects established at the edges of a continuous subtropical evergreen broad-leaved forest tract (Lithocarpus xylocarpus forest) bordering anthropogenic grasslands and three tropical seasonal rain forest fragments (Shorea wantianshuea forest) bordering fallows. Species composition in both soil seed banks and understory vegetation showed great difference among edge sites. In soil seed banks, the dominance (relative abundance and relative richness) of each ecological group did not change significantly along the edge to interior gradient. In understory vegetation, the invasion of non-forest species concentrated on the first several meters along the edge to interior gradient. The dominance of secondary forest species decreased with distance from the edge, while the dominance of primary forest species increased with distance from the edge. In forest edge zones, the invasion of a majority of non-forest species in understory vegetation lags behind the accumulation of their seeds in soil seed banks. Forest edges do not act as a good barrier for the penetration of non-forest species seeds. The lack of non-forest species in understory vegetation must then be due to conditions that are not appropriate for their establishment. Therefore, to prevent germination and survival of non-forest species further into the forest, management should focus on maintaining interior forest conditions.     

Germination characteristics and diversity of soil seed banks and above-ground vegetation in disturbed and undisturbed oak forests

The destruction of natural ecosystems is an important issue in many parts of the world. In the west of Iran, a vast area of the Zagros Mountain range is covered by typical vegetation including several rare plant species, of which many are currently considered endangered by anthropogenic activities. Despite the important role of soil seed banks to help conserve these degraded plant communities, the floristic studies in the Zagros forests have only focused on above- ground vegetation. In this study, the characteristics of soil seed banks and above-ground vegetation were examined at two forest sites： an undisturbed control （Un） and a disturbed （D） site. The objectives of this study were 1） to investigate the diversity of above-ground vegetation and soil seed banks in disturbed and undisturbed forests, 2） to examine the soil properties and the germination characteristics of the soil seed bank in disturbed and undisturbed oak forests and 3） to estimate the potential of soil seed banks in the restoration of disturbed sites. The results show that soil properties between Un and D sites were significantly different with higher values of pH, NH4-N, N~o,, CEC, OC, clay and canopy percentage in the Un site than in the D site. The Simpson diversity, Margalef richness and evenness indices differed significantly between sites, either for the soil seed banks or the above-ground vegetation. After a period of 26 weeks, the germination speed and the mean daily number of germinants were significantly different between Un and D sites. Without other conservation measures, soil seed banks alone cannot result in a full recovery after severe disturbances in the oak forests of Zagros.     

Seed supply and the regeneration potential for plantations and shrubland in southern China

Assessing the characteristics of seed supply will be vital to better understand the dynamics of forest regeneration. In this study, we surveyed the aboveground vegetation, the seed rain, the seed bank, and natural seedling emergence in four typical 24-year-old plantations (eucalyptus, mixed-native, mixed-legume, and mixed-conifer) and a naturally successioned shrubland in southern China. The dominant species in the understory were similar among the five plant communities. The seed rain and the seed bank were dominated by shrubs and herbs but indigenous tree species were rare. Species that were common to all five-plant communities represented a great proportion of the seeds in the seed rain and seed bank. The seed rain consisted mostly of seeds derived from the local plant community. Seed abundance was greater in the seed bank than in the seed rain, and species richness was greater in the seed bank and in the corresponding plant community than in the seed rain. Species composition similarity between the seed rain, the seed bank, and the aboveground vegetation was low, because the seed rain contained much fewer species, and the seed bank and aboveground vegetation contained many different species, respectively. These findings indicate that both the seed rain and the seed bank play important roles in providing seeds for plant recruitment in the understory, but the seed bank contributes more than the current seed rain to the diversity of recruited plants. The current plant community has little impact on the qualitative composition of the seed rain and seed bank. Based on these data, it appears that succession to the desired zonal, mature forest community is unlikely to result from seeds in the seed rain or seed bank. Lack of seed availability of desired zonal mature forest species is the main bottleneck currently limiting succession in the plantations. Reintroduction of late-successional species could facilitate the desired succession.     

