开垦年限对黑土氮初级转化速率和净转化速率的影响

以东北黑土区开垦2 a和开垦30 a的典型旱作土壤为研究对象,采用15N同位素成对标记技术开展室内培养试验,利用数值计算模型(FLUAZ)计算不同开垦年限土壤的氮初级转化速率,以比较不同开垦年限黑土氮初级转化速率和净转化速率的差异,明确开垦年限对黑土氮转化过程的影响。结果表明,与开垦2a土壤相比,开垦30a土壤的有机碳和水溶性有机碳含量显著降低,导致土壤氮初级矿化速率和初级固定速率也显著降低。但开垦30a土壤的初级硝化速率、净硝化速率和净氮矿化速率却显著高于开垦2a土壤。两个开垦年限土壤的初级硝化速率分别为净硝化速率的1.15倍和1.02倍,说明土壤微生物对硝态氮的固定很少。开垦30a土壤的m/i值(氮初级矿化速率与初级固定速率之比)和n/ia值(初级硝化速率与初级铵态氮固定速率之比)均显著大于1,而开垦2 a土壤的m/i值和n/ia值均接近1。表明开垦2 a土壤的氮矿化与固定过程紧密偶联,氮素损失的风险较小,而开垦30 a土壤中氮矿化量超过了固定量,这为硝化作用的进行提供了底物,增加了硝酸盐反硝化和淋溶风险。     

DEM空间尺度对可照时数模拟结果的影响 ——以浙江省仙居县为例

以浙江省仙居县为实验区,基于4种不同空间分辨率DEM提取相关地形因子,结合可照时数分布式模型,利用数字地形分析和空间数据叠置分析等方法,模拟1月和7月4种空间分辨率下的可照时数,并定量分析DEM尺度效应对模拟结果的影响。结果表明：（1）模拟结果的空间异质性随分辨率减小而减小,其平均值逐渐增加,且1月增幅大于7月,最大值随分辨率的变化不大,而最小值差异较大,标准差逐渐减小。（2）受海拔和地形遮蔽影响,平地和山脊处可照时数最多,海拔200-400m区间最少,400-1100m区域可照时数随海拔增加而增加。以10m分辨率结果为参照,30m、90m和900m分辨率下的差值随分辨率减小而增加,海拔<100m处差值最小,700-900m区域差值最大,1月日均多算0.7、1.4和2.9h,7月日均多算0.5、0.9和2.3h。（3）坡度0-55°范围内,可照时数随坡度增加而减少,30m、90m和900m分辨率与10m分辨率的差值随分辨率降低而增加,且最小差值均在<5°区域,最大差值在不同坡度等级,1月日均多算2.1、1.8和1.7h,而7月日均多算0.3、0.6和1.2h。（4）受太阳高度角和方位角影响,可照时数在南坡-北坡间的差异较大,东南-西南坡、东坡-西坡以及东北-西北坡之间差异较小,30m、90m和900m分辨率与10m分辨率的差值随分辨率降低而增加,在偏北坡,1月差值大于7月,最大差值在1月的北坡上,日均多算1.4、2.5和4.8h,在偏南坡上,1月差值小于7月,最大差值在7月的南坡或西南坡上,日均多算0.5、0.9和2.1h。     

交易持续期、交易信息与投资者行为——基于PCD模型的研究

使用PCD模型，通过引入买卖价差、交易量、交易规模、委托指令流等交易信息变量探讨交易信息对投资者行为的影响。实证研究表明，买卖价差与期望交易持续期显著正相关，不支持Easley和O’Hara（1992）的观点。同时大规模的交易能够显著地延长交易持续期，而中等规模的交易能够减小交易持续期，证实了知情交易者的隐藏交易假说。指令流信息中的买卖申报数量也对交易持续期有显著的影响，上期买卖申报数量与本期交易持续期正相关。     

太原地区梨大食心虫转芽转果期观察

从1993～1995年观察结果看，太原地区梨大食心虫转芽期为4月7～24日，处于梨树梨芽膨大期。随气温不断上升，转芽率也递增。转果期为5月23日至6月26日，梨果脱萼期幼虫出现转果。针对发生特点，提出“以转芽期防治为主，转果期防治为辅”的防治策略。     

黄杨绢野螟生物学特性研究

摘要本文阐述了黄杨绢野螟[Diaphania perspectalis(Walker)]在上海地区年发生3代,并以3～4龄幼虫在黄杨木叶片上结苞越冬。翌年3月中下旬开始活动为害;经过2个世代后,第三代幼虫于9月中旬起陆续结茧越冬。同时对该虫的各虫态发育历期、生物学特性等进行了研究,为指导防治提供依据。     

