Aspects Of Landscape Structure Research Articles

Plant–pollinator metanetworks in fragmented landscapes: a simulation study

BackgroundThe topology of the plant–pollinator network can be explained by the species’ abundance and their random interactions. Plant–pollinator networks can be studied in the context of a landscape, because each patch can accommodate a certain local network. Local populations of pollinators in the landscape can be connected through migration and then constitute a metanetwork that is known as a combination of spatial and ecological networks. In this regard, habitat fragmentation can affect the topology of plant–pollinator metanetworks through changes in the species abundance and limiting their interactions. However, it is not clear what pattern (fragmented or aggregated) of the landscape structure can accommodate networks with a higher degree of specialization.Methodswe created simulated landscapes with different forest proportions scenarios (from 5% to 50% of the total landscape) and degrees of fragmentation. Then, for each landscape, we limited the proportion of pollinators to the forest patch. We assumed that plants and pollinators are randomly distributed around the landscape and interact randomly. We used landscape metrics to measure different aspects of landscape structure and bipartite metrics for calculating the degree of specialization in plant–pollinator networks.ResultsThe statistical relationship between bipartite and landscape metrics showed that the relationship between the topology of plant–pollinator networks and the landscape structure is affected by the forest amount in the landscape and the degree of forest fragmentation. We also found that according to the nestedness and H2 (a measure of specialization) metrics, fragmented landscapes contain more general plant–pollinator networks.ConclusionsOur findings suggest that fragmented landscapes, characterized by scattered forest patches, can promote higher levels of interaction between limited pollinators and diverse flowers, leading to more general plant–pollinator networks.

Ecological corridors in Costa Rica: An evaluation applying landscape structure, fragmentation‐connectivity process, and climate adaptation

AbstractIn recent years, ecological corridors have been proposed on a global scale as a response to the accelerated process of natural ecosystem fragmentation, mainly as a result of human impact. In accordance with this trend, Costa Rica has undergone a process of implementing ecological corridors as to promote ecological connectivity since the 1990s, with the establishment of 44 ecological corridors covering 38% of Costa Rica's territory. Nevertheless, there is no research evaluating these corridors on a national scale that takes into account their functions as conduits, barriers, and habitats. Thus, the objective of this research was to describe the process of biological corridor formation in Costa Rica, and to evaluate the potential effectiveness of corridors by considering aspects of landscape structure and ecological processes related to connectivity and fragmentation. We used the National Program of Ecological Corridors database along with coverage analysis from Landsat images from 2000 and 2015.The composition of the biological corridors was determined at the landscape scale and related to potential to maintain a specific population of wild mammals weighing more than 10 kg. The composition of the ecological corridors was highly variable in terms of total area, proportion of natural habitat, and fragmentation process. Most biological corridors are capable of maintaining viable populations of Pecari tajacu and Tapir bairdii, while none could maintain populations of Panthera onca and Tayassu pecari. Only 50% of the biological corridors had improved in their connectivity. Therefore, public policies, such as master plans focusing on ecosystem restoration must be established. In addition, only two biological corridors incorporate the majority of elevation ranges (Life Zones) present in the country, which reduces the potential of the corridor system as a tool for climate change adaptation.

Coccinellid response to landscape composition and configuration

Arthropod natural enemies provide valuable pest suppression in agricultural landscapes. Natural enemy abundance and diversity within a given crop, in turn, have frequently been shown to be positively related to the amount of semi-natural habitat in the landscape. However, other aspects of landscape structure may also influence natural enemy communities and may be more amenable to management. We simultaneously assessed the relationship among several metrics of landscape structure, as well as between these metrics and coccinellid activity in soybean fields. We used partial least squares regression to examine the coccinellid response to landscape structure. Coccinellid activity was lowest in landscapes dominated by annual crops grown in large fields and highest in landscapes dominated by semi-natural habitats such as grasslands and forests, with a higher diversity of crops grown in smaller fields. Landscape characteristics, including composition factors such as the type and amount of different land covers and configuration factors such as the interspersion of these land covers, are often correlated within a set of landscapes. Isolating the effects of individual landscape characteristics on natural enemy communities will be necessary to move forward with the development of management actions that can increase biocontrol services in agroecosystems.

Spatial hyperdynamism in a post-disturbance simulated forest

Competition–colonization models can address the population dynamics of remnants following habitat destruction. Spatially explicit versions have produced qualifications of the extinction debt issue and limited hyperdynamism in populations following habitat destruction. Although spatially explicit, these efforts examined few indicators of the spatial structure of the landscape. An existing model is modified here to represent a difference in niche adaptations as well as the competition–colonization tradeoff. Several landscape metrics are calculated at each iteration. Although the addition of niche differentiation did not change the qualitative outcome of the model, the spatial metrics show that some aspects of landscape structure, i.e., average patch area and proximity, become hyperdynamic and remain so. Small fluctuations in species populations are magnified in their spatial expression because the landscape is simplified.