Mangrove community recovery potential after catastrophic disturbances in Bangladesh

The objective of this study was to compare the variation in the soil seed banks and the aboveground vegetation in relation to three habitats, i.e., swamp forests, grassland and sand dunes within the Sundarbans mangrove forests of Bangladesh. We collected vegetation data (species and their percentage cover) by using quadrat sampling: 10 m × 10 m for swamp forests and 5 m × 5 m for grassland and sand dunes. We estimated the density of viable seeds of species in the seed bank by counting germinants from soil cores in a germination chamber. Species richness and composition of both aboveground vegetation and the soil seed banks differed significantly among habitats. We identified a total of 23 species from the soil seed bank. Of these, two were true mangrove species and the remaining were non-mangrove species, including halophytic grasses, herbs and mangrove associate species. Our results confirm that mangrove species do not possess a persistent soil seed bank. The presence of high-density non-mangrove and associated mangrove species in the soil seed bank implies that after frequent catastrophic disturbances which limit incoming propagules from adjacent forest stand, large canopy gaps can easily become invaded by non-mangrove and mangrove associate species. This would result in the formation of a cover of non-mangrove species and cryptic ecological degradation in mangrove habitats. We suggest that forest managers should actively consider gap plantations with mangrove species in the large canopy gaps created after catastrophic disturbances to counteract the invasion of non-mangrove species and cryptic ecological degradation.     

Soil seed banks in four 22-year-old plantations in South China: Implications for restoration

To better understand the potentials of the soil seed banks in facilitating succession towards a more natural forest of native tree species, we quantified the size and composition of the soil seed banks in established plantations in South China. The seed banks were from four typical 22-year-old plantations, i.e., legume, mixed-conifer, mixed-native, and Eucalyptus overstory species. Species diversity in the seed banks was low, and the vegetation species differed from those found in the seed bank in each plantation. A total of 1211 seedlings belonging to eight species emerged in a seedling germination assay, among which Cyrtococcum patens was most abundant. All species detected were shrubs and herbs, and no viable indigenous tree seeds were found in soil samples. Size and species composition of the seed banks might be related to the overstory species compositions of the established plantations. The seed bank density in soils was highest in the mixed-conifer plantation followed by Eucalyptus, mixed-native, and legume plantations. Species richness among the seed banks of plantations was ranked as follows: Eucalyptus > mixed-conifer > mixed-native = legume. The results indicated that the soil seed banks of the current plantations are ineffective in regenerating the former communities after human disturbances. Particularly, the absence of indigenous tree species seeds in the seed banks would limit regeneration and probably contribute to arrested succession at the pioneer community stage. It would appear from these data that the soil seed banks under the current plantations should not be considered as a useful tool leading the succession to more natural stages. Introduction of target indigenous species by artificial seeding or seedling planting should be considered to accelerate forest regeneration.     

松嫩草地不同次生光碱斑种子流比较及其潜在生态恢复意义

在松嫩平原不同退化程度的草地中选取三个次生光碱斑,通过分析其土壤种子库和表面种子流动态,探讨了土壤表面种子流在次生光碱斑植被恢复中的潜在作用。研究结果表明:样地间种子流种类与数量上相似性很高,且种子流与周围植被具有一定的相关性。土壤表面种子流数量巨大,且以一年生耐盐碱的先锋植物(虎尾草和碱蓬)种子为主,占总流量的 96 %。虽然土壤表面的种子流量巨大,但次生光碱斑对种子的截留能力很低,土壤种子库得不到及时更新与补充,常处于较低水平,尤其在 5 月份和 6 月份,土壤中甚至没有种子出现。土壤种子库和表面种子流表现出季节性动态变化,均在 10 月份达到最大。土壤种子库缺乏是限制次生光碱斑的植被自然恢复能力的一个重要因素。因此,表面种子流是潜在的种子资源,提高次生光碱斑对种子的截留能力(人工处理方式),将加速次生光碱斑的植被恢复进程。图 5 表2 参 27。     

