Short-term waterlogging increases arbuscular mycorrhizal fungal species richness and shifts community composition

Plant and Soil - Our aim was to investigate the effects of short-term waterlogging in shaping communities of the obligately aerobic AMF in roots of Populus deltoides. AMF community in populus roots...     

Comparing tree diversity and composition in coffee farms and sacred forests in the Western Ghats of India

Expansion of coffee cultivation is one of the causes of deforestation and biodiversity loss. However, shade grown coffee has been promoted as a means for preserving biodiversity in the tropics. In this study we compared tree diversity in two types of coffee management regimes with the sacred groves in the Western Ghats of India. We computed species accumulation curves, species diversity indices and evenness indices to compare the different management regimes. Results of diversity indices showed that shade coffee had less diversity compared to sacred groves. Exotic species dominated the tree diversity in lands where the tree harvesting rights are with the growers. Native trees dominated the tree diversity when growers had no ownership rights on trees. A species accumulation curve suggested that the sacred grove had higher species richness compared to other two habitats. Lack of incentive to preserve endemic species as shade trees is forcing growers to plant more exotic species in shade grown coffee plots. If encouraged, shade grown coffee can preserve some biodiversity, but cannot provide all ecological benefits of a natural forest.     

Fire-induced shifts in overstory tree species composition and associated understory plant composition in Glacier National Park,Montana

In Rocky Mountain forests, fire can act as a mechanism of change in plant community composition if postfire conditions favor establishment of species other than those that dominated prefire tree communities. We sampled pre and postfire overstory and postfire understory species following recent (1988–2006) stand-replacing fires in Glacier National Park (GNP), Montana. We identified changes in relative density of tree species and groups of species (xerophytes vs. mesophytes and reseeders vs. resprouters) in early succession. Postfire tree seedling densities were adequate to maintain prefire forest structure, but relative densities among species were variously changed. Changes were directly related to individual species’ response to severe fires. Most notably, relative density of the mesophytic resprouter quaking aspen (Populus tremuloides) and the xerophytic reseeder lodgepole pine (Pinus contorta) increased substantially following fire, with a concomitant decline in proportional abundance of other tree species that, in some cases, dominated stands before fire. Trends identified in our study suggest that forest community shifts toward those dominated by lodgepole pine and quaking aspen are occurring in GNP. Cover of understory species was not affected by tree species composition or density. These forest communities will likely change throughout succession with the addition of shade-intolerant species in early seral stages and shade-tolerant species later in succession. However, with increased fire frequency, the lodgepole pine-dominated postfire communities observed in our study may become more common throughout time.     

Structure,composition and species diversity in an altitude-substrate matrix of rain forest tree communities on Mount Kinabalu,Borneo

We studied forest structure, composition and tree species diversity of eight plots in an environmental matrix of four altitudes (700, 1700, 2700 and 3100 m) and two types of geological substrates (ultrabasic and non-ultrabasic rocks) on Mount Kinabalu, Borneo. On both substrate series, forest stature, mean leaf area and tree species diversity (both 4.8 cm and 10 cm diameter at breast height [dbh]) decreased with altitude. The two forests on the different substrate series were similar at 700 m in structure, generic and familial composition and tree species diversity, but became dissimilar with increasing altitude. The decline in stature with altitude was steeper on the ultrabasic substrates than on the non-ultrabasic substrates, and tree species diversity was generally lower on ultrabasic substrates than on non-ultrabasic substrates at 1700 m. The forests on non-ultrabasic substrates at higher altitudes and those on ultrabasic substrates at the lower altitudes were similar in dbh versus tree height allometry, mean leaf area, and generic and familial composition at 1700 m. These contrasting patterns in forest structure and composition between the two substrate series suggested that altitudinal change was compressed on the ultrabasic substrates compared to the non-ultrabasic substrates. Tree species diversity was correlated with maximum tree height and estimated aboveground biomass, but was not with basal area, among the eight study sites. We suggest that forests with higher tree species diversity are characterized by greater biomass allocation to height growth relative to trunk diameter growth under more productive environment than forests with lower tree species diversity.     

