混交林的改土效益及其在防止地力衰退上的应用

讨论了人工混交林对林地土壤理化性质、微生物及水土保持等方面的改良和促进作用。针对目前人工纯林地力衰退的问题，提出了混交林可作为防止地力衰退的途径， 并对混交林应用上的有关问题作了探讨。     

Biomass production and carbon sequestration potential in poplar plantations with different management patterns

Biomass production and carbon storage in short-rotation poplar plantations over 10 years were evaluated at the Hanyuan Forestry Farm, Baoying County, China. Experimental treatments applied in a split-plot design included four planting densities (1111, 833, 625 and 500 stems ha(-1)) and three poplar clones (NL-80351, I-69 and I-72). Based on the model of total biomass production developed, total plantation biomass production was significantly different in the plantations. The ranking of the plantation biomass production by planting density was 1111>833 more more than 625>500 stems ha(-1), and by components was stem>root>or=branch>leaf for all plantations. At 10 years, the highest total biomass in the plantation of 1111 stems ha(-1) reached about 146 t ha(-1), which was 5.3%, 11.6% and 24.2% higher than the plantations of 833, 625 and 500 stems ha(-1), respectively. The annual increment of biomass production over 10 years differed significantly among initial planting densities and stand ages (p<0.01), but no significant difference was observed from age 7 to 10. Mean carbon concentration among all biomass components ranged from 42-50%, with the highest carbon concentrations in stems and the lowest in leaves. Over the study period, the dynamic pattern of total plantation carbon storage by planting density was similar to that of total biomass production. At age 10, the highest total plantation carbon storage in the plantation of 1111 stems ha(-1) reached about 72.0 t ha(-1), which was 5.4%, 11.9% and 24.8% higher than in the plantations of 833, 625 and 500 stems ha(-1), respectively. The annual carbon storage increment over 10 years differed significantly among initial planting densities and stand ages (p<0.01), and it showed a pattern similar to the annual biomass production increment of the plantations. The results suggest that biomass production and carbon storage potential were highest for planting densities of 1111 and 833 stems ha(-1) grown over 5- and 6-year cutting cycles, respectively. If 3- or 4-year cutting cycles are used, the planting density should be higher than 1111 stems ha(-1) (e.g., 1667 or 2500 stems ha(-1)). Based on the mean annual carbon storage for the plantation of 625 stems ha(-1), as an estimation, the mean carbon storage in the biomass of poplar plantations (excluding leaves) amounts to 3.75x10(7) t ha(-1)yr(-1) in China.     

植茶年限对土壤水稳性团聚体腐殖质组分特征的影响

退耕植茶是川西低山丘陵区响应退耕还林工程实施的重要措施之一.为了研究茶园土壤团聚体中腐殖质组分的分布特征,反映植茶对土壤质量的影响,选取不同植茶年限（18、25、33、55 a）的老川茶园为研究对象,以邻近撂荒地为对照（CK）,研究植茶对土壤团聚体中富里酸（FA）和胡敏酸（HA）分布的影响.结果表明:①不同植茶年限下,土壤富里酸含量（以质量分数计）在2.97~6.26 g/kg之间,胡敏酸含量在1.24~4.89 g/kg之间;随植茶年限的延长,土壤富里酸、胡敏酸含量先增加后降低,均在植茶25 a时达到最大值.②随着土壤团聚体粒径的减小,富里酸含量逐渐降低,胡敏酸则表现为≥5 mm粒径团聚体高于其他粒径.③土壤胡富比（HA/FA）在0.30~0.88之间,总体表现为≥5 mm和 < 0.25 mm粒径团聚体腐殖化程度较高,植茶25 a时大团聚体数量的增加有利于有机质含量和品质的提高.④逐步回归分析表明,≥5、2~5、0.25~0.5和 < 0.25 mm粒级团聚体中有机碳组分对水稳性团聚体的形成和稳定的影响较大.研究显示,植茶有利于土壤团聚体中腐殖质各组分的积累和腐殖化程度的增强,可增加土壤有机碳的稳定性;植茶25 a时土壤碳汇效应较强,植茶33 a后土壤固碳能力有所下降,可通过改善茶园施肥管理等措施保持茶园土壤的结构和肥力,以实现茶园土壤的可持续利用.      

Potential of Co2 emission reductions by carbonizing biomass waste from industrial tree plantation in South Sumatra,Indonesia

Approximately half of the carbon in trees can be fixed to charcoal by carbonization. Porous charcoal is useful as a soil amendment for crop fields and forests, and also as a water purifying agent. Given these facts, charcoal production should be recognized as one of the most promising CO₂ sequestration methods. A project on biomass utilization and forest conservation is proposed as a Clean Development Mechanism (CDM) project, by incorporating the carbonization of biomass residue and waste from tree plantations and pulp mills, and also the utilization of carbon products in various fields. A feasibility study was conducted with the existing project of an industrial tree plantation and pulp production in Indonesia. If conventional charcoal-making methods are used, a total of 368,000 t yr^-1 of biomass residue and waste could be transformed into charcoal of77,000 t yr^-1, and the carbon emission reductions by the project reaches 62,000t-C yr^-1 (or 230,000 t-CO₂yr^-1) in consideration of the project baseline. This charcoal project could provide jobs for approximately 2,600people. The soil fertility in man-made forests could be maintained by returning charcoal to the original forests. Therefore, the project would be beneficial to the regional economy. In addition, the present charcoal project is expected to give more positive impacts than negative ones, or leakage, beyond the project boundary. This revised version was published online in August 2006 with corrections to the Cover Date.     

