Long‐term fertilization impacts on corn yields and soil organic matter on a clay‐loam soil in Northeast China

A long‐term fertilization experiment with monoculture corn (Zea mays L.) was established in 1980 on a clay‐loam soil (Black Soil in Chinese Soil Classification and Typic Halpudoll in USDA Soil Taxonomy) at Gongzhuling, Jilin Province, China. The experiment aimed to study the sustainability of grain‐corn production on this soil type with eight different nitrogen (N)‐, phosphorus (P)‐, and potassium (K)–mineral fertilizer combinations and three levels (0, 30, and 60 Mg ha^–1 y^–1) of farmyard manure (FYM). On average, FYM additions produced higher grain yields (7.78 and 8.03 Mg ha^–1) compared to the FYM0 (no farmyard application) treatments (5.67 Mg ha^–1). The application of N fertilizer (solely or in various combinations with P and K) in the FYM0 treatment resulted in substantial grain‐yield increases compared to the FYM0 control treatment (3.56 Mg ha^–1). However, the use of NP or NK did not yield in any significant additional effect on the corn yield compared to the use of N alone. The treatments involving P, K, and PK fertilizers resulted in an average 24% increase in yield over the FYM0 control. Over all FYM treatments, the effect of fertilization on corn yield was NPK > NP = NK = N > PK = P > K = control. Farmyard‐manure additions for 25 y increased soil organic‐matter (SOM) content by 3.8 g kg^–1 (13.6%) in the FYM1 treatments and by 7.8 g kg^–1 (27.8%) in the FYM2 treatments, compared to a 3.2 g kg^–1 decrease (11.4%) in the FYM0 treatments. Overall, the results suggest that mineral fertilizers can maintain high yields, but a combination of mineral fertilizers plus farmyard manure are needed to enhance soil organic‐matter levels in this soil type.     

喀斯特石漠化区不同处理方式下滇柏的生长状况——以贵州省陈家寨为例

通过对陈家寨石漠化区综合治理过程中对比、客土、施肥、保水剂、覆盖、保水剂+覆盖6种不同处理方式下柏树林样地的连续观测,对不同处理方式下柏树的生长状况的总体趋势进行了研究。以2年为周期,通过不同时段4次采样,对柏树的高度、基径2个指标的测量。研究结果表明,各种处理方式下柏树的生长状况都得到了明显的改善和提高,其生长程度为保水剂+覆盖保水剂客土覆盖施肥对比。由此可以看出,通过人为的干扰方式,能够有助于植被的生长,有效缓解石漠化的加剧,从而为该区在石漠化综合治理中提供可借鉴的依据。     

桤柏混交林能量代谢中能量吸收,固定,积累和损耗研究

本文通过桤柏混交林气体交换测定研究了能量代谢基本过程。结果表明：桤柏混交林吸收的太阳辐射能大部分损耗子蒸腾作用中，桤木和柏木用于生长呼吸中损耗的能量最多．其中桤木南面时则用于维持呼吸中损耗能量最多，其能量固定建立在内部节律基础上，柏木能量积累大于桤木．     

Effects of rhizospheres on the community composition of Collembola in a temperate forest

Influence of living roots on the community composition of Collembola was investigated in a coniferous forest of Chamaecyparis obtusa. We conducted a buried pot experiment that constructed two different systems for carbon (C) availability. We used two types of pots with or without a C. obtusa seedling. The former pots were used to make a system with soil including living roots (i.e. a system based on root-derived and litter-derived C), while the latter was equivalent to soil system without living roots (i.e. a system based on litter-derived C). After 8 months, we harvested the pots and examined the collembolan community and environmental factors. The presence of living roots affected collembolan abundance and species-specific responses. These changes could be explained in terms of leaf biomass of the seedlings, indicating a possible linkage between above-ground productivity and collembolan community. Given the possibility that root-derived C is associated with aboveground plant mass, we speculate that collembolan community responds to root-derived C. The three dominant species, which are widespread in Japanese temperate forests, were more abundant in the presence of living roots. Moreover they were positively correlated with leaf biomass in the system with a seedling, again suggesting the fundamental importance of living roots for the organisation of the collembolan community.     