Rapid shifts in the structure and composition of a protistan assemblage during bottle incubations affect estimates of total protistan species richness

Changes in the structure and composition of a protistan community were characterized through the analysis of small-subunit ribosomal RNA gene (18S) sequences for a 3-day bottle incubation using a single sample collected in the western North Atlantic. Cloning and sequencing was used to investigate changes in perceived species richness and diversity as a consequence of environmental perturbation. The treatments included a control (unamended seawater), inorganic nutrient enrichment, and enrichment with a complex organic mixture. Five clone libraries were constructed and analyzed at the time of collection (t-0?h) and after 24 (t-24?h) and 72 (t-72?h) h for the control, and at t-72?h for the inorganic and organic enrichments, resulting in an analysis of 1,626 partial 18S rDNA sequences that clustered into 238 operational taxonomic units (OTUs). Analysis of the clone libraries revealed that protistan assemblages were highly dynamic and changed substantially at both the OTU level and higher taxonomic classifications during time frames consistent with many oceanographic methods used for measuring biological rates. Changes were most dramatic in enrichments, which yielded community compositions that were strongly dominated by one or a few taxa. Changes in community structure during incubation dramatically influenced estimates of species richness, which were substantially lower with longer incubation and especially with amendment, even though all incubated samples originated from the same aliquot of seawater. Containment and enrichment of the seawater sample led to the detection of otherwise undetected protistan taxa, suggesting that characterization of protistan diversity in a sample only at the time of collection could lead to an underrepresentation of unique taxa. Additionally, the rapid increase in the relative abundance of some members of the ??rare biosphere?? in our results implies an ecological importance of at least some of the taxa comprising the ??rare biosphere.??     

Patterns of tree species richness in Jalisco,Mexico: relation to topography,climate and forest structure

The objective of this study was to identify the major environmental variables and components of forest structure associated with variability in tree species richness on a network of 806 permanent plots in the State of Jalisco, Mexico. Tree data recorded on the sample plots were used to characterize tree species richness by forest type and climatic conditions (temperature and precipitation) in the State. Species composition and other diversity indices were also calculated. Explanatory variables identified in a Poisson regression identified forest cover type, elevation, tree basal area, canopy closure, and winter precipitation as being important to changes in tree species richness. An “extreme quantile curve estimation” approach was then used to approximate the boundary that represented the maximum potential species richness response to the various levels of important variables. Maximum tree species richness decreased with increasing elevation. The relationships between maximum species richness and tree basal area, canopy closure, and winter precipitation followed a hump-back unimodal model, with intermediate values supporting the largest species richness. We believe that results of the current study will contribute to further development of a conservation plan for tree species in the State of Jalisco, Mexico.     

Relationship of butterfly diversity with nectar plant species richness in and around the Aokigahara primary woodland of Mount Fuji,central Japan

We examined the relationships between the diversities of vegetation, adult nectar plants, and butterflies in and around the Aokigahara primary woodland on the northwestern footslopes of Mount Fuji, central Japan. The results showed that the nectar resource utilization by adult butterflies was significantly biased to herbaceous plants, especially to perennials, compared to woody species, although most of the study area was in and near a primary woodland. There were greater nectar plant species in sites with greater plant species richness. Among the butterfly community indices analyzed, the strongest correlation was detected between butterfly species richness and nectar plant species richness at each site. Another close correlation was detected between the species richness of nectar plants and herbaceous plants at each site. These results suggest that herbaceous plant species richness in a habitat plays a central role in its nectar plant species richness, and the nectar plant richness is a highly important factor supporting its adult butterfly species richness. Consequently, we propose that the maintenance and management of herbaceous plant species richness in a butterfly habitat, which lead to those of its nectar plant species richness, are very important for conservation of butterfly diversity even in and around woodland landscapes of temperate regions.     

Effects of rain forest logging on species richness and assemblage composition of small mammals in Southeast Asia

Aim The effects of logging and habitat degradation on the richness and abundance of small mammals in Asian rain forests are largely unknown. This work compares the species richness, dominance and evenness of small non‐volant mammals between logged and unlogged forests, and assesses whether assemblage variability (β‐diversity) is similar between forest types. Location Southeast Asia, northern Borneo (Sabah, Malaysia), Sunda‐shelf. Methods We surveyed species‐rich assemblages of small non‐volant mammals in three unlogged and three logged forests for 2 years. At each forest site, we sampled a permanently marked transect and two additional sites in three trapping sessions. All analyses were performed at both levels to include the effects of local abundances and point estimates, separately from the relative abundances of species on a more regional scale. Results We trapped a total of 1218 individuals of 28 species. Eleven common species accounted for 95% of all captures. Species richness and diversity were significantly higher in unlogged forest (27 species) than in logged forest (17 species). This was mainly attributable to the smaller number of rarely recorded species in logged forest (five compared with 16 in unlogged forest, with a total of fewer than 10 captures). However, all common species were present in both logged and unlogged forests, and our analyses revealed similar patterns of dominance, evenness and fluctuations in abundance. Hence overall assemblage composition in multivariate space did not differ greatly between forest types. Assemblages of Muridae and Tupaiidae showed similar population fluctuations in space and time, indicating that the ecology of these taxa may be partially driven by the same environmental factors. Main conclusions Although species were distributed patchily within sites, analyses at local and regional scales revealed similar patterns in diversity and assemblage variability, suggesting that effects of forest modification did not differ extensively locally and regionally, but had a profound effect on rare species. Our results emphasize the importance and conservation value of logged forest stands that are able to hold a large proportion of the small mammals also found in unlogged forests. Rare and more specialized species are more vulnerable to forest degradation than commonly caught species, resulting in the complete loss, or a decrease in numbers, of certain groups, such as arboreal small mammals and Viverridae.     

