Severe Human Disturbance Research Articles

Molecular Genetic Evidence for an Intra‐Specific Differentiation in Bursera simaruba in a Subtropical Forest

Bursera simaruba is also known as Gumbo-limbo. Their seeds mature during the last half of the dry season and are dispersed by birds and mammals. Bursera sp. can be found growing in dry humid tropical and subtropical zones. Bursera is known for his adaptation capabilities, easy reproduction and cutting. The population of trees in a forest patch of the Guanica dry forest colonized the area during the last 35 years after undergoing severe human disturbance and abandonment. Previous research indicates that the colonization could have taken place through seed dispersal mechanisms. Nevertheless, the spatial distribution of the trees suggests that the tree colony may be the result of root sprouting or cloning. This study focuses on the question: is the tree colony of Bursera simaruba at the study site in the Guanica Dry Forest Reserve made up of ramets of a genet? The short-term study aim of this work was PCR optimization of Bursera DNA fragments for the treatment population. The methodology was based in the collection of six leaves from twelve different Bursera trees growing in the colonized dry forest area (treatment) and another area serving as a control population. The age of the trees in both populations were estimated by measuring their diameter at breast height (DBH). Then, DNA extraction of leaves of every tree was performed and finally PCR optimization of DNA fragments was done. The DNA bands were observed confirming the presence of DNA in the samples.

Influence of forest structure and composition on population density of the red slender loris Loris tardigradus tardigradus in Masmullah proposed forest reserve, Sri Lanka

Few studies address the influence of habitat disturbance on Sri Lanka's fauna, including the endemic red slender loris Loris tardigradus tardigradus. Masmullah Proposed Forest Reserve harbours one of few remaining red slender loris populations, and is considered a "biodiversity hotspot". Using plotless sampling, we sampled 387 trees to ascertain density, and to record traits influential to loris presence. The most common tree species was Humboldtia laurifolia, occurring at 676 trees/ha, with overall density at 1077 trees/ha. Twenty-seven families belonging to 40 species were recorded, of which 45% were endemic, 40% native, 7.5% introduced. Humboldtia laurifolia has a mutualistic relationship with ants, providing abundant food for lorises. Substrates available at 3.5 m (height preferred by lorises), were small (less than 5 cm2), the size preferred by lorises. Vines and branches provided continuous passage, and trees held a number of potential sleeping sites. The characteristics of the forest are ideal for lorises, but the abundance of this habitat as measured by basal area is small, typical of severe degradation associated with chronic human disturbance. Continued illegal deforestation will impact severely already fragmented loris populations.

Diversity, distinctiveness and conservation status of the Mediterranean coastal dung beetle assemblage in the Regional Natural Park of the Camargue (France)

Abstract.The Mediterranean region as a whole has the highest dung beetle species richness within Europe. Natural coastal habitats in this region are among those which have suffered severe human disturbance. We studied dung beetle diversity and distinctiveness within one of the most important coastal protected areas in the west Euro‐Mediterranean region (the regional Park of Camargue, southern France) and made comparisons of dung beetle assemblages with other nearby Mediterranean localities, as well as with other coastal protected area (Doñana National Park, Spain). Our finding showed that: (1) The species richness of coastal habitats in the Camargue is low and only grasslands showed a similar level of species richness and abundance to inland habitats of other Mediterranean localities. The unique habitats of the coastal area (beaches, dunes and marshes) are largely colonized by species widely distributed in the hinterland. (2) In spite of their low general distinctiveness, dune and marsh edges are characterized by the occurrence of two rare, vulnerable, specialized and large roller dung beetle species of the genus Scarabaeus. As with other Mediterranean localities, current findings suggest a recent decline of Scarabaeus populations and the general loss of coastal dung beetle communities in Camargue. (3) The comparison of dung beetle assemblages between the Camargue and Doñana shows that, in spite of the low local dung beetle species richness in the Camargue, the regional dung beetle diversity is similar between both protected areas. Unique historical and geographical factors can explain the convergence in regional diversity as well as the striking divergence in the composition of dung beetle assemblages between both territories.

Special Section: Effects of Mobile Fishing Gear on Marine Benthos

Conservation BiologyVolume 12, Issue 6 p. 1178-1179 Special Section: Effects of Mobile Fishing Gear on Marine Benthos Les Watling, Les Watling Darling Marine Center, University of Maine, Walpole, ME 04573, U.S.A., email [email protected]Search for more papers by this authorElliott A. Norse, Elliott A. Norse Marine Conservation Biology Institute, 15806 NE 47th Court, Redmond, WA 98052-5208, U.S.A., email [email protected]Search for more papers by this author Les Watling, Les Watling Darling Marine Center, University of Maine, Walpole, ME 04573, U.S.A., email [email protected]Search for more papers by this authorElliott A. Norse, Elliott A. Norse Marine Conservation Biology Institute, 15806 NE 47th Court, Redmond, WA 98052-5208, U.S.A., email [email protected]Search for more papers by this author First published: 09 October 2008 https://doi.org/10.1046/j.1523-1739.1998.0120061178.xCitations: 15Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume12, Issue6December 1998Pages 1178-1179 RelatedInformation

