鹤庆深钻孢粉记录揭示的气候变化与西南季风演化

本文在鹤庆深钻孢粉分析的基础上,把各孢粉类型划分成不同的孢粉生态组,结合孢粉多样性指数,系统重建云南鹤庆地区2.78 Ma以来的占气候演化所经历的8个大的阶段,与西南季风在滇西北地区8次大的变化相对应:即在2.729-2.608Ma和0.118Ma-11.83ka BP期间,气候整体湿润,冬、夏季降水的季节性较强,反映西南季风相对较强盛;1.447-0.342Ma期间,气候整体逐渐变湿,冷暖、干湿变化幅度逐渐变大,气候组合特征逐渐变复杂,反映西南季风逐渐增强,其波动幅度也逐渐变大,并于0.991-0.342Ma期间达到最强盛,其波动幅度也最大;而在2.780-2.729Ma、2.608-1.447Ma和0.342-0.118Ma期间,气候普遍相对温暖干旱,西南季风相对较弱.     

小麦胚性悬浮系与原生质体植株再生

普通小麦(Triticum aestivum)昌乐5号(冬性)胚性悬浮细胞系的组成成分对原生质体再生频率发生影响,此种悬浮系是由混合型愈伤组织建立起来的,建成的悬浮系中含有2—3mm的小愈伤组织和分散好的几十至上百个细胞的细胞团。分别用悬浮系中的小愈伤组织和细胞团分离原生质体进行培养。结果表明．由小愈伤组织来源的原生质体再生植株的频率显著高于由细胞团分离的原生质体的再生频率。培养基中不同成分对原生质体分裂的影响也作丁研究。     

Habitat, diet and food assimilation of Arctic charr under the winter ice in two subarctic lakes

The Arctic charr Salvelinus alpinus populations of the subarctic lakes Takvatn and Fjellfrøsvatn, north Norway, concentrated in the littoral zones (0–15 m) of the lakes during the entire winter (December to May) despite very low temperatures (0·2 and 0·7° C). High prey availability, low predation and competition and comparatively better light under snow and ice in shallow compared with deep water are probable reasons. At ice break in June, all Arctic charr moved to the profundal zone for a brief period, probably in response to the sudden light increase and a profundal resource peak of chironomid pupae. In the summer, the Arctic charr are found in the pelagic, profundal and littoral zones of the lakes. These populations therefore perform regular habitat shifts between the littoral zone in the winter, the profundal zone at ice break and the whole lake in the summer and autumn. The fish fed continuously during winter despite the cold water and the poor light. Amphipods and chironomid larvae dominated the diet. Catch per unit effort, numbers of stomachs with food and food intake rates varied with the subarctic light cycle but were lowest after the winter solstice. The winter assimilation of energy was about equal to the standard metabolism in Takvatn but was higher in Fjellfrøsvatn. The assimilation increased in both lakes under the spring ice in May. The habitat choice, diet and energy assimilation indicate that the Arctic charr is well adapted to the extreme winter conditions of subarctic lakes.     

The Dry Holocene Megathermal in Inner Mongolia

The paleoclimate since 14 kyr BP (¹⁴C age) was reconstructed based on a 16.22-m-long sediment core collected from Lake Yanhaizi, a saline lake located near the northern limit of the East Asian summer monsoon in Inner Mongolia. Coarse sediments were deposited there during a shrinkage phase of the lake when sand dunes reactivated. These sediments have low organic carbon contents but high maturity indices, indicating that they were deposited in an arid environment. By contrast, based on high organic contents and low maturity indices, fine sediments were deposited during periods of high lake stand in a humid environment. It was in general dry between 8.0 and 4.3 kyr BP. The above dry and wet phases are consistent with those recovered from the arid-semiarid transition zone elsewhere, but are unlike the widely perceived humid Holocene Megathermal reported in east China and the newly reconstructed record in the alpine Retreat Lake in Taiwan. The discrepancy may be due to a relative insensitivity to humidity changes in these two areas since they have both been under the total influence of the summer monsoon. On the other hand, much enhanced evaporation over higher monsoon precipitation at Lake Yanhaizi reduces the effective humidity in the warm climate near the northern boundary of the summer monsoon. This also accounts for the fact the high-temperature Holocene Megathermal, as revealed in the Okinawa Trough and the northern South China Sea, is correlated to the dry phases at Lake Yanhaizi. Conversely, the 4-2-kyr BP coldest period in the Holocene corresponds to a wet phase at Lake Yanhaizi.     

