Sixteen modern Nothofagus solandri tree-ring chronologies, developed from sites near the alpine timberline, South Island, New Zealand are presented. The statistical properties of the chronologies are similar, having high mean sensitivity values (mean of 0.34), moderate autocorrelation values (mean of 0.50), and high common variance values (mean of 42 %). However, the chronologies are mainly less than 300 years in length. Examination of interchronology variation suggests that the similarity between two chronologies decreases with increasing distance. It is concluded that these chronologies offer considerable potential for reconstructing palaeoclimates, especially palaeotemperature.

Spline functions were examined and compared with conventional polynomials for use in filtering nonclimatic variance from tree-ring width series. Both types of curve were fitted to ring-width series exhibiting particularly marked effects of competition and release from competition with neighboring trees during the last 100 years. Available climatic data from that interval were used to statistically evaluate the capabilities of each type of function for removing nonclimatic effects and preserving the climatic signal. The results suggest that both types of function can be used successfully for those purposes, though in the presence of extremely rapid changes in growth rate due to a sudden release from competition it may be necessary to divide the ring-width series into two segments and fit a separate curve to each segment. Tightly-fit polynomials seem to be about as effective as splines, but are less desirable from a computational point of view as, for example, when the magnitude of the (negative) exponents of the coefficients exceeds computer capacity. Further, a spline function can be prescribed from its frequency-response characteristics, so it is possible to specify in advance the extent to which it will filter out any potential climatic cycles.

A simple method of testing the statistical significance of the summary response function derived by Pilcher and Gray is given and applied to European oak data.

Five modern Nothofagus menziesii tree-ring chronologies, developed from sites near the alpine timberline, South Island, New Zealand, are presented. The properties of the chronologies are described; as a group they have high mean sensitivity values (mean of 0.31), moderate autocorrelation values (mean of 0.42) and moderate common variance values (mean of 31 %). One site, lying some 200 km distant from the others, is the least similar of the five chronologies. It is concluded that both the long length of N. menziesii chronologies and the proximity of trees to the alpine timberline present considerable potential for reconstructing palaeotemperatures.

Populus balsamifera grows farther north than any other tree in North America. In northern Alaska, these trees have clear annual growth rings, and reach ages over 230 years. High year-to-year variability in ring widths permitted ready crossdating. A chronology prepared using paired cores from 16 trees exhibits mean sensitivity (0.48) and standard deviation (0.50) values much higher than those obtained from most conifer species in the Arctic. First order autocorrelation (0.43) is also lower than most Arctic species. A strong correlation (r =0.47) with June temperature suggests balsam poplar may provide a good record of growing season temperature.

Dendrochronological problems in dating tropical tree species are responsible for a large gap in global dendroclimatic reconstructions. Study of Cedrela and Juglans in the low-latitude forests of northern Argentina and Bolivia has resulted in development of four chronologies. These genera have good tree-ring characteristics, and statistics indicate that they have good potential for dendroclimatology. Longer series should be obtained from older stands.

In the continental United States, mean surface air temperature is expected to increase by up to 5°C within 100 years. With hotter temperatures, leaf budbreak is expected to occur earlier in forests, and leaf area is expected to increase in locations where temperature is limiting. The response of plant photosynthesis to hotter temperatures is less certain; plant productivity could increase or decrease. Past studies have found intraspecific variation in the responses of forest tree productivity, phenology, canopy leaf area, and leaf isoprene emission to warming, which all influence carbon uptake and yield for agricultural tree species; it is therefore important to understand not only how hot climates affect carbon uptake and biomass production between different tree species, but also in different genotypes of the same species. We conducted a common garden study at the Biosphere 2 research center near Oracle, AZ, USA. We created a hybrid poplar plantation of 168 trees, which were planted as cuttings in January 2013. The trees used in this study are comprised of 5 distinct genotypes of Populus deltoides × trichocarpa from a range of average annual air temperatures. We measured photosynthetic capacity, leaf phenological timing, canopy leaf area and aboveground woody biomass in 2014 growing season, and leaf isoprene emission in the 2015 growing season. We observed a strong effect of genotype on aboveground woody biomass increment, implying strong local adaptation to the home range and limited phenotypic plasticity in terms of physiological and biometric responses to high temperature environments. Our study suggests that genotypes from hotter home ranges are able to maintain photosynthetic capacity and canopy leaf area late into the growing season, despite high temperatures, and thus produce more aboveground woody biomass. This study may have implications for agricultural management—as temperatures warm where managers currently grow hybrid poplar for agricultural or other purposes, the genotypes from those home ranges would likely have reduced yield; managers could investigate the use of genotypes from home ranges with higher average temperatures to replace the vulnerable local varieties.

