Aim: Tropical forests account for a quarter of the global carbon storage and a third of the terrestrial productivity. Few studies have teased apart the relative importance of environmental factors ...and forest attributes for ecosystem functioning, especially for the tropics. This study aims to relate aboveground biomass (AGB) and biomass dynamics (i.e., net biomass productivity and its underlying demographic drivers: biomass recruitment, growth and mortality) to forest attributes (tree diversity, community-mean traits and stand basal area) and environmental conditions (water availability, soil fertility and disturbance). Location: Neotropics. Methods: We used data from 26 sites, 201 1-ha plots and >92,000 trees distributed across the Neotropics. We quantified for each site water availability and soil total exchangeable bases and for each plot three key community-weighted mean functional traits that are important for biomass stocks and productivity. We used structural equation models to test the hypothesis that all drivers have independent, positive effects on biomass stocks and dynamics. Results: Of the relationships analysed, vegetation attributes were more frequently associated significantly with biomass stocks and dynamics than environmental conditions (in 67 vs. 33% of the relationships). High climatic water availability increased biomass growth and stocks, light disturbance increased biomass growth, and soil bases had no effect. Rarefied tree species richness had consistent positive relationships with biomass stocks and dynamics, probably because of niche complementarity, but was not related to net biomass productivity. Community-mean traits were good predictors of biomass stocks and dynamics. Main conclusions: Water availability has a strong positive effect on biomass stocks and growth, and a future predicted increase in (atmospheric) drought might, therefore, potentially reduce carbon storage. Forest attributes, including species diversity and community-weighted mean traits, have independent and important relationships with AGB stocks, dynamics and ecosystem functioning, not only in relatively simple temperate systems, but also in structurally complex hyper-diverse tropical forests.
The proliferation of digital cameras co-located with eddy covariance instrumentation provides new opportunities to better understand the relationship between canopy phenology and the seasonality of ...canopy photosynthesis. In this paper we analyze the abilities and limitations of canopy color metrics measured by digital repeat photography to track seasonal canopy development and photosynthesis, determine phenological transition dates, and estimate intra-annual and interannual variability in canopy photosynthesis. We used 59 site-years of camera imagery and net ecosystem exchange measurements from 17 towers spanning three plant functional types (deciduous broadleaf forest, evergreen needleleaf forest, and grassland/crops) to derive color indices and estimate gross primary productivity (GPP). GPP was strongly correlated with greenness derived from camera imagery in all three plant functional types. Specifically, the beginning of the photosynthetic period in deciduous broadleaf forest and grassland/crops and the end of the photosynthetic period in grassland/crops were both correlated with changes in greenness; changes in redness were correlated with the end of the photosynthetic period in deciduous broadleaf forest. However, it was not possible to accurately identify the beginning or ending of the photosynthetic period using camera greenness in evergreen needleleaf forest. At deciduous broadleaf sites, anomalies in integrated greenness and total GPP were significantly correlated up to 60 days after the mean onset date for the start of spring. More generally, results from this work demonstrate that digital repeat photography can be used to quantify both the duration of the photosynthetically active period as well as total GPP in deciduous broadleaf forest and grassland/crops, but that new and different approaches are required before comparable results can be achieved in evergreen needleleaf forest.
Conspecific negative density-dependent establishment, in which local abundance negatively affects establishment of conspecific seedlings through host-specific enemies, can influence species diversity ...of plant communities, but the generality of this process is not well understood. We tested the strength of density dependence using the United States Forest Service's Forest Inventory and Analysis database containing 151 species from more than 200,000 forest plots spanning 4,000,000 square kilometers. We found that most species experienced conspecific negative density dependence (CNDD), but there was little effect of heterospecific density. Additionally, abundant species exhibited weaker CNDD than rarer species, and species-rich regions exhibited stronger CNDD than species-poor regions. Collectively, our results provide evidence that CNDD is a pervasive mechanism driving diversity across a gradient from boreal to subtropical forests.
