Life form spectra in the Hantam-Tanqua-Roggeveld, South Africa

The Hantam-Tanqua-Roggeveld subregion is situated in an area where the Fynbos, Succulent Karoo and Nama Karoo biomes meet. Life form spectra were compiled at a species richness and vegetation cover level in order to determine the affinities of the vegetation of the subregion with respect to its Succulent Karoo, Fynbos and Nama Karoo Biome status. A percentage succulence was also calculated for both species richness and cover. Comparisons of life form spectra and succulence were made across the eight vegetation associations found in the area and across three broad vegetation groups, i.e., Mountain Renosterveld, Winter Rainfall Karoo and Tanqua Karoo. Mountain Renosterveld vegetation was characterised by high chamaephyte, cryptophyte and therophyte species contributions. Compared to the other broad vegetation groups, the Mountain Renosterveld group showed phanerophyte contributions at the vegetation cover level to be highest, but the degree of succulence was low. Winter Rainfall Karoo vegetation was co-dominated by high levels of chamaephyte, cryptophyte and therophyte species with chamaephytes dominating the vegetation cover. Succulent contributions to species richness and cover values were higher than for Mountain Renosterveld vegetation. Tanqua Karoo vegetation was dominated by chamaephyte species or co-dominated by chamaephyte and cryptophyte species with therophyte species contributions lowest of all vegetation groups. Contributions by succulent species to richness and vegetation cover were high in the Tanqua Karoo. Life form spectra of the Mountain Renosterveld associations compared poorly to other sites in the Fynbos Biome. However, the low level of succulence in the Mountain Renosterveld associations also precludes its inclusion into the Succulent Karoo Biome. The large contribution of succulent species at a species and vegetation cover level in Winter Rainfall Karoo and Tanqua Karoo associations confirms that these two groups belong to the Succulent Karoo Biome. Affinities to the Nama Karoo Biome were indicated by the low level of succulence at a vegetation cover level in one of the Winter Rainfall Karoo associations (Roggeveld Karoo).     

7个冬小麦品种灌浆期抗旱性鉴定指标的综合评价

采用7个冬小麦(Triticum aestivum L.)品种,研究了不同水分处理下部分生理指标和部分农艺性状变化,以各单项指标的抗旱系数作为抗旱性衡量指标,利用主成分分析对其抗旱性进行评价,同时将综合评价值(D值)与抗旱指数(DRI)进行相关性分析。结果表明:(1)与对照相比,干旱胁迫后的超氧化物歧化酶(SOD)活性、过氧化氢酶(CAT)活性、相对电导率、丙二醛(MDA)含量、脯氨酸(Pro)含量、可溶性糖含量、胞间CO2浓度(Ci)均有不同程度上升;根系活力、净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、株高、穗下节长度、叶面积、穗长、小穗数和穗粒数均下降;过氧化物酶(POD)活性和可溶性蛋白质含量在各品种间变化趋势不尽一致。(2)通过主成分分析综合评价值(D值),供试品种可分为3类:‘晋麦47’和‘小偃22’属于强抗旱型;‘矮抗58’、‘西农979’和‘西农509’属于中等抗旱型;‘郑麦366’和‘郑麦9023’属于弱抗旱型。(3)两种不同干旱胁迫下综合评价值(D值)与抗旱指数均显著相关(r分别为0.768和0.808,p0.05)。     

河北省冬小麦品种SSR标记遗传多样性分析

利用79对多态性较高的SSR引物,对河北省1997-2007年间审定的冬小麦品种及国家小麦区试抗旱对照品种晋麦47和洛旱2号,共计87个冬小麦品种进行遗传多样性分析。79对SSR引物共检测出175个等位变异位点,每对引物可产生1~6条等位变异位点,平均2.215条。标记位点多态性信息含量(PIC)变幅为0.824~0.998,平均为0.941;有效等位基因数(Ne)变幅为1.644~20.333,平均4.708;香农指数(H’)变幅为0.148~1.102,平均为0.544,说明河北省冬小麦品种SSR遗传多样性较低。品种间遗传相似系数(GS)变幅为0.184~0.899,平均为0.418,其中河农826与石家庄8号间的遗传相似性最高,GS高达0.899,71-3与藁优9618间的遗传相似性最低,GS为0.184。不同育种单位培育的小麦品种平均遗传相似系数存在较大差异。UPGMA遗传相似性聚类表明,石家庄市小麦新品种新技术研究所培育的小麦品种与其他单位品种存在较大的遗传差异。     

