Constraints on physiological function associated with branch architecture and wood density in tropical forest trees   总被引：1，自引：0，他引：1  

Meinzer FC  Campanello PI  Domec JC  Genoveva Gatti M  Goldstein G  Villalobos-Vega R  Woodruff DR 《Tree physiology》2008,28(11):1609-1617

This study examined how leaf and stem functional traits related to gas exchange and water balance scale with two potential proxies for tree hydraulic architecture: the leaf area:sapwood area ratio (A(L):A(S)) and wood density (rho(w)). We studied the upper crowns of individuals of 15 tropical forest tree species at two sites in Panama with contrasting moisture regimes and forest types. Transpiration and maximum photosynthetic electron transport rate (ETR(max)) per unit leaf area declined sharply with increasing A(L):A(S), as did the ratio of ETR(max) to leaf N content, an index of photosynthetic nitrogen-use efficiency. Midday leaf water potential, bulk leaf osmotic potential at zero turgor, branch xylem specific conductivity, leaf-specific conductivity and stem and leaf capacitance all declined with increasing rho(w). At the branch scale, A(L):A(S) and total leaf N content per unit sapwood area increased with rho(w), resulting in a 30% increase in ETR(max) per unit sapwood area with a doubling of rho(w). These compensatory adjustments in A(L):A(S), N allocation and potential photosynthetic capacity at the branch level were insufficient to completely offset the increased carbon costs of producing denser wood, and exacerbated the negative impact of increasing rho(w) on branch hydraulics and leaf water status. The suite of tree functional and architectural traits studied appeared to be constrained by the hydraulic and mechanical consequences of variation in rho(w).  相似文献   

Stem dimensional fluctuation in Jeffrey pine from variation in water storage as influenced by thinning and prescribed fire     

Robert M. Fecko  Roger F. Walker  Wesley B. Frederick  Watkins W. Miller  Dale W. Johnson 《Annals of Forest Science》2008,65(2):201-201

Forest thinning utilizing cut-to-length and whole-tree harvesting systems with subsequent underburning were assessed for their impacts on water storage in the extensible tissues of dominant and codominant trees in an uneven-aged Jeffrey pine (Pinus jeffreyi Grev. & Balf.) stand on the east slope of the Sierra Nevada. Prior to the onset of the third growing season following thinning and the second season after burning, manual band dendrometers were installed at breast height on the selected trees and readings of diurnal fluctuation in stem circumference, an indication of bole water status, were taken monthly for one year. Diameter and relative diameter fluctuation were calculated from the circumference measurements. Overall, thinning had a positive influence on stem water recharge capacity, with the most pronounced effects evident in the latter part of the growing season. During this period, bole contraction in thinned stand portions was 49 to 55% greater than in the unthinned control, suggesting that both a greater volume of stored water was available for transpiration and was transpired in trees of the former treatment. There was no clear evidence that harvesting method affected stem water storage and influences of underburning were also absent entirely. Seasonal effects on diurnal changes in stem diameter were prominent, as the extent to which boles contracted generally increased over the course of the growing season, whereas fluctuations were at a minimum during the colder months. The magnitude of stem dimensional flux was found to be negatively correlated with initial tree DBH in one instance, while negative relationships between the former and live crown length as well as percentage were also revealed, albeit infrequently. Changes in bole size were positively correlated with residual basal area in some cases. These results suggest that improvement in water relations can be realized from density management in a dry site forest type with no apparent compromise of this benefit by broadcast underburning.  相似文献   

Removal of nutrient limitations by long-term fertilization decreases nocturnal water loss in savanna trees     

Scholz FG  Bucci SJ  Goldstein G  Meinzer FC  Franco AC  Miralles-Wilhelm F 《Tree physiology》2007,27(4):551-559

Under certain environmental conditions, nocturnal transpiration can be relatively high in temperate and tropical woody species. We have previously shown that nocturnal sap flow accounts for up to 28% of total daily transpiration in woody species growing in a nutrient-poor Brazilian Cerrado ecosystem. In the present study, we assessed the effect of increased nutrient supply on nocturnal transpiration in three dominant Cerrado tree species to explore the hypothesis that, in nutrient-poor systems, continued transpiration at night may enhance delivery of nutrients to root-absorbing surfaces. We compared nocturnal transpiration of trees growing in unfertilized plots and plots to which nitrogen (N) and phosphorus (P) had been added twice yearly from 1998 to 2005. Three independent indicators of nocturnal transpiration were evaluated: sap flow in terminal branches, stomatal conductance (g(s)), and disequilibrium in water potential between covered and exposed leaves (DeltaPsi(L)). In the unfertilized trees, about 25% of the total daily sap flow occurred at night. Nocturnal sap flow was consistently lower in the N- and P-fertilized trees, significantly so in trees in the N treatment. Similarly, nocturnal g(s) was consistently lower in fertilized trees than in unfertilized trees where it sometimes reached values of 150 mmol m(-2) s(-1) by the end of the dark period. Predawn gs and the percentage of nocturnal sap flow were linearly related. Nocturnal DeltaPsi(L) was significantly greater in the unfertilized trees than in N- and P-fertilized trees. The absolute magnitude of DeltaPsi(L) increased linearly with the percentage of nocturnal sap flow. These results are consistent with the idea that enhancing nutrient uptake by allowing additional transpiration to occur at night when evaporative demand is lower may avoid excessive dehydration associated with increased stomatal opening during the day when evaporative demand is high.  相似文献   

The recombinant BGH controversy in the United States: Toward a new consumption politics of food?     

