Mixed Broadleaf Research Articles

A Mammal Survey of the Lower Usuthu Basin, Swaziland

The Lower Usuthu River Basin is set in the lowveld of Swaziland. The predominant vegetation types are mixed broadleaf woodland in the western lowveld and Acacia savanna in the eastern lowveld. The mammalian fauna of the Lower Usuthu Basin has been poorly documented. The study set out to survey mammals of the Lower Usuthu Basin using appropriate sampling techniques. A total of 45 species of mammals were recorded, or presumed to occur, in the study area, of which 10 species are of special conservation status both within Swaziland and in the southern african region. On Swazi Nation Land, species diversity and population sizes of mammals, especially the antelopes, were very low. Large-scale reduction of habitat may affect the conservation status of many mammals in the Lower Usuthu Basin. UNISWA Research Journal of Agriculture, Science and Technology Vol. 4 (1) 2000: pp 55-61

Tuatara (Sphenodon punctatus) feeding ecology in the presence of kiore (Rattus exulans)

The diet of tuatara was investigated on kiore‐inhabited Lady Alice Island in the Hen and Chickens Group, northern New Zealand, between 1993 and 1994. Both dietary (targeted) and inedible (incidental) items were eaten by tuatara. Dietary items recorded were exclusively invertebrate in origin. Estimates of environmental availability of invertebrates and indicated that the prey consumed were strongly selected by size and by taxa. Beetles, insect larvae, arachnids and weta comprised the greatest proportion of total diet, appeared in the greatest number of stomachs and were taken in excess of their abundance. Most prey were >10 mm in length, despite an abundance of smaller prey in the environment. The risk of predation by tuatara was greatest for terrestrial invertebrates and least for arboreal species. The composition of diets by habitat was largely similar between mid‐successional kanuka (Kunzea ericoides) and late successional mixed broadleaf forest. The size distribution of prey eaten by tuatara in kanuka habitat during autumn, and the low number of tuatara yielding dietary samples, are discussed in terms of food competition with kiore. Overall, the foraging behaviour of tuatara was not obviously different on rodent‐free compared to kiore‐inhabited islands, either indicating that food competition is insufficient to influence diet, or that tuatara are unable to change their feeding behaviour under a higher degree of competitive pressure for prey items. Clear support for either hypothesis is lacking.

Effects of forest management and grazing on breeding bird communities in plantations of broadleaved and coniferous trees in western England

Management options in commercial forestry include choice of conifers or broadleaves, rotation length, stand size and grazing regime. Each factor potentially affects the conservation value of woodland for birds. Relationships between these factors and the structure and composition of breeding bird communities were examined in 69 stands distributed across a range of plantations composed of predominantly native broadleaved and non-native coniferous trees in the Forest of Dean, western England, in 1992 and 1993. Each stand was classified as one of three high forest types: broadleaved, coniferous or mixed broadleaves and conifers. Stand size had no effect on bird communities. Species richness and overall bird abundance increased with forest age when all forest types were combined. Within stands of similar ages, there were no consistent differences in species richness or overall bird abundance between the three forest types or between grazed and ungrazed stands. However, bird communities in mixed stands were intermediate in their overall species composition to those in broadleaved and coniferous stands. Regression and gradient analyses (CCA and PCA) revealed that major gradients in the species composition of the bird communities were associated with stand age and with tree species composition. The proportion of individuals contributed by hole-nesting species was higher in broadleaved than coniferous stands and increased with stand age. The proportion of individuals contributed by migrants was higher in especially the early years, but also in the late years of the rotation. The proportion of migrants was higher in ungrazed than in grazed stands and increased with openness of the canopy and development of low vegetation. The diversity of stands in terms of tree sizes and tree species was positively correlated with both number of bird species and overall bird abundance. The relevance of these findings is discussed in relation to the integration of bird conservation into coniferous forestry, focusing particularly on the value of broadleaved stands and the effects on bird communities of stand structure and grazing pressure.