美洲斑潜蝇发育历期和有效积温的研究

研究结果表明，美洲斑潜蝇的卵、幼虫、蛹、成虫的发育起点温度分别为１６．８２，１６．５６，１２．８２，１８．１６℃；有效积温分别为３３．４３，３２．４７，１１５．９５，３９．５０日度。并得出各虫态的发育历期与温度的４个关系式。本资料可用于美洲斑潜蝇的发生期及世代的预测。     

Soil quality variables in organically and conventionally cultivated field sites

This study aimed to answer the following questions (a) which of the soil variables (chemical, biological, enzyme activities and potential metabolic profile based on the Biolog method) could be used as indicators reflecting differences in soil quality between organically and conventionally managed asparagus fields, (b) how the duration of organic management affects these soil variables and (c) in what extent the soil quality in organic fields is comparable to that in hedgerows. The study included four organically cultivated fields which differed in the time they enter organic treatment: 6 years (O6), 5 years (O5), 3 years (O3) and 2 years (O2), the closest to them hedgerow (Ho), a conventionally managed field (CF) and its adjacent hedgerow (Hc). Among the chemical and biological variables, those contributing for most to the discrimination of the organic and conventional fields were mainly microbial biomass C (MBC) and N (MBN) and secondly variables related to N-cycle (NO₃, N organic, rate of N mineralization). MBC and MBN were higher in organic and conventional areas, respectively, reflecting differences in the structure of their microbial communities. The chemical and biological variables did not differ among O3, O5 and O6 fields, while low values of organic N, rate of N mineralization and extractable P was recorded in O2 area. The enzyme activities of amidohydrolases (l-asparaginase,l-glutaminase, urease) and phosphatases (alkaline and acid phosphatase) were by far higher in organic areas than in the conventional one. The activities of amidohydrolases and alkaline phosphatase changed in a similar way, exhibiting higher values in O3 and O5 areas while between the oldest (O6) and the newest (O2) area no differences were recorded. While the suppress of enzyme activities in O2 was related to low inputs due to transition, the negative feedback between supply of N and P and activities in O6 was a possible explanation. The activity of acid phosphatase increased from the newest to oldest organic areas. The potential functional diversity and substrate evenness did not differ among sampling areas. Differences between areas were recorded only in relation to the carbohydrates' consumption. The soil quality of hedgerows seems to be completely different than that of the arable land in terms of all studied variables. Also, significant differences were recorded between the two hedgerows, a fact that could be related to the different management practices applied in the neighboring fields.     

Functional Growth Model for Pod Development in Greengram and Blackgram

Identification of readily measured traits that are associated with higher productivity of field crops is important to breeders. The objective of this study was to find out whether pod filling rate or duration of pod filling greatly decide final pod weight in greengram and blackgram. The effective pod filling duration is only 16 days in both the crops. Pod filling rate is more important than duration of pod development. Richards function is found to more closely fit the data on pod development from anthesis to maturity in both the species.     

处理时间对热改性橡胶木物理力学性能的影响

采用过热蒸汽作为传热介质和保护气体热改性橡胶木,分别于185℃条件下热改性处理2、3、4、5h,于200℃热改性处理1、2、3、4h,主要分析了处理时间对橡胶木热改性材物理力学性能的影响。结果表明:在200℃条件下,处理时间对质量损失率、颜色的影响均较185℃更显著。在两个温度条件下,处理时间对MOE的影响均不显著。在185℃温度条件下,MOR从3h开始即无显著变化;在200℃温度条件下,MOR在前3h内无显著变化,第4h开始显著降低。     

猕猴桃在南京地区开花物候期观察

观察中华和美味猕猴桃优良品种在南京地区开花物候期,为其花期管理和授粉提供理论依据。笔者田间观察记录中华猕猴桃和美味猕猴桃的初花期、盛花期、末花期和坐果期,并统计不同猕猴桃品种的花期长度。结果表明,中华和美味猕猴桃的花期集中在4 月中旬—5 月上旬,‘红阳’的初花期最早,为4 月10 日,‘海沃德’初花期最晚,为5 月3 日,两者相差24 天。并且不同猕猴桃品种的花期长短不一,‘翠玉’的花期最长,为17 天,而‘金魁’的花期最短,仅5 天。中华猕猴桃的初花期比美味猕猴桃早,并且花期比美味猕猴桃长。