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1.
This paper quantifies two important native forest ecosystem services in southern Chile: water supply and recreational fishing opportunities. We analyzed streamflow in relation to forest cover in six watersheds located in the Valdivian Coastal Range (39°50′–40°05′S), the effect of forest management on streamflow in two watersheds in the Valdivian Andes (600–650 m of elevation; 39°37′S), and fish abundance as a function of forest cover in 17 watersheds located in the Coastal Range and the Central Depression (39°50′–42°30′S). We found that the annual direct runoff coefficient (quickflow/precipitation) and total streamflow/precipitation in the dry summer season were positively correlated with native forest cover in the watershed (R2 = 0.67 and 0.76; *P = 0.045 and 0.027, respectively) during four years of observations. Conversely, a negative correlation was found between summer runoff coefficients (total streamflow/precipitation) and cover of Eucalyptus spp. and Pinusradiata plantations (R2 = 0.84; *P = 0.010). We estimated a mean increase of 14.1% in total summer streamflow for every 10% increase in native forest cover in the watershed. The analysis of streamflow changes between two paired watersheds dominated by native secondary Nothofagus stands, one thinned with 35% of basal area removal and a control, showed that the former had a 40% increase during summer (four years of observations). The best correlation between fish abundance and forest cover was found between trout abundance (%) and secondary native forest area in 1000 m × 60 m stream buffers (R2 = 0.65, ***P < 0.0001). We estimated a 14.6% increase in trout abundance for every 10% increase of native forest cover in these buffers. Similar approaches to quantify forest ecosystem services could be used elsewhere and provide useful information for policy and decision-making regarding forest conservation and management.  相似文献   

2.
We compared the understory communities (herbs, shrubs, and tree seedlings and saplings) of old-growth and second-growth eastern hemlock forests (Tsuga canadensis) in western Massachusetts, USA. Second-growth hemlock forests originated following clear-cut logging in the late 1800s and were 108–136 years old at the time of sampling. Old-growth hemlock forests contained total ground cover of herbaceous and shrub species that was approximately 4 times greater than in second-growth forests (4.02 ± 0.41%/m2 versus 1.06 ± 0.47%/m2) and supported greater overall species richness and diversity. In addition, seedling and sapling densities were greater in old-growth stands compared to second-growth stands and the composition of these layers was positively correlated with overstory species composition (Mantel tests, r > 0.26, P < 0.05) highlighting the strong positive neighborhood effects in these systems. Ordination of study site understory species composition identified a strong gradient in community composition from second-growth to old-growth stands. Vector overlays of environmental and forest structural variables indicated that these gradients were related to differences in overstory tree density, nitrogen availability, and coarse woody debris characteristics among hemlock stands. These relationships suggest that differences in resource availability (e.g., light, moisture, and nutrients) and microhabitat heterogeneity between old-growth and second-growth stands were likely driving these compositional patterns. Interestingly, several common forest understory plants, including Aralia nudicaulis, Dryopteris intermedia, and Viburnum alnifolium, were significant indicator species for old-growth hemlock stands, highlighting the lasting legacy of past land use on the reestablishment and growth of these common species within second-growth areas. The return of old-growth understory conditions to these second-growth areas will largely be dependent on disturbance and self-thinning mediated changes in overstory structure, resource availability, and microhabitat heterogeneity.  相似文献   

3.
Water temperature has profound effects on stream ecosystems. We studied effects of clear-fell logging Pinus radiata plantations on mid-summer water temperatures and recovery times in streams with 2–12 m wide channels. Post-logging increases were 2–3.8 °C for summer daily means and 4–7.3 °C for summer daily maxima. Rates of recovery of thermal regimes after logging were strongly negatively correlated with stream size, as indexed by catchment area, channel width or baseflow (r2 = 0.80–0.93). Summer daily mean and maximum temperatures declined during the riparian vegetation regrowth phase by 0.18 and 0.47 °C year−1, respectively, for the largest stream and 1.4 and 1.9 °C year−1 in the smallest stream. Thermal regimes were restored in small streams (2–4 m wide channels) about 6–8 years after clearfelling. In medium-sized streams (6–12 m wide channels), we predict this recovery will take 12–16 years.  相似文献   

