In temperate forests, wind throw often creates canopy gaps which can dramatically change the micro climate and soil water balance. The main focus of this thesis is to understand the spatio-temporal dynamics of the microclimatic conditions in gaps and the sub-canopy in broadleaved deciduous forests. This was achieved by applying a combination of numerical modelling and remote sensing techniques. An analysis of the effects of canopy gap size on microclimate and soil water content was conducted in a semi-natural broadleaved deciduous forest, Eaves Wood, located in North West England. The results showed that solar radiation, air temperature, soil temperature and soil water content significantly increased with gap size; air humidity was consistently lower in gaps than the sub-canopy but did not vary with gap size. However, the variability of wind speed could not be explained by the presence or size of gaps. A spatially explicit model of forest gap microclimate and soil water balance, FORGAP-BD (FORest GAP - Broadleaved Deciduous) was developed based on previous reviewed literatures and field measurements. The spatial input variables for FORGAP-BD such as leaf area index, land surface elevation, gap and canopy properties and canopy radiation extinction coefficient were derived from LiDAR and multi spectral remotely sensed data. A preliminary study demonstrated the effectiveness of combining numerical modelling and remote sensing approaches for analysis of the spatio-temporal variability of forest microclimate and soil water balance. Refinements were made to the methodologies for extracting canopy and gap properties using LiDAR and multi spectral data, in order to improve the gap microclimate and soil water content simulations. The outputs of the FORGAP-BD model were then validated using in situ data collected at Eaves Wood, U.K. The results demonstrated that FORGAP-BD driven by remotely-sensed inputs was able to accurately simulate the diurnal fluctuations and spatial distribution of solar radiation, air temperature, relative humidity, wind speed and soil water content across the study site. Multi-temporal LiDAR data were used to characterise the dynamics of gaps over a ten year period for a broadleaved deciduous forest, Frame Wood, U.K. The dominance of the process of gap contraction by lateral crown expansion was revealed. The spatial outputs from the multi-temporal remotely-sensed data were used to drive the FORGAP-BD model in order to assess the influence of gap dynamics on micro climate. The effects of different types of gap and canopy change were examined. Importantly, by linking gap properties and their influences upon microclimates this research has generated a potentially valuable tool for understanding the consequences of gap dynamics on a range of abiotic and biotic properties and processes. Hence, the approach developed here provides the basis on which to assess the implications of forestry and conservation practices and natural or anthropogenic disturbances in temperate forest ecosystems.

Woodlands represent refugia for wildlife within the intensive agricultural landscape of rural Britain but over the last century these ecosystems have become highly fragmented, exposing woodland specialist species to a range of threats. Management for pheasant shooting affects 14% of all woodland area in Britain and is often promoted as a way to reconcile sporting interests with conservation. However, the implications of pheasant release and the associated management for ecosystems are not well understood. I examined this issue by quantifying the effects of pheasant release and the associated management on the abundance and diversity of small mammal and breeding bird populations within game-managed woodlands. I found no evidence to suggest that pheasants impacted woodland ecosystems directly. However, the management practices associated with pheasant release did affect native vertebrates. In autumn, wood mice were more abundant near pheasant release pens, perhaps in response to increased resource levels and/or release from predation pressure within the pen. Common shrews decreased near release pens in autumn, potentially as a result of habitat disturbance.

Mycorrhizal mutualisms between aboveground vascular plant communities, which reward their belowground fungal associates with photosynthates in return for growth-limiting nutrients such as phosphate, are widely recognized as stable long-term interactions which helped plants colonize land. Pezoloma ericae (D.J. Read) Baral, an ascomycete mycorrhiza-forming fungus present amongst plants in the Ericales, such as heathers, also forms associations in several families of non-vascular leafy liverworts. Whether there is a mutually beneficial functional relationship between these leafy liverworts and the fungus growing in their rhizoids was previously unconfirmed. Furthermore, an ecological role of this 'shared' mycobiont and its link between vascular (Ericaceae) and non-vascular (liverworts) plants was also unknown. Thus the main questions asked in this dissertation are: 1) Is there a measurable mutually beneficial relationship between a liverwort and its fungal partner?; and, 2) Can liverworts harbouring the ericoid mycorrhiza P. ericae act as inoculum that facilitates the re-establishment of Ericaceae - and henceforth be proposed as a practical tool in a restoration ecology context. This is the first time British species of leafy liverworts are conclusively identified to harbour the ericoid mycorrhizal fungus Pezoloma ericae using molecular identification. I have demonstrated a mutualism occurring between the leafy liverworts and their fungal symbiont in two independent microcosm growth experiments and confirmatory reciprocal trophic exchanges between phosphorus and carbon and the two organisms. Glasshouse experiments demonstrated P. ericae originating from leafy liverwort rhizoids, can repeatedly colonize Ericaceae plant roots. Under realistic ecological circumstances (further tested at two field sites), liverworts delivered mycorrhizal inoculum and improved the resilience and growth of vascular plants. By providing this novel source of mycorrhizal inoculum, symbiotic non-vascular plants can contribute to the restoration of plant communities dominated by Ericaceous plants. This research leads to broader knowledge about the function of ericoid mycorrhizas in ecosystems with multi-trophic non-vascular-fungi-vascular community interactions, both above and below ground.

