Michael G. Messina

Initial responses of woody vegetation, water quality, and soils to harvesting intensity in a Texas bottomland hardwood ecosystem

Sustainable management of bottomland hardwood forest ecosystems requires a knowledge of responses to management impacts, including timber harvesting. The effects of clearcutting and partial cutting on woody vegetation regeneration dynamics, surface and groundwater quality, soil physical properties, and soil respiration were tested in a bottomland hardwood ecosystem in southeastern Texas, USA, through comparison with non-cut control areas. Overstory removal only slightly affected composition of woody vegetation regeneration 1 year after harvesting compared with pre-harvest composition. Initial composition in both cutting treatments appeared to be the strongest determinant of post-harvest composition, at least for the first year after harvesting. There were few significant differences in groundwater properties when harvesting treatments were compared with control areas during a 17-month period following harvest. Turbidity, temperature, electrical conductivity, dissolved O2, NH4-N, NO3-N, and PO4-P of streamwater did not vary significantly among treatments. Slight decreases in total and macroporosity were observed in association with higher bulk densities at 0–5 cm depth in the clearcut and partial cut treatments. Saturated hydraulic conductivity values did not decline significantly with treatment intensity. No significant differences among treatments in measured soil physical properties were observed at 5–10 cm depth. Although in situ soil respiration increased with harvest intensity, treatment had no significant effect on mineral soil respiration. In summary, most variables showed only slight response to harvesting, thereby indicating that harvesting practices can be conducted with minimal initial impacts on measured response variables.

Effects of silvicultural activity on ecological processes in floodplain forests of the southern United States: a review of existing reports

Activities associated with timber harvesting have occurred within floodplain forests in the southern United States for nearly two hundred years. However, it is only in the last ten years that any information has become available about the effects of harvesting on the ecological functions of this valuable resource. Hydrology is the driving influence behind all ecological processes in floodplains, and timber harvesting alone usually has little long-term effect on hydroperiod. However, logging roads, built in association with harvest sites, can sometimes alter hydroperiod to the extent that vegetation productivity is raised or lowered. There is no evidence that harvesting followed by natural regeneration represents a threat to ground or surface water quality on flood plain sites, as long as “best management practices” are followed. Harvested floodplains may increase or have little effect on decomposition rates of surface organic matter. The nature of the effect seems to be controlled by site wetness. Data from recently harvested sites (i.e. within the last ten years) suggest that vegetation productivity is maintained at levels similar to those observed prior to harvests. During the early stages of stand development, tree species composition is heavily influenced by harvest method. Similarly, amphibian populations (monitored as bioindicators of ecosystem recovery) seem to rebound rapidly following harvests, although species composition may be different from that of unharvested stands.

Response of Eucalyptus regnans F. Muell. to thinning and urea fertilization in New Zealand

A 7-year-old Eucalyptus regnans plantation on the North Island of New Zealand was urea fertilized (230 and 460 kg N ha−1) and thinned to 350 and 150 trees ha−1 (TPH) from an initial stand density of 1200 TPH. Tree diameter, height, and crown height were measured periodically for the next 2.5 years. Crop trees (the 100 TPH with the largest diameter at final measurement) responded to both thinning and fertilization with greater diameter growth at the intermediate levels of both treatments. Thinning increased diameter growth slightly more than did fertilization. There was no interaction of thinning and fertilization on diameter growth. Thinning tended to decrease height growth while fertilization had a small positive effect on height growth. Live crown ratio was increased by both thinning and fertilization. Effects on stand basal area and volume increment were similar to those for diameter. Foliar nutrient analyses showed that the highest level of fertilization lowered concentrations of non-fertilizer elements and substantially altered ratios of nitrogen to the other elements. This possibly caused the lack of response at that level of fertilization. Radical thinning to final crop stocking (150 TPH) at an early age did not offer any growth advantage over less extreme thinning (350 TPH). The heaviest rate of fertilization (460 kg N ha−1) at any level of thinning did not increase growth. Therefore, more moderate rates of thinning and fertilization are recommended in young E. regnans plantations.

