No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Effect of tree canopy on herbaceous vegetation and soil characteristics in semi-arid forests of the Aravalli hills
Abstract
Herbaceous vegetation is of great ecological importance and responds quickly to environmental changes. The present study was aimed to understand the variation in herbaceous species composition, biomass and soil physico-chemical properties in the naturally formed gap and the understory of semi-arid forests in the Aravalli hills. Four permanent plots consisting of the gap as well as the understory were established. To study herbs phytosociological attributes and biomass, 10 quadrats of 0.5 X 0.5 m size were laid in each plot. For soil physico-chemical properties, 5 soil samples were collected randomly at 0–10 cm depth from each plot. Relationships among biodiversity indices, herbaceous biomass and soil physico-chemical properties were determined using Redundancy Analysis (RDA) and correlation analysis. Across the sites, Poaceae was the dominant family. All species showed a contagious distribution pattern. In the understory, Importance Value Index (IVI) was the recorded highest for Oplismenus burmannii, ranging from 138 to 230.5 while in the gap, it was the highest for Achyranthes aspera (56.15) followed by Eragrostis ciliaris (53.1). Both sites included, herbaceous community biomass in the gap ranging from 700 to 900 g m-2 while in the understory it ranged from 30 to 70 g m-2. Cenchrus ciliaris (597.97 g m-2) and Chrysopogon sp. (391.2 g m-2) contributed a major proportion of herbaceous community biomass in the gap. Oplismenus burmannii (52.2 g m-2), Dipteracanthus prostratus (16.6 g m-2) and Cynodon dactylon (9.6 g m-2) contributed a major proportion of herbaceous community biomass in the understory. The understory soil had significantly (p < 0.05) higher soil moisture (%), electrical conductivity (EC), soil organic carbon (SOC) and soil total nitrogen (TN) compared to the gap. Even though canopy had positive effects on soil physico-chemical properties, it has negatively influenced herbaceous species composition, diversity and biomass, due to significant reduction in solar radiation reaching the ground.
... The hypothesis is proposed here that a majority of today's churchgoers, priests and church officials in Russia are atheists or agnostics, habitually supporting the Soviet-time vision of the "West" as perpetual threat [24][25][26][27]. The politicization is illustrated by a paradox: the concept of Orthodoxy is broader than that of faith; some atheists designate themselves as Orthodox. ...
... Poor nutrient/ soil quality have been shown to promote the distribution of grasses, while trees species grow in nutrient rich and quality soils [25,26]. Furthermore, canopy gaps have been highlighted to affect herbaceous biomass, diversity, and soil physical properties [27]. ...
The book: https://novapublishers.com/shop/the-conflict-in-ukraine-psychopathology-and-social-aspects/
... The herbaceous vegetation growth simulations were conducted under two management scenarios: one with grazing in the spring season with stocking rates similar to those observed in the study area (about 0.5 LSU/ha/year) and another without grazing. The simulations were performed on a daily scale over a 50-year sample (49 years) of stochastic daily weather data generated from statistics collected over the historical series from 1985-2015 using the WXGEN climate generator (Nicks et al., 1990) [48]. ...
This study investigates the role of prescribed grazing as a sustainable fire prevention strategy in Mediterranean ecosystems, with a focus on Sardinia, an area highly susceptible to wildfires. Using FlamMap simulation software, we modeled fire behavior across various grazing and environmental conditions to assess the impact of grazing on fire severity indicators such as flame length, rate of spread, and fireline intensity. Results demonstrate that grazing can reduce fire severity by decreasing combustible biomass, achieving reductions of 25.9% in fire extent in wet years, 60.9% in median years, and 45.8% in dry years. Grazed areas exhibited significantly lower fire intensity, particularly under high canopy cover. These findings support the integration of grazing into fire management policies, highlighting its efficacy as a nature-based solution. However, the study’s scope is limited to small biomass fuels (1-h fuels); future research should extend to larger fuel classes to enhance the generalizability of prescribed grazing as a fire mitigation tool.
... This lack of light is more important for the establishment of herbaceous species, as shade reduces herbaceous species richness (Gillet et al. 1999;Fikadu and Zewdu 2021). Light is a key resource for the growth and survival of herbaceous species (Tinya et al. 2009;Plue et al. 2013;Garg et al. 2022) and is likely the reason we observed more herbaceous species in open areas compared to tree bases in interior forests, which had less available light because of greater canopy cover. ...
Since the type of forest influences vegetation patterns from the edge-to-interior forest, site-specific edge studies are needed but there have been few studies in open-canopied forests such as oak savannahs. Our objective was to compare patterns of herbaceous plant diversity along the forest edge-to-interior gradient between open areas and underneath oak trees in the Zagros Forest in Iran. We established eighteen transects from the forest edge to the interior in small and large forest fragments to sample herbaceous species in five 0.25 m² quadrats at 1 m intervals from the base of the tree to the open area at different distances from the forest edge. We analyzed the data using randomization tests for edge influence and generalized linear mixed models. Edge influence had a positive effect on herbaceous species richness and diversity underneath oak trees but a negative effect in open areas. At forest edges, species richness and diversity significantly decreased from the tree base toward open areas, but exhibited the opposite pattern away from the edge. Edge influence extended up to 50 m from the forest edge to the interior. Our findings highlight the importance of considering forest type and stand heterogeneity when studying edge influence on plant diversity. Our results show that edge studies are needed for specific forest types, particularly in heterogeneous landscapes, to ensure appropriate conservation of species diversity. We recommend establishing a 50-m buffer zone along edges in the Zagros Forest in Iran to minimize negative edge influence on herbaceous plant diversity.
... This is especially true in the Khanak range. Recently, Garg et al. (2021) found 19 herb species in the Delhi region, 11 of which were perennial (grass) species, and 8 of which were annual (forb species). Based on field research in the region, we found two wildlife sanctuaries in the upper range (Sultanpur Bird and Asola Bhatti WLS) as well as a national park in the upper range, all of which have been home to various species, including the Egyptian vulture and red-headed vulture, the white-faced Ibis, the Indian leopard, the Sambhar deer and wild cats . ...
In India's semi-arid climatic zone, the Aravalli hills range is an ecotone between the Thar Desert and the Gangetic plain, covering about 10% of the forest cover of Western India. Notably, the upper range of the hills has a high population density; this range has encountered substantial areal transformation in the last five decades. However, we believe that the enhancement of green cover within this range has occurred primarily due to discontinuous degradation within the entire range, without geographical alteration. We use MODIS products to compare and contrast spatiotemporal ecological dynamics between different sub-ranges (upper, middle, and lower) of Aravalli between 2000 and 2019. Specifically, we adopt seven eco-biophysical parameters that include EVI, LAI, PTC, PNTV, ET, NPP, and LST. Pixel-based time-series trend evaluation for MODIS imagery composite within the GEE platform, using the Ordinary Least Square (OLS) regression method identified that forest enhancement is experienced in some parts of different ranges. We also observed some human-induced factors and natural stressors that could possibly be responsible for forest health dynamics. Thus, we suggest sustainable planning and policy changes for people who are under anthropocentric stress; this we believe, would help management practices.
