Dry-matter production in a tomato crop: comparison of two simulation models

TOMSIM(l.O) and TOMGRO(l.O) are two dynamic models for tomato growth and development. Their submodels for dry matter production are compared and discussed. In TOMSIM(l.O), dry matter production is simulated by a modified version of SUCROS87 (Spitters et al., 1989). Single leaf photosynthesis rates are calculated separately for shaded and sunlit leaf area at different depths in the canopy, according to the direct and diffuse components of light; daily crop gross assimilation rate (A) is computed by integration of these rates over the different depths and over the day. In TOMSIM(l.O) leaf photochemical efficiency (e) and potential leaf gross photosynthesis rate at saturating light level (Pgmax) both depend on temperature and C02 level. In TOMGRO(l.O) crop gross photosynthesis rate is calculated by the equation of Acock et al. (1978); e is a constant and Pg max is a linear function of C02. In both models leaf photosynthesis characteristics are assumed to be identical in the whole canopy. Maintenance respiration (Rm) and conversion efficiency (Cf) are taken into account in the same way, except that root maintenance respiration is neglected in TOMGRO(l.O). For both models a sensitivity analysis was performed on the input variables (light intensity, temperature, C02 and leaf area index (LAI)) and on some of the model parameters. Under most conditions considered, simulated A was found to be 5-30% higher in TOMSIM(l.O) than in TOMGRO(l.O). At temperatures above 18°C Rm was also higher in TOMSIM(l.O), and C, was 4% higher in TOMGRO(l.O). The two models were very sensitive to changes in e and to a lesser extent to changes in the light extinction coefficient, whereas the scattering coefficient of leaves had hardly any effect on the simulated A. TOMGRO(l.O) appeared to be rather sensitive to the C02 use efficiency, whereas at ambient C02 level mesophyll resistance was quite important in TOMSIM(l.O). Four sets of experimental data (differences in cultivar, C02 enrichment and planting date) from Wageningen (The Netherlands) and Montfavet (southern France) were used to validate the models. Average 24 h temperature and average daily C02 concentration values were used as input to the models. For the Wageningen experiments, hourly PAR values were calculated from the daily global radiation sum by TOMSIM(l.O) and used as input in both models. For the Montfavet experiment, average hourly PAR measurements were used. Also measured LAI, dry matter distribution and organ dry weights (for calculation of Rm) were input to the simulation. In the Wageningen experiments, total dry matter production was simulated reasonably well by both models, whereas in the Montfavet experiment an under-estimation of about 35% occurred. TOMGRO(l.O) and TOMSIM(l.O) simulated almost identical curves in all four experiments. Strong and weak points of both models are discussed.     

The resilience of a floodplain vegetation landscape

Landscape Ecology - Floodplains are complex adaptive ecosystems that provide an array of ecosystem services. Despite the growing focus on resilience as a fundamental feature of floodplain...     

Inherent limitations of nondestructive chlorophyll meters: a comparison of two types of meters

Two types of nondestructive chlorophyll meters were compared with a standard, destructive chlorophyll measurement technique. The nondestructive chlorophyll meters were 1) a custom built, single-wavelength meter, and 2) the recently introduced, dual-wavelengh, chlorophyll meter from Minolta (model SPAD-502). Data from both meters were closely correlated with destructive measurements of chlorophyll (r2 = 0.90 and 0.93; respectively) for leaves with chlorophyll concentrations ranging from 100 to 600 mg m-2, but both meters consistently overestimated chlorophyll outside this range. Although the dual-wavelength meter was slightly more accurate than the single-wavelength meter (higher r2), the light-scattering properties of leaf cells and the nonhomogeneous distribution of chlorophyll in leaves appear to limit the ability of all meters to estimate in vivo chlorophyll concentration.     

A comparison of popular approaches to optimize landscape resistance surfaces

Landscape Ecology - Landscape resistance surfaces are often used to address questions related to movement, dispersal, or population connectivity. However, modeling landscape resistance is...     