Winter diet composition of the golden jackal (Canis aureus L., 1758) in Serbia

The winter diet composition of golden jackals was determined by analysing the stomach contents of 248 specimens collected between December and February 2005–2009 at six localities in Serbia. The average weight of stomach contents was 189.9 ± 137.3 g. At all localities, livestock carcasses were the primary food category (frequency 56.1%, biomass 77.7%). The secondary food category consisted of small mammals taken as live prey (frequency 20.7%, biomass 5.2%). Other food categories were present less frequently (roe deer, wild boar, hare, and birds), and rarely (plant material, dogs, carnivores, lizards, and inedible inorganic material). No statistically significant differences were found in diet between jackals from different localities. The only difference was found between yearlings and adults with regard to the consumed biomass (%B). The analysis of the winter diet of golden jackals in Serbia indicates that the species has opportunistic feeding habits consisting primarily of easily accessible food sources.     

作物光合、蒸腾与水分高效利用的试验研究

通过田间试验,对作物光合、蒸腾、气孔行为及其影响因素进行了研究。结果表明,光合与蒸腾的非线性关系可以用抛物线方程表述,其中光合速率最高时的蒸腾速率为临界值,超出该值即为奢侈蒸腾,干旱处理的临界值较低,通过合适的调控措施,抑制奢侈蒸腾并不影响光合生产,综合分析光合速率、蒸腾速率与气孔导度的关系,气孑L导度大于0．12mol·m^-2·s^-1,实施提高气孔阻力并抑制蒸腾的措施,既节约水分又促进光合作用,增加产量．光合速率基本上随光合有效辐射的增加而提高,并有光饱和点存在,水分条件影响叶片光合作用达到饱和的早晚,干旱处理的光饱和点远远低于湿润处理,强光需要水分充足相耦合,才能充分发挥光能利用率,蒸腾与辐射的线性关系十分显著。从光合有效辐射入手,在光合有效辐射大于1000μmol·m^-2·s^-1时实施措施,既可大大降低蒸腾,又可改善光合,节水增产效果不言而喻。     

气候变化对我国华北地区冬小麦发育和产量的影响

验证作物模型在我国华北冬小麦主产区是否适应的基础上,采用作物模型与气候模式相结合的研究方法,定量化地模拟预测了未来100年气候变化对华北冬小麦生产的影响.结果表明,从2000～2004年,华北地区冬小麦产量的模拟值与实测值的变化趋势基本一致,且生育期和产量变化不大.未来100年内华北地区冬小麦的生长期可能会有所缩短,平均缩短8.4 d;产量也会有不同程度的下降,平均减产10.1％.适当采取应对措施可以有效降低冬小麦的减产趋势.     

黄土旱塬冬小麦返青期断根对根冠比、水分利用及产量的影响

采用适当的农艺措施来影响根系生长以提高作物水分利用效率是节水农业研究的一项重要内容。通过田间试验研究了旱作冬小麦‘长武135’(Triticum aestivum cv. Changwu135)返青期切断部分侧生根对根冠比、水分利用效率及产量的影响。与不断根处理相比,冬小麦切断部分侧根后,极显著地减少了表层的根量,花期时断根和不断根小麦在0~20 cm土层根量分别249.70和307.52 g·m^-2,100 cm以上总根量分别为305.53和368.73 g·m^-2。断根比不断根处理根呼吸速率下降了25.57%。断根也抑制了小麦的群体数量,断根和不断根处理单位面积的穗数分别为590.33和646.33 m^-2,但断根显著增加了千粒重,断根和不断根分别为45.99和41.47 g,收获指数也有一定提高。断根对籽粒产量没有显著影响,但断根后土壤含水量显著增加,水分消耗减少。以生物量计算的水分利用效率和以产量计算的水分利用效率分别提高了32.52%和29.98%。因此,在旱地农业中,通过返青期人工断根措施削减根系降低根系对同化产物的消耗和减少耗水量来达到提高冬小麦水分利用效率的方法,是可行的。但今后还需对断根措施作进一步研究,以期实现产量和水分利用效率的同步提高。     