香格里拉亚高山不同退化程度森林群落土壤种子库的特征研究

2006～2007年采用种子萌发法,对香格里拉亚高山不同退化森林群落的土壤种子密度、丰富度,物种组成及地上植被组成开展了调查研究。结果表明:(1)亚高山土壤种子库中共有42个种子植物,种子密度为471～891粒/m2;(2)退化林地种子库中的物种密度依次为重度退化>极度退化>中度退化>轻度退化>未退化,物种丰富度依次为轻度退化>未退化>极度退化>中度退化>重度退化;(3)多年生草本植物在5类群落中均占绝对优势,只在未退化林地中发现木本植物;(4)土壤种子库及地上植被在物种组成上具有较小的Jaccard相似系数;(5)11月份物种数量及种子密度比4月份及7月份高;(6)0～5 cm表土种子库中具有较高的物种数量及种子密度;(7)种子扩散、地上植物的无性繁殖及人工造林是恢复香格里拉亚高山退化植被的有效途径。     

Floristic composition and spatial distribution of germinable seeds in a spruce plantation

Introduction

The logging of several spruce plantations is planned for the next years in the Eifel National Park (Western Germany). To understand the ecological mechanisms of spontaneous forest regeneration that follows these impacts, it is crucial to investigate the species composition and functional diversity of the buried germinable seeds in those stands.

Methods

We analysed the soil seed bank by germination method and characterised germination dynamics and distribution of seedlings throughout the samples according to a sigmoid model and cumulative curves, respectively. To compare the proportions of functional and syntaxonomical groups between seed bank and aboveground vegetation, we applied the Fisher??s exact test. Additionally, we described the spatial distribution of the species in the seed bank according to semivariograms.

Results

The studied seed bank reached a density of about 5,300 seed?m^?2. Most of the species detected in the seed bank are related to open vegetation, forest fringes and early successional stages of forest regeneration. In spite of a low floristic similarity between seed bank and aboveground vegetation, the functional and syntaxonomical composition is very similar. Further studies considering the distribution of seeds in the soil and the changes of the seed bank composition during the regeneration process are required.     

桑植石漠化林地植物多样性及群落数量特征分析

以湖南桑植县石漠化区为研究对象,采用样方调查法对3个不同石漠化等级样地进行植被调查,分析不同石漠化等级植物物种组成结构及植物多样性指数差异,并根据Jaccard群落相似性原理进行不同石漠化等级植物群落间的相似度评价分析.结果表明:调查区共出现草本植物23科39种、木本植物26科38种,优势科为菊科、蔷薇科、百合科、禾本...     

庞泉沟自然保护区河岸林群落的土壤种子库特征

以人工拣种结合种子萌发法研究了庞泉沟自然保护区9种河岸林群落的土壤种子库特征,结果表明: 9种群落的土壤种子库密度间于684±108 - 2 696±266粒·m^-2,69.27% - 88.65%的种子留存于0 - 5 cm的层次,沙棘灌丛的种子库密度最大,乌柳灌丛最小;离河岸10 m和20 m处的种子库密度大于岸边、离河岸30 m和40 m处;种子库包含的40种植物以多年生草本为主,灌木和草本种多为耐干扰种,存在典型的湿地植物,但种子储量以先锋种白桦最丰;辽东栎无完整种子,白桦、华北落叶松、云杉和油松的种子活力保持期为1 - 2年,多数草本的种子活力保持期超过2年;按照群落土壤种子库的相似性,将群落划分为林分开始期、林分排除期、下层再现期和老熟期4个演替阶段。演替后期群落的种子库密度、丰度以及与地上植被的相似性都小于前期群落。土壤种子库是森林自然更新及种群恢复的重要基础,本文对于研究地区河岸林的保护和重建具有重要的理论意义。     

