Floristic and structural changes related to opportunistic soil tilling and pasture planting in grassland communities of the Flooding Pampa

The Flooding Pampa natural grassland has an intricate pattern of plant communities, related to small topographic differences that determine important changes in soil characteristics. Despite limitations imposed by soil properties and periodic waterlogging, opportunistic tilling is carried out to plant pastures. There is little information on how pasture planting may affect the structure of the grassland communities. In order to document changes caused by cultural activities on structural and functional characteristics of plant communities in this landscape, we made field surveys in grasslands and very old pastures (grassland communities recovered through secondary succession) using transects located across existing topographic gradients. The patchy structure of this landscape was revealed by the multivariate analysis, by means of which four plant communities could be identified in the natural grassland. Species composition of these communities differed from that of the corresponding old pastures. They lost an important number of exclusive species, but also gained species: some new to the landscape and many already present in other environments. Pasture planting reduced the rate of species replacements along the gradient and produced changes in patchiness, but had no effect on the species–area curve at the landscape scale. Neither did we find differences in total number of species, average number of species/site and proportion of functional types. The new grassland created by opportunistic pasture planting has developed into a structural gradient in which important differences occurred in the lower waterlogged-prone stands, whereas the sites of the other communities experienced less structural changes.     

Biodiversity conservation in cocoa production landscapes: an overview

Cocoa agroforests that retain a floristically diverse and structurally complex shade canopy have the potential to harbour significant levels of biodiversity, yet few studies have documented the plant and animal species occurring within these systems or within landscapes dominated by cocoa production. In this special issue, we bring together nine studies from Latin America, Africa and Asia that document the contribution of cocoa agroforestry systems to biodiversity conservation, and explore how the design, management and location of these systems within the broader landscape influence their value as habitats, resources and biological corridors. Tree diversity within the cocoa production systems is variable, depending on management, cultural differences, location and farm history, among other factors. Animal diversity is typically highest in those cocoa agroforests that have high plant diversity, structurally complex canopies, and abundant surrounding forest cover. In general, both plant and animal diversity within cocoa agroforests is greater than those of other agricultural land uses, but lower than in the original forest habitat. There are several emerging threats to biodiversity conservation within cocoa production landscapes, including the loss of remaining forest cover, the simplification of cocoa shade canopies and the conversion of cocoa agroforestry systems to other agricultural land uses with lower biodiversity value. To counter these threats and conserve biodiversity over the long-term, land management should focus on conserving native forest habitat within cocoa production landscapes, maintaining or restoring floristically diverse and structurally complex shade canopies within cocoa agroforests, and retaining other types of on-farm tree cover to enhance landscape connectivity and habitat availability.     

Testing the utility of Nothofagus pumilio for dating a snow avalanche in Tierra del Fuego, Argentina

In the subalpine forest zone, snow avalanches are potentially stand-devastating disturbances. Historical data regarding past avalanches in Argentina are scarce, but sufficiently old trees can show signs of past avalanche episodes that can be accurately dated using dendrochronological methods. Tree-ring analysis has not yet been used for dating avalanches in Tierra del Fuego, even though these disturbances are important to the dynamics of these southern forests. In this study, we evaluated the quality of Nothofagus pumilio for dating the avalanche that took place in the Martial Valley in 1976. Tree-ring data, complemented with vegetation analysis, was used to study the avalanche path. The dendrochronological study consisted of the analysis of wood samples taken from living trees located on the boundary between the undisturbed forest and the avalanche path. The vegetation analysis compared the forest structure within the avalanche path with the unaffected nearby forest. Wood scars and the abrupt increase in tree growth confirmed the occurrence of an avalanche event in 1976 in the Martial Valley of Tierra del Fuego, Argentina. The vegetation structure within the avalanche path was considerably different than that of the undisturbed forest. We found an important relationship between sapling abundance within the avalanche path and their distance from the undisturbed forest and their altitudinal position. The dendrochronological dating obtained in this research confirmed that the techniques and methodology used for N. pumilio in this study can be successfully applied for dating other avalanches that lack historical information.     