Frederick H. Buttel 《Agriculture and Human Values》2000,17(1):5-20

The history of the controversy overrecombinant bovine growth hormone (rBGH) is exploredin terms of the issue of the potential robustness ofa consumption-driven ``new' politics of food andagriculture. It is noted that while the dominanthistorical traditions in the social sciences haveserved to discount the autonomous role that consumersand consumption play in modern societies, there hasbeen growing interest in consumption within foodstudies as well as other bodies of scholarship such aspostmodernism, social constructivism, socialcapital/social distinction, and environmentalsociology. A review of the shifting pattern ofdiscourses during the rBGH controversy shows thatconsumption-driven claims and politics played atangible, but relatively minor role. Even so, it issuggested that the rBGH experience along with paralleltrends in food politics (e.g., anti-pesticidecampaigns such as the ``Alar scare,' agribusinessattempts to intimidate opponents through fooddisparagement laws, conditions-of-productionprovisions of the World Trade Organization agreement)could make the consumption/consumer dimension of foodpolitics more important in the future.  相似文献   

New brunswick growers organize a certified seed potato growers” association     

Frederick C. Johnson 《American Journal of Potato Research》1924,1(8):158-158

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Investigation,evaluation, and priority ranking of natural areas     

Frederick R. Gehlbach 《Biological conservation》1975,8(2):79-88

Texas experience suggests that amateur naturalists will be heavily involved in preliminary ecological surveys of natural areas, hence a simple key for identification of community-types is presented. Line intercept transects are suggested for amateur use in providing standardised quantitative data on the physiognomy of natural areas. A scheme for the evaluation of each area utilises the weighted values of climax condition, educational suitability, species significance, community representation, and human impact through multiplicative scoring to give a natural area score. With the weighted values-multiplicative scoring scheme, natural areas are clearly distinguished in priority for acquisition.  相似文献   

Exploring the efficacy of vaccine techniques in juvenile sablefish,Anoplopoma fimbria          下载免费PDF全文

Mary R. Arkoosh  Joseph P. Dietrich  Mary Beth Rew  Wendy Olson  Graham Young  Frederick W. Goetz 《Aquaculture Research》2018,49(1):205-216

Wild sablefish, Anoplopoma fimbria, are a valuable commercial species whose populations are declining. Fortunately, sablefish are excellent species for commercial aquaculture. Sablefish raised under high‐density conditions in the marine environment require the use of efficacious vaccines to control disease. Sablefish impacted by disease in net pens may have poor flesh quality and high mortality during grow‐out. As a result, disease can cause financial hardship for sablefish aquaculture operators. The efficacy of a multivalent vaccine preparation for sablefish, administered either by intraperitoneal (i.p.) injection or by immersion, against atypical and typical Aeromonas salmonicida, the causative agents of atypical and typical furunculosis, respectively, was examined. A. salmonicida can affect sablefish at any age and size. Consequently, an efficacious vaccine that can be appropriately and optimally administered to all life stages is desirable. Sablefish vaccinated by immersion at ~1.5 or ~4.5 g with a whole‐cell multivalent vaccine were not protected against either typical or atypical A. salmonicida. Factors that may have contributed to the ineffectiveness of the immersion vaccine are discussed. By contrast, the relative per cent survival (RPS) or potency of the whole‐cell multivalent vaccine injected i.p. in juvenile sablefish at ~50 g against typical and atypical A. salmonicida was 94.3% and 81.7% respectively. The high RPS values indicated that the vaccine successfully initiated an immune response in sablefish upon a second encounter with the pathogen.  相似文献   

Salmon testes meal as a functional feed additive in fish meal and plant protein‐based diets for rainbow trout (Oncorhynchus mykiss Walbaum) and Nile tilapia (Oreochromis niloticus L.) fry          下载免费PDF全文

Kyeong‐Jun Lee  Samad Rahimnejad  Madison S Powell  Frederick T Barrows  Scott Smiley  Peter J Bechtel  Ronald W Hardy 《Aquaculture Research》2015,46(7):1590-1596

Fishery processing by‐products are a large resource from which to produce fishmeal and other products for a variety of uses. In this study, testes meal (TM) produced from pink salmon processing by‐product was evaluated as a functional ingredient in aquafeeds. Nile tilapia and rainbow trout fry were fed five isonitrogenous and isoenergetic experimental diets for 4 and 9 weeks respectively. Two diets were fishmeal‐based (FM) and three were plant protein‐based (PP). Salmon TM was added to the FM and PP diets at 7% to replace 20% of fishmeal protein (FMTM and PPTM respectively). An additional control diet was prepared in which fishmeal was added to the PP diet to supply an equivalent amount of protein as supplied by TM (PPFM). Inclusion of TM in both the FM‐ and PP‐based diets resulted in higher final body weights, although differences were only significant between rainbow trout fed FM or FMTM diets. Similar differences were calculated for other indices of fish performance, e.g. specific growth rate, feed conversion ratio, protein efficiency ratio and protein retention efficiency. Feed intake was significantly higher for fish fed FMTM compared with FM in rainbow trout. For tilapia, final weights were numerically higher, but not significantly different for fish fed diets containing TM compared with non‐TM diets (FM vs. FMTM; PP vs. PPTM). Performance of trout or tilapia fed the PPFM diet did not increase compared with the PP diet. The results indicate that TM addition to both FM and PP diets increased feed intake and also increased metabolic efficiency, demonstrating that TM can be a functional ingredient in aquafeeds.  相似文献   

Comparison of Prosthetic Materials for Abdominal Wall Reconstruction in the Presence of Contamination and Infection     

GL Brown  JD Richardson  MA Malangoni  GR Tobin  D. Ackerman  HC Polk 《Veterinary surgery : VS》1985,14(4):306-306

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Excision of melanomas in horses     

D Frederick 《Journal of the American Veterinary Medical Association》1990,196(8):1201-1202

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