Impacts of level of utilisation by grazing on an Astrebla (Mitchell grass) grassland in north-western Queensland between 1984 and 2010. 2. Plant species richness and abundance

The occurrence of interstitial species in Astrebla grasslands in Australia are influenced by grazing and seasonal rainfall but the interactions of these two influences are complex. This paper describes three studies aimed at determining and explaining the changes in plant species richness and abundance of the interstitial species in a long-term sheep utilisation experiment in an Astrebla grassland in northern Queensland. In the first study, increasing utilisation increased the frequency of Dactyloctenium radulans (Button grass) and Brachyachne convergens (Downs couch) and reduced that of Streptoglossa adscendens (Mint bush). In the second study, seasonal rainfall variation between 1984 and 2009 resulted in large annual differences in the size of the seed banks of many species, but increasing utilisation consistently reduced the seed bank of species such as Astrebla spp. and S. adscendens and increased that of species such as B. convergens, D. radulans, Amaranthus mitchellii (Boggabri) and Boerhavia sp. (Tar vine). In the third study, the highest species richness occurred at the lightest utilisation because of the presence of a range of palatable forbs, especially legumes. Species richness was reduced as utilisation increased. Species richness in the grazing exclosure was low and similar to that at the heaviest utilisation where there was a reduction in the presence of palatable forb species. The pattern of highest species richness at the lightest grazing treatment was maintained across three sampling times, even with different amounts of seasonal rainfall, but there was a large yearly variation in both the density and frequency of many species. It was concluded that the maintenance of highest species richness at the lightest utilisation was not aligned with other data from this grazing experiment which indicated that the maximum sustainable wool production occurred at moderate utilisation.

Effects of light conditions and plant density on growth and reproductive biology of Cascabela thevetia (L.) Lippold

Cascabela thevetia (L.) Lippold (Apocynaceae) is an invasive woody weed that has formed large infestations at several locations in northern Australia. Understanding the reproductive biology of C. thevetia is vital to its management. This paper reports results of a shade house experiment that determined the effects of light conditions (100% or 30% of natural light) and plant densities (one, two, four or eight plants per plot) on the growth, time to flowering and seed formation, and monthly pod production of two C. thevetia biotypes (peach and yellow). Shaded plants were significantly larger when they reached reproductive maturity than plants grown under natural light. However, plants grown under natural light flowered earlier (268 days compared with 369 days) and produced 488 more pods per pot (a 5-fold increase) over 3 years. The yellow biotype was slightly taller at reproductive maturity but significantly taller and with significantly greater aboveground biomass at the end of the study. Both biotypes flowered at a similar time under natural light and low plant densities but the yellow biotype was quicker to seed (478 versus 498 days), produced significantly more pods (364 versus 203 pods) and more shoot growth (577 g versus 550 g) than the peach biotype over 3 years. Higher densities of C. thevetia tended to significantly reduce the shoot and root growth by 981 g and 714 g per plant across all light conditions and biotypes over 3 years and increase the time taken to flower by 140 days and produce seeds by 184 days. For land managers trying to prevent establishment of C. thevetia or to control seedling regrowth once initial infestations have been treated, this study indicates that young plants have the potential to flower and produce seeds within 268 and 353 days, respectively. However, with plant growth and reproduction most likely to be slower under field conditions, annual surveillance and control activities should be sufficient to find and treat plants before they produce seeds and replenish soil seed banks. The most at-risk part of the landscape may be open areas that receive maximum sunlight, particularly within riparian habitats where plants would consistently have more favourable soil moisture conditions.

The growth, reproduction and survival of 'Cascabela thevetia' seedlings under two levels of canopy cover

The ornamental tree 'Cascabela thevetia', from tropical America, has naturalised and formed large infestations at several locations in northern Australia. Some understanding of its ecology and invasiveness was gleaned from a field experiment undertaken in North Queensland. The experiment quantified the growth, time to seed formation and survival of seedlings of the peach biotype growing under light and dense canopy cover within a riparian habitat. Growth, reproduction and survival of young plants varied. Growth was most rapid for seedlings away from, or on the edge of infestations because they were constrained by parent plants. The findings also suggested that land managers have at least 12 months following control to detect new plants, or regrowth, before plants set seed and replenish soil seed banks.

Predicting the temporal response of seagrass meadows to dredging using Dynamic Bayesian Networks

Predicting temporal responses of ecosystems to disturbances associated with industrial activities is critical for their management and conservation. However, prediction of ecosystem responses is challenging due to the complexity and potential non-linearities stemming from interactions between system components and multiple environmental drivers. Prediction is particularly difficult for marine ecosystems due to their often highly variable and complex natures and large uncertainties surrounding their dynamic responses. Consequently, current management of such systems often rely on expert judgement and/or complex quantitative models that consider only a subset of the relevant ecological processes. Hence there exists an urgent need for the development of whole-of-systems predictive models to support decision and policy makers in managing complex marine systems in the context of industry based disturbances. This paper presents Dynamic Bayesian Networks (DBNs) for predicting the temporal response of a marine ecosystem to anthropogenic disturbances. The DBN provides a visual representation of the problem domain in terms of factors (parts of the ecosystem) and their relationships. These relationships are quantified via Conditional Probability Tables (CPTs), which estimate the variability and uncertainty in the distribution of each factor. The combination of qualitative visual and quantitative elements in a DBN facilitates the integration of a wide array of data, published and expert knowledge and other models. Such multiple sources are often essential as one single source of information is rarely sufficient to cover the diverse range of factors relevant to a management task. Here, a DBN model is developed for tropical, annual Halophila and temperate, persistent Amphibolis seagrass meadows to inform dredging management and help meet environmental guidelines. Specifically, the impacts of capital (e.g. new port development) and maintenance (e.g. maintaining channel depths in established ports) dredging is evaluated with respect to the risk of permanent loss, defined as no recovery within 5 years (Environmental Protection Agency guidelines). The model is developed using expert knowledge, existing literature, statistical models of environmental light, and experimental data. The model is then demonstrated in a case study through the analysis of a variety of dredging, environmental and seagrass ecosystem recovery scenarios. In spatial zones significantly affected by dredging, such as the zone of moderate impact, shoot density has a very high probability of being driven to zero by capital dredging due to the duration of such dredging. Here, fast growing Halophila species can recover, however, the probability of recovery depends on the presence of seed banks. On the other hand, slow growing Amphibolis meadows have a high probability of suffering permanent loss. However, in the maintenance dredging scenario, due to the shorter duration of dredging, Amphibolis is better able to resist the impacts of dredging. For both types of seagrass meadows, the probability of loss was strongly dependent on the biological and ecological status of the meadow, as well as environmental conditions post-dredging. The ability to predict the ecosystem response under cumulative, non-linear interactions across a complex ecosystem highlights the utility of DBNs for decision support and environmental management.

