以木麻黄Casuarina equisetifolia 15个家系品种为材料,利用聚乙二醇6000(PEG-6000)模拟水分胁迫环境,设置三个胁迫强度处理(轻度、中度、重度胁迫),研究受胁迫2月龄木麻黄幼苗丙二醛(MDA)含量、超氧化物歧化酶(SOD)活性、脯氨酸含量的变化.结果表明,经干旱胁迫处理后,各家系幼苗叶片MDA含量随胁迫强度增大而增大,但增幅差异较大;不同干旱胁迫水平下,各家系SOD活性存在一定差异;重度胁迫条件下,除粤杂交家系外,其余家系脯氨酸含量与对照相比均为显著增加.采用主成分分析法进行抗旱性综合评价,表明MDA含量是反映水分胁迫最重要的指标.各指标综合分析结果表明,家系701、莆20、抗3、惠2、南山7和东山2抗旱性能力较好;东山短、601、59、A13抗旱能力一般;千头、粤杂交、抗1、龙4和平5抗旱能力较差.

以尾叶桉(Eucalyptus urophylla)的根作为试验材料,按照1∶6,1∶12,1∶24三种浓度梯度配置水浸提液,通过开展盆栽试验研究不同浓度浸提液对1 a生木荷(Schima superba)和樟树(Cinnamomum camphora)苗木生长的化感效应.结果表明,尾叶桉根的水浸提液对木荷和樟树的地径和苗高生长均无明显影响,但对幼苗的根长生长、茎叶生物量、根系生物量、总生物量和根冠比均具有显著抑制作用.

To study the allelopathy effects of eucalyptus urophylla on photosynthesis characteristics of schima superba and cinnamomum canphora seedlings, three concentrations of root extracts (l:6, l:12 and l:24) were prepared with eucalyptus urophylla and used for pot culture experiment on photosynthetic indexes of two species seedlings. Being treated with the root extracts, the change trends of net photosynthetic rate, transpiration rate and stomatal conductance of schima superba were basically the same. The diurnal variations of intercellular CO2 concentrations for all of the treatments of schima superba showed the basal identical trend. The net photosynthetic rate, transpiration rate and stomatal conductance diurnal variation of cinnamomum canphora seedlings treated with the extraction of root had the same trend line as a double-peak curve with the maximum peak at the same time. The diurnal variation of intercellular CO2 concentrations of the treatments at noon was higher than that in the morning and evening. However, the controls of cinnamomum canphora fluctuated in a small concentration range.

Water conservation forest is a special kind of protection forests. It can conserve water sources, improve hydrologic situation, control flood and peak, regulate regional water circulation, control soil erosion and purify water quality. The development of modern society has caused the increasing demand of water resources and serious deterioration of water environment. Water quality shortage has become a global concern. Meanwhile, the problem of shortage of water resources in China is also growing. Therefore, strengthening the construction of water conservation forest is an effective way to achieve sustainable use of water resources. This paper systematically reviews the present research status of hydrologic and ecological function of water conservation forest in china regarding research methods, tree species selection and the mechanism and function of water conservation.

In this paper,using survey data and other data in 2004 and 2009,we evaluated the ecological sustainability of forest resource in Zhongshan during this 5 years.The study contents includ biodiversity and its protection,forest productivity,forest health and its preservation,forest management activities and the environmental response to it.The results show that the ecological sustainability of forest resources has increased,the total evaluation values were 6.55 in 2004 and 6.64 in 2009.

Fire is an important disturbance factor in many terrestrial ecosystems and plays a key role in shaping many forest systems around the world.Fire influences both above-ground and below-ground nutrient cycles by burning some of the vegetation,litter and duff,and therefore leads to nutrient losses.It can also cause important changes in the physical and chemical properties of forest soils including increased bulk density,and altered physical structure,soil moisture,pH and microbial populations.The degree of severity of the fire is largely dependent on the depth,moisture content and flammability of the forest floor material.During burning,nutrients can be lost to the atmosphere through volatilization and particulate transport.Because of its low volatilization temperature this loss includes most of the N.Fly-ash losses of P and K may be significant,although their volatilization temperatures are often higher.After the fire,nutrients are usually deposited on the soil surface in the form of ash,which may then be lost by wind or water erosion or leached into the soil.Wildfires are an important component of the historic disturbance regime of Pinus massoniana stands in south China,which can lead to important changes in the physical,chemical and biogeochemical properties of the soils under these stands.The effects of a wildfire on soil physical,chemical and biogeochemical properties(0 — 0.20 m) were studied in a field-scale experiment on a P.massoniana stand in Heyuan,Guangdong Province,China.We compared soil bulk density,porosity,capillary water,pH,soil organic matter,N,P,K,microbial populations and enzyme activity in unburned plots and in plots affected by wildfires burned over a 4-yr period,to understand the mechanisms involved in soil degradation in the burned P.massoniana stand.Wildfire significantly increased soil bulk density by 11%;slightly increased capillary porosity by 6%;and significantly decreased non-capillary porosity,total porosity and clay content by 30%,8% and 16%,respectively;whereas the soils' capillary water content decreased by only 5%.Wildfire had no significant effect on soil pH.Lower soil organic matter,N,P and K contents were observed in the wildfire plots compared with the controls,and the wildfires significantly decreased the soil organic matter content,total N,P,and K,alkalized N,available P,and K with values of 43%,29%,23%,36%,43%,20% and 47%,respectively.High temperature and environmental changes resulting from the wildfires affected the soil microbial populations.The bacterial counts were significantly lower,in the wildfire plots whereas numbers of fungi and actinomyces remained unchanged.The wildfires caused a large decrease in urease,acid phosphatase and catalase activities,reducing them by 36%,61% and 19%,respectively.Burning also caused nutrients to be deposited on the soil surface in the form of ash which caused bulk density increases,whereas the size of the microbial populations and their enzyme activity tended to decrease because of the lower organic matter content present.