Aims
Plant roots often encounter heterogeneity in soil water content and respond by compensating water uptake from wet zones to cope with the transpiration demand. Simultaneously, plants may also exhibit root-mediated hydraulic redistribution from wet to dry zones. Experiments were conducted to simultaneously monitor compensated root water uptake and hydraulic redistribution in the vadose zone.
Methods
Vertical and horizontal split-root lysimeters were used to hydraulically isolate maize roots under altering soil water conditions. Compensated root water uptake and root-mediated hydraulic redistribution were monitored by continuous measurement of water content in the lysimeter compartments.
Results
Soil water heterogeneity and limited soil water availability were found to accelerate the root water uptake from moist region to compensate the reduced water availability in dry zone. However, no measurable root mediated hydraulic redistribution was observed in short term basis, despite high water potential gradient in the root zone of both lysimeters. The night-time transpiration and xylem refilling processes seem to override the hydraulic redistribution on a diurnal basis in our experiment.
Conclusions
Our study shows that compensated root water uptakeplays a major role in meeting the transpiration demand. In contrast, the role of root mediated hydraulic redistribution is found to benegligible in maize plant.
Understanding the effects of silvicultural practices including single-tree selection on soil properties is essential for forest management in temperate broadleaved beech forests. Changes in physico-chemical and biological soil properties in 15 harvest-created gaps under single-tree selection and the adjacent closed canopies, with five replications for each, were studied 6 years after gap creation in an oriental beech (Fagus orientalis L.) stand of the Hyrcanian forest. Gaps were classified into three size classes: small (85-130 m2), medium (131-175 m2) and large (176-300 m2). Soil cores were collected at the center and at the edge of gaps, and under the adjacent closed canopy. Results indicated that gap size significantly affected soil texture and bulk density, whereas soil organic carbon (SOC), total nitrogen and pH showed a significant gradient from the center to the edge of gap independently form their size. SOC and total nitrogen at the center of gaps were also significantly lower than closed-canopy, in particular for the medium-gap; contrastingly, the bulk density with the highest mean value was found at the center of the large-gap. Gap size had no significant influence on soil microbial biomass. These results highlighted that similar conditions in terms of many soil properties were still present among gaps and adjacent closed-canopy stands six years after logging, though canopy openness triggered a reduction in carbon and nitrogen availability along with the related microbial activity at the center of gaps, independently from their size. Therefore, if aimed at preserving an uneven aged structure along with soil quality in temperate broadleaved deciduous forest as the oriental beech stands in the Hyrcanian region, single-tree selection practice for harvesting trees can be recommended as sustainable forest management type.
Understorey vegetation comprises a major portion of plant diversity and contributes greatly to nutrient cycling and energy flow. This review examines the mechanisms involved in the response of understorey vegetation to stand development and the overstorey canopy following disturbances. The overall abundance and diversity of the understorey is enhanced with the availability and heterogeneity of light, soil nutrients, soil moisture, and substrates. Vascular plants are positively impacted by the availability and heterogeneity of light and soil nutrients, whereas non-vascular vegetation is more strongly influenced by colonization time, soil moisture, and substrates, and is decreased with a higher proportion of broadleaf overstorey. The availability of resources is a prominent driver toward the abundance and diversity of understorey vegetation, from the stand initiation to stem exclusion stage under a single-species dominated overstorey. However, resource heterogeneity dominates at the later stages of succession under a mixed overstorey. Climate and site conditions modify resource availability and heterogeneity in the understorey layer, but the extent of their influences requires more investigation. Forest management practices (clearcutting and partial harvesting) tend to increase light availability and heterogeneity, which facilitates the abundance and diversity of understorey vascular plants; however, these factors reduce the occurrence of non-vascular plants. Nevertheless, in the landscape context, anthropogenic disturbances homogenize environmental conditions and reduce beta-diversity, as well, the long-term effects of anthropogenic disturbances on understorey vegetation remain unclear, particularly compared with those in primary forests.
Assessment of carbon pools in semi-arid forests of India is crucial in order to develop a better action plan for management of such ecosystems under global climate change and rapid urbanization. This study, therefore, aims to assess the above- and belowground carbon storage potential of a semi-arid forest ecosystem of Delhi. For the study, two forest sites were selected, i.e., north ridge (NRF) and central ridge (CRF). Aboveground tree biomass was estimated by using growing stock volume equations developed by Forest Survey of India and specific wood density. Understory biomass was determined by harvest sampling method. Belowground (root) biomass was determined by using a developed equation. For soil organic carbon (SOC), soil samples were collected at 0–10-cm and 10–20-cm depth and carbon content was estimated. The present study estimated 90.51 Mg ha−1 biomass and 63.49 Mg C ha−1 carbon in the semi-arid forest of Delhi, India. The lower diameter classes showed highest tree density, i.e., 240 and 328 individuals ha−1 (11–20 cm), basal area, i.e., 8.7 (31–40 cm) and 6.08 m2 ha−1 (11–20 cm), and biomass, i.e., 24.25 and 23.57 Mg ha−1 (11–20 cm) in NRF and CRF, respectively. Furthermore, a significant contribution of biomass (7.8 Mg ha−1) in DBH class 81–90 cm in NRF suggested the importance of mature trees in biomass and carbon storage. The forests were predominantly occupied by Prosopis juliflora (Sw.) DC which also showed the highest contribution to the (approximately 40%) tree biomass. Carbon allocation was maximum in aboveground (40–49%), followed by soil (29.93–37.7%), belowground or root (20–22%), and litter (0.27–0.59%). Our study suggested plant biomass and soils are the potential pools of carbon storage in these forests. Furthermore, carbon storage in tree biomass was found to be mainly influenced by tree density, basal area, and species diversity. Trees belonging to lower DBH classes are the major carbon sinks in these forests. In the study, native trees contributed to the significant amount of carbon stored in their biomass and soils. The estimated data is important in framing forest management plans and strategies aimed at enhancing carbon sequestration potential of semi-arid forest ecosystems of India.
