Response of a Reptile Guild to Forest Harvesting

Abstract:  Despite the growing concern over reptile population declines, the effects of modern industrial silviculture on reptiles have been understudied, particularly for diminutive and often overlooked species such as small-bodied snakes. We created 4 replicated forest-management landscapes to determine the response of small snakes to forest harvesting in the Coastal Plain of the southeastern United States. We divided the replicated landscapes into 4 treatments that represented a range of disturbed habitats: clearcut with coarse woody debris removed; clearcut with coarse woody debris retained; thinned pine stand; and control (unharvested second-growth planted pines). Canopy cover and ground litter were significantly reduced in clearcuts, intermediate in thinned forests, and highest in unharvested controls. Bare soil, maximum air temperatures, and understory vegetation all increased with increasing habitat disturbance. Concomitantly, we observed significantly reduced relative abundance of all 6 study species (scarletsnake [Cemophora coccinea] , ring-neck snake [Diadophis punctatus] , scarlet kingsnake [Lampropeltis triangulum] , red-bellied snake [Storeria occipitomaculata] , southeastern crowned snake [Tantilla coronata] , and smooth earthsnake [Virginia valeriae] ) in clearcuts compared with unharvested or thinned pine stands. In contrast, the greatest relative snake abundance occurred in thinned forest stands. Our results demonstrate that at least one form of forest harvesting is compatible with maintaining snake populations. Our results also highlight the importance of open-canopy structure and ground litter to small snakes in southeastern forests and the negative consequences of forest clearcutting for small snakes.     

Patch-Occupancy Modeling as a Method for Monitoring Changes in Forest Floristics: a Case Study in Southeastern Australia

Abstract:  The ability to monitor changes in biodiversity is fundamental to demonstrating sustainable management practices of natural resources. Disturbance studies generally focus on responses at the plot scale, whereas landscape-scale responses are directly relevant to the development of sustainable forest management. Modeling changes in occupancy is one way to monitor landscape-scale responses. We used understory vegetation data collected over 16 years from a long-term study site in southeastern Australia. The site was subject to timber harvesting and frequent prescribed burning. We used occupancy models to examine the impacts of these disturbances on the distribution of 50 species of plants during the study. Timber harvesting influenced the distribution of 9 species, but these effects of harvesting were generally lost within 14 years. Repeated prescribed fire affected 22 species, but the heterogeneity of the burns reduced the predicted negative effects. Twenty-two species decreased over time independent of treatment, and only 5 species increased over time. These changes probably represent a natural response to a wildfire that occurred in 1973, 13 years before the study began. Occupancy modeling is a useful and flexible technique for analyzing monitoring data and it may also be suitable for inclusion within an adaptive-management framework for forest management.     

ESTIMATING EROSION RISKS ASSOCIATED WITH LOGGING AND FOREST ROADS IN NORTHWESTERN CALIFORNIA1

ABSTRACT: Erosion resulting from logging and road building has long been a concern to forest managers and the general public. An objective methodology was developed to estimate erosion risk on forest roads and in harvest areas on private land in northwestern California. It was based on 260 plots sampled from the area harvested under 415 Timber Harvest Plans completed between November 1978 and October 1979. Results confirmed previous findings that most erosion related to forest management occurs on a small fraction of the managed area. Erosion features larger than the minimum size inventories in this study (> 13 yd³) occupied only 0.2 percent of the area investigated. Linear discriminant analysis was used to develop two equations for identifying critical sites (sites with erosion >100 yd³ac^?1). The equations were based on slope, horizontal curvature (an expression of local topography), and soil color (on road sites) or the strength of the underlying rocks (on harvest sites). The equations can be used in planning to estimate the erosion risk of proposed activities. They can also be used to estimate acceptable risk thresholds based on the value of competing resources.     

ASPEN CLEARCUTTING INCREASES SNOWMELT AND STORM FLOW PEAKS IN NORTH CENTRAL MINNESOTA1

ABSTRACT: Clearcutting aspen from the upland portion of an upland peatland watershed in north central Minnesota caused snowmelt peak discharge to increase 11 to 143 percent. Rainfall peak discharge size increased as much as 250 percent during the first two years after clearcutting, then decreased toward precutting levels in subsequent years. Storm flow volumes from rain during the first two years increased as much as 170 percent but declined to preharvest volumes in the third year. Snowmelt volumes did not significantly change. Snowmelt peak discharge occurred about four to five days earlier after clearcutting, but the timing of storm flow from rainfall was not changed. Snowmelt peaks remained above precut size for nine years after clearcutting on an area undergoing natural regeneration to aspen saplings. Partial cutting - up to approximately one-half of the watershed - reduced peak snowmelt discharge because melt was desynchronized in cleared and forested parts. Clearing more than 2/3 of the watershed caused snowmelt flood peak size to double during years with snow packs in excess of seven inches of water that remained until a day when maximum air temperatures exceeded 60d?F.     

