纤维用亚麻在高寒地区的可种植性及高产技术措施

分析了制约纤维用亚麻 (以下简称为亚麻 )生长的水分、温度、光照、土质等因素 ,提出了它在高寒地区的可种植性及高产技术措施。

表征复合型有机污染场地土壤污染程度的生态指标研究

以江苏吴江某复合型有机污染场地土壤为材料,用盆栽黑麦草出苗率和生长一段时期的生物量作为土壤可种植性的标准,通过对比分析不同污染程度场地土壤过氧化氢酶、脲酶、蔗糖酶、多酚氧化酶活性和小麦发芽指数以筛选可用于复合型有机污染场地土壤污染程度指示的灵敏生态指标。结果表明:土壤多酚氧化酶活性和小麦发芽指数可以灵敏表征该复合型有机污染场地土壤污染的程度,且与土壤可种植性存在显著相关关系,其中多酚氧化酶活性与黑麦草出苗率和生物量的相关系数分别为-0.956和-0.938(n=7);小麦发芽指数与出苗率和生物量的相关系数分别为0.936和0.755(n=7);若以黑麦草发芽率大于80%,出苗率大于50%,生长11d株高大于4cm作为土壤对植物生长无害的标准,则对应的土壤多酚氧化酶活性应小于0.8mg·g-1,小麦发芽指数应大于110%。

Spatial and seasonal variation in soil respiration along a slope in a rubber plantation and a natural forest in Xishuangbanna, Southwest China

Soil respiration is a key component of the global carbon cycle, and even small changes in soil respiration rates could result in significant changes in atmospheric CO_2 levels. The conversion of tropical forests to rubber plantations in SE Asia is increasingly common, and there is a need to understand the impacts of this land-use change on soil respiration in order to revise CO_2 budget calculations. This study focused on the spatial variability of soil respiration along a slope in a natural tropical rainforest and a terraced rubber plantation in Xishuangbanna, Southwest(SW) China. In each land-use type, we inserted 105 collars for soil respiration measurements.Research was conducted over one year in Xishuangbanna during May, June, July and October 2015(wet season) and January and March 2016(dry season). The mean annual soil respiration rate was 30% higher in natural forest than in rubber plantation and mean fluxes in the wet and dry season were 15.1 and 9.5 Mg C ha^(-1) yr^(-1) in natural forest and 11.7 and 5.7 Mg C ha^(-1) yr^(-1) in rubber plantation. Using a linear mixedeffects model to assess the effect of changes in soil temperature and moisture on soil respiration, we found that soil temperature was the main driver of variation in soil respiration, explaining 48% of its seasonal variation in rubber plantation and 30% in natural forest. After including soil moisture, the model explained 70% of the variation in soil respiration in natural forest and 76% in rubber plantation. In the natural forest slope position had a significant effect on soil respiration, and soil temperature and soil moisture gradients only partly explained this correlation. In contrast, soil respiration in rubber plantation was not affected by slope position, which may be due to the terrace structure that resulted in more homogeneous environmental conditions along the slope. Further research is needed to determine whether or not these findings hold true at a landscape level.

Effects of Fertilization Types and Cultivation Years on Dissolved Organic Carbon(DOC) in Paddy Soil under Water-logging Condition

In this study, the spatial and temporal distribution characteristics of dis- solved organic carbon （DOC） in water-logged paddy soil in Yanbian were investigat- ed under conditions of different fertilization types （single application of chemical fer- tilizer, mixed application and chemical and organic fertilizers and single application of organic fertilizer） and cultivation years （80 years and 120 years）. The results showed that the spatial and temporal distribution of DOC in water-logged paddy soil changed significantly with time going by. The single application of chemical fertilizer or mixed application of chemical and organic fertilizers contributed to the release of DOC in top paddy soil under water-logging condition; the single application of organ- ic fertilizer promoted the accumulation of DOC in bottom paddy soil, resulting in great heterogeneity of DOC in the vertical space, but the single application of chem- ical fertilizer weakened the vertical spatial heterogeneity of soil DOC; the DOC con- tent in the 80-year-old water-logged paddy soil was higher and more stable than that in the 120-year-old soil.

