Drivers Of Spatial Patterns Research Articles

Multi‐scale drivers of spatial patterns in floodplain sediment and phosphorus deposition

AbstractThe capacity for floodplains to capture sediment and filter pollutants is spatially variable and depends on the complex interactions of geomorphic, geologic, and hydrologic variables that operate at multiple scales. In this study, we integrated watershed‐scale and local assessments to improve our understanding of floodplain depositional patterns. We developed a dataset of event‐scale observations of sediment and phosphorus deposition rates distributed at 129 plots across large environmental gradients of floodplain topography, valley geometry, and watershed characteristics in the Lake Champlain Basin, Vermont. Plot‐scale observations were used to evaluate the cross‐scale influence of environmental factors and were summarized into site‐scale averages to explore regional trends. Consistent with other studies, floodplain deposition generally scaled with drainage area, but trends were longitudinally discontinuous and depended on variations in valley width and slope. While variability in deposition patterns at the watershed‐scale was large (average of 2.0 (0.2–9.8) kg sediment m−2 yr−1; average of 1.4 (0.2–6.5) g phosphorus m−2 yr−1), the range in deposition rates locally across a floodplain was greater (average of 4.6 (0.06–21.7) kg sediment m−2 yr−1; average of 6.4 (0.1–41.1) g phosphorus m−2 yr−1). Local variables that described the proximity to water and sediment sources, and frequency with which the plot was activated by a flood, had the greatest relative contribution to boosted regression tree models of phosphorus deposition rates, highlighting the importance of river–floodplain connectivity for floodplain functioning and the profound impact of human activities that limit such connectivity. Patterns identified in our study may guide prioritization of restoration and conservation practices designed to capture sediment and phosphorus on floodplains.

Impacts of Forest Fire on Understory Species Diversity in Canary Pine Ecosystems on the Island of La Palma

Forest fires are drivers of spatial patterns and temporal dynamics of vegetation and biodiversity. On the Canary Islands, large areas of pine forest exist, dominated by the endemic Canary Island pine, Pinus canariensis C. Sm. These mostly natural forests experience wildfires frequently. P. canariensis is well-adapted to such impacts and has the ability to re-sprout from both stems and branches. In recent decades, however, anthropogenically caused fires have increased, and climate change further enhances the likelihood of large forest fires. Through its dense, long needles, P. canariensis promotes cloud precipitation, which is an important ecosystem service for the freshwater supply of islands such as La Palma. Thus, it is important to understand the regeneration and vegetation dynamics of these ecosystems after fire. Here, we investigated species diversity patterns in the understory vegetation of P. canariensis forests after the large 2016 fire on the southern slopes of La Palma. We analyzed the effect of fire intensity, derived from Sentinel-2 NDVI differences, and of environmental variables, on species richness (alpha diversity) and compositional dissimilarity (beta diversity). We used redundancy analysis (dbRDA), Bray–Curtis dissimilarity, and variance partitioning for this analysis. Fire intensity accounted for a relatively small proportion of variation in alpha and beta diversity, while elevation was the most important predictor. Our results also reveal the important role of the endemic Lotus campylocladus ssp. hillebrandii (Christ) Sandral & D.D.Sokoloff for understory diversity after fire. Its dominance likely reduces the ability of other species to establish by taking up nutrients and water and by shading the ground. The mid- to long-term effects are unclear since Lotus is an important nitrogen fixer in P. canariensis forests and can reduce post-fire soil erosion on steep slopes.

