Debating the greening vs. browning of the North American boreal forest: differences between satellite datasets

A number of remote sensing studies have evaluated the temporal trends of the normalized difference vegetation index (NDVI or vegetation greenness) in the North American boreal forest during the last two decades, often getting quite different results. To examine the effect that the use of different datasets might be having on the estimated trends, we compared the temporal trends of recently burned and unburned sites of boreal forest in central Canada calculated from two datasets: the Global Inventory, Monitoring, and Modeling Studies (GIMMS), which is the most commonly used 8 km dataset, and a new 1 km dataset developed by the Canadian Centre for Remote Sensing (CCRS). We compared the NDVI trends of both datasets along a fire severity gradient in order to evaluate the variance in regeneration rates. Temporal trends were calculated using the seasonal Mann–Kendall trend test, a rank‐based, nonparametric test, which is robust against seasonality, nonnormality, heteroscedasticity, missing values, and serial dependence. The results showed contrasting NDVI trends between the CCRS and the GIMMS datasets. The CCRS dataset showed NDVI increases in all recently burned sites and in 50% of the unburned sites. Surprisingly, the GIMMS dataset did not capture the NDVI recovery in most burned sites and even showed NDVI declines in some burned sites one decade after fire. Between 50% and 75% of GIMMS pixels showed NDVI decreases in the unburned forest compared with <1% of CCRS pixels. Being the most broadly used dataset for monitoring ecosystem and carbon balance changes, the bias towards negative trends in the GIMMS dataset in the North American boreal forest has broad implications for the evaluation of vegetation and carbon dynamics in this region and globally.     

PRIMARY PEPTIDE SEQUENCES FROM SQUID MUSCLE AND OPTIC LOBE MYOSIN IIs: A STRATEGY TO IDENTIFY AN ORGANELLE MYOSIN

The squid giant axon provides an excellent model system for the study of actin-based organelle transport likely to be mediated by myosins, but the identification of these motors has proven to be difficult. Here the authors purified and obtained primary peptide sequence of squid muscle myosin as a first step in a strategy designed to identify myosins in the squid nervous system. Limited digestion yielded fourteen peptides derived from the muscle myosin which possess high amino acid sequence identities to myosin II from scallop (60–95%) and chick pectoralis muscle (31–83%). Antibodies generated to this purified muscle myosin were used to isolate a potential myosin from squid optic lobe which yielded 11 peptide fragments. Sequences from six of these fragments identified this protein as a myosin II. The other five sequences matched myosin II (50–60%, identities), and some also matched unconventional myosins (33–50%). A single band that has a molecular weight similar to the myosin purified from optic lobe copurifies with axoplasmic organelles, and, like the optic lobe myosin, this band is also recognized by the antibodies raised against squid muscle myosin II. Hence, this strategy provides an approach to the identification of a myosin associated with motile axoplasmic organelles.     

Crops that stay green1

Genetic variation exists for foliar senescence and has, usually incidentally or empirically, been exploited for crop improvement. We review the incidence of delayed or inoperative senescence in maize, sorghum, oats, rice, wheat, fescue, soybean, french bean, fruit crops, trees and other species. The insights such variants give into the genetic control of leaf senescence, and the practical implications of improved understanding of the stay-green phenomenon are discussed.     

Comparison of the Surface Proteins and Glycoproteins On Erythrocytes of Calves Before and During Infection With Babesia Bovis