Maize-rice cropping systems in Bangladesh： Status and research needs

Maize-rice cropping systems are expanding in Bangladesh. Hybrid maize has increasing demand and value, particularly for poultry feed, while rice remains the traditional dominant starch staple food. Bangladesh maize yields （with average farm yields around 5.7 t·ha^-1） are among the highest found in Asia. Cool winter （Rabi） season maize followed by T. Aman （monsoon） rice is the major cropping system; however it is now becoming diversified with many other crops including potato. Financially, hybrid maize is far more profitable than boro （irrigated） rice, wheat, or most other competing winter season Rabi crops. Although maize is relatively problem-free in Bangladesh, some constraints are intensifying with increased concern over input supply and soil-related environmental sustainability. An array of new technologies for sustainable intensive maize production systems is emerging in Bangladesh and some are being promoted and adopted. Continued sustainability of hybrid maize production in Bangladesh depends on optimization of planting time, quality seed of appropriate hybrids, balanced use of nutrient inputs along with soil fertility conservation and other management, for which further research would be high priority.

Spatial Land Evaluation for Oil Palm Cultivation Using GIS （Geographic Information System）

The objective of the study was to establish spatial land evaluation for oil palm cultivation using GIS （geographic information system）. The study area is situated in the KESEDAR region in the state of Kelantan, Malaysia. The evaluation of the land in terms of the suitability classes were based on the method of FAO （Food and Agriculture Oganization of the United Nations）. Five land qualities are important for determining the physical land suitability for oil palm; these are nutrient availability, oxygen availability, water availability, workability and availability of foothold for roots. Each of the above mentioned land qualities with associated attribute data were digitally encoded in a GIS database to create thermatic layers. Overlay operation on the layer produced resultant polygonal layer each of which is a land unit with characteristics of the land. The results from GIS overlay analyses showed that Bungor, Chat, Chempaka, Alluvium, Musang and Tok Yong series are highly suitable while Kawang series is moderately suitable for oil palm cultivation. The same results were obtained by using parametric-limitation method.

Poplar Plantation as an Agroforestry Approach:Economic Benefits and Its Role in Carbon Sequestration in North India

Poplar has gained popularity among farmers of Punjab,Haryana,Western Uttar Pradesh,and the foothills of Uttarakhand and Himachal Pradesh due to their fast growth rate and suitability for industrial uses such as pulp and timber production.Integrating poplar trees into agroforestry systems optimizes land resources and economic gains,as successful techniques have been developed to coordinate crop timing and arrangements effectively.Integrating poplar trees with agricultural crops provides additional income streams for farmers and contributes to soil conservation,biodiversity enhancement,and other environmental benefits.Farmers in these regions typically employ effective spacing of 5 m×4 m for block plantation and 1 m×3 m for row plantation.In the present study,a systematic literature review encompassing 137 English-language journal articles was conducted to assess the economic benefits of Poplar using discounted cash flow(DCF)analysis,considering short-rotation poplar(SRC)and very short-rotation poplar(vSRC)plantations alongside annual crops.The findings revealed that increasing canopy density led to a decline in crop yields by 37%,70%,and 99% at canopy densities of 30%,60%,and 90%,respectively,from early spring to harvest.Cost-benefit analysis in Saharanpur district,India,indicated average annual net returns of USD 346.36 for Poplar-based agrisilviculture,while monoculture yielded USD 140.73 per annum.Furthermore,economic analysis in Yamunanagar and Haridwar districts showed benefit-cost ratios ranging from 2.35 to 3.7.Additionally,Poplar block and boundary plantations were found to sequester significantly more carbon in long-lived biomass,serving as substitutes for fossil fuels(5.45 and 1.84 t ha-1 yr-1)in poplar-based systems with block and boundary plantations.The study suggested expanding spacing between tree rows may mitigate resource competition between plantations and crops.The study inferred that Poplar-based agroforestry may play a crucial role in climate mitigation programs by effectively sequestering atmospheric carbon and offering fuel,fodder,timber,and wood products,thereby alleviating pressure on existing natural forests.