Exogenous Factors. Second-tier variables relating to the exogenous factors in the broader environmental and social-economic-political systems of which urban forests are a part. Abbreviations in the “Other UF frameworks” column correspond to shorthand citation keys for frameworks described in Table 2. Notes for Table 3 through Table 9 appear in Appendix D. UFSES (urban forest social-ecological system); UF (urban forest).
| Second-tier variable | Description and possible third-tier variables | Other UF frameworks |
|---|---|---|
| Broader Environmental Context & Dynamics (ENV) | ||
| Biome characteristics | Climate (landscape-level), type of native biome/ecosystem, topography, pre-urbanization vegetation and land cover, etc. | MORT, PAT |
| Earth system processes | Climate change, stratospheric ozone depletion, atmospheric aerosol loading, ocean acidification, biogeochemical flows, freshwater change, land system change, biosphere integrity, novel entities (Note 37). | NBS |
| Polycentricity of Earth systems | Nested, multilevel, multiscale; from cellular- to organism- to landscape- and continent-level; from mitosis to global biogeophysical cycles and weather patterns, etc. (Note 38). | NBS |
| Ecological Disturbances (ED) | ||
| “Pulse” disturbances | Ecological disturbances that occur at a relatively discrete period in time (measurable in hours or days) and onset is often sudden; can be predictable or unpredictable. Examples include storms and extreme weather events (thunderstorm, tornado, hurricane, derecho/flatline winds, polar vortex/extreme cold, ice storms, blizzard, heat dome/extreme heat events, dust storm, etc.), fires at the wildland-urban interface, some kinds of pest and disease outbreaks, etc. | VULN, LEG |
| “Press” disturbances | Ecological disturbances that occur more gradually over relatively longer periods of time than “pulse” disturbances, such as gradually increasing temperatures due to climate change, long term changes in precipitation patterns including flood/drought, El Niño/La Niña multiyear weather cycles, etc.; some kinds of pest and disease outbreaks that come on more gradually and persist long term might be “press” disturbances. | CC, VULN, LEG |
| Characteristics of these disturbances | Magnitude, frequency, duration, extent (Note 39). | VULN, CC |
| Ecological Rules (ER)(Note 40) | ||
| Physical phenomena | Urban heat island effect, light penetration, air pollutant dispersal, etc. | VULN |
| Biogeochemical phenomena | Photosynthesis and flows of nutrients through urban ecosystems, soil processes, etc. | |
| Biological/ecological phenomena | Competition between individual organisms and between species, natural selection and evolutionary processes, ecological succession, landscape fragmentation and patch dynamics, etc. | |
| Larger Social, Economic, and Political Context & Dynamics (SOC) | ||
| Human legacies | Historical decisions around tree planting/care, including species symbolism, civic beautification movements, park creation, street tree planting, national and regional identity as connected to trees or forests, trends in urban design and development, political popularity or unpopularity of trees and forests, etc. (Note 41). | LEG |
| Sub-national (state/provincial, county/municipal) government factors | Policies, laws, regulations, initiatives, funding, etc. at a level larger or higher up than the level of analysis for the system of interest. | MORT |
| National and multinational government factors | Policies, laws, regulations, initiatives, funding, etc. at the single country level (e.g., Spain) or higher (e.g., the European Union). | MORT |
| Largescale social and economic systems | Geopolitical stability, epidemics/pandemics, market economics/incentives, old/new/social media influences, national/global demographic trends, cultural paradigms, etc. | PAT, NBS |
| Polycentricity of governance structures | Nested multilevel, multiscale; management of urban forests within a single place is nested within larger regional, state/provincial, national, and international levels of governance and across public, private, nonprofit, and informal sectors (Note 42). | NBS |