Pseudoreplication in Tropical Forests and the Resulting Effects on Biodiversity Conservation

Tropical forest ecosystems are threatened by habitat conversion and other anthropogenic actions. Timber production forests can augment the conservation value of primary forest reserves, but studies of logging effects often yield contradictory findings and thus inhibit efforts to develop clear conservation strategies. We hypothesized that much of this variability reflects a common methodological flaw, simple pseudoreplication, that confounds logging effects with preexisting spatial variation. We reviewed recent studies of the effects of logging on biodiversity in tropical forests (n = 77) and found that 68% were definitively pseudoreplicated while only 7% were definitively free of pseudoreplication. The remaining proportion could not be clearly categorized. In addition, we collected compositional data on 7 taxa in 24 primary forest research plots and systematically analyzed subsets of these plots to calculate the probability that a pseudoreplicated comparison would incorrectly identify a treatment effect. Rates of false inference (i.e., the spurious detection of a treatment effect) were >0.5 for 2 taxa, 0.3–0.5 for 2 taxa, and <0.3 for 3 taxa. Our findings demonstrate that tropical conservation strategies are being informed by a body of literature that is rife with unwarranted inferences. Addressing pseudoreplication is essential for accurately assessing biodiversity in logged forests, identifying the relative merits of specific management practices and landscape configurations, and effectively balancing conservation with timber production in tropical forests. Pseudoreplicación en Bosques Tropicales y Efectos Resultantes Sobre la Conservación de Biodiversidad     

EROSION ON LOGGING ROADS IN REDWOOD CREEK,NORTHWESTERN CALIFORNIA1

Road-related erosion was estimated by measuring 100 randomly located plots on a 180 km road network in the middle reach of R'dwood Creek in northwestern California. The estimated erosion ratn of 177 m³ km^-1 was contrasted with two earlier studies in nearby parts of the same watershed. A sizable proportion of the great reduction in erosion from that reported in the earlier studies is attributed to changes in forest practice rules. Those changes have resulted in better placement and sizing of culverts and, especially, to less reliance on culverts to handle runoff from logging roads.     

浅谈测井事故的认识与处理

在测井过程中,由于各种不可预见的复杂原因,测井事故不可避免。文章分析了形成测井事故的影响因素,如井径、钻井液性能、全角变化率、操作过程、套管鞋等。一旦测井事故发生,根据卡电缆、卡仪器、断电缆的事故特点来判断事故类型,再根据各种处理方法的优缺点来处理事故;提出一些注意事项,使测井事故防患于未然。     

Effects of Reduced-Impact Logging on Fish Assemblages in Central Amazonia

Abstract: In Amazonia reduced‐impact logging, which is meant to reduce environmental disturbance by controlling stem‐fall directions and minimizing construction of access roads, has been applied to large areas containing thousands of streams. We investigated the effects of reduced‐impact logging on environmental variables and the composition of fish in forest streams in a commercial logging concession in central Amazonia, Amazonas State, Brazil. To evaluate short‐term effects, we sampled 11 streams before and after logging in one harvest area. We evaluated medium‐term effects by comparing streams in 11 harvest areas logged 1–8 years before the study with control streams in adjacent areas. Each sampling unit was a 50‐m stream section. The tetras Pyrrhulina brevis and Hemigrammus cf. pretoensis had higher abundances in plots logged ≥3 years before compared with plots logged <3 years before. The South American darter (Microcharacidium eleotrioides) was less abundant in logged plots than in control plots. In the short term, the overall fish composition did not differ two months before and immediately after reduced‐impact logging. Temperature and pH varied before and after logging, but those differences were compatible with normal seasonal variation. In the medium term, temperature and cover of logs were lower in logged plots. Differences in ordination scores on the basis of relative fish abundance between streams in control and logged areas changed with time since logging, mainly because some common species increased in abundance after logging. There was no evidence of species loss from the logging concession, but differences in log cover and ordination scores derived from relative abundance of fish species persisted even after 8 years. For Amazonian streams, reduced‐impact logging appears to be a viable alternative to clear‐cut practices, which severely affect aquatic communities. Nevertheless, detailed studies are necessary to evaluated subtle long‐term effects.     

Impacts of Alternative Timber Harvest Practices on Leaf-Chewing Herbivores of Oak

Abstract:  Studies of the effects of logging on Lepidoptera rarely address landscape-level effects or effects on larval, leaf-feeding stages. We examined the impacts of uneven-aged and even-aged logging on the abundance, richness, and community structure of leaf-chewing insects of white ( Quercus alba L.) and black ( Q. velutina L.) oak trees remaining in unharvested areas by sampling 3 years before and 7 years after harvest. After harvest, white oaks in uneven-aged sites had 32% fewer species of leaf-chewing insects than control sites. This reduction in species richness may have resulted from changes in microclimate (reducing plant quality and/or changing leaf phenology) that affected a much larger total area of each site than did even-aged cuts. For black oak after harvest, species richness in uneven- and even-aged sites increased relative to levels before harvest. Harvesting did not alter total insect density or community structure in the unlogged habitat for either oak species with one exception: insect density on black oak increased in the oldest forest block. Community structure of herbivores of black and white oaks in clearcut gaps differed from that of oaks in intact areas of even-aged sites. Furthermore, both richness and total insect density of black oaks were reduced in clearcut gaps. We suggest that low-level harvests alter herbivore species richness at the landscape level. Treatment effects were subtle because we sampled untreated areas of logged landscapes, only one harvest had occurred, and large temporal and spatial variation in abundance and richness existed. Although the effects of logging were greater in uneven-aged sites, the effects of even-aged management are likely to increase as harvesting continues.     

