Structure,diversity, and regeneration of tropical dry deciduous forest of northern India

This study examined the impact of disturbance on the pattern of diversity, forest structure and regeneration of tree species in the Vindhyan dry tropical forest of India. A total of 1500 quadrats distributed over five, 3-ha permanent plots in five sites, differing in degree of disturbance, were used to enumerate and measure the tree species. A total of 65 species with 136,983 individuals were enumerated in the total 15-ha area for stems 30 cm height. The number of species and number of stems ranged from 12 to 50 and 8063–65331 per 3-ha area. The number of species and stems for trees 10 cm dbh ranged from 3 to 28 species, with a mean value of 16 species ha^–1, and from 16 to 477 stems, with a mean value of 256 stems ha^–1, respectively. The adult based PCA ordination indicated uniqueness of sites in terms of species composition and habitat characteristics. PCA ordination also showed uniqueness of sites in terms of seedling composition, but the seedling and adult distributions were not spatially associated. The distinct species composition at the different sites and at the two life-cycle stages on the same site is indicative of marked spatio-temporal dynamics of the dry tropical forest. The density–diameter semi-logarithmic curves ranged from a near linear to an overall concave appearance with a limited plateau in the mid-diameter ranges. The -diversity and its components decreased with increasing disturbance intensity, reflecting enhanced utilization pressure with increasing disturbance. The site-wise and species-wise regression analyses of the number of individuals in different stages of the species revealed that both the level of disturbance and the nature of species strongly affect the regeneration. In conclusion, although the forest is relatively species-poor, the differential species composition on different sites and the temporal dynamics lend a unique level of diversity to the tropical dry deciduous forest.     

Diatom and micro-invertebrate communities and environmental determinants in the western Australian wheatbelt: a response to salinization

Diatom and micro-invertebrate communities were analyzed in 56 lentic wetlands from the wheatbelt of Western Australia. Sixteen water quality parameters were measured at each habitat and were tested as determinants of diatom and micro-invertebrate distribution. Nearly all waters were dominated by Na¹⁺ and Cl^1– and over half had low buffering capacity (<2 meq/L as TCO). Salinities ranged from <1 to > 240 mS/cm; some hypersaline habitats had pH values as low as 2.1, but most sites were alkaline.Diatoms (165 taxa) were present in all habitats, with indications that assemblages are correlated with land-use practices, i.e., historical clearing of native vegetation for dryland agriculture with resultant hydrological problems of salinization and water-logging. A non-metric multidimensional ordination showed pH, salinity, TCO, and total phosphorus to be significantly correlated with diatom community structure. Principal components analysis showed similar patterns. A salinity index was also developed for numerically important diatom taxa. Principal components analysis showed similar patterns. Certain tolerant Bacillariales, including Hantzschia amphioxys, Nitzschia hybrida, Tryblionella hungarica, and N.recta, were numerically important taxa in wetlands with visible signs of salinization.Micro-invertebrates (143 taxa) were present in habitats with salinities up to 200 mS/cm. Multidimensional ordinations showed salinity to be significantly correlated with micro-invertebrate community structure. The cladoceran Daphniopsis queenslandensis, ostracods Australocypris insularis, Mytilocypris tasmanica chapmani, and Platycypris baueri, and copepods Apocyclops dengizicus and Mesochra nr. flava were numerically important micro-invertebrates in moderate to high salinity environments, including those with signs of salinization. The diatoms, Navicula minuscula var. muralis and Pinnularia divergentissa var.subrostrata, and the copepod, Calamoecia trilobata, were common inhabitants of the extreme hypersaline (75 mS/cm), acidic (<4) habitats. Diatom communities were similar to those previously reported for other regions in Australia subjected to salinization; there were some differences in micro-invertebrate communities.     

Assessing Simple Versus Complex Restoration Strategies for Industrially Disturbed Forests

Assessing the community‐level consequences of ecological restoration treatments is essential to guide future restoration efforts. We compared the vegetation composition and species richness of restored sites that received a range of restoration treatments and those of unrestored sites that experienced varying levels of disturbance. Our study was conducted in the industrially degraded landscape surrounding Sudbury, Ontario, Canada. The Great Lakes–St. Lawrence Forest once present in this area was degraded through logging, mining, and smelting activities beginning in the late 1800s until restoration of the most visibly degraded areas began in 1974. Restoration treatments ranged from simple abiotic enhancements to complex, multistage revegetation treatments using native and non‐native species, which included fertilizing, spreading of ground dolomitic limestone, understory seeding, and tree planting. Canonical correspondence analysis was used to determine which restoration treatments explained differences in the community structure among sites. We found that native understory vascular species richness was similar in restored sites that received more complex restoration treatments and unrestored sites that were mildly disturbed; however, the role of planted trees and non‐native species in the restored communities remains unclear. Understory vascular seeding played a key role in determining community composition of vascular understory and overstory communities, but the time since restoration commenced was a more important factor for nonvascular communities because they received no direct biotic enhancements. The use of non‐native species in the vascular seed mix seems to be slowly encouraging the colonization of native species, but non‐natives continue to dominate restored sites 25 years after restoration began.     

