杨树1年生整株苗造林树体控制技术研究

为了论证杨树1年生整株苗造林树体控制技术中最适宜的截干高度以及后期采用何种主干控制技术能使苗木获得较好的生长,本研究采取双因素完全随机试验设计,设置不同截干高度和不同主干控制方式两个因素进行试验.结果表明:1年生整株苗造林树体控制技术的苗木造林平均成活率达97.4％以上,显著高于常规整株苗造林的平均成活率;合理截干高度...     

短轮伐期桉树人工林个体林木特征研究

利用广东高要和广西扶绥两地14个2~10年生桉树林分样地共287株样木,研究短轮伐期桉树人工林个体林木特征指标,并比较现有广西良种桉二元带皮和去皮材积公式估算个体林木材积的准确性,分析不同年龄、林分和径阶林木的出材率。结果表明:带皮和去皮林木的胸高形数为0.504±0.004 2和0.529±0.004 4、实验形数为0.410±0.002 4和0.427±0.002 7、形率为0.657±0.003 4和0.690±0.003 6、高径比为1.22±0.017和1.43±0.019。用广西良种桉二元带皮和去皮材积公式估算单株林木带皮和去皮材积与实际材积高度相关(r>0.99),但估算值普遍偏低,平均分别小3.7%和21.0%;尤以用带皮材积公式估算去皮材积比用去皮材积公式估计要准确,平均只小2.3%。如以6年生以上样地和尾径4 cm以上的去皮林木为实际出材,5个相关样地林分平均出材率为(73.3±4.31)%,最小为54.6%,最大为81.5%。     

油松侧枝的节间特征及其变异规律

【目的】为阐明油松侧枝的节间特征及其变异规律,了解当年生节间枝条和针叶的异速生长关系,揭示侧枝空间构型、活力和光合产物分配的主要影响因子。【方法】本研究在35 a生油松林内选取了5株标准木的标准枝,通过枝条解析截取了372个节间,采用统计分析和模型模拟等方法对相关问题进行了研究。【结果】结果表明:油松枝条多分为3级,近90%的节间分布在2级和3级枝,直径生长周期为1~4 a、具有针叶着生和光合功能的节间占节间总数的83%;节间直径和长度均随枝级增加而显著下降,均随节间生长周期(或形成时间)的增加而显著增加,后者在枝级间及枝级内的变异均远高于前者,后者受枝级和着生位置光照环境的影响明显高于前者。全枝70%以上的枝条生物量分布在1级枝节间,80%以上的针叶分布在2级和3级枝节间;1级和2级枝的生物量以枝条为主,3级枝以针叶为主。直径生长周期为1~3 a的节间生物量以叶为主,4 a的以枝条为主,4 a以上的以完全以枝条为主。当年生节间的不同特征变量间均成显著的异速生长关系,而非成比例变化。【结论】节间是侧枝的基本单元,其数量、质量、生长发育及其在不同枝级和形成时间的变异,以及其主要构件的异速生长关系是影响侧枝空间构型、活力和光合产物分配的主要因子。     

基于CRISPR/Cas9技术的水稻miR1866突变体构建

microRNA (miRNA)是长度为18～25个碱基的非编码单链RNA,在植物生长发育过程中起着重要的调节作用.水稻是世界上重要的粮食作物之一,近年来调控水稻生长发育的miRNA不断被发掘,但目前关于miR 1866的研究还比较少.本研究通过构建miR1866的CRISPR/Cas9表达载体,创制miR1866的突...     

不同浓度硝基苯对水稻发芽和秧苗生长发育的影响

试验结果表明,硝基苯浓度达到27倍(0.34 mg/L)以上对水稻发芽产生明显影响,致使芽率下降.不同浓度的硝基苯对不同品种的发芽率影响不显著.随着浓度的增加,同一品种株高基本呈降低趋势,根数、叶片与对照差异显著.     