4.
The introduction of non-native pathogens can have profound effects on forest ecosystems resulting in loss of species, changes in species composition, and altered fuel structure. The introduction of Phytophthora ramorum, the pathogen recognized as causing Sudden Oak Death (SOD), leads to rapid decline and mortality of tanoak (Lithocarpus densiflorus) in forests of coastal California, USA. We tracked foliar moisture content (FMC) of uninfected tanoaks, SOD-infected tanoaks, SOD-killed (dead) tanoaks, and surface litter for 12 months. We found that FMC values differed significantly among the three categories of infection. FMC of uninfected tanoaks averaged 82.3% for the year whereas FMC of infected tanoaks had a lower average of 77.8% (ANOVA, P = 0.04). Dead trees had a significantly lower FMC, averaging 12.3% (ANOVA, P < 0.01) for the year. During fire season (June–September), dead tanoak FMC reached a low of 5.8%, with no significant difference between dead canopy fuels and surface litter (ANOVA, P = 0.44). Application of low FMC values to a crown ignition model results in extremely high canopy base height values to escape crown ignition. Remote estimation of dead FMC using 10-h timelag fuel moisture shows a strong correlation between remote automated weather station (RAWS) 10-h timelag fuel moisture data and the FMC of dead leaves (R2 = 0.78, P < 0.01). Results from this study will help refine the decision support tools for fire managers in SOD-affected areas as well as conditions in other forests where diseases and insect epidemics have altered forest canopy fuels.  相似文献   

5.
Hemlock woolly adelgid (Adelges tsugae Annand) threatens native hemlock (Tsuga canadensis and T. caroliniana) in the eastern United States. Imidacloprid used as a soil-applied systemic insecticide is effective against A. tsugae in natural forests and in landscapes. Non-target impacts are a special concern because hemlock is ecologically important; often growing next to streams which contain aquatic species that are sensitive to imidacloprid, some of which are protected or endangered fauna. Environmental risk can be mitigated by determining the minimum effective dosage in forests. Adelgid populations responded to imidacloprid dosage with approximately a linear relationship between the percent population reduction (probability scale) vs. log of dosage; 50% reduction in populations could be achieved with 0.15 g per 2.5 cm of trunk diameter at breast height (dbh), or 10% of the maximum labeled dosage. However, effectiveness was found to vary based on dbh; the dosage predicted to give ∼90% reductions in adelgid populations is given by the equation log(dosage) = 0.0153 × dbh − 1.074, where the dosage is g imidacloprid per 2.5 cm of trunk dbh, and dbh is measured as cm. For trees less than 82 cm dbh, these dosages are less than the typical 1.5 g imidacloprid per 2.5 cm dbh currently used. Formulation into tablets rather than as a wettable powder reduced the maximum imidacloprid concentration in soil solution at 5 cm depth from 80 to 1.6 ppm in columns constructed with the organic soil found beneath forest hemlocks. A combination of optimum dosing of trees and adoption of the tablet formulation when treating trees in sensitive habitats should minimize the risk of contaminating aquatic resources with imidacloprid.  相似文献   