Variation of the treefall gap regime in a bottomland hardwood forest: relationships with microtopography

Abstract Treefall gaps, formed as a result of small-scale disturbances, allow seedling recruitment and growth in forests where large-scale disturbances are infrequent. Many factors contribute to gap regime heterogeneity within and among forest stands, including wind and fire patterns, stand age, stand composition, and site hydrology. While there is evidence suggesting that topography can also affect gap formation, most studies have examined gaps in steep terrain rather than in relatively level terrain such as bottomland hardwood forests. This study examined the treefall gap regime among three microtopographical classes—ridge, slope, and bowl—in a bottomland hardwood stand in the Big Thicket region of east Texas. The null hypothesis that the gap regime does not vary among microtopographical positions was tested. Using point sampling, microtopographic variation was estimated throughout the site. Line intersect sampling was used to select gaps for measurement of gap frequency, area, fraction (percent cover) and abundance (density) within the study area. While gap area and frequency did not vary among microtopographical classes, fraction and abundance differed significantly. Ridges contained the highest fraction and highest abundance compared to slopes and bowls. Based on these findings, the null hypothesis was rejected and we concluded that microtopography affects at least some aspects of the gap regime in this bottomland hardwood forest.

Estimating regional forest cover in East Texas using Advanced Very High Resolution Radiometer (AVHRR) data

This study tested the degree to which single date, near-nadir AVHRR image could provide forest cover estimates comparable to the phase I estimates obtained from the traditional photo-based techniques of the Forest Inventory and Analysis (FIA) program. FIA program is part of the United States Department of Agriculture-Forest Service (USFS). A six-county region in east Texas was selected for this study. Manual identification of ground control points (GCPs) was necessary for geo-referencing this image with higher precision. Through digital image classification techniques forest classes were separated from other non-forest classes in the study area. Classified AVHRR imagery was compared to two verification datasets: photo-center points and the USFS FIA plots. The overall accuracy values obtained were 67 and 71%, respectively. Analyses of the error matrices indicated that the AVHRR image correctly classified more forested areas than non-forested areas; however, most of the errors could be attributed to certain land cover and land use classes. Several pastures with tree cover, which were field-identified as non-forest, were misclassified as forest in the AVHRR image using the image classification system developed in this study. Recently harvested and young pine forests were misclassified as non-forest in the imagery. County-level forest cover estimates obtained from the AVHRR imagery were within the 95% confidence interval of the corresponding estimates from traditional photo-based methods. These results indicate that AVHRR imagery could be used to estimate county-level forest cover; however, the precision associated with these estimates was lower than that obtained through traditional photo-based techniques.

Issues related to wetland delineation of a Texas, USA bottomland hardwood forest

Methods of wetland delineation require presence of three parameters: hydric soils, wetland hydrology, and hydrophytic vegetation. Currently accepted methods to assess these parameters often have inconsistent agreement among the parameters in bottomland hardwood forested wetlands. This study characterized soil morphology, hydrology, and vegetative composition in a bottomland hardwood forest in east Texas, USA. Alternate methods for assessment of the three parameters were examined with the aim of determining if there is an approach that provides better agreement among parameters than methods in current use. We compared four methods for determining dominance ratios and a prevalence index to assess the status of vegetation. The most stringent method of assessment and the method that provided best agreement with soil and hydrology parameters at this site was a prevalence index. We compared three criteria to assess the hydrology parameter: (1) length of growing season as defined by air temperature greater than −2°C (28°F) vs. 0°C (32°F), (2) saturation or inundation for 5% vs. 12.5% of the growing season, and (3) saturation to within 30 cm vs. 15 cm of the soil surface. Length of growing season had little or no effect on the outcome at this site; duration of required hydrology had the greatest influence over agreement with vegetation and soil parameters. We also compared the field method used to determine presence of hydric soil when sampling was conducted in 1995 with currently used field indicators. The combination that, in general, provided better agreement among the three parameters at this site was saturation to within 15 cm of the surface for 12.5% of the growing season, using current field indicators for hydric soil. Despite having been mapped as a wetland by the National Wetlands Inventory, under current federal guidelines, most of this bottomland hardwood forest would not be a jurisdictional wetland as defined by Clean Water Act regulations.

The Role of the Sustainable Forestry Initiative in Forest Landscape Changes in Texas, USA

We studied the changes in landscape pattern and function resulting from the application of the Sustainable Forestry Initiative (SFI) in East Texas, USA. Changes in landscape structure were studied by comparing landscapes with different management histories. A methodology to integrate landscape and stand pattern dynamics with processes was developed based upon modeling and simulation. The effects of pattern on processes were analyzed with this methodology considering the quality, quantity and configuration of vertebrate habitat and hydrological processes.