Use of Sediment Bioassays to Verify Efficacy of Caulerpa taxifolia Eradication Treatments

Infestations of the marine macrophytic alga Caulerpa taxifolia were discovered in Agua Hedionda Lagoon, California in 2000. Rapid response actions included containment under pvc tarps coupled with injection of liquid sodium hypochlorite. To assess the efficacy of these treatments, replicated sediment cores were removed from representative treated sites and transferred to grow-out facilities. Similar cores from uninfested (control) sediments were removed, inoculated with viable explants of C. taxifolia and placed in grow-out facilities. Results from two sampling periods (1 year, 2 years post-treatment) showed that no viable C. taxifolia emerged in cores, and that inoculated “control” sediments supported normal growth. Eelgrass ( Zostera marina L.) seedlings emerged from native seed-banks in “treated” cores, which also supported growth of some invertebrates (annelid worms and hydroids). This study provided essential verification of C. taxifolia eradication efforts, and demonstrates the feasibility of incorporating quality control/quality assurance components in rapid response actions. Results of this study also suggest that seeds of eelgrass are viable for at least two years. (PDF has 9 pages.)

放牧对内蒙古草原群落和土壤种子库的影响及两者关系的研究

选取内蒙古草原三种主要草原类型（草甸草原、典型草原和荒漠草原）代表性群落羊草杂类草群落、羊草群落和大针茅群落、小针茅群落，应用样线法沿水分梯度研究放牧对内蒙古草原不同植物群落功能群组成、多样性、生产力以及多样性与生产力关系的影响和放牧对土壤种子库组成、大小以及多样性的影响，在此基础上，研究土壤种子库与地上植被间的关系。主要结论如下： 1 放牧对植物群落的影响 荒漠草原的放牧演替规律为小针茅群落→猪毛菜 + 小针茅群落→猪毛菜群落;典型草原为羊草或大针茅群落→糙隐子草 + 大针茅群落或克氏针茅群落→星毛委陵菜 + 糙隐子草群落;草甸草原为羊草杂类草群落→羊草 + 贝加尔针茅群落，这是不同物种对牧压的不同适应结果造成的。 放牧使4种草原群落生活型功能群组分间发生强烈的生态替代作用，但不同的群落生态替代模式不同：放牧使小针茅群落多年生丛生禾草作用减弱，一二年生草本作用增强;羊草群落和大针茅群落多年生丛生禾草、多年生根茎禾草作用减弱，多年生杂类草作用增强;羊草杂类草群落多年生根茎禾草作用减弱，多年生丛生禾草作用增强。放牧使非旱生和C3植物作用减弱，而旱生、C4植物作用增强。 放牧对4种群落物种和功能群多样性的影响随不同的群落而表现不同：物种丰富度、物种多样性、生活型多样性 和水分生态类型多样性除羊草杂类草群落外随放牧强度的加大而降低，但适度放牧增加了羊草杂类草群落的上述多样性指标。 群落地上现存量一般随放牧强度的增大而下降，但小针茅群落反之，主要与一年生植物猪毛菜的生物量迅速增加有关。除羊草群落外，0~10 cm 地下生物量随放牧强度的变化不显著;除大针茅群落外，放牧显著降低0~30 cm 地下生物量。 放牧影响下内蒙古草原植物群落生物量随水分生态类型多样性的升高而升高，其回归方程为：Y = 809 + 774x （R2=0.84, P<0.001），其中Y代表群落地上现存量和地下生物量之和，x代表群落水分生态类型多样性。 2 放牧对土壤种子库的影响 小针茅群落、大针茅群落、羊草群落和羊草杂类草群落土壤种子库组成中均以多年生杂类草为主，分别占各自群落种子库总物种数的40%、52%、54%和67%。 生活型功能群种子库密度除羊草杂类草群落外，均以一二年生草本占优势。中度放牧升高了除小针茅群落外多年生禾草种子库密度;放牧增大了小针茅群落和羊草杂类草群落一二年生草本种子库密度;除羊草杂类草群落外，放牧对多年生杂类草种子库密度影响不大;总种子库组成中，灌木半灌木和小半灌木种子库密度不大，不随取样时间和牧压而变化。 中度放牧种子库总密度最大，小针茅群落在重度放牧最大，主要是由于猪毛菜种子库密度在重度放牧突增所致。总体上，内蒙古草原4种群落在不同取样时间不同牧压下种子库总密度波动在20.8~3819.2粒/m2。 土壤种子库物种丰富度最大值一般出现在10月份，除羊草杂类草群落外，不放牧群落较放牧群落为高，中度放牧使羊草杂类草群落土壤种子库物种丰富度增加。中度放牧增加了小针茅群落、大针茅群落7月份和羊草杂类草群落各取样时间土壤种子库物种多样性。 3 地上植被与土壤种子库的关系 土壤种子库的优势种在特定时间特定放牧强度下与地上现有植被优势种一致，但一致率仅为三次取样时间不同放牧强度下总体的23.3%。 地上植被与土壤种子库物种组成相似性指数受不同取样时间的影响，一般的10月取样最大。不同放牧强度对二者间的相似性亦有影响，中度放牧提高了小针茅群落、羊草杂类草群落各取样时间和大针茅群落、羊草群落4月份的相似性指数。隔年二次萌发法提高了二者间的相似性水平。总体上相似性指数变动在0.1~0.75之间。 地上植被现存量、总密度与各取样时间土壤种子库总密度之间不存在显著的相关性。 4 对于估计土壤种子库密度、物种组成和确定种子库与地上植被间的关系，隔年二次萌发法对于弥补直接萌发法本身所具有的不足不失为一种有益的尝试。