林木抗旱生理研究进展

从林木的表型特征、生理生化特性、抗旱分子生物学与抗旱基因表达3方面对国内外林木抗旱性研究进行综述。当前国内外学者对植物叶茎根的表形特征、渗透调节、光合生理、叶绿素荧光变化、活性氧代谢、植物激素的研究较多, 而对受干旱胁迫下林木的分子生物学与基因表达研究相对较少。最后提出了林木抗旱生理研究的主要评价方法、研究指标、研究方法与内容。随着技术的发展及相关研究的深入, 抗旱分子生物学与抗旱基因等方面的研究将成为林木抗旱生理方面的热点。     

Native woody species regeneration in exotic tree plantations at Munessa-Shashemene Forest,southern Ethiopia

Regeneration of native woody species was studied in the plantations and the adjacent natural forest at Munessa-Shashemene Forest Project Area, Ethiopia. The aim of the study was to test the hypothesis that tree plantations foster regeneration of native woody species. A total of 60 plots, having 10 × 10 m area each, were studied in monoculture plantations of 4 exotic species (Cupressus lusitanica, Eucalyptus globulus, E. saligna, Pinus patula) and an adjacent natural forest. Ages of the plantations ranged between 9 and 28 years. Soil seed bank analysis was also undertaken from soil samples collected in each of the 60 plots to examine the similarity between the soil seed flora and aboveground vegetation. A total of 56 naturally regenerated woody species were recorded beneath all plantation stands with densities ranging between 2300 and 18650 individuals / ha in different stands. There was a significant difference among plantation stands with regard to understorey density (standard deviation: 4836 ± 1341). Vegetation diversity was assessed through analyses of floristic composition, species richness and abundance. Generally, seedling populations were the most abundant components of the regeneration in most of the plantation stands, forming 68 % of the total regeneration count in all stands. A total of 77 plant species represented by 44 herbs, 13 woody species, 8 grasses and 12 unidentified species were recorded in the soil seed bank from all stands. Similarity between the soil seed bank and aboveground flora was very low implying that the role of soil seed banks is negligible rather dispersal plays an important role in the process of regeneration. These results support the concept that forest plantations can foster the regeneration of native woody species, thereby increasing biological diversity, provided that there are seed sources in the vicinity of the plantations.     

尼加拉瓜废弃农田次生演替后的土壤种子库

定量分析了被废弃4年、9年和14年的农田地上派生的次生林土壤中种子组成和密度,从而检测在次生林演替形成过程中,土壤种子库是否能随着植物种群的集成而集成。分别在废弃了4年、9年和14年的农田地里（15cm×15cm样方、9cm土层深）,掘取了18,37和48份土壤样品。在废弃了4,9和14年的农田地上,分别发现了3,5和9个物种。在这些不同的生命形态中,在9年和14年的迹地上,土壤种子树木占主要成分,分别为60%和33%,而4年废弃迹地主要被非木本植物所占领。三块废弃地里,4年废弃迹地植物种子的总数为327粒,相应可发育的种子密度为141粒/m2,14年废弃迹地种子的总数为46粒,相应的可发育种子的密度为26粒/m^2,指明种子数、种子密度随废弃地龄成下降趋势。在9年和14年龄废弃地上,土壤种子植物种类与立地木本植物种类的相似度较低,而4年龄地上两者比较则完全不同。我们认为：土壤种子库的物种构成是在次生演替过程中逐渐形成的,但是,所获得的总体种子密度太低,仅仅依赖于这些种子来实现树木自然再生是不可靠的。为了加快这些废弃地次生林的恢复,既要依靠自然集成的土壤种子库,还需要通过直播、所需物种的强化种植和设定人工生长环境以利于种子传播。     