6.
Great Smoky Mountains National Park is using systemic imidacloprid to treat eastern hemlocks (Tsuga canadensis [L.] Carr.) infested with the exotic insect, hemlock woolly adelgid (Adelges tsugae Annand). This study investigated effects of these treatments on insectivorous birds and hemlock canopy arthropod assemblages in the context of food availability for insectivorous birds. Six pairs of treated and untreated hemlock sites were studied in 2007. Territories of three hemlock-associated Neotropical migratory foliage-gleaning bird species were mapped in these six sites, and relationships between bird territory density and hemlock foliar density were examined. Canopy arthropods were sampled by clipping mid-canopy hemlock branches in each paired site. Arthropods were identified to order or suborder and categorized into bird prey guilds and non-target herbivorous insect guilds. Despite being treated within the previous two years, there were no differences in hemlock woolly adelgid infestation between treated and untreated sites. This may reflect recovery or because the imidacloprid is slow-acting. Bird densities also did not differ between treated and untreated sites but were positively related to branch foliage mass, implying a preference in these birds for well-foliated hemlocks. A total of 10,219 hemlock woolly adelgids, and a total of 906 other arthropods from 16 orders were collected. There were no differences in species richness, abundance, or species composition between treated and untreated sites for total arthropods, or for immature arthropods ≥ 3 mm. In contrast, non-target herbivorous Hemiptera and larval Lepidoptera were significantly reduced in treated hemlocks. Although larval Lepidoptera are primary prey for insectivorous foliage-gleaning birds, the similarity in bird densities between treated and untreated sites suggests the birds are able to find other food resources in the mixed hemlock-deciduous stands where the study sites were located. Therefore, controlling hemlock woolly adelgid-induced defoliation through use of imidacloprid may have short-term benefits for hemlock-associated birds. While imidacloprid treatments did not appear to be currently affecting most arthropods, primary prey guilds should be monitored for long-term declines that could impact hemlock-associated birds.  相似文献   

7.
The use of shelterwoods to favour the development of natural or underplanted seedlings is common in temperate forests but rare in the pine forests of the Mediterranean area. Our aim was to assess the use of shelterwoods in Aleppo pine (Pinus halepensis) woodlands in southern France to promote the survival and growth of two co-occurring oak species: the deciduous Quercus pubescens and the evergreen Quercus ilex.Twelve Aleppo pine stands were selected and differentially thinned to create a light shelterwood (basal area = 10 m2/ha, irradiance 52%), a medium shelterwood (basal area = 19 m2/ha, irradiance 33%) and a dense shelterwood (basal area = 32 m2/ha, irradiance 13%). A total of 1248 sowing points, half composed of Q. pubescens and half of Q. ilex, were then set up in these three conditions. Seedling survival and growth were monitored for 3 years. Plant stress was assessed by measuring predawn leaf potential and photosynthetic performance through the Fv/Fm ratio. Soil moisture was also recorded at two depths during two growing seasons.Survival was high for both species in all three conditions due to three consecutive wet years. The lowest survival was recorded for Q. pubescens in the dense shelterwoods. Growth in diameter and height increased from the dense to the light shelterwoods. Shrubs developed more strongly in the light shelterwood, and increasing shrub cover enhanced height growth. Photosynthetic performance was lowest for Q. pubescens in dense shelterwoods and highest in light shelterwoods, whereas the reverse was true for Q. ilex. The lowest predawn potentials were recorded in the dense shelterwoods even though higher soil water content values were measured in this treatment during the summer drought.We show that light shelterwoods were more beneficial to growth than denser ones, indicating control mainly by light availability during the 3 years of the study. However, as lower soil moisture at 30-50 cm depth and faster understorey development were also recorded in this condition, more extended observation is needed to determine whether this benefit persists in subsequent years.  相似文献   

8.
Wood is an important component of forested stream ecosystems, and stream restoration efforts often incorporate large wood. In most cases, however, stream restoration projects are implemented without information regarding the amount of wood that historically occurred or the natural rates of wood recruitment. This study uses a space-for-time analysis to quantify large wood loading to 28 streams in the northeastern US with a range of in-stream and riparian forest characteristics. We document the current volume and frequency of occurrence of large wood in streams with riparian forests varying in their stage of stand development as well as stream size and gradient. Linear models relating stream wood characteristics to stream geomorphic and forest characteristics were compared using Akaike's Information Criterion (AIC) model selection. The AIC analysis indicated that the volume and frequency of large wood and wood accumulations (wood jams) in streams was most closely associated with the age of the dominant canopy trees in the riparian forest (best models: log10(large wood volume (m3 100 m−1)) = (0.0036 × stand age) − 0.2281, p < 0.001, r2 = 0.80; and large wood frequency (number per 100 m) = (0.1326 × stand age) + 7.3952, p < 001, r2 = 0.63). Bankfull width was an important factor accounting for wood volume per unit area (m3 ha−1) but not the volume of wood per length of stream (100 m−1). The empirical models developed in this study were unsuccessful in predicting wood loading in other regions, most likely due to difference in forest characteristics and the legacy of forest disturbance. However, these models may be applicable in other streams in the northeastern US or in streams with comparable riparian forests, underlying geology, and disturbance regimes—factors that could alter long-term wood loading dynamics. Our results highlight the importance of understanding region-specific processes when planning stream restoration and stream management projects.  相似文献   