1. Long-term patterns of natural regeneration, growth, mortality and disturbance were recorded in six native lowland woods around Britain, using a series of permanent transects/plots established during the 1950-80s. Records were made including the position and status of trees, shrubs, established seedlings, dead wood and canopy gaps. 2. The stands inherited various original-natural features and grew away from a managed state. Nonetheless, their structure and composition remained heavily influenced by past treatment and non-native species. 3. The natural development of five woodland types and twelve tree and shrub species was reviewed and four general stages of stand development were recognised. 4. The major processes controlling stand development were: (i) exclusion; (ii) damage caused by wind, drought, large herbivores and grey squirrels; and (iii) regeneration and release below part-broken stands and within/around larger canopy gaps. 5. The main structural changes identified during stand development were: (i) an increase in basal area to a maximum of c.30-50m² ha^-1; (ii) a decline in stem density until understorey reinitiation/gap-phase regeneration occurred; (iii) an increase instratification, especially under lighter crowned trees and once reinitiation/regeneration occurred; (iv) a scarcity of canopy gaps until at least 125-150 years growth, after which gap creation tended to be patchy and mainly associated with windstorms and drought,though an extensive blow down was recorded; and (v) a scarcity of dead wood until stands matured and broke-up. 6. Compared to other temperate forests, several distinctive aspects of stand development were recognised, particularly: (i) the role of large herbivores in delaying and altering regeneration; (ii) the importance of debarking by grey squirrels; (iii) the potential for some canopy gaps to fill other than with tree regeneration; (iv) the persistence of the understorey in certain native stand types; and (v) the vulnerability of mature beech stands to sudden and quite extensive collapse.

No description available.

The fixation of atmospheric nitrogen (N) is a major pathway for available N entering ecosystems. In N-limited boreal forests, a significant amount of N is fixed by cyanobacteria that live epiphytically on feather mosses. Despite the dominance of bryophytes in the boreal biome and their association with cyanobacteria, the role of feather mosses in boreal N cycling remains poorly understood. Further, evaluating abiotic controls on N2 fixation in the feather moss-cyanobacteria association is a challenge yet to be addressed. Therefore, the aims of this thesis were to identify the main factors that drive N2 fixation in the feather moss-cyanobacteria association, and to gain a deeper understanding of the feather moss’ role for the N cycle in boreal forests. The effects of natural and artificial N additions, N deprivation as well as the impact of drying and rewetting events on N2 fixation rates in the ubiquitous- and cyanobacteria-hosting feather moss Pleurozium schreberi (Brid.) Mitt. were analyzed. Further, the ability of P. schreberi to take up N from soil was tested, assessing another possible pathway through which the moss can utilize N. The cyanobacterial contribution to the decomposition resistance of the moss was evaluated; and finally, when and how the fixed N enters the soil to become available for plants and microbes was assessed. The results of my work demonstrated that N2 fixation is negatively affected by natural as well as artificial N inputs, but the inhibition of N2 fixation is dependent on the amount of added N and further, N2 fixation seems to be resilient to N deposition as well as to drying-rewetting events indicated by the increase of N2 fixation rates in the moss-cyanobacteria association upon removal of the stressors. P. schreberi was found to be able to take up organic and inorganic N from soil, but it accounted for a small fraction of total N demand. Cyanobacteria do not contribute to the moss’ resistance towards decomposition by soil bacteria. Feather mosses effectively retain the acquired N, thus representing a short-term N sink. By using lab as well as field-based approaches to identify factors that drive N2 fixation in the feather moss-cyanobacteria association, I gained a deeper understanding of a major component of the N cycle in boreal forests. The moss was shown to have the ability to use soil-N and to retain N over several months, however, the moss likely represents a long-term N source to the boreal system, due to its association with N2-fixing cyanobacteria. Nevertheless, assessing the transfer and exchange of N and carbon (C) between feather moss and cyanobacteria, and defining the interface of this, would improve our understanding of their role in ecosystem nutrient cycling and should be subject to future research.