The thesis focuses on segmentation of images with leaves of woody species. The main aim was to investigate existing image segmentation methods, choose suitable method for given data and implement it. Inputs are scanned leaves and photographs of various quality. The thesis summarizes the general methods of image segmentation and describes algorithm that gives us the best results. Based on the histogram, the algorithm decides whether the input is of sufficient quality and can be segmented by Otsu algorithm or is not and should be segmented using GrowCut algorithm. Next, the image is improved by morphological closing and holes filling. Finally, only the largest object is left. Results are illustrated using generated output images. Powered by TCPDF (www.tcpdf.org)

Thesis advisor: Noah P. Snyder / Thesis advisor: Gail C. Kineke / Maine coastal rivers host the last remaining runs of endangered anadromous Atlantic salmon in the United States, whose populations have decline from ~500,000 returning adults in the 1880s to only ~1000 in 2000. Restoration projects have focused on these coastal river systems to bring natural populations back to the area, and recent efforts involve adding large woody debris (LWD) to small tributaries to improve salmon rearing habitat. Large woody debris actively changes the hydraulics and geomorphology of small streams by acting as a barrier to flow and creating decreased velocity zones, scour pools, and sediment storage and sorting. I study the effects of LWD additions in early August 2008 on hydraulics and substrate in Baker Brook, a west-flowing tributary of the Narraguagus River. Hydraulically, I focus on the treatment reach nearest the confluence with the Narraguagus River (Baker1), and I also study changes in substrate in Baker1 and the upstream treatment location (Baker3). Both study locations are divided into two reaches, treatment (Baker1-T and Baker3-T) and control (Baker1-C and Baker3-C). In Baker1, the treatment and control reaches are further divided into four 50 m sub-reaches based on channel gradient (~1% in Baker1-C-Flat and Baker1-T-Flat; >2% in Baker1-C-Steep and Baker1-T-Steep). In Baker3, we use two 50 m sub-reaches of similar gradient (ranges from ~1% to 2%) to determine substrate changes. Significant post-LWD addition changes are determined by comparison with the control sub-reaches. Changes in the treatment sub-reaches must be larger than those in the control sub-reaches to be deemed significant. I seek to answer three research questions: (1) how much does mean velocity through the study sub-reaches change as a result of additions; (2) how much does hydraulic roughness change; and (3) does sediment storage and spatial sorting result from the LWD additions? I measured reach-average velocities (Ureach) in Baker1 using the salt dilution method in May, July and August 2008 and May 2009. I use rating curves to compare the post-treatment to the pre-treatment Ureach-stage relationship. A temporary decrease in Ureach occurred in October 2008 in Baker1-T-Flat, whereas the other sub-reaches experienced no change in Ureach. A localized change in cross-sectionally averaged velocity (U) measured with a flow meter, is also evident at Baker1-T-Flat, but this is because an added tree lies directly in the downstream cross-section where measurements are recorded. I assessed channel roughness changes by comparing roughness rating curves created using the Manning roughness parameter, n (back-calculated from velocity measurements) for each sub-reach. Because of the short-term decrease in Ureach, roughness increased in Baker1-T-Flat in October 2008 as well. No change in roughness is evident in the other sub-reaches because post-treatment values of n plot on the same decreasing trend with respect to stage as pre-treatment values. I quantified pre- and post-treatment sub-reach substrate median grain size (D50) with intensive clast counts in July 2008 and May 2009. In Baker1, analysis of pre-treatment substrate size show that the flat sub-reaches have a finer substrate size (34-38 mm) than the steep sub-reaches (88-134 mm). Baker3 pre-treatment grain size is similar to that of the flat Baker1 sub-reaches, with a median grain size of 38 mm in Baker3-T and 28 mm in Baker3-C. Two of the three treatment sub-reaches exhibited significant fining (D50 decreased by 37-54%) between the surveys, and the third changed less than measurement uncertainty. One of the three control sub-reaches coarsened significantly (D50 increased by 29%), one fined significantly (-42%), and one coarsened less than measurement uncertainty. In summary, I find that LWD additions in Baker Brook had little effect on reach-scale hydraulics during the flows we observed, but did influence bed-grain size during the 10-month study interval, underscoring the importance of floods on channel change. / Thesis (MS) — Boston College, 2009. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

