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1.
Climate and topography are two important controls on spatial patterns of fire disturbance in forests globally, via their influence
on fuel moisture and fuel production. To assess the influences of climate and topography on fire disturbance patterns in a
temperate forest region, we analyzed the mapped perimeters of fires that burned during 1930–2003 in two national parks in
the eastern United States. These were Great Smoky Mountains National Park (GSMNP) in the southern Appalachian Mountains and
Shenandoah National Park (SNP) in the central Appalachian Mountains. We conducted GIS analyses to assess trends in area burned
under differing climatic conditions and across topographic gradients (elevation, slope position, and aspect). We developed
a Classification and Regression Tree model in order to further explore the interactions between topography, climate, and fire.
The results demonstrate that climate is a strong driver of both spatial and temporal patterns of wildfire. Fire was most prevalent
in the drier SNP than the wetter GSMNP, and during drought years in both parks. Topography also influenced fire occurrence,
with relatively dry south-facing aspects, ridges, and lower elevations burning most frequently. However, the strength of topographic
trends varied according to the climatic context. Weaker topographic trends emerged in the drier SNP than GSMNP, and during
low-PDSI (dry) years than high-PDSI (wet) years in both parks. The apparent influence of climate on the spatial patterning
of fire suggests a more general concept, that disturbance-prone landscapes exhibit weaker fine-scale spatial patterning of
disturbance than do less disturbance-prone landscapes. 相似文献
2.
Forest compositional shifts in response to climate change are likely to be initially detectable in the understory tree regeneration layer near species range limits. Because many factors in addition to climate, such as seedbed and soil characteristics, overstory composition, and interactions with other understory biota, drive tree regeneration trends, a thorough understanding of the relative importance of all variables as well as their interrelationships is needed. The range limits of several widespread temperate and boreal tree species overlap in the upper Great Lakes region, USA, thus facilitating an observational study over relatively short regional climate gradients. We used redundancy analysis and variation partitioning to quantify the unique, shared, and total explanatory power of four sets of explanatory variables. The results showed that all four variable sets (climate 9.5 %, understory environment 13.7 %, overstory composition 26.3 %, and understory biota 13.8 %) were significantly associated with tree regeneration compositional variation in mixed temperate–boreal forests. Partitioning also revealed high confounded or shared explanatory power, but also that each set contributed significant unique explanatory power not shared with other sets. Spatial patterning in regeneration composition was strongly related to broad scale environmental patterns, while the large majority of unexplained variation did not have a detectable spatial structure, suggesting factors with local scale variability. Future forest shifts across the landscape will depend not only on the rate and direction of climate change but also on how the strengths and interrelationships among other explanatory variables, such as overstory composition and understory biota, shift with a changing climate. 相似文献
3.
Urban trees store and sequester large amounts of carbon and are a vital component of natural climate solutions. Despite the well-recognized carbon benefits of urban trees, there is limited effort to examine how spatial distribution of carbon density varies across distinctive social, demographic, and built dimensions of urban landscapes. Moreover, it is unclear whether specific aspects of landscape structure and design could help increase carbon densities in urban trees. Here, we produced a fine-resolution carbon density map of urban trees in New York City (NYC) by integrating high-resolution land cover map, LiDAR-derived tree metrics, i-Tree Eco, and field survey data. We then explored spatial variations of carbon density across the gradients of urban development intensity, social deprivation index, and neighborhood age, and we examined the relationships between carbon density, and fragmentation, aggregation, size, and shape of tree canopy cover. We find that carbon stored in urban trees in NYC is estimated as 1078 Gg, with an average density of 13.8 Mg/ha. This large amount of carbon is unevenly distributed, with carbon densities being highest in Bronx and in open parks and street trees. Furthermore, carbon densities are negatively associated with urban development intensity and the social gradient of deprivation. Regarding the impacts of tree morphology on carbon density, our results show that while the amount of tree cover is the most influential factor in determining carbon density, small-sized forest patches and moderate levels of forest edges are also conductive to increasing carbon densities of urban trees. To incorporate urban forestry into developing innovative, effective, and equitable climate mitigation strategies, planners and decision makers need to identify the optimal spatial configuration of urban forests and invest in tree planting programs in marginalized communities. 相似文献
4.
