Toby Richard Marthews

UK Centre for Ecology & Hydrology | CEH · Hydroclimate Risks

Wetlands play a key role in hydrological and biogeochemical cycles and provide multiple ecosystem services to society. However, reliable data on the extent of global inundated areas and the magnitude of their contribution to local hydrological dynamics remain surprisingly uncertain. Global hydrological models and land surface models (LSMs) include...

The growth and survival of individual trees determine the physical structure of a forest with important consequences for forest function. However, given the diversity of tree species and forest biomes, quantifying the multitude of demographic strategies within and across forests and the way that they translate into forest structure and function rem...

Wetlands are the largest natural source of methane. The ability to model the emissions of methane from natural wetlands accurately is critical to our understanding of the global methane budget and how it may change under future climate scenarios. The simulation of wetland methane emissions involves a complicated system of meteorological drivers cou...

Soil moisture information is essential to monitoring of the intensity of droughts, the start of the rainy season, planting dates and early warnings of yield losses. We assess spatial and temporal trends of drought over the Brazilian semiarid region by combining soil moisture observations from 360 stations, root zone soil moisture from a leading lan...

Drought is predicted to increase in the future due to climate change, bringing with it myriad impacts on ecosystems. Plants respond to drier soils by reducing stomatal conductance in order to conserve water and avoid hydraulic damage. Despite the importance of plant drought responses for the global carbon cycle and local and regional climate feedba...

Fine roots constitute a significant component of the net primary productivity (NPP) of forest ecosystems but are much less studied than above‐ground NPP. Comparisons across sites and regions are also hampered by inconsistent methodologies, especially in tropical areas. Here, we present a novel dataset of fine root biomass, productivity, residence t...

Tropical forests are the most diverse and productive ecosystems on Earth. While better understanding of these forests is critical for our collective future, until quite recently efforts to measure and monitor them have been largely disconnected. Networking is essential to discover the answers to questions that transcend borders and the horizons of...

Wetlands play a key role in hydrological and biogeochemical cycles and provide multiple ecosystem services to society. However, reliable data on the extent of global inundated areas and the magnitude of their contribution to local hydrological dynamics remain surprisingly uncertain. Global hydrological models and Land Surface Models (LSMs) include...

Timely predictions of fluvial flooding are important for national and regional planning and real-time flood response. Several new computational techniques have emerged in the past decade for making rapid fluvial flood inundation predictions at time and space scales relevant to early warning, although their efficient use is often constrained by the...

A rich understanding of the productivity, carbon and nutrient cycling of terrestrial ecosystems is essential in the context of understanding, modelling and managing the future response of the biosphere to global change. This need is particularly acute in tropical ecosystems, home to over 60% of global terrestrial productivity, over half of planetar...

Drought is predicted to increase in the future due to climate change, bringing with it a myriad of impacts on ecosystems. Plants respond to drier soils by reducing stomatal conductance, in order to conserve water and avoid hydraulic damage. 55 Despite the importance of plant drought responses for the global carbon cycle and local/regional climate f...

The sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such effects translate into long-term responses. Here, we analyze 590 permanent plots measured across the tropics to derive the equilibrium climate contro...

The sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such effects translate into long-term responses. Here, we analyze 590 permanent plots measured across the tropics to derive the equilibrium climate contro...

A series of fire events have captured the attention of the public and press in the last couple of years. South America, for example, saw the largest increase in fire count in nearly 10 years, mainly in areas historically associated with deforestation in Amazonia. Meanwhile, South Eastern Australia has seen a number of devastating bush fires in rece...

Knowledge of how uncertainty propagates through a hydrological land surface modelling sequence is of crucial importance in the identification and characterisation of system weaknesses in the prediction of droughts and floods at global scale. We evaluated the performance of five state-of-the-art global hydrological and land surface models in the con...

Anthropogenically driven declines in tropical savannah burnt area1,2 have recently received attention due to their effect on trends in global burnt area3,4. Large-scale trends in ecosystems where vegetation has adapted to infrequent fire, especially in cooler and wetter forested areas, are less well understood. Here, small changes in fire regimes c...

A severe drought hit the Greater Horn of Africa (GHA) in 2014, but it remains unclear whether this extreme event was attributable to anthropogenic climate change or part of longer-term natural cycles. Precipitation patterns are known to be changing across the GHA, but trajectories in land surface variables are much less well known. We simulated the...

Evapotranspiration (ET) from soil and vegetation is a key part of the energy and water budgets and, with condensation, a process that links both explicitly. Accurate experimental determination of ET is a requirement, but it is challenging both in situ and remotely, introducing uncertainties for model pa- rameterization development and validation. F...

Knowledge of how uncertainty propagates through a hydrological land surface modelling sequence is of crucial importance in the identification and characterisation of system weaknesses in the prediction of droughts and floods at global scale. We evaluated the performance of five state-of-the-art global hydrological and land surface models in the con...

Tropical forests play a major role in the carbon cycle of the terrestrial biosphere. Recent field studies have provided detailed descriptions of the carbon cycle of mature tropical forests, but logged or secondary forests have received much less attention. Here we report the first measures of total net primary productivity (NPP) and its allocation...