Biodiversity along temperate forest succession Hilmers, Torben; Friess, Nicolas; Bässler, Claus ...
The Journal of applied ecology,
November 2018, Letnik:
55, Številka:
6
Journal Article
Recenzirano
Odprti dostop
1. The successional dynamics of forests—from canopy openings to regeneration, maturation, and decay—influence the amount and heterogeneity of resources available for forest-dwelling organisms. ...Conservation has largely focused only on selected stages of forest succession (e.g., late-seral stages). However, to develop comprehensive conservation strategies and to understand the impact of forest management on biodiversity, a quantitative understanding of how different trophic groups vary over the course of succession is needed. 2. We classified mixed mountain forests in Central Europe into nine successional stages using airborne LiDAR. We analysed α- and β-diversity of six trophic groups encompassing approximately 3,000 species from three kingdoms. We quantified the effect of successional stage on the number of species with and without controlling for species abundances and tested whether the data fit the more-individuals hypothesis or the habitat heterogeneity hypothesis. Furthermore, we analysed the similarity of assemblages along successional development. 3. The abundance of producers, first-order consumers, and saprotrophic species showed a U-shaped response to forest succession. The number of species of producer and consumer groups generally followed this U-shaped pattern. In contrast to our expectation, the number of saprotrophic species did not change along succession. When we controlled for the effect of abundance, the number of producer and saproxylic beetle species increased linearly with forest succession, whereas the U-shaped response of the number of consumer species persisted. The analysis of assemblages indicated a large contribution of succession-mediated β-diversity to regional γ-diversity. 4. Synthesis and applications. Depending on the species group, our data supported both the more-individuals hypothesis and the habitat heterogeneity hypothesis. Our results highlight the strong influence of forest succession on biodiversity and underline the importance of controlling for successional dynamics when assessing successional stages with highest diversity (early and late successional stages) are currently strongly underrepresented in the forests of Central Europe. We thus recommend that conservation strategies aim at a more balanced representation of all successional stages.
1. Disturbances are widespread and may affect community assembly, species composition, (functional) diversity and hence ecosystem processes. It remains still unclear to what extent ...disturbance-mediated species changes scale-up to changes in community functional properties, especially for species-rich tropical forests. 2. A large-scale field experiment was performed in which the dynamics of 15 000 stems >10 cm in diameter was monitored for 8 years in 44 one-ha forest plots. Twelve functional effect and response traits were measured for the most dominant tree species. The effects of different intensities of disturbance caused by logging and silvicultural treatments on the species and functional diversity of a Bolivian tropical forest community were evaluated, along with how these changes were driven by underlying demographic processes. 3. Disturbance treatments did not affect species diversity or functional diversity indices based on multiple traits related to primary productivity and decomposition rate. This result suggests that species richness is conserved, and trait variation is maintained, which can buffer the community against environmental change. 4. In contrast, disturbance intensity affected the average plant trait values in the community (the community-weighted mean) for seven of 12 traits evaluated. At high disturbance intensity, the community had a lower wood density of stem and branches, lower leaf toughness and dry matter content, but higher specific leaf area and leaf N- and P concentration, with the value of these traits changing on average 6% over the 8-year period. The functional spectrum of the community changed, therefore, from 'slow', conservative, shade-tolerant species towards 'fast', acquisitive, light-demanding species. These functional changes in mean trait values may enhance primary productivity and decomposition rate in the short term. 5. Temporal changes in community functional properties were mainly driven by recruitment, and little by mortality or survival. 6. Synthesis. Moderate levels of (logging) disturbance neither affected species diversity nor functional diversity per se in the 8-year period after logging. Disturbance did, however, change the functional community composition towards 'fast' species with more acquisitive traits, thus potentially fuelling primary productivity and nutrient and carbon cycling. In conclusion, tropical forest management may contribute to conserving functional biodiversity of trees while providing forest resources.
