长期水陆周期性变化条件下香根草形态性状和生物量分配的可塑性

香根草是能够长期适应三峡水库消落带生境的少数物种之一。虽然国内对香根草的引种栽培和研究已有几十年的历史,但是对香根草在三峡库区消落带长期水陆周期性变化条件下的生态适应对策还知之甚少。为此,以2008年在三峡水库巫山段消落带建立的香根草引种栽培试验示范基地为研究平台,在2016年对海拔166—169 m、169—172 m和172—175 m区段的香根草的形态性状、生物量及其分配特征进行了研究。结果表明：(1)海拔166—169 m香根草的分蘖株数、平均株高、节间数量、节间长度、叶片数/分蘖株、叶片数/丛、叶片长等各指标值均低于海拔169—172 m和海拔172—175 m,海拔166—169 m与其它海拔区段的节间数量差异显著(P<0.05);(2)海拔166—169 m香根草的根系数量最少,但根系长度最长;(3)海拔166—169 m无节间的香根草株数最多,且与海拔172—175 m和海拔169—172 m差异显著(P<0.05);(4)不同海拔区段香根草的总生物量大小表现为海拔172—175 m>海拔169—172 m>海拔166—169 m,且海拔166—...     

Temporal and spatial variation of forest biomass in relation to stand dynamics in a mature,lowland tropical rainforest,Malaysia

To clarify consistency in the size of carbon pool of a lowland tropical rainforest, we calculated changes in above-ground biomass in the Pasoh Forest Reserve, Peninsular Malaysia. We estimated the total above-ground biomass of a mature stand using tree census data obtained in a 6-ha plot every 2years from 1994 to 1998. The total above-ground biomass decreased consistently from 1994 (431Mgha^–1) to 1998 (403Mgha^–1) (1Mg=10³ kg). These are much lower than that in 1973 for a 0.2ha portion of the same area, suggesting that the the total above-ground biomass reduction might have been consistent in recent decades. This trend contrasted with a major trend for neotropical forests. During 1994–1998, the forest gained 23.0 and 0.88Mgha^–1 of the total above-ground biomass by tree growth and recruitment, respectively, and lost 51.9Mgha^–1 by mortality. Overall, the biomass decreased by 28.4Mgha^–1 (i.e. 7.10Mgha^–1·year^–1), which is almost equivalent to losing a 76-cm-diameter living tree per hectare per year. Analysis of positive and negative components of biomass change revealed that deaths of large trees dominated the total above-ground biomass decrease. The forest biomass also varied spatially, with the total above-ground biomass density ranging 212–655Mgha^–1 on a 0.2-ha basis (n= 30 subplots, 1998) and 365–440Mgha^–1 on a 1ha basis. A large decrease of the total above-ground biomass density (>50Mg per ha per 2years) in several 0.2-ha subplots contributed to the overall decrease in the 6-ha total above-ground biomass. In the present study, we discuss the association between forest dynamics and biomass fluctuation, and the implication for carbon cycling in mature forests with emphasis on forest monitoring and assessments of soil and decomposition systems.     

The sugar,biomass and biofuel potential of temperate by tropical maize hybrids

The demand for biofuels has created a market for feedstocks to meet future energy requirements. Temperate × tropical maize (Zea mays L.) hybrids, which combine high biomass and fermentable stalk sugars, have yet to be considered as a biomass feedstock. Our objective was to evaluate biological potential, genetic variability and impact of nitrogen (N) on biomass, stalk sugar, and biofuel potential of temperate × tropical maize (TTM) hybrids. Twelve TTM hybrids, two grain and silage hybrids were grown in 2008, followed in 2009 by seven earshoot‐bagged TTM hybrids. In both years, they were grown with and without supplemental N (202 kg ha^?1) in Champaign, IL. Plants were sampled for total and partitioned biomass, and analyzed for concentration and content of sugar. The TTM hybrids were 40% taller, exhibited later reproductive maturity, greater flowering asynchrony, and remained green longer. All hybrids responded to supplemental N by producing more biomass and grain, a lower percent of biomass partitioned to stalk and leaf, whereas TTM also had a decreased concentration of sugar. Total average biomass yields were 24 Mg ha^?1 for both the TTM and grain hybrids. However, TTM partitioned 50% more biomass to the stalk and produced 50% more sugar, and had less than half the grain of the commercial hybrids, indicating grain production and sugar accumulation are inversely related. When grain formation was prevented by earshoot bagging, TTM hybrids produced, without supplemental N fertilizer, an average of 4024 kg ha^?1 of sugar, which was three‐ to four‐fold greater than the non earshoot‐bagged TTM and ear removed hybrid. Calculated estimates for ethanol production, considering the potential from sugar, stover and grain, indicate TTM can yield nearly the amount of ethanol per hectare as modern grain hybrids, but with a decreased requirement for supplemental fertilizer N.     

