Climax Vegetation Research Articles

A high-latitude Gondwanan lagerstätte: The Permian permineralised peat biota of the Prince Charles Mountains, Antarctica

The Toploje Member chert is a Roadian to Wordian autochthonous–parautochthonous silicified peat preserved within the Lambert Graben, East Antarctica. It preserves a remarkable sample of terrestrial life from high-latitude central Gondwana prior to the Capitanian mass extinction event from both mega- and microfossil evidence that includes cryptic components rarely seen in other fossil assemblages. The peat layer is dominated by glossopterid and cordaitalean gymnosperms and contains moderately common herbaceous lycophytes, together with a broad array of dispersed organs of ferns and other gymnosperms. Rare arthropod–plant and fungal–plant interactions are preserved in detail, together with a plethora of fungal morphotypes, Peronosporomycetes, arthropod remains and a diverse coprolite assemblage. Comparisons to other Palaeozoic ecosystems show that the macroflora is of low diversity. The fungal and invertebrate–plant associations demonstrate that a multitude of ecological interactions were well developed by the Middle Permian in high-latitude forest mires that contributed to the dominant coal deposits of the Southern Hemisphere. Quantitative analysis of the constituents of the silicified peat and of macerals within adjacent coal seams reveals that whilst silicified peats provide an unparalleled sample of the organisms forming Permian coals, they do not necessarily reflect the volumetric proportions of constituents within the derived coal. The Toploje Member chert Lagerstätte provides a snapshot of a rapidly entombed mire climax ecosystem in the closing stages of the Palaeozoic, but prior to the onset of the protracted crisis that engulfed and overthrew these ecosystems at the close of the Permian.

围封禁牧对小叶锦鸡儿灌丛化草原群落组成和结构的影响

典型草原向灌丛化草原的转变是过度放牧引起的重要结果之一。为研究内蒙古地区小叶锦鸡儿灌丛化草原对围封禁牧的响应，在内蒙古锡林郭勒典型草原退化区选取小叶锦鸡儿成片分布的典型地段，自2003年，分别设置禁牧样区和放牧样区。于2008-2011年连续四年调查禁牧样区小叶锦鸡儿种群生长和生理生化指标及灌丛间群落基本特征，并将2011年禁牧样区与放牧样区小叶锦鸡儿种群与灌丛间群落进行比较。结果显示：（1）围封后小叶锦鸡儿种群开始衰退，主要体现在种群盖度的降低和叶片氮磷含量（特别是磷含量）有所降低，而个体构件生长状况无显著差异；（2）灌丛间群落的物种组成随围封年限增加发生显著变化：禁牧后1年生植物逐渐退出群落，多年生丛生禾草重要值随围封年限增加而显著增加，即围封禁牧对小叶锦鸡儿灌丛化草原的群落恢复有积极作用；（3）小叶锦鸡儿种群盖度与多年生丛生禾草的重要值显著负相关，说明两者之间存在竞争关系，推测多年生丛生禾草的竞争是禁牧后小叶锦鸡儿衰退的重要原因。;Grassland ecosystem is one of the most important terrestrial ecosystems in the world which may impose an impact upon global environmental change. The dynamics of a grassland ecosystem can be affected by disturbance in terms of promoting community succession and changing community structure. Among the disturbing factors, grazing is considered one of the key factors which affect both above-and below-ground processes in the ecosystem. One of the most prominent consequences of overgrazing is the transformation of grassland to shrub-land. In order to protect grassland ecosystem and restore vegetation productivity, a number of measures have been put into practice, among which fencing an area to exclude livestock is often considered to be a simple but effective way. The aim of the present study was to explore the response of the <em>Caragana microphylla</em>-dominated community to fencing and to predict when the degraded community would restore to its normal status after grazing exclusion. The study site was located in Xilingol degraded grassland of Inner Mongolia, China. Long-time grazing resulted in the expansion of <em>C. microphylla</em> populations in this site, and we set different treatments since 2003. Animals were excluded by fencing in the plot of grazing exclusion (EG), while the grazing intensity was controlled at 3 sheep/hm² in the plot of grazing (G). The two plots were adjacent and had similar environment until 2003. We investigated the growth and physiological traits of <em>C. microphylla</em> and the basic characteristics of the herbaceous communities, and compared the temporal changes in plot EG after 5-8 years of fencing and the spatial differences between these two plots after eight years of different utilization regimes. We analyzed the response of the traits of <em>C. microphylla</em> and the composition of herbaceous community to grazing and fencing, and also the relationship between the cover of <em>C. microphylla </em>and the ‘Importance Value’ of different functional groups. (1) The coverage of <em>C. microphylla</em> decreased in the plot EG during the four years while the morphological traits showed no significant variation, indicating that <em>C. microphylla</em> population declined after grazing exclusion. The decline of <em>C. microphylla </em>reflected a decrease of population coverage instead of the growth status of individual modules. Moreover, leaf nitrogen and phosphorus content, especially the latter, decreased after grazing exclusion, which might be associated with the decline of <em>C. microphylla</em> population. (2) Herbaceous community composition showed significant change after eight years of grazing exclusion. Annuals disappeared from the community, while the Important Value of perennial bunch grasses increased significantly in the plot EG both in temporal and spatial comparison. The change of community structure indicated that grazing exclusion had a positive effect on the restoration of <em>C. microphylla</em>-dominated grassland. (3) The coverage of <em>C. microphylla</em> decreased with the increasing Importance Value of perennial bunch grasses, indicating that there existed a competition between <em>C. microphylla</em> and the perennial bunch grasses. The decline of <em>C. microphylla</em> population might be caused by the expansion of well-grown perennial bunch grasses. It is suggested that grazing exclusion impose an effect on the restoration of <em>C. microphylla</em>-dominated community, but re-establishment of the typical steppe with climax community needs at least eight years; in other words, the restoration of <em>C. microphylla</em>-dominated grassland to its original status is a long-term process.