Trajectories of land use change in Europe: a model-based exploration of rural futures

Land use change is characterized by a high diversity of change trajectories depending on the local conditions, regional context and external influences. Policy intervention aims to counteract the negative consequences of these changes and provide incentives for positive developments. Region typologies are a common tool to cluster regions with similar characteristics and possibly similar policy needs. This paper provides a typology of land use change in Europe at a high spatial resolution based on a series of different scenarios of land use change for the period 2000–2030. A series of simulation models ranging from the global to the landscape level are used to translate scenario conditions in terms of demographic, economic and policy change into changes in European land use pattern. A typology developed based on these simulation results identifies the main trajectories of change across Europe: agricultural abandonment, agricultural expansion and urbanization. The results are combined with common typologies of landscape and rurality. The findings indicate that the typologies based on current landscape and ruralities are poor indicators of the land use dynamics simulated for the regions. It is advocated that typologies based on (simulated) future dynamics of land change are more appropriate to identify regions with potentially similar policy needs.     

The effects of habitat resolution on models of avian diversity and distributions: a comparison of two land-cover classifications

Quantifying patterns is a key element of landscape analysis. One aspect of this quantification of particular importance to landscape ecologists is the classification of continuous variables to produce categorical variables such as land-cover type or elevation stratum. Although landscape ecologists are fully aware of the importance of spatial resolution in ecological investigations, the potential importance of the resolution of classifications has received little attention. Here we demonstrate the effects of using two different land-cover classifications to predict avian species richness and the occurrences of six individual species across the conterminous United States. We compared models built with a data set based on 14 coarsely resolved land-cover variables to models built with a data set based on 160 finely resolved land-cover variables. In general, comparable models built with the two data sets fit the data to similar degrees, but often produced strikingly different predictions in various parts of the country. By comparing the predictions made by pairs of models, we determined in which regions of the US predictions were most sensitive to differences in land-cover classification. In general, these sensitive areas were different for four of the individual species and for predictions of species richness, indicating that alternate classifications will have different effects in the analyses of different ecological phenomena and that these effects will likely vary geographically. Our results lead us to emphasize the importance of the resolution to which continuous variables are classified in the design of ecological studies.This revised version was published online in May 2005 with corrections to the Cover Date.     

Multifunctionality of floodplain landscapes: relating management options to ecosystem services

The concept of green infrastructure has been recently taken up by the European Commission for ensuring the provision of ecosystem services (ESS). It aims at the supply of multiple ESS in a given landscape, however, the effects of a full suite of management options on multiple ESS and landscape multifunctionality have rarely been assessed. In this paper we use European floodplain landscapes as example to develop an expert based qualitative conceptual model for the assessment of impacts of landscape scale interventions on multifunctionality. European floodplain landscapes are particularly useful for such approach as they originally provided a high variety and quantity of ESS that has declined due to the strong human impact these landscapes have experienced. We provide an overview of the effects of floodplain management options on landscape multifunctionality by assessing the effects of 38 floodplain management interventions on 21 relevant ESS, as well as on overall ESS supply. We found that restoration and rehabilitation consistently increased the multifunctionality of the landscape by enhancing supply of provisioning, regulation/maintenance, and cultural services. In contrast, conventional technical regulation measures and interventions related to extraction, infrastructure and intensive land use cause decrease in multifunctionality and negative effects for the supply of all three aspects of ESS. The overview of the effects of interventions shall provide guidance for decision makers at multiple governance levels. The presented conceptual model could be effectively applied for other landscapes that have potential for a supply of a high diversity of ESS.     

Spatial and temporal organization of macroinvertebrate assemblages in a lowland floodplain ecosystem

An important goal in ecology is to understand controls on community structure in spatially and temporally heterogeneous landscapes, a challenge for which riverine floodplains provide ideal laboratories. We evaluated how spatial position, local habitat features, and seasonal flooding interact to shape aquatic invertebrate community composition in an unregulated riverine floodplain in western Alabama (USA). We quantified sediment invertebrate assemblages and habitat variables at 23 sites over a 15-month period. Dissolved oxygen (DO) varied seasonally and among habitats, with sites less connected to the river channel experiencing frequent hypoxia (<2 mg O₂ L^?1) at the sediment–water interface. Differences in water temperature among sites were lowest (<1 °C) during winter floodplain inundation, but increased to >14 °C during spring and summer as sites became isolated. Overall, local habitat conditions were more important in explaining patterns in assemblage structure than was spatial position in the floodplain (e.g., distance to the main river channel). DO was an important predictor of taxonomic richness among sites, which was highest where hydrologic connections to the main river channel were strongest. Compositional heterogeneity across the floodplain was lowest immediately following inundation and increased as individual sites became hydrologically isolated. Our results illustrate how geomorphic structure and seasonal flooding interact to shape floodplain aquatic assemblages. The flood pulse of lowland rivers influences biodiversity through effects of connectivity on hydrologic flushing in different floodplain habitats, which may prevent the development of harsh environmental conditions that exclude certain taxa. Such interactions highlight the ongoing consequences of river regulation for taxonomically diverse floodplain ecosystems.     