In recent decades, alternative management techniques integrating conservation concerns into industrial forestry have become increasingly widespread. In order to compare the effects of various management methods on forest site and biodiversity, a systematic forestry experiment was conducted in a managed, mature oak–hornbeam forest. The present work introduces the 2-year responses of environmental variables and understory vegetation to different silvicultural treatments. These belong either to clear-cutting (clear-cutting, retention tree group), to shelterwood (preparation cutting), or to continuous cover forestry systems (gap-cutting). The experiment follows a complete block design with four replicates. Light availability was significantly higher in all the treatments than in the uncut control, with highest values in the clear-cuts. Soil moisture was highest in the gap-cuts and clear-cuts, while in the retention tree group, it did not differ from the control. Species richness, cover, and height of the understory considerably differed from the control in the clear-cuts and gap-cuts, while in the retention tree group, only species richness was higher. The establishment of ruderal, non-forest species altered the species composition in the clear-cuts. Based on these short-term responses, we conclude that as a result of the extreme environmental changes, clear-cutting in oak–hornbeam forests changes the understory vegetation considerably. Retention tree groups can maintain legacies of the understory composition for some years. Despite the experienced high vegetation cover, gap-cutting preserves the forest characteristics of the understory better than clear-cutting. These results confirm that in oak–hornbeam forests, continuous cover forestry may be more sustainable from conservational aspect than clear-cutting system.
The work has been carried out from April 2012 to March 2016 with the main aim to document the floristic diversity of Angiosperms at the Asola Bhatti Wildlife Sanctuary, Delhi in a view to conserve native flora of the Aravalli biodiversity. The vegetation is dry deciduous consisting of Prosopis juliflora as dominant exotic species and Diospyros montana as dominant native species in the sanctuary. In the present study we documented 82 genera and 100 species from the trails selected in the sanctuary and analyzed over three seasons. we geo-tagged all the species encountered and frequency of species in disturbed trails was also assessed. Diagnostic features of all the documented species have been included, along with their protologue information.
We have limited understanding of how tropical canopy foliage varies along environmental gradients, and how this may in turn affect forest processes and functions. Here, we analyse the relationships between canopy leaf area index (LAI) and above ground herbaceous biomass (AGB H) along environmental gradients in a moist forest and miombo woodland in Tanzania. We recorded canopy structure and herbaceous biomass in 100 permanent vegetation plots (20 m × 40 m), stratified by elevation. We quantified tree species richness, evenness, Shannon diversity and predominant height as measures of structural variability, and disturbance (tree stumps), soil nutrients and elevation as indicators of environmental variability. Moist forest and miombo woodland differed substantially with respect to nearly all variables tested. Both structural and environmental variables were found to affect LAI and AGB H , the latter being additionally dependent on LAI in moist forest but not in miombo, where other factors are limiting. Combining structural and environmental predictors yielded the most powerful models. In moist forest, they explained 76% and 25% of deviance in LAI and AGB H, respectively. In miombo woodland, they explained 82% and 45% of deviance in LAI and AGB H. In moist forest, LAI increased non-linearly with predominant height and linearly with tree richness, and decreased with soil nitrogen except under high disturbance. Miombo woodland LAI increased linearly with stem density, soil phosphorous and nitrogen, and decreased linearly with tree species evenness. AGB H in moist forest decreased with LAI at lower elevations whilst increasing slightly at higher elevations. AGB H in miombo woodland increased linearly with soil nitrogen and soil pH. Overall, moist forest plots had denser canopies and lower AGB H compared with miombo plots. Further field studies are encouraged, to disentangle the direct influence of LAI on AGB H from complex interrelationships between stand structure, environmental gradients and disturbance in African forests and woodlands.
Seasonal variation in biomass, net primary productivity and turnover of dry matter of herbaceous layer under Albizia lebbeck (L.) Benth and Populus deltoides G3 Marsh plantations and in an adjacent open field was studied at Pusa in Bihar, eastern India. Live shoot biomass attained peak values of 682, 665 and 512 g m-2, respectively under A. lebbeck, P. deltoides and in open field in September. Corresponding values of net aboveground production were 749, 692 and 678 g m-2 year-1. The belowground net primary production of herbaceous layer was also highest under A. lebbeck (89 g m-2 year-1) followed by P. deltoides (110 g m-2 year-1) and open field (67 g m -2 year-1). The turnover rates of total plant biomass were maximum in the rainy season and the least in the summer season on all sites. Shoots shared 86 to 91% of annual total net primary production. Thus the herbaceous vegetation under the monsoon subtropical condition exhibited a strong seasonality in biomass production. Under the plantations, herbaceous biomass achieved higher net primary production compared to the open field.
Treefall gap, canopy opening caused by the death of one or more trees, is the dominant form of disturbance in many forest systems worldwide. Gaps play an important role in forest ecology helping to preserve bio- and pedo-diversity, influencing nutrient cycles, and maintaining the complex structure of the late-successional forests. Over the last 30 years, numerous reviews have been written describing gap dynamics. Here we synthesize current understanding on gap dynamics relating to tree regeneration with particular emphasis on gap characteristics considered critical to develop ecologically sustainable forest management systems and to conserve native biodiversity. Specifically, we addressed the question: how do gaps influence forest structure? From the literature reviewed, the size of gaps induces important changes in factors such as light intensity, soil humidity and soil biological properties that influence tree species regeneration and differ in gaps of different sizes. Shade-tolerant species can colonize small gaps; shade-intolerant species need large gaps for successful regeneration. Additionally, gap dynamics differ between temperate, boreal; and tropical forests, showing the importance of climate differences in driving forest regeneration. This review summarizes information of use to forest managers who design cutting regimes that mimic natural disturbances and who must consider forest structure, forest climate, and the role of natural disturbance in their designs.
Soil organic matter (SOM) and soil organic carbon (SOC) constitute usually a small portion of soil, but they are one of the most important components of ecosystems. Bulk density (dB or BD) value is necessary to convert organic carbon (OC) content per unit area. Relationships between SOM, SOC and BD were established in weak alkaline clay fractions of agriculture soils in Southeast Anatolia Region in Turkey. The importance of such relationships results from using sample and rapid techniques to estimate SOC-BD and SOM-BD relationships. Between SOM and SOC, the positive strongest relationship for three models (R 2=0.9976; 0.9982; 94.64) were detected. For SOM-BD and SOC-BD, negative relationship for three models were determined (R 2=0.1342; 0.1420; 0.1329 and R 2=0.1266; 0.1252; 0.1378 respectively). The mismanagement and land cultivation in the past and present causes soil degradation. Therefore, the soil organic matter and carbon are now below their potential level. Evaluation of their stocks requires knowledge about BD. BD is affected by factors such as water, aeration status, root penetrate, clay content, texture, land use and management, therefore it is a very important soil parameter.