9.
The purpose of this study was to compare carbon sequestration between moso bamboo (Phyllostachys heterocycla) and China fir (Cunninghamia lanceolata) forests. The study site was located in the lower mountain area of central Taiwan, where both moso bamboo and China fir were rich. In addition, moso bamboo and China fir forests were surveyed on 12 and 19 plantations, respectively. We predicted carbon sequestration based on the allometric model for moso bamboo and China fir forests and compared the relationships between characteristics of bamboo forests and elevation. The results showed that mean diameter at breast height (DBH), culms per hectare and aboveground biomass were not clearly affected by elevation, whereas a negative correlation (R = −0.600, p = 0.039) between mean DBH and stand density was found for moso bamboo forests. Moreover, the aboveground carbon storage was higher for China fir forests than for moso bamboo (99.5 vs. 40.6 Mg ha−1). However, moso bamboo is an uneven-aged stand which is only composed of 1-5-year-old culms, while China fir is an even-aged stand and the age range is from 15 to 54 years, such that, per year, the mean aboveground carbon sequestration is 8.13 ± 2.15 and 3.35 ± 2.02 Mg ha−1 for moso bamboo and China fir, respectively. On the other hand, the mean carbon sequestration of China fir decreases with increasing the age class. Furthermore, the ratio of moso bamboo to China fir is 2.39 and a T-test showed that the aboveground carbon levels were significantly different between these two species; thus, moso bamboo is a species with high potential for carbon sequestration.  相似文献   

10.
We addressed the efficacy of stream-side buffers in ameliorating the effects of clearcut timber harvest on Cascade torrent salamanders (Rhyacotriton cascadae), coastal/Cope's giant salamanders (Dicamptodon tenebrosus/D. copei), coastal tailed frogs (Ascaphus truei), and water temperature regimes in the Cascade Range in southern Washington. Forty-one streams in 4 categories were sampled; streams in clearcuts with and without buffers, streams in 35+ year old second-growth forest, and streams in unharvested forest (150+ years old). Tailed frog and Cascade torrent salamander densities were 2–7-fold lower (P < 0.05), respectively, in streams in managed forests than in streams in unharvested forest. In addition, both these species were less abundant (P < 0.05) in unbuffered streams than streams with buffers or in second-growth forest. In contrast, giant salamander densities were 5–50% greater (P > 0.05) in managed streams than unharvested, being greatest in unbuffered and second-growth streams. We used the differences in density estimates of unbuffered streams and unharvested streams to define an ecologically important effect size for each species and then compared the mean effect size and 95% confidence intervals of contrasts between managed stream categories to assess buffer effectiveness. Buffers had a positive ecologically important effect on the density of torrent salamanders and tailed frogs, but had an ecologically negative effect on giant salamanders. Water temperatures were similar among stream categories. However, Cascade torrent salamanders were nearly absent from streams where temperatures were ≥14 °C for ≥35 consecutive hours. Issues that need further study include effective buffer width and longitudinal extent, and confirmation of the water temperature threshold we identified.  相似文献   

11.
Allometric equations have been developed for various different vegetation types but have rarely been validated in the field and never for dry tropical forest such as caatinga. In three areas of semi-arid Brazil, with regenerating caatinga vegetation, we measured and weighed twelve hundred individuals of four tree species and used the data to validate equations previously determined in mature caatinga. They and several other equations developed for tropical vegetations overestimate the biomass (B) of trees from the regeneration areas by more than 20%, possibly because these trees have reduced crowns, with lower branch masses. We then determined new allometric equations for them, validating equations for one site against data of the others and pooling the data if they were cross-validated. The best equations were power ones, based on diameter at breast height (D), with little improvement by including height, crown area and/or wood density (Caesalpinia pyramidalis, B = 0.3129D1.8838; Croton sonderianus, B = 0.4171D1.5601; Mimosa ophthalmocentra, B = 0.4369D1.8493; and Mimosa tenuiflora, B = 0.3344D1.9648 and 0.4138D1.7718).  相似文献   