Vertical farming: a summary of approaches to growing skywards

Pressure on agricultural land from a rising global population is necessitating the maximisation of food production per unit area of cultivation. Attention is increasingly turning to Vertical Farming (VF) approaches in an attempt to provide a greater crop yield per square meter of land. However, this term has been used to cover a broad range of approaches, from personal- or community-scale vegetable and herb growing to vast skyscrapers for commercial production of a wide range of crops. This article summarises the main categories of VF in order to help clarify this emerging but sometimes confusing area of agriculture and discusses how scientific investigation of the potential of VF is currently lacking and will be required to help determine its feasibility as a method to assist meaningfully in global food production.     

Machine learning in landscape ecological analysis: a review of recent approaches

Landscape Ecology - Artificial Intelligence (AI) has rapidly developed over the past several decades. Several related AI approaches, such as Machine Learning (ML), have been applied to research on...     

Plant species response to urbanization: comparison of isolated woodland patches in two cities of North-Western France

The effect of urbanization on species distribution has been extensively documented, but a main challenge in urban ecology is to better understand the factors causing different distributions among species in response to urbanization. Hence, this paper aims to compare the effects of urbanization on woodland plant assemblages in two cities and to describe species responses by using several indicators. The study was carried out in the cities of Angers and Rennes (North-Western France) where 11 isolated woodlands were surveyed along an urban–rural gradient in each city. Abundance data of spontaneous species were collected from 220 quadrats. The effect of land cover (within a 500 m buffer around each woodland) on species assemblages was investigated by Canonical Correspondence Analysis. Buildings and pavement areas were the most significant predictors of species composition, and the effect of location in Angers or Rennes appeared on the second axis. More than 60% of the most frequent plant species were indicator of urban or rural location and their preferences were similar in the two cities. These lists of urban and rural indicator species were compared with Ellenberg’s indicator values and two other indicators specific to forest environment. The species which grow preferentially in urban woodlands are species which are already known to be associated with recent forests rather than ancient forests; with hedgerows rather than woodlands. The opposite pattern was observed concerning rural species. Moreover, urban indicator species have higher optima for soil pH and soil nitrogen content than rural indicator species. Different characteristics and history of forest habitat—continuity of the forest land cover, linearity of the habitat, change in adjacent land cover and land use—could select the same species, and the responses of the latter might involve different preferences concerning soil alkalinity and nutrient status.     

A comparison of neighbourhood liveability as perceived by two groups of residents: Tehran,Iran and Tartu,Estonia

Liveability is an important component of the sustainable urban environment, especially in residential neighbourhoods. This study presents a comparison in perceived liveability between residents living in two very different locations, Tehran, Iran and Tartu, Estonia, using a questionnaire survey (n = 102). The image-questionnaire was used to measure residents’ response towards environmental factors and to examine the relationships between the attributes of residential neighbourhoods and perceived liveability. Statistical analyses were performed to analyze the data collected from the survey. The results showed that the neighbourhood liveability was positively influenced by proportion and scale of the spaces, amount of private green areas, street character, amount of public greenery, the variety of building form, the mix of buildings from different periods, perceived crowding and social density. The study demonstrated that residents can assess the factors and that the approach worked in two contrasting locations. The results also showed a great deal of similarity in preference, although this was not the main aim of the study. The approach has potential to be incorporated into participatory urban planning models.     

Novel approaches to sampling pollinators in whole landscapes: a lesson for landscape-wide biodiversity monitoring

Landscape Ecology - Biodiversity monitoring programs require fast, reliable and cost-effective methods for biodiversity assessment in landscapes. Sampling pollinators across entire landscapes is...     