Land use change is a major threat to biodiversity. One mechanism by which land use change influences biodiversity and ecological processes is through changes in the local climate. Here, the relationships between leaf area index and five climate variables – air temperature, relative humidity, vapour pressure deficit, specific humidity and soil temperature – are investigated across a range of land use types in Borneo, including primary tropical forest, logged forest and oil palm plantation. Strong correlations with the leaf area index are found for the mean daily maximum air and soil temperatures, the mean daily maximum vapour pressure deficit and the mean daily minimum relative humidity. Air beneath canopies with high leaf area index is cooler and has higher relative humidity during the day. Forest microclimate is also found to be less variable for sites with higher leaf area indices. Primary forest is found to be up to 2.5 °C cooler than logged forest and up to 6.5 °C cooler than oil palm plantations. Our results indicate that leaf area index is a useful parameter for predicting the effects of vegetation upon microclimate, which could be used to make small scale climate predictions based on remotely sensed data.
Quantitative data on patterns of distribution and diversity of grasslands is necessary for conservation planning and sustainable utilization. This is the first study to document and analyse the phytosociological data of grasslands of entire Rajasthan state, India. The data was collected through stratified random sampling method by laying 515 sample plots. The study found 375 species belonging to 188 genera and 46 families. Species diversity (Shannon-Weiner diversity) in seven grassland community types ranged between 2.59 and 3.18. The highest Shannon-Weiner diversity index (H'= 3.18) was found in Aristida-Dichanthium grassland followed by Sehima-Apluda grassland (H' = 3.17). The Simpson diversity index and Similarity index are quite different from each other reveals the uniqueness of these grasslands types. Based on our analysis we are concluding that, saline grasslands and swampy grasslands are narrow-niched and ecologically unique. Analysis showed grasslands of Rajasthan as highly species diverse communities and requires prioritization in the long term conservation planning.
We studied the species diversity of the herb layer and ecological factors in harvest-created gaps in beech stands under a single-tree selection system in Northern Iran. To determine diversity, the number of beech seedlings, and other ecological factors, 16 gaps were selected and subplots of 5 m2 were positioned at the centre and at the cardinal points of each gap. Species richness and Simpson diversity index increased with increasing gap area as did numbers of seedlings. With increasing humus layer thickness, species richness declined but the Hill evenness index increased. Species richness increased with increasing light availability. There was no relationship between crown radii of beech trees and diversity indices. Correlations between environmental factors and numbers of individuals of some species in the herb layer were not significant except in a few cases. The results help explain the effects of man-made gaps on the dynamics of managed beech stands and this benefits evaluation of silvicultural operating plans.
Because of their overwhelming size over other organisms, trees define the structural and energetic properties of forest ecosystems. From grasslands to forests, leaf area index, which determines the amount of light energy intercepted for photosynthesis, increases with increasing canopy height across the various terrestrial ecosystems of the world. In vertically well-developed forests, niche differentiation along the vertical gradient of light availability may promote species coexistence. In addition, spatial and temporal differentiation of photosynthetic traits among the coexisting tree species (functional diversity) may promote complementary use of light energy, resulting in higher biomass and productivity in multi-species forests. Trees have evolved retaining high phenotypic plasticity because the spatial/temporal distribution of resources in forest ecosystems is highly heterogeneous and trees modify their own environment as they increase nearly 1,000 times in size through ontogeny. High phenotypic plasticity may enable coexistence of tree species through divergence in resource-rich environments, as well as through convergence in resource-limited environments. We propose that the breadth of individual-level phenotypic plasticity, expressed at the metamer level (leaves and shoots), is an important factor that promotes species coexistence and resource-use complementarity in forest ecosystems. A cross-biome comparison of the link between plasticity of photosynthesis-related traits and stand productivity will provide a functional explanation for the relationship between species assemblages and productivity of forest ecosystems.
Herb layer contributes substantially to the species diversity of forests and responds relatively quickly to changes in the environment. The objectives of the present study were to understand the relationships among tree canopy cover, soil moisture, light intensity, herbaceous diversity and biomass in a dry tropical forest of India. For this, 20 locations equally distributed in four sites were selected. Four quadrats, each 1 × 1 m in size, were randomly placed for sampling at each location. For each quadrat, tree canopy cover, incident light, soil moisture, herbaceous diversity, and biomass were determined. Results indicated that the selected locations differed in terms of tree canopy cover, soil moisture, light intensity, herbaceous diversity, and biomass. Principal component analysis (PCA), using importance value indices of the component species yielded four groups corresponding to the four communities. PCA axes were related to the tree canopy cover, light intensity, and soil moisture and suggested that these variables had a profound effect on the organization and determination of herbaceous floristic composition and diversity. Positive relationships of tree canopy cover with soil moisture, herbaceous diversity and biomass, and those of soil moisture with herbaceous diversity and biomass suggested that the tree canopies facilitated the herbaceous communities by modifying environmental conditions that ultimately improved the diversity and production. Further, the study showed a linear relationship of herbaceous diversity with biomass, indicating the importance of species diversity for generating primary production in forest herbs.
Abstract Measurement,guidelines for forest carbon,sequestration,were,developed,to support reporting by public and,private entities to greenhouse,gas registries. These guidelines are intended,to be a reference for designing,a forest carbon,inventory and,monitoring,system,by professionals with a knowledge of sampling, statistical estimation, and forest measurements. This report provides guidance on defining boundaries; measuring, monitoring, and estimating changes,in carbon stocks; implementing,plans to measure,and,monitor carbon; and developing,quality assurance,and quality control plans to ensure credible and,reproducible estimates of the carbon credits. Expected users include entities, e.g., individual landowners, industrial forestry companies and managers of utility company lands, within the United States who,are interested in implementing,forestry activities and projects designed,to generate carbon credits that could be traded as an offset, or for registering carbon dioxide reductions using the U.S. Department,of Energy 1605(b) voluntary reporting registry. The Authors TIMOTHY R.H. PEARSON and SANDRA L. BROWN are scientists with Winrock
We review patterns of plant species richness with respect to variables related to resource availability and variables that have direct physiological impact on plant growth or resource availability. This review suggests that there are a variety of patterns of species richness along environmental gradients reported in the literature. However, part of this diversity may be explained by the different types and lengths of gradients studied, and by the limited analysis applied to the data. To advance in understanding species richness patterns along environmental gradients, we emphasise the importance of: (1) using variables that are related to the growth of plants (latitudinal and altitudinal gradients have no direct process impact on plant growth); (2) using multivariate gradients, not single variables; (3) comparing patterns for different life forms; and (4) testing for different shapes in the species richness response (not only linear) and for interaction between variables.