Deeper Snow Enhances Winter Respiration from Both Plant-associated and Bulk Soil Carbon Pools in Birch Hummock Tundra

It has only recently become apparent that biological activity during winter in seasonally snow-covered ecosystems may exert a significant influence on biogeochemical cycling and ecosystem function. One-seventh of the global soil carbon pool is stored in the bulk soil component of arctic ecosystems. Consistent climate change predictions of substantial increases in winter air temperatures and snow depths for the Arctic indicate that this region may become a significant net annual source of CO₂ to the atmosphere if its bulk soil carbon is decomposed. We used snow fences to investigate the influence of a moderate increase in snow depth from approximately 0.3 m (ambient) to approximately 1 m on winter carbon dioxide fluxes from mesic birch hummock tundra in northern Canada. We differentiated fluxes derived from the bulk soil and plant-associated carbon pools using an experimental ‘weeding’ manipulation. Increased snow depth enhanced the wintertime carbon flux from both pools, strongly suggesting that respiration from each was sensitive to warmer soil temperatures. Furthermore, deepened snow resulted in cooler and relatively stable soil temperatures during the spring-thaw period, as well as delayed and fewer freeze–thaw cycles. The snow fence treatment increased mean total winter efflux from 27 to 43 g CO₂-C m⁻². Because total 2004 growing season net ecosystem exchange for this site is estimated at 29–37 g CO₂-C m⁻², our results strongly suggest that a moderate increase in snow depth can enhance winter respiration sufficiently to switch the ecosystem annual net carbon exchange from a sink to source, resulting in net CO₂ release to the atmosphere.     

Effects of body mass,temperature, and season on resting metabolism of the nocturnal gecko Hemidactylus flaviviridis

Abstract

The resting metabolic rate (RMR) of Hemidactylus flaviviridis was measured at different temperatures from 20 to 35°C during winter and summer acclimatization. The mass exponent b values ranged between 0.67 and 0.72. Winter-acclimatized geckos of various body masses had significantly lower RMRs than summer-acclimatized geckos only at 20°C. It seems that low thermal sensitivity for summer–acclimatized group may facilitate activity during its active seasons, and high thermal sensitivity between 20 and 25°C for winter–acclimatized group may conserve energy during inactivity in winter.     

不同带长微喷带灌溉对土壤水分布与冬小麦耗水特性及产量的影响

于2010—2012年度冬小麦生长季,选用高产冬小麦品种济麦22,采用测墒补灌方式,设置40m(T40)、60m(T60)和80m(T80)3种带长的微喷带灌溉处理,研究不同带长微喷带灌溉对土壤水分分布及冬小麦耗水特性和产量的影响.结果表明:拔节期和开花期采用微喷带补灌,随微喷带带长缩短,灌溉水在土壤中的水平分布均匀系数显著增加.拔节期补灌,T40和T60处理在距畦首0～40m范围内各小麦行间的0～200cm土层土壤含水量均无显著差异;T80处理在距畦首38～40m、58～60m和78～80m处各小麦行间的0～200cm各土层土壤含水量变化规律一致,均表现为随距微喷带的距离增加而减小.T40处理的小麦在拔节至开花期间和开花至成熟期间分别对40～60cm和20～80cm土层土壤贮水的消耗量显著高于T60和T80处理,而对深层土壤贮水消耗量和总土壤贮水消耗量、开花期补灌水量、总灌水量和总耗水量显著低于T60和T80处理.随微喷带带长缩短,小麦籽粒产量、产量水分利用效率显著升高,而流量降低,在灌水量一定的情况下,单位时间内的有效灌溉面积减小.综合考虑小麦籽粒产量、水分利用效率和流量,40和60m是本试验条件下的适宜微喷带带长.     