The ecology of plant species at Sandford Rocks Nature Reserve (SRNR) was studied. The study site is an important nature reserve that contains relatively undisturbed natural vegetation. It has a mosaic of exposed granite rocks, scrublands and woodlands. The study involved: a description of the structure and composition of the vegetation; the population characteristics of selected Acacia species; aspects of reproduction in Acacia; germination and seedling characteristics of some Acacia and grass species that dominate the reserve; the effect of seed size on germination and seedling characteristics; and, the relationship of seed size to seed coat thickness in selected Acacia species. Five different areas were studied using the point centered quarter method to sample the woody perennial species. Thirteen Acacia species were examined for reproduction characteristics; and in 2 selected Acacia species, the effects of phyllode and/or inflorescence removal on reproduction was investigated. Germination tests were conducted to identify germination characteristics in 8 Acacia and 7 grass species dominant at SRNR. The possible effects of variation in seed size on germination; seedling characteristics; and, seed coat thickness were investigated in Acacia fauntleroyi and Acacia prainii. A total of 85 species from 20 families of woody perennials were collated. All areas were dominated by the Myrtaceae, Mimosaceae and Proteaceae families. There was considerable variability in the structure and composition of vegetation. Most species were present in particular sites and the composition of communities appears to be related to the heterogeneity of the habitat within the reserve. In areas of shallow or rocky soil, vegetation types present include Allocasuarina huegeliana woodland, Grevillea paradoxa low scrubland and Acacia neurophylla medium shrubland. / In a seasonally wet area, vegetation types present include low open grassland; Eucalyptus capillosa (wandoo) woodland; and, Acacia saligna thicket. In deep, dry sandy soil, vegetation types include Phebalium tuberculosum shrubland, Acacia acuminata and Acacia coolgardiensis thickets. On relatively flat areas that gain water from adjacent large granite hills, the vegetation consists mainly of tall, open woodlands of Eucalyptus species. Vegetation types include: medium tall Eucalyptus salmonophloia woodland with Kunzea pulchella shrubland at the periphery of the Eucalyptus woodland. At rock areas, vegetation types present include dense Leptospermum erubescens thicket, low open Acacia prainii and Dodonaea viscosa shrubland. Of the Acacia populations studied, in A. lasiocalyx no recent seedling establishment was observed. It is hypothesised that recruitment occurs in particular periods. As the plants are associated with rock and soils are generally shallow, it appears that recruitment depends on run-off water from the rocks in winter. Continuous recruitment seems to be the pattern in A. prainii with both seedlings and saplings represented. A. fauntleroyi forms relatively small populations; apparently long drought periods (>l00 d) result in mass death and limit its population size. In A. hemiteles, no seedling stage was found, root competition (for water) from associated Eucalyptus species presumably limits its recruitment. Reproductive success of Acacia is affected by rainfall. A wet winter is required to induce flowering and further rain is required after flowering to promote pod development and good seed set. / All Acacia species suffer from drought in the reproduction season, however they differ in their degree of susceptibility. Leaflessness and tree shape also affect Acacia fecundity. Plants bearing more phyllodes produce more flowers and pods, and branches in the upper part of the crown bear heavier inflorescences. In 1998, all Acacia species at SRNR produced mature seed of low weight, with many immature and diseased seed, which gave poor germination. A late spring frost in 1998 is believed to be responsible for limited seed development. In two selected Acacia species, removal of phyllodes reduced the number of pods produced. Presumably, phyllode removal reduces photosynthate produced, therefore the competition among inflorescences (or pods) for resources is more intense and subsequent abortions are likely to occur. All Acacia species studied showed best germination in the cool winter temperature range. Apparently, seeds are adapted to germinate in winter when seasonal moisture is more likely to be available. The best temperature however, varied slightly between species. The grass species dominant in the reserve, except for Aristida contorta, also had more germination in cooler rather than warmer temperatures. The flora of SRNR is similar to typical vegetation of the Southwest. Generally, Acacia species are present only in particular sites, presumably were habitat moisture allows. Seedlings of Acacia species growing in naturally dry areas have greater root: shoot masses than those growing in seasonally wet areas. Biomass partitioning is an apparent strategy to conserve water. Of the 7 grass species, Amphipogon strictus appears to have fastest growth. / Eriachne ovata has greater root than shoot mass, while in all other species, shoot mass is greater than root mass; a characteristic of species that grow well in moist habitats. The longest shoots and roots are in Austrostipa elegantissima, an understorey species of eucalypt woodland. In A. fauntleroyi, the degree of hard-seededness varies between seed sizes. There is a higher proportion of soft seed in smaller seed. Seed of different sizes show some responses to different pre-treatments and incubation temperatures for germination. Larger seeds generally germinate in greater numbers after higher treatment temperatures. The best treatment for small seeds is pre-treatment at 75°C and incubated at 15°C. For medium and large seed, best pre-treatment is at 75°C with incubation at 30°C or soaking in boiling water and incubation at either 15 or 3°C. In A. prainii, seed size; pre-treatment; incubation; and, their interaction all affected germination; larger seeds are more viable. The best treatment to promote germination of A. prainii is soaking in boiling water and incubation at 25°C. In both A. fauntleroyi and A. prainii, larger seeds produce larger seedlings. Seedlings from large seeds have the potential for more rapid pre-photosynthetic growth. Larger, heavier seed has a thicker seed coat. The seed coat of A. prainii is thicker than in A. fauntleroyi; the difference in seed coat thickness is reflected by more soft seed in A. fauntleroyi (35%) than in A. prainii (6%).