不同透光环境下红松光合色素含量的季节变动及应对策略

研究了辽东山区天然次生林内3种不同透光环境（强度透光、中度透光和弱度透光）下红松针叶光合色素（叶绿素a（Chl a）、叶绿素b（Chl b）、类胡萝卜素（Car）和叶绿素总量（Chl T））应对光环境季节变动做出的适应性调整。结果表明，随季节的变动（从春季至秋季），林分透光孔隙度逐渐减小。春季，透光度越大，红松叶绿素含量越高，Chl a/b值升高，Car /Chl T值降低；夏季，不同透光条件对红松光合色素含量无影响；秋季，各类透光条件下红松光合色素含量总体表现为升高的趋势，强度透光与中度透光条件红松针叶Chl a/b显著大于弱度透光，3种透光条件下红松Car/Chl T均降低。在春季红松开始生长前进行适当抚育，能提高光合色素含量，增强光合作用能力，促进生长。;Broad-leaved Korean pine forest (BKPF) is one of several zonal climax vegetation types dominated by Korean pine (<em>Pinus koraiensis</em>) in the temperate forest region of Northeast China. Unfortunately, intense human activities and extreme natural disturbances have continuously affected the succession of the BKPFs for the past century. Most of the historic areas of BKPFs have succeeded into secondary forests that are not dominated by Korean pine. As a result, since the 1960s, <em>P. koraiensis</em> seedlings have been planted under the canopy of secondary forests in an effort to restore the BKPFs. The status of the survival and growth of <em>P. koraiensis</em> saplings under the canopy of secondary forests has been considered to be an important indicator demonstrating the success of these efforts. Many reports suggested that light was one of the most important environmental factors affecting the regeneration and growth of <em>P. koraiensis</em>. Generally, <em>P. koraiensis </em>is considered to be both a tolerant and intolerant species, having a dual response to light conditions in forest communities depending on its habitat and age classes. <em>P. koraiensis</em> seedlings are able to survive under closed canopy conditions; canopy openness ranging from 0.5 to 0.6 is optimal for the survival and growth of <em>P. koraiensis</em> seedlings. However, as the saplings grow, they need more and more light and finally become intolerant to shaded conditions. For example, compared with seedlings, slightly more mature trees will grow under a forest canopy with a canopy openness of 0.7 for the long-term, but they grow poorly and eventually die under those conditions over an extended period of time. Selective thinning is almost always carried out when <em>P. koraiensis</em> saplings reach an age of 8 to 10 years. However, the needles of <em>P. koraiensis </em>may turn yellow after the selective thinning indicating that the type and quantity of photosynthetic pigments in needles changes in response to the selective thinning. This study was conducted to analyze the response of the photosynthetic pigments in <em>P. koraiensis</em> needles to selective thinning in an effort to understand the relationships between the light environment and the regeneration of <em>P. koraiensis</em>. The experiments were conducted at Qingyuan Experimental Station of Forest Ecology, Chinese Academy of Sciences, located in Changsha, Qingyuan County, Fushun City, Liaoning Province, China. We compared the content of chlorophyll a (Chl a), chlorophyll b (Chl b), carotenoids (Car), and total chlorophyll (Chl T) in <em>P. koraiensis</em> needles under three light environments: low-, mid- and high light levels in a secondary forest. The results showed that canopy openness decreased from a high-level light to low-level light environment from spring through summer to autumn. In spring, the chlorophyll content and the ratio of Chl a/b increased, but the ratio of Car/Chl T decreased as the light levels changed from a low-level to high-level light environment. However, the Car content did not change significantly during spring. In summer, no significant differences in pigment content were observed among the three light levels, but the pigment content was higher than that in spring for all pigments analyzed here. In autumn, the ratio of Chl a/b was higher in the high-level and mid-level light environments than that in the low-level light environment. The photosynthetic pigment content increased in all three light levels from spring to summer, but the ratio of Car/Chl T decreased significantly during the same time period. In summary, these results suggest that thinning management designed to increase light-transmittance should be conducted in spring and a mid-level thinning intensity is suitable for improving the photosynthetic capability and for accelerating growth of <em>P. koraiensis</em> under the canopy of secondary forests.