Tropical forests play a major role in the carbon cycle of the terrestrial biosphere. Recent field studies have provided detailed descriptions of the carbon cycle of mature tropical forests, but logged or secondary forests have received much less attention. Here we report the first measures of total net primary productivity (NPP) and its allocation...

It is hypothesized that more accurate prediction and warning of natural hazards, such as of the impacts of severe weather mediated through various components of the environment, require a more integrated Earth System approach to forecasting. This hypothesis can be explored using regional coupled prediction systems, in which the known interactions a...

It is hypothesised that more accurate prediction and warning of natural hazards, such as of the impacts of severe weather mediated through various components of the environment, requires a more integrated Earth System approach to forecasting. This hypothesis can be explored using regional coupled prediction systems, in which the known interactions...

Productive forests of the Andes are subject to high erosion rates that supply to the Amazon River sediment and carbon from both recently photosynthesized biomass and geological sources. Despite this recognition, the source and discharge of particulate organic carbon (POC) in Andean Rivers remain poorly constrained. We collected suspended sediments...

Global fire models typically describe fire as a consequence of fuel load, moisture, natural and anthropogenic ignitions, and land use suppression. A lack of information on the temporal and spatial distribution of these controls has meant that their simulated effects on predicting burnt area are largely untested. Despite this, there is a pervasive a...

Atmospheric methane (CH4) accounts for ~20% of the total direct anthropogenic radiative forcing by long-lived greenhouse gases. Surface observations show a pause (1999-2006) followed by a resumption in CH4 growth, which remain largely unexplained. Using a land surface model, we estimate wetland CH4 emissions from 1993 to 2014 and study the regional...

Large-scale mortality events in forests are increasing in frequency and intensity and can lead to both intermediate- and long-term changes in these systems. Specialist pests and pathogens are unique disturbances, as they commonly target individual species that are relatively prevalent in the community. Understanding the consequences of pathogen-cau...

Ensemble modelling of the East African 2014 long rains season suggests no anthropogenic influence on the likelihood of low rainfall but clear signals in other drivers of drought.

Meeting report for the NCBS-Oxford meet, May 2014 in Bangalore

Global change is impacting forests worldwide, threatening biodiversity and ecosystem services including climate regulation. Understanding how forests respond is critical to forest conservation and climate protection. This review describes an international network of 59 long-term forest dynamics research sites (CTFS-ForestGEO) useful for characteriz...

Understanding the relationship between photosynthesis, net primary productivity and growth in forest ecosystems is key to understanding how these ecosystems will respond to global anthropogenic change, yet the linkages among these components are rarely explored in detail. We provide the first comprehensive description of the productivity, respirati...

Modelling land surface water flow is of critical im-portance for simulating land surface fluxes, predicting runoff and water table dynamics and for many other applications of Land Surface Models. Many approaches are based on the popular hydrology model TOPMODEL (TOPography-based hydrological MODEL), and the most important parameter of this model is...

Advances in forest carbon mapping have the potential to greatly reduce uncertainties in the global carbon budget and to facilitate effective emissions mitigation strategies such as REDD+ (Reducing Emissions from Deforestation and Forest Degradation). Though broad-scale mapping is based primarily on remote sensing data, the accuracy of resulting for...

Modelling land surface water flow is of critical importance for simulating land-surface fluxes, predicting runoff and water table dynamics and for many other applications of Land Surface Models. Many approaches are based on the popular hydrology model TOPMODEL, and the most important parameter of this model is the well-knowntopographic index. Here...

Modern land surface model simulations capture soil profile water movement through the use of soil hydraulics sub-models, but good hydraulic parameterisations are often lacking, especially in the tropics. We present much-improved gridded data sets of hydraulic parameters for surface soil for the critical area of tropical South America, describing so...

Background: The slopes of the eastern Andes harbour some of the highest biodiversity on Earth and a high proportion of endemic species. However, there have been only a few and limited descriptions of carbon budgets in tropical montane forest regions. Aims: We present the first comprehensive data on the production, allocation and cycling of carbon f...

Background: The forests of western Amazonia are known to be more dynamic that the better-studied forests of eastern Amazonia, but there has been no comprehensive description of the carbon cycle of a western Amazonian forest. Aims: We present the carbon budget of two forest plots in Tambopata in south-eastern Peru, western Amazonia. In particular, w...

Background: Tropical montane cloud forests (TMCF) are unique ecosystems with high biodiversity and large carbon reservoirs. To date there have been limited descriptions of the carbon cycle of TMCF. Aims: We present results on the production, allocation and cycling of carbon for two mid-elevation (1500–1750 m) tropical montane cloud forest plots in...

Advances in forest carbon mapping have the potential to greatly reduce uncertainties in the global carbon budget and to facilitate effective emissions mitigation strategies such as REDD+. Though broad scale mapping is based primarily on remote sensing data, the accuracy of resulting forest carbon stock estimates depends critically on the quality of...

A mosaic of protected areas, including indigenous lands, sustainable-use production forests and reserves and strictly protected forests is the cornerstone of conservation in the Amazon, with almost 50 per cent of the region now protected. However, recent research indicates that isolation from direct deforestation or degradation may not be sufficien...