杨树生长量与滩地高程关系的研究

根据同一滩地、不同高程杨树林一个轮伐期的定位观测,杨树造林保存率和材积生长量均随滩地高程降低、淹水时间增加而减小。东南湖滩地根据其杨树宜林性分为3类:①高位滩地,适于建速生丰产林基地;②中位滩地,可作一般用材林、防浪林、抑螺林的造林;③低位滩地,一般不宜直接用于杨树造林。     

浙南室内水泥池刺参度夏试验

通过自然常温饲育和人工控温(23.6±0.5)℃的降温饲育,研究了3种规格体质量(10、20、50个/kg)刺参于浙江南部海区室内水泥池的度夏。结果表明,常温饲育下,3种规格的刺参体质量均呈负增长,且特定负生长率随着刺参体质量的增加而升高;降温饲育下,10个/kg与20个/kg体质量刺参组呈负增长,而50个/kg体质量刺参组略呈正增长,第30 d与第60 d的特定生长率分别为0.0496%与0.0513%。降温(23.6±0.5)℃饲育能有效提高刺参度夏时的存活率,有效降低刺参的特定负生长率,且刺参体质量越大,有效降低的体质量下降幅度也越大。在浙江南部海区室内水泥池养殖刺参,温度保持在(23.6±0.5)℃时,50个/kg的刺参不夏眠。     

Tailoring codend mesh size to improve the size selectivity of undifferentiated trawl species

Tiger flathead, Neoplatycephalus richardsoni (Castelnau), and sand flathead, Platycephalus bassensis Cuvier, are undifferentiated and managed with a common legal minimum length (LML). The Commonwealth Trawl Sector (CTS) and the Tasmanian Danish‐seine fishery (TDSF) use a minimum codend mesh sizes of 90 and 70 mm, respectively. The codend mesh size should be tailored to the LML, which is based on the length of first maturity of females (M₅₀). This study found the length–girth relationship of N. richardsoni and P. bassensis was not significantly different. Using the covered codend method, these two species had 50% retention lengths (L₅₀) of 294 ± 2 and 307 ± 3 mm, in 70‐mm and 90‐mm codends, respectively. L₅₀ estimates for mesh sizes from this study and others produced a curvilinear relationship: y = 120 ln(x) ? 214, with an r² of 0.8504. The size at maturity (M₅₀) for female N. richardsoni was 337 mm, which is larger than the estimate for female P. bassensis (247 mm). There is a mismatch between the estimates of L_50, the estimates of M₅₀ and the LMLs in each fishery, leading to suboptimal exploitation of female Platycephalus. The model produced in this paper recommends a codend mesh size of 98 mm for both fisheries to exploit Platycephalus species sustainably.     

Growth and mortality of sibling triploid and diploid Sydney rock oysters, Saccostrea glomerata (Gould), in the Camden Haven River

Growth and mortality of sibling triploid and diploid Sydney rock oysters, grown at two tidal heights, three stocking densities and three different sites on the Camden Haven River estuary, were compared. Triploids grew faster than diploids. The majority of the growth rate difference occurred after the oysters reached 2 years of age. By 3.2 years, triploids were 49% heavier than diploids. Oysters grown intertidally were larger than those grown subtidally. Oysters stocked at the lightest density of 2 L per basket grew to a significantly larger size than baskets stocked at 3 or 4 L. Growth rates were significantly different at the three sites. Growth was reduced the further the oysters were from the mouth of the estuary. There was no significant difference in mortality between ploidy level, but there were differences between tidal heights, stocking densities and sites. Intertidal oysters suffered higher mortality than subtidal. Oysters stocked at the highest density had a significantly higher mortality than the lowest density; neither of these was significantly different from the medium density. The site closest to the mouth of the estuary had significantly lower mortality than the middle and upper estuary sites.     

Reforming the European Common Fisheries Policy: a case for capacity and effort controls

I summarize the total allowable catch (TAC) fishery management system, which forms part of the European Common Fisheries Policy (CFP) as complicated, inaccurate and ineffective. Total allowable effort (TAE), i.e. limits on fishing capacity and days‐at‐sea, provides a simpler, readily enforceable control to protect all species affected by a fishery. Fishing capacity of vessels in each region‐gear fleet could be capped through limits on engine power, gear, crew, and fittings, and/or reducing allowances of days‐at‐sea for large, powerful vessels. Two basic, fishery‐dependent indicators are put forward to assess sustainability of a fishery dependably even in the absence of fishery‐independent data. One is socio‐economic, the other is ecological. Fishery working groups within each marine region would recommend a TAE to sustain their fishery while also protecting the most critically affected species or processes. Regional working groups would supervise a consistent approach across the different fisheries in their region. A pan‐European group would set policy, implement external agreements, set rules for trading TAE if necessary and harmonize fishing opportunities across regions. To ease negotiations on TAEs with the fishing industry when an ecosystem needs to recover, I propose compensation payments funded by re‐direction of existing CFP subsidies that promote fishing.