12.
Greenhouse gas emissions from managed peatlands are annually reported to the UNFCCC. For the estimation of greenhouse gas (GHG) balances on a country-wide basis, it is necessary to know how soil–atmosphere fluxes are associated with variables that are available for spatial upscaling. We measured momentary soil–atmosphere CO2 (heterotrophic and total soil respiration), CH4 and N2O fluxes at 68 forestry-drained peatland sites in Finland over two growing seasons. We estimated annual CO2 effluxes for the sites using site-specific temperature regressions and simulations in half-hourly time steps. Annual CH4 and N2O fluxes were interpolated from the measurements. We then tested how well climate and site variables derived from forest inventory results and weather statistics could be used to explain between-site variation in the annual fluxes. The estimated annual CO2 effluxes ranged from 1165 to 4437 g m−2 year−1 (total soil respiration) and from 534 to 2455 g m−2 year−1 (heterotrophic soil respiration). Means of 95% confidence intervals were ±12% of total and ±22% of heterotrophic soil respiration. Estimated annual CO2 efflux was strongly correlated with soil respiration at the reference temperature (10 °C) and with summer mean air temperature. Temperature sensitivity had little effect on the estimated annual fluxes. Models with tree stand stem volume, site type and summer mean air temperature as independent variables explained 56% of total and 57% of heterotrophic annual CO2 effluxes. Adding summer mean water table depth to the models raised the explanatory power to 66% and 64% respectively. Most of the sites were small CH4 sinks and N2O sources. The interpolated annual CH4 flux (range: −0.97 to 12.50 g m−2 year−1) was best explained by summer mean water table depth (r2 = 64%) and rather weakly by tree stand stem volume (r2 = 22%) and mire vegetation cover (r2 = 15%). N2O flux (range: −0.03 to 0.92 g m−2 year−1) was best explained by peat CN ratio (r2 = 35%). Site type explained 13% of annual N2O flux. We suggest that water table depth should be measured in national land-use inventories for improving the estimation of country-level GHG fluxes for peatlands.  相似文献   

13.
Wang QX  Li SF  Zhao F  Dai HQ  Bao L  Ding R  Gao H  Zhang LX  Wen HA  Liu HW 《Fitoterapia》2011,82(5):777-781
A new oxysporidinone analogue (1) and a new 3-hydroxyl-2-piperidinone derivative (2), along with the known compounds (−)-4,6′-anhydrooxysporidinone (3), (+)-fusarinolic acid (4), gibepyrone D (5), beauvercin (6),cerevisterol (7), fusaruside (8), and (2S,2′R,3R,3′E,4E,8E)-1-O-D-glucopyranosyl-2-N-(2′-hydroxy-3′-octadecenoyl)-3-hydroxy-9-methyl-4,8-sphingadienine (9) were isolated from Fusarium oxysporum. Compounds 1-9 were evaluated for cytotoxicity using the MTT method against cancer cell lines, PC-3, PANC-1, and A549. Beauvericin showed cytotoxicity against PC-3, PANC-1, and A549 with IC50 value of 49.5 ± 3.8, 47.2 ± 2.9, and 10.4 ± 1.6 μM, respectively. Beauvericin also exhibited anti-bacterial activity towards methicillin-resistant Staphylococcus aureus (MIC = 3.125 μg/mL) and Bacillus subtilis (MIC = 3.125 μg/mL).  相似文献   

