Statistics for Spatial Data.

Individual-based modeling is a new, exciting discipline that allows ecologists to explore, using computer simulations, how properties of populations and ecosystems might evolve from the characteristics and behaviors of individual organisms. Individual-based Modeling and Ecology, written by Volker Grimm and Steven F. Railsback, gives an excellent introduction and overview of this field. It should be read by everyone interested in individual-based modeling, and especially by anyone contemplating developing, or being involved with a group developing, an individualbased model.

http://www.gbv.de/dms/weimar/toc/396272002_toc.pdf

Individual-based modeling and ecology

Summary 1. Increasingly, river managers are turning from hard engineering solutions to ecologically based restoration activities in order to improve degraded waterways. River restoration projects aim to maintain or increase ecosystem goods and services while protecting downstream and coastal ecosystems. There is growing interest in applying river restoration techniques to solve environmental problems, yet little agreement exists on what constitutes a successful river restoration effort. 2. We propose five criteria for measuring success, with emphasis on an ecological perspective. First, the design of an ecological river restoration project should be based on a specified guiding image of a more dynamic, healthy river that could exist at the site. Secondly, the river’s ecological condition must be measurably improved. Thirdly, the river system must be more self-sustaining and resilient to external perturbations so that only minimal follow-up maintenance is needed. Fourthly, during the construction phase, no lasting harm should be inflicted on the ecosystem. Fifthly, both pre- and postassessment must be completed and data made publicly available. 3. Determining if these five criteria have been met for a particular project requires development of an assessment protocol. We suggest standards of evaluation for each of the five criteria and provide examples of suitable indicators. 4. Synthesis and applications . Billions of dollars are currently spent restoring streams and rivers, yet to date there are no agreed upon standards for what constitutes ecologically beneficial stream and river restoration. We propose five criteria that must be met for a river restoration project to be considered ecologically successful. It is critical that the broad restoration community, including funding agencies, practitioners and citizen restoration groups, adopt criteria for defining and assessing ecological success in restoration. Standards are needed because progress in the science and practice of river restoration has been hampered by the lack of agreed upon criteria for judging ecological success. Without well-accepted criteria that are ultimately supported by funding and implementing agencies, there is little incentive for practitioners to assess and report restoration outcomes. Improving methods and weighing the ecological benefits of various restoration approaches require organized national-level reporting systems.

/pdf/standards-for-ecologically-successful-river-restoration-m6t9p6x5um.pdf

Standards for ecologically successful river restoration

What determines the number and size of the seeds produced by a plant? How often should it reproduce them? How often should a plant produce them? Why and how are seeds dispersed, and what are the implications for the diversity and composition of vegetation? These are just some of the questions tackled in this wide-ranging review of the role of seeds in the ecology of plants. The authors bring together information on the ecological aspects of seed biology, starting with a consideration of reproductive strategies in seed plants and progressing through the life cycle, covering seed maturation, dispersal, storage in the soil, dormancy, germination, seedling establishment, and regeneration in the field. The text encompasses a wide range of concepts of general relevance to plant ecology, reflecting the central role that the study of seed ecology has played in elucidating many fundamental aspects of plant community function.

The ecology of seeds

Recently there has been much interest in the hypothesis that competition between individual plants is asymmetric or onesided: larger individuals obtain a disproportionate share of the resources (for their relative size) and suppress the growth of smaller individuals. This has important implications for population structure, for the analysis of competition between plants at the individual, population and community levels, and for our understanding of competition as a selective force in the evolution of plant populations.

Asymmetric competition in plant populations

Latitude is an important determinant of local environmental conditions that affect plant growth. Forty ecotypes of Arabidopsis thaliana were selected from a wide range of latitudes (from 16°N to 63°N) to investigate genetic variation in plant size and relative growth rate (RGR) along a latitudinal gradient. Plants were grown in a greenhouse for 31 days, during which period three consecutive harvests were performed. Plants from high latitudes tended to have smaller plant size in terms of seed size, cotyledon width, rosette size, number of rosette leaves, size (leaf area) of the largest leaves, total leaf area, and total dry weight per plant than those from low latitudes. The mean (±SE) RGR across ecotypes was 0.229 (±0.0013) day−1. There was, however, significant ecotypic variation, with RGR being negatively correlated with latitude. The two main components of RGR, leaf area ratio (LAR) and unit leaf rate (ULR), were also correlated with latitude: LAR increased with increasing latitude while ULR decreased with increasing latitude. It was also found that RGR tended to be negatively correlated with LAR, specific leaf area (SLA) and specific root length (SRL) but to be positively correlated with mean area per leaf (MAL) and ULR. The variation in RGR among ecotypes was relatively small compared with that in the other traits. RGR may be a conservative trait, whose variation is constrained by the trade-off between its physiological (i.e. ULR) and morphological (i.e. LAR) components.

Latitudinal variation in plant size and relative growth rate in Arabidopsis thaliana

A stochastic model and the moment dynamics of the growth and size distribution in plant populations

The size structure of populations is important for the study of the life histories and evolution of plant species. Many aspects of the dynamics of size structure as affected by species characteristics and environmental conditions have been interpreted well by recent models.

Dynamics of size structure in plant populations

With the increase in concentration of applied salicylic acid (SA), chlorophyll (Chl) content decreased significantly in both wheat and moong seedlings. Chl a/b ratio decreased significantly only in wheat and remained constant in moong. On the other hand, total carotenoid (Car) content, size of xanthophyll pool, and de-epoxidation rate increased significantly with an increase in SA concentration in both plant species. Hence SA treatment may induce Car biosynthesis in these plant species, but the increase in the xanthophyll pool and de-epoxidation rate indicates that SA may create oxidative stress the degree of which is different in various plants.

Effect of salicylic acid on chlorophyll and carotenoid contents of wheat and moong seedlings

Growth dynamics and size structure during one growing season were investigated at the level of the individual shoot of Phragmites australis, a clonal plant. These were based on the diffusion model for three shoot populations which are described as even-aged sparse (the least crowded), even-aged dense and uneven-aged dense (the most crowded). Irrespective of the difference in the degree of crowdedness, these three shoot populations converged to the same size structure in height and weight as they grew, suggesting a regulatory mechanism between shoots. There was no growth in shoot diameter, and hence size-structure dynamics of shoot height and weight were almost parallel (...)

Toshihiko Hara

Papers

Latitudinal variation in plant size and relative growth rate in Arabidopsis thaliana

A stochastic model and the moment dynamics of the growth and size distribution in plant populations

Dynamics of size structure in plant populations

Effect of salicylic acid on chlorophyll and carotenoid contents of wheat and moong seedlings

Growth dynamics and size structure of shoots of Phragmites australis, a clonal plant