Richard T. T. Forman

Patches and Structural Components for A Landscape Ecology

Landscapes as ecological units with structure and function are composed primarily of patches in a matrix. Patches differ fundamentally in origin and dynamics, while size, shape, and spatial configuration are also important. Line corridors, strip corridors, stream corridors, networks, and habitations are major integrative structural characteristics of landscapes. (Accepted for publication 29 May 1981)

Some general principles of landscape and regional ecology

A dozen general principles of landscape and regional ecology are delineated to stimulate their evaluation, refinement, and usage. Brief background material and a few references provide entrées into the subjects. The principles are presented in four groups: landscapes and regions; patches and corridors; mosaics; and applications. Most appear useful in solving a wide range of environmental and societal land-use issues.

Hedgerows and hedgerow networks in landscape ecology

Hedgerows originated and coexist with agriculture. Their internal structure and species diversity vary widely with origin (planted, spontaneous, or remnant), farming practices in adjacent fields, and the refined art of hedgerow management. Most hedgerow species are forest-edge species, and apparently none is limited to hedgerows. Wide hedgerows composed of trees and shrubs appear to function as corridors for movement of many plants and animals across a landscape. The reduction of crop loss, by dampening pest population fluctuations with hedgerow predators, remains a hypothesis for study.Field microclimate downwind of a hedgerow is modified about 16 times the hedgerow height (h) for evaporation, and approximately 28 h for wind speed. A turbulent wind pattern with harsher microclimate is present at 6–8 h if a second hedgerow is nearby downwind. Zones of higher crop productivity at 3- to 6-h downwind, and 2- to 6-h upwind of a second hedgerow may be expected. Overall, we expect little short-term difference in farm-field production with or without hedgerows.Evidence suggests that hedgerow networks, and especially their mesh size (of fields), exert a major control on many major landscape fluxes. Such fluxes include animal populations, wind speed, evapotranspiration and soil desiccation, soil erosion and nutrient runoff, species movement along network lines, and movement of field species across the network. In a relatively short period, the hedgerow ecosystem, with no unique species, has attained a metastable equilibrium, which is regulated by enormous human inputs.More than 20 economic roles of hedgerows are pinpointed. The roles, providing resources and protection of resources, are poorly known quantitatively. We conclude that hedgerows perform diverse functions for society and the farmer that are both economically and ecologically significant.

Forest size and avian diversity in New Jersey woodlots with some land use implications

SummaryThe effect of forest size on avian diversity was studied in oak forest patches in rural New Jersey. Number of bird species continued to increase significantly in old oak woods up through 40 ha. This was due to the progressive addition of carnivorous species with increasing minimum forest size requirements. One large woodlot had more species than the same area subdivided into smaller woodlots. To maintain maximum regional diversity more than three large forests are required. Primary land use priority should be to protect large forests. Second priority should be to maintain a high density of small woodlots.

Pine barrens: ecosystem and landscape.

This illustrated survey brings together the work of forty-one experts who describe the people, geology and soils, climate, water and aquatic ecosystems, vegetation patterns, plant and animals, and animal communities of the remarkable 2,000 square mile forested landscape in New Jersey known as the Pine Barrens.

Landscape graphs: Ecological modeling with graph theory to detect configurations common to diverse landscapes

In view of the bewildering diversity of landscapes and possible patterns therein, our objectives were to see if a useful modeling method for directly comparing land mosaics could be developed based on graph theory, and whether basic spatial patterns could be identified that are common to diverse landscapes. The models developed were based on the spatial configuration of and interactions between landscape elements (ecosystems, land uses or ecotopes). Nodes represented landscape elements and linkages represented common boundaries between elements. Corridors, corridor intersections, and the matrix were successfully incorporated in the models. Twenty-five landscape graphs were constructed from aerial photographs chosen solely to represent a breadth of climates, land uses and human population densities. Seven distinctive clusters of nodes and linkages were identified and common, three of which, in the forms of a ‘spider’, ‘necklace’ and ‘graph cell,’ were in >90% of the graphs. These represented respectively the following ‘configurations’ of patches, corridors and matrix: (1) a matrix area surrounding or adjoining many patches; (2) a corridor bisecting a heterogeneous area; and (3) a unit in a network of intersecting corridors. The models also indicated that the connectivity or number of linkages for several common elements, such as fields and house clearings, was relatively constant across diverse landscapes, and that linear shaped elements such as roads and rivers were the most connected. Several additional uses of this graph modeling, including compatibility with systems dynamics models, are pinpointed. Thus the method is useful in allowing simple direct comparisons of any scale and any landscape to help identify patterns and principles. A focus on the common and uncommon configurations should enhance our understanding of fluxes across landscapes, and consequently the quality of land planning and management.