Patterns of herbivore species richness in Kenya and current ecoclimatic stability

The increased attention to biodiversity worldwide has stimulatedinterest in understanding biophysical factors associated with indicators ofbiodiversity such as species richness. Although levels of biodiversity may seemto be equivalent in different areas, high species richness may be caused byaccumulation of species over a long time in places where environmentalconditions remained stable and predictable. The advanced very high resolutionradiometer (AVHRR)–normalized difference vegetation index (NDVI) has beenestablished to be a good proxy for studying interannual climate variability aswell as regional drought condition. In this study, I examined the relationshipbetween large herbivore species richness and AVHRR–NDVI derivedclimatic-variability indices, interannual average NDVI and coefficient ofvariation of NDVI at a regional spatial scale in Kenya. Regions with a relativelylow coefficient of variation of NDVI and high interannual average NDVIcharacterize current ecoclimatic stability. By contrast, a high coefficient ofvariation of NDVI and relatively low interannual average NDVI characterizeecoclimatic instability (drought risk). Statistical analyses revealed that a highinterannual average NDVI increases species richness, whereas a high coefficient ofvariation of NDVI lowers species richness. This indicates that maximum numbers ofspecies are found in regions with current ecoclimatic stability. Understandingsuch relationships can help in explaining spatial distribution of speciesrichness and predicting global changes resulting from human impacts on theenvironment.     

Habitat associations with topography and canopy structure of tree species in a tropical montane forest on Mount Kinabalu,Borneo

Habitat associations with topography and canopy structure of 42 abundant tree species were studied in a 2.74-ha plot of tropical montane forest on Mount Kinabalu, Borneo. Many of these species belong to the same higher taxa including eight families and four genera. Analysis of intraspecific spatial distributions for stems ≥ 10 cm diameter revealed that 28 species (including all six species of Fagaceae) showed aggregated distributions at the 100-m² and/or 400-m² scales, and that 20 species showed habitat associations with topography by torus-translation tests; 17 species showed both characteristics. Species' associations with the local canopy structure were characterized by crown position index (CPI), which was defined relative to neighbour trees. The CPI differed greatly among individual stems at 10–40 cm diameter, and 19 species showed significantly different frequencies of crowns exposed vertically versus those shaded beneath the canopy. Mean growth rates at 10–40 cm diameter and size distributions of species were not related to topographic associations, but were explained by the associations with canopy structure; species with more exposed crowns grew faster and had less positively skewed distributions. Diversity in habitat associations was manifest between two genera (Syzygium and Tristaniopsis) in the family Myrtaceae and among species in these genera, but was less evident in other families and two genera (Garcinia and Lithocarpus). This revised version was published online in June 2006 with corrections to the Cover Date.     

Differential diameter-size effects of forest management on tree species richness and community structure: implications for conservation

In this paper we tested the hypothesis that logging effects in the adult tree community reverberate upon the regeneration contingent. We examined the differences on the tree community between forest reserves and 10 year-old logged areas in the Yucatan Peninsula. We used a paired design in three independent sites to estimate the effects of logging on tree species richness, diversity, composition and structure. Analyses were conducted differentiating individuals of four diameter-size classes: 1–5, 5–10, 10–25, and >25 cm DBH. We found out that there were differential effects by size. Species richness in the smaller and larger diameter-size classes was significantly lower in logged areas. Floristic composition was also different between logged and unlogged areas, with a trend towards more secondary forest associated species and less primary forest associated species in logged areas, and a higher density of species represented by a single individual in unlogged reserves. In terms of structure, trees DBH <10 cm, lianas, and re-sprouting stumps were more abundant in logged areas. Our findings suggest that 10 years after logging, harvested areas show alterations in structure, and potentially a reduction in species richness. We suggest that to make timber extraction and forest conservation compatible at this site, it is necessary to gain a better understanding of the ecology and regeneration requirements of the less abundant species, and to assess whether current logging practices might hinder their permanence in the study area.     

Changes in fish species composition in Lake Naivasha,Kenya

The fish species composition in Lake Naivasha has been modified during recent years. Out of seven introduced and one indigenous species reported in 1962, only three introduced ones are found today. The elimination of species has been brought about by predation and changing ecological conditions. The most common fish species today is Sarotherodon leucosticuus. The hybridization found by previous workers between S. leucostictus x S. spilurus niger has stopped, as S. s. niger is no longer found in the lake. Most of the hybrid characters have been lost by the few surviving hybrids due to backcrossing between hybrids and between hybrids and S. leucostictus. The hybrids now mostly resemble S. leucostictus.     