Despite a growing awareness that the herbaceous layer serves a special role in maintaining the structure and function of forests, this stratum remains an underappreciated aspect of forest ecosystems. In this article I review and synthesize information concerning the herb layer's structure, composition, and dynamics to emphasize its role as an integral component of forest ecosystems. Because species diversity is highest in the herb layer among all forest strata, forest biodiversity is largely a function of the herb-layer community. Competitive interactions within the herb layer can determine the initial success of plants occupying higher strata, including the regeneration of dominant overstory tree species. Furthermore, the herb layer and the overstory can become linked through parallel responses to similar environmental gradients. These relationships between strata vary both spatially and temporally. Because the herb layer responds sensitively to disturbance across broad spatial and temporal scales, its dynamics can provide important information regarding the site characteristics of forests, including patterns of past land-use practices. Thus, the herb layer has a significance that belies its diminutive stature.
This study describes the biomass and net primary productivity of the forests of Central Himalaya occurring in areas where vegetation ranges from close-canopy broad-leaved forest to stunted open-canopy timberline vegetation. The forests studied were Acer cappadocicum forest at 2750 m, Betula utilis forest at 3150 m, and Rhododendron campanulatum forest at 3300 m altitude in Central Himalaya. With the rise in altitude the forest biomass decreased from 308.3 ton/ha in Acer forest to 40.5 ton/ha in Rhododendron forest. The decrease in net primary productivity was less steep, from 19.6 ton/ha/yr in Acer forest to 10.0 ton/ha/yr in Rhododendron forest. The production efficiency of leaves (net production per unit leaf weight) in these forests is higher than in low altitude broad-leaved forests of Central Himalaya, i.e. from 2.89 in Acer forest to 3.41 g net production/g leaf biomass/yr, against 0.81-1.55 at lower altitudes.
Physiographic factors along with edaphic conditions play a crucial role in establishment of plant species throughout a region. Identification of the most effective factors is of high importance in sustainable management of a forest ecosystem. This study aims to investigate the relationships between understory vegetation and some environmental factors in natural forest ecosystems. This study has been carried out among the Fagetum orientalis communities of Ramsar Region, located in the north of Iran. For this purpose, 105 releves were sampled by a randomized-systematic method throughout the study area, using the Braun-Blanquet scale. Physiographic parameters such as elevation, as well as slope and orientation were measured. By identification of the herb-layer vegetation contained in each sampling, vegetation composition and cover abundance of species were separately identified. Then, the aforementioned properties of soil were entirely measured in the taken samples. Cluster analysis and detrended correspondence analysis have been applied to classify the site. Moreover, in order to determine the relation between species composition and environmental factors, canonical correspondence analysis was used. Results showed a significant relation between distribution of plant types and environmental factors. Eventually, environmental factors including slope, orientation, silt percent, pH, organic matter, soluble phosphorous were among the most effective factors in establishment of Hedera pastuchowii, Solanum kieseritzkii, Oplismenus undulatifolius, Sedum stoloniferum, Rubus hyrcanus and Saxifraga cymbalaria species.
Rates of key soil processes involved in recycling of nutrients in forests are governed by temperature and moisture conditions and by the chemical and physical nature of the litter. The forest canopy influences all of these factors and thus has a large influence on nutrient cycling. The increased availability of nutrients in soil in clearcuts illustrates how the canopy retains nutrients (especially N) on site, both by storing nutrients in foliage and through the steady input of available C in litter. The idea that faster decomposition is responsible for the flush of nitrate in clearcuts has not been supported by experimental evidence. Soil N availability increases in canopy gaps as small as 0.1 ha, so natural disturbances or partial harvesting practices that increase the complexity of the canopy by creating gaps will similarly increase the spatial variability in soil N cycling and availability within the forest.
Canopy characteristics affect the amount and composition of leaf litter produced, whichlargely determines the amount of nutrients to be recycled and the resulting nutrient availability. Although effects of tree species on soil nutrient availability were thought to be brought about largely through differences in the decomposition rate of their foliar litter,recent studies indicate that the effect of tree species can be better predicted from the mass and nutrient content of litter produced, hence total nutrient return, than from litter decay rate. The greater canopy complexity in mixed species forests creates similar heterogeneity in nutritional characteristics of the forest floor.
Site differences in slope position, parent material and soil texture lead to variation in species composition and productivity of forests, and thus in the nature and amount of litter produced.Through this positive feedback,the canopy accentuates inherent differences in site fertility.
Plant development and distribution in areas with seasonal rainfall are often related to the ability of plants to postpone
desiccation or tolerate low water potentials during drought. Regeneration of Shorea robusta Gaertn. (sal), a commercially valuable, widely distributed tree of the Indian tropical belt, is unsuccessful at the base
of the Himalaya. Seedling shoots die back repeatedly during the long drought that follows the monsoon rain. During the course
of one year, we monitored changes in plant and soil water potentials (Ψ), leaf conductance (gw), osmotic and elastic adjustment, and xylem conductance of sal seedlings of different sizes from three landforms: an alluvial
plain at 540 m elevation, a slope at 510 m, and a montane site at 1370 m. Predawn plant Ψ and gw were lowest in the smallest seedlings (< 20 cm tall). Across sites and seasons, seedlings > 100 cm tall had higher morning
gw than seedlings in the other size classes. In all size classes, plant Ψ was lowest during early summer, when leafing begins.
Among sites, Ψ and gw were lowest in seedlings at the montane site. Osmotic potential was lowest during leaf development and highest during the
rainy season, and tissue elasticity was highest during winter. As leaf area increased during leaf development, xylem conductance
per unit of xylem cross-sectional area also increased. We conclude that low Ψ is unlikely to be a major cause of seedling
mortality. Small seedlings, with low Ψ, had low leaf conductance. Adjustments of osmotic and elastic properties appear to
aid responses of seedlings to drought.
