杉木优良无性系苗造林的效益估算

未来的林业是无性系林业,优良无性系苗造林能把种源选择,种子园的遗传改进、杂交育种、个体选择等成果择其最优部分加以基因复制、利用,从而获得较高的增产效益。本文介绍了12个杉木优良无性系造林后各因子的遗传力和遗传增益。估算了12个优良无性系造林的效益。     

Impact of Harvest Intensity on Long-Term Base Cation Budgets in Swedish Forest Soils

The effects of harvesting on the long-term mass balances of calcium (Ca), magnesium (Mg) and potassium (K) were evaluated on a regional level in Sweden. A new high-resolution weathering database was used together with estimates of total deposition, losses through harvest and leaching. Estimates were made for pine and spruce separately and for two harvesting intensity scenarios: stem harvesting and whole-tree harvesting. The mass balance calculations showed net losses of Ca and Mg in almost the whole country for both scenarios. The losses were smaller for pine than for spruce. The K balances were mainly positive for pine but negative for spruce. Leaching was a main factor in the mass balances, especially for Ca and Mg. Whole-tree harvesting in spruce forests led to substantially higher net losses of K and Ca than stem harvesting, according to the calculations. In the whole-tree harvesting scenario in spruce forests the estimated yearly net losses of Ca, Mg and K corresponded to at least 5%, 8% and 3% of the pools of exchangeable base cations, respectively, at 25% of the analysed sites. If losses of this magnitude continue the depletion of the pools of Ca, Mg and K may lead to very low base saturation of the soils, possibly accompanied by negative effects on soil fertility, runoff water quality, tree vitality and tree growth within a forest rotation in parts of Sweden. Avoiding whole-tree harvesting can improve the situation substantially for K, but the losses of Ca and Mg will still be significant.     

The hypothesis of hydrochorous dissemination of populations of conifers

A comparative analysis of field observations and experiments on the distance and rate of dispersal of self-sown Scotch pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) progeny has shown that the rate of their hydrochorous dissemination downstream is an order of magnitude higher than the rate of dispersal in upland areas. A hypothesis assigning priority to the role of hydrochory in the expansion of conifer populations to the tundra (periglacial) zone along with climate warming has been formulated and substantiated by comparative isozyme analysis of populations in transects lying along and across rivers.     

我国西南地区氮饱和马尾松林土壤和植物15N自然丰度对长期氮施加的响应

我国快速增长的氮沉降可能造成森林生态系统的氮饱和,进而导致一系列严重的环境后果.为了深入研究氮沉降对我国森林生态系统的影响,进而评价和预测森林生态系统的氮状态,本研究选取我国西南地区典型的马尾松林生态系统,对土壤和植物的15N自然丰度(δ15N)进行了测定,探讨用15N富集因子(εp/s)作为氮状态指标的可行性.对该马尾松林连续7 a施加NH4NO3或Na NO3的控制实验结果表明,长期的高氮输入显著增加了土壤和植物的δ15N.同时,该生态系统对不同形态的氮输入有不同的响应,即在NH+4沉降下δ15N显著高于NO-3沉降下的值.15N富集因子与氮沉降量、净硝化速率和淋溶量均呈显著的正相关关系,特别是本研究与之前研究的所有马尾松林的15N富集因子与氮沉降量之间线性相关,表明15N富集因子可用来表征氮状态.由于在相同氮沉降的情况下,NH+4的效应强于NO-3,建议我国在未来控制氮氧化物排放的同时也应当重视氨的排放控制.     

马尾松苗期体内铝离子存在方式、形态和分布

本文用溶液培养方法研究铝在马尾松幼苗体内的存在方式、形态及其分布。结果表明,①松苗吸收的铝主要积累于根部,只有较少量的铝转移至地上部分;②针叶内铝离子主要以束缚态的方式存在,根内束缚态与自由态的存在比例大致相当;③铝离子在表面自由空间大部分以三价铝离子的形态存在,其中针叶内约占63～85％,根内占41—67％;④铝离子在根组织内的含量以外皮层为最高,中柱最低,呈现为从内向外增多的分布状态.     

铝处理马尾松对高温、低温、干旱和SO2的抗性研究

马尾松在不同浓度铝溶液(0、30、60、120、240、480ppm)中生长两个月后,转移至高温、低温、干旱或SO₂熏气罩中,结果发现,经过铝培养松苗的膜透性显著高于未经过铝培养松苗的膜透性,且铝浓度越大,膜透性越大,表明铝处理马尾松对高温、低温、干旱和SO₂的抵抗性降低.300ppb的SO₂熏气30h后,未经铝培养的松苗没有明显受害症状出现,而经过铝培养的松苗却表现出针叶发黄、叶缘和叶尖出现明显可见伤害斑点等SO₂受害症状,高温、低温和干旱处理的主要症状表现为针叶发黄、萎蔫。