QUANTITATIVE ASPECTS OF PLANT DISTRIBUTION

Ecosystem Services Flows: Why Stakeholders' Power Relationships Matter

The ecosystem services framework has enabled the broader public to acknowledge the benefits nature provides to different stakeholders. However, not all stakeholders benefit equally from these services. Rather, power relationships are a key factor influencing the access of individuals or groups to ecosystem services. In this paper, we propose an adaptation of the “cascade” framework for ecosystem services to integrate the analysis of ecological interactions among ecosystem services and stakeholders’ interactions, reflecting power relationships that mediate ecosystem services flows. We illustrate its application using the floodplain of the River Piedra (Spain) as a case study. First, we used structural equation modelling (SEM) to model the dependence relationships among ecosystem services. Second, we performed semi-structured interviews to identify formal power relationships among stakeholders. Third, we depicted ecosystem services according to stakeholders’ ability to use, manage or impair ecosystem services in order to expose how power relationships mediate access to ecosystem services. Our results revealed that the strongest power was held by those stakeholders who managed (although did not use) those keystone ecosystem properties and services that determine the provision of other services (i.e., intermediate regulating and final services). In contrast, non-empowered stakeholders were only able to access the remaining non-excludable and non-rival ecosystem services (i.e., some of the cultural services, freshwater supply, water quality, and biological control). In addition, land stewardship, access rights, and governance appeared as critical factors determining the status of ecosystem services. Finally, we stress the need to analyse the role of stakeholders and their relationships to foster equal access to ecosystem services.

How long is enough to detect terrestrial animals? Estimating the minimum trapping effort on camera traps

Camera traps is an important wildlife inventory tool for estimating species diversity at a site. Knowing what minimum trapping effort is needed to detect target species is also important to designing efficient studies, considering both the number of camera locations, and survey length. Here, we take advantage of a two-year camera trapping dataset from a small (24-ha) study plot in Gutianshan National Nature Reserve, eastern China to estimate the minimum trapping effort actually needed to sample the wildlife community. We also evaluated the relative value of adding new camera sites or running cameras for a longer period at one site. The full dataset includes 1727 independent photographs captured during 13,824 camera days, documenting 10 resident terrestrial species of birds and mammals. Our rarefaction analysis shows that a minimum of 931 camera days would be needed to detect the resident species sufficiently in the plot, and c. 8700 camera days to detect all 10 resident species. In terms of detecting a diversity of species, the optimal sampling period for one camera site was c. 40, or long enough to record about 20 independent photographs. Our analysis of evaluating the increasing number of additional camera sites shows that rotating cameras to new sites would be more efficient for measuring species richness than leaving cameras at fewer sites for a longer period.

Centaurea in South-West Asia: patterns of distribution and diversity

In SW Asia 260 species of Centaurea in 38 sections are recognised. Species numbers are highest in S and E Turkey and adjacent Iran and Iraq. East Iran and Afghanistan are poor in species. The number of sections is largest in NE Turkey (and adjacent Transcaucasia). Two hundred and one species are restricted to the area under study; the greatest number of narrow endemics is found in S and E Turkey. The subgenera and sections show quite different patterns of distribution and centres of diversity. The data presented point to E Anatolia and adjacent areas as the foremost centre of evolution for the genus and make probable a relatively recent speciation; an important secondary centre is S Turkey (and of course several other Mediterranean countries too). Some notes are added on the morphological variation in the genus and possible factors influencing its evolution.

Dominance and Diversity in Land Plant Communities: Numerical relations of species express the importance of competition in community function and evolution

Most plant communities consist of several or many species which compete for light, water, and nutrients. Species in a given community may be ranked by their relative success in competition; productivity seems to be the best measure of their success or importance in the community. Curves of decreasing productivity connect the few most important species (the dominants) with a larger number of species of intermediate importance (whose number primarily determines the community's diversity or richness in species) and a smaller number of rare species. These curves are of varied forms and are believed to express different patterns of competition and niche differentiation in communities. It is probably true of plants, as of animals, that no two species in a stable community occupy the same niche. Evolution of niche differentiation makes possible the occurrence together of many plant species which are partial, rather than direct, competitors. Species tend to evolve also toward habitat differentiation, toward scattering of their centers of maximum population density in relation to environmental gradients, so that few species are competing with one another in their population centers. Evolution of both niche and habitat differentiation permits many species to exist together in communities as partial competitors, with distributions broadly and continuously overlapping, forming the landscape's many intergrading communities.

