Ecophysiological controls over the net ecosystem exchange of mountain spruce stand. Comparison of the response in direct vs. diffuse solar radiation

Cloud cover increases the proportion of diffuse radiation reaching the Earth's surface and affects many microclimatic factors such as temperature, vapour pressure deficit and precipitation. We compared the relative efficiencies of canopy photosynthesis to diffuse and direct photosynthetic photon flux density (PPFD) for a Norway spruce forest (25‐year‐old, leaf area index 11 m² m⁻²) during two successive 7‐day periods in August. The comparison was based on the response of net ecosystem exchange (NEE) of CO₂ to PPFD. NEE and stomatal conductance at the canopy level (G_canopy) was estimated from half‐hourly eddy‐covariance measurements of CO₂ and H₂O fluxes. In addition, daily courses of CO₂ assimilation rate (A_N) and stomatal conductance (G_s) at shoot level were measured using a gas‐exchange technique applied to branches of trees. The extent of spectral changes in incident solar radiation was assessed using a spectroradiometer. We found significantly higher NEE (up to 150%) during the cloudy periods compared with the sunny periods at corresponding PPFDs. Prevailing diffuse radiation under the cloudy days resulted in a significantly lower compensation irradiance (by ca. 50% and 70%), while apparent quantum yield was slightly higher (by ca. 7%) at canopy level and significantly higher (by ca. 530%) in sun‐acclimated shoots. The main reasons for these differences appear to be (1) more favourable microclimatic conditions during cloudy periods, (2) stimulation of photochemical reactions and stomatal opening via an increase of blue/red light ratio, and (3) increased penetration of light into the canopy and thus a more equitable distribution of light between leaves. Our analyses identified the most important reason of enhanced NEE under cloudy sky conditions to be the effective penetration of diffuse radiation to lower depths of the canopy. This subsequently led to the significantly higher solar equivalent leaf area compared with the direct radiation. Most of the leaves in such dense canopy are in deep shade, with marginal or negative carbon balances during sunny days. These findings show that the energy of diffuse, compared with direct, solar radiation is used more efficiently in assimilation processes at both leaf and canopy levels.     

Poleward shifts in breeding bird distributions in New York State

Like other regions of the northern hemisphere, the northeastern United States has experienced a general increase in regional temperatures over the past 20 years. Quantifying the ecological implications of these changing temperatures has been severely constrained by a lack of multispecies distributional data by which to compare long-term changes. We used the New York State Breeding Bird Atlas, a statewide survey of 5332 25 km² blocks surveyed in 1980–1985 and 2000–2005, to test several predictions that the birds of New York State are responding to climate change. Our objective was to use an information-theoretic approach to analyze changes in three geographic range characteristics, the center of occurrence, range boundaries, and states of occurrence to address several predictions that the birds of New York State are moving polewards and up in elevation. As expected, we found all bird species ( n =129) included in this analysis showed an average northward range shift in their mean latitude of 3.58 km [ Prob ( H _a|data)=0.87)]. Past studies have found that northern range boundaries are more likely to be influenced by climatic factors than southern range boundaries. Consequently, we predicted that northward shifts would be more evident in northern as opposed to southern range boundaries. We found, however, that the southern range boundaries of northerly birds moved northward by 11.4 km [ n =43, Prob ( H _a|data)=0.92], but this pattern was less evident in northern range boundaries of southerly birds. In addition, we found that bird species demonstrated a general shift downhill in their mean elevation, but demonstrated little change in their elevational boundaries. The repeated pattern of a predicted northward shift in bird ranges in various geographic regions of the world provides compelling evidence that climate change is driving range shifts.     

Inclusion of the Vietnamese endemic genus Grushvitzkya in Brassaiopsis (Araliaceae): evidence from nuclear ribosomal ITS and chloroplast ndhF sequences

The phylogenetic position of the recently described monotypic Vietnamese genus Grushvitzkya is evaluated using nuclear ribosomal ITS and chloroplast ndh F sequence data . Grushvitzkya stellata has often been considered as intermediate between Brassaiopsis and Trevesia , but differs in having a 5-locular ovary rather than a 2- or 6–16-locular ovary, respectively. The molecular data indicate that Grushvitzkya is deeply nested within Brassaiopsis and has a close relationship with B. phanrangensis from central and southern Indochina, and B. stellata from the regions bordering China and Vietnam. The Kimura 2-parameter distances of the ITS sequences between G. stellata and B. phanrangensis and B. stellata are 0.403 and 0.945%, respectively. Furthermore, G. stellata and B. phanrangensis have an identical ndh F sequence profile. Grushvitzkya stellata differs from B. stellata by a single nucleotide in their ndh F sequences. The available evidence is compatible with the hypothesis that Grushvitzkya diverged recently from B. phanrangensis and B. stellata . Although these three closely related species all possess stellate trichomes, G. stellata and B. phanrangensis have highly similar trichome micromorphology, with almost no difference in size, shape and branching pattern, supporting a very close relationship between the two taxa. The higher number of locules in the ovary of Grushvitzkya appears to be a secondary increase despite earlier interpretations that higher numbers are evolutionarily primitive. Grushvitzkya is herein merged with Brassaiopsis ; because the combination B. stellata is occupied, a new name, Brassaiopsis grushvitzkyi , is proposed.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 455–463.     

轮藻植物在澳大利亚的重新发现之探密

澳大利亚轮藻植物研究历史悠久,迄今约有95种被描记。在Wood(1972)对澳大利亚轮藻植物的修订研究中,一些种因为标本遗失或已损坏而未包括在内,其中有的种近年来又被重新发现。本文重点介绍Nitella hookeri A．Br．var．arthroglochin A．Br．,Lychnothamnus barbatus(Meyen)Leonh．和Nitella partita Nordst．的发现过程及其产地生态环境,探讨了季节性湿地对轮藻植物的保护意义。N．hookeri var．arthroglochin早在1854年就发现于澳大利亚,并于1887年再次作为澳大利亚特有物种而被记录,然而从此销声匿迹,直至1989年才再度问世,它重新出现的地点为新南威尔士州高海拔花岗岩风化土壤地区的季节性溪流中。L．barbatus则为R．D．Wood首次发现于1960年,嗣后一再搜寻并无踪迹,直到1996年才于昆士兰东南地区亚热带阵发性溪流中被再次发现。昆士兰中部干旱地区1889年一度见到的N．partita,也是近一百年后才在新南威尔士州西北干旱地区的季节性湿地再次发现。     

Tuberculosis organisms resistant to drugs; the incidence and the rate of relapse among patients

The optimum treatment for cancer of the thyroid depends on (a) the pathological type of tumor present and (b) the stage of the disease.In patients with well-differentiated papillary carcinoma, simple operation is usually adequate. In cases of most other types, more extensive operation, followed by adequate postoperative radiotherapy, is regarded as the treatment of choice. In terms of clinical stage, the primary treatment of most cases classified as Stage I or II should be surgical, and of most cases classified as Stage III or IV, radiological. The five-year survival rate in a series of nonterminal cases treated under such a program was 47 per cent. Persistent treatment of selected inoperable or metastatic lesions may result in unexpectedly long survivals.