Biomass Production and Carbohydrate Content of Arabidopsis thaliana at Atmospheric CO2 Concentrations from 390 to 1680 μl l-1

Abstract: The concentration dependency of the impact of elevated atmospheric CO₂ concentrations on Arabidopsis thaliana L. was studied. Plants were exposed to nearly ambient (390), 560, 810, 1240 and 1680 μl I^-1 CO₂ during the vegetative growth phase for 8 days. Shoot biomass production and dry matter content were increased upon exposure to elevated CO₂. Maximal increase in shoot fresh and dry weight was obtained at 560 μl I^-1 CU₂, which was due to a transient stimulation of the relative growth rate for up to 3 days. The shoot starch content increased with increasing CO₂ concentrations up to two-fold at 1680 μl I^-1 CO₂, whereas the contents of soluble sugars and phenolic compounds were hardly affected by elevated CO₂. The chlorophyll and carotenoid contents were not substantially affected at elevated CO₂ and the chlorophyll a/b ratio remained unaltered. There was no acclimation of photosynthesis at elevated CO₂; the photosynthetic capacity of leaves, which had completely developed at elevated CO₂ was similar to that of leaves developed in ambient air. The possible consequences of an elevated atmospheric CO₂ concentration to Arabidopsis thaliana in its natural habitat is discussed.     

C and N storage in living trees within Finland since 1950s

Living biomass contains 45 to 60% carbon and 0.05 to 3% nitrogen, in dry weight. Like throughout Europe, the amount of living biomass in Finnish forests has increased on average over the last decades, largely because of changes in forest management. The storage of organic C and N in biomass has also increased.Changes in biomass vary between regions. Data were analysed on changes in the last 30–40 years in C and N storage in living trees in Finland, subdivided into 20 regions. Tree biomass increased in 17 regions, and decreased in 3 regions. The storage rate varied between -170 and +480 kg C ha^-1 a^-1, and between –0.5 and +1.2 kg N ha^-1 a^-1.Nitrogen accumulation in trees was less than 15% of atmospheric N deposition in all regions. Although the eventual increase of the nitrogen concentration in tree tissues was omitted, it is not possible that living biomass has been the major sink for atmospheric N deposition to forests. A hypothesis is presented that the main sink is litter layer and organic soil. Carbon can also be accumulating in soils essentially faster than hitherto estimated in analyses of carbon budgets of European forests.Died on September 2, 1994.     

Relationship between soil and biomass chemical properties,herbage yield and sward height in cut and unmanaged mountain hay meadow (Polygono–Trisetion)

Little is known about the effects of either long-term cutting with herbage removal or no management on the nutritional status of Agrostis capillaris and Festuca rubra meadows. We asked how management affected soil and herbage chemical properties, herbage yield and sward height. The experiment with cutting (C) and unmanaged (U) treatments was undertaken from 1999 to 2009 in the Jizera Mts., Czech Republic. Soil and herbage samples were taken from 2003 to 2009.Potassium was the only nutrient for which the soil concentration decreased under the C treatment. Soil K concentration was 175 and 210 mg kg^?1 in the C and U treatments, respectively, in the last year of the experiment. Herbage yield as well as sward height were significantly higher in the unmanaged than in the cutting treatment in all years. Concentrations of P and K in the herbage biomass were lower in the cutting than in the unmanaged treatment, but concentrations of N were lower only in some years. Concentrations of Ca and Mg were not affected by the different treatments. A strong positive relationship between concentration in soil and herbage was recorded only for K.In contrast to K, ten years of contrasting management was too short a period to affect plant-available (Mehlich III) P, Ca and Mg concentrations, but it was long enough to affect herbage chemical properties and yield.     

The production of antimicrobial compounds by British marine algae I. Antibiotic-producing marine algae

Using five species of bacteria as the test organisms, 151 species of British marine algae have been screened for the production of antibiotics. Of these, Asparagopsis armata, Bonnemaisonia asparagoides, Bonnemaisonia hamifera, Chondrus crispus, Dilsea carnosa, Gloiosiphonia capillaris, Sphondylothamnion multifidum, Desmarestia aculeata, Desmarestia ligulata, Laminaria digitata, Dictyopteris membranacea, Dictyota dichotoma, Halidrys siliquosa and most members of the family Rhodomelaceae appear to possess outstanding antibacterial properties. Although the production of antibiotics would appear to be a characteristic of several families, it has not been possible to establish any major correlation between taxonomy and antibiotic production. In the case of two closely related and morphologically similar species, Chondrus crispus and Gigartina stellata, the former possesses considerable degrees of antimicrobial activity whilst the latter exhibits no such activity. The results also indicate that the production of antibiotics by the algae is affected by the season of the year.     

松材线虫侵染的马尾松人工林细根形态及生物量分异特征

中龄林的马尾松受松材线虫侵染后,林木生长、生理生化指标、群落多样性等会发生异质性变化,但是,针对患病林木地下细根的响应尚不清楚。本研究以松材线虫疫区患病马尾松和健康马尾松为研究对象,采用土柱法,分0-15 cm和15-30 cm土层,对细根进行分级研究,定量分析1-5级细根的形态、生物量以及养分元素,探讨松材线虫侵染的马尾松人工林细根形态、生物量以及养分元素的分异特征。结果表明:(1)患病马尾松人工林细根的健康状态与根长密度、生物量呈极显著正相关(P<0.01),低级根(如1级根)患病后,响应会更加强烈。(2)马尾松人工林患病后,细根有效磷、速效钾浓度会显著降低(P<0.05),而全氮、钙浓度会显著升高(P<0.05)。(3)松材线虫病使林分的土壤有机质含量显著高于健康林分(P<0.05),而土壤速效钾含量会显著低于健康林分(P<0.05)。以上结果表明,松材线虫侵染的马尾松人工林会在细根形态、细根养分和土壤养分上会发生特异性响应,揭示了松材线虫病对马尾松人工林地下细根的影响,旨在为松材线虫病防治提供一定参考。