Tree diversity is one of the most important components of urban ecosystems, because it provides multiple ecological benefits and contributes to human well-being. However, the distribution of urban trees may be spatially segregated and change over time. To provide insights for a better distribution of tree diversity in a socially segregated city, we evaluated spatial segregation in the abundance and diversity of trees by socioeconomic group and their change over a 12-year period in Santiago, Chile. Two hundred vegetation plots were sampled across Santiago in 2002 and 2014. We found that overall abundance and diversity of urban trees for the entire city were stable over 12 years, whereas species richness and abundance of native tree species increased. There was segregation in tree species richness and abundance by socioeconomic group, with wealthier areas having more species and greater abundance of trees (for all tree species and native species) than poorer ones. Tree community composition and structure varied with socioeconomic group, but we found no evidence of increased homogenization of the urban forest in that 12 years. Our findings revealed that although tree diversity and abundance for the entire city did not change in our 12-year period, there were important inequities in abundance and diversity of urban trees by socioeconomic group. Given that 43% of homes in Santiago are in the lower socioeconomic areas, our study highlights the importance of targeting tree planting, maintenance and educational programs in these areas to reduce inequalities in the distribution of trees. 相似文献
5.
Min Zhao Francisco J. Escobedo Christina Staudhammer 《Urban Forestry & Urban Greening》2010,9(3):205-214
Spatial patterns of tree structure and composition were studied to assess the effects of land tenure, management regimes, and the environment on a coastal, subtropical urban forest. A total of 229 plots in remnant natural areas, private residential, public non-residential, and private non-residential land tenures were analyzed in a 1273 km2 study area encompassing the urbanized portion of Miami-Dade County, USA. Statistical mixed models of structure, composition, location, and land tenure data were used to analyze spatial patterns across the study area. A total of 1200 trees were measured of which 593 trees (49%) were located in residential areas, 67 (6%) in public non-residential areas, 135 trees (11%) in private non-residential areas, and 405 (34%) in remnant, natural areas. A total of 107 different tree species belonging to 90 genera were sampled. Basal area in residential land tenures increased towards the coast while private residential land tenures and natural areas had higher species diversity than non-residential areas. Tree height, crown light exposure, and crown area might indicate the effects of past hurricane impacts on urban forest structure. Land tenure, soil types, and urban morphology influenced composition and structure. Broadleaf evergreen trees are the most common growth form, followed by broadleaf deciduous, palms, and conifers. Exotic tree species originated mainly from Asia and 15% of all trees measured were considered exotic-highly invasive species. We discuss the use of these results as an ecological basis for management and resilience towards hurricane damage and identifying occurrence of invasive, exotic trees. 相似文献
6.
7.
Andrew Koeser Richard Hauer Kelly Norris Randy Krouse 《Urban Forestry & Urban Greening》2013,12(4):562-568
Street trees are exposed to a variety of site conditions, environmental factors, and physical disturbances which influence their survival in urban areas. This study draws on 25 years of urban forest monitoring data from the city of Milwaukee, WI (United States) to model the impacts of these factors on tree survival for a single cohort of trees. Tree condition, tree size, tree species, and site attributes were measured initially in 1979. These factors were measured again in 1989 and 2005 and compared to construction data for the same area during the study period. Multivariate logistic regression was used to identify factors associated with tree survival. Cross-validation show the final model could successfully predict tree survival nearly 85% of the time. Results indicate that tree survival varied by species. Additionally, trees were more likely to die as trunk diameter increased, planting space width decreased in the tree lawn, and tree condition decreased. Finally, trees adjacent to construction were nearly twice as likely to die as those not exposed to development and redevelopment activities. 相似文献
8.