Local vulnerability as an advantage: mangrove forest management in Pará state,north Brazil,under conditions of illegality

When ecosystems are threatened or scientific knowledge of the effects of human action is uncertain, legislative prohibition is often adopted. This paper examines how the criminalization of mangrove tree use affects ecosystem management outcomes. We explore the biological, economic and social sustainability effects of the legal ban on mangrove use on the coast of Bragança, Pará, north Brazil. There are two main categories of mangrove users in this area: firstly, local subsistence users who also derive some financial incomes from mangrove sale. Their mangrove use is intertwined with household livelihood strategies and they display self-initiated planning and action towards sustainable management; secondly, more mobile, purely commercial users who are responsible for most commercial mangrove exploitation and who employ regionally sequential, predatory resource exploitation strategies. These users are typically based at some distance from the exploited areas and share neither local livelihood strategies nor sustainability agendas. The current outright ban on any utilization of mangrove flora seems to undermine biological sustainability, is economically inefficient and generates normative insecurity, conflict and social polarization. The ineffectiveness of the outright legal prohibition of mangrove tree use in terms of sustainable coastal management leads us to investigate alternative management options. We suggest that the legalization of local mangrove utilization and the strengthening of local users rights and responsibilities to control outsiders in a co-management framework, as proposed in the Brazilian extractive reserves (RESEX) approach, is most likely to advance ecologically, economically and socially sustainable mangrove management. It is demonstrated that a legal recognition of local entitlements to mangrove trees would reduce social vulnerability and therefore move forest management outcomes into more desirable directions.

1954年,1991年长江流域洪涝对比

1991年6、7月间长江流域遭受了特大洪涝灾害,范围之大、程度之深、损失之惨重,为解放以来所罕见。本文就雨涝特征、洪涝成因和经济影响三个方面与1954年洪涝作一对比。     

不同土地利用分布格局下的岩溶泉水化学变化研究

利用多参数自动记录仪CTDP300对具有不同土地利用分布格局的贵州普定陈旗和灯盏河两个岩溶泉域的降雨量、泉水位、水温、pH值和电导率进行了一个完整水文年的连续监测,并依据化学平衡热力学原理进行计算,得到连续的水的CO2分压(PCO2)和方解石饱和指数(SIc)。结果表明这两个泉的这些水化学指标均呈现出明显的季节变化和暴雨动态变化。然而,两泉水的这些变化具有明显的差异:对于土壤分布较多和水田分布在排泄区的陈旗泉而言,HCO3-和PCO2较高,而pH和SIc值明显低于土壤分布较少且水田分布于补给区的灯盏河泉,且变幅较小。此外在暴雨后,陈旗泉pH升高、PCO2降低,而灯盏河泉pH降低、PCO2升高。这些反映了不同土地利用分布格局对岩溶水化学调节作用的差异。灯盏河泉Ca2+、SO2-4、Mg2+和EC较高主要是其流域中石膏和白云岩含量较多的缘故。这些发现说明,pH、电导率、HCO3-、Ca2+、SO42-、Mg2+、PCO2和SIc等岩溶水化学参数可以作为不同土地利用分布格局和环境变化的重要指标。     

Effects of Scale and Logging on Landscape Structure in a Forest Mosaic

Landscape structure in a forest mosaic changes with spatial scale (i.e. spatial extent) and thresholds may occur where structure changes markedly. Forest management alters landscapestructure and may affect the intensity and location of thresholds. Our purpose was to examine landscape structure at different scales to determine thresholds where landscape structure changes markedly in managed forest mosaics of the Appalachian Mountains in the eastern United States. We also investigated how logging influences landscape structure and whether these management activities change threshold values. Using threshold and autocorrelation analyses, we found that thresholds in landscape indices exist at 400, 500, and 800 m intervals from the outer edge of management units in our studyregion. For landscape indices that consider all landcovercategories, such as dominance and contagion, landscape structureand thresholds did not change after logging occurred. Measurements for these overall landscape indices were stronglyinfluenced by midsuccessional deciduous forest, the most commonlandcover category in the landscape. When restricting analysesfor mean patch size and percent cover to individual forest types,thresholds for early-successional forests changed after logging. However, logging changed the landscape structure at small spatialscale, but did not alter the structure of the entire forestmosaic. Previous forest management may already have increasedthe heterogeneity of the landscape beyond the point whereadditional small cuts alter the overall structure of the forest. Because measurements for landscape indices yield very differentresults at different spatial scales, it is important first toidentify thresholds in order to determine the appropriate scalesfor landscape ecological studies. We found that threshold andautocorrelation analyses were simple but powerful tools for thedetection of appropriate scales in the managed forest mosaicunder study.