Geographic variability in lingcod Ophiodon elongatus life history and demography along the US West Coast: oceanographic drivers and management implications

Understanding the environmental and anthropogenic drivers of spatial patterns in life history variation for exploited fish populations is important when making management decisions and designating stock boundaries. These considerations are especially germane for stocks that are overfished or recently rebuilt, such as lingcodOphiodon elongatus, a commercially and recreationally valuable species of groundfish along the West Coast of North America. Between 2015 and 2017, we collected 2189 lingcod from 24 port locations, spanning 28° of latitude from southeast Alaska (60°N) to southern California (32°N), to investigate latitudinal patterns in size- and age-structure, growth, timing of maturity, condition, and mortality, as well as to identify biologically relevant population breakpoints along the coast. We found strong latitudinal patterns in these life history and demographic traits consistent with Bergmann’s rule: lingcod from colder, northern waters were larger-at-age, lived longer, matured at larger sizes, and had lower natural mortality rates than lingcod from warmer, southern waters. Female lingcod were larger-at-age, lived longer, and matured at larger sizes compared to males within each examined region. In addition, we found evidence for strong associations between lingcod life history traits and the oceanographic variables of sea surface temperature and chlorophylla. Cluster analysis using life history traits indicated that central Oregon is a biologically relevant breakpoint for lingcod along the US West Coast. This breakpoint based on life history traits, in conjunction with a recently identified population genetic breakpoint between central and northern California, highlights the need for future lingcod stock assessments to consider multiple sources of information to best inform management of this trans-boundary stock.

Temperature change as a driver of spatial patterns and long-term trends in chironomid (Insecta: Diptera) diversity.

Anthropogenic activities have led to a global decline in biodiversity, and monitoring studies indicate that both insect communities and wetland ecosystems are particularly affected. However, there is a need for long-term data (over centennial or millennial timescales) to better understand natural community dynamics and the processes that govern the observed trends. Chironomids (Insecta: Diptera: Chironomidae) are often the most abundant insects in lake ecosystems, sensitive to environmental change, and, because their larval exoskeleton head capsules preserve well in lake sediments, they provide a unique record of insect community dynamics through time. Here, we provide the results of a metadata analysis of chironomid diversity across a range of spatial and temporal scales. First, we analyse spatial trends in chironomid diversity using Northern Hemispheric data sets overall consisting of 837 lakes. Our results indicate that in most of our data sets, summer temperature (Tjul ) is strongly associated with spatial trends in modern-day chironomid diversity. We observe a strong increase in chironomid alpha diversity with increasing Tjul in regions with present-day Tjul between 2.5 and 14°C. In some areas with Tjul >14°C, chironomid diversity stabilizes or declines. Second, we demonstrate that the direction and amplitude of change in alpha diversity in a compilation of subfossil chironomid records spanning the last glacial-interglacial transition (~15,000-11,000years ago) are similar to those observed in our modern data. A compilation of Holocene records shows that during phases when the amplitude of temperature change was small, site-specific factors had a greater influence on the chironomid fauna obscuring the chironomid diversity-temperature relationship. Our results imply expected overall chironomid diversity increases in colder regions such as the Arctic under sustained global warming, but with complex and not necessarily predictable responses for individual sites.

Remotely sensed canopy nitrogen correlates with nitrous oxide emissions in a lowland tropical rainforest.

Tropical forests exhibit significant heterogeneity in plant functional and chemical traits that may contribute to spatial patterns of key soil biogeochemical processes, such as carbon storage and greenhouse gas emissions. Although tropical forests are the largest ecosystem source of nitrous oxide (N2 O), drivers of spatial patterns within forests are poorly resolved. Here, we show that local variation in canopy foliar N, mapped by remote-sensing image spectroscopy, correlates with patterns of soil N2 O emission from a lowland tropical rainforest. We identified ten 0.25ha plots (assemblages of 40-70 individual trees) in which average remotely-sensed canopy N fell above or below the regional mean. The plots were located on a single minimally-dissected terrace (<1km2 ) where soil type, vegetation structure and climatic conditions were relatively constant. We measured N2 O fluxes monthly for 1yr and found that high canopy N species assemblages had on average three-fold higher total mean N2 O fluxes than nearby lower canopy N areas. These differences are consistent with strong differences in litter stoichiometry, nitrification rates and soil nitrate concentrations. Canopy N status was also associated with microbial community characteristics: lower canopy N plots had two-fold greater soil fungal to bacterial ratios and a significantly lower abundance of ammonia-oxidizing archaea, although genes associated with denitrification (nirS, nirK, nosZ) showed no relationship with N2 O flux. Overall, landscape emissions from this ecosystem are at the lowest end of the spectrum reported for tropical forests, consist with multiple metrics indicating that these highly productive forests retain N tightly and have low plant-available losses. These data point to connections between canopy and soil processes that have largely been overlooked as a driver of denitrification. Defining relationships between remotely-sensed plant traits and soil processes offers the chance to map these processes at large scales, potentially increasing our ability to predict N2 O emissions in heterogeneous landscapes.