The main objective of the study was to investigate influence of Nepalese alder (Alnus nepalensis D. Don) on fine root biomass (diameter ≤ 2 mm) dynamics and the physical and chemical properties of the soil in white oak (Quercus leucotrichophora A. Camus) forests. Five representative stands of each oak mixed alder (OMA) and oak without alder (OWA) were selected along the stand development gradient in the Indian central Himalaya. Fine root and soil samples from of 0–10 cm, 10–20 cm, and 20–30 cm depths were collected using soil core method. Soil physical and chemical properties and monthly variations in fine root dynamics (biomass distribution and decomposition) were analyzed. Fine root decomposition was studied by using the litterbag technique. Redundancy and correlation analyses were performed to evaluate the relationship between fine root dynamics, stands, and tree total basal area and soil properties. Both the fine root biomass and production of Q. leucotrichophora were significantly (P < 0.05) higher for oak without alder stands than oak mixed alder stands. Fine root biomass, production, and turnover rate of A. nepalensis were significantly (P < 0.05) higher than Q. leucotrichophora in oak mixed alder stands. Within the investigated soil profile, in all the sites, maximum fine root biomass and production were found in the upper (0–10 cm) soil depths. The analyses revealed clear differences in all the measured soil physical and chemical properties and fine root traits in oak mixed alder and oak without alder stands. The soil organic carbon (SOC), total nitrogen (TN) contents, and soil C and N stocks were significantly (P < 0.05) higher in oak mixed alder stands than oak without alder stands while opposite trends were found for soil pH and bulk density (BD). Present findings reveal that improvement of the soil properties under oak mixed alder stands was significantly higher than the oak without alder stands. Fine root decomposition for A. nepalensis was significantly faster than Q. leucotrichophora. Q. leucotrichophora fine roots in OMA stands decomposed at significantly faster rates compared to OWA stands. Additionally, the present study suggests that variation, in fine root dynamics across the forest stands was not only positively correlated to the soil physical and chemical properties but also highly dependent on the forest stand characteristics.
Plant invasion has been a major threat to biodiversity and ecosystem stability. In the present study, we have estimated the effect of two invasive alien species, Lantana camara and Ageratina adenophora on the understory vegetation composition and species diversity of chir pine (Pinus roxburghii) forests in the central Himalaya. We have selected three sites in pine forests and each site was divided into three subsites i.e. non-invaded (NI), Lantana camara invaded (LI) and Ageratina adenophora invaded (AI). In each subsite, 10 random quadrats for herbs (1 × 1 m) and shrubs (5 × 5 m) were laid down. In all the study sites, native herbs and shrubs species richness, diversity, and evenness changed due to invasive species. The presence of both the invasive species caused a reduction in native understory herbs and shrubs species number by 29–40% indicating a strong effect on native vegetation. Shrub density ranged from 6720 to 9680 individuals ha⁻¹ and 8960 to 12000 individuals ha⁻¹ in LI and AI sites, respectively. Total shrub basal area varied between 1.64 and 2.52 m² ha⁻¹ in LI sites and 1.76 and 2.24 m² ha⁻¹ in AI sites. Shrub density and basal area in NI sites (4200–6960 individual ha⁻¹ and 0.60–0.96 m² ha⁻¹) were 2–3 times lower than LI and AI sites. Higher shrub density and basal area in LI and AI sites altered the vegetation composition and diversity of understory vegetation in pine forests. The dominance of invasive species also altered the soil physico-chemical properties. Their interrelationship among species assemblage, study sites and environmental variables showed the adverse impact of invasion on native species. This depletion of native flora is worrisome for both ecological as well as socio-economical perspectives and needs urgent attention of forest managers and policymakers.
Plant community composition and functional traits respond to chronic drivers such as climate change and nitrogen (N) deposition. In contrast, pulse disturbances from ecosystem management can additionally change resources and conditions. Community responses to combined environmental changes may further depend on land-use legacies. Disentangling the relative importance of these global change drivers is necessary to improve predictions of future plant communities. We performed a multi-factor global change experiment to disentangle drivers of herbaceous plant community trajectories in a temperate deciduous forest. Communities of five species, assembled from a pool of fifteen forest herb species with varying ecological strategies, were grown in 384 mesocosms on soils from ancient forest (forested since at least 1,850) and post-agricultural forest (forested since 1950) collected across Europe. Mesocosms were exposed to two-level full-factorial treatments of warming, light addition (representing changing forest management) and N enrichment. We measured plant height, specific leaf area (SLA), and species cover over the course of three growing seasons. Increasing light availability followed by warming reordered species towards a taller herb community, with limited effects of N enrichment or the forest land-use history. Two-way interactions between treatments and incorporating intraspecific trait variation (ITV) did not yield additional inference on community height change. Contrastingly, community SLA differed when considering ITV along with species reordering, which highlights ITV's importance for understanding leaf morphology responses to nutrient enrichment in dark conditions. Contrary to our expectations, we found limited evidence of land-use legacies affecting community responses to environmental changes, perhaps because dispersal limitation was removed in the experimental design. These findings can improve predictions of community functional trait responses to global changes by acknowledging ITV, and subtle changes in light availability. Adaptive forest management to impending global change could benefit the restoration and conservation of understorey plant communities by reducing the light availability.
Woody encroachment is occurring globally; however, the tropical grassy ecosystems, which dominate Africa, are particularly vulnerable to this phenomenon. Encroached ecosystems experience significant changes in biodiversity, ecosystem functioning and service provisioning. One such vital ecosystem service is the provisioning of grazing. As encroachment can reduce grass production through the shading out of shade-intolerant grasses, there is a need to better predict these impacts particularly, since multiple woody species act as encroachers and little is known on their differential effects. Encroacher species may affect grass production differently, depending on the architecture of their canopies. This study therefore aimed to compare the effects of two structurally different encroaching species (a shrub vs a tree) (Dichrostachys cinerea and Terminalia sericea) on grass biomass. We tested the effects of canopy architectural traits of these two species on grass biomass using field sampling in a savanna conservation area in southern Zimbabwe. Canopy cover was a strong predictor of grass biomass, where increasing canopy cover significantly reduced grass biomass under both species. However, the architecture of the shrub D.cinerea, typified by a large crown diameter and crown height and a small crown base-height, created more shade, which had a significantly greater negative effect on grass biomass than the canopies of T.sericea at the same stem density. Architectural traits are therefore considered useful in predicting impacts of encroaching species on grass biomass. The findings show that encroachment of D.cinerea holds the potential to cause a regime shift from an open system to a closed system as a result of its extensive canopy cover.