How does landscape structure influence landscape connectivity?

We investigated the impact of landscape structure on landscape connectivity using a combination of simulation and empirical experiments. In a previous study we documented the movement behaviour of a specialized goldenrod beetle (Trirhabda borealis Blake) in three kinds of patches: habitat (goldenrod) patches and two types of matrix patch (cut vegetation and cut vegetation containing camouflage netting as an impediment to movement). In the current study, we used this information to construct simulation and experimental landscapes consisting of mosaics of these three patch types, to study the effect of landscape structure on landscape connectivity, using the T. borealis beetle as a model system. In the simulation studies, landscape connectivity was based on movements of individual beetles, and was measured in six different ways. The simulations revealed that the six measures of landscape connectivity were influenced by different aspects of landscape structure, suggesting that: (1) landscape connectivity is a poorly defined concept, and (2) the same landscape may have different landscape connectivity values when different measures of landscape connectivity are used. There were two general predictions that held over all measures of landscape connectivity: (1) increasing interpatch distance significantly decreased landscape connectivity and (2) the influence of matrix elements on landscape connectivity was small in comparison to the influence of habitat elements. Empirical mark‐release‐resight experiments using Trirhabda beetles in experimental landscapes supported the simulation results.

Количественная оценка отклонения ландшафтного разнообразия от потенциальной естественной растительности при помощи энтропии Шеннона

In the past 20 years, several metrics have been developed to quantify various aspects of landscape structure and diversity in space and time, and most have been tested on grid- based thematic maps. Once landscape patterns have been quantified, their effects on ecological functions can be explained if the expected pattern in the absence of specific processes is known. This type of expected pattern has been termed a neutral landscape model. In the landscape-ecological literature, researchers traditionally adopt random and fractal computer-generated neutral landscape models to verify the expected relationship between a given ecological process and landscape spatial heterogeneity. Conversely, little attention has been devoted to distribution patterns of potential natural vegetation (PNV) as an ecological baseline for the evaluation of pattern-process interactions at the landscape scale. As an application for demonstration, we propose a neutral model based on PNV as a possible reference for a quantitative comparison with actual vegetation (ARV) distribution. Within this context, we introduce an evenness-like index termed "actual-to-potential entropy ratio’ (HA/P=HARV/HPNV, where H is Shannon’s entropy). Results show that, despite the hypothetical character of most PNV maps, the use of PNV distribution as a baseline for a quantitative comparison with ARV distribution may represent a first step towards г general model for the evaluation of the effects of disturbance on vegetation patterns and diversity.

Integrating landscape-based values—Norwegian monitoring of agricultural landscapes

An accumulating body of research identifies the importance of landscape structure for a wide range of countryside interests. Landscape structure reflects the results of policies and practices, and is well-suited as a target for management actions. New landscape metrics represent a potential for indicator-based management, provided such metrics relate consistently to the landscape values of interest. In this paper we propose that aspects of landscape structure, specifically heterogeneity, may be related to landscape-based values such as biodiversity, cultural heritage and human appreciation. Birds and vascular plants correlated well with our index for the heterogeneity of land types, whereas insects did not. Occurrence of prehistoric graves was also associated with land type heterogeneity, though other types of cultural remains were not. Landscape experience seems to be associated with the heterogeneity of landscape space rather than heterogeneity of land types. Different aspects of heterogeneity, scale, and variation over time all contribute to explain how our measures of landscape-based values vary in their relationship to landscape heterogeneity. Successful integration between disciplines in landscape studies depends on having a common operational framework, a shared theoretical basis, and a harmonised approach to data collection.

Quantitative comparison of the diversity of landscapes with actual vs. potential natural vegetation

Abstract. In the past 20 years, several metrics have been developed to quantify various aspects of landscape structure and diversity in space and time, and most have been tested on grid‐based thematic maps. Once landscape patterns have been quantified, their effects on ecological functions can be explained if the expected pattern in the absence of specific processes is known. This type of expected pattern has been termed a neutral landscape model. In the landscape‐ecological literature, researchers traditionally adopt random and fractal computer‐generated neutral landscape models to verify the expected relationship between a given ecological process and landscape spatial heterogeneity. Conversely, little attention has been devoted to distribution patterns of potential natural vegetation (PNV) as an ecological baseline for the evaluation of pattern‐process interactions at the landscape scale. As an application for demonstration, we propose a neutral model based on PNV as a possible reference for a quantitative comparison with actual vegetation (AC V) distribution. Within this context, we introduce an evenness‐like index termed ‘actual‐to‐potential entropy ratio’ (HA/P = HACV/HPNV, where H is Shannon's entropy). Results show that, despite the hypothetical character of most PNV maps, the use of PNV distribution as a baseline for a quantitative comparison with ACV distribution may represent a first step towards a general model for the evaluation of the effects of disturbance on vegetation patterns and diversity.