紫茎泽兰种子库及幼苗动态特征

紫茎泽兰（Eupatorium adenophorum）是臭名昭著的世界性恶草之一，目前已对全世界30多个国家和地区造成入侵危害，大约在20世纪30年代入侵我国，在我国西南地区造成了严重的危害。本文以四川省攀枝花市遭受紫茎泽兰入侵危害严重的生态系统为研究对象，分别对不同生境下的紫茎泽兰土壤种子库进行调查，以探究紫茎泽兰土壤种子库的结构，并分析人类干扰对土壤种子库结构的影响。并在种子库调查的基础上设计了两项盆栽实验，研究紫茎泽兰土壤种子库的结构的改变导致的紫茎泽兰种子环境因子的改变，从而影响紫茎泽兰种子的萌发、幼苗的命运，以期阐明人类干扰对紫茎泽兰入侵的影响。另外连续测定紫茎泽兰早期生长的生物量，研究紫茎泽兰生物量增长、分配规律，并与其它几种本地种相比较，说明紫茎泽兰能够入侵成功的原因。 在攀枝花紫茎泽兰入侵严重的地区，通过取样研究果园、放牧灌丛以及禁牧灌丛3种不同生境紫茎泽兰土壤种子库特征，发现这3种生境的土壤种子库大小分别为10422粒m-2，3522粒m-2和2889粒m-2 。果园、放牧灌丛和禁牧灌丛等3种干扰程度不同生境的深层种子量占总种子量的比例分别为56.44%，46.96%，24.86%（p=0.006）。从干扰程度上来说，由于果园>放牧灌丛>禁牧灌丛，这一结果表明土壤深层种子量大小与干扰成正比，干扰越大，深层次紫茎泽兰种子量占总种子量的比重越大。由此可以推测，人类的干扰使得紫茎泽兰土壤种子库结构发生了改变，一方面人类干扰导致生境植被覆盖不同，干扰越大，植被覆盖度越小，土壤种子库越大，另一方面人类活动对土壤的直接扰动，使土壤种子库结构发生变化，在放牧灌丛和果园2种生境中，由于人类活动的影响，促使了紫茎泽兰土壤种子库表层种子向下层转移，而且转移量与干扰程度成正相关。由于一定深度埋藏的紫茎泽兰种子萌发的幼苗具有较低的死亡率，进入土壤深层的紫茎泽兰种子越多，紫茎泽兰的长久性土壤种子库就越大，对紫茎泽兰幼苗的补充和定居越有利，入侵也就越难以治理。 初步研究了光照、水分和种子在土壤中的埋藏深度等对紫茎泽兰幼苗的影响，结果发现，1) 播种在0cm、2cm、5cm深度的种子萌发率分别为64.67%、22.67%、13.33%，即种子埋藏越深，萌发率越低，不同层次种子萌发率差异极显著(p=0.00)；幼苗死亡率分别为27.95%、0、0，表层种子萌发的幼苗有较高的死亡率，而由埋藏在深层种子萌发的幼苗没有死亡，土壤表层发芽的幼苗与不同埋藏深度种子萌发的幼苗之间死亡率差异极显著(p=0.00)；2) 在无遮蔽、半遮蔽、全遮蔽3种不同情况下，紫茎泽兰幼苗的死亡率分别为72.15%、30.38%、4.87%，定居率分别为6.66%、33.99%、46.67%，即遮蔽程度越高，死亡率越低，定居率越高，不同处理之间死亡率和定居率差异均极显著（p=0.00）；3) 在浇水、不浇水这2种水分条件下紫茎泽兰的萌发率分别为41.56%、32% (p=0.021)；死亡率分别为35.8%、35.23% (p=0.934)；定居率分别为29.11%、22.66% (p=0.083)，说明水分因子对萌发率的影响显著，对死亡率、定居率的影响不显著。上述结果表明，土壤埋藏深度、光照和水分都是影响紫茎泽兰幼苗萌发的重要因素：一定深度的土壤埋藏能够有效降低紫茎泽兰幼苗的死亡率；光照强度与紫茎泽兰幼苗死亡率成正相关；而水分对紫茎泽兰幼苗的存活影响不显著。 通过跟踪调查紫茎泽兰的早期生长的生物量，发现紫茎泽兰生物量和高度增加迅速,且生物量的增加主要来自地上部分量的增加，而本地灌木却生长缓慢。与本地种相比，紫茎泽兰的根冠比很小，在生殖分配上，紫茎泽兰与本地灌木相比又比较大。另一方面，在生长季到来的时候，紫茎泽兰能够迅速生长，并将大部分生物量分配到地上部分；而在旱季，当许多本地本植物由于枯死、休眠进入休眠状态时，紫茎泽兰却能继续生长，从而确保其在竞争中的空间优势。 综上所述，人类活动的干扰可能导致更多的紫茎泽兰种子进入土壤深层，从而改变了紫茎泽兰土壤种子库的结构；种子萌发后强光直射可能是导致紫茎泽兰幼苗死亡的重要原因；由于土壤深层种子比表层种子具有更强的抵抗强光照射等不良环境因子影响的能力，所萌发的幼苗成活率高，表明其具有更高的繁殖效率。因此可以说是人类活动的干扰不但加剧了紫茎泽兰的入侵，也使得紫茎泽兰入侵后难以根除。

子午岭人工油松林土壤种子库特征研究

采用野外调查取样和室内观测试验相结合的方法,研究了子午岭人工油松林土壤种子库的物种组成、密度、垂直分布等特征。结果表明:(1)土壤种子库储量密度平均为5711粒/m2,最大密度是9537粒/m2,最小密度是3563粒/m2。(2)土壤种子库的种子的垂直分布主要集中在0—2.5cm,2.5—5cm和5—7.5cm这3个层次,占75.38%～79.32%,枯枝落叶层和7.5—10cm层分布较少,占20.68%～24.62%。(3)土壤种子库物种组成主要为灌木和草本两个种类,无乔木植物,多年生草本在物种数和种子数上占据明显优势。

黄土丘陵沟壑区退耕地土壤种子库特征与季节动态

采用野外样线取样与室内萌发相结合的方法研究了黄土高原丘陵沟壑区退耕地种子库的组成、密度、分布特征、季节动态、种子库类型。结果表明,土壤种子库中共发现50种植物的种子,隶属15个科,39个属,主要物种组成与密度季节间差异不显著;在演替过程中土壤种子库的物种数量与密度随退耕年限的增加表现出:增加-减少-增加的趋势,同时阳坡种子库密度波动较阴坡剧烈;土壤种子库密度年内变化范围为1 067~14 717粒/m2,土壤种子库平均密度是夏季>秋季>春季;研究区域退耕地土壤种子库类型属于以猪毛蒿为优势种,并具有其他一年生、多年生草本植物与灌丛种子的没有显著的季节动态的持久种子库,是物种适应黄土丘陵沟壑区特有生态环境条件的繁殖更新策略;从土壤种子库的物种组成、密度、类型来看,黄土丘陵沟壑区退耕地具有一定的自然恢复潜力。

六盘山森林土壤种子库与植被演替过程

以六盘山森林植被为研究对象,通过20多年的森林土壤种子库变化与植被演替过程的试验研究,分析了8种森林群落类型的不同生长年限、生长坡位、枯枝落叶层和土壤深度对土壤种子库形成过程的影响。结果表明:六盘山森林群落不同生长坡位,土壤种子库的储量坡中部>坡下部>坡上部;不同层次土壤种子库,枯枝落叶层远高于0-15 cm深土层,8种森林群落类型排序为华北落叶松林>油松林>华山松林>辽东栎林>山杨林>白桦林>灌丛>草地;土壤种子库储量高峰期,不同群落有显著差异,华山松林和油松林在林龄的30~40年,华北落叶松林在20年,辽东栎林、山杨林、白桦林在15~20年,灌丛和草地在10~20年,其森林群落生长年限与土壤种子库储量变化趋势呈拟合曲线,符合指数方程,相关性极为显著;土壤种子库物种组成丰富,草本和灌木植物远高于乔木树种,乔木树种仅有3~5种,但多数为外来入侵种,而在每一类型中出现频率最高的草地植物多为蒿类,灌木植物为柔毛绣线菊和沙棘,乔木为辽东栎树种。因此,在六盘山林区植被自然更新与合理演替的驱动种和先锋种草地植物为蒿类,灌木植物为柔毛绣线菊和沙棘,乔木为辽东栎,其次是华北落叶松、油松和华山松。

