地表蚂蚁在云南萨王纳地区植被恢复过程中的指示作用

为了查清地表蚂蚁在萨王纳地区人工植被恢复过程中的指示作用,采用陷阱法调查了云南省萨王纳地区人工林和自然植被地表蚂蚁多样性。(1)群落物种组成:采集蚂蚁40467头,隶属于5亚科19属47种。扁平虹臭蚁Iridomyrmes anceps是保护较好自然植被的常见种;而迈氏小家蚁Monomorium mayri是干扰较大的自然植被及多数人工林的常见种。(2)多度和α多样性:在人工林中,印楝林地表蚂蚁群落多度和α多样性最高,桉树林次之,新银合欢林最低。(3)群落相似性及β多样性:印楝林地表蚂蚁群落与自然植被灌草丛较接近,而其它人工林蚂蚁物种组成不相似;新银合欢林β多样性最高,βCs值在0.481—0.935;印楝林较低,βCs值在0.200—0.478。(4)相关性分析:地表蚂蚁群落物种丰富度S值及ACE值和草本植物群落S值及ACE值均正相关。印楝林和桉树林具有较高的α多样性,在当地生物多样性保护中具有积极意义;而新银合欢林是生境极度退化区域的重要植被恢复模式之一,这3种人工林对于萨王纳地区植被恢复具有重要作用。蚂蚁群落α多样性能够作为生物多样性的指示物,指示云南萨王纳地区植被恢复中生物多样性的状况。     

金沙江河谷苏铁天然植物群落的研究

近年在金沙江干热河谷及其邻近地区陆续发现的苏铁天然植物群落,为本属植物在欧亚大陆内陆分布的最北边缘。其中,面积最大和保存较好的是渡口市攀枝花苏铁(Cycas panzhihuaensis)植物群落。本文研究了这个群落的分布与生境、生长状况、外貌、种类组成以及群落的综合特征等。认为具有稀树草原的特点,而这里的稀树草原是次生性质的,苏铁群落是其中幸存的残遗植被类型。这对研究我国植物地理有着重要意义。     

云南元江干热河谷半萨王纳植被的植物群落学研究

采用Ｂｒａｕｎ－ Ｂｌａｎｑｕｅｔ 植物群落学研究的理论与方法, 对云南元江中上游干热河谷分布的植被进行考察研究, 把各处取得较典型的１１０ 个样地记录按确限度的原则由下而上归类成１５ 个群丛、５ 个群属、２ 个群目和１ 个群纲, 建立了元江干热河谷萨王纳植被群纲—群目—群属—群丛分类系统综合表和１５ 个群丛表, 以全面深入反映全干热河谷植物群落各级分类单位中各植物种类组成的多优度、存在度、盖度系数、生活型和生长型等特征及其群落结构、生态环境和种型类别。在此基础上, 根据群落的种类组成、结构和生态特征, 确定元江干热河谷植被为萨王纳中“河谷型半萨王纳植被”, 主要是“树萨王纳”和“灌萨王纳”, 肉质刺灌丛属于灌萨王纳。     

金沙江干热河谷(元谋段)丛枝菌根真菌多样性研究*

从金沙江干热河谷(元谋段)75种植物的根际土壤中分离鉴定了44种丛枝菌根真菌, 分属无梗囊霉属Acaulospora、古孢霉属Archaeospora、内养囊霉属Entrophospora、巨孢囊霉属Gigaspora、球囊霉属Glomus和盾巨孢囊霉属Scutellospora, 其中,球囊霉属和无梗囊霉属为金沙江干热河谷中丛枝菌根真菌的优势属。齿状无梗囊霉A. denticulata、刺状无梗囊霉A. spinosa、瘤状无梗囊A. tuberculata,近明球囊霉Glomus claroideum、明球囊霉G. clarum、根内球囊霉G. intraradices、单孢球囊霉G. monosporum、弯丝球囊霉G. sinuosa是金沙江干热河谷(元谋段)的优势种。金沙江干热河谷土壤中丛枝菌根真菌的孢子密度为5~6400个/100g土壤,平均1504;每个根际土壤中丛枝菌根真菌的物种丰富度1~18种,平均9种。     

