Are lianas increasing in importance in temperate floodplain forests in the southeastern United States?   总被引：1，自引：0，他引：1  

Bruce P. Allen  Rebecca R. Sharitz  P. Charles Goebel 《Forest Ecology and Management》2007

Floodplain forests of the southeastern United States are species rich, often with a dense and diverse liana community. Long-term trends in the density and distribution of lianas may indicate shifts in the composition of plant functional types in these forests. Liana communities in non-fragmented forests in Panama and across the Neotropics have increased in size and density over the last two decades of the 20th century. Are similar changes occurring in temperate forests? Evidence from long-term studies of liana communities in two floodplain forests in South Carolina support the findings from tropical forests. In second-growth forests of the Savannah River system, data from five 1-ha plots established in 1979 and monitored for 22 years indicate a steady increase in liana size and density. Likewise, in old-growth floodplain forests of the Congaree National Park, liana density has increased over 12 years in six 1-ha plots after Hurricane Hugo disturbed the forests in 1989. The increase in liana density and size in these floodplain forests of the southeastern United States is of sufficient magnitude to suggest that lianas are likely influencing stand dynamics in these forests. Consequently, we argue that lianas should be included in models of temperate bottomland forest development of the southeastern United States.  相似文献   

Monitoring forest dynamics using satellite imagery—a case study in the natural reserve of Changbai Mountain in China     

Qi-Jing Liu  Xuan-Ran Li  Ze-Qing Ma  Nobuo Takeuchi 《Forest Ecology and Management》2005,210(1-3):25-37

This study intended (1) to develop a quantitative method to describe vegetation succession or change by remote sensing approach, and (2) to test the capability in clarifying the stability or instability of natural forests in landscape scales. With special attention on the coniferous forest, the attempt was conducted on the natural reserve of Changbai mountain in northeast China by using multi-temporal TM images. Two simple parameters were derived to represent succession rate or change extent. One was the mean change of radiance, and another was the number of pixels with changed reflection property. As conclusion, TM imagery is effective for detecting vegetation changes. The results also demonstrated that the so called climax is not a pure stand, which is generally assumed to be exclusively dominated by climax species, but rather a complex of shifting mosaic. The pioneer patches are permanent units in the forest community. This method is considered applicable for assessing the developing status or behavior of plant communities in large scales, like a life zone, under disturbance of global warming, especially for long-time span.  相似文献   

Spatial dispersion of trees in an old-growth temperate hardwood forest over 60 years of succession     

Preston R. Aldrich  George R. Parker  Jeffrey S. Ward  Charles H. Michler 《Forest Ecology and Management》2003,180(1-3):475-491

An analysis of spatial dispersion was conducted for individual tree species in the old-growth forest at the Davis-Purdue Research Forest in Indiana. This 20.6 ha stand has been left largely undisturbed by exogenous factors since its acquisition by Purdue in 1917. It is the only long-term study plot of its size for a temperate hardwood forest with x–y coordinates (rectangular plot) for all species above 10 cm diameter. Full censuses have been conducted spanning 60 years (1926, 1976 and 1986).

Ripley’s L(t) function revealed that most species are characterized by some form of aggregation, agreeing with a prior evaluation from 1981. Heterogeneity of spatial structure was evident between two large plots, indicating that differences in site quality and history had influenced spatial structure. Shade-intolerant species were numerically dominant and spatially aggregated in 1926 but have declined over the 60-year interval and become more random in spatial dispersion. Shade-tolerant species have increased in number and become more aggregated over time, or they exhibit little change in spatial structure. Examples of the latter include Acer saccharum and Ulmus americana, species that experienced explosive population growth. These contrasting patterns are masked by stand-level patterns that show a trend toward uniformity over the same time frame.