黄土高原草地封育与放牧条件下土壤种子库特征

对半干旱区黄土高原草地在封育和放牧条件下土壤种子库种子密度、种子库组成、种子库物种多样性及均匀性进行了比较研究,并得出主要结论:1)封育提高土壤种子库的植物种类和密度,使优良禾草和多年生植物增加。2)种子库的垂直分布规律是随着土层的加深,种子在数量上递减的速度较快。3)坡向和坡位对土壤种子库有较大影响,种子库密度变化趋势是阴坡>阳坡;坡下部>坡中部>坡上部。4)从丰富度、Shannon-Wiener多样性和均匀性3个方面比较分析封育和放牧样地土壤种子库多样性,得出封育样地Margalef丰富度指数和Shannon-Wiener指数都高于放牧地,Pielou均匀性指数低于放牧地。

川西亚高山云杉人工林天然更新与生境异质性研究

川西亚高山针叶林是四川森林的主体，是长江上游重要的生态屏障。云杉作为亚高山针叶林人工更新的主要树种，已经在该地区形成了大面积的人工纯林。目前，许多云杉人工林分已经进入更新成熟龄，而这些人工林的持续更新却成为日益凸现的问题。探讨这些云杉人工林的自我更新潜力及云杉种子种群更新特点，可为培育后续森林资源提供科学依据。 本文以川西米亚罗亚高山60a云杉人工林为研究对象，并以该区域内相对稳定的植被群落——天然林为对照，采用种子收集器、土壤种子库筛选、室内外种子萌发实验及野外幼苗调查等方法，从异质性微生境的角度研究了种子雨下落之后，不同微生境对种子库、种子萌发、幼苗建立及分布这一前期更新过程的影响，得出如下结果： 1、通过对川西亚高山60a云杉人工林和天然林6年内种子雨雨量、形态特征、散步动态等的持续观测和综合比较可以发现，云杉林结实特点由于林木自身的特征存在着巨大的变动，2002年和2006年两个种子结实大年内，60a人工林种子雨强度分别达到1088.2 ± 52.3粒/m2和704.3 ± 48.9粒/m2，远大于天然林579.9 ± 28.9粒/m2 和507.5± 30.7粒/m2；且云杉林结实质量优于天然林。60a人工林结实量大，种子质量也最好，相对天然林来说对种群的天然更新以及群落的演替都有最大的贡献潜力。应该说，在川西亚高山云杉人工林的天然更新过程中，种源不是影响天然更新的因素。在种子结实大年里，达到更新成熟的云杉人工林有着优于该地区相对稳定植被群落——天然林的种源优势。至少在种子结实大年，种子供应不是该区域人工林天然更新的限制因子。 2、相对于天然林种子库，人工林种子库在种子萌发前能够有较多的有活力种子。虽然这其中有种子雨输入量有差别的因素存在，但两种林分种子库对种子的保存率的不同才是造成这种差异的主要因素。在人工林中，不同地被类型形成的微生境显著地影响了种子库中种子的密度、垂直分布。有地被物存在的微生境能够将种子雨的大部分截留在地被层中，成为幼苗出现的主要场所；同时不同的地被物对种子的保存情况存在显著的差异，苔藓和凋落物层能都较好地保持其中的种子，到种子萌发前，这两种种子库类型能分别为天然更新提供366.1粒/m2和302粒/m2的有效种子。从这点来看，林下地被物上的种子库能够为天然更新萌发阶段提供数量可观的物质基础。 3、种子的萌发和幼苗的定居是天然更新过程中种子库向幼苗库转化的关键环节。总的说来，米亚罗人工林区60a云杉人工林种子向幼苗的转化率十分低下，凋落物、苔藓、草本、裸地四种主要地被物以及天然林内种子/幼苗的转化率分别仅为2.22%、2.14%、0.57%、0.67%、1.05%。这种低的转化率成为云杉林天然更新的限制性因子。但在现有更新条件下，微生境对这一环节仍然显示出十分显著的影响，表现为凋落物和苔藓对现有更新的新幼苗的保存率高于其它类型及天然林。苔藓和凋落物在种子萌发，幼苗保存，以及幼苗分布上都要优于其它地被物类型；另外，微地形对天然更新过程的影响也很显著，凹立地上更适宜于种子的汇集、萌发和定居。 Subalpine coniferous forests dominate most parts of the forested areas in western Sichuan, and they are important ecological barriers in the upper reaches of the Yangtze River. Picea asperata is one of the keystone spruce species for re-afforestation after felling of the natural forests and there have been a total of ca. 13 000 ha of plantations dominate by this species established. Nowadays, many P. asperata plantations have reached reproductive maturity. However, continued regeneration becomes to an important problem in these plantations. Understanding their self-regeneration potential and the regeneration characteristics of seed populations in spruce plantations of these plantations can have some insights on the management of these plantations and the establishment of following forest resources. A subalpine 60a P. asperata plantation distributed in Miyaluo artificial forest area was studied in this paper, at the same time. Synchronously, a 150a natural spruce forest was studied as comparison. Using seed collecting traps, sieving method for soil seed bank, seed germination experiments and seedling investigations in the field, the effects of heterogeneous microsites on early natural regeneration processes after seed rain were studied, which included seed banks, seed germination, seedling establishment and distribution. The main results are as follows. 1. Through a 6-year long term investigation of seed rain intensities, characteristic, dispersal dynamics of 60a P. asperata plantation, we could concluded that the seed setting properties of 60a P. asperata plantation have a great variation for the characteristics trees. In the mast seed year of 2002 and 2006, the seed rain intensities of plantation was 1088.2 ± 52.3 seeds/m2 and 704.3 ± 48.9 seeds/m2 respectively, which were much greater than that of natural spruce forest (579.9 ± 28.9 seeds/m2 in 2002, and 507.5± 30.7 seeds/m2 in 2006). Furthermore, the quality of seed rain in P. asperata plantation was better than that of natural spruce forest. Contrasting with natural spruce forest, 60a P. asperata plantation has a greater potential on natural regeneration of P. asperata population and succession of community for the reason of greater seed rain intensities and better seed quality. We can confirm that seed source was not a limiting factor which influences the natural regeneration progress of P. asperata population distributed in subalpine mountain zone, at least in the mast seed year. 2. Contrasting with natural spruce forest, P. asperata population had more viable seeds in seed bank before the germination. Although the difference of seed rain intensities of two forests has effect on this phenomenon, the difference of seed conservation ability in two forests was the main factor. In the P. asperata plantation, the seed densities and seed vertical distribution pattern were significant effected by the microsites, which posed by different ground cover types. In other word, Microsite with ground covers can obstruct most seeds and keep them in ground cover layer from seed rain, and these ground covers would be the main site for seed occurrence. There was a significant difference about seeds conservation ability among these ground covers. Litter and moss could better conserve P. asperata seeds which distributed in this two covers. Seed banks exist in litter and moss ground cover types could respectively provide 302seed/m2 and 366.1seed/m2 for natural regeneration before the seed germination. From this point of view, we could conclude that ground covers can ensure considerable numbers of seeds for the germination process. 3. Seed germination and seed establishment are key steps that the seeds invert to seedlings in natural generation process. In sum, the seed/seeding transform rate in 60a P. asperata plantation distributed in Miyaluo artificial forest area is very low. the seed/seeding transform rates in litter, moss, herb, soil surface and natural spruce forest were 2.22%、2.14%、0.57%、0.67%、1.05%, respectively. The low transform rate become to a limiting factor of P. asperata natural regeneration process. However, under the existing conditions of natural regeneration, microsit still had significant effect on this transform. The states of Seed germination, new seedling conservation, and older seedling distribution in litter and moss were better than in any other ground cover type or natural spruce forest. In addition, the micro-relief has significant effect on natural regeneration process. Concave site was more suitable for seed collection, seed germination and seedling distribution.