The assessment of plant biodiversity specifies adaptability of species and other sets of environmental conditions, which are essential for the growth of an ecosystem. During this study, a total of 92 pla nt species including 15 trees, 9 shrubs and 68 herbs belonging to 34 families and 84 genera were noticed. The quadrates of 10m×10m, 05m×05m and 01m×01m sized were fixed for trees, shrubs and herbs, respectively, inside 15 plots of 50m×50m sized to get density, abundance, relative density, relative frequency and basal area etc. The density and frequency represented the species composition, whereas the importance value index indicated the dominancy of one species over another and besides, Shannon and Simpson's index revealed the species diversity and concentration of dominance, respectively. The Acacia arabica amongst trees, Prosopis juliflora in shrubs and Cynodon dactylon in herbs were found to be the dominant species. Although, the herbs were found dominated over shrubs, followed by trees. The Febaceae amongst trees, Febaceae and Malvaceae among shrubs and Poaceae amid herbs was observed to be the dominant family. This study provides exact information about composition of every plant species at the site, which is essential to make conservational strategies for the preservation and development of plant biodiversity. Abbreviatio ns Used Species density: D Species richness: SR Abundance: A Frequency (%): F Total Basal Area: TBA Relative density (%): RD Relative frequency (%): RF Relative Basal Area (%): RBA Importance Value Index: IVI Species diversity: SD Concentration of dominance: CD
Shade, in ecological sense, is not merely a lack of light, but a multi-faceted phenomenon that creates new and complex settings for community and ecosystem dynamics. Tolerating shade therefore affects plants’ ability to cope with other stressors, and also shape its interactions with surrounding organisms. The aim of this broad review was to map our current knowledge about how shade affects plants, plant communities and ecosystems – to gather together knowledge of what we know, but also to point out what we do not yet know. This review covers the following topics: the nature of shade, and ecological and physiological complexities related to growing under a canopy; plants’ capability of tolerating other stress factors while living under a shade – resource trade-offs and polytolerance of abiotic stress; ontogenetic effects of shade tolerance; coexistence patterns under the canopy – how shade determines the forest structure and diversity; shade-induced abiotic dynamics in understorey vegetation, including changing patterns of irradiance, temperature and humidity under the canopy; shade-driven plant–plant and plant–animal interactions – how shade mediates facilitation and stress, and how it creates differentiated environment for different herbivores and pollinators, including the role of volatile organic compounds. We also discuss the ways how vegetation in understorey environments will be affected by climate change, as shade might play a significant role in mitigating negative effects of climate change. Our review shows that living under a shade affects biotic and abiotic stress tolerance of plants, it also influences the outcomes of both symbiotic and competitive plant–plant and plant–animal interactions in a complex and dynamic manner. The current knowledge of shade-related mechanisms is rather ample, however there is much room for progress in integrating different implications of the multifaceted nature of shade into consistent and integral understanding how communities and ecosystems function.
Bulk density values established by the volume excavation method were significantly lower than core sampling values at 2 of 3 locations. The differences in bulk densities generated by the two techniques should be considered when evaluating the severity of compaction on a site relative to an assumed critically limiting bulk density. Core sampling is a simple, fast and common technique, but is not suitable for sampling rocky, dry or wet soils. The volume excavation methods requires simple to use and inexpensive tools and was useful for sampling soils of various conditions, but this technique required greater care and time. -from Authors
A comparison was made of several cumulative species/cumulative individuals indices using a statistical distribution corresponding to the species of insects in a sample from the herb stratum of a lespedeza field. Criteria used in comparison were that the indices be intensive for a given universe regardless of sample size and that the indices differentiate between universes having different numbers of species for a given number of individuals. Species/log individuals, species--1/natural log of individuals, log species/log individuals, and species/square root of individuals were examined. Only the index of species/square root of individual met both of the criteria.
Progress in understanding the patterns of plant diversity requires a conceptualization and quantification of the hierarchy of patch configuration that exists in plant communities across levels of observation. In order to identify the scales at which vascular plant diversity is maximized, we investigated the hierarchical organization of understory vascular plant diversity in relation to canopy patch types in mature boreal mixedwood forests in western Canada. In each of two study areas within a 30 km2 landscape (55° N, 112° E) we sampled four canopy patch types: conifer, mixed conifer-broadleaf, broadleaf and canopy gaps. Understory diversity (richness and Shannon’s (H′) index) was additively partitioned in relation to these four canopy patch types across a hierarchy of four scales; α-individual patch + β1-among patches within canopy patch type + β2-among canopy patch types within area + β3-between areas. We also examined understory species abundance patterns by means of rank-abundance plots fitted to relative abundance models. The largest partition of species richness was among patches within canopy patch type (β1). For Shannon diversity index, the largest partition was at the within-individual patch level (α1) indicating that evenness was high at the patch level but that dominance increased at higher levels in the hierarchy. The assessment of relative abundance by means of rank abundance plots suggested that the canopy patch types differed in terms of the ecological mechanisms influencing diversity patterns. Considering plant diversity within a hierarchical framework is critical for the understanding and management of biodiversity as maximum levels of plant richness and evenness do not necessarily occur at the same observational scales. Management practices which retain the natural hierarchies of vegetation patches will help conserve plant community richness and diversity.
Information content may be used as a measure of the diversity of a many-species biological collection. The diversity of small collections, all of whose members can be identified and counted, is defined by Brillouin's measure of information. With larger collections it becomes necessary to estimate diversity; what is estimated is Shannon's measure of information which is a function of the population proportions of the several species. Different methods of estimation are appropriate for different types of collections. If the collection can be randomly sampled and the total number of species is known, Basharin's formula may be used. With a random sample from a population containing an unknown number of species, Good's method is sometimes applicable. With a patchy population of sessile organisms, such as a plant community, random samples are unobtainable since the contents of a randomly placed quadrat are not a random sample of the parent population. To estimate the diversity of such a community a method is proposed whereby the sample size is progressively increased by addition of new quadrats; as this is done the diversity of the pooled sample increases and then levels off. The mean increment in total diversity that results from enlarging the sample still more then provides an estimate of the diversity per individual in the whole population.
Present study was made on the foot hill, slope (middle hill) and top of the protected and unprotected hills of the Aravalli at Jaipur (26o 49'N, 75o 48'E, 436 m.s.l.). Herbaceous vegetation was therophytic in nature, exhibiting maximum number of species during rainy season. The biomass of herbaceous vegetation at the unprotected hill sites (264- 462 g m-2) was higher than protected hill sites (201-338 g m-2). Annual net primary production was: protected hill, 430-587 g m-2; unprotected hill, 283-613 g m-2. Nitrogen and phosphorus contents in the plant biomass varied from 2725-7723 mg m-2 and 364-795 mg m-2 respectively. The present study revealed an increase in the soil nutrients and species diversity at the protected hill and role of herbaceous vegetation in the conservation of nutrients at both hills. Resumen: El presente estudio se llevó a cabo en el piedemonte, la pendiente media y la cima de las colinas protegidas y no protegidas de Aravalli, Jaipur (26o 49'N, 75o 48'E, 436 m s.n.m.). La vegetación herbácea tuvo una naturaleza terofítica y el número máximo de especies se mostró durante la estación lluviosa. La biomasa de la vegetación herbácea en los sitios no protegidos de las colinas (264-462 g m-2) fue mayor que en los sitios protegidos (201-338 g m-2). La producción primaria neta anual fue: colina protegida, 430-587 g m-2; colina no protegida, 283-613 g m-2. Los contenidos de nitrógeno y fósforo en la biomasa vegetal variaron de 2725- 7723 mg m-2 a 364-795 mg m-2, respectivamente. Este estudio reveló que existe un incremento en los nutrientes del suelo y en la diversidad de especies en las colinas protegidas, y mostró el papel de la vegetación herbácea en la conservación de los nutrientes en las colinas en ambas condiciones.