Past disturbances and intraspecific competition as drivers of spatial pattern in primary spruce forests

AbstractThe role of density dependence in shaping spatial patterns in tree distributions presumably changes throughout stand development. However, empirical investigations into developmental processes are often limited by a lack of long‐term data on disturbance history, which further limits the ability to assess the role of spatial variation in site conditions (e.g., slope, aspect, mean annual temperature). This study included data from 289 plots within 26 primary forest stands of the Carpathian Mountains; stands were dominated by Norway spruce (Picea abies) and driven by mixed‐severity disturbance regimes. We assessed spatial patterns in living tree positions, tree diameters, and the relative position of living trees to dead trees. Random forest classification was used to discriminate between disturbance history, tree density, and site conditions and their effects on the observed spatial patterns. At the stand scale, distances between trees of equal diameter were more uniform that expected (tree diameter was showing repulsion), while tree positions and dead trees were mostly distributed randomly. The processes that best explained the spatial patterns were identified as self‐thinning mortality and past disturbances (100–150 yr). This study demonstrated that the plot and stand‐scale spatial patterns resulted from the combination of past disturbances and density‐dependent legacies derived from earlier forest development stages.

Spatial patterns and environmental drivers of benthic infaunal community structure and ecosystem function on the New Zealand continental margin

To investigate regional drivers of spatial patterns in macro- and meio-faunal community structure (abundance, biomass and taxonomic diversity) and ecosystem function (sediment community oxygen consumption [SCOC]), we sampled two regions in close proximity on New Zealand's continental margin—the Chatham Rise and the Challenger Plateau. Sites (n = 15) were selected in water depths ranging from 266–1212 m to generate a gradient in sedimentary properties and, in particular, surface pelagic productivity. Both macro- and meio-fauna abundance and biomass was 2–3.5 times higher on the Chatham Rise than on the Challenger Plateau, reflecting regional differences in pelagic primary production. We also found significant inter- and intra-regional differences in macro-fauna taxonomic diversity with two distinctive site groupings in each region. Univariate and multivariate measures of macro-fauna community attributes were most strongly correlated with sediment photosynthetic pigment (explaining 24%–59% of the variation). Sediment pigment content was as equally important in explaining meio-fauna community structure (36%–7%). Unlike community structure, SCOC was most strongly correlated with depth (44%), most likely reflecting temperature effects on benthic metabolism. Our results highlight the importance of a benthic labile food supply in structuring infaunal communities on continental margins and emphasise a tight coupling between pelagic and benthic habitats.

Land use dynamics and the environment

This paper builds a benchmark framework to study optimal land use, encompassing land use activities and environmental degradation. We focus on the spatial externalities of land use as drivers of spatial patterns: land is immobile by nature, but local actions affect the whole space since pollution flows across locations resulting in both local and global damages. We prove that the decision maker problem has a solution, and characterize the corresponding social optimum trajectories by means of the Pontryagin conditions. We also show that the existence and uniqueness of time-invariant solutions are not in general guaranteed. Finally, a global dynamic algorithm is proposed in order to illustrate the spatial-dynamic richness of the model. We find that our simple set-up already reproduces a great variety of spatial patterns related to the interaction between land use activities and the environment. In particular, abatement technology turns out to play a central role as pollution stabilizer, allowing the economy to reach a time-invariant equilibrium that can be spatially heterogeneous.