Ecological Study of Bryophytes on Platanus orientalis L. Trees in Nainital (Western Himalaya)

The bryophytic vegetation associated with Platanus orientalis trees were studied and compared with other important tree species of Nainital. In total 27 mosses and liverworts belonging to 14 families with three morphological groups formed the principle component of Platanus orientalis tree bark. Based on IVI (Important Value Index), Regmatodon orthostegius together with Brachymenium capitulatum formed the pioneer community, while Herpetineuron toccoae formed the climax community on the Platanus orientalis stems. Comparison of the bryoflora of P. orientalis with other dominant trees of this locality indicated that 15 species were common, while 12 species viz., Didymodon vinealis (Brid.) R.H., Bryoerythrophyllum dentatum (Mitt.) Chen, Gemmabryum apiculatum (Schw?gr.), Ditrichum heteromallum (Hedw.) Britt., Entodon chloropus Ren. & Card., Cylindrothecium laetum (Griff.) Paris, Fabronia schensiana C. Muell., Lejeunea tuberculosa Stephani, Levierella neckeroides (Griff.), Regmatodon orthostegius Mont., Rhynchostegiella menadensis (Lac.) Bartr. and Stereophyllum fulvum (Harv.) Jaeg. were confined to the tree barks of P. orientalis.

江西武夷山——黄岗山西北坡森林繁殖鸟类多样性调查

研究区属于江西武夷山国家级自然保护区范围,为中国亚热带东部最高的山地,森林原生性保存较为完好。2004-2012年,在研究区海拔300-2160 m范围,布设了穿越所有代表性生境的1条主样线和6条辅助样线,共记录有森林繁殖鸟188种,占中国东部丘陵平原亚区繁殖鸟种数的71.76%。在这些繁殖鸟中,物种数在10种及以上的优势科有鸫科(Turdidae)13种、鹟科(Muscicapidae)10种、画眉科(Timaliidae)21种、莺科(Sylviidae)22种,占研究区森林繁殖鸟种数的35.1%、雀形目(PASSERIFORMES)的51.2%。将研究区按海拔高度、植被类型和人类干扰程度分为4类生境进行分析,结果显示:物种数以次生林恢复区最多(138种) > 原生性森林区(127种) > 农林营作干扰区(119种) > 中山灌丛草甸区(51种),其中中山灌丛草甸区由于生境条件因素各项指标数值均最小,其余3类生境分区,无论是总鸟种数、雀形目鸟种数,还是优势科鸟种数,均支持中间膨胀效应(Mid-domain effect)。<em>G-F</em>指数由低海拔向高海拔依次降低,即:农林营作干扰区(<em>D</em><em>_G-F</em> =0.775) > 次生林恢复区(<em>D</em><em>_G-F</em> =0.772) > 原生性森林区(<em>D</em><em>_G-F</em> =0.760) > 中山灌丛草甸区(<em>D</em><em>_G-F</em> =0.603);雀形目鸟种<em>G-F</em>指数分析,原生性森林区(<em>D</em><em>_G-F</em> =0.650)则略大于次生林恢复区(<em>D</em><em>_G-F</em> =0.633),提示顶级植物群落更大的森林内部空间和多样的内部层次结构,对雀形目鸟种多样性具有积极意义。分析显示次生林恢复区与原生性森林区相似性系数最高,表明经过30a左右自然演替恢复的次生林,对于森林繁殖鸟来说其生态功能已接近顶级群落,而农林营作干扰区和中山灌丛草甸区相似性系数最低。同时,研究区鸡形目(GALLIFORMES)鸟类生态位分异表现最为典型。;The research area belongs to Jiangxi Wuyishan National Nature Reserve, it is the highest mountain land in east of China subtropical area, and the original nature of forest is relatively intactly preserved. During 2004-2012, one main line and six auxiliary sample lines were laid across all the typical habitats at the scope of the altitude between 300 and 2160m in the research area, 188 kinds of forest breeding birds have been recorded, occupies 71.76 percent of the species number of forest breeding birds in China's eastern hilly and plain subregion. Among these breeding birds, dominant families with 10 kinds or more species number are: Turdidae 13 kinds, Muscicapidae 10 kinds, Timaliidae 21 kinds, Sylviidae 22 kinds, occupies 35.1 percent of the species number of forest breeding birds in the research area and 51.2 percent of the Passeriformes. The research area was divided into 4 categories of habitat in accordance with altitude, vegetation form and human interference degree and analyzed. The result shows that recovering secondary area have the most species number(138 kinds) > original forest (127 kinds) > production activities interference area (119 kinds) > peak scrub meadow area (51 kinds), among the four areas the numerical value of every index of peak scrub meadow area is the smallest for the habitat condition factors, the remaining three kinds of habitat subareas sustain Mid-domain effect both in overall bird species number, Passeriformes bird species number, and in the bird species number of dominant families. The <em>G-F</em> index reduces as the altitude increases, namely production activities interference area(<em>D</em><em>_G-F</em> =0.775) > recovering secondary area (<em>D</em><em>_G-F</em> =0.772) > original forest (<em>D</em><em>_G-F</em> =0.760) > peak scrub meadow area (<em>D</em><em>_G-F</em> =0.603);in the <em>G-F</em> index analysis of Passeriformes bird species, the <em>G-F</em> index of original forest (<em>D</em><em>_G-F</em> =0.650) is slightly higher than that of the recovering secondary area (<em>D</em><em>_G-F</em>=0.633), which shows that bigger forest inner space and the various interior hierarchical structure of climax community have positive significance for the diversity of Passeriformes birds. Analysis shows that recovering secondary area and original forest area have the highest similarity coefficient, and indicates that the ecological functions of secondary forest after about 30 years natural succession recovery is already approximate to that of the climax community for forest breeding birds,while the similarity coefficient of production activities interference area and peak scrub meadow area is the lowest. Meanwhile, the Birds ecological Niche differentiation manifestation of Galliformes is most typical.