金沙江干热河谷(元谋段)丛枝菌根真菌多样性研究

从金沙江干热河谷(元谋段)75种植物的根际土壤中分离鉴定了44种丛枝菌根真菌, 分属无梗囊霉属Acaulospora、古孢霉属Archaeospora、内养囊霉属Entrophospora、巨孢囊霉属Gigaspora、球囊霉属Glomus和盾巨孢囊霉属Scutellospora, 其中,球囊霉属和无梗囊霉属为金沙江干热河谷中丛枝菌根真菌的优势属。齿状无梗囊霉A. denticulata、刺状无梗囊霉A. spinosa、瘤状无梗囊A. tuberculata,近明球囊霉Glomus claroideum、明球囊霉G. clarum、根内球囊霉G. intraradices、单孢球囊霉G. monosporum、弯丝球囊霉G. sinuosa是金沙江干热河谷(元谋段)的优势种。金沙江干热河谷土壤中丛枝菌根真菌的孢子密度为5~6400个/100g土壤,平均1504;每个根际土壤中丛枝菌根真菌的物种丰富度1~18种,平均9种。     

金沙江干热河谷的资源植物及其生态特征

金沙江干热河谷是金沙江沿岸具有特殊景观的一类地区,其环境特点是热量高,水份含量低。金沙江干热河谷资源植物多样性及其生态与分布特点的初步研究表明,金沙江干热河谷有记载的资源植物为５８５种,占全部１００４种植物的５８．３％。将资源植物分为９类,其中以药用植物的种类最多,达３７７种,占全部资源植物的６４．４％。资源植物的生长型、生活型、叶型等生态成分反映出生态环境的干热特点,也为资源植物的进一步引种提供基础。     

滇川干热河谷植被布朗布朗喀群落分类单位的植物群落学分类

按布郎布朗喀群落分类单位,即从群丛,群属,群目至群纲,用植物群落学或植物区系－群落学的分类方法,建立了滇川干热河谷植被群纲－群目－群属－群丛分类系统表。表上有元江,怒江和金沙江三江河谷型半萨王纳植被的１个群纲４个群目,１０个群属和６４个群丛,均由５２３个样地记录归类而成。     

金沙江干热河谷(元谋段)的丛枝菌根

用碱解离、酸性品红染色法对金沙江干热河谷(元谋段)中生长的60种植物的丛枝菌根状况进行了调查。结果发现被调查植物中70％的植物形成丛枝菌根,干热河谷自然植物群落中的建群种大多具有丛枝菌根,一些莎草科、蓼科的植物也形成典型的丛枝菌根。丛枝菌根是干热河谷生态系统中的重要组成成分,在干热河谷的植被恢复中,必须同时考虑对地下植物共生真菌进行恢复。     

金沙江干热河谷（元谋段）丛枝菌根真菌多样性研究

从金沙江干热河谷(元谋段)75种植物的根际土壤中分离鉴定了44种丛枝菌根真菌,分属无梗囊霉属Acaulospora、古孢霉属Archaeospora、内养囊霉属Entrophospora、巨孢囊霉属Gigaspora、球囊霉属Glomus和盾巨孢囊霉属Scutellospora,其中,球囊霉属和无梗囊霉属为金沙江干热河谷中丛枝菌根真菌的优势属。齿状无梗囊霉A．denticulata、刺状无梗囊霉A．spinosa、瘤状无梗囊A．tuberculata,近明球囊霉Glomus claroideum、明球囊霉G．clarum、根内球囊霉G．intraradices、单孢球囊霉Gmonosporum、弯丝球囊霉G．sinuosa是金沙江干热河谷(元谋段)的优势种。金沙江干热河谷土壤中丛枝菌根真菌的孢子密度为5-6400个／100g土壤,平均1504;每个根际土壤中丛枝菌根真菌的物种丰富度1～18种,平均9种。     