Horse chestnut (Aesculus hippocastanum L.) is a common urban tree species in Ljubljana, the capital of Slovenia. This area is forecast to experience a general reduction in precipitation and an increase in temperature, which increases water demand in plants. Because A. hippocastanum is known for its drought vulnerability, the question of the future suitability of this urban tree species in Ljubljana has arisen. To investigate how climate has influenced A. hippocastanum radial growth and how trees responded to extreme climatic events, standardized precipitation-evapotranspiration index (SPEI) was used as a proxy for water demand. Climatic signal and its stability through time were calculated using Pearson’s correlation coefficient. Additionally, to investigate whether the trees had a common response to extreme climatic events, pointer years were calculated using Cropper values. We sampled 19 trees that were growing in Tivoli Park in Ljubljana. After successful cross-dating of 15 trees, the ring count showed that the trees had up to 201 tree-rings and had 130 on average. Climate-tree growth analysis showed that in July, 3-month SPEI had the strongest influence on radial growth, but its influence on radial growth decreased over time, possibly due to the die-off process of trees. The narrowest tree-rings were a result of unusually dry periods at the time of cambium activity and/or new cell growth. With the forecast of longer, more frequent summer drought periods in Ljubljana, soil moisture stress will increase, and as a result, a decrease in radial tree growth of A. hippocastanum trees from Tivoli Park is expected. 相似文献
9.
Holocene palaeo-invasions: the link between pattern, process and scale in invasion ecology? 总被引：2，自引：1，他引：1
Lindsey Gillson Anneli Ekblom Katherine J. Willis Cynthia Froyd 《Landscape Ecology》2008,23(7):757-769
Invasion ecology has made rapid progress in recent years through synergies with landscape ecology, niche theory, evolutionary
ecology and the ecology of climate change. The palaeo-record of Holocene invasions provides a rich but presently underexploited
resource in exploring the pattern and process of invasions through time. In this paper, examples from the palaeo-literature
are used to illustrate the spread of species through time and space, also revealing how interactions between invader and invaded
communities change over the course of an invasion. The main issues addressed are adaptation and plant migration, ecological
and evolutionary interactions through time, disturbance history and the landscape ecology of invasive spread. We consider
invasions as a continuous variable, which may be influenced by different environmental or ecological variables at different
stages of the invasion process, and we use palaeoecological examples to describe how ecological interactions change over the
course of an invasion. Finally, the use of palaeoecological information to inform the management of invasions for biodiversity
conservation is discussed. 相似文献
10.
We assessed landscape-scale invasions of openings in mountain forests by native tree species since EuroAmerican settlement
(ca. 1870–1899). We reconstructed historical openings across a 250,240 ha area in the Medicine Bow Mountains, Wyoming, using
notes from the original General Land Office (GLO) surveys, and compared historical openings to modern openings interpreted
from digital aerial photography. We constructed logistic regression models to describe and predict tree invasion, based on
a set of environmental and land use predictors. Openings have decreased by about 7.3% in the last ca. 110 years. Invasion
was more likely to occur on moister sites, indicated by high values for steady-state wetness, low values for evaporative demand,
proximity to streams, and topographic settings in basins or channels. More invasion also occurred on unprotected public land,
in openings surrounded by lodgepole pine and aspen, and on mesic soils. The relatively slow rates of invasion in the study
area may be driven by climate and land use. 相似文献
11.
Linda A. Møller Anne-Marie T. Skou Johannes Kollmann 《Urban Forestry & Urban Greening》2012,11(1):59-64
Dispersal limitations contribute to shaping plant distribution patterns and thus are significant for biodiversity conservation and urban ecology. In fleshy-fruited plants, for example, any preference of frugivorous birds affects dispersal capacities of certain fruit species. We conducted a removal experiment with fruits of Ilex aquifolium, a species that is currently expanding its range margin in northern Europe in response to climate change. The species is also a popular ornamental tree and naturalization has been observed in many parts of its range. Fruits of native I. aquifolium and of three cultivars were offered to birds at the expanding range margin in urban habitats in eastern Denmark. The four fruit types were removed at different rates and red fruits were preferred over a yellow cultivar. Small fruit diameter was positively related to fruit removal, and removal was faster under tree canopies compared with open habitats. The preference for red cultivars compared with native I. aquifolium may contribute to naturalization and potential invasion of garden escapes. Preferential foraging under closed canopies indicates trees and shrubs as recruitment foci for fleshy-fruited plants in urban landscapes. The results should be included in urban forestry and planting of potentially invasive ornamental species. 相似文献
12.