Multi‐scale determinants of dung beetle assemblage structure across abiotic gradients of the Kalahari–Nama Karoo ecotone, South Africa

AbstractAim Changing conditions across spatial gradients are primary determinants of biotic regions, local habitats, and distributional edges. We investigate how a climatic gradient and edaphic mosaic interact as multi‐scale drivers of spatial patterns in scarabaeine dung beetles. The patterns are tested for congruency with ecoregion and floral boundaries over the same gradient, as responses to physical factors often differ among higher taxa.Location Southern Africa and the Nama Karoo–Kalahari ecotone, Northern Cape, South Africa.Methods Data consisted of the climatic distributions of 104 species and their abundances at 223 sites in two ecoregions/floral biomes, four bioregions, and 13 vegetation units. Factor analyses determined the biogeographical composition of the species, and regional‐ to local‐scale patterns in species abundance structure. Hierarchical analysis of oblique factors determined the proportional contribution of spatial variance to patterns. One‐wayanovawas used to test for significant separation of patterns along factor axes. Stepwise multiple regression was used to determine correlations of five physical attributes with species richness, Shannon‐Wiener diversity, and factor loadings for the study sites.Results Four biogeographical influences overlap in the study region, although rank contribution declines from south‐west arid through north‐east savanna to widespread and south‐east highland taxa. Species abundance structure comprises five subregional patterns, two centred to the north‐east (Kalahari, Isolated Kalahari Dune) dominated by Kalahari influence, and three to the south‐west (Nama Karoo subdivisions: Bushmanland, ‘Upper’, ‘Stony Prieska’) dominated by south‐west arid influence. Kalahari deep sands are characterized especially by a warmer, moister climate, whereas the Nama Karoo mosaic of deep or stony soils is characterized especially by north‐west aridity (Bushmanland), south‐east cooler temperatures (‘Upper’), or excessively stony soils (‘Stony Prieska’). Four of the subregional patterns each comprised three localized patterns related primarily to relative stoniness, edge effects from geographical position, or incidence of rainfall. Species richness and diversity declined with decreasing rainfall and increasing stoniness.Main conclusions Climatic and edaphic factors are important multi‐scale determinants of spatial patterns in dung beetle assemblage structure, with edaphic factors becoming more important at local spatial scales. The patterns are roughly congruent with the Kalahari Savanna–Nama Karoo ecotone at the floral biome or ecoregion scale, but show limited coincidence with finer‐scale floral classification.

Scenarios of Future Urban Land Use in Europe

The objective of this paper is to present the development of quantitative, spatially explicit, and alternative scenarios of future urban land use in Europe. The scenario-construction methodology is based on three steps: (1) an interpretation of four global-scale storylines describing in qualitative terms alternative urban-development pathways, (2) the development and application of a simple statistical model to estimate the future demand for urban land, and (3) the development of rules to allocate this urban demand geographically through the consideration of land-use planning goals. The qualitative part of the analysis is based on an interpretation of the four storylines of the Special Report on Emission Scenarios by the Intergovernmental Panel on Climate Change. This interpretation describes the principal driving forces that are specific to the European region and to the urban sector on the basis of the theoretical principles of urban economy. The urban-demand model includes two driving forces: (a) the population, representing demographic trends and the demand for housing; and (b) the gross domestic product, reflecting the economic level and dynamism. A further three variables are used as drivers of spatial patterns: (c) accessibility to the transport network; (d) the degree of restriction arising from land-use planning policy, and (e) the relative attractiveness (in terms of residential-location choice) of small, medium, and large cities. Thus, the urban-land-use change model is based on a multilevel analysis, which integrates theory and empirical evidence. The results are original urban-land-use maps of Europe for each of the four scenarios on the basis of a 10′ (latitude and longitude) geographic grid. The comparison of these alternative views of the future and the transparency of the development of these views provide a rich and consistent method for understanding the relationships between driving forces, their intensity, and their consequence for geographic space. Scenario analysis is a useful tool to test incentives, measures, or planning regulations according to different policy objectives.