14.
The loss of natural forest habitats due to forestry is the main reason for the decline in boreal forest biodiversity of the Nordic countries of Europe. Ecological rehabilitation may provide means to recover and sustain biodiversity. We analyzed the effects of controlled burning and dead-wood creation (DWC) on the diversity of pioneer wood-inhabiting fungi in managed Norway spruce (Picea abies) forests in southern Finland. Altogether 18 stands were first subjected to a partial cutting with ordinary logging residues in form of cut stumps and treetops left on site. The subsequent rehabilitation treatments consisted of a controlled burning applied in half of the stands and three levels of dead-wood creation (5, 30 and 60 m3 ha−1). The DWC involved creation of logs; felling of whole trees to mimic downed logs formed by natural disturbance processes. Each treatment was replicated three times. Inside each stand, substrates were sampled in two different biotopes; one on mineral soil and one on mineral soil with a thin peat layer. We surveyed the fungal flora on the logs (n = 364) and the ordinary residue stumps (n = 1767) and tops (n = 845) five years after the treatments.When comparing different stands, controlled burning had a significant effect on species composition; certain species were significantly more frequent on substrates in burned stands than in unburned stands, indicating that these species were favored by controlled burning. By contrast, we found no significant effects of DWC levels or biotope on species composition or richness. When comparing different substrates, 99% of the logs hosted at least one species and the occurrence probability of certain species was significantly higher on logs than on ordinary residue stumps and tops. Yet, volume-based rarefaction analyses showed that residues were more species dense than the logs, indicating that ordinary logging residues constitute important resources for many pioneer species.We conclude that controlled burning combined with DWC have strong effects on biodiversity; it modifies the composition of the pioneer wood-inhabiting fungal species found in managed forests and may thereby also influence the further succession and diversity of the secondary fungal flora.  相似文献   

15.
Scolytids have been studied more than any other group of forest insects, but most investigations have been restricted to only a few pest species. This bias hampers our understanding of variation in abundance and pest status. Even the simple question whether the abundance of scolytids can predicted by the same independent variables as their pest status is still a matter of debate. To explore this issue, we estimated their abundance using non-attracting flight-interception traps set in a wide range of forests across Czech Republic, Germany, and France. Pest status was taken from current literature. As independent variables, we considered host range, host abundance, and several traits of the considered species in linear models using generalized least squares with a correlation structure derived from the phylogenetic tree of the beetles. Host range was calculated as the root phylogenetic diversity index. The variation in the abundance across scolytids was well explained by resource-related parameters (R2 = 0.53). In contrast to abundance, the pest status was significantly related to species-specific traits, such as body size and maximum number of generations. However, the explained variance was much lower (R2 = 0.19). Although our analysis showed that abundance and pest score follow different patterns, we stress the importance of monitoring all species using non-selective traps. Considering the increasing global trade and the rapidly changing climate, such a broad ecological monitoring is necessary to detect new interactions and/or invading species that may influence our forests ecosystems.  相似文献   

16.
Although the removal or addition of understory vegetation has been an important forest management practice in forest plantations, the effects of this management practice on soil respiration are unclear. The overall objective of this study was to measure and model soil respiration and its components in a mixed forest plantation with native species in south China and to assess the effects of understory species management on soil respiration and on the contribution of root respiration (Rr) to total soil respiration (Rs). An experiment was conducted in a plantation containing a mixture of 30 native tree species and in which understory plants had been removed or replaced by Cassia alata Linn. The four treatments were the control (Control), C. alata addition (CA), understory removal (UR) and understory removal with C. alata addition (UR + CA). Trenched subplots were used to quantify Rr by comparing Rs outside the 1-m2 trenched subplots (plants and roots present) and inside the trenched subplots (plants and roots absent) in each treatment. Annual soil respiration were modeled using the values measured for Rs, soil temperature and soil moisture. Our results indicate that understory removal reduced Rs rate and soil moisture but increased soil temperature. Regression models revealed that soil temperature was the main factor and soil moisture was secondary. Understory manipulations and trenching increased the temperature sensitivity of Rs. Annual Rs for the Control, CA, UR and UR + CA treatments averaged 594, 718, 557 and 608 g C m−2 yr−1, respectively. UR decreased annual Rs by 6%, but CA increased Rs by about 21%. Our results also indicate that management of understory species increased the contribution of Rr to Rs.  相似文献   