Quartzite ridges in the Delhi region include in their local depressions thick piles of unconsolidated, unstratified, yellowish brown, homogenous loamy sediments. These Delhi ridge sediments (DRS) have textural, mineralogical and geochemical characteristics similar to those of loess sediments. Geochemically, DRS, just as other loess sediments, are similar to average exposed upper continental crust of Taylor and McLennan [Taylor, S.R., McLennan, S.M., 1985. The Continental Crust: Its Composition and Evolution. Blackwell, London, 311 pp.]. The calculated chemical index of alteration [Nesbitt, H.W., Young, G.M., 1984. Prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations. Geochim. Cosmochim. Acta 54, 1523–1534; Nesbitt, H.W., Young, G. M., 1989. Formation and diagenesis of weathering profiles. J. Geol. 97, 129–147.] and other chemical parameters suggest a provenance of chemically less weathered rocks. During the process of wind transport and deposition, not only the dilution effect of silica on the REE abundance was counterbalanced but also the REE pattern was kept similar to the UCC and PAAS by the appropriate concentration and mixing of the REE bearing phases. The immediate source to these sediments is likely to be mechanically ground sediments of glacial origin. The last phase of the upliftment of the Himalayas, accompanied by Pleistocene glaciation could have provided a vast glacio–fluvial outwash plain. The aeolian processes associated with prevailing W to SW winds in the hot arid condition seem to have been selectively transporting fertile silt materials leaving behind infertile desert sands.
In this study we examine the facilitative effect of Cori- aria nepalensis Wall. verns. at two contrasting sites, a severely eroded hill slope consisting of loose material and a stable hill with normal soil cover (forest). The facilitative effect was measured in terms of species richness and growth of herbs associated with the nurse species. The beta-diversity was more at the open microsite than below-canopy microsite. At the eroded site, the herb density was greater in the open than below the Coriaria canopy. The ameliorative effect of Coriaria bush at the eroded site was dramatic in terms of herb biomass. Our study shows a strong facilitative effect of Coriaria in the harsh environment of the hill slope with severely eroded surface. The facilitative effect is reflected in terms of signif i- cantly higher alpha-diversity and biomass of herbs growing below Coriaria than those growing in the open. The facilitative effect of Coriaria, however, is not manifested at the favourable forest site. The bush showed several ameliorative effects on the eroded site, including higher rate of soil build-up and accumula- tion of nutrients and organic matter leading to an increase in soil water potential. The ability of Coriaria plants to nurse herbs can be used to stabilize hill slopes, to regenerate them and to promote species diversity.
In temperate deciduous forests, the herb layer contributes most to total vascular plant species richness. The diversity of the tree layer can influence herb layer diversity by modifying resource availability and environmental conditions relevant to herb layer plants. Here, we explore the relationship between tree layer diversity and herb layer species richness and cover. Also, we address the question how different environmental factors that are potentially modified by the tree layer influence herb layer characteristics. Our study area is located in the Hainich National Park, one of the largest continuous stretches of broad-leaved deciduous forest in Central Europe. We recorded herb and tree layer composition on 79 plots selected along a tree diversity gradient ranging from two to nine tree species. In addition, canopy cover, soil pH, mass of the humus layer, soil C:N ratio, soil moisture and distance to the forest edge were determined. We used generalized least square models to analyse effects of tree diversity, environmental variables, and spatial plot positions on herb layer species richness and cover. Species richness and cover of the herb layer increased with increasing tree diversity. In addition, both species richness and cover showed a negative response to increasing canopy cover and mass of the humus layer. Herb layer species richness was also positively related to increasing soil pH and the distance to the forest edge. The proportion of forbs increased with increasing tree diversity, whereas the proportion of tree saplings decreased and the proportion of graminoids was not affected. The proportion of true forest species increased with increasing canopy cover. We conclude that forest stands with a high tree diversity feature a more diverse herb layer and a higher herb cover. Furthermore, the environmental variables humus layer mass, light availability and pH also strongly affect herb layer species richness and cover.
The most important unsolved problems of the Kjeldahl method for total nitrogen are concerned with digestion conditions. The quantity of sulfuric acid used in comparison to the size of sample, and the amount of added salt, are factors of importance. Addition of extra sulfuric acid during digestion is often desirable. Mercury is the most effective catalyst for digestion of proteins and usually cannot be satisfactorily replaced by selenium, which must be kept under constant control. Oxidizing agents, except hydrogen peroxide, should be used only with the greatest care. Length of digestion after clearing requires further attention. The milligram scale Kjeldahl method is recommended for general application. The ultramicromethod, in which the ammonia is separated by diffusion, is convenient and suitable for many small scale uses. Significant developments in reducing the size of sample into the submicrogram range are to be expected, through use of the spectrophotometer equipped with capillary cells, and improvements in spectrophotometric instrumentation.
Information on changes in the herb layer of unmanaged forest nature reserves may be useful to assess present-day issues of management relating to sustainability and biodiversity in forestry and nature conservation. Selected floristic and vegetation studies from forest nature reserves in the German states of Lower Saxony and Hesse showed that the number of vascular plant species was higher in forests that are managed than in completely unmanaged forests. Species richness declined significantly during a ten-year period after the active management of the forest reserves had stopped. In both cases, species richness was related to non-forest plant species that depend on high light intensity and soil disturbances. Beech (Fagus sylvatica) became dominant in unmanaged forests due to its high shade tolerance, providing it with a competitive advantage over most other species. However, after large-scale disturbances such as windthrow, species richness increased again even in unmanaged forests.
Grain size analysis is an essential tool for classifying sedimentary environments. The calculation of statistics for many samples can, however, be a laborious process. A computer program called GRADISTAT has been written for the rapid analysis of grain size statistics from any of the standard measuring techniques, such as sieving and laser granulometry. Mean, mode, sorting, skewness and other statistics are calculated arithmetically and geometrically (in metric units) and logarithmically (in phi units) using moment and Folk and Ward graphical methods. Method comparison has allowed Folk and Ward descriptive terms to be assigned to moments statistics. Results indicate that Folk and Ward measures, expressed in metric units, appear to provide the most robust basis for routine comparisons of compositionally variable sediments. The program runs within the Microsoft Excel spreadsheet package and is extremely versatile, accepting standard and non-standard size data, and producing a range of graphical outputs including frequency and ternary plots. Copyright © 2001 John Wiley & Sons, Ltd.