Tropical forests play a major role in the global carbon cycle, both as sources of atmospheric greenhouse gases through biomass burning, decomposition and deforestation, and as probable sinks of atmospheric carbon dioxide (CO2) in intact forests. They also harbour over one half of global biodiversity and a quarter of all the biomass and soil carbon...

Despite widespread recognition of the major threat to tropical forest biological diversity and local food security posed by unsustainable bushmeat hunting, virtually no long-term studies tracking the socioecological dynamics of hunting systems have been conducted. We interviewed local hunters and collected detailed hunting data to investigate chang...

The management effectiveness of protected areas is a critically important consideration for their conservation success. Over 40 different protected area management effectiveness (PAME) data collection tools have been developed to systematically assess protected area management effectiveness. Many of these assessments have recently been collated int...

Modern land surface model simulations capture soil profile water movement through the use of soil hydraulics sub-models, but good hydraulic parameterisations are often lacking, especially in the tropics. We present much-improved gridded datasets of hydraulic parameters for surface soil for the critical area of tropical South America, describing soi...

A continuing challenge in tropical ecology is to explain the coexistence of large numbers of rain forest tree species. One possible coexistence mechanism is partitioning of the highly variable and dynamic forest light environment, in which species that grow better in one light treatment grow worse in another. To test whether species respond differe...

A continuing challenge in tropical ecology is to explain the coexistence of large numbers of rain forest tree species. One possible coexis-tence mechanism is partitioning of the highly variable and dynamic forest light environment, in which species that grow better in one light treatment grow worse in another. To test whether species respond differ...

A better understanding of the mechanisms controlling the magnitude and sign of carbon components in tropical forest ecosystems is important for reliable estimation of this important regional component of the global carbon cycle. We used the JULES vegetation model to simulate all components of the carbon balance at six sites along an Andes-Amazon tr...

Accurate monitoring of the effectiveness of protected areas (PAs) in decreasing deforestation is increasingly important given the vital role of forest protection in climate change mitigation. Recent studies on PA effectiveness have used remote-sensing imagery to compare deforestation rates within PAs to surrounding areas. However, remote-sensing da...

Small-seeded plant species are often reported to have high relative growth rate or RGR. However, because RGR declines as plants grow larger, small-seeded species could achieve higher RGR simply by virtue of their small size. In contrast, size-standardized growth rate or SGR factors out these size effects. Differences in SGR can thus only be due to...

1. Plant growth is a fundamental ecological process, integrating across scales from physiology to com- munity dynamics and ecosystem properties. Recent improvements in plant growth modeling have al- lowed deeper understanding and more accurate predictions for a wide range of ecological issues, includ- ing competition among plants, plant-herbivore i...

Field measurements of radiation fluxes—notably downwelling longwave radiation flux (LW flux)—are as yet rare or nonexistent outside a very select number of sites in the tropics. Data gaps can only be filled through the use of estimation schemes based on measurements of other meteorological variables, and there is a need for recommendations on best...

Tropical forests are a critical component of the global carbon cycle and their response to environmental change will play a key role in determining future concentrations of atmospheric carbon dioxide (CO2). Increasing primary productivity in tropical forests over recent decades has been attributed to CO2 fertilization, and greater biomass in tropic...

Plant growth is an essential ecological process, integrating across scales from physiology to community dynamics. Predicting the growth of plants is essential to understand a wide range of ecological issues, including competition, plant-herbivore interactions and ecosystem functioning. A challenge in modeling plant growth is that growth rates almos...

Background/Question/Methods Plant growth is an essential ecological process, integrating across scales from physiology to community dynamics. Many models have been proposed but most suffer from the almost inescapable tradeoffs among a model’s flexibility, its predictive capacity, and the data requirements for its parameterization. A further challe...

Spatial and temporal variation in the below-canopy light environment of tropical forests is not well known and its measurement is technically challenging. Distributions of gap and understory areas in forests are likewise little known because of the resource requirements of forest structural censuses and a lack of consensus over how gaps should be d...

Secondary dispersal is an important stage in the life cycle of tree species, determining the fate of a high proportion of all seeds. For small-seeded species both physical and biological processes may influence the secondary fate of seeds, however the relative importance of these processes is not well known. Seeds of the pioneer tree species Cecrop...

Soil water and temperature regimes in the tropical moist forest on Barro Colorado Island, Panama, were simulated directly from meteorological data using the model SWEAT. Separate field observations from root-exclusion, litter-removal and control treatments in one small and one large forest gap were used for calibration and validation. After irrigat...

The managers at Doñana are trying to decide whether to devote their limited resources to reducing hunting in the park or bringing pressure to bear on upstream mining to reduce lead pollution. A sensitivity analysis of a model of blood lead levels will help them to identify the most cost-effective decision. A basic model of blood lead levels in Span...

It has been suggested that discrimination and rejection of the nestlings of avian brood parasites are most likely to evolve when the parasite nestling is raised alongside the host nestlings, for example, many cowbird-host systems. Under these circumstances, the benefits of discrimination are high because the host parents may save most of their broo...