缙云山常绿阔叶林种子雨组成及其时空动态

【目的】分析缙云山常绿阔叶林种子雨组成及其时空动态,为常绿阔叶林种子生态学大尺度和长时序的研究提供数据支持,并为受损常绿阔叶林近自然恢复过程中的种源收集和种子撒播提供参考信息。【方法】 2014-01—2016-12,收集缙云山常绿阔叶林1 hm 2标准地中172个种子收集框内的种子,鉴定物种并计数,风干后称质量。根据果实类型及种子特征并结合野外实地观察,确定每个物种种子(果实)的散布方式。【结果】 3年间共收集到成熟种子36 298粒,种子雨密度为140.69粒·m -2 a -1;种子分属于19科21属27种,占群落木本植物物种总数的36.49%;种子雨具有明显的季节动态,在秋季出现高峰,其中有17个物种在干季(1—4和10—12月)成熟并散布,6个物种在湿季(5—9月)成熟并散布,4个物种在干、湿季均有散布;种子雨密度年际变异系数为0.36~1.73,空间变异系数为1.54~15.20。【结论】缙云山种子雨产量在常绿阔叶林中处于较低水平;优势种对群落种子雨产量贡献较大,种子雨物种组成与群落物种组成相似性较低;群落水平种子雨具有明显的季节动态,且存在很大的年际变异和空间变异,反映出亚热带常绿阔叶林种子雨时空动态的典型特征。在区域植被近自然恢复中的种子采集和撒播环节,应当充分参照不同物种的种子雨掉落的时空动态。     

喀斯特区石漠化治理对土壤水分-物理性状的影响--以黔中杠寨小流域为例

【目的】为了更科学系统地评价喀斯特区石漠化综合治理的土壤效应,揭示小流域石漠化综合治理土壤水分-物理性状的演变趋势,为喀斯特地区生态恢复以及石漠化综合治理提供理论基础和技术支持。【方法】以黔中喀斯特区杠寨小流域为例,于2009年、2012年和2018年分别对不同石漠化程度下各工程治理措施、植被类型以及不同土层深度土壤的水分-物理性状进行了长期、持续的动态监测。【结果】不同石漠化程度,土壤水分-物理性状以非石漠化的最佳,潜在石漠化的次之,中度和重度石漠化的居中,轻度石漠化的最差,且非石漠化与轻度石漠化间差异显著;随着石漠化治理年限的增加,流域内土壤容重的变化不明显,但土壤总孔隙度、持水量和渗滤率则均呈增加趋势,土壤质量总体得到了一定提升;土壤水分-物理性状随土层深度的加深基本上呈降低趋势;不同工程治理措施,荒山造林和封山育林土壤水分-物理性状的改善程度较大,而退耕还林的则恢复较慢;不同植被恢复模式,针叶林、针阔混交林和灌木林的土壤水分-物理性状其改善程度均要高于阔叶林和经果林。对区域土壤水分-物理性状的解释程度依次为土层深度(39.10%)>坡度(26.32%)>监测年限(18.05%)>石漠化程度(11.65%)>工程措施(3.20%)>植被类型(1.69%)。【结论】喀斯特区石漠化综合治理要防治结合,因地制宜,综合考虑各影响因素,采取适宜的工程治理措施,最终达到恢复生态的目的。     

大黑山生态修复区典型植物群落物种多样性变化特征分析

以大黑山水土保持生态修复工程示范区为研究区域,运用典型植物群落物种组成和群落物种多样性指数方法,对大黑山水土保持生态修复区典型植物群落物种多样性变化特征进行了研究,结果表明,生态修复区内天然次生林植物群落形成了乔灌草相结合的稳定的植物群落结构。人工林植物群落按生长型可以划为明显的乔木层和草本层2层群落结构类型;典型植物群落物种多样性指数的排序为:蒙古栎+蒙椴植物群落(Ⅱ)>山杏+黄榆植物群落(Ⅰ)>蒙古栎植物群落(Ⅲ)>油松+山杏混交植物群落(Ⅴ)>油松纯林植物群落(Ⅳ)>油松+沙棘混交植物群落(Ⅵ)>油松疏林植物群落(Ⅶ)。天然次生林植物群落的物种多样性要大于人工林植物群落。天然次生林植物群落由于远离人类活动区,长期以来受人为干扰较小,逐渐形成了相对比较发达的草本层植物群落。     