These data reveal that changes in dispersion accompany the demographic failure experienced by numerous tree species in Central Hardwood old-growth stands, and these changes may feed back into a negative population cycle and further impede regeneration. The simultaneous manipulation of dispersion and density should be considered as a tool for influencing forest succession and promoting regeneration of desired tree species.  相似文献   

Winter litter disturbance facilitates the spread of the nonnative invasive grass Microstegium vimineum (Trin.) A. Camus     

Christopher M. Oswalt  Sonja N. Oswalt 《Forest Ecology and Management》2007

We investigated the impacts of winter litter disturbance on the spread of the nonnative invasive plant Microstegium vimineum (Trin.) A. Camus through experimental removals. We hypothesized that light penetration through the litter layer facilitates the spread of M. vimineum in forested systems. Our objective, therefore, was to quantify M. vimineum spread following litter removal. Linear spread and cover expansion from established M. vimineum patches was documented for one growing season under intact, undisturbed hardwood canopies within plots receiving one of two treatments. Treatments included litter removal (hereafter “removal”) and no litter removal (hereafter “undisturbed”). After one growing season, plots receiving the removal treatment experienced a spread of M. vimineum 4.5 times greater than plots receiving the undisturbed treatment (P < 0.0001; 1.66, and 0.37 m expansion, respectively). Cover expansion (measured as percent cover in 0.5 m² blocks at 0.5, 1, 1.5, and 2 m from established M. vimineum) averaged 16, 4, 0, and 0%, respectively, for the undisturbed treatment and 87, 64, 31, and 9%, respectively, for the removal treatment. Differences existed in cover expansion between treatments at the 0.5, 1, and 1.5 m distances (P < 0.0001, P < 0.001, and P = 0.01, respectively). Our results suggest that winter litter removal as a result of harvest activities, floodwater scour, or animal activities can drastically increase M. vimineum spread and may enhance potential ecological impacts of invasions by increasing M. vimineum percent cover. Previous studies have shown that M. vimineum responds to canopy removal with dramatic increases in biomass. This study suggests one mechanism facilitating rapid expansion of M. vimineum following site disturbance, and indicates that M. vimineum can experience rapid growth in response to site disturbance even in the absence of canopy removal.  相似文献   

Dynamics of sapling population in savanna woodlands of Burkina Faso subjected to grazing,early fire and selective tree cutting for a decade     

Didier Zida  Louis Sawadogo  Mulualem Tigabu  Daniel Tiveau  Per Christer Odén 《Forest Ecology and Management》2007

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Spatiotemporal Availability of Dead Wood in Protected Old-growth Forests: A Case Study from Boreal Forests in Eastern Finland     

《Scandinavian Journal of Forest Research》2012,27(4):317-329

Spatiotemporal patterns of standing and fallen dead trees were examined in two protected Scots pine ( Pinus sylvestris L.)-Norway spruce ( Picea abies (L.) Karst.) forests in eastern Finland (Pahkavaara and Pönttövaara). In Pahkavaara the volume of standing dead trees was 10 m 3 ha -1 and the volume of fallen logs was 66 m 3 ha -1 , and in Pönttövaara the values were 48 m 3 ha -1 and 107 m 3 ha -1 , respectively. The areas differed with respect to the tree species composition, whereas the proportion of different decay stages was similar. Decay stage and dendrochronological analyses revealed the continuity of dead wood formation. The spatial pattern of standing dead trees was usually towards clustered. The volumes of fallen logs showed a spatial autocorrelation up to distances of 10-20 m. The results also suggest that the current amount and diversity of dead wood is rather high, but that forest succession is likely to lead to a less diverse state in the future.  相似文献   

Comparing landscape scale vegetation dynamics following recent disturbance in climatically similar sites in California and the Mediterranean basin     

Carmel  Yohay  Flather  Curtis H. 《Landscape Ecology》2004,19(6):573-590

A long line of inquiry on the notion of ecological convergence has compared ecosystem structure and function between areas that are evolutionarily unrelated but under the same climate regime. Much of this literature has focused on quantifying the degree to which animal morphology or plant physiognomy is alike between disjunct areas. An important property of ecosystems is their behavior following disturbance. Yet, this aspect of ecosystems has not been investigated in a comparative study of convergence. If different ecosystems are under similar environmental controls, then one would predict that the rates and patterns of response to disturbance would also be similar. The objective of this study is to compare landscape dynamics following disturbance using spatiotemporal models to quantify vegetation change in Mediterranean ecosystems found in California and Israel. We model the process of tree and shrub regeneration at the landscape scale in two similar study sites in Israel (Mount Meron) and California (Hasting Nature Reserve). During the periods studied (1964-1992 for Israel and 1971-1995 for California), average annual change in tree cover was 5 times larger in Israel than in California. Based on multiple regression models, differences were found in the relative importance of specific variables predicting vegetation change. In Hastings (California), initial tree cover accounted for most of the explained variability in 1995 tree cover (partial R² = 0.71), while in Meron (Israel), grazing type and intensity, topography indices, and initial vegetation each accounted for about a third of the explained variability. These findings support the notion that traits such as regeneration pattern and rate, both at the individual level and at the landscape level, were largely affected by the human land use history of the region.  相似文献   

Species Dynamics in Disturbed Landscapes: When does a Shifting Habitat Mosaic Enhance Connectivity?     