남강댐의 운영수위 변경에 따른 선버들 군락의 분포현황 및 특성

The present Namgang Dam had been completed in 2000, Salix subfragilis communities began to form in 2003 and their distribution area have been rapidly extended into nine times in 2010. In order to deduce correlation between water level and distribution of Salix subfragilis communities under this background in Namgang-dam reservoir, distribution characteristics and widening direction of Salix subfragilis communities have been analyzed by aerial photographs and water levels has been reviewed, also heights and ages of Salix subfragilis have been surveyed in field. The water levels of Namgang-dam related germination of Salix subfragilis have been analyzed in May and June from 2000 to 2010, mean water level, minimum water level and maximum water level were 37.87m, 36.99m and 38.82m, respectively. The oldest ages were 9-13 years, average diameters of breast height, average heights, average numbers and average crown area were respectively 3.9-8.8cm, 3.8-7.5m, and in sites. Therefore, this results showed that the first recruitment of Salix subfragilis was in May 2002 when water levels have been maintained as 38.76-41.31m and the widening of Salix subfragilis communities was in May 2004 and 2005 when mean minimum water levels have been maintained as 38.76-41.31m. Salix subfragilis communities formed climax forest in Namgang-dam shore, this phenomena were different from the succession processes of Salix in rivers appeared landforming by deposition of sediment.

Clinical Insights from Metagenomic Analysis of Sputum Samples from Patients with Cystic Fibrosis

As DNA sequencing becomes faster and cheaper, genomics-based approaches are being explored for their use in personalized diagnoses and treatments. Here, we provide a proof of principle for disease monitoring using personal metagenomic sequencing and traditional clinical microbiology by focusing on three adults with cystic fibrosis (CF). The CF lung is a dynamic environment that hosts a complex ecosystem composed of bacteria, viruses, and fungi that can vary in space and time. Not surprisingly, the microbiome data from the induced sputum samples we collected revealed a significant amount of species diversity not seen in routine clinical laboratory cultures. The relative abundances of several species changed as clinical treatment was altered, enabling the identification of the climax and attack communities that were proposed in an earlier work. All patient microbiomes encoded a diversity of mechanisms to resist antibiotics, consistent with the characteristics of multidrug-resistant microbial communities that are commonly observed in CF patients. The metabolic potentials of these communities differed by the health status and recovery route of each patient. Thus, this pilot study provides an example of how metagenomic data might be used with clinical assessments for the development of treatments tailored to individual patients.

The Fauna from Quiroste: Insights into Indigenous Foodways, Culture, and Land Modification

The CA-SMA-113 archaeofauna suggests that Quiroste Valley people used varied terrestrial and marine foods, generally avoided consuming birds, and maintained more open habitats than typifies the valley's natural climax vegetation. We contextualize habitat-diagnostic rodent taxa from the site with data from a recent live trapping transect only a few kilometers south of Quiroste. California voles, an open country species, were never trapped in closed vegetation but are the second most common identifiable rodent species in the CA-SMA-113 archaeofauna, a divergence that is extremely statistically significant. Based upon the modern live-trapping data, voles should not have been present at all, if Quiroste Valley habitats were unmodified. Their robust presence implies processes favoring grassland maintenance.