Effects of local and landscape scale and cattle grazing intensity on Orthoptera assemblages of the Hungarian Great Plain

The aims of this study were to test the influence of grazing intensity, effects of local and landscape parameters, and regional effects on orthopteran assemblages. We made our investigations on extensively and intensively grazed cattle pastures in three regions of the Hungarian Great Plain. The regions differed in landscape complexity; one region was situated in a structurally simple landscape with large landscape units, one in a structurally complex landscape with marshy patches and trees in the grasslands and one in a landscape with intermediate structural complexity. In each region we had seven pairs of differently managed grasslands, which differed in grazing intensity. Grasshoppers were recorded once in July 2003 using sweepnet catches and visual and acoustic observations in two 95 m long transects at each site (84 transects in total). Botanical surveys and measurements of other local factors were also made for each transect. After samplings, we digitised the most important land-use types using aerial photographs to produce landscape scale parameters within 100 and 500 m circles around every site. Analysing the management, regional, landscape and local effects on species richness with linear mixed models, we showed only strong significant regional differences. Linear mixed models for Orthoptera abundance yielded significant regional effects and marginal management effects. However, after including local and landscape parameters in a separate model a marginal local effect was found instead of a management effect in addition to the significant regional effect. Logistic regression models of 15 species also revealed the importance of local factors, particularly the importance of grass height, which is highly dependent on grazing intensity. We conclude that management intensity has indirect effects on Orthoptera species richness and abundance. Landscape scale parameters are also important, at least for some species.     

Simulating the impacts of southern pine beetle and fire on the dynamics of xerophytic pine landscapes in the southern Appalachians

Question: Can fire be used to maintain Yellow pine (Pinus subgenus Diploxylon) stands disturbed by periodic outbreaks of southern pine beetle? Location: Southern Appalachian Mountains, USA. Methods: We used LANDIS to model vegetation disturbance and succession on four grids representative of xeric landscapes in the southern Appalachians. Forest dynamics of each landscape were simulated under three disturbance scenarios: southern pine beetle, fire, and southern pine beetle and fire, as well as a no disturbance scenario. We compared trends in the abundance of pine and hardwood functional types as well as individual species. Results: Yellow pine abundance and open woodland conditions were best maintained by a combination of fire and southern pine beetle disturbance on both low elevation sites as well as mid‐elevation ridges & peaks. On mid‐elevation SE‐W facing slopes, pine woodlands were best maintained by fire alone. Conclusions: Our simulations suggest that fire can help maintain open pine woodlands in stands affected by southern pine beetle outbreaks.     

Reinstatement of traditional mowing regimes counteracts population senescence in the rare perennial Primula vulgaris

Question: Traditional management of grassland verges or ditch banks included mowing as a way to provide additional harvesting of hay. Nowadays, such sites are often left unmanaged, as mowing verges is no longer profitable in modern agricultural systems. Are vulnerable plant species able to withstand competition with the surrounding vegetation and maintain viable populations under these circumstances? How do they respond to reinstatement of traditional mowing regimes? Location: Oedelem, northwestern Belgium. Methods: To investigate the effect of reinstatement of the rare perennial Primula vulgaris, demography and adult plant performance were monitored in a grassland verge between 1999 and 2003 under different mowing regimes. Year transitions between life stages were analysed with matrix population models. To disentangle the contributions of the deviations in different life stage transitions to the variation in overall population growth rate, life table response experiments were used. Results: Both management and year had a strong impact on demographic traits of P. vulgaris. If plots were left unmanaged, lower plant performance and declining population growth rates were observed. While population growth rates differed significantly between mowing regimes, mowing of plots only in July did not differ from mowing in July and October in terms of vegetative and reproductive output of adults. Mowing twice a year appeared to be most efficient in increasing population growth rate both by raising recruitment and growth of individuals into large reproductive adults. Conclusions: Large P. vulgaris populations show a good ability to recover from recent abandonment of traditional management regimes. By mowing twice a year, managers are able to target vital rates that are most influential: growth and flowering of adult individuals.     

Gastrocnemius medialis muscle architecture and physiological cross sectional area in adult males with Duchenne muscular dystrophy

Objectives:

To describe muscle size and architecture of the gastrocnemius medialis (GM) muscle in eleven adult males with Duchenne Muscular Dystrophy (DMD, age 24.5±5.4 years), and a control group of eleven males without DMD (CTRL, age 22.1±0.9 years).