Winter down-regulation of intrinsic photosynthetic capacity coupled with up-regulation of Elip-like proteins and persistent energy dissipation in a subalpine forest

Overwintering, sun-exposed and photosynthetically inactive evergreens require powerful photoprotection. The goal of this study was to seasonally characterize photosynthesis and key proteins/components involved in electron transport and photoprotection. Maximal photosystem II (PSII) efficiency and photosynthetic capacity, amounts of zeaxanthin (Z), antheraxanthin (A), pheophytin and proteins (oxygen-evolving 33 kDa protein (OEC), PSII core protein D1 and subunit S (PsbS) protein, and members of the early light-inducible protein (Elip) family) were assessed in five conifer species at high altitude and in ponderosa pine (Pinus ponderosa) at moderate altitude during summer and winter. Relative to summer, winter down-regulation of photosynthetic capacity and loss of PSII efficiency at the high-altitude sites were paralleled by decreases in OEC, D1, and pheophytin; massive nocturnal retention of (Z + A) and up-regulation of two to four proteins cross-reactive with anti-Elip antibodies; and no change in PsbS amount. By contrast, ponderosa pine at moderate altitude exhibited no down-regulation of photosynthetic capacity, smaller depressions in PSII efficiency, and less up-regulation of Elip family members. These results support a function for members of the Elip family in the acclimation of sun-exposed needles that down-regulate photosynthesis during winter. A possible role in sustained photoprotection is considered.     

不同土壤肥力条件下施氮量对小麦氮肥利用和土壤硝态氮含量的影响

在土壤肥力不同的两块高产田上,利用15N示踪技术,研究了高产条件下施氮量对冬小麦氮肥吸收利用、籽粒产量和品质的影响,及小麦生育期间土壤硝态氮含量的变化.结果表明：1.成熟期小麦植株积累的氮素73.32%～87.27%来自土壤,4.51%～9.40%来自基施氮肥,8.22%～17.28%来自追施氮肥;随施氮量增加,植株吸收的土壤氮量减少,吸收的肥料氮量和氮肥在土壤中的残留量显著增加,小麦对肥料氮的吸收率显著降低;小麦对基施氮肥的吸收量、吸收率和基施氮肥在土壤中的残留量、残留率均显著小于追施氮肥,基施氮肥的损失量和损失率显著大于追施氮肥;较高土壤肥力条件下,植株吸收更多的土壤氮素,吸收的肥料氮量较少,土壤中残留的肥料氮量和肥料氮的损失量较高,不同地块肥料氮吸收、残留和损失的差异主要表现在基施氮肥上.2.当施氮量为105 kg/hm2时,收获后0～100cm土体内未发现硝态氮大量累积,随施氮量增加,0～100cm土体内硝态氮含量显著增加;施氮量大于195 kg/hm^2时,小麦生育期间硝态氮呈明显的下移趋势,土壤肥力较高地块,硝态氮下移较早,下移层次深.3.随施氮量增加,小麦氮素吸收效率和氮素利用效率降低,适量施氮有利于提高成熟期小麦植株氮素积累量、籽粒产量和蛋白质含量;施氮量过高籽粒产量和蛋白质含量不再显著增加,甚至降低;较高土壤肥力条件下,获得最高籽粒产量和蛋白质含量所需施氮量较低.     

鼎湖山季风常绿阔叶林木本植物个体死亡动态

采用永久样地生物多样性长期监测的方法,在对1hm^2永久样地DBH≥1cm的植物进行4次测定的基础上,研究了鼎湖山季风常绿阔叶林植物个体死亡的动态及其成因,并对不同物种和不同径级植物死亡率的格局差异进行了分析。结果表明,从1992年到2004年,12a内该样地DBH≥1cm的植物共死亡2411株,为该样地现有活立木的69．34％。共有92种木本植物发生了个体死亡,占样地108种木本植物的85．19％,其中乔木70种,灌木22种;年平均死亡株数呈直线上升;死亡涉及木本植物种数也呈上升趋势;样地内种群数量最多的云南银柴（Aporosa yunnanensis）和柏拉木（Blastus cochinchinensis）死亡株数也最多（分别为445株和440株）,分别占所有死亡株数的18．46％、18．25％;优势树种黄果厚壳桂由于受虫害的影响,种群死亡率达90．83％;小径级树木死亡较多,其中DBH≤5cm死亡株数占样地死亡总株数的79．22％。自疏作用、灾害性天气、虫害和人为干扰直接影响到样地内植物个体的死亡动态。