17.
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   

18.
Impacts of forestry have been described in many studies, with a strong focus on changes in run-off water quality. Biological responses to forest drainage and the efficiency of commonly used water protection methods remain largely unknown, however. We used a six-year replicated before-after-control-impact (BACI) field experiment to assess the effects of forest drainage improvement works (ditch cleaning; digging of supplementary ditches) on water chemistry, sedimentation, brown trout egg mortality and macroinvertebrate community composition in six headwater streams in Northern Finland. Standard water protection methods (ditch break combined with sedimentation pit) were used to reduce fine sediment (<1.0 mm) loading into the streams. Six artificial spawning sites were constructed in each stream, three downstream (treatments) and three upstream (controls) of the drainage areas. Sediment loading did not increase after forest drainage, and no changes were detected in water quality. Brown trout egg mortality rate increased after drainage works, but more so in the upstream controls than downstream treatment sections, and only in smaller (watershed <6.25 km2) streams. All macroinvertebrate metrics (e.g. total macroinvertebrate diversity and density) decreased significantly through time. However, these responses were observed in both control and treatment sections, and could not have been caused by the drainage works directly but were rather related to inter-annual variability in precipitation and discharges. Our results thus highlight the importance of placing results from local monitoring studies in a regional context.  相似文献   

19.
High densities of bell miners (Manorina melanophrys) are known to accelerate dieback in eucalypt forests presumably through their negative impact on other avian insectivores and predatory insects. Some areas of moist eucalypt forest that are managed for sustained timber production also support very high densities of bell miners. In this study, we quantified the relative population density of bell miners in forests, and investigated the relationship between bell miner population density, the relative population density of other birds and species richness. A study site of 900 ha was selected in Olney State Forest on the Central Coast of New South Wales (33°7′ S, 150°22′ E), an area that has been managed for timber production since the 1920s. Monthly census counts were carried out over a 16-month period to include diurnal and seasonal variation. Bell miner population density ranged from 14–38 birds/ha and was found to be negatively correlated with diversity of other species. A linear empirical relationship was found between bird species richness (y) and bell miner relative population density (x) by the equation y = −0.12x + 7.78 (R = 0.9638, n = 8, P < 0.0001), and an increase in bell miner abundance was found to decrease the abundance of other species as given by the equation y = −0.32x + 16.83 (R = −0.9646, n = 8, P < 0.0001).  相似文献   

20.
We examined the short-term effects of group-selection harvesting with seed-tree retention on ground-dwelling and bark-dwelling arthropod communities in a northern hardwood forest in the Upper Peninsula of Michigan. Arthropods were sampled in 16 group-selection openings and 8 closed canopy reference plots. Two opening sizes were examined—radii of 0.5 (320 ± 27 m2, n = 8) and 1.0 (1217 ± 62 m2, n = 8) times the mean canopy height (22 m). Each opening and reference plot was centered on a single Betula alleghaniensis Britt. (yellow birch). Ground-dwelling arthropods were sampled using pitfall traps that were opened for two 1-week periods (rounds 1 and 2), and bark-dwelling arthropods were sampled with sticky traps attached to the centrally located B. alleghaniensis trees. Family-level diversity of ground-dwelling arthropods was lower in reference plots than in the openings, but the only significant difference occurred during round 2, between the matrix and large openings (P < 0.01). During both sampling periods, the ground-dwelling community exhibited a distinct clustering of family-level composition along environmental gradients such as opening size. Families such as Staphylinidae (rove beetles) and Trombidiidae (red velvet mites) were not favored by higher canopy openness while families such as Acrididae (grasshoppers) and Lycosidae (wolf spiders) were captured more in openings than in the forest matrix. Landing rates of wood-boring insects such as Buprestidae (metallic wood-boring beetles) and Xiphydriidae (wood wasps) were significantly higher on seed trees in group-selection openings than in reference plots (P < 0.05). Our results suggest that integrating group-selection openings within northern hardwood forests can lead to an increase in the family-level diversity of ground-dwelling arthropods, at least in the short term. Furthermore, seed trees left in such openings may be more attractive to bark- and wood-boring insects, which warrants further investigation into the susceptibility of these seed trees to damage by certain insect pests.  相似文献   

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