Aluminium and fluoride concentrations of three tea varieties growing at Lantau Island,Hong Kong

The present project aims to investigate aluminium (Al) and fluoride (F) contents in teas (Camellia sinensis (L.) O. Kuntze). Three different commercial tea varieties: Assam variety and two China sub-varieties, a large leafed variety and small leafed variety, were collected in two tea gardens of Lantau Island tea plantation of Hong Kong. In general, high concentrations of Al and F were accumulated in the mature leaves (15.3 and of 2.07 g kg^–1 respectively). Among the three varieties, the small leafed variety exhibited the highest Al and F contents followed by the large leafed variety whereas the Assam variety had the lowest Al and F concentrations in its tea bushes. Tea products from a plantation were also analysed and it was noted that black tea had higher Al and F concentrations than green tea. The amount of Al and F released into tea liquor was also tested and the results showed that higher concentrations of Al and F were released into tea liquor under repeated infusion method than continuous infusion method.     

Effects of litter removal on plant species diversity: a case study in tropical Eucalyptus forest ecosystems in South China

The removal of litterfall in the Eucalyptus plantations in South China affected the plant biodiversity in these ecosystems was found based on the field observation and lab analysis.The protection times of species diversity of three Eucalyptus communities were different (Community Ⅰ with no protection,Community Ⅱ with 7-year-protection,Community Ⅲ with 35-year-protection).The total numbers of species in these communities(from Community Ⅰ to Ⅱ to Ⅲ)are 1,6,and 17,respectively.The tesults showed that the protection of litterfall from being taken out of the ecosystem is important and can increase plant species diversity.This study ombined biomass data,the chemical and physical properties of the soil,and the diversity of microbes in the communities.It is concluded that the mechanism of the effects of litter removal on biodiversity includes three factors:removing the suitable habitat of microbe and animal,decreasing the soil mutrient, and changing the special habitat for the germination and growth of invading plants.These results should have important implications for managing these Eucalyptus forest ecosystems in South China.     

桤木混交对杉木人工林大型土壤动物群落的影响

调查了中亚热带会同地区13a生杉木纯林(纯林)和8杉木2桤木混交林(混交林)的大型土壤动物群落，并比较了两个林分在群落结构上的差别．结果表明：砹翅目是两个群落在数量上的优势类群，分别占全部大型土壤动物个体数的52．1％和82．4％．杉木跟桤木混交以后，保留了纯林的大部分属性，各类群在大型土壤动物群落中的地位基本保持不变，双翅目、蜘蛛目、膜翅目仍然是最主要的类群，但这种混交方式改变了一些土壤动物的群落结构参数，多度和丰富度出现上升的趋势，均匀度显著降低．在各类群中，主要以双翅目幼虫的多度和相对多度增加幅度较大，这种变化是降低整个群落均匀度的一个主要原因．图3表2参30     

桉树人工林生态系统养分循环与平衡研究Ⅳ.桉树林间种山毛豆对生态系统养分循环的作用

桉树人工林间种山毛豆，增加了凋落物量和养分归还量，改善了营养元素的生物小循环。在一个轮伐期内山毛豆归还土壤养分的数量如下：氮528.37kg／hm^2，磷28.06kg／hm^2，钾66.20kg／hm^2，钙184.96kg／hm^2，镁57.21kg／hm^2；而同期刚果W5桉归还土壤养分的数量为：氮85.98kg／hm^2，磷3.94kg／hm^2，钾11.80kg/hm^2，钙36.98kg／hm^2，镁18.30kg／hm^2。由于间种山毛豆增加了生态系统的养分收入，减少了水土流失的养分支出，系统的各种养分出现了盈余的状况。     

晋西黄土高原水资源植被承载力分析及对策建议

干旱缺水始终是黄土高原地区林业水资源管理面临的难题. 为了探究造成黄土高原地区林水失衡的主要原因,以2009—2012年晋西黄土高原蔡家川流域油松人工林树干液流量与土壤水分长期连续定位观测数据为基础,采用土壤有效水与单株油松耗水量的比值来衡量该区域水资源植被承载力. 结果表明:①在油松人工林实际密度(1 300株/hm2)下,油松人工林过度耗水是深层土壤干化的主要原因;降水量是决定水资源植被承载力的主要环境因子,降水量越大,油松人工林地的水资源植被承载力就越高. ②根据构建的降水量-水资源植被承载力拟合方程,在当地年均降水量为576 mm条件下,研究区20 a林龄油松人工林地水资源植被承载力为1 084株/hm2,而油松人工林地的实际密度远大于该水资源植被承载力. 在黄土高原地区,人工林密度过高是造成深层土壤干化、植被退化等生态恶化的主要原因. 因此,将人工林密度控制在当地水资源植被承载力范围之内,是减少林地深层土壤水分消耗、调节林地水平衡的重要措施.      

基于森林健康视角的北长山岛人工林生物量

以山东省长岛县北长山岛为研究区,通过现场调查、数学模型和3S技术,分析人工林生物量的总量（全部生物量）、存量（活树生物量）、失量（死树生物量）和存量失量比,并探讨生物量的影响因子.结果显示：（1）北长山岛人工林生物量总量共5.88万t,均值为145.8t/hm²,高于全国和山东省的平均水平;生物量存量共3.79万t,失量共2.09万t,其均值分别为93.9t/hm²和51.9t/hm²,森林健康问题已经成为影响北长山岛人工林生物量的重要因素.（2）随着林分密度的增加,生物量总量和存量呈现先上升后下降的趋势,失量持续上升,存量失量比则不断下降;随着胸径的增大,黑松的存量失量比逐渐减小,刺槐则相反;NDVI与生物量总量、存量和存量失量比呈显著正相关,与失量呈显著负相关.（3）存量失量比与坡向、土壤含水率、全磷和总氮呈显著正相关,与海拔、坡度、含盐量和全钾呈显著负相关,与坡位、pH值和总碳关系不明显.