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- Komatsu, Kimberly J., et al.
(författare)
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Global change effects on plant communities are magnified by time and the number of global change factors imposed
- 2019
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 116:36, s. 17867-17873
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Tidskriftsartikel (refereegranskat)abstract
- Accurate prediction of community responses to global change drivers (GCDs) is critical given the effects of biodiversity on ecosystem services. There is consensus that human activities are driving species extinctions at the global scale, but debate remains over whether GCDs are systematically altering local communities worldwide. Across 105 experiments that included over 400 experimental manipulations, we found evidence for a lagged response of herbaceous plant communities to GCDs caused by shifts in the identities and relative abundances of species, often without a corresponding difference in species richness. These results provide evidence that community responses are pervasive across a wide variety of GCDs on long-term temporal scales and that these responses increase in strength when multiple GCDs are simultaneously imposed.Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (<10 y). In contrast, long-term (≥10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated, suggesting the emergence of additive or synergistic effects of multiple drivers, particularly over long time periods. In half of the cases, GCD manipulations caused a difference in community composition without a corresponding species richness difference, indicating that species reordering or replacement is an important mechanism of community responses to GCDs and should be given greater consideration when examining consequences of GCDs for the biodiversity–ecosystem function relationship. Human activities are currently driving unparalleled global changes worldwide. Our analyses provide the most comprehensive evidence to date that these human activities may have widespread impacts on plant community composition globally, which will increase in frequency over time and be greater in areas where communities face multiple GCDs simultaneously.
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| 3. |
- Park, J. -B, et al.
(författare)
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Periodontal regeneration in class III furcation defects of beagle dogs using guided tissue regenerative therapy with platelet-derived growth factor
- 1995
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Ingår i: Journal of Periodontology. - : John Wiley & Sons. - 0022-3492 .- 1943-3670. ; 66:6, s. 462-477
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Tidskriftsartikel (refereegranskat)abstract
- We developed an effective regenerative therapy, referred to as platelet-derived growth factor-BB (PDGF-BB)-modulated guided tissue regenerative (GTR) therapy (P-GTR), capable of achieving periodontal regeneration of horizontal (Class III) furcation defects in the beagle dog. To determine its efficacy, repair and regeneration of horizontal furcation defects by P-GTR therapy and GTR therapy were compared. Chronically inflamed horizontal furcation defects were created around the second (P2) and fourth mandibular premolars (P4). After demineralization of the root surfaces with citric acid, the surfaces of left P2 and P4 were treated with PDGF-BB (P-GTR therapy) and those of contralateral teeth were treated with vehicle only (GTR therapy). Periodontal membranes were placed and retained 0.5 mm above the cemento-enamel junction for both groups. The mucoperiosteal flap was sutured in a coronal position and plaque control was achieved by daily irrigation with 2% chlorhexidine gluconate. At 5, 8, and 11 weeks, two animals each were sacrificed by perfusion with 2.5% glutaraldehyde through the carotid arteries, and the lesions were sliced mesio-distally, demineralized, dehydrated, and embedded. Periodontal healing and regeneration after GTR and P-GTR therapy were compared by histomorphometric as well as morphological analysis. Morphometric analysis for each time period was performed on the pooled samples of P2 and P4. Five weeks after both therapies, the lesions were filled primarily by tissue-free area, epithelium, inflamed tissue, and a small amount of newly formed fibrous connective tissue. At 8 and 11 weeks after P-GTR therapy, there was a statistically greater amount of bone and periodontal ligament formed in the lesions. The newly formed bone filled 80% of the lesion at 8 weeks and 87% at 11 weeks with P-GTR therapy, compared to 14% of the lesion at 8 weeks and 60% at 11 weeks with GTR therapy. Also, with P-GTR therapy there was less epithelium and tissue-free area, less inflamed tissue, and less connective tissue. Morphological analysis indicated that the defects around P2 revealed faster periodontal repair and regeneration than those around P4. While the lesions around P2 were effectively regenerated by 11 weeks even after GTR therapy, those around P4 failed to regenerate. On the other hand, P-GTR therapy further promoted periodontal repair and regeneration so that at 8 weeks the lesions around P2 and P4 demonstrated complete and nearly complete regeneration, respectively. Interestingly, P-GTR therapy stimulated formation of fibrous connective tissue compared to GTR therapy in the early stages of repair, thereby filling the wound space with the tissue and stabilizing the wound. Later, the fibrous connective tissue was found to be mineralized into bone or cementum depending on locations during remodeling. Consequently, P-GTR therapy effectively promoted periodontal regeneration with reproducibility.
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