| 1. |
- Poorter, Lourens, et al.
(författare)
-
Wet and dry tropical forests show opposite successional pathways in wood density but converge over time
- 2019
-
Ingår i: Nature Ecology & Evolution. - : Nature Publishing Group. - 2397-334X. ; 3:6, s. 928-934
-
Tidskriftsartikel (refereegranskat)abstract
- Tropical forests are converted at an alarming rate for agricultural use and pastureland, but also regrow naturally through secondary succession. For successful forest restoration, it is essential to understand the mechanisms of secondary succession. These mechanisms may vary across forest types, but analyses across broad spatial scales are lacking. Here, we analyse forest recovery using 1,403 plots that differ in age since agricultural abandonment from 50 sites across the Neotropics. We analyse changes in community composition using species-specific stem wood density (WD), which is a key trait for plant growth, survival and forest carbon storage. In wet forest, succession proceeds from low towards high community WD (acquisitive towards conservative trait values), in line with standard successional theory. However, in dry forest, succession proceeds from high towards low community WD (conservative towards acquisitive trait values), probably because high WD reflects drought tolerance in harsh early successional environments. Dry season intensity drives WD recovery by influencing the start and trajectory of succession, resulting in convergence of the community WD over time as vegetation cover builds up. These ecological insights can be used to improve species selection for reforestation. Reforestation species selected to establish a first protective canopy layer should, among other criteria, ideally have a similar WD to the early successional communities that dominate under the prevailing macroclimatic conditions.
|
|
| 2. |
- Tromp, Jasper, et al.
(författare)
-
Serum Potassium Levels and Outcome in Acute Heart Failure (Data from the PROTECT and COACH Trials)
- 2017
-
Ingår i: American Journal of Cardiology. - : EXCERPTA MEDICA INC-ELSEVIER SCIENCE INC. - 0002-9149 .- 1879-1913. ; 119:2, s. 290-296
-
Tidskriftsartikel (refereegranskat)abstract
- Serum potassium is routinely measured at admission for acute heart failure (AHF), but information on association with clinical variables and prognosis is limited. Potassium measurements at admission were available in 1,867 patients with AHF in the original cohort of 2,033 patients included in the Patients Hospitalized with acute heart failure and Volume Overload to Assess Treatment Effect on Congestion and Renal FuncTion trial. Patients were grouped according to low potassium (amp;lt;3.5 mEq/l), normal potassium (3.5 to 5.0 mEq/l), and high potassium (amp;gt;5.0 mEq/l) levels. Results were verified in a validation cohort of 1,023 patients. Mean age of patients was 71 +/- 11 years, and 66% were men. Low potassium was present in 115 patients (6%), normal potassium in 1,576 (84%), and high potassium in 176 (9%). Potassium levels increased during hospitalization (0.18 +/- 0.69 mEq/l). Patients with high potassium more often used angiotensin-converting enzyme inhibitors and mineralocorticoid receptor antagonists before admission, had impaired baseline renal function and a better diuretic response (p = 0.005), independent of mineralocorticoid receptor antagonist usage. During 180-day follow-up, a total of 330 patients (18%) died. Potassium levels at admission showed a univariate linear association with mortality (hazard ratio [log] 2.36, 95% confidence interval 1.07 to 5.23; p = 0.034) but not after multivariate adjustment. Changes of potassium levels during hospitalization or potassium levels at discharge were not associated with outcome after multivariate analysis. Results in the validation cohort were similar to the index cohort. In conclusion, high potassium levels at admission are associated with an impaired renal function but a better diuretic response. Changes in potassium levels are common, and overall levels increase during hospitalization. In conclusion, potassium levels at admission or its change during hospitalization are not associated with mortality after multivariate adjustment. (C) 2016 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativeconunons.org/licenses/by/4.0/).
|
|
| 3. |
- Chazdon, Robin L., et al.