Patterns of weight loss and nutrient release from decomposing leaf litter in an age series of eucalypt plantations

Decomposition of leaf litter in an age series (1–8 yr) of eucalypt plantations, raised after the clear-felling of natural mixed broad leaf forest, was studied using litter bags exposed in each plantation to examine the weight loss pattern and nutrient dynamics. Analysis of variance indicated significant differences in weight loss between age and time. The most rapid weight loss occurred in the 1 yr old plantation and decreased with plantation age. The decomposition rate was lower than in the surrounding natural mixed broad leaf forest and adjacent natural sal ( Shorea robusta) forest. The rates of decomposition were significantly correlated with initial nutrient concentrations. Of the nutrients studied potassium was released most rapidly.

Migration characteristics of microelements in process of landscape geochemistry in Mt. Namjagbarwa area

To provide scientific basis for appraising natural resources in Mt. Namjagbarwa area, the migration characteristics of geochemical microelements, such as Zn, V, Ti, Pb, Ni, Cu, Cr, Co, Be and Ba, in the landscape zones of alpine scrub and meadow, the mountainous dark coniferous forest, the mountainous mixed broadleaf and coniferous forest, the mountainous quasi-subtropical semi-evergreen broadleaf forest, the mountainous subtropical evergreen broadleaf forest, and the valley quasi-tropical monsoon rainforest have been described in the paper.

Population Density of Empoasca fabae (Homoptera: Cicadellidae) in Weedy Beans

The response of Empoasca fabae (Harris) to beans, Phaseolus vulgaris L., in four weed habitats, bean monocultures, beans with Brassica kaber (D.-C.), beans with weeds that were removed in early July, and unweeded beans, was examined by visual and D-Vac samples. Weeds in the unweeded treatment were mixed broadleaf and grassy weeds. Visual samples showed that leafhopper density per bean leaflet was highest in bean monocultures, lowest in unweeded beans, and intermediate in the remaining weed habitats. D-Vac samples showed no difference in leafhopper density per area among weed habitats. D-Vac samples included leafhoppers living on the associated weeds, whereas visual samples restricted population estimates to leafhoppers on bean plants. These results suggest that mixed broad leaf and grassy weeds did not affect total E. fabae population density per land area, but did affect the spatial distribution of E. fabae among weedy and cultivated host plants.

Observations of the chemical properties of dew on vegetation that affect the dry deposition of SO2

Experiments were conducted to examine the chemical properties of dew (and guttation) that affect the dry deposition of SO2 to prairie grasses of tall stature and mixed broadleaf plants of short stature. For 2–3 hours after sunrise, liquid samples were extracted directly from the upper of the plant canopies and from surrogate surfaces, concurrently with selected atmospheric observations. Chemical analyses showed that aqueous concentrations of S(IV), SO42‐, and several other ions in the leaf wetness were often high compared to values typically found in rain, while NH4+ was not very abundant. Guttation produced substantial amounts of liquid, which mainly contributed Cl− to the leaf wetness. The dry deposition of S(IV) to leaf wetness was not always apparently limited by aqueous oxidation by O3, especially when aerodynamic resistances limited the maximum potential deposition velocity to less than 0.5 cm/s at a height of 8 m. A more effective oxidant than atmospheric O3 or NO2 could have been present and could have lessened the inferred substantial contributions of particle deposition to leaf wetness SO42‐. Foliar uptake of NO3‐ and SO42‐ was significant after sunrise. The pH of the leaf wetness in the broadleaf vegetation seemed to have a lower limit of about 5.3, possibly because of neutralization by substances leached from leaves, while the pH of the grasses reached values as low as 4.5 when the amount of leaf wetness was small. The potassium ion concentration in leaf wetness appeared to be an effective marker for leaf leaching.