岷江上游高山林线附近优势树种土壤种子库和幼苗更新特征的研究

岷江上游地区高山/亚高山植被分布的坡向性分异显著，阴阳坡高山林线不仅物种组成差异明显，并且分布海拔呈现出阴坡高阳坡低的格局．阳坡林线树种主要是圆柏属乔木，林线类型多为渐变型，海拔高度大约在3 400m~3 800m；阴坡林线树种主要是冷杉，林线类型多为骤变型，海拔高度约在3 800m~4 400m．本研究采用土壤种子库物理筛选、室内萌发实验及野外群落调查等方法，对岷江上游地区阴坡岷江冷杉和阳坡祁连圆柏两类林线树种不同海拔梯度上土壤种子库以及幼苗库特征进行了调查，从土壤种子库和幼苗更新特征的角度对林线乔木树种种群更新特征进行了分析，进而对该地区高山林线在阴阳坡分布差异的原因进行了探讨，结果显示： 1．土壤种子库 阴坡：阴坡高山林线附近岷江冷杉土壤种子的平均密度大约为50.96粒/m2，其中树线以上10m处土壤种子密度为1.00粒/m2，树线处大约19.33粒/m2，林线交错带内土壤种子密度最高为136.83粒/m2，郁闭林内种子密度小于林线交错带，只有30.50粒/m2，种子平均空壳率为52％，霉变率达34%，完好种子只有6%．土壤种子库垂直分布特征为地被物层含种子比重最大，大约在67.50%左右；其次为0~2cm层，约18.84%左右；2~5cm层所占种子比例最小，约13.66%左右．霉变种子数量与土壤深度呈负相关． 阳坡：阳坡祁连圆柏土壤种子的平均密度为60.16粒/m2．树线以上10m处密度为1.92粒/m2，树线位置大约108.16粒/m2，林线交错带内平均为75.80粒/m2，郁闭林内种子密度小于林线交错带，只有20.00粒/m2．种子平均空壳率为36％，完好种子占49%，霉变率较低，大约为10%．阴阳坡林线树种土壤种子库垂直分布特征为：地被物层含种子最多，其次为0~4cm层，4~10cm层所占种子比例最小，霉变种子数量与土壤深度也呈负相关． 2． 幼苗库调查 阳坡：在树线以上区域没有发现幼苗，林线交错带内幼苗密度平均达3 250株/hm2，郁闭林内仅2 750株/ hm2．整个样地内1～2a幼苗很少甚至没有出现，3～10a的幼苗相对较多．空间分布上，祁连圆柏幼苗在林线交错带内接近随机分布，郁闭林内则介于随机分布和均匀分布之间． 阴坡：在树线以上幼苗密度为1 250株/ hm2，全部为1~2a幼苗，林线交错带内幼苗密度平均达7 000株/ hm2，郁闭林内达6 250株/ hm2．林线附近岷江冷杉幼苗丰富度以及幼苗的出现频率明显高于祁连圆柏，年龄结构也较祁连圆柏完整．岷江冷杉幼苗空间分布除了树线处幼苗的分布为随机分布，其他海拔则为集群分布． 3．从不同土壤深度的种子总量和幼苗数量的相关性检验发现，当年生幼苗数量跟表层种子总量相关性极显著, 但是两年生幼苗的数量与底层种子数量相关性显著．土壤种子在土壤中的垂直分布格局从一定程度上可以反映种子库的年际特征．岷江冷杉土壤种子库较丰富，种子散布后的存活力随着时间的变化逐渐下降，属于季节性瞬时种子库；祁连圆柏土壤种子散布格局为集群型分布，成熟种子大部分散布在母株冠幅内，属于永久性土壤种子库． 4．在阴坡林线交错带及以上区域还存在较为丰富的乔木土壤种子，并且在树线以上区域还发现了少量的岷江冷杉幼苗．从样地乔木的年龄结构发现，在林线交错带内上部到树线位置主要以幼龄林为主，且年龄结构完整，基本符合入侵性林线特征；阳坡林线交错带内幼苗出现频率很低，树线以上区域虽然存在种子库，但是没有幼苗出现，在林线交错带内乔木径级差距很大，年龄结构异常不完整，这种特征的林线将会面临两个可能结果：一种是维持现有状态，保持平衡；另外一种就是退化，但阳坡林线的实际动态趋势还有待长期定点研究． Treelines on the upper region of Minjiang River differ between the north aspect and the south aspect in their appearances, altitudes and tree species. On the north aspect, trees of Abies form a sharp and abrupt treeline ranging from 3800m to 4400m, while on the south the treeline is generally lower(3 400~3 800m), more open and gradual and mostly composed of Sabina. In this study, we examined the altitudinal gradients of soil seed banks and seedling recruitments at the treeline ecotones of a N-aspect and a S-aspect by using soil sieving, germination experiment and field investigations, analyzed the characteristics of population regeneration of tree species at the transitional zone and presented a analysis of the causes to the aspect-related difference in treeline patterns in the study area. Major results of our study include: 1． Soil seed bank N-aspect: Of the 50 plots investigated, the average density of soil seeds is 50.96/m2, in which well-formed seeds account for 6%, empty seeds 52%, parasitized seeds34%, and seeds damaged by animals 8%. The size of soil seed bank varies along altitude, being 1.00 seeds /m2 at the 10m above the treeline and ca.19.33 seeds/m2 at the upper limit of treeline. The highest density (136.83 seeds/m2) occurs at the treeline ecotone. By contrast, the density of soil seed for the closed forest is only 30.50 seeds/m2. In terms of vertical strata, 67.50% of the total seeds are at the surface layer, 18.84% at the middle layer (0~2cm) and 13.66% at deeper layer (2~5cm). The number of parasitized seeds is negatively correlated to soil depth. S-aspect: Of the 50 plots investigated, the average density of soil seeds is 60.16 seeds/m2, and the well-formed seeds account for 49%, empty seeds 36%, parasitized seeds10%, and seeds damaged by animals 1%. The size of soil seed bank varies along altitude, with 1.92 seeds/m2 recorded at the10m above the treeline，108.16 seeds/m2 at the upper limit of treeline, and 75.80 seeds/m2 at the treeline ecotone, while that for the closed forest is 20.00 seeds/m2. The number of seeds decreases with the depth of soil. As is on the N-aspect, the size of soil bank, from large to small, follows the order of the surface layer, the middle layer (0~4cm) and the bottom layer (4~10cm). The number of parasitized seeds is also negatively correlated to the depth of the soil. 2． Seedling bank N-aspect: A mean maximum seedling abundance of 31 000 seedlings/hm2 was recorded near alpine treeline at growing season. The density of seedlings is 1 250 seedlings/ha (all being 1 or 2 years old) at the alpine meadow 10m away above treeline, 7 000 seedlings/ha at treeline ecotone and 6 250 seedlings/ha for closed forest．The spatial distribution of Abies faxoniana seedlings is random at the upper limit of the treeline but clumped at other altitudes． S-aspect: No seedlings were found at the alpine meadow 10m away from the treeline. The density of seedlings was 3 250 seedlings/ha at treeline ecotone and 2 750 seedlings/ha for the closed forest．Hardly any 1 year current and 2 year-old seedlings appeared at the plots. The spatial distribution of Sabina przewalskii seedlings is random at treeline ecotone and between “random” and “even” forest closed forest． 3．Correlation tests of seedling population and seed bank at different soil layers indicated that the emergents were strongly correlated to seed bank at surface layer while the number of two-year seedlings was significantly correlated to the seed bank at the bottom of soil layer, indicating that germination mainly occurs at the soil surface while the middle or bottom layer was the reserve for non-germination or dead seeds. It can thus be postulated that Abies faxoniana soil seed bank is of seasonal transient type. By contrast, the soil seed bank of Sabina przewalskii is of persistent type and the soil seeds and seedlings of this species occurred more frequently near the islands of adult trees. 4．A good many soil seeds of both tree species were found near the treeline ecotone and above at N- and S-aspects. A few young seedlings were found above the Abies treeline. Investigation of five altitudinal transects respectively on N- and S-aspects indicated that Abies faxoniana has a more complete age structure than the stands of Sabina przewalskii. The age of firs decreased from closed forest to the upper limit of treeline, which suggests that the Abies treeline is advancing to higher altitude. While on the south aspect, only few Sabina przewalskii soil seeds and nearly no seedlings were found above the treeline ecotone. The stands exhibit extremely great difference in diameter classes with significantly incomplete age structure. This would lead to two possible results for the treelines: maintaining an equilibrium state at the current position or degenerating. But more studies should be carried out at longer time scales or larger spatial scales to understand whether the Sabina treeline is degenerating.

