The effects of water-level fluctuations on weekly tree growth in a southeastern usa swamp

Annual growth of wetland trees has been shown to be related to variations in hydrologic regimes, however the relationship between water level fluctuations and tree growth throughout the growing season has not been documented. In a study of weekly growth patterns of three wetland tree species in a southeastern forested wetland, transfer function modeling was used to examine relationships between tree growth and the weekly changes in water levels and weekly changes in the atmospheric water balance (precipitation minus potential evapotranspiration). An autoregressive-moving average model was fit to each time series of water-level changes (input series), and the selected model was then used to filter the tree-growth (output) time series. Cross-correlations between each input and output time series were examined and significant relationships between weekly changes in water levels and tree diameter were found for Nyssa sylvatica and Taxodium distichum trees growing at sites with periodic shallow flooding. There were no significant relationships between changing water levels and tree growth in areas with permanent flooding or soil saturation. Further, changes in growth of N. sylvatica, N. aquatica, and T. distichum were significantly cross-correlated with weekly changes in the atmospheric water balance at sites with either periodic or permanent flooding.     

Antimicrobial activity of certain essential oils against hindgut symbionts of the drywood termite Kalotermes flavicollis Fabr. and prevalent fungi on termite-infested wood

Abstract:  When the kalotermitid Kalotermes flavicollis Fabr. pseudergates exposed to Casuarina wood wafers treated separately with different concentrations (5, 15 and 30  μ l/2 g wood wafer) of the essential oils, their spirochaete and flagellate populations abnormally reduced in numbers and vigour. The lophomonadids Joenia sp. and Mesojoenia sp. were the most adversely affected flagellates followed by the polymastigid Foaina sp. and the trichomonadid Tricercomitus sp. The Taxodium distichum essential oil evidently appeared to have the greatest adverse effect on the flagellates (95–100% decline in numbers within 2–4 days) followed by the Eucalyptus citriodora (89–100%) and the Cupressus sempervirens oils (31–100%). While with the hindgut spirochaetes, the adverse effect seemed to be reversed where the E. citriodora essential oil had the greatest effect (54–100%) followed by C. sempervirens (46–100%) and T. distichum (8–100%) oils. Moreover, the essential oils were assayed for their antifungal activity, at 15, 20, 25, 30, and 50  μ l/1 ml acetone/15 ml Czapek-Dox medium, against isolates of four woodrotting fungi associated with Casuarina timber, Aspergillus sp., Penicillium sp., Fusarium sp. and Mucor sp. by a method based on inhibition of the fungus growth on agar plates. E. citriodora exhibited the most potent fungicidal activity against the tested four fungi, followed by T. distichum oil. While the C. sempervirens essential oil appeared to have the least significant antifungal property.     

Response of pondcypress growth rates to sewage effluent application

Cores were collected from dominant pondcypress trees growing in a swamp that had received sewage effluent for 7 yr and a nearby control swamp to determine the combined effects of changes in nutrient supply and hydrologic regime on tree growth. The cores were used to measure two indices of tree growth: basal area increment (BAI) and relative basal area increment (RBAI, which accounts for differences in growth due to the size of teh tree) between 1970–1983 while one swamp remained untreated and the other received weekly additions of sewage effluent from 1974–1981. Throughout the whole period, the mean BAI and RBAI of pond-cypress trees in the untreated swamp remained unchanged, ranging between 5.55–6.38 cm² yr^–1 and 1.09–1.27% yr^–1, respectively. In contrast, trees in the treated swamp increased their BAI approximately two-fold from 7.40 cm² yr^–1 prior to treatment to 14.83 cm² yr^–1 after the onset of treatment and maintained this rate of growth in the 2 yr period after cessation of treatment. Relative basal area increment showed a similar response, but the proportional increase due to treatment was less (1.5-fold factor) than for BAI. The response of pondcypress trees to the sewage effluent differed depending upon whether the trees were located in the deep or shallow water zones. Trees in the deep zone of the treated swamp had lower BAIs and RBAIs than those in the shallow zone during the treatment period, whereas in pre- and post-treatment periods growth indices were equal in both zones. No significant differences in growth between deep and shallow zones were observed during all three time periods in the control swamp.     

落羽杉根系有机酸与NSC代谢对三峡消落带水位变化的响应

为探究三峡库区消落带水位变化下落羽杉根系有机酸和非结构性碳水化合物(NSC)的响应特征,以适生木本植物落羽杉为对象,在消落带原位环境中设置对照-SS(海拔175 m,试验期间无水淹)、MS(海拔170 m,中度水淹胁迫)和DS(海拔165 m,深度水淹胁迫)3个处理,分别于海拔170 m和165 m退水时采集样品,测定并分析根系有机酸和NSC的变化。结果表明:(1)库区水淹对落羽杉基径无显著影响,仅有DS组明显抑制了高生长,落羽杉生长能较积极地响应库区水淹。(2)库区水淹对落羽杉侧根和总根有机酸的影响一致,侧根有机酸代谢作用优于主根。与SS组相比,MS组根系有机酸含量增高,DS组根系有机酸含量降低,除部分根系酒石酸、苹果酸、柠檬酸变化达到显著水平外,其余有机酸均无显著变化。(3)库区不同强度水淹对落羽杉根系NSC有不同程度的影响。与SS组相比,MS组可溶性糖无显著变化,淀粉、NSC含量显著增加,但总根NSC在水淹前与水淹后无明显差异;形成鲜明对比的是,DS组显著降低了可溶性糖、NSC含量,对淀粉无显著影响,且水淹后总根NSC显著低于水淹前。(4)相关分析表明,主根、总根草酸、苹果酸、柠檬酸及侧根、总根莽草酸分别与淀粉、NSC间表现出显著相关性(P0.05)。研究结果表明,在三峡库区消落带水淹胁迫下,落羽杉根系有机酸与NSC代谢联系紧密。通过维持一定的根系淀粉含量,保持植株正常的有机酸代谢水平,较好地适应三峡库区消落带生境。     