Priming of Soil Carbon Decomposition in Two Inner Mongolia Grassland Soils following Sheep Dung Addition: A Study Using 13C Natural Abundance Approach

To investigate the effect of sheep dung on soil carbon (C) sequestration, a 152 days incubation experiment was conducted with soils from two different Inner Mongolian grasslands, i.e. a Leymus chinensis dominated grassland representing the climax community (2.1% organic matter content) and a heavily degraded Artemisia frigida dominated community (1.3% organic matter content). Dung was collected from sheep either fed on L. chinensis (C3 plant with δ13C = −26.8‰; dung δ13C = −26.2‰) or Cleistogenes squarrosa (C4 plant with δ13C = −14.6‰; dung δ13C = −15.7‰). Fresh C3 and C4 sheep dung was mixed with the two grassland soils and incubated under controlled conditions for analysis of 13C-CO2 emissions. Soil samples were taken at days 17, 43, 86, 127 and 152 after sheep dung addition to detect the δ13C signal in soil and dung components. Analysis revealed that 16.9% and 16.6% of the sheep dung C had decomposed, of which 3.5% and 2.8% was sequestrated in the soils of L. chinensis and A. frigida grasslands, respectively, while the remaining decomposed sheep dung was emitted as CO2. The cumulative amounts of C respired from dung treated soils during 152 days were 7–8 times higher than in the un-amended controls. In both grassland soils, ca. 60% of the evolved CO2 originated from the decomposing sheep dung and 40% from the native soil C. Priming effects of soil C decomposition were observed in both soils, i.e. 1.4 g and 1.6 g additional soil C kg−1 dry soil had been emitted as CO2 for the L. chinensis and A. frigida soils, respectively. Hence, the net C losses from L. chinensis and A. frigida soils were 0.6 g and 0.9 g C kg−1 soil, which was 2.6% and 7.0% of the total C in L. chinensis and A. frigida grasslands soils, respectively. Our results suggest that grazing of degraded Inner Mongolian pastures may cause a net soil C loss due to the positive priming effect, thereby accelerating soil deterioration.

Soil biota in post-mining sites along a climatic gradient in the USA: Simple communities in shortgrass prairie recover faster than complex communities in tallgrass prairie and forest

Soil biota were studied at four post-mining areas along a climatic gradient in the USA. The natural climax vegetation was hardwood forest (TN, IN), tallgrass prairie (IL), or shortgrass prairie (WY). Two chronosequences were used in each state, each contained young (2–5 y) and old (15–20 y) post-mining and a site with the area's climax vegetation. All sites were sampled in spring 2008 and 2011. Microbial biomass, microbial respiration, ergosterol, composition of microbial community (using phospholipid fatty acids), community composition of soil nematodes and macrofauna, soil chemistry, and soil microstructure (using thin soil sections) were studied. Total carbon and nitrogen content increased with successional age, while total phosphorus was often greater in young post-mining sites than in climax sites. Microbial biomass in forest chronosequences increased with age, actinobacteria were associated with prairie sites, and fungi were associated with forest sites. Root-feeding nematodes and macroflora were dominant in the shortgrass prairie sites. Earthworms were absent in such shortgrass sites but were present in the wetter, eastern sites. In forest chronosequences, other saprophages, litter transformers, and microphagous groups were also abundant. Absence of saprophagous groups, and especially earthworms, resulted in the absence of bioturbation in shortgrass prairie sites while worm casts and other biogenic structures formed an important part of the soil profile in other chronosequences. Both young and old restoration sites were much closer to the climax condition in shortgrass prairie than in the other sites. The shortgrass prairie soil community contained abundant root-feeding organisms, which may establish quicker than the more saprophagous soil biota that were abundant at the other sites. In chronosequences other than the one in shortgrass prairie, bioturbation played an important role in topsoil formation, which result to complex soil profile development compare to shortgrass prairie which may contribute to faster recovery communities in shortgrass prairie in comparison with tallgrass prairie and forest.

Use of Pollen and Ancient DNA as Conservation Baselines for Offshore Islands in New Zealand

Islands play a key role globally in the conservation of endemic species. Many island reserves have been highly modified since human colonization, and their restoration and management usually occur without knowledge of their prehuman state. However, conservation paleoecology is increasingly being recognized as a tool that can help to inform both restoration and conservation of island reserves by providing prehuman vegetation baselines. Many of New Zealand's mammal-free offshore islands are foci for biological diversity conservation and, like many islands in the Polynesian region, were deforested following initial human settlement. Therefore, their current restoration, replanting, and management are guided either by historic vegetation descriptions or the occurrence of species on forested islands. We analyzed pollen and ancient DNA in soil cores from an offshore island in northern New Zealand. The result was a 2000-year record of vegetation change that began >1200 years before human settlement and spanned 550 years of human occupation and 180 years of forest succession since human occupation ceased. Between prehuman and contemporary forests there was nearly a complete species turnover including the extirpation of a dominant conifer and a palm tree. The podocarp-dominated forests were replaced by a native but novel angiosperm-dominated forest. There is no modern analog of the prehuman forests on any northern New Zealand island, and those islands that are forested are dominated by angiosperms which are assumed to be climax forests. The pollen and DNA evidence for conifer- and palm-rich forests in the prehuman era challenge this climax forest assumption. Prehuman vegetation records can thus help to inform future restoration of degraded offshore islands by informing the likely rate and direction of successional change; helping to determine whether natural rates of succession are preferable to more costly replanting programs; and providing past species lists if restoration replanting is desired.