Individual Tree Inventory (ITI) is critical for urban planning, including urban heat mitigation. However, an ITI is usually incomplete and costly due to data collection challenges in the dynamic urban landscape. This research developed a methodical GeoAI framework to build a comprehensive ITI and quantify tree species cooling on rising urban heat.The object detection Faster R-CNN model with Inception ResNet V2 was implemented to detect individual trees canopy and seven tree species (Callery pear, Chinese elm, English elm, Mugga ironbark, Plane tree, Spotted gum and White cedar). The land surface temperature (LST) was derived from Landsat 8 surface reflectance imagery. Two models for ITI were further developed for spatial and statistical analysis. Firstly, an ‘Individual tree-based model’ stores the attributes of tree species and its vertical configuration obtained from LiDAR, along with its tree canopy area and surface temperature. Secondly, the ‘LST zone-based model’ stores tree canopy cover and building areas in each zone unit. Pearson correlation, global linear regression, and geographically weighted regression (GWR) were applied to establish the relationship between tree attributes, building areas (explanatory variables) with local temperature (dependent variable). Results showed that English elm has the highest cooling and least by Mugga ironbark in the study area. GWR results demonstrate that 94% of the LST was explained by tree height and tree canopy area. The LST zone-based model showed that 85% of the LST was explained by the percentage of tree species and buildings. Maps of the local R2 and coefficients of the independent variables provide spatially explicit information on the cooling of different tree species compared to building areas. The implemented GeoAI approach provides important insights to urban planners and government to monitor urban trees with the enhanced Individual Tree Inventory and strategies mitigation plan to reduce the impact of climate change and global warming. 相似文献
13.
Improved knowledge of the environmental factors that affect woody composition is urgently required for species conservation in riparian zones of urbanizing landscapes. We investigated the environmental factors influencing tree abundance and regeneration in diverse forest types growing in the riparian area of an urbanizing landscape along the Chao Phraya River. We established 252 0.1-ha circular plots in remnant forest patches along 372 km of the river. Cluster analysis was applied to classify the forest types. The relationships between environmental variables and tree abundance were assessed with ordination analysis, and generalized linear models were used to assess seedling/sapling abundance. The cluster analysis revealed five forest types, including floodplain forest with three sub-forest types, swamp forest, and mangrove forest. The ordination indicated that tree abundance in the floodplain forest was positively affected by distance to the ocean and the proportion of forested area. Swamp forest was positively influenced by the proportion of urbanized area and mean rainfall. Mangrove forest was negatively related to distance to the river. Seedling/sapling abundance of the dominant species in the floodplain forests was positively affected by lowland plain topography and negatively affected by the proportion of urbanized area, whereas swamp and mangrove forest species were positively influenced by the proportion of urbanized area and estuarine topography. Mature tree density influenced seedling/sapling abundance of all forest types. Tree abundance and regeneration of the riparian landscape was prevented by the urbanized area, floodplain, estuarine topography, and mature tree densities in remnant forests. These results suggest that remnant forest patches of conserved riparian forests along the urbanized landscape of the Chao Phraya River must be protected and the factors determining their colonization must be considered to enhance restoration practices. 相似文献
14.