岷江干旱河谷三种蔷薇植物繁殖更新研究

繁殖更新是植物生活史的重要阶段，在退化生态系统中，植物繁殖更新能力往往较差，是植被恢复的限制环节，因而也成为恢复研究重点和核心。本研究选择岷江干旱河谷广泛分布的三种蔷薇：多苞蔷薇（R. multibracteata）、黄蔷薇（R. hugonis）和川滇蔷薇（R. soulieana）为研究对象，通过野外调查，在查明其生长、繁殖更新状况的基础上，采用控制和模拟实验，对种子和幼苗阶段进行了深入研究，综合分析更新潜力，并提出相对应的促进更新和植被恢复措施。主要结论如下： 1）三种蔷薇在岷江干旱河谷广泛分布，生长和繁殖状况良好，结实量大。各生长指标：株高、基径和冠幅，繁殖指标：结实数量、重量和单果重量都具有显著的空间差异性。基径对多苞蔷薇结实量影响最大；而冠幅对黄蔷薇结实量影响最大。海拔和纬度是对蔷薇生长和繁殖影响最大的环境因素，随着海拔和纬度的升高，植株生长更高大，结实量增加；坡度和坡向对其生长和繁殖也有一定影响，随着坡度 和坡向增加，蔷薇生长和结实受到抑制。 2）三种蔷薇在岷江干旱河谷更新现状不佳, 但更新潜力大。活力种子比率低，动物取食以及两年生幼苗的大量死亡是蔷薇更新的主要限制因素。多苞蔷薇和黄蔷薇的结实率低，川滇蔷薇较高。三种蔷薇种子产量大，但种子质量较差，更新具有充足的种源。三种蔷薇都能形成持久种子库，种子库中种子总量大，但有效种子少，黄蔷薇被动物啃食的比例很高，多苞蔷薇和川滇蔷薇也有一部分种子受到动物破坏。三种蔷薇幼苗库组成特征表现为，当年生幼苗所占比例很高，年龄较大幼苗所占比例小。 3）三种蔷薇都具有不同程度休眠，未经处理种子的发芽率极低。黄蔷薇休眠程度最深，为深度生理休眠；多苞蔷薇为中度生理休眠；川滇蔷薇为非深度生理休眠。三种蔷薇种子在形态上发育成熟，种皮具有透水性。蔷薇果果肉和瘦果中含有抑制物质，其浸泡液抑制了油菜种子萌发，果肉抑制作用更强，果肉和瘦果浸泡液的抑制程度分别为：川滇蔷薇>黄蔷薇>多苞蔷薇。切割和硫酸腐蚀提高了川滇蔷薇种子的发芽能力，而对多苞蔷薇和黄蔷薇没有影响。完全去除瘦果果皮和种皮提高了多苞蔷薇种子发芽率，但对黄蔷薇没有影响。赤霉素和烟水对蔷薇种子萌发没有促进作用。三种蔷薇打破休眠所需低温层积时间分别为：黄蔷薇>多苞蔷薇>川滇蔷薇。对于多苞蔷薇和川滇蔷薇，层积前对种子进行硫酸腐蚀或暖温层积能缩短低温层积时间，提高发芽率。对于多苞蔷薇，变温层积中暖温层积和低温层积具有一定的负补性，即延长暖温层积可以缩短种子萌发对低温层积的需要。 4）多苞蔷薇种子形态特征和种子休眠与萌发在不同海拔梯度间存在较大差异。种子采集时间、采集季节和干藏影响多苞蔷薇和川滇蔷薇的种子休眠。多苞蔷薇果实大小、种子大小和千粒重、种皮厚度随海拔升高而增加，而种子饱满率和活力随海拔升高而降低，种子休眠程度也随海拔升高而增加。种皮厚度与种子大小、千粒重成正相关关系，硫酸腐蚀后的种子经过不同时间的低温层积后，种子发芽率与种皮厚度、种子大小、千粒重、海拔成正相关关系。2006 年采集川滇蔷薇和多苞蔷薇种子休眠程度较2005 年低。种子休眠随种子年龄增加而减弱。高温和干旱能减轻多苞蔷薇和川滇蔷薇种子休眠。 5）三种蔷薇的生长和生物量积累在干旱胁迫条件下受到抑制，而生物量分配、叶片形态特征和水分利用特征等都发生了变化。三种蔷薇的根、茎、叶各器官生物量以及总生物量等在干旱胁迫下明显减小，叶片脱落数量增加。在干旱胁迫条件下，较多的生物量分配到地下部分，从而这使R/S 明显增加。比叶面积（SLA）和冠层面积比（LAR）对干旱胁迫的反应不敏感，仅有部分物种在干旱胁迫条件下发生了变化，并且其变化特点在不同年龄幼苗之间有一定差异。干旱胁迫对WUE 的影响在不同物种间存在差异。多苞蔷薇和黄蔷薇的WUE 随着干旱胁迫的增加而增大， 而川滇蔷薇的WUE 则随干旱胁迫增加而减小。在干旱胁迫条件下，多苞蔷薇和黄蔷薇叶片脱落量和生物量减小幅度较川滇蔷薇大，表明其抗旱能力较强。在干旱胁迫条件，三种蔷薇两年生幼苗的生物量减小幅度较当年生幼苗小，表明两年生幼苗的抗旱能力更强。 6）两种植被恢复措施中，幼苗移栽比播种具有更好的植被恢复效果。播种后，蔷薇种子的发芽率较高，但出苗率都很低，即使出苗，幼苗也几乎在一月内全部死亡。 三种微生境条件下（灌木、半灌木和裸地），种子出苗和幼苗成活没有差异。移栽幼苗总体死亡率都比较低，小于20％。特别是两年生幼苗死亡率更低，小于2％。移栽后的幼苗生长状况良好，在整个生长季中，各生长指标不断增加。生境对幼苗的存活率没有显著影响，但对于幼苗的生长和生物量积累有一定影响，裸地更有利于幼苗生长和生物量积累。与当年生幼苗相比，两年生幼苗具有更高的成活率。总之，三种蔷薇在干旱河谷分布广泛、生长繁殖状况良好，结实量大，具有丰富种源，繁殖更新潜力大，但繁殖更新状况不佳；种子散布后动物对种子的取食、种子的深度休眠过程、种子出苗以及当年生幼苗的存活和定居是更新的主要限制环节。水分是影响结实、种子休眠解除和萌发，幼苗存活和定居的最主要的限制因素。在植被恢复中，应在种子成熟季节大量采集种子，在室内打破休眠后进行人工播种，培育两年生幼苗，通过幼苗移栽方式进行植被恢复。川滇蔷薇应栽种在相对湿润的过渡区，而多苞蔷薇和黄蔷薇可以应用于核心区植被恢复。 Regeneration is an important phase in plant life cycle. It has been a key component of ecological restoration in degradation ecosystem in which plants commonly has poor regeneration. In this paper, we investigated the natural growth, propagation and regeneration status of native three rose species, Rosa multibracteata, R. hugonis and R. soulieana, and analysis the limitation in seed germination and seedling establishment stages. Advice on facilitating the use of these plants in restoration based on the results has been proposed. The results were as follows: 1) Three rose plants widely distributed in the dry valley of the Minjiang River, and made a good performance in growth and propagation. There were significant spatial differences in each growth parameter, such as ramet height, basal diameter, crown diameter and propagation parameters including hip number of a clump, hip mass of a clump and a hip mass. Basa diameter was the most important growth parameter influencing fruit number for R. multibracteata and crown diameter was for R. hugoni. Altitude and latitude had the greatest effect on the growth and propagation of rose plants among environmental conditions. Each parameter of growth and propagation increased with the increase of altitude and latitude. In addition, the increase of slope and aspect limited the growth and propagation. 2) Three rose plants had poor natural regeneration, but great regeneration potential. Low seed viability, predation and higher mortality of current year old seedlings were the limitation in regeneration. R. multibracteata and R. hugonis had higher fruiting rates than R. souliean. All three plants produced a great number of seeds, while their viability was poor. Three rose plants had persistent seed banks, with high total seed number but very low viable seed density. Predation was most severe in R. hugonis, and it also existed to some degree in R. multibracteata and R. soulieana. The seedling age-structure was characteristic of current-year seedlings predominating and few older seedlings were observed. 