(författare)
-
Carbon sequestration potential of second-growth forest regeneration in the Latin American tropics
- 2016
-
Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 2:5
-
Tidskriftsartikel (refereegranskat)abstract
- Regrowth of tropical secondary forests following complete or nearly complete removal of forest vegetation actively stores carbon in aboveground biomass, partially counterbalancing carbon emissions from deforestation, forest degradation, burning of fossil fuels, and other anthropogenic sources. We estimate the age and spatial extent of lowland second-growth forests in the Latin American tropics and model their potential aboveground carbon accumulation over four decades. Our model shows that, in 2008, second-growth forests (1 to 60 years old) covered 2.4 million km2 of land (28.1% of the total study area). Over 40 years, these lands can potentially accumulate a total aboveground carbon stock of 8.48 Pg C (petagrams of carbon) in aboveground biomass via low-cost natural regeneration or assisted regeneration, corresponding to a total CO2 sequestration of 31.09 Pg CO2. This total is equivalent to carbon emissions from fossil fuel use and industrial processes in all of Latin America and the Caribbean from 1993 to 2014. Ten countries account for 95% of this carbon storage potential, led by Brazil, Colombia, Mexico, and Venezuela. We model future land-use scenarios to guide national carbon mitigation policies. Permitting natural regeneration on 40% of lowland pastures potentially stores an additional 2.0 Pg C over 40 years. Our study provides information and maps to guide national-level forest-based carbon mitigation plans on the basis of estimated rates of natural regeneration and pasture abandonment. Coupled with avoided deforestation and sustainable forest management, natural regeneration of second-growth forests provides a low-cost mechanism that yields a high carbon sequestration potential with multiple benefits for biodiversity and ecosystem services.
|
|
| 4. |
- Gei, Maga, et al.
(författare)
-
Legume abundance along successional and rainfall gradients in Neotropical forests
- 2018
-
Ingår i: Nature Ecology & Evolution. - : Springer Science and Business Media LLC. - 2397-334X. ; 2:7
-
Tidskriftsartikel (refereegranskat)abstract
- The nutrient demands of regrowing tropical forests are partly satisfied by nitrogen-fixing legume trees, but our understanding of the abundance of those species is biased towards wet tropical regions. Here we show how the abundance of Leguminosae is affected by both recovery from disturbance and large-scale rainfall gradients through a synthesis of forest inventory plots from a network of 42 Neotropical forest chronosequences. During the first three decades of natural forest regeneration, legume basal area is twice as high in dry compared with wet secondary forests. The tremendous ecological success of legumes in recently disturbed, water-limited forests is likely to be related to both their reduced leaflet size and ability to fix N2, which together enhance legume drought tolerance and water-use efficiency. Earth system models should incorporate these large-scale successional and climatic patterns of legume dominance to provide more accurate estimates of the maximum potential for natural nitrogen fixation across tropical forests.
|
|
| 5. |
- Kraai, Imke, et al.
(författare)
-
The value of telemonitoring and ICT-guided disease management in heart failure: Results from the IN TOUCH study
- 2016
-
Ingår i: International Journal of Medical Informatics. - : ELSEVIER IRELAND LTD. - 1386-5056 .- 1872-8243. ; 85:1, s. 53-60
-
Tidskriftsartikel (refereegranskat)abstract
- Aim: It is still unclear whether telemonitoring reduces hospitalization and mortality in heart failure (HF) patients and whether adding an Information and Computing Technology-guided-disease-management-system (ICT-guided-DMS) improves clinical and patient reported outcomes or reduces healthcare costs. Methods: A multicenter randomized controlled trial was performed testing the effects of INnovative ICT-guided-DMS combined with Telemonitoring in OUtpatient clinics for Chronic HF patients (IN TOUCH) with in total 179 patients (mean age 69 years; 72% male; 77% in New York Heart Association Classification (NYHA) III-IV; mean left ventricular ejection fraction was 28%). Patients were randomized to ICT-guided-DMS or to ICT-guided-DMS + telemonitoring with a follow-up of nine months. The composite endpoint included mortality, HF-readmission and change in health-related quality of life (HR-QoL). Results: In total 177 patients were eligible for analyses. The mean score of the primary composite endpoint was -0.63 in ICT-guided-DMS vs. -0.73 in ICT-guided-DMS + telemonitoring (mean difference 0.1,95% CI: -0.67 +0.82, p = 0.39). All-cause mortality in ICT-guided-DMS was 12% versus 15% in ICT-guided-DMS + telemonitoring (p = 0.27); HF-readmission 28% vs. 27% p = 0.87; all-cause readmission was 49% vs. 51% (p = 0.78). HR-QoL improved in most patients and was equal in both groups. Incremental costs were 1360 in favor of ICT-guided-DMS. ICT-guided-DMS + telemonitoring had significantly fewer HF-outpatient-clinic visits (p < 0.01). Conclusion: ICT-guided-DMS + telemonitoring for the management of HF patients did not affect the primary and secondary endpoints. However, we did find a reduction in visits to the HF-outpatient clinic in this group suggesting that telemonitoring might be safe to use in reorganizing HF-care with relatively low costs. (C) 2015 The Authors. Published by Elsevier Ireland Ltd. This is an open access article under the CC BY-NC-ND license (http://cleativecommons.org/licenses/by-nc-nd/4.0/).