Molecular evidence of the hybrid origins of leyland cypress (×Cupressocyparis leylandii)

Leyland cypress (×Cupressocyparis leylandii) has been regarded as an intergeneric hybrid between Monterey cypress (Cupressus macrocarpa) and Alaska cypress (Chamaecyparis nootkatensis) in the Cupressaceae. Each partial sequence of the 18S-rDNA from nuclear and therbcL from chloroplast DNA genomes was determined using above three species. At the 59th site from the 5′ end of the 152 bp of the determined 18S-rDNA sequence, one base difference was identified between Monterey cypress (T) and Alaska cypress (A). However, Leyland cypress showed either nucleotide A or T at this site. Since nuclear DNA is inherited by biparental mode, this result shows genetic evidence that the nucleic genome of Leyland cypress originates from Monterey cypress and Alaska cypress and that this species is of hybrid origin.     

Effect of Ca on Al-induced activation of antioxidant enzymes in the needles of hinoki cypress (Chamaecyparis obtusa)

The effect of CA(NO₃)₂ on the active oxygen scavenging system in hinoki cypress (Chamaecyparis obtusa) seedlings cultured in a nutrient solution containing aluminum was examined. The hinoki cypress seedlings were transferred to nutrient solutions containing 5 mM AlCl₃ together with various concentrations of Ca(NO₃)₂ in pots containing glass beads and Teflon tips. The growth in height and dry matter allocation to each organ was little influenced over a period of 12 weeks by either Al or the concentration of Ca(NO₃)₂. The activity of superoxide dismutase (SOD) in the needles was stimulated by Al, and the effect of Al was lowered significantly by simultaneous application of 25 mM Ca(NO₃)₂. At week 1, the activity of catalase (CAT) in the needles was increased by Al, but the effect was no longer observed at week 12. The Al concentration in the roots was increased by treatment with Al, whereas the Al concentration in needles was not. These results indicate that rhizospheric Al stress stimulates antioxidative enzyme activities in hinoki cypress needles and the activation of the enzymes is suppressed by addition of Ca. The transmission of Al stress to the needles, which induced a change in the enzyme activity, is not caused by the transfer of the Al ion itself from roots to needles. This work was supported in part by funding from the Japan Science and Technology Corporation, the CREST program 1996–2001, and the Center for Forest Decline Studies.     

不同种植模式核桃品质、产量的比较分析

为研究不同种植模式核桃品质、产量的差异,以单作（核桃纯林上坡B1、核桃纯林下坡B2）与间作（红枣/核桃上坡C1、红枣/核桃下坡C2）2种种植模式的核桃为研究对象,对其品质（单果质量、含水量、出仁率、脂肪含量、脂肪酸组分及其含量、蛋白质含量、氨基酸组分及其含量、还原糖含量）进行比较和产量分析。结果表明,不同种植模式的核桃品质、产量均有较大差异,纯林模式有利于核桃积累水解后还原性糖,而间作模式有利于核桃积累蛋白质。B2处理的核桃出仁率、脂肪含量、脂肪酸含量、氨基酸含量、还原糖含量均较高,而其蛋白质含量较低;同种种植模式,下坡处理的核桃产量显著高于上坡处理的核桃产量。综合考虑各项指标,B2处理的核桃的产量最高、品质较好。     

松柏比德的历史演进

在以儒家为主导的中国文化中，有“比德”之传统，即将价值理念、人格理想等赋予具体的事物。松柏不畏严寒，品性贞刚，天然具备能暗示、象征主体品格内涵的特征，因此成为中国文学中常见的“比德”之象。松柏比德在长期的发展演进中，比德内涵日渐丰富，人格象征逐步完善。在人们的心目中，松柏代表着高洁的人格和坚贞的操守，成为民族理想人格的符号。     

Long‐distance dispersal and its influence on adaptation to host resistance in a heterogeneous landscape

Small propagules like pollen or fungal spores may be dispersed by the wind over distances of hundreds or thousands of kilometres, even though the median dispersal may be only a few metres. Such long‐distance dispersal is a stochastic event which may be exceptionally important in shaping a population. It has been found repeatedly in field studies that subpopulations of wind‐dispersed fungal pathogens virulent on cultivars with newly introduced, effective resistance genes are dominated by one or very few genotypes. The role of propagule dispersal distributions with distinct behaviour at long distances in generating this characteristic population structure was studied by computer simulation of dispersal of clonal organisms in a heterogeneous environment with fields of unselective and selective hosts. Power‐law distributions generated founder events in which new, virulent genotypes rapidly colonized fields of resistant crop varieties and subsequently dominated the pathogen population on both selective and unselective varieties, in agreement with data on rust and powdery mildew fungi. An exponential dispersal function, with extremely rare dispersal over long distances, resulted in slower colonization of resistant varieties by virulent pathogens or even no colonization if the distance between susceptible source and resistant target fields was sufficiently large. The founder events resulting from long‐distance dispersal were highly stochastic and exact quantitative prediction of genotype frequencies will therefore always be difficult.