3) Three rose seeds were dormant and untreated seeds germinated with very low germination percentages. The rose seeds had morphological mature embryos, and achenes were permeable. Some inhabit substances existed in hips and achenes for the extracts of hips and achenes inhibited germination of Brassica campestris. The inhibition effect of the extracts of three rose hip and achenes was R. soulieana>R. hugonis>R. multibracteata. Mechanical and H2SO4 scarification increased R. soulieana germination but had no effect on germination of R. hugonis and R. multibracteata seeds. Full removal of pericarp and testa improved the germination of R. multibracteata but did not affect R. hugonis germination. GA3 and smoke water had no positive effect on rose seed germination. The periods of cold stratification required to released seed dormancy was R. hugonis > R. soulieana >R. multibracteata. H2SO4 scarification and warm stratification shortened cold stratification to release dormancy for R. soulieana and R. multibracteata. Warm stratification had complementary effect for cold stratification, i.e. the longer warm stratification seeds received, the shorter cold stratification were required to obtain the same germination percentage. Three rose seeds had different kinds of dormancy; R. hugonis has deep physiological dormancy, R. multibracteata with intermediate physiological dormancy and R. souliean non-deep physiological dormancy. 4）The seeds traits and dormancy of R. multibracteata showed significant difference across altitudes. Year and season of seed collection had significant effect on seed dormancy for both R. souliean and R. multibracteata. Hip size, seed size, seed weight, seed coat thickness and seed dormancy level increased with the increase of the altitude. There were positive relations between seed coat thickness with seed size and seed weight. Germination percentage of seeds treated with H2SO4 scarification following different periods of cold stratification showed positive relation with seed coat thickness, seed size, seed weight and altitude. Seeds of R. souliean and R. multibracteata collected in 2006 had low dormancy level than those collected in 2005. Seed dormancy decreased with increasing seeds age. High temperature and drought were associated with low dormancy level. 5) Seedling growth, the total dry mass and their components of seedlings were reduced, while leaf senescence accelerated under drought stress. More biomass allocation to root system resulted in higher R/S ratio under drought. Water-use efficiency (WUE) of R. multibracteata and R. hugonis increased, while it declined for R. soulieana under drought stress. R. soulieana seedlings had poor drought-resistance capacity it had more senescent leaves, and its reduction of biomass was stronger than two other rose plants under drought. The reduction degree of one year old seedlings under drought stress was slighter than that of current year seedlings. Therefore, one year old seedling was more drought-resistent compared to current year seedlings. 6）Planting seedlings may have better effect in comparison with direct seeding. Most seeds germinated after seeding, but seedling emergence was very low. More than 80 % seedlings from direct seeding died within a months after emergence. Seedling emergence and survival rate did not show difference among microhabitats. Mortality rates of seedlings artificially planted in microhabitats were general lower than 20 %, and the mortality rate of one year old seedlings was lower than 2 %. Each grow parameter including plant height, leaf number and branch number continually increased after planting. Microhabitat type had effect on the growth parameter and biomass production, but it did not influence the seedling survival. Bare land tended to facilitate seedling growth. One year old seedlings had higher survival rate than current year seedlings. In conculsion, the three rose had wide distribution in the dry valley of the Minjiang River. They produced many seeds and had tolerance to drought stress to some degree. But they had poor regeneration in habitats may be caused by predation, seed dormancy，and high mortality in current year seedlings. We recommend that rose plants should be utilized in restoration by planting two-year old seedlings in spring. A large quantity of seeds should be collected artificially in autumn, release seed dormancy in room, and then cultivate two-year old seedlings by seeding in particular container. R. soulieana seedling probably be planted in transition area, and R. multibracteata and R. hugonis can be used in core area of the dry valley of the Minjiang River.