Biological signaling field in mammals (for 110th Anniversary of Professor N.P. Naumov)

Last 30 years the concept of biological signaling field, proposed by N.P. Naumov, developed, by and large, on the base of its main proposition according to which mammals leave on the landscape objects within a biogeocenosis some traces of their life activity forming, from generation to generation, the so called "matrix of stable elements" (Naumov, Goltzman et al., 1987). This matrix of stable elements is, really, a system of attractors. Within the context of signaling field, attractors are objects that attract animals' attention (Goltzman, Kruchenkova, 1999) and organize their usage of territory with all the resources that could be found on this territory. Elements of landscape attracting animals' attention form a system of attractors of the first order (basic attractors) (Nikol'skii, 2011). In perspective, as the signaling field develops, it is exactly them that form the basis of the matrix of stable elements which the system of unstable elements would be attached to. With regard to attractors of the first order, traces of mammals' life activity can be treated as attractors of the second order. Animals do not mark the resources themselves, but only the territory where those resources are located. Stable elements produce an olfactory-optic image of the territory that is used by every new generation of mammals. A supposition is brought forward that, similar to biological productivity and species diversity, stable elements of signaling field are indicative of respective stages of an ecological succession. The matrix of stable elements is most steady in mature, climax communities. As an example, main runs that are used by many mammal species can be considered. Last years, publications appear regularly in which main propositions of the signaling field concept are applied. A necessary condition for further development of the concept seems to be the establishment of new exploratory methods including modeling of processes that lead to the matrix of stable elements formation.

Interrelations between Dreissena polymorpha colonization and autotrophic periphyton development – a field study in a temperate floodplain lake

Temporal changes in autotrophic periphyton (algae and cyanobacteria) in relation to the colonization of Dreissena polymorpha, an invasive species, were investigated in situ using artificial substrata (glass slides) from April to August of 2008 in a Danubian floodplain. The colonization of cyanobacteria and planktonic diatoms firmly attached to the substrata followed by the development of apical pad forming diatoms and stalk forming diatoms, resulted in the rapid formation of a three-dimensional structure of periphyton. Increasing water temperatures, to- gether with the well developed autotrophic periphyton, supported the colonization of Dreissena. A total of 16 size classes of Dreissena were found during the gradual mussel development. The most likely formed from the initially settled larvae which dominated the first period of aggregation, while adult individuals dominated the later phase, contributing to the increase in habitat complexity. High competition for space and nutri- ents on small-size substrata limited the autotrophic periphyton to achieve the climax community characterized by filamentous green algae. Consequently, algal abundance decreased and diatoms firmly attached to the substrata pre- vailed. The decrease in mussel abundance at the end of the colonization experiment enabled a gradual increase in diatom abundance and redevelopment of a three-dimensional autotrophic periphyton structure. Altogether, our re- sults showed that dense coverage of hard surfaces by mussels may have negatively influenced the algal causing a significant decrease in algal abundance and a shift to the dominance of species resistant to the disturbance.

Natural regeneration potential of abandoned agricultural land in the southern Gadarif Region, Sudan: implications for conservation

AbstractThe present study seeks to provide a contribution to the understanding of vegetation regrowth on abandoned agricultural land by investigating the impacts of the previous cultivation period and the duration of the fallow on the subsequent natural regeneration in terms of vegetation composition, structure and diversity. The results of the study show that both factors have significant effects on the subsequent regeneration of plant species and thus the vegetation development in the southern Gadarif Region, Sudan. The oldest abandoned farmlands were recolonized by tree/shrub species, whereas recently abandoned ones are covered with herbaceous vegetation. There is a general tendency regarding the number of species to decrease with an increase in the period of cultivation. The plant species diversity pattern shows domination of herbaceous species with some scattered woody species. Vegetation changes due to land abandonment may have implications for the conservation of plant species diversity and composition of fauna harboured in the region. Although natural regeneration could be recommended as means of restoring natural vegetation that previously dominated that region, the current regeneration capacity might not be sufficient to reach the climax vegetation except for some pockets, which received more regenerative resources.

Natural regeneration of shade-tolerant Abies alba Mill. in gradients of stand species compositions: Limitation by seed availability or safe microsites?

