Paleovegetation dynamics in an alternative stable states landscape in the montane Western Ghats, India

Peat deposits (>50 ka) in the montane Nilgiris (Western Ghats, India), have been central to the reconstruction of late Quaternary paleoclimate using paleovegetation changes in the forest-grassland vegetation mosaic that coexist here. However, it is well-known that short-term disturbances can also cause vegetation switches when multiple stable vegetation states exist. We studied paleovegetation changes within the alternative stable states framework using stable carbon isotopes (relative abundance of C3-C4 vegetation) on the cellulose fraction from two high-resolution radiocarbon-dated peat cores ~170 m apart in the Sandynallah valley: Core 1 closer to the hillslope (32,000 years old) and Core 2 from the centre of the valley (45,000 years old). Core 1 is located in an ecotone showing shola-sedgeland dynamics with vegetation switching at c.22 ka from shola (possibly due to fire) to a prolonged unstable state until 13 ka sustained by low waterlogging. Following a hiatus c.13 ka, sedgeland dominates, with a shift into shola at 3.75 ka driven by increasing aridity. Core 2 shows a stable sedgeland mixed C3-C4 composition responding to temperature, enriched in C3-vegetation in the last glacial with C4-dominance beginning c.18.5 ka, indicative of deglacial warming. The distinctive vegetation states at corresponding times in Cores 1 and 2 within the same valley, responding independently to disturbances and climate, respectively, is the first paleo-record from an alternative stable states landscape in the montane tropics. Thus, short-term disturbances and site attributes need to be accounted for before ascribing vegetation change to changing climate in such vegetation mosaics.

Populational Structure of Eugenia sp. in Paraban Semiarid of State, Brazil

The genus Eugenia presents one of the most important in Myrtaceae family, expressing a potential nutritional high and in drugs obtaining. The plants are resist and resist disease, their hardwood has been used to produce posts, stakes, poles, firewood and charcoal. The objective of this present work was to conduct a survey of the population structure of Eugenia sp. was conducted in caatinga area, located in the municipality of Caturité, PB. Were sampled Forty plots of 10x20 m, totaling a sample area of 8.000 m². All shrub-tree individuals were inventoried by the taking the ground level diameter (DNS), height and number of tillers. The vegetation structure was evaluated by basal area, absolute density, absolute frequency and aggregation index of the species. A total of 741 individuals of Eugenia sp. Distributed in four vegetation mosaics with a history of different uses, which were conventionally approached as: A I = Abandoned quarry area; A II = Bottom of the valley; A III = Conserved Area and A IV = Capoeira Area. Area I presented a total of 92 individuals sampled in the 10 experimental plots (DA = 460), where in this environment the species tended to cluster, Area II presented 124 individuals (DA = 620) and the McGuines index expressed that in this environment the species finds grouped. In Area III, 480 individuals were sampled with an absolute density of 2,400 ind. ha-1 grouped. The density of Eugenia sp. Was performed descriptive statistical analysis. It is different in vegetation mosaics due to the history of land use in the studied areas. The largest number of individuals of Eugenia sp. is concentrated in the conserved area showing aggregation pattern. In all areas of study, individuals have low stem diameter, expressing the importance of the species in the regeneration of disturbed areas. In the quarry area are the individuals with higher height.

Soils and open ecosystems

Boundaries between open and closed ecosystems often coincide with soil differences of greater or lesser degree. It has long been argued that these soil differences explain the striking differences in vegetation structure. But the nature of the vegetation itself feeds back on soil properties so that it is far from trivial to determine whether soil differences are a cause or consequence of the vegetation growing at a site. This chapter reviews soil physical and chemical characteristics and their potential to determine open and closed vegetation mosaics. The chapter also explores competitive exclusion of forest trees by grasses, herbs, and shrubs.

Answer to California Landscape Riddle Lies Underground

Scientists link vegetation mosaics in California to patterns of weathered bedrock.