中山杉及其父母本幼苗对干旱胁迫和复水的响应

本文研究了落羽杉和墨杉及其杂交后代中山杉302(落羽杉♀×墨杉♂)、中山杉407(墨杉♀×落羽杉♂)、回交代中山杉118(中山杉302♀×墨杉♂)在自然干旱胁迫和复水过程中,光合特征、抗氧化酶系统和形态特性等的响应.结果表明:随干旱时间的延长,所有植株的净光合速率逐渐降低、脯氨酸开始积累且抗氧化酶系统逐渐清除丙二醛的毒性.胁迫至第8天,落羽杉净光合速率的下降幅度最大,而中山杉118的水分利用效率最高、丙二醛含量最少;墨杉的超氧化物歧化酶活性和脯氨酸含量增长最大.复水2 d后,所有植物的参数均有不同程度的恢复,其中,中山杉118恢复速率最快,其净光合速率和脯氨酸含量分别恢复了74.4%和60.2%.复水9 d后,所有植株的测定指标基本恢复至或接近正常水平,其中,中山杉118的生物量未受影响且根冠比显著增加.植物的耐旱能力依次为墨杉>中山杉118>中山杉407>中山杉302>落羽杉.回交品种中山杉118的杂种优势明显,较大程度地遗传了墨杉的耐旱性,该结论可为耐旱中山杉品种的杂交选育和推广应用提供科学依据.     

Native Alternatives for Non-Native Turfgrasses in Central Florida: Germination and Responses to Cultural Treatments

Little information exists about the establishment of native longleaf pine flatwoods species for use in restoration efforts and as buffers around natural areas in the southeastern United States. Composition of groundcover in these systems is dominated by perennial graminoid species. Vegetation in current buffers is generally non‐native turfgrass that can escape into natural areas, often reducing establishment and survival of native species. Where management objectives involve actively restoring native groundcover or reducing the probability of invasion by these non‐native turfgrasses, identification of native species and restoration methods is needed. We investigated seed germination and establishment of four species native to longleaf pine flatwoods in central Florida and one species native to the adjacent wetland communities. Paspalum setaceum, Panicum anceps, Eustachys petraea, and Eragrostis refracta were directly seeded, and P. distichum was planted as sprigs into three former P. notatum pastures. Irrigation, fertilization, weed control, and mowing treatments were assessed in terms of cover development of the sown species. Paspalum distichum developed the highest percent cover—over 80% in wet areas after 1 year. Mowing had mixed impacts depending on the species, and fertilization never significantly increased cover. Directly seeded species developed sparse cover (0–40%), probably as a result of drought conditions. However, E. petraea and E. refracta appeared more promising for use on rights‐of‐way when using high sowing rates. A second experiment conducted on a roadside included these two species and sprigged P. distichum. Both E. petraea and P. distichum developed more than 45% cover on the roadside. Establishment of these natives from seed or sprigs was significantly enhanced when site preparation effectively reduced the seedbank of other species present in the soil.     

Activity of Ion Transporters and Salt Tolerance in Barley

The authors attempted to relate the cultivar-specific salt tolerance in barley (Hordeum distichum L.) to the efficiency of ion transporters in the plasmalemma and tonoplast. The study involved plasmalemma and tonoplast membrane vesicles isolated from roots and leaves of the 7-day-old barley seedlings exposed to elevated NaCl concentrations. Two barley cultivars were employed: salt-tolerant cv. Elo and salt-susceptible cv. Belogorskii. The vesicles were used to measure the transport activity of plasmalemma and tonoplast proton pumps and the cation/anion exchange. The data obtained in the experiments demonstrated that the changes in the activity of ion transporters under salt stress conditions correlated with the barley cultivar-specific tolerance to elevated NaCl concentrations.     

Control of barley root respiration

Evidence from barley [ Hordeum distichum (L.) Lam. cv. Maris Mink], and from many other species, suggests that respiration is controlled by either supply of carbohydrate or demand for ATP. The relationship between root respiration rate (measured as O₂ consumption or CO₂ production) and ethanol-soluble carbohydrate content altered with time following selective pruning, and the change could not be accounted for by buffering of the cytoplasmic carbohydrate concentration by sugars in the vacuole. Exogenous sucrose supplied to the roots prevented any decline of the respiration rate in shoot-pruned plants, and if supplied for 24 h stimulated the respiration rate after any treatment. Root extension responded to sucrose in a similar manner. We suggest that respiration is under fine control by adenylates, but the capacity of the respiratory system is fixed by the supply of sucrose, possibly via coarse control of the respiratory machinery, or of the processes requiring metabolic energy.