Litter decomposition is a key component in ecosystem C and nutrient cycling. Shrubland litter decomposition is not well understood, even though shrublands cover a significant proportion of earth surface. This project aims to investigate the decomposition of shrubland plant residue (Cistus monspeliensis L.). The first and second experimental chapters of this thesis present the data about root chemistry, C and N mineralisation from the decomposing roots. Root tissue chemistry varies significantly with age, younger roots consist of higher relative amounts of N, P, K, soluble compounds, conversely Ca, hemicellulose, cellulose concentrations are higher in older roots. Faster short-term C, and N mineralisation rates were observed in senescing younger roots compared to the older roots under our experimental conditions. The third experimental chapter is about leaf litter decomposition study using litter bag technique. Accumulated mass loss from the decomposing leaf litter is a biphasic process where initial rapid mass loss followed by relatively slower phase. Among the various leaf litter decomposition parameters lignin: N best explained the accumulated mass loss. Fourth experimental chapter is an attempt to understand the 14C mineralisation process from decomposing soluble and insoluble components of above and below ground plant parts. Soluble components have shown faster 14C mineralisation compared to the insoluble fractions of above (stem and leaf) and belowground (roots) plant components. Belowground plant components have shown a distinctive 14C mineralisation pattern with more % 14C entering in to microbial biomass pool compared to the aboveground components which will have consequences on whole ecosystem C cycle. Results from final experimental chapter indicate that C sourced by hyphal biomass reside longer duration even after death thereby contribute significant amounts of C to the belowground. However, further long-term studies that includes multi plant species under filed conditions are needed before these results extrapolate to the shrubland ecosystem.

A functional ecology approach was combined with floristic studies to seek increased ecological understanding of forest characteristics and processes in the Central Highlands of Chiapas State, Mexico. The study had two main aims: 1) to determine the major ecological factors driving the floristic and functional variation of forest ecosystems, with emphasis on the operation of either environmental (niche model) or spatial (dispersal limitation model) factors and 2) to determine the relationship of leaf-litter decomposition rates to both leaf functional traits and forest conditions. For this, the specific objectives were i), characterise both the dominant species and the forest stands they form using functional traits, determining also the trait-trait and species-trait relationships; ii), characterise the floristic and functional variation amongst forest stands, and the relationship of this variation with spatial and environmental variables; iii) determine the influence of spatial factors, climate variables, anthropogenic disturbance, forest canopy openness and the traits of species on the abundance of saplings and iv), determine the effect of species leaf trait values, forest type, and their interaction, on leaf-litter decomposition. The study area encompassed a narrow altitudinal range from 2100 to 2800 m a.s.l., located on a carboniferous limestone substrate with abrupt topography and a cool and humid climate. For objectives i), ii) and iii), both adult trees and saplings were counted, measured and identified in field plots in four previously-defined forest types –oak forest, pine-oak forest, pine forest and broadleaved forest– at seven study sites. Plots were characterised in terms of spatial location, altitude above sea level and climate variables from Worldclim climate surfaces. Leaf, stem and whole-plant traits, as well as leaf carbon fractions, were measured for dominant species, and saplings were sampled under both closed and open canopies. For objective iv), first, leaf litter decomposition rates of 20 dominant species were measured in a greenhouse experiment for the assessment of trait effects and second, decomposition rates of representative litter from each forest type, plus two standard species, were measured in a field experiment using forest type as the main factor. Forests of the study area are a mosaic in which three main functional groups of species were identified (objective i). Two groups were respectively dominated by Quercus species and Pinus species, which both reach the canopy or sub-canopy layers of the forests and had high wood density, leaf dry matter content (LDMC) and other trait values suggesting relatively slow growth. The third group contained a wide taxonomic range of species that generally develop in the forest understorey and had high specific leaf area, leaf nutrient contents and other trait values suggesting relatively high rates of growth and population turnover. These three functional groups of species form a variety of floristic assemblages, ranging from those of simple structure and low floristic diversity (mostly pine forests) to complex and diverse broad-leaved forests. Most oak and pine-oak forests had intermediate characteristics. Variation partitioning analysis showed that the floristic variation of both adults and saplings was related to climate but also to spatial factors, suggesting an important role of dispersal limitation in the shaping of species assemblages (objectives ii and iii). In contrast, variation partitioning also showed that forest functional characteristics –measured using weighted mean trait values– were strongly linked to human disturbance, suggesting that people have had strong effects on the ecological functions of these forests (objective ii). Additionally, floristic variation among forest stands was not always accompanied by functional variation, suggesting that floristics can change across space while forest functional characteristics remain relatively homogeneous. Regarding objective (iii), leaf area was the only species functional trait with a clear relationship to the absolute densities of saplings, suggesting that the abundance of regeneration increases with increasing leaf area, though the effect of canopy openness was small. Finally, for objective iv), the greenhouse experiment showed that Quercus spp. and Pinus spp. with tough leaves had relatively slow decomposition rates and species with lower LDMC and associated tradeoffs in trait values, such as high specific leaf area, had higher decomposition rates. In the field experiment (objective iv), decomposition rates did not vary significantly between the four different forest types, supporting the hypothesis that persistent leaf characteristics of species, rather than forest functional characteristics and environment, are the most important controls on decomposition. Nevertheless, there was evidence that litter mixtures tended to show higher decomposition rates in forest associations where they were collected, than in other forest associations (the “home-field advantage” hypothesis). This result suggests probable variations in leaf-litter substrates determined by forest functional composition. It is believed that this is the first study to apply a functional traits approach to understanding variation of forest ecological characteristics and processes in Mesoamerican mountains. The study shows that dispersal limitation, as well as environmental and anthropogenic factors, probably influences the characteristics of forest stands, and that the degree of functional variation may be smaller than that of floristic variation. The study demonstrates that leaf trait values of dominant tree species influence litter decomposition rates and therefore, potentially, nutrient cycling. Even though litter decomposition rates in the field were most likely to be affected by leaf and litter characteristics, not forest environment, there was evidence for a home-field advantage effect. In the current era of anthropogenic global change effects on the forests of Chiapas, this work sheds new light on forest function and forest change and has special relevance for the design of conservation strategies for the tropical montane ecosystems.