拉萨河谷草地群落的数量分类与排序

采用TWINSPAN数量分类和DCA、CCA排序的方法,对拉萨河谷草地23个样点进行统计分析。结果显示:(1)TWINSPAN数量分类将拉萨河谷草地群落划分成8种类型,拉萨河谷的草地群落分布呈现明显的垂直地带性分布格局。(2)TWINSPAN分类所划分的各群落在DCA排序图上都有各自的分布范围和界限,说明DCA排序能较好的反应各群落与其环境资源之间的关系,同时,TWINSPAN的分类结果也在排序图上得到较好的印证。(3)样点DCA排序的第一轴基本反映了海拔高度的变化梯度,第二轴基本反映了坡向的变化。(4)样点CCA排序表明,影响群落分布的主要环境因子是海拔,其次是坡向。CCA排序进一步阐明了拉萨河谷草地群落分布决定于海拔和坡向等环境因子,并间接验证了TWINSPAN的分类结果。(5)物种CCA排序和TWINSPAN分类结果表明:植物群落中物种的分布格局与植物群落类型的分布格局存在一定的相似性,物种的分布格局在很大程度上影响着群落的分布格局。     

Multivariate analyses in microbial ecology

Environmental microbiology is undergoing a dramatic revolution due to the increasing accumulation of biological information and contextual environmental parameters. This will not only enable a better identification of diversity patterns, but will also shed more light on the associated environmental conditions, spatial locations, and seasonal fluctuations, which could explain such patterns. Complex ecological questions may now be addressed using multivariate statistical analyses, which represent a vast potential of techniques that are still underexploited. Here, well-established exploratory and hypothesis-driven approaches are reviewed, so as to foster their addition to the microbial ecologist toolbox. Because such tools aim at reducing data set complexity, at identifying major patterns and putative causal factors, they will certainly find many applications in microbial ecology.     

Comparing agglomerative clustering and three weed classification frameworks to assess the invasiveness of alien species across spatial scales

To prioritize weed management at the catchment scale, information is required on the species present, their relatively frequency, abundance, and likely spread and impact. The objective of this study was to classify the invasiveness of alien species that have invaded the Upper Burdekin Catchment in Queensland, Australia, at three spatial scales. A combination of three published weed classification frameworks and multivariate techniques were employed to classify species based on their frequency and cover at a range of spatial scales. We surveyed the Upper Burdekin Catchment for alien species, and for each species determined the following distribution indices — site frequency, total cover, transect frequency per site frequency and quadrat frequency per site frequency, cover per quadrat when present, cover per transect when present, and cover per site when present. These indices capture the effect of species abundance and frequency between sites (site frequency and total cover), within sites (transect frequency per site and cover per transect when present), and within transects (quadrat frequency per site frequency and cover per site). They were used to classify the species into seven groups using a hierarchical cluster analysis. The relationship between the indices was explored to determine how effective the small scale, site‐specific indices were at predicting the broader, landscape‐scale patterns. Strong correlations were observed between transect frequency per site and frequency (r² = 0.89) and cover per transect when present and total cover (r² = 0.62). This suggests that if a weed is abundant at the site level, it has the potential to occupy large areas of the catchment. The species groupings derived from the application of the three published weed classification frameworks were compared graphically to the groupings derived from the cluster analysis. One of the frameworks classified species into three groups. The other two frameworks classified species into four groups. There was a high degree of subjectivity in applying the frameworks to the survey data. Some of the data were of no relevance to the classification frameworks and were therefore ignored. We suggest that the weed classification frameworks should be used in conjunction with existing multivariate techniques to ensure that classifications capture important natural variations in observed data that may reflect invasion processes. The combined use of the frameworks and multivariate techniques enabled us to aggregate species into categories appropriate for management.     

Spoil Heaps From Brown Coal Mining: Technical Reclamation Versus Spontaneous Revegetation

Abstract Vegetation samples from either spontaneously revegetated or technically reclaimed spoil heaps of different ages in one of the largest active brown coal mining districts in Europe were analyzed and compared. The spoil heaps are located in the northwestern part of the Czech Republic and represent ages between 0 and 45 years. Ordination analysis (detrended correspondence analysis) showed that vegetation on technically reclaimed spoil heaps developed in a different way than that on spontaneously revegetated ones. The latter exhibited much higher species diversity in the oldest stages with the number of species doubled that of technically reclaimed sites. The oldest stages were also more advanced along an expected successional gradient as indicated by the ordination. Accelerating the vegetation development by technical reclamation was only of temporal character, whereas spontaneous succession proceeded further over the longer time scale. Spontaneous succession is advocated as an inexpensive and easy alternative to technical reclamation, because it leads to a more natural and rich vegetation cover. Unfortunately, technical reclamation is still the only approach considered in the present reclamation activities for this region.     

南泥湾片段森林蝗虫群落多样性比较

应用多样性指数、排序和多元逐步回归分析方法比较了南泥湾片断化森林的蝗虫群落结构,并进行了环境因素的解释。结果显示：在南泥湾,树木破坏不严重的片断化森林,随森林面积的减小,林缘草层蝗虫种类、多样性指数和均匀度指数差异不大;林中草层蝗虫密度、多样性指数和均匀度指数减小。在面积小、树木破坏严重、植被结构发生明显改变的片断森林林中草层,相对于树木破坏不严重的片断化森林,蝗虫的密度、多样性指数和均匀度指数明显增大;而林缘草层蝗虫的密度和群落优势度指数上升,多样性指数和均匀度指数下降。以主分量分析方法可明显将林中草层蝗虫群落分为森林破坏严重和不严重两种类型。通过多元逐步回归分析发现,影响片断化森林蝗虫群落结构和多样性的主要因素有片断森林面积、森林植被结构的复杂性、食料植物的多少等几个方面。