Tree canopy cover data from aerial photographs and building energy simulations were applied to estimate energy savings from existing trees and new plantings in California. There are approximately 177.3 million energy-conserving trees in California communities and 241.6 million empty planting sites. Existing trees are projected to reduce annual air conditioning energy use by 2.5% with a wholesale value of $ 485.8 million. Peak load reduction by existing trees saves utilities 10% valued at approximately $778.5 million annually, or $ 4.39/tree. Planting 50 million trees to shade east and west walls of residential buildings is projected to reduce cooling by 1.1% and peak load demand by 4.5% over a 15-year period. The present wholesale value of annual cooling reductions for the 15-year period is $ 3.6 billion ($ 71/tree planted). Assuming total planting and stewardship costs of $ 2.5 billion ($ 50/tree), the cost of peak load reduction is $ 63/kW, considerably less than the $ 150/kW benchmark for cost-effectiveness. Influences of tree location near buildings and regional climate differences on potential energy savings are discussed. 相似文献
15.
Climate change, human population growth, the energy crisis, and food insecurity negatively drive livelihoods in developing countries. The trend seems to be severe in arid and semi-arid areas where some livelihood strategies are naturally constrained. Tree planting is one of the mitigation and adaptation approaches applied to climate variability and change for sustainable development in sub-Saharan Africa. The current study assessed the status, determinants, and challenges of tree planting in Nkuhungu, Msalato, and Hombolo villages in the Dodoma district, Tanzania. A household questionnaire survey (HQS) was used to collect data from 213 household respondents. In-depth interviews and focus group discussions were used to supplement data from HQS. Results indicate that tree planting is practiced at household and institutional levels during the wet season and was promoted after the government shifted from Dar es Salaam to Dodoma. Approximately 5111 planted trees were recorded in the study villages, with an average of 24 ± 5 trees planted per household. Fruit and shade trees are widely planted in residential areas, and privately owned nurseries and the Tanzania Forest Services Agency (TFS) are the major sources of seedlings. Level of education (+), type of employment (-), seedling price (-), water availability (+), and the importance of the tree (+) were found to influence the number of trees planted by household respondents. The main challenges of tree planting are inadequate land size, water scarcity, high pricing of seedlings, lack of improved seeds, and insufficient extension services. Knowledge on tree planting determinants would be instrumental in strengthening the current governmental strategies for greening Dodoma. The study suggests increasing water sources such as boreholes and digging wells/ponds for watering trees; improvement of extension services; and provisioning of affordable improved and adaptive seeds to semi-arid areas. 相似文献
16.
Cristian Paltineanu Silvia Nicolae Nicolae Tanasescu Emil Chitu Sergiu Ancu 《Erwerbs-Obstbau》2017,59(1):29-37
Plum and apple trees are the most widely spread fruit trees in south-eastern Europe. The main purpose of this paper is to characterize the spatial distribution of roots in medium and course textured soils to improve orchard management. ’Stanley’ plum cultivar grafted on Saint Julien A semi-dwarf rootstock and ’Topaz’ apple cultivar grafted on M.9 dwarf rootstock were studied in a temperate climate and medium and course textured soils. The trench technique was used. There was an intense concentration of roots near the trees and the roots did not occupy the whole soil space between tree rows. The finest tree roots in both species were prevalent. Root density was higher in tree rows versus inter-rows. Both the inter-row and in-row distances can be reduced to increase tree density if light penetration into canopy is sufficient. When a full irrigation regime is applied, a soil depth of 0.8?m would be sufficient for water application, and soil depths of 0.4 to 0.6?m would be recommended for deficit irrigation; water and fertilizers should only be applied over the surface area covering most of the roots. When a more strict control on root activity is desired, the tree roots could be cut vertically at 0.5–0.8?m distance from tree rows. The results could also be used in regions and countries with similar soil texture and climate conditions. 相似文献
17.