Changes in Vegetation Structure and Diversity After Grass-to-Forest Succession in a Southern Appalachian Watershed

To document how species richness and diversity (H′) recover from severe large-scale disturbance, we report temporal patterns of species composition and diversity following grass-to-forest succession from a long-term experiment in the Coweeta Basin, western North Carolina. The original experiment—clear-cutting, 5 yr of grass cover followed by a herbicide treatment, and abandonment in a Southern Appalachian mixed deciduous forest—represents the most severe human disturbance in the Coweeta Basin. For several years after cessation of management, Robinia pseudoacacia quickly sprouted from roots and exceeded the growth rates of other species. Liriodendron tulipifera increased in density and basal area because of its prolific seedling establishment and rapid growth rate. Regeneration of large seeded species was mixed—sparse for Quercus rubra and Q. coccinea and nonexistent for Q. prinus and Q. velutina. In the overstory, density-based H′ increased from 1958, before grass conversion, to 15 yr and 28 yr following disturbance. In contrast, basal area-based H′ had significantly declined at 15 yr, then increased at 28 yr. The initial decline in basal area-based H′ was attributed to a decline in evennness of species distribution (J′) rather than to a change in species richness. The severe disturbance increased the abundance of early successional woody species and of herbaceous genera that tolerate open habitats, such as Erichtites, Phytolacca, and Erigeron. Shade-tolerant understory ferns and herbs such as Polystichum acrostichoides, Dennstaedtia punctilobula, Galium latifolium and Viola cucullata gradually became more abundant. The 28-yr-old forest of WS6 had much lower species richness than the adjacent reference watersheds, but more than threefold higher density.

Experimental Studies on the Resiliency of Floating Typha Mats in a Freshwater Marsh

(1) This paper examines the phenology of Typha in floating mats, following drainage or seasonal burning or both, in marshes where water-level can be controlled, near the Bay of Fundy (New Brunswick, Canada). On both drained and flooded areas, four burning treatments (spring, summer, autumn and no burning) were superimposed in 1981. The fires were more intense than would occur naturally but we wished to establish resistance to change. (2) Drainage and subsequent burning in summer reduced the Typha standing crop, by the end of the vegetation period following the treatments, to 201% of that in the flooded, unburned treatment. (3) Typha survived the disturbance and no major shifts in species composition were observed. (4) The results suggest that the Typha floating mat is resilient and will recover quickly from the range of drying and burning regimes that could be imposed under the normal climatic conditions of the Bay of Fundy area. (5) It is hypothesized from the present short-term study that these flooded areas may move toward bog-like conditions in the absence of continued and severe human disturbance.

Numbers of nesting frigatebirds, Fregata minor and F. ariel, on Aldabra Atoll nature reserve, Seychelles

Aldabra Atoll, a strict Nature Reserve and major breeding station of lesser and greater frigatebirds, may be developed for tourism. Determining whether this affects the frigate breeding populations is complicated by their extended annual laying seasons and the biennial breeding periodicity of individuals rearing fledgelings. This study, using a census method incorporating adjustments for seasonal changes in nest numbers, changes in nest ownership and replacement laying, indicates that there are at least 4000 pairs of greater frigatebirds and 6000 pairs of lesser frigatebirds annually involved in breeding activities. There is some evidence that more male than female greater frigatebirds attempt to pair each season. Comparison with an earlier census suggests that severe human disturbance induces curtailment of laying seasons, major changes in nest distribution and prevents many birds from breeding.

Habitat gradient and reproductive habits of the sevenStellaria species in Japan

The author studied the habitat preference, life form, life cycle and reproductive characteristics of the seven species of the genusStellaria along a valley in the northeastern part of Kyoto City. Along the valley 150 quadrats were set from the village up to the hills. The quadrats were sorted into 15 quadrat groups by their affinity in the environment. The quadrat groups were ordinated by the quotients of community and the Bray-Curtis method in order to reveal the complex gradient in the environment. The complex gradient could be best understood by the degree of human disturbance. The seven species showed a continuous distribution along the complex gradient. There existed three patterns in their habitat preference and reproductive characteristics: (1)S. media andS. neglecta grew as annuals in the habitat of severe human disturbance. (2)S. tomentella, S. sessiliflora, andS. diversiflora grew as perennials in the habitat of slight human disturbance. (3)S. aquatica andS. alsine grew as facultative annuals either in the habitat of severe or slight human disturbance.