Development and Integration of Biocontrol Products in Branched Broomrape (Phelipanche ramosa) management in Tomato

Parasitic weeds of the genera Striga, Orobanche, and Phelipanche pose a severe problem for agriculture because they are difficult to control and are highly destructive to several crops. The present work was carried out during the period October, 2009 to February, 2012 to evaluate the potential of arbuscular mycorrhizal fungi (AMF) to suppress P. ramosa on tomatoes and to investigate the effects of air-dried powder and aqueous extracts from Euphorbia hirta on germination and haustorium initiation in Phelipanche ramosa. The work was divided into three parts: a survey of the indigenous mycorrhizal flora in Sudan, second, laboratory and greenhouse experiments (conducted in Germany and Sudan) to construct a base for the third part, which was a field trial in Sudan. A survey was performed in 2009 in the White Nile state, Sudan to assess AMF spore densities and root colonization in nine fields planted with 13 different important agricultural crops. In addition, an attempt was made to study the relationship between soil physico-chemical properties and AMF spore density, colonization rate, species richness and other diversity indices. The mean percentage of AMF colonization was 34%, ranging from 19-50%. The spore densities (expressed as per 100 g dry soil) retrieved from the rhizosphere of different crops were relatively high, varying from 344 to 1222 with a mean of 798. There was no correlation between spore densities in soil and root colonization percentage. A total of 45 morphologically classifiable species representing ten genera of AMF were detected with no correlation between the number of species found in a soil sample and the spore density. The most abundant genus was Glomus (20 species). The AMF diversity expressed by the Shannon–Weaver index was highest in sorghum (H\= 2.27) and Jews mallow (H\= 2.13) and lowest in alfalfa (H\= 1.4). With respect to crop species, the genera Glomus and Entrophospora were encountered in almost all crops, except for Entrophospora in alfalfa. Kuklospora was found only in sugarcane and sorghum. The genus Ambispora was recovered only in mint and okra, while mint and onion were the only species on which no Acaulospora was found. The hierarchical cluster analysis based on the similarity among AMF communities with respect to crop species overall showed that species compositions were relatively similar with the highest dissimilarity of about 25% separating three of the mango samples and the four sorghum samples from all other samples. Laboratory experiments studied the influence of root and stem exudates of three tomato varieties infected by three different Glomus species on germination of P. ramosa. Root exudates were collected 21or 42 days after transplanting (DAT) and stem exudates 42 DAT and tested for their effects on germination of P. ramosa seeds in vitro. The tomato varieties studied did not have an effect on either mycorrhizal colonization or Phelipanche germination. Germination in response to exudates from 42 day old mycorrhizal plants was significantly reduced in comparison to non-mycorrhizal controls. Germination of P. ramosa in response to root exudates from 21 day old plants was consistently higher than for 42 day-old plants (F=121.6; P<.0001). Stem diffusates from non-mycorrhizal plants invariably elicited higher germination than diffusates from the corresponding mycorrhizal ones and differences were mostly statistically significant. A series of laboratory experiments was undertaken to investigate the effects of aqueous extracts from Euphorbia hirta on germination, radicle elongation, and haustorium initiation in P. ramosa. P. ramosa seeds conditioned in water and subsequently treated with diluted E. hirta extract (10-25% v/v) displayed considerable germination (47-62%). Increasing extract concentration to 50% or more reduced germination in response to the synthetic germination stimulants GR24 and Nijmegen-1 in a concentration dependent manner. P. ramosa germlings treated with diluted Euphorbia extract (10-75 % v/v) displayed haustorium initiation comparable to 2, 5-Dimethoxy-p-benzoquinon (DMBQ) at 20 µM. Euphorbia extract applied during conditioning reduced haustorium initiation in a concentration dependent manner. E. hirta extract or air-dried powder, applied to soil, induced considerable P. ramosa germination. Pot experiments were undertaken in a glasshouse at the University of Kassel, Germany, to investigate the effects of P. ramosa seed bank on tomato growth parameters. Different Phelipanche seed banks were established by mixing the parasite seeds (0 - 32 mg) with the potting medium in each pot. P. ramosa reduced all tomato growth parameters measured and the reduction progressively increased with seed bank. Root and total dry matter accumulation per tomato plant were most affected. P. ramosa emergence, number of tubercles, and tubercle dry weight increased with the seed bank and were, invariably, maximal with the highest seed bank. Another objective was to determine if different AM fungi differ in their effects on the colonization of tomatoes with P. ramosa and the performance of P. ramosa after colonization. Three AMF species viz. GIomus intraradices, Glomus mosseae and Glomus Sprint® were used in this study. For the infection, P. ramosa seeds (8 mg) were mixed with the top 5 cm soil in each pot. No mycorrhizal colonization was detected in un-inoculated control plants. P. ramosa infested, mycorrhiza inoculated tomato plants had significantly lower AMF colonization compared to plants not infested with P. ramosa. Inoculation with G. intraradices, G. mosseae and Glomus Sprint® reduced the number of emerged P. ramosa plants by 29.3, 45.3 and 62.7% and the number of tubercles by 22.2, 42 and 56.8%, respectively. Mycorrhizal root colonization was positively correlated with number of branches and total dry matter of tomatoes. Field experiments on tomato undertaken in 2010/12 were only partially successful because of insect infestations which resulted in the complete destruction of the second run of the experiment. The effects of the inoculation with AMF, the addition of 10 t ha-1 filter mud (FM), an organic residues from sugar processing and 36 or 72 kg N ha-1 on the infestation of tomatoes with P. ramosa were assessed. In un-inoculated control plants, AMF colonization ranged between 13.4 to 22.1% with no significant differences among FM and N treatments. Adding AMF or FM resulted in a significant increase of branching in the tomato plants with no additive effects. Dry weights were slightly increased through FM application when no N was applied and significantly at 36 kg N ha-1. There was no effect of FM on the time until the first Phelipanche emerged while AMF and N application interacted. Especially AMF inoculation resulted in a tendency to delayed P. ramosa emergence. The marketable yield was extremely low due to the strong fruit infestation with insects mainly whitefly Bemisia tabaci and tomato leaf miner (Tuta absoluta). Tomatoes inoculated with varied mycorrhiza species displayed different response to the insect infestation, as G. intraradices significantly reduced the infestation, while G. mosseae elicited higher insect infestation. The results of the present thesis indicate that there may be a potential of developing management strategies for P. ramosa targeting the pre-attachment stage namely germination and haustorial initiation using plant extracts. However, ways of practical use need to be developed. If such treatments can be combined with AMF inoculation also needs to be investigated. Overall, it will require a systematic approach to develop management tools that are easily applicable and affordable to Sudanese farmers. It is well-known that proper agronomical practices such as the design of an optimum crop rotation in cropping systems, reduced tillage, promotion of cover crops, the introduction of multi-microbial inoculants, and maintenance of proper phosphorus levels are advantageous if the mycorrhiza protection method is exploited against Phelipanche ramosa infestation. Without the knowledge about the biology of the parasitic weeds by the farmers and basic preventive measures such as hygiene and seed quality control no control strategy will be successful, however.