Spiders associated with the meadow and tree canopies of orchards respond differently to habitat fragmentation 总被引：1，自引：0，他引：1
John D. Herrmann Debra Bailey Gabriela Hofer Felix Herzog Martin H. Schmidt-Entling 《Landscape Ecology》2010,25(9):1375-1384
The response of animal communities to habitat quality and fragmentation may vary depending on microhabitat associations of
species. For example, sensitivity of species to woody habitat fragmentation should increase with their degree of association
with woody plants. We investigated effects of local and landscape factors on spider communities in different microhabitats
within Swiss apple orchards. We expected a stronger negative effect of woody habitat fragmentation on spiders inhabiting tree
canopies compared to spiders living in the meadow. The 30 orchards that we sampled varied in woody habitat amount and isolation
at landscape and patch scales. Local factors included management intensity and plant diversity. Spiders associated with meadow
were affected by plant diversity, but not by fragmentation. In contrast, spiders associated with canopies responded to isolation
from other woody habitats. Surprisingly, we found both positive and negative effects of habitat isolation on local abundance.
This indicates that differences in dispersal and/or biotic interactions shape the specific response to habitat isolation.
The relative importance of local and landscape factors was in accordance with the microhabitat of the spiders. Thus, considering
microhabitat associations can be important for identifying processes that would be overlooked if sampling were pooled for
the whole habitat. 相似文献
18.
Tree failure is an increasingly frequent issue in cities worldwide leading to the risk of property damage, financial loss, citizen injury, and death. Assessing tree failure is a challenging task since early signs are often not visible and require a detailed evaluation of each tree, which is limiting considering the management of trees across the whole city. We used Regression Trees and Bagging to assess tree failure on the streets of São Paulo / Brazil using parameters from the gray and green infrastructure that could be easily estimated in the field to support the proper preventive maintenance of street trees. We characterized the districts’ age, average building height, tree height, canopy cover, sidewalk width, sidewalk slope, and terrain slope of 26,616 fallen trees. The Regression Tree shows 82% accuracy and reveals that building height is the main predictor of tree failure, followed by district age, sidewalk width, and tree height. The proportion of tree failure in the most verticalized areas, with on average five stories buildings or taller, is twice that observed in the entire city. Tree failure also increases in districts older than 42 years. The proportion of tree failure is 37% lower than the city’s average in relatively newer districts with low building height, where trees taller than 9.58 m are more prone to failure. These results point to possible roles of wind tunneling, shading, pollution, canopy conflicts with service cables in the urban canyons, and the natural senescence of trees in the oldest districts. The present study establishes comprehensive guidelines for effective preventive maintenance of the street trees in São Paulo. 相似文献
19.
Tree risk assessment is an inherently human endeavor that can be influenced by risk perception, risk acceptance, and professional bias. Tree risk assessments from 296 arborists were evaluated to assess tree- and assessor-based factors that influenced ratings. Additionally, we investigated sources of variability associated with the main inputs of risk assessment – likelihood of impact ratings, likelihood of failure ratings, and consequences of failure ratings. Finally, we assessed the factors that influenced prescribed mitigation measures. Results indicate that professionals with training and industry credentials had lower risk ratings and were less likely to prescribe more active mitigation measures like tree removal. More notably, there was significant variability among raters, with the likelihood of impact and consequence of failure serving as the most variable factors in tree risk assessment. 相似文献
20.
Urban forests produce ecosystem services that can benefit city dwellers, but are especially vulnerable to climate change stressors such as heat, drought, extreme winds and pests. Tree selection is an important decision point for managers wanting to transition to a more stable and resilient urban forest structure. This study describes a five-step process to identify and evaluate the performance of promising but infrequently used tree species. The approach is illustrated for the Central Valley of California, USA and has been implemented in the Inland Empire and Southern Coastal regions of California. Horticultural advisors nominated 134 taxon for consideration. A filtering process eliminated taxon that were relatively abundant in a compilation of 8 municipal tree inventories, then those with low adaptive capacity when scored on habitat suitability, physiology and biological interactions. In 2015, 144 trees were planted, with 2 trees of each of 12 species planted in 4 Sacramento parks and 4 replicates planted in the Davis, California reference site. This approach can serve as an international model for cities interested in climate adaptation through urban forestry. 相似文献