滇中小百草岭多变石栎林植物区系的初步研究

多变石栎林是小百草岭地区亚热带山地植被垂直带上最具特征性的植被类型 ,也是该地区州级自然保护区境内面积最大、保存最为完整、最有保护价值的植被类型。通过该植被类型中 116种常见种和优势种的群落结构和植物区系分析表明 :仅有中国特有分布种和中国-喜马拉雅分布种能贯穿于该植被类型的整个群落结构之中 ,植物区系成分以热带亚洲、中国 -喜马拉雅和中国特有类型为主 ,表明它隶属东亚植物区 ,中国 -喜马拉雅森林植物亚区 ,云南高原地区 ,云南高原亚地区 (IIIE13a)的一个具体区系单元的基本特征 ;其中的中国特有种又以小百草岭与周边的滇西北、川、黔、藏地区 (主要为横断山地区 )所共有的种占优势 ,从而也表明了小百草岭种子植物区系与横断山植物区系的联系相对紧密 ;通过与周边地区相同植被类型的比较 ,显示其地处滇中高原北缘的地理位置及受金沙江干热河谷气候影响使得该植被类型垂直分布海拔较高 ,更偏“干”的特点。     

The role of remnants of Amazon savanna for the conservation of Neotropical mammal communities in eucalyptus plantations

In this study, we investigated the effects of the partial conversion of native Amazon savanna into a eucalyptus plantation on the richness, composition, and abundance of medium and large mammals. Considering these plantations as an integral component of a patchwork savanna landscape, we verified how the negative effects of these plantations can be buffered by the conservation of remnants of native habitat within their area. We analyzed the contribution of each type of Amazonian savanna to the maintenance of the mammalian fauna and the potential of eucalyptus plantations to substitute these native habitats. A total of 23 mammal species were recorded in line-transect surveys conducted within the conserved savanna. By contrast, only eight species were recorded in the eucalyptus plantation and none of them were exclusive to this vegetation. However, the landscape patchwork formed by plantations and savanna was more diverse and contained 19 species of mammals, highlighting the potential importance of remnant savanna vegetation. The maintenance of remnants of savanna habitat may thus be essential for ensuring the conservation of mammals in the anthropogenic landscape of this region. It will also be important to include as many different subtypes of native savanna vegetation as possible and to consider the connectivity between habitats.     

元谋干热河谷植被的类型研究 Ⅰ.群丛以上单位

本文主要用法瑞植物社会学学派的方法对元谋干热河谷植被的群丛以上单位进行划分和研究。经分析,确定了从群目(order)到群丛(association)的一个分类等级系统。整个河谷区的植被可以归入到扭黄茅、坡柳群目(Dodonaeo-Heteropogonetalia contorti)中,下面再分出两个群属(alliance)和九个群丛。经使用模糊聚类分析数学方法验证,分类基本合理。 经研究表明元谋干热河谷1600米以下地区的气候及植被特点与热带的稀树草原(savanna)十分相似,可以称为半自然稀树草原或次生性稀树草原(semi-natural savanna or secondarysavanna)。     

Fire weather risk differs across rain forest—savanna boundaries in the humid tropics of north‐eastern Australia

Alternative stable state theory has been applied to understanding the control by landscape fire activity of pyrophobic tropical rain forest and pyrophytic eucalypt savanna boundaries, which are often separated by tall eucalypt forests. We evaluate the microclimate of three vegetation types across an elevational gradient and their relative fire risk as measured by McArthur's Forest Fire Danger Index (FFDI). Microclimatic data were collected from rain forest, tall eucalypt forest and savanna sites on eight vegetation boundaries throughout the humid tropics in north Queensland over a 3‐year period and were compared with data from a nearby meteorological station. There was a clear annual pattern in daily FFDI with highest values in the austral winter dry season and lowest values in the austral summer wet season. There was a strong association of the meteorological station FFDI values with those from the three vegetation types, albeit they were substantially lower. The rank order of FFDI values among the vegetation types decreased from savanna, tall eucalypt forest, then rain forest, a pattern that was consistent across each transect. Only very rarely would rain forest be flammable, despite being adjacent to highly flammable savannas. These results demonstrate the very strong effect of vegetation type on microclimate and fire risk, compared with the weak effect of elevation, consistent with a fire–vegetation feedback. This study is the first demonstration of how vegetation type influences microclimate and fire risk across a topographically complex tropical forest–savanna gradient.     