This paper analyses the effect of selected site and stand variables on the natural regeneration of the late-successional species Abies alba Mill. in a sequence of stands with increasing partition of three other tree species: light-demanding early-successional Pinus sylvestris (L.), moderately shade-tolerant Picea abies (L. Karst.), and shade-tolerant late-successional Fagus silvatica (L.). The data used originated from inventories carried out in publicly owned forests in southern Poland on a total of 2262 stands in a 30,700ha area. First, the effect of geographic location, altitude, slope, aspect, site trophism, stand age, stand volume and proportion of admixed species on the occurrence of A. alba regeneration was analysed using generalised linear models (GLZ). The empirical associations derived from these models were then compared with the expected outcomes for two scenarios of seedling over-dispersion given a decreasing number of trees producing seeds and a neutral effect of admixed species. The highest regeneration coverage was found in pure A. alba stands. In the mixed stands, regeneration coverage decreased with a decreasing proportion of A. alba, although at a lower rate than might be expected given a neutral effect of admixed species. The survival rate modelled in close to mono-specific stands (i.e., those with 90%) of P. abies, F. sylvatica and P. sylvestris was 3.0–8.5 times higher than in pure A. alba stands. Nevertheless, the reduced seed availability resulting from a lower number of seed producers in mixed stands might not be fully balanced by more advantageous microsite conditions. In stands with a high percentage of the early-successional species P. sylvestris, regenerative conditions were no more advantageous than in stands with a high percentage of late-successional species. The higher modelled survival rate of A. alba regeneration in stands of late-successional P. abies and F. sylvatica than in stands of con-specific trees may be viewed as an increase-when-rare mechanism. The question remains, however, of whether it is an intrinsically anthropogenic mechanism (e.g., increased herbivory pressure) or a natural mechanism capable of maintaining the mixed species composition of climax communities undisturbed by man.

Effects of Different Vegetation Types on Soil Microbiological Properties on the Loess Plateau

The re-establishment of natural species-rich health lands on abandoned farmland is one of the main measures in soil erosion control in the Loess Plateau of China. This study was conducted to understand how enzyme activities changed with nutritional properties and microbial biomass in different vegetation types in the loessial gully region of the Loess Plateau. Soil samples were collected in different vegetations which had planted for almost 30 years. For the collected soils, nutritional, microbial and enzymatic properties were determined. The result showed that soil nutritional properties and microbial biomass were enhanced in black locust-amorpha, compared with black locust, but weakened in Chinese pine-amorpha compared with Chinese pine. Besides, soil urease, α-amylase, alkaline phosphatase, catalase, saccharase and cellulase activities in creased with restoration, but decreased polyphenol oxidase. Moreover, urease activity was obviously high in korshinsk peashrub and black locust for the nitrogen fixation of them, and α-amylase was high in Chinese pine for low pH value. However, there still was a certain gap to Chinese arborvitae which was considered to be the climax community in the region. In general, the distance of vegetations to Chinese arborvitae was grassland &gt; black locust &gt; Chinese pine&gt; korshinsk peashrub &gt; Chinese pine-amorpha &gt; black locust-amorpha.

National‐scale assessment of ecological content in the world's largest land management framework

Meeting the diverse sustainability targets of modern society has led to the development of national‐level management frameworks meant to guide resource management actions and conservation funding decisions. In U.S. rangelands, state‐and‐transition models have been developed within the Ecological Site Description (ESD) Database as an application of alternative state theory and to move the discipline toward a more dynamic platform for resource management. After 15 years of development, and with government‐mandated collaboration among federal agencies, these models are set to become one of the world's largest guiding frameworks for terrestrial ecosystem management. Yet, ESD state‐and‐transition models are being marketed for broad‐scale application without a national‐level critique evaluating their strengths and limitations. In this article, we conduct a national assessment of ESDs with a central focus on evaluating the specific details of ESD state‐and‐transition models. Importantly, we are not evaluating the conceptual underpinnings of the state‐and‐transition management framework, but rather its application. Specifically, we (1) quantify and summarize the information presented in ESD state‐and‐transition models; (2) determine whether ESDs fully meet U.S. Congress's goal of a nationally consistent system for defining, mapping, and interpreting ecological sites; (3) identify limitations and logical holes in ESD predictions; and (4) evaluate whether conservation funding priorities are consistent with output from ESDs. Our evaluation reveals multiple shortcomings in the application of the state‐and‐transition model concept within ESDs, primarily that they are highly subjective, inconsistent in design and application, focus on a single historical climax community, and overuse grazing as a driver of both ecological degradation and restoration. Considering that many of these limitations have been a consistent criticism of rangeland assessment procedures throughout the history of the discipline, state‐and‐transition models within ESDs will require major reconstruction beyond the current plans for revision if they are to meet society's demand for more effective management and utilization of rangeland resources. While ESDs were developed to link science and management in rangeland ecology, our assessment suggests well‐intentioned management frameworks built upon expert opinion and qualitative inputs will not effectively shift ecosystem management from long‐held practices rooted in community climax theory to modern scientific perspectives based on alternative state theory.