Performance of loblolly pine (Pinus taeda L.) seedlings and micropropagated plantlets on an east Texas site: I. Above- and belowground growth

Abstract East Texas contains the western extent of the natural range of loblolly pine (Pinus taeda L.) and, therefore, many planted seedlings there experience water deficit sometimes leading to plantation failure. One solution may be to regenerate with clonally propagated drought-hardy planting stock. The objective of this research was to compare the field performance of loblolly pine seedlings and plantlets of diverse genetic origin, produced via micropropagation technology. Two adjacent sites were established (Site I in 1993 and Site II in 1994) with trees produced from four genetic families: Liberty (LIB) and Montgomery (MON) Counties from southeast Texas, and Fayette (FAY) and Bastrop (BAS) Counties from the “Lost Pines” in Central Texas. Height, groundline diameter (GLD), leaf area, survival, root/shoot ratio, and root system architecture were measured throughout the 1994 and 1995 growing seasons. In addition, height and diameter at breast height on Site II were measured at the end of 1999 and 2000 growing seasons. Height and GLD growth for seedlings was significantly greater than for plantlets on both sites. However, mean relative growth rates for height were greater for plantlets during the first growing season, but comparable thereafter. Survival for all treatments was >85% on Site I and >90% on Site II at the end of the 1995 growing season. Survival was significantly different, but by a negligible margin, between families and stock types on Site II at the end of the 1995 growing season, and by a margin of 7% (89% for seedlings vs. 82% for plantlets) at the end of the 2000 growing season. Seedlings had greater leaf area growth than plantlets after two growing seasons. Root/shoot ratio was significantly greater for plantlets after two growing seasons, whereas their specific root length was significantly smaller than that of seedlings. This was attributed to root system architecture. Whereas plantlets produced thicker roots with less length per unit dry weight, seedlings produced more branching with thinner roots for similar dry weights.

Irrigation effects on growth and water use of Quercus virginiana (Mill.) on a Texas lignite surface-mined site

Abstract Three different irrigation regimes (100%-high, 67%-medium and 33%-low of estimated well-watered conditions) were applied to Quercus virginiana (live oak) seedlings on reclaimed lignite surface-mined soils in central Texas as a means to study the physiology and growth of seedlings during establishment. The study period was 4 July 1990 through 30 September 1990. Transpiration, stomatal conductance and water potential were significantly higher (α = 0.05) in the high treatment than in the low and medium treatments. Favorable water status contributed to somewhat greater seedling growth in the high treatment than in the low and medium treatments. Greater growth was associated with favorable seedling water potential, high stomatal conductance and rapid transpiration in the high treatment. Physiological responses and growth characteristics indicated that an irrigation rate of 1.2 kg·d−1 per seedling during the dry summer months was sufficient for seedling survival and establishment. An irrigation rate of 3.8 kg·d−1 per seedling promoted rapid seedling growth in addition to ensuring establishment.

Effects of the Sustainable Forestry Initiative on the Quality, Abundance, and Configuration of Wildlife Habitats

Abstract We analyzed the effects of landscape measures within the Sustainable Forestry Initiative (SFI) program on the suitability, abundance and spatial pattern of vertebrate habitats based on modeling and simulation of landscape and stand structure in a forested watershed in East Texas. Eight vertebrate species representing guilds established according to breeding and foraging requirements were selected: American beaver (Castor canadensis), American woodcock (Scolopax minor), pine warbler (Dendroicapinus), downy woodpecker (Picoides pubescens), barred owl (Strix varia), wild turkey (Meleagris gallopavo silvestris), fox squirrel (Sciurus niger) and gray squirrel (Sciurus carolinensis). Habitat suitability of the landscape in general increased with the implementation of SFI measures and habitat conditions were more diverse and even. Fragmentation and establishment of narrow and elongated habitat areas in a network configuration were the main consequences of the implementation of SFI measures in terms of habitat spatial structure. These changes were usually not limiting for the species analyzed. Mature pine and hardwood stands were absent from the simulated landscapes limiting the habitat for species like downy woodpecker or barred owl. Most of the species considered in this work benefited particularly from the implementation of streamside management zones (SMZs).