凉风坳亚热带次生常绿阔叶林土壤种子库和种子雨的特征研究

选择四川省沐川县凉风坳亚热带次生常绿阔叶林为研究对象,在2004年5月、2004年12月和2005年5月对其林下土壤种子库、种子雨以及种子天然萌发状况等方面进行系统调查及分析研究。结果显示,种子下落前后土壤种子库储量,变动为643.2～889.2粒.m-2,物种和种子密度多年生草本物种均占优势。天然林土壤种子库Shannon-Wiener指数均在2004年5月最大,2004年12月次之,2005年5月最小;Simpson指数却和Shannon-Wiener指数H＇的变化趋势相反;Pielou均匀度指数在2004年12月有所降低,此后又升高。种子均呈明显垂直分布,其中0～2 cm土层种子数量最多,其次是枯枝落叶层,其数量随着土层加深而降低。土壤种子库年输入活力种子142.3粒.m-2,年输出活力种子268.9粒.m-2,动物取食是造成种子损失的主要原因。对照人工林土壤种子库物种和密度均低于天然林地;种子库与地上植被物种相似性系数,人工林较高,而天然次生常绿阔叶林较低。     

黄山率水流域水陆交错带植被类型及群落特征

研究以黄山市率水流域水陆交错带典型植物群落为对象,沿主河道设置了 33 个样方,采用 法瑞学派调查法记录样方的物种组成和群落结构;并根据离水面距离和土壤基质类型划分了 3 种生境类 型：砾石型河漫滩、粘土型河漫滩以及河岸边坡,进而进行群落类型划分与生态梯度分析。结果表明： 调查区域有维管束植物共计 67 科 124 属 146 种;水陆交错带植被可分成 15 个群落类型,包含 3 个森林 群落、3 个灌丛群落和 9 个草本群落;森林群落均出现在河岸边坡生境类型中,灌从群落多见于粘土型河 漫滩,草本群落主要集中于砾石型河漫滩;非度量多维标度分析表明,存在于上下游之间和水陆之间的 两个生态梯度是影响群落物种组成的重要因素,并且在两个生态梯度中心过渡区,植物群落丰富度达到 最大。     

徐州石灰岩山地不同植被恢复模式对土壤健康的影响

在对徐州石灰岩山地不同植被恢复类型土壤理化性质研究的基础上,综合分析了不同植被恢复类型对土壤健康影响,结果表明：石灰岩山地不同植被恢复模式土壤健康存在明显差异。其中：针阔混交林中土壤物理性质较好,说明混交林在一定程度上改善了土壤物理性质;土壤有机质和各养分含量上层明显高于下层,且各养分含量均以针阔混交林最高,进一步说明混交林在一定程度上改善了土壤化学性质。应用主成分分析方法对3种植被类型林分土壤健康状况综合评价指标主成分得分,针叶林为-8.309,针阔混交林为6.876,阔叶林为1.433。各类型林分土壤健康状况排序为：针阔混交林〉阔叶林〉针叶林,表明针阔混交林能够改善土壤健康状况。建议在徐州石灰岩山地上应以针阔混交林为主要恢复模式,从而提高该地区土壤的健康水平。     

滇西北亚高山地区落叶松-高山栎混交林土壤种子库初步研究

采用随机取样的方法,对滇西北高山地区落叶松-高山栎针阔混交林的土壤种子库进行了研究。结果表明:亚高山地区落叶松-高山栎针阔混交林土壤种子库由分属9科17属的18种植物的种子组成,种子密度343粒/m2,其中75%的种子分布在0~5 cm的土层中。土壤种子库的物种组成与其地上植被物种组成相关不明显,相关系数仅为0.042 6。其树木群落种子雨由云杉、白桦和高山松等5个树种组成,密度为3 520粒/m2,发生时间集中在每年的9~11月。