Dry-matter partitioning in a tomato crop: Comparison of two simulation models

SUMMARY

TOMSIM(l.O) and TOMGRO(I.O) are two dynamic models for tomato growth and development. Their sub-models for dry-matter distribution between leaves, stem and fruits were compared and discussed. In both models the simulated dry-matter distribution is regulated by the relative sink strengths of the plant organs. These sink strengths are quantified by the potential growth rates of individual organs, i.e. the growth rates under conditions of non-limiting assimilate supply. This approach is general and not limited to the tomato crop. In TOMGRO(J.O), fruits, leaves and internodes stay within age classes and move from class to class during development, whereas in TOMSIM (1.0), record is kept of every fruit truss separately but leaves and internodes are lumped together (i.e. no record of weight or leaf area per age class as in TOMGRO(l.O)). In TOMSIM(1.0), vegetative sink strength is a constant, whereas in TOMGRO(l.0) it is calculated from potential area expansion rate of leaves and specific leaf area. In both models, the ratio between leaf growth and stem growth is constant. In TOMGRO(l.O) there is a feed-back mechanism which controls the vegetative/generative balance: a higher demand/supply ratio for assimilates induces higher fruit abortion rates. In TOMSIM(l.O) the number of fruits set per truss is not simulated, but is an input to the model. TOM SIM (1.0) functions representing flowering rate, fruit growth period, vegetative sink strength and fruit sink strength were compared with similar TOMGRO(l.O) functions, in their dependence on temperature and physiological plant age. A sensitivity analysis was made for the effects of temperature, flowering rate, and fruit and vegetative sink strengths on dry-matter distribution for both models. A validation of both models was based upon periodic destructive harvests in: 1) a greenhouse experiment in Wageningen, using a round tomato cultivar, consisting of a control treatment and a treatment where every second truss was removed at anthesis, and 2) two greenhouse experiments conducted in Montfavet, using a beefsteak tomato cultivar. Daily shoot dry-weight increase, average 24 h greenhouse temperatures and numbers of fruits set per truss (in TOMGRO(l.O) numbers of flowers per truss) were inputs to the models. In general dry-matter distribution was simulated well by both models for the cultivar and conditions where they were developed. TOMGRO(1.0)'s poor performance in one of the validations resulted from the absence of an assimilate storage pool. To achieve reasonable agreement between measurements and simulations for situations other than where the models were developed, parameter adjustments had to be made, most likely reflecting cultivar differences. Strong and weak points of both models are discussed.     

Teaching landscape ecology: the importance of field-oriented,inquiry-based approaches

Context

Landscape ecology has traditionally been taught through theoretical classes or computer labs. On the other hand, field labs have been generally less used as a way of teaching landscape ecology concepts.

Objectives

We show that field labs with an inquiry-based approach, where students are involved in the investigation, are feasible for training students in landscape ecology. We evaluated how common field labs are in landscape ecology courses, and also their contribution for student learning.

Methods

We evaluated whether field labs are used in landscape ecology courses by scanning available syllabi. We also used outcomes from a course offered in Brazil to show how field labs can be integrated into landscape ecology courses.

Results

Only 18.2 % of the 44 syllabi we found had field labs. The case study developed in Brazil showed that field labs allowed students to develop important skills, including the ability to design field studies, choose appropriate scales of analysis, detect ecological patterns, and judge multiple hypotheses.

Conclusions

Field labs are still uncommon in landscape ecology courses, but they can be a useful tool to teach landscape ecology concepts and to help students developing the necessary skills to do research. We offer recommendations regarding how to incorporate field labs in landscape ecology courses.

     

Thinking outside the patch: a multi-species comparison of conceptual models from real-world landscapes

Context

When modeling a species’ distribution, landscapes can alternatively be conceptualized following patch- or gradient-based approaches. However, choosing the most suitable conceptualization is difficult and methods for empirical validation are still lacking.

Objectives

To address the conditions under which a given conceptual model is more suitable, taking into account landscape context and species trait dependency effects. Patch- and gradient-based conceptualizations were built based on two structurally different landscapes: variegated and mosaic. We hypothesize that: (H1) gradient-based models better describe variegated landscapes while patch-based models perform better in mosaic landscapes; and (H2) gradient-based models will fit generalist species better while patch-based models will suit specialists better.

Methods

We modeled the distribution of eleven bird species in each landscape using each conceptualization. We determined the suitability of each conceptual model to fit statistical models by looking for cross-species responses and deviations from best models.

Results

We found no clear support for our hypotheses. Although patch-based models performed better in mosaic landscapes (H1), they also provided useful conceptualizations in variegated landscapes. However, when patches showed high heterogeneity, gradient-based approaches better fit specialist species (H2).

Conclusions

The suitability of a given conceptual model depends on the interaction between species habitat specialization, and the intrinsic spatial heterogeneity of the landscape and the ability of each conceptualization to capture it. Gradient-based models provide better information on resource allocation, while patch-based models offer a simplified perspective on landscape attributes. Future research should consider the nature of both species and landscapes in order to avoid bias from inadequate landscape conceptualizations.