The lack of cost-effective, reliable sampling methods for many wetland characteristics hinders efforts to describe the structural and functional properties of wetlands. This study evaluated techniques for sampling the subsurface hydrology and invertebrates of freshwater wetlands. The depth of rusting on mild steel rods was compared with water well measurements to determine the reliability of rust depth as a predictor of subsurface water levels. An emergence trap and a benthic coring device were compared to determine the utility of each for sampling the invertebrate fauna of a wetland. Accuracy of the rods in estimating different water table measurements (average, lowest, most recent) and comparability of rod data (within sets of five rods) were investigated for different reference points on the rods, residence times, and wetland soils. The effect of the presence of vegetation in a soil low in organic matter on rod accuracy also was evaluated. The depth of lowest formation of a rust band on the rods predicted average and most recent water table depths in peat soil (r² for regressions of rust band depth on water table depth ranged from 0.71-0.95). Estimates of average water table depths were most precise for peat soil. Accuracy and precision were considerably lower in sand and clay soils, but significant relationships (P < 0.10) between depth of rust band formation and water table depth were found for all soils (r² values for sand and clay ranged from 0.13-0.55). The presence of vegetation had no effect on rod accuracy in the sand soil. Differences in rod performance between residence times were not apparent. However, a rod residence time of 4-6 weeks is recommended to balance the time necessary for adequate rust formation on the rods and to minimize the chance of exposure to large changes in water levels. A decrease in water table depth of approximately 40 cm in one month in the clay wetland caused a month lag time in rust formation. Differences in depth of rust band formation between the five rods within replicate sets were greatest for rods from clay (mean SD = ±7.9 cm). Variability of rust band measurements within replicate sets was lower in peat (mean SD = ±2.3 cm) and sand (mean SD = ±2.6 cm). The results indicated that the rusty rod technique has serious limitations and should be applied only in situations where the use of standard methods must be restricted. Emergence traps and a benthic coring device were used to sample the invertebrates of a freshwater, emergent wetland during late spring and summer, 1989. The fauna captured by each technique, disparities between the techniques in sampling certain taxa, and factors potentially affecting abundance estimates were examined. In addition, the efficiency of each technique, expressed as the number of samples required to achieve a desired level of precision, in estimating mean abundances of the dominant invertebrate group, the Chironomidae, was evaluated. Total and monthly estimates of insect family richness were higher for continuous sampling of emergence than for monthly core samples of the benthos. Emergence traps also caught a greater variety of the insect taxa inhabiting the wetland. The precision and efficiency of each technique in estimating abundances of the dominant group, the Chironomidae, varied between months and habitats (open water; vegetation). The variation was most likely due to the natural spatial and temporal variations inherent in invertebrate populations. The number of samples required (n[subscript r]) to estimate mean Chironomidae abundances for the entire summer, June-September, to a precision of D= 0.20 (equivalent to a standard error equal to 20% of the mean), varied between techniques. Fewer sampling stations would have been required to estimate mean adult abundances using emergence traps than would have been required for estimates of larval abundances using benthic core samples. Large numbers of benthic cores (27-208 individual cores per habitat) would have generally been required for both monthly and seasonal estimates of non-insect invertebrate abundances. Labor costs for processing emergence samples were about 30% of those for benthic samples. Subsampling of dominant groups in the emergence samples would have further reduced costs. Frequent sampling throughout a season, with several different techniques, is required to completely characterize the invertebrate community of a wetland. This study compared two quantitative techniques for sampling wetland insects. Continuous sampling with emergence traps provided higher estimates of insect family richness and more precise estimates of Chironomidae abundances at a lower cost per sample than monthly core samples of the benthos. / Graduation date: 1992

[Truncated abstract] Removal of native vegetation to facilitate traditional agriculture practices has been shown to reduce ecosystem health, and restricts the native habitat. The subsequent change in the predominant vegetation water use patterns has altered the catchment water balance, and hydrology which results in land degradation through such processes of salinisation and water logging. More recently, moves toward more sustainable farming practices have been taken to help re-establish catchment hydrological equilibrium and improve catchment ecosystem services. Agroforestry is one such vehicle for this reestablishment. Perennial native vegetation has been shown to have a significant effect on catchment processes, mitigating any further degradation of the land. The effect of alternating native perennial tree belts with traditional broad acre agriculture in the alleys, referred to as alley farming, is investigated in this thesis due to the potential environmental and economic benefits that can result. This thesis investigates the impact of tree belts upon the water table and aims to gauge the ability of alley farming at controlling recharge within the low-medium rainfall zone on the valley floor. The basis of this research is the analysis of data collected from the Toolibin Alley Faring Trial. This experiment was established in 1995 to assess the viability of alley farming and incorporates different combinations of belt width, alley width and revegetation density. Transects of piezometers within each design have been monitored from October 1995 to January 2008. The piezometers were sporadically monitored over this period on a total of 39 dates. ... To further understand the response observed in the water table data, in depth hydrograph analysis of the control piezometer water levels was conducted. The statistical analysis demonstrates that the belts are having a very limited impact on the water table morphology, this is associated with the restricted use of groundwater by the perennial tree belts due to the poor quality, has been applied. This explains why there is limited signature of increased water table depth in the statistical analysis; there is evidence that alley farming as a means of reducing recharge may work however the overriding control on the trial are the rainfall trends rather than perennial growth. The low perennial biomass production at the site is an effect of limited water resources; however a significant distinction can be made between the water table depth and variability beneath high and low biomass belts. There are three main controls at the site; climate, development of perennial biomass and development of perennial root systems (both vertically and laterally). The regional climatic trends will influence water table levels creating a greater soil water storage capacity; therefore the contribution of soil water to transpiration rates will enable the tree belts to have some impact on recharge. Of the alley farming designs tested, the optimal planting density and belt/alley design, from an economic perspective, is identified as having a 4m belt width which generated the greatest biomass. As a means of controlling recharge at the site the effectiveness of alley farming is limited due the shallow saline water table limiting perennial growth.