Relations between damage symptoms and nutritional status of Norway spruce stands (Picea abies Karst.) in southwestern Germany

Since the mid-1970s new types of forest damage are observed in the Federal Republic of Germany. Typical damage symptoms in coniferous tree species are needle yellowing, reddening and premature loss of older foliage. Needle analysis carried out in damaged Norway spruce stands indicated that these phenomena, most of all needle yellowing, are influenced by the nutritional status of the trees. For the investigated sites Mg but also other elements, particularly P, S, K, Ca and Zn may play a causal role. As N is the most abundant element in the plant its form of uptake is important for a balanced nutrition. On the contrary to NO₃-N high NH₄-N uptake reduces the uptake of cations, particularly Mg and Ca, eventually inducing foliar discoloration symptoms on specific sites. Fertilizer experiments indicated that Mg fertilization is an appropriate tool to mitigate forest damages associated with Mg deficiency for a sustained time period. The application of N in the form of NH₄-N may impede Mg uptake. This mechanism may cause severe damage in forest areas receiving continuously high NH₄-N deposition.     

An Optical Parametric Amplified Fiber Switch for Optical Signal Processing and Regeneration

An optical parametric amplified (OPA) fiber switch is described in this paper. This device switches input signals without shifting the wavelength by changing the polarization state of the signal using optical parametric amplification. The OPA fiber switch features ultra-broadband, highly efficient switching with a high contrast ratio. We experimentally test the prototype of the OPA fiber switch, which uses a highly nonlinear fiber. Optical demultiplexing of 160 Gb/s differential phase-shift keying (DPSK) signals is demonstrated in the whole C-band and shows that it provides almost penalty-free optical detection. The application of amplitude noise suppression with the OPA fiber switch by using parametric gain saturation is then proposed and demonstrated for a 160 Gb/s DPSK signal. When it is set to an amplitude-limiting condition, the OPA fiber switch successfully increases the optical signal-to-noise ratio by 4 dB and effectively suppresses the phase deterioration in 160 Gb/s DPSK transmission by increasing the system margin by more than 5 dB.     

Nutrient management of forests under stress for improved health and increased productivity

Invited paper for IUFRO World Congress, Montreal, Canada, August 6–11, 1990.     

GDNF improves dopamine function in the substantia nigra but not the putamen of unilateral MPTP-lesioned rhesus monkeys

Microdialysis measurements of dopamine (DA) and DA metabolites were carried out in the putamen and substantia nigra of unilateral 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned rhesus monkeys that received intraventricular injections of vehicle or glial-derived neurotrophic factor (GDNF, 300 microg) 3 weeks prior to the microdialysis studies. Following behavioral measures in the MPTP-lesioned monkeys, they were anesthetized with isoflurane and placed in a stereotaxic apparatus. Magnetic resonance imaging (MRI)-guided sterile stereotaxic procedures were used for implantations of the microdialysis probes. Basal extracellular levels of DA and the DA metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), were found to be decreased by >95% in the right putamen of the MPTP-lesioned monkeys as compared to normal animals. In contrast, basal DA levels were not significantly decreased, and DOPAC and HVA levels were decreased by only 65% and 30%, respectively, in the MPTP-lesioned substantia nigra. Significant reductions in d-amphetamine-evoked DA release were also observed in the MPTP-lesioned substantia nigra and putamen of the monkeys as compared to normal animals. A single intraventricular administration of GDNF into one group of MPTP-lesioned monkeys elicited improvements in the parkinsonian symptoms in these animals at 2-3 weeks post-administration. In addition, d-amphetamine-evoked overflow of DA was significantly increased in the substantia nigra but not the putamen of MPTP-lesioned monkeys that had received GDNF. Moreover, post-mortem brain tissue studies showed increases in whole tissue levels of DA and DA metabolite levels primarily within the substantia nigra in MPTP-lesioned monkeys that had received GDNF. Taken together, these data support that single ventricular infusions of GDNF produce improvements in motoric behavior in MPTP-lesioned monkeys that correlate with increases in DA neuronal function that are localized to the substantia nigra and not the putamen.