Forest commons and local enforcement Chhatre, Ashwini; Agrawal, Arun
Proceedings of the National Academy of Sciences - PNAS,
09/2008, Letnik:
105, Številka:
36
Journal Article
Recenzirano
Odprti dostop
This article examines the relationship between local enforcement and forests used as commons. It uses a unique multicountry dataset, created over the past 15 years by the International Forestry ...Resources and Institutions Research Program. Drawing on original enforcement and forest commons data from 9 countries, we find that higher levels of local enforcement have a strong and positive but complex relationship to the probability of forest regeneration. This relationship holds even when the influence of a number of other factors such as user group size, subsistence, and commercial importance of forests, size of forest, and collective action for forest improvement activities is taken into account. Although several of the above factors have a statistically significant relationship to changes in the condition of forest commons, differences in levels of local enforcement strongly moderate their link with forest commons outcomes. The research, using data from diverse political, social, and ecological contexts, shows both the importance of enforcement to forest commons and some of the limits of forest governance through commons arrangements.
Originally published in 2000, this title is a collection of engaging, nontechnical contributions of scholars, policymakers, and forestry officials providing broad reflections on the agency's past and ...future, contemporary perspectives about the use and stewardship of public lands, and insightful analyses about the science involved in the practice of scientific management. The authors offer challenging ideas for evaluating the performance of the U.S. Forest Service, reshaping its mission, enhancing its effectiveness, improving internal morale, and increasing public participation in the agency. It is a valuable resource for policymakers, professional foresters, and any student interested in Environmental Studies.
Trees, Truffles, and Beasts Maser, Chris; Claridge, Andrew W; Trappe, James M
2008, 20080201, 2008-02-01
eBook, Book
In today's world of specialization, people are attempting to protect the Earth's fragile state by swapping limousines for hybrids and pesticide-laced foods for organic produce. At other times, ...environmental awareness is translated into public relations gimmicks or trendy commodities. Moreover, simplistic policies, like single-species protection or planting ten trees for every tree cut down, are touted as bureaucratic or industrial panaceas.Because today's decisions are tomorrow's consequences, every small effort makes a difference, but a broader understanding of our environmental problems is necessary to the development of sustainable ecosystem policies. In Trees, Truffles, and Beasts, Chris Maser, Andrew W. Claridge, and James M. Trappe make a compelling case that we must first understand the complexity and interdependency of species and habitats from the microscopic level to the gigantic. Comparing forests in the Pacific Northwestern United States and Southeastern mainland of Australia, the authors show how easily observable speciesùtrees and mammalsùare part of a complicated infrastructure that includes fungi, lichens, and organisms invisible to the naked eye, such as microbes.Eminently readable, this important book shows that forests are far more complicated than most of us might think, which means simplistic policies will not save them. Understanding the biophysical intricacies of our life-support systems just might.
Tree species exceeding 70 m in height are rare globally. Giant gymnosperms are concentrated near the Pacific coast of the USA, while the tallest angiosperms are eucalypts (Eucalyptus spp.) in ...southern and eastern Australia. Giant eucalypts co-occur with rain-forest trees in eastern Australia, creating unique vegetation communities comprising fire-dependent trees above fire-intolerant rain-forest. However, giant eucalypts can also tower over shrubby understoreys (e.g. in Western Australia). The local abundance of giant eucalypts is controlled by interactions between fire activity and landscape setting. Giant eucalypts have features that increase flammability (e.g. oil-rich foliage and open crowns) relative to other rain-forest trees but it is debatable if these features are adaptations. Probable drivers of eucalypt gigantism are intense intra-specific competition following severe fires, and inter-specific competition among adult trees. However, we suggest that this was made possible by a general capacity of eucalypts for ‘hyper-emergence’. We argue that, because giant eucalypts occur in rain-forest climates and share traits with rain-forest pioneers, they should be regarded as long-lived rain-forest pioneers, albeit with a particular dependence on fire for regeneration. These unique ecosystems are of high conservation value, following substantial clearing and logging over 150 yr.
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