The surface proteins and glycoproteins on red cells from normal and Babesia bovis-infected calf blood have been compared. Several radiolabeling probes were used to label specifically external membrane molecules which were then separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and identified by autoradiography or fluorography. No differences were observed among the Coomassie Blue-stained membrane proteins of erythrocytes from individual uninfected calves. Comparison of red cells from these animals also indicated no qualitative differences in the surface proteins with accessible tyrosyl residues labeled by lactoperoxidase-catalyzed radioiodnation, although some quantitative variation in the uptake of radioactivity into particular proteins was observed. the major radioiodinated bands on normal bovine erythrocytes had Mr of 165, 130, 90, and 45 kiloDaltons. However, labeling of surface glycoproteins by the periodate/[³H]NaBH₄ and galactose oxidase (± neuraminidase)/[³H]NaBH₄ methods showed significant differences in the surface proteins of red cells from individual uninfected calves. of 14 animals tested, 5 had major labeled glycoproteins of unique Mr. No changes were observed in radioiodinated surface proteins of total red cell samples from infected calves with 0.5-6% parasitemia. Radioiodination of concentrated infected red cells from the same samples (concentrated by selective hypotonic lysis of uninfected erythrocytes in KC1) resulted in the labeling of 3 new surface proteins, with Mr of 118, 115, and 60 kiloDaltons. the same new ¹²⁵I-labeled bands were identified on infected cells from 3 avirulent strains of B. bovis used in vaccine production. Furthermore, in concentrated infected cells there was very poor radiolabeling of major bands strongly labeled on uninfected cells (Mr 165, 130, and 90 kiloDaltons), suggesting parasite-induced loss of these proteins. Although there were some differences in ³H-labeled surface glycoproteins of red cells from normal and. B. bovis -infected blood, they were restricted to minor labeled bands and were not seen consistently. the labeled surface glycoproteins of concentrated infected cells were very similar to those of the uninfected red blood cells from infected blood.     

Carbonic Anhydrase in the Accessory Boring Organ of the Gastropod, Urosalpinx

Carbonic anhydrase (CA), the enzyme which catalyzes the reactionCO₂+H₂OH₂CO₃, was found in both active and resting accessoryboring organs (ABO) of Urosalpinx, using a modification of theWaldeyer and Häusler (1959) technique in which the tissuesection is floated on the substrate solution. The intense reactivityof this gland exceeded the activity of other pedal tissues ofthis muricid gastropod. The ventral pedal gland of the femalealso exhibited strong activity, but theconcentration in thistissue was not as intense as that observed in the ABO. No discernible differences between the microvilli of restingand boring ABOs were noted after fixation in acetone, formalin,or glutaraldehyde. However, notable nuances in reactivity ofthe pedal structures occurred when the comparative effect offixatives was evaluated. All variations of the immersion technique, as opposed to flotationprocedures, exhibited a strong stain only in the microvilliof active ABOs, and little or no activity in resting ABOs. Thisdifference between active and resting ABOs (immersion techniqueonly) appears to be due to the binding (chelation) of calciumwith subsequent replacement of cobalt (probably as a carbonatecomplex) in the substrate. The markedly greater CA activity in the ABO, relative to othersecretory tissues inthe snail, suggests a vital role for thisenzyme in the process of penetrating shell. Thelow pH of thesecretion from the active ABO during boring indicates that atleast one phase of the boring process is a chemical reactionassociated with production of acid.     

Host-Integrated Development in the Amoebidiales*

SYNOPSIS. Induction of the resistant stage in the Amoebidiales appears to be dependent upon a morphogenetic factor derived from the host animal. This triggering substance is released either at death or ecdysis of the host arthropod. Growth of the epizoon, Amoebidium parasiticum, in both complex and defined media, follows a sporangiospore sporangium pattern. The amoeba-cyst phase, however, was only noted after crushed host material (Cladocera) was added to the axenically grown thalli. Subsequent tests, evaluated with a quantitative assay, indicate that amoebagenesis is influenced by pH, temperature, condition of the protist, and concentration of the active principle. Commercial “dried daphnia” has consistently yielded an active extract. A large number of complex and simple materials has been screened for activity, and only extracts of ground crab show promise as an alternate source. The amoebagenic factor is heat stable, relatively small, and not soluble in ether, acetone or chloroform. Paper chromatography with polar solvent systems yields a single active band, and this is the best evidence that amoebagenesis is induced by a single, rather than a multiple factor. Paramoebidium, the second genus in this obscure order, undergoes amoebagenesis at ecdysis of the host. The possibility that Amoebidium and Paramoebidium are simply different growth forms of the same protist is discussed.