Biological communities are changing across the globe as a result of anthropogenic pressures; abundances of individuals are declining within populations and species are becoming extinct. Biological diversity and trophic complexity in grasslands and soil food webs are positively associated with the cycling of nutrients in soil and water, primary productivity and decomposition. Since these ecosystem processes underpin a number of goods and services to society, human-driven changes in the structure of ecosystems could negatively impact upon human wellbeing. However, the majority of our knowledge of the role of biodiversity in ecosystem functioning comes from studies conducted in temperate grassland systems. Consequently, our understanding of how of higher-level organisms influence ecological processes in different ecosystems is limited. This thesis aims to address these knowledge gaps by investigating how dung beetle traits and functional diversity influence the secondary dispersal of seeds and the emergence and survival of seedlings in the northeastern Brazilian Amazon. My first research aim was to understand the importance of intraspecific variability in dung beetle traits for the accuracy of functional diversity (FD) indices (Chapter 2). This chapter demonstrates that intraspecific differences in dung beetle traits are small compared to between species differences. However, failure to include intraspecific variability resulted in large errors in the calculation of FD indices when describing small and/or species poor communities. Second, I investigated how dung beetle diversity influences secondary seed dispersal, and the role of environmental context in modulating relationships. Here I reveal positive relationships between dung beetle functional diversity and both the probability of seed burial and the dispersion of seeds throughout the soil profile. However, these patterns were dependant on soil type and thus environmental context (Chapter 3). Finally, I explored the multitrophic significance of findings from Chapter 3 by testing how dung beetle communities affect the burial of different sizes of seeds and emergence and survival of seedlings (Chapter 4). Results from this chapter demonstrate how dung beetles could influence vegetation regeneration because beetle diversity negatively affected the likelihood that experimental seeds emerged from the soil surface, but positively impacted on the likelihood that emerged seeds survived until the end of the experiment period. Furthermore, I show that large seeds could be more vulnerable to anthropogenic driven changes in dung beetle communities than smaller seeds. These research aims were realised through field-based experiments from which I sampled and identified approximately 2,650 dung beetles from 180 naturally formed communities, collected more than 17,000 morphological trait measurements and sieved approximately 11 tonnes of soil in search of 1800 seed mimics. Overall, this work demonstrates diversity in dung beetle communities is positively associated with the ecological processes they govern but that environmental context is instrumental in modulating biodiversity-ecosystem functioning relationships. I use the outcomes from this work to discuss the challenges in describing diversity-functioning relationships across trophic levels. Finally, I highlight that ecological processes are the product of complex species-specific interactions, dependent on the biotic and abiotic environment. Therefore, predicting the consequences of anthropogenic-driven species losses for the structure and functioning of natural systems is a major research challenge.

No description available.