Tree formations in relation with soil and grasses in a dry savanna in Mali, West Africa

The relationship between trees, grass and soil in a dry savanna in Mali was investigated, to identify variables that are most relevant to assess vegetation units. A 65 ha plateau was inventoried using a systematic square grid sampling pattern. Thirteen soil or topography variables, and tree and grass characteristics were measured at each sampling point. Multivariate analysis was used to separately analyse soil, tree and grass data, and to characterize tree–grass and tree–soil relationships. Four units of soils, four units of tree formations, and four units of grass formations were identified. There was a correspondence between these groups, indicative of four vegetation units: thicket, bare land, shrub savanna and tree savanna. Soil depth and soil texture were the soil variables that best related to tree vegetation. A negative correlation was found between tree basal area and grass dry biomass. Finally, vegetation units, as identified from tree species composition, had contrasted diameter structures and densities.     

Regional Fragmentation of Rain Forest in West Africa and Its Effect on Local Dung Beetle Assemblage Structure

Data from Ghana and Côte d'Ivoire, for local dung beetle assemblages of rain forest, plantations, and savanna, suggest that a subset of the savanna fauna has expanded its range across the Eastern Guinean Forest ecoregion, presumably in response to its conversion from continuous rain forest into an archipelago of forest fragments within a disturbance matrix of less shady plantation and farmland vegetation that more resembles moist savanna.     

Structure of the woody vegetation in disturbed and undisturbed arid savanna,Botswana

The structure of woody vegetation was studied in little disturbed arid savanna and in adjacent over-grazed vegetation. In the over-grazed areas density and cover of woody plants were higher than in the less disturbed vegetation. The difference was accounted for by one species, Acacia mellifera, which was strongly dominant in the overgrazed vegetation. In the open savanna, the woody species varied in height from small shrubs to trees, while the dense shrub vegetation was of uniformly low stature.It is suggested that, while the differences in total abundance of woody species depend on differences in the amount of soil water available for woody growth, differences in species composition and height distribution are governed by the spatial and temporal distribution of water in the soil profile.     

Do feral buffalo (Bubalus bubalis) explain the increase of woody cover in savannas of Kakadu National Park,Australia?

Aim To study changes in woody vegetation in both floodplains and eucalypt savanna over a 40‐year period using multi‐temporal spatial analysis of variation in density of a large introduced herbivore, the Asian water buffalo (Bubalus bubalis). Feral buffalo built up to high densities in the study area until c. 1985, after which a control programme almost eliminated the animals. From 1990, low densities of managed buffalo were maintained inside an enclosure. We compared trends in woody vegetation when buffalo were high‐density feral, low‐density managed or absent. Location The study area was located in and around a 116‐km² buffalo enclosure inside Kakadu National Park, in monsoonal northern Australia. Methods We analysed sequences of digitized and geo‐rectified aerial photographs, acquired in 1964, 1975, 1984, 1991 and 2004, to chart changes in woody cover on the floodplain and in the savanna. On the floodplain we assessed whether trees were present at these times at 14,568 points, and buffalo density was estimated from the density of animal tracks. In the savanna we estimated woody cover at pre‐selected sites. Generalized linear modelling was used to analyse changes in woody vegetation, using elevation and presence of woody vegetation in neighbouring points on the floodplain, and buffalo regime and initial woody cover in the savanna. Results Changes in animal track density reflected park‐wide historical estimates of buffalo numbers. Tree cover increased in both floodplain and savanna, but this was only weakly related to buffalo density. The best predictor of whether a floodplain cell converted from treeless to woody, or the converse, was the woodiness of neighbouring vegetation. There was slightly less thickening with high buffalo densities. In savanna, low densities of managed buffalo were weakly associated with increases in tree cover relative to either high densities of feral buffalo or no buffalo. Main conclusions Our study indicates that buffalo are not a major driver of floodplain and eucalypt savanna dynamics. Rather, the observed increase in woody cover in both savanna and flood plains concords with regional trends and may be related to increased atmospheric CO₂, increasing rainfall and changing fire regimes during the study period.     