Scale dependence in plant biodiversity

The relationship between the number of species and the area sampled is one of the oldest and best-documented patterns in community ecology. Several theoretical models and field data from a wide range of plant and animal taxa suggest that the slope, z, of a graph of the logarithm of species richness against the logarithm of area is roughly constant, with z approximately 0.25. We collected replicated and randomized plant data at 11 spatial scales from 0.01 to 10(8) square meters in Great Britain which show that the slope of the log-log plot is not constant, but varies systematically with spatial scale, and from habitat to habitat at the same spatial scale. Values of z were low (0.1 to 0.2) at small scales (<100 square meters), high (0.4 to 0.5) at intermediate scales (1 hectare to 10 square kilometers), and low again (0.1 to 0.2) for the largest scale transitions (e.g., East Berks to all of Berkshire). Instead of one process determining changes in species richness across a wide range of scales, different processes might determine plant biodiversity at different spatial scales.

Distribution of capillaries and diffusion distances in guinea pig myocardium

A frequency distribution of distances from random points to the nearest capillary was generated from high-magnification photomicrographs of thin sections of the myocardium of seven guinea pigs. Individual mean capillary densities taken from regions viewed in transverse section ranged from approximately 1800 to 2500 capillaries/mm2. Mean (R) and maximal (R95) diffusion distances measured by the closest individual method ranged from R = 6.6 to 8.7 microns and R95 = 11 to 18 microns. Further mathematical analysis of the frequency distributions of diffusion distances indicated that the capillaries of the myocardium are distributed in an ordered array.

The distribution of diffusion distances in the gastrocnemius muscle of various mammals during maturation

Large changes in fiber size, capillary density and capillary/fiber architecture occur during maturation of mammalian skeletal muscle. To examine the effect of these changes on oxygen diffusion distance, the mean (R) and maximal (R95) distances from the capillary to the tissue were measured in the gastrocnemius of maturing guinea pigs, rats and dogs. Hyperbolic relationships between capillary density and R and between capillary density and R95 were found for the combined data from these three species. The R and R95 increased with decreasing CD in growing guinea pigs and rats, but they remained constant in dogs. Statistical analyses showed that the capillaries in this muscle in all three species tended to be distributed in ordered arrays. These anatomical measurements are discussed in relation to their potential physiological impact on oxygen delivery to tissues.

Some morphometric methods for the central nervous system

It is the quantitative study of the central nervous system to enumerate neurone populations. Since neurones are generally arranged in non-random patterns the conventional method of counting with a square lattice graticule in the ocular of the microscope is severely restricted. Appropriately tailored methods of (a) counting, or (b) estimating the density of a neurone population must therefore be used. Four types of neuronal distribution pattern are discussed and morphometric methods adapted to them are presented, as follows: (1) Where the whole population is circumscribed, as in the anterior horn motor neurones of the cord, direct counting is feasible. Only those cells whose nucleoli are visible should be included; this diminishes the bias in favour of large cells, and if one corrects for the fact that larger neurones have larger nucleoli the bias can be eliminated completely. (2) Where neurones are situated on an "interface", as Purkinje cells are, the length of its profile (in this instance the boundary between the molecular and granular zones) is estimated by superimposing parallel lines on the microscopical image and counting intersections as these lines cross the interface. The number of Purkinje cells in each particular field is counted at the same time. A "linear dinsity" (PL) is then calculated from the formula pl = 2n/pid where n is the quotient of (a) the number of cells counted along (b) an estimated length of profile, and d is the distance between the parallel lines of the graticule. For comparative studies between cerebella of different sizes a correction factor is easily introduced. Those who prefer to work on photomicrographs can use a mapping wheel to measure a length of profile and then proceed as before. (3) Where neurones are organised in a curving band, as in the dentate nucleus, another form of cell density can be established. The microscope is focused on a neurone at random, and the distance from this cell to its nearest neighbour is measured, preferably by means of a screw-micrometer eyepiece. The mean value r of a number of such measurements is substituted in a formula which gives the "areal density" of the neurone population: pa = 1/4r2. This method can be applied to photomicrographs by using a pair of dividers and/or an accurate rule to measure the set of r values. (4) In large collections of neurones, e.g., in the thalamus, three methods are available: (a) the nearest neighbour method; (b) a conventional squared graticule count, and (c) a count of cells intersected by a line probe as in Haug's (1972) technique (fig. 5), or a modified form of Strong's (1966) transect method.