追施氮肥时期对冬小麦旗叶叶绿素荧光特性的影响

在大田条件下,研究了不同追氮时期对小麦旗叶叶绿素荧光特性、光合速率及籽粒产量的影响.结果表明,拔节期追肥较起身期或挑旗期追肥,改善了小麦旗叶PSⅡ的活性(F_v/F_o)、光化学最大效率(F_v/F_m)、光化学猝灭系数(qP)、实际量子产量(ΦPSⅡ)及光合速率,降低了籽粒灌浆中前期非辐射能量耗散,有利于叶片所吸收的光能较充分地用于光合作用,提高了籽粒灌浆后期非辐射能量的耗散,减缓了叶片光抑制程度和衰老进程.拔节期追肥可显著增加穗粒数和千粒重,提高产量.     

贺兰山保护区冬季岩羊集群特征的初步分析

Group size and composition of blue sheep （Pseudois nayaur) were studied in the Helan Mountains, Ningxia Autonomous Region from November to December 2003. We scanned mountain slopes with binoculars and observed with 20 - 60 x spotting-scope. A total of 310 herds of blue sheep and 1 336 individuals were observed during the study period. Blue sheep were frequently seen in small herds of 2 to 8 individuals, which represent 94.8% of total herds observed. Herds consisting of 9 individuals or more represented 5.2%. The largest herd we observed numbered 51 individuals. Mean group size was 4.2 individuals. Blue sheep herds can be divided into three types: male herds （composed solely of males), female herds (consisting of females with or without juveniles of both sexes), and mixed herds （including adult males, females, and subadults). Among the 310 herds, female herds were counted 150 times (48.4%}, mixed herds 154 times (49.7%), and male berds 6 times (1.9%) . Of 1 336 blue sheep classified by sex and age, adults, subadults and juveniles composed 64.1%, 20.8%, and 15.1% respectively. The female: male ratio of adults was 1:0.73. The ratio of adult females to juveniles was 1:0.56, which is higher than the ratio recorded in spring （ 1:0.43) or summer （ 1:0.44). The results showed that the Helan Mountains State Nature Reserve has succeed in protecting blue sheep.     

Determining environmental covariates which explain genotype environment interaction in winter wheat through probe genotypes and biadditive factorial regression

Genotype-environment interaction has been analyzed in a winter-wheat breeding network using bi-additive factorial regression models. This family of models generalizes both factorial regression and biadditive (or AMMI) models; it fits especially well when abundant external information is available on genotypes and/or environments. Our approach, focused on environmental characterization, was performed with two kinds of covariates: (1) deviations of yield components measured on four probe genotypes and (2) usual indicators of yield-limiting factors. The first step was based on the analysis of a crop diagnosis on four probe genotypes. Difference of kernel number to a threshold number (DKN) and reduction of thousand-kernel weight from a potential value (RTKW) were used to characterize the grain-number formation and the grain-filling periods, respectively. Grain yield was analyzed according to a biadditive factorial regression model using eight environmental covariates (DKN and RTKW measured on each of four probe genotypes). In the second step, the usual indicators of yield-limiting factors were too numerous for the analysis of grain yield. Thus a selection of a subset of environmental covariates was performed on the analysis of DKN and RTKW for the four probe genotypes. Biadditive factorial regression models involved environmental covariates related to each deviation and included environmental main effect, sum of water deficits, an indicator of nitrogen stress, sum of daily radiation, high temperature, pressure of powdery mildew and lodging. The correlations of each environmental covariate to the synthetic variates helped to discard those poorly involved in interaction (with | correlation | <0.3). The grain yield of 12 genotypes was interpreted with the retained covariates using biadditive factorial regression. The models explained about 75% of the interaction sums of squares. In addition, the biadditive factorial regression biplot gave relevant information about the interaction of the genotypes (interaction pattern and sensitivities to environmental covariates) with respect to the environmental covariates and proved to be interesting for such an approach. Received: 8 March 1999 / Accepted: 29 July 1999