Michael C. Wimberly 《Landscape Ecology》2006,21(1):35-46

Although landscape ecology emphasizes the effects of spatial pattern on ecological processes, most neutral models of species–habitat relationships have treated habitat as a static constraint. Do the working hypotheses derived from these models extend to real landscapes where disturbances create a shifting mosaic? A spatial landscape simulator incorporating vegetation dynamics and a metapopulation model was used to compare species in static and dynamic landscapes with identical habitat amounts and spatial patterns. The main drivers of vegetation dynamics were stand-replacing disturbances, followed by gradual change from early-successional to old-growth habitats. Species dynamics were based on a simple occupancy model, with dispersal simulated as a random walk. As the proportion of available habitat (p) decreased from 1.0, species occupancy generally declined more rapidly and reached extinction at higher habitat levels in dynamic than in static landscapes. However, habitat occupancy was sometimes actually higher in dynamic landscapes than in static landscapes with similar habitat amounts and patterns. This effect was most pronounced at intermediate amounts of habitat (p = 0.3?0.6) for mobile species that had high colonization rates, but were unable to cross non-habitat patches. Differences between static and dynamic landscapes were contingent upon the initial metapopulation size and the shapes of disturbances and the resulting habitat patterns. Overall, the results demonstrate that dispersal-limited species exhibit more pronounced critical behavior in dynamic landscapes than is predicted by simple neutral models based on static landscapes. Thus, caution should be exercised in extending generalizations derived from static landscape models to disturbance-driven landscape mosaics.  相似文献   

Behavior as a tool for assessing a managed landscape: a case study of the Karner blue butterfly     

Bradley A. Pickens  Karen V. Root 《Landscape Ecology》2009,24(2):243-251

In an increasingly human-dominated landscape, effective management of disturbance-maintained ecosystems, such as grasslands and savannas, is critical to the conservation of biodiversity. Yet, the response of individual organisms to landscapes created by disturbances and management is rarely studied. In this study, we examined the endangered Karner blue butterfly, Lycaeides melissa samuelis, in a heterogeneous oak savanna. Our objective was to quantify the butterfly’s habitat use and behavior to assess the effects of prescribed burning. The oak savanna management in Ohio, USA divides each Karner blue site (n = 4) into three units. Each one-third unit is then burned, mowed, or unmanaged in an annual rotation within each site, and the result is a fire return interval of ~3 years. Our surveys measured habitat use, while behavior observations quantified reproduction and foraging for the two annual broods. Our habitat use results showed burned treatments were recolonized quickly, but there was not a clear selection for burned treatments. Foraging rates were similar in all treatments; however, females oviposited significantly less in unmanaged treatments (only 5 of 127 ovipositions). This oviposition preference was likely due to habitat degradation and the availability of recently burned, early successional habitat. Since Karner blues avoided reproduction in units unburned for ≥4 years, these units could be burned to create high quality early successional habitat. These results demonstrate how behavioral decisions can be pivotal forces driving spatial population dynamics. Our case study demonstrates how a fine-scale landscape perspective combined with measurements of behavioral processes can assist with management decision-making.  相似文献   

亚热带多优势种森林群落演替现状评判研究   总被引：12，自引：0，他引：12  

张家城  陈力 《林业科学》2000,36(2):116-121

亚热带多优势种常绿阔叶林演替过程,依第１优势种的耐荫,喜湿特性,可划分为６个阶段;（１）针叶林阶段;（２）以针叶树为主的针阔混交林阶段;（３）以阳生性阔叶树为主的针阔混交林阶段;（４）以阳生性树种为主的绿阔叶林,当中生性树种在成为第１优势树种表明演替已进入顶极阶段,此后,又以优势树种人布格局为依据,将顶极阶段分为第５、第６阶段;（５）未发衣完善的顶极阶段;（６）发育完善的顶极阶段。据此,判定本文所  相似文献