Tropical forest biomass and successional age class relationships to a vegetation index derived from landsat TM data

Forest stand structure and biomass data were collected using conventional forest inventory techniques in tropical, subtropical, and warm temperate forest biomes. The feasibility of detecting tropical forest successional age class and total biomass differences using Landsat-Thematic mapper (TM) data, was evaluated. The Normalized Difference Vegetation Index (NDVI) calculated from Landsat-TM data were not significantly correlated with forest regeneration age classes in the mountain terrain of the Luquillo Experimental Forest, Puerto Rico. The low sun angle and shadows cast on steep north and west facing slopes reduced spectral reflectance values recorded by TM at orbital altitude. The NDVI, calculated from low altitude aircraft scanner data, was significantly correlated with forest age classes. However, analysis of variance suggested that NDVI differences were not detectable for successional forests older than approximately 15–20 years. Also, biomass differences in young successional tropical forest were not detectable using the NDVI. The vegetation index does not appear to be a good predictor of stand structure variables (e.g., height, diameter of main stem) or total biomass in uneven age, mixed broadleaf forest. Good correlation between the vegetation index and low biomass in even age pine plantations were achieved for a warm temperate study site. The implications of the study for the use of NDVI for forest structure and biomass estimation are discussed.

Nitrogen dynamics of decomposing hardwood leaf litter in a central himalayan forest

The N dynamics in four decomposing broadleaf litter species of a mixed broadleaf forest in Central Himalaya was followed for a period of 578 days. The C:N ratio above which net immobilization and below which net mineralization took place, differed among species. Once the nitrogen release phase started, the release was in proportion to the weight loss.

Effects of Weeds on the Diversity and Abundance of Insects in Soybeans1

Sweep-net sampling and pitfall trapping were used to survey insects in weedy and weedfree soybean habitats. Weedy soybean habitats consisted of (1) grassy soybeans; (2) soybeans with broadleaf weeds; and (3) soybeans with broadleaf weeds and grasses. Insect species diversity was greater in weedy soybean habitats than in weed-free soybeans. Greatest diversity of species occurred in the mixed-weed soybean habitat. The most important phytophagous insect on soybeans in Indiana, the Mexican bean beetle. Epilachna varivestis Mulsant, was most abundant in weed-free soybeans. Predators were most abundant in weedy soybeans. Coleomegilla maculata (DeGeer) was most abundant in weedy soybean habitats, whereas Orius insidiosus (Say) and Nabis spp. were most abundant in soybean habitats with grasses and mixed weeds. In the pitfall trapping study, Harpalus spp. were more abundant in soybean habitats with grasses and mixed broadleaf and grass weeds

PREDICTION OF THE ENVIRONMENTAL IMPACT OF MINING AND METALLURGICAL PRODUCTION IN THE TAYGA ZONE (with reference to the copper-nickel complexes of Mochegorsk and Sudbury)

The environmental impact of smelter gases of the nickel-copper complexes of Sudbury, Ont., and Monchegorsk, in the Soviet Union's Kola Peninsula, is compared. Despite the larger volume of production and of emissions from the Sudbury smelters, exceeding those of Monchegorsk by one order of magnitude, a relatively smaller area around the Sudbury smelter is affected by pollutants. The greater vulnerability of the biotic environment around Monchegorsk is related to the fact that the Soviet smelter complex lies in the northern tayga, with smaller biomass and biological productivity, while the Sudbury complex is situated in a richer forest region of mixed broadleaf and needle species, corresponding to the southern tayga in the Soviet Union.

Pear, Cutworm Control, 1976

Abstract Five insecticides were evaluated for control of 2 species of cutworms in a block of mature Bartlett pear trees. Plots (a 600-sq ft area with a tree at each corner of the plot) were replicated twice in a randomized block design. A handgun operated at a pump pressure of 500 psi was used to apply the sprays (volume of 500 gal/acre) in an effort to penetrate the cover crop of mixed broadleaf weeds and grasses. Effectiveness was determined by counting live larvae and cadavers in four 1/4 m2 quadrats chosen at random. Pretreatment counts were made July 28 and Aug 2, 1976; posttreatment counts were made Aug 5 and 6. The spray was applied Aug 2. Control was based on the number of cadavers vs. the number of live larvae recovered.