From Formation to Ecosystem: Tansley’s Response to Clements’ Climax

Arthur G. Tansley never accepted Frederic E. Clements' view that succession is a developmental process whose final stage, the climax formation, is determined primarily by regional climate and that all other types of vegetation are some kind of successional stage or arrested successional stage. Tansley was convinced that in a given region a variety of environmental factors could produce different kinds of climax formations. At the heart of their dispute was Clements' organicist view of succession, i.e., the formation was a complex organism with an ontogeny and phylogeny. As early as 1905, Tansley offered an alternative to Clements' complex organism, the quasi-organism, but Clements in private and public rejected this compromise. Tansley and other plant ecologists continued to criticize Clements' theories for the next 20years, but with no impact on Clements. John Phillips, a South African plant ecologist who was a follower of Clements, published a series of papers in 1934 and 1935 defending Clementsian ecology. These papers were triggered by the publication of a letter by another ecologist working in Africa who claimed that there was a strong correlation between soils and various kinds of climax vegetation, which was contrary to what was predicted by Phillips and Clements. In 1935, Tansley published an attack on Phillips and Clements and their developmental theory of succession. In it, he proposed the concept of the ecosystem as a way to get around Clements' monoclimax theory by making the physical environment (e.g., soil chemistry, soil texture, soil moisture) as important a factor as climate, plants and other organisms in determining the composition and characteristics of ecological entities, i.e., ecosystems. Tansley's ecosystem concept quickly replaced Clements' monoclimax theory as a dominant paradigm in ecology.

FACTORS AFFECTING THE VEGETATION SUCCESSION OF MOIST·DECIDUOUS FORESTS AT SIGIRIYA SANCTUAR~SRILANKA

This study examines the vegetation succession of moist deciduous forests at the Sigiriyasanctuary and some factors affecting for this. Thirty eight 20x20m2 experimental plotswere established in sites ranging in disturbance history from areas abandoned for onemonth after swidden farming to forests not known to have been recently disturbed. Thevegetation was enumerated while the canopy openness, soil moisture and soil temperaturewere measured. Seed rain was monitored while the soil seed bank was enumerated threetimes over a year in four month intervals. Seedling bank was also enumerated in lx2m2quadrat in each experimental plot. Seed predation was examined by keeping seeds ofChloroxylon swietenia seeds in the experimental plots and by continuous observations.Succession appears to be a process of progressive change in species dominance and lossof less shade-tolerant subordinates rather than accumulation of new colonists. Both seedrain and soil seed bank in all these young successional forests contain many agriculturalweed species but the density of seeds of climax species is negligible. Consequently, theseedling bank is very poor and contains many agricultural weed and light demandingshrub species. The soil temperature in young successional forests is higher while the soilmoisture is lower than the older successional or high forests. After 18-20 years, the treesare released and shade-out light demanding species. This results in the death of most ofthe light demanding shrubs and as a consequence, root competition is reduced and morespace is available for the establishment of new immigrant climax forest species. The seedrain, soil seed bank and the seedling bank of 20-25 year old forests contain some seeds ofclimax forest species.High forests contain many climax forest tree ,IUd shrub species but seeds a.id seedlings ofvaluable timber tree species are rare in them. High seed predation is one reason for thissituation. Seedling bank is very fragmented and mostly contains individuals of climaxforest shrub species.It seems that the studied moist deciduous forests are somewhat degraded and thevegetation succession after a large scale disturbance is a slow process. Therefore,protection and rehabilitation of these forests are vital activities for their perpetuity.

Functional traits shed new light on the nature of ecotones: a study across a bog-to-forest sequence

Ecotones have long been a focus of ecological research, and there is considerable current interest in functional traits in community ecology. Yet, surprisingly, the functional trait approach has not been applied to ecotones. A bog-forest sequence in southern New Zealand was sampled with a grid of quadrats, and eight traits related to leaf function were measured on the 54 species found. Two ecotones were identified using moving-window analysis: Ecotone I was the transition from bog to edge forest, and Ecotone II was the transition from edge forest to tall climax forest. No strict ecotonal species were present. In contrast to theoretical predictions, species richness was not higher or lower in either ecotone, rather, both ecotones represented a transition in richness from one community to the other. It has long been said that ecotones are mosaics, but species mosaicity was no higher in either ecotone than in the adjacent communities, in fact it was lower in Ecotone I. Functional trait diversity decreased along the sequence from bog to forest, with no deviation in either ecotone. However, examining mosaicity in terms of traits, there was a steady rise in Ecotone I and, in conformance with ecotone / functional trait theory, a clear peak in Ecotone II. We conclude that the features claimed for ecotones are often not present, and whether they are present is dependent on the components measured: species vs traits. Here, the clearest patterns were seen in trait mosaicity, but even this differed markedly between the two ecotones. Generalisations about ecotones should be avoided; they will vary from ecotone to ecotone, and probably depend on the type of ecotone: anthropogenic, environmental, switch, etc.