Methods:

GM anatomical cross sectional area (ACSA), volume (VOL), physiological cross sectional area (PCSA), fascicle length (Lf) and pennation angle (θ) were assessed using B-Mode Ultrasonography. GM ACSA was measured at 25, 50 and 75% of muscle length (Lm), from which VOL was calculated. At 50% of Lm, sagittal plane images were analysed to determine GM Lf and θ. GM PCSA was calculated as VOL/Lf. The ratio of Lf and Lm was also calculated.

Results:

GM ACSA at 50% Lm, VOL and PCSA were smaller in DMD males compared to CTRL males by 36, 47 and 43%, respectively (P<0.01). There were no differences in Lf and θ. GM Lm was 29% shorter in DMD compared to CTRL. Lf/Lm was 29% longer in DMD (P<0.01).

Conclusions:

Unlike previous data in children with DMD, our results show significant atrophy in adult males with DMD, and no change in Lf or θ. The shorter Lm may have implications for joint flexibility.     

Tuning plant signaling and growth to survive salt

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Assessing California's bar-built estuaries using the California Rapid Assessment Method

Bar-built estuaries are generally found at the mouths of smaller watersheds with seasonal precipitation, episodic streamflow and seasonal swell dynamics. Low streamflows and constructive wave forces form a sand bar at the mouth isolating the stream from the ocean, creating a ponded lagoon, and inundating the surrounding marsh plain. Bar-built estuaries are wide spread in California comprising over 50 percent of California's more than 500 estuaries. By connecting terrestrial, freshwater, and marine realms bar-built estuaries are complex and dynamic providing great habitat and ecosystem services. California has suffered some of the highest losses of wetland habitats, and the wetland habitats of bar-built estuaries continue to be threatened by further development, pollution, and climate related changes including diminished streamflows and sea level rise. Given this loss and threat we developed a California Rapid Assessment Method (CRAM) to assess the condition of California's bar-built estuaries. CRAM uses visual indicators to accurately reflect current wetland condition with regards to buffer habitat, hydrology, physical complexity, plant diversity and structure, and landscape influences. Here we validate this method by comparing results of CRAM for bar-built estuaries to other accepted measures of wetland condition that we simultaneously collected with CRAM including vegetative surveys, water nutrient levels, and GIS landscape scale measures of stress for 32 sites throughout California. CRAM correlated well with each of these three independent methods of assessing condition. Notably, the Environmental Monitoring and Assessment Program (EMAP) number of natives metric significantly correlated with CRAM Index and all Attribute scores. The strong correlations of CRAM to nutrient levels is particularly important considering the documentation of the negative impact of nutrients on fish populations, the use of bar-built estuaries by juveniles of commercially important species, and the nursery role of bar-built estuaries for maintaining imperiled populations of species such as steelhead. GIS measured percent impervious, percent agriculture, and percent dams all correlated well with expected CRAM Attribute scores at appropriate watershed scales relative to the area of inference for each CRAM metric. Further, CRAM for bar-built estuaries works well throughout California's diversity of environmental conditions and regardless of geography, timing, or whether the bar was open or closed during the survey. We hope that the availability of CRAM combined with available data repositories will enable local, state, and federal decision makers to better manage, restore, and conserve valuable bar-built estuaries in the face of continual threats like development, drought, and sea level rise.     

Impacts of forest cover change on ecosystem services in high Andean mountains

Land conversion affects the delivery of ecosystem goods and services. In this study, we used a 50 years time series of land cover maps to assess the potential impacts of forest cover changes on ecosystem services. A multi-source data integration strategy was followed to reduce inconsistencies in land cover change detection that result from the comparison of historical aerial photographs and satellite images. Our forest cover change analysis highlighted a shift from net deforestation to net reforestation in the early 1990s, consistent with the forest transition theory. When taking the nature of forest cover changes into account, our data show that the areal increase of the forested area was not associated with an improvement in ecological conditions. The overall capacity of the landscape to deliver ecosystem services dropped steadily by 16% over the 50 years’ study period. Conversion of native forests to agricultural land was associated with the strongest decline in ecosystem services. Conversion of natural grasslands into pine plantations mostly led to negative and probably irreversible impacts on the delivery of ecosystem services. Conversion of degraded agricultural lands into pine plantations led to an improvement in ecological conditions. An effective spatial targeting of forestation programs has the potential to maximize the environmental benefits that forest plantations may offer while minimizing their environmental harm.