Herb Cover Effects on Tree Seedling Patterns in a Mature Hemlock‐Hardwood Forest

The role of herbs in affecting tree seedling patterns was investigated in an old—growth hemlock—hardwood forest in Cathedral State Park, West Virginia. Herb species cover, tree seedling density, and overhead foliage were sampled along with midsummer soil pH, soil moisture, and light intensity in 20 selected herb patches and 440 30 x 30 cm plots. Analyses of the patch data showed significant correlations of seedlings of major tree species: Prunus serotina, Acer rubrum, Tsuga canadensis, and Betula spp., with leading herb species (Dennstaedtia, Mitchella, Lycopodium, and Oxalis). Each tree species had few seedlings in some herb species patches, but was independent of or concentrated in other patches. Herb species were spatially related to other herb species, but showed little correspondence to soil pH, soil moisture, and light intensity patterns. Analyses of plot samples supported each of the above results. In addition, total tree seedling density was inversely correlated with total herb cover, but neither ...

A conceptual model of land conversion processes: predictions and evidence from a microlandscape experiment with grassland insects

Land conversion due to human activities produces distinctive spatial patterns across the landscape. It remains unclear, however, how particular spatial arrangements of remnant habitat patches influence species persistence. We present a conceptual model of landscape change that focuses explicitly on habitat spatial arrangement. Four sequences, characterized as shrinkage, bisection, fragmentation, and perforation, differ qualitatively in the spatial arrangement of intact habitat and differ quantitatively in boundary length, amount of interior area, and connectivity. We tested the predictions of this conversion sequence model in a microlandscape field experiment with insects in a native grassland habitat. The four conversion sequences significantly influenced the species composition of the above-ground insect community, and insect species groups varied in their responses. Four patterns were evident from the field experiment: (1) as habitat decreased, insect density rose sharply on small dispersed patches of the bisection and fragmentation sequences, an effect less evident in the large remnant patch of the shrinkage sequence; (2) species richness declined only in the case of shrinkage, whereas richness increased in the fragmentation sequence; (3) most individual species examined responded similarly to the community as a whole: and (4) large rare species were concentrated in remaining habitat of the shrinkage and fragmentation sequences. Overall, the shrinkage and perforation sequences, which had high connectivity, were similar to one another in species composition, while the bisection and fragmentation sequences, which had low connectivity, were similar to one another. Based on these results, we conclude that a spatial pattern of land conversion that maintains one or more large, closely spaced remnant patches of native vegetation is essential for species persistence.

Nature conserved in changing landscapes with and without spatial planning

Abstract We use a simple spatial model to illustrate an ecologically optimum sequence of landscape change, evaluate how much ecological difference it makes, and determine if there is a phase during which its use is most effective or important in protecting nature. Compared with a random pattern of vegetation removal, the spatial solution protects five times more area of high ecological value. Equally significant is the better spatial arrangement of vegetation. Using random change as an analogue for lack of planning, we compare different lengths of random change before spatial planning begins. The analysis suggests that spatial planning is most significant in nature conservation when 10–40% of the natural vegetation has been removed from a landscape. We conclude that the few simple patterns and principles presented, combined with a general survey of a landscape area, constitute an important solution to land planning and conservation, especially where detailed ecological data are limited or lacking.

Plant Species Removals and Old‐Field Community Structure and Stability

The roles of species abundance, community structure, and competitive relation- ships in community recovery following stress were studied by separately removing species in June in three 6-yr-old fields at Hutcheson Memorial Forest, New Jersey. Percent cover of remaining species was measured in September. In 9 of 17 species removals there was high community recovery, mainly due to one re- maining species which increased significantly; 8 removals resulted in low community recovery. Abundant species replaced species removed. Only one remaining species, Potentilla simplex, increased regardless of treatment; the responses of others were highly dependent on the particular species removed, emphasizing the importance of species interactions. Reciprocal removals for a species pair produced unrelated responses. Community recovery correlated inversely with cover of species removed. However, the order of species according to cover differed from the order of amounts of community recovery, indicating that species rank by abundance may be an inadequate measure of relative importance of a species in the community. High community recovery correlated with vertical stratification (bilayered with a dense ground layer), horizontal patchiness (many low diversity patches), abundance of rapid vegetatively reproducing species, and differential species interactions. Species diversity changed negligibly following removal of a species. It is concluded that community recovery from a stress and the effects of species extinction are dependent on (a) community structure and (b) species composition.