|
|
| 6. |
|
|
| 7. |
- Egelkraut, Dagmar D., 1989-
(författare)
-
Long-lasting ecological legacies of reindeer on tundra vegetation
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Reindeer can have strong effects on the plant species composition and functioning of tundra ecosystems, and often promote a transition towards a graminoid-dominated vegetation type. As a result, they influence many ecological processes, such as nutrient dynamics, soil biotic composition and functioning, and carbon storage. Several studies suggest that the effect of reindeer on vegetation may follow predictable patterns and could induce an alternative stable vegetation state. However, little empirical data on the long-term stability of reindeer effects on vegetation exist, as it is inherently challenging to study these ecological processes experimentally on a sufficiently long timescale. The main objective of this thesis was therefore to gain a better understanding of the long-term ecological processes following reindeer-induced vegetation shifts.In order to gain a more mechanistic insight in what initially drives this transition, I used a field-based grazing simulation experiment in which I separated defoliation, trampling, moss removal and the addition of feces. This allowed me to test the relative contribution of reindeer-related activities to initiating the shift from moss and heath- dominated tundra towards a graminoid-dominated vegetation state. Additionally, I studied the long-term ecological stability following such a vegetation shift. I did this by addressing historical milking grounds (HMGs): sites where high reindeer concentrations associated with historical traditional reindeer herding practices induced a vegetation transition from shrubs towards graminoids several centuries earlier, but which were abandoned a century ago. Studying HMGs allowed me to address: 1. The potential stability of reindeer-induced vegetation shifts; 2. The ecological mechanisms contributing to the long-term stability of these vegetation shifts; and 3. How such long-lasting vegetation changes influence soil carbon- and nutrient cycling.I found that trampling by reindeer is an important mechanism by which reindeer cause vegetation change. Addressing HMGs further revealed that this vegetation change can be hightly persistent, as the studied HMGs showed only a low encroachment at the surrounding borders in the last 50 years. The vegetation in the core areas of all studied HMGs had remained strikingly stable, and were hardly invaded by surrounding shrubs. Interestingly, soil nutrient concentrations and microbial activities were still different from the surrounding area as well, and even comparable to actively grazed areas. Even after many centuries of changed vegetation composition and soil processes, there was no difference in total carbon sequestration. This suggests that the environmental conditions for microbial decomposition were more important than vegetation composition for the soil carbon stocks, in our study site.After studying the contemporary habitat use of HMGs by reindeer and other herbivores, investigating the potential plant-soil feedbacks mechanisms and detailed soil analyses, I concluded that several ecological mechanisms contribute to the long-term stability of HMGs: first, the altered soil biotic and abiotic conditions appear to have a stronger advantage for HMG vegetation than for the surrounding tundra vegetation. Furthermore, I found a clear browsing preference of small rodents on single shrubs proliferating in HMGs, causing a strong limitation on shrub expansion. Moreover, the dense established sward of graminoids likely poses a strong direct competition for space and nutrients, hindering seedling establishment. Finally, I conclude that HMGs are highly stable on relevant ecological timescales, and propose how the concepts of historical contingency and ASS can be applied to understand stability of these reindeer-induced vegetation transitions.
|
|