Salamander Abundance along Road Edges and within Abandoned Logging Roads in Appalachian Forests

Abstract:  Roads may be one of the most common disturbances in otherwise continuous forested habitat in the southern Appalachian Mountains. Despite their obvious presence on the landscape, there is limited data on the ecological effects along a road edge or the size of the "road-effect zone." We sampled salamanders at current and abandoned road sites within the Nantahala National Forest, North Carolina (U.S.A.) to determine the road-effect zone for an assemblage of woodland salamanders. Salamander abundance near the road was reduced significantly, and salamanders along the edges were predominantly large individuals. These results indicate that the road-effect zone for these salamanders extended 35 m on either side of the relatively narrow, low-use forest roads along which we sampled. Furthermore, salamander abundance was significantly lower on old, abandoned logging roads compared with the adjacent upslope sites. These results indicate that forest roads and abandoned logging roads have negative effects on forest-dependent species such as plethodontid salamanders. Our results may apply to other protected forests in the southern Appalachians and may exemplify a problem created by current and past land use activities in all forested regions, especially those related to road building for natural-resource extraction. Our results show that the effect of roads reached well beyond their boundary and that abandonment or the decommissioning of roads did not reverse detrimental ecological effects; rather, our results indicate that management decisions have significant repercussions for generations to come. Furthermore, the quantity of suitable forested habitat in the protected areas we studied was significantly reduced: between 28.6% and 36.9% of the area was affected by roads. Management and policy decisions must use current and historical data on land use to understand cumulative impacts on forest-dependent species and to fully protect biodiversity on national lands     

Nutrients in soil solution following selective logging of a humid tropical ‘terra firme’ forest north of Manaus,Brazil

Sustainable use of the Amazon forest for timber production is conditioned by the effect of logging on the system's nutrient cycling. This paper reports the results of a soil moisture and soil water chemistry monitoring campaign before and immediately after a selective logging which removed 35 m³ wood/ha. Soil moisture was measured using tensiometers, and soil water chemistry using suction samplers in five disturbance classes: tractor tracks, clearing centres, clearing edges, forest edges and untouched forest. The results show that the soil under the tractor tracks and clearings contained more moisture than under the untouched forest. The suction samplers extracted substantially more nitrate, ammonium, calcium, magnesium and potassium from the clearing centres, the tractor tracks and the clearing edges than from the forest sites. The results are explained in terms of altered microbial activity, changes in crown interception and uptake by roots.     

A Contemporary Assessment of Change in Humid Tropical Forests

Abstract: In recent decades the rate and geographic extent of land‐use and land‐cover change has increased throughout the world's humid tropical forests. The pan‐tropical geography of forest change is a challenge to assess, and improved estimates of the human footprint in the tropics are critical to understanding potential changes in biodiversity. We combined recently published and new satellite observations, along with images from Google Earth and a literature review, to estimate the contemporary global extent of deforestation, selective logging, and secondary regrowth in humid tropical forests. Roughly 1.4% of the biome was deforested between 2000 and 2005. As of 2005, about half of the humid tropical forest biome contained 50% or less tree cover. Although not directly comparable to deforestation, geographic estimates of selective logging indicate that at least 20% of the humid tropical forest biome was undergoing some level of timber harvesting between 2000 and 2005. Forest recovery estimates are even less certain, but a compilation of available reports suggests that at least 1.2% of the humid tropical forest biome was in some stage of long‐term secondary regrowth in 2000. Nearly 70% of the regrowth reports indicate forest regeneration in hilly, upland, and mountainous environments considered marginal for large‐scale agriculture and ranching. Our estimates of the human footprint are conservative because they do not resolve very small‐scale deforestation, low‐intensity logging, and unreported secondary regrowth, nor do they incorporate other impacts on tropical forest ecosystems, such as fire and hunting. Our results highlight the enormous geographic extent of forest change throughout the humid tropics and the considerable limitations of the science and technology available for such a synthesis.     

Bushmeat Supply and Consumption in a Tropical Logging Concession in Northern Congo

Abstract: Unsustainable hunting of wildlife for food empties tropical forests of many species critical to forest maintenance and livelihoods of forest people. Extractive industries, including logging, can accelerate exploitation of wildlife by opening forests to hunters and creating markets for bushmeat. We monitored human demographics, bushmeat supply in markets, and household bushmeat consumption in five logging towns in the northern Republic of Congo. Over 6 years we recorded 29,570 animals in town markets and collected 48,920 household meal records. Development of industrial logging operations led to a 69% increase in the population of logging towns and a 64% increase in bushmeat supply. The immigration of workers, jobseekers, and their families altered hunting patterns and was associated with increased use of wire snares and increased diversity in the species hunted and consumed. Immigrants hunted 72% of all bushmeat, which suggests the short‐term benefits of hunting accrue disproportionately to “outsiders” to the detriment of indigenous peoples who have prior, legitimate claims to wildlife resources. Our results suggest that the greatest threat of logging to biodiversity may be the permanent urbanization of frontier forests. Although enforcement of hunting laws and promotion of alternative sources of protein may help curb the pressure on wildlife, the best strategy for biodiversity conservation may be to keep saw mills and the towns that develop around them out of forests.