Winners and losers: tropical forest tree seedling survival across a West African forest–savanna transition

Forest encroachment into savanna is occurring at an unprecedented rate across tropical Africa, leading to a loss of valuable savanna habitat. One of the first stages of forest encroachment is the establishment of tree seedlings at the forest–savanna transition. This study examines the demographic bottleneck in the seedlings of five species of tropical forest pioneer trees in a forest–savanna transition zone in West Africa. Five species of tropical pioneer forest tree seedlings were planted in savanna, mixed/transition, and forest vegetation types and grown for 12 months, during which time fire occurred in the area. We examined seedling survival rates, height, and stem diameter before and after fire; and seedling biomass and starch allocation patterns after fire. Seedling survival rates were significantly affected by fire, drought, and vegetation type. Seedlings that preferentially allocated more resources to increasing root and leaf starch (starch storage helps recovery from fire) survived better in savanna environments (frequently burnt), while seedlings that allocated more resources to growth and resource‐capture traits (height, the number of leaves, stem diameter, specific leaf area, specific root length, root‐to‐shoot ratio) survived better in mixed/transition and forest environments. Larger (taller with a greater stem diameter) seedlings survived burning better than smaller seedlings. However, larger seedlings survived better than smaller ones even in the absence of fire. Bombax buonopozense was the forest species that survived best in the savanna environment, likely as a result of increased access to light allowing greater investment in belowground starch storage capacity and therefore a greater ability to cope with fire. Synthesis: Forest pioneer tree species survived best through fire and drought in the savanna compared to the other two vegetation types. This was likely a result of the open‐canopied savanna providing greater access to light, thereby releasing seedlings from light limitation and enabling them to make and store more starch. Fire can be used as a management tool for controlling forest encroachment into savanna as it significantly affects seedling survival. However, if rainfall increases as a result of global change factors, encroachment may be more difficult to control as seedling survival ostensibly increases when the pressure of drought is lifted. We propose B. buonopozense as an indicator species for forest encroachment into savanna in West African forest–savanna transitions.     

Herbaceous vegetation responses to experimental fire in savannas and forests depend on biome and climate

Fire–vegetation feedbacks potentially maintain global savanna and forest distributions. Accordingly, vegetation in savanna and forest ecosystems should have differential responses to fire, but fire response data for herbaceous vegetation have yet to be synthesized across biomes. Here, we examined herbaceous vegetation responses to experimental fire at 30 sites spanning four continents. Across a variety of metrics, herbaceous vegetation increased in abundance where fire was applied, with larger responses to fire in wetter and in cooler and/or less seasonal systems. Compared to forests, savannas were associated with a 4.8 (±0.4) times larger difference in herbaceous vegetation abundance for burned versus unburned plots. In particular, grass cover decreased with fire exclusion in savannas, largely via decreases in C₄ grass cover, whereas changes in fire frequency had a relatively weak effect on grass cover in forests. These differential responses underscore the importance of fire for maintaining the vegetation structure of savannas and forests.     

Strong positive effects of termites on savanna bird abundance and diversity are amplified by large herbivore exclusion

Vast areas of the African savanna landscapes are characterized by tree‐covered Macrotermes termite mounds embedded within a relatively open savanna matrix. In concert with termites, large herbivores are important determinants of savanna woody vegetation cover. The relative cover of woody species has considerable effects on savanna function. Despite the potentially important ecological relationships between termite mounds, woody plants, large herbivores, and birds, these associations have previously received surprisingly little attention. We experimentally studied the effects of termites and large herbivores on the avian community in Lake Mburo National Park, Uganda, where woody vegetation is essentially limited to termite mounds. Our experiment comprised of four treatments in nine replicates; unfenced termite mounds, fenced mounds (excluding large mammals), unfenced adjacent savanna, and fenced savanna. We recorded species identity, abundance, and behavior of all birds observed on these plots over a two‐month period, from late dry until wet season. Birds used termite mounds almost exclusively, with only 3.5% of observations occurring in the treeless intermound savanna matrix. Mean abundance and species richness of birds doubled on fenced (large herbivores excluded) compared to unfenced mounds. Feeding behavior increased when large mammals were excluded from mounds, both in absolute number of observed individuals, and relative to other behaviors. This study documents the fundamental positive impact of Macrotermes termites on bird abundance and diversity in an African savanna. Birds play crucial functional roles in savanna ecosystems, for example, by dispersing fruits or regulating herbivorous insect populations. Thus, the role of birds in savanna dynamics depends on the distribution and abundance of termite mounds.