Dataset Information

Ecological contingency in the effects of climatic warming on forest herb communities.

ABSTRACT: Downscaling from the predictions of general climate models is critical to current strategies for mitigating species loss caused by climate change. A key impediment to this downscaling is that we lack a fully developed understanding of how variation in physical, biological, or land-use characteristics mediates the effects of climate change on ecological communities within regions. We analyzed change in understory herb communities over a 60-y period (1949/1951-2007/2009) in a complex montane landscape (the Siskiyou Mountains, Oregon) where mean temperatures have increased 2 °C since 1948, similar to projections for other terrestrial communities. Our 185 sites included primary and secondary-growth lower montane forests (500-1.200 m above sea level) and primary upper montane to subalpine forests (1,500-2,100 m above sea level). In lower montane forests, regardless of land-use history, we found multiple herb-community changes consistent with an effectively drier climate, including lower mean specific leaf area, lower relative cover by species of northern biogeographic affinity, and greater compositional resemblance to communities in southerly topographic positions. At higher elevations we found qualitatively different and more modest changes, including increases in herbs of northern biogeographic affinity and in forest canopy cover. Our results provide community-level validation of predicted nonlinearities in climate change effects.

SUBMITTER: Harrison S

PROVIDER: S-EPMC2984146 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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Ecological contingency in the effects of climatic warming on forest herb communities.

Harrison Susan S Damschen Ellen I EI Grace James B JB

Proceedings of the National Academy of Sciences of the United States of America 20101025 45

Downscaling from the predictions of general climate models is critical to current strategies for mitigating species loss caused by climate change. A key impediment to this downscaling is that we lack a fully developed understanding of how variation in physical, biological, or land-use characteristics mediates the effects of climate change on ecological communities within regions. We analyzed change in understory herb communities over a 60-y period (1949/1951-2007/2009) in a complex montane lands ...[more]

PMID: 20974978

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Project description:Ecological strategies identified by plant functional traits are valuable descriptors for understanding species, populations, communities, and ecosystems in response to environmental conditions. Ecological strategies, in conjunction with the functional structure of plant communities, serve as crucial tools for investigating complex relationships among the environment, vegetation, and ecosystem functions. However, it remains unclear whether the functional structure (specifically, community-weighted mean [CWM] traits) accurately reflects the optimal ecological strategies in forest communities. Here, we gathered seven functional traits for each species from four distinct forest vegetation types across four climatic zones, including leaf area (LA), specific leaf area (SLA), leaf dry matter content (LDMC), leaf phosphorus concentration (LPC), leaf nitrogen concentration (LNC), wood density (WD) and maximum plant height (H). We based on CSR (Competitors, Stress-tolerators, Ruderals) theory and "StrateFy" ordination method utilizing LA, LDMC and SLA to position them within CSR triangle and categorize them into four ecological strategy groups: Competitive, Stress-tolerant, Intermediate, and Ruderal ecological strategy groups (C-group, S-group, Int-group, and R-group). We then determined the proportion of species in each group. Subsequently, we calculated the CWM trait values for the remaining four functional traits: WD (CWM-WD), LPC (CWM-LPC), LNC (CWM-LNC) and H (CWM-H). Non-metric multidimensional scaling and hierarchical partitioning revealed that CWM-WD, CWM-LPC, CWM-LNC and CWM-H significantly influenced the ecological strategies of forest communities. The synergistic interaction of CWM-WD and CWM-LPC had the most significant impact on ecological strategies within forest communities. Notably, CWM-WD emerged as the most crucial single CWM trait for explaining variation in ecological strategies within forest communities. In conclusion, our study demonstrates that CWM traits effectively reflect optimal CSR ecological strategies in forest communities across different climatic zones, with CWM-WD serving as a preferred indicator. This can improve our critical insights into key ecological processes in forest communities using trait-based approach.

Project description:Kelp forests provide important ecosystem services, yet coastal kelp communities are increasingly altered by anthropogenic impacts. Kelp forests in remote, offshore locations may provide an informative contrast due to reduced impacts from local stressors. We tested the hypothesis that shallow kelp assemblages (12-15 m depth) and associated fish and benthic communities in the coastal southwest Gulf of Maine (GOM) differed significantly from sites on Cashes Ledge, 145 km offshore by sampling five coastal and three offshore sites at 43.0 +/- 0.07° N latitude. Offshore sites on Cashes Ledge supported the greatest density (47.8 plants m2) and standing crop biomass (5.5 kg m2 fresh weight) of the foundation species Saccharina latissima kelp at this depth in the Western North Atlantic. Offshore densities of S. latissima were over 150 times greater than at coastal sites, with similar but lower magnitude trends for congeneric S. digitata. Despite these differences, S. latissima underwent a significant 36.2% decrease between 1987 and 2015 on Cashes Ledge, concurrent with a rapid warming of the GOM and invasion by the kelp-encrusting bryozoan Membranipora membranacea. In contrast to kelp, the invasive red alga Dasysiphonia japonica was significantly more abundant at coastal sites, suggesting light or dispersal limitation offshore. Spatial differences in fish abundance mirrored those of kelp, as the average biomass of all fish on Cashes Ledge was 305 times greater than at the coastal sites. Remote video censuses of cod (Gadus morhua), cunner (Tautaogolabrus adspersus), and pollock (Pollachius virens) corroborated these findings. Understory benthic communities also differed between regions, with greater abundance of sessile invertebrates offshore. Populations of kelp-consuming sea urchins Stronglyocentrotus droebachiensis, were virtually absent from Cashes Ledge while small urchins were abundant onshore, suggesting recruitment limitation offshore. Despite widespread warming of the GOM since 1987, extraordinary spatial differences in the abundance of primary producers (kelp), consumers (cod) and benthic communities between coastal and offshore sites have persisted. The shallow kelp forest communities offshore on Cashes Ledge represent an oasis of unusually high kelp and fish abundance in the region, and as such, comprise a persistent abundance hotspot that is functionally significant for sustained biological productivity of offshore regions of the Gulf of Maine.

Dataset Information

Ecological contingency in the effects of climatic warming on forest herb communities.

Publications

Ecological contingency in the effects of climatic warming on forest herb communities.

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