煤炭开采对野生植物物种丰富度和物种组成的影响

煤炭开采引发的生态环境破坏早已引起关注,对其破坏机理和修复方法进行研究显得非常重要。本文探讨了煤炭开采对野生植物物种丰富度和物种组成成分的影响。从分布在晋西北地区的338个煤矿中,随机选择16个煤矿作为研究对象,调查了煤炭采空区和非采空区地面的野生植物物种,用Gleason丰富度指数分析了煤矿采空区和非采空区的野生植物物种丰富度差异,同时用Srensen指数分析了煤炭采空区野生植物物种组成成分和非采空区植物物种组成成分的相似性。结果表明:煤炭开采造成了野生植物物种数的减少,采空区的野生物种丰富度明显少于非采空区;煤炭开采也造成了野生植物物种组成成分的变化,采空区和非采空区的野生植物物种组成成分出现明显差异。     

Stochastic relations between species richness and the variability of species composition

Ecological communities change over time and space, and ecologists have long suggested that biodiversity might influence the rate of change. Here we cast new light on this question by demonstrating statistical covariation between species richness and the variability of species abundances and identities within a community (compositional variability). We provide a new analytical framework for several previously published measures of ecosystem functioning and compositional variability. We derive three related variances, each of which measures compositional variability due solely to stochastic sampling processes. Our analyses show that whether relations between species richness and compositional variability are positive, negative or zero, depends on two factors. Not only does the particular variance used affect the relation, but, more importantly, the underlying determinants of species richness can strongly affect the stochastic relations between species richness and compositional variability. This analysis makes clear for the first time how species richness should correlate with important measures of community variability, even in the absence of systematic processes.     

Context dependent effects of ectomycorrhizal species richness on tree seedling productivity

While there has been much recent interest about the relationships between plant diversity and plant productivity, much remains unknown about how the diversity of mycorrhizal fungi affects plant productivity. We investigated the effects of ectomycorrhizal fungal community composition and diversity on the productivity and growth characteristics of seedlings of two tree species ( Pinus sylvetris and Betula pendula ) as well as their interactions with each other. This involved setting up a mycorrhizal fungal diversity gradient from one to eight species using a design previously demonstrated to be able to separate diversity effects from compositional effects. We found that the eight mycorrhizal fungal species differed in their effects on seedling productivity and that the nature of effects was determined by the fertility of the substrate. Fungal species richness effects were also important in affecting seedling productivity over and above what could be explained by sampling effect but only in some situations. For B. pendula in a low fertility substrate there were clear positive causative effects between fungal species richness and productivity with the eight species treatment having over double the productivity of any of the eight monoculture treatments; no diversity effects were, however, detected in a high fertility substrate. For P. sylvestris in a high fertility substrate there were significant negative effects of fungal diversity on productivity while in a low fertility substrate no effects were apparent. The possible mechanistic bases for these results are discussed. The growth of P. sylvestris relative to that of B. pendula when grown in combination was unaffected by mycorrhizal treatments. Our results provide clear evidence that effects of mycorrhizal fungal diversity on productivity are context dependent and may be positive, negative or neutral depending on the situation considered.     

Dynamics,productivity and species richness of tropical rainforests along elevational and edaphic gradients on Mount Kinabalu,Borneo

We studied the dynamics of nine tropical rainforests on Mount Kinabalu, Borneo, at four elevations (700, 1,700, 2,700 and 3,100 m) on various edaphic conditions for four 2-year periods over 8 years (1995–2003), and examined the relationships with above-ground productivity. Mean growth rate of stem diameter, basal area turnover rate and estimated recruitment rate (using growth rate and size distribution) correlated with productivity among the nine forests in all periods. These rates based on growth rates of surviving stems appeared to be good measures of stand turnover. However, observed recruitment rate and mortality (and turnover rate as mean of these rates) based on direct observation of recruits and deaths did not correlate with productivity in some periods. These rates may not be useful as measures of stand turnover given small sample size and short census interval because they were highly influenced by stochastic fluctuation. A severe drought associated with the 1997–1998 El Niño event inflated mortality and depressed mean growth rate, recruitment rate and basal area turnover rate, but had little effect on the correlations between these rates (except mortality) and productivity. Across broad elevational and edaphic gradients on Mount Kinabalu, forest turnover, productivity and species richness correlated with each other, but the causal interpretation is difficult given the different histories and species pools among forests at different elevations.