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.     

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。     

Estimations of the Transparency of the Forest Canopy: Analysis of the Ecological Content

The transparency of the forest canopy of lichen-green moss pine forests was estimated for different numbers of sectors of the celestial hemisphere. The ecological contents of these estimations are discussed. The dominance frequencies of species of the herbaceous-dwarf shrub and moss-lichen layers were analyzed. Based on the results of this analysis, it was concluded that the transparency estimated for the zenith sector alone better reflects the influence of leaf debris and the rainfall interception by the crowns. If the transparency was estimated taking into account all sectors of the celestial hemisphere, the effect of community disturbance increased and the redistribution of rainfall was masked.     

Early responses of soil ammonium and nitrate nitrogen to forest gap harvesting of a Pinus massoniana plantation in the upper reaches of Yangtze River北大核心CSCD

To understand the short-term effects of forest gap by human harvesting on soil available nutrient in Pinus massoniana plantations, the variations of soil ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3-N) concentrations in the gap center and gap edge during growing season were observed in seven gaps of different size (Gl: 100 m2; G2:225 m2; G3:400 m2; G4:625 m2; G5:900 m2; G6:1225 m2; G7:1600 m2) and pure understory of a 39-year-old masson pine plantation in a hilly area of the upper reaches of Yangtze River. The results showed that in the early stage of gap formation, the gap size had significant effect on NH4+-N, the season changes on NP3--N, and the interaction effect of gap size and seasonal variation on NH4+-N and NO3--N. The difference of NH4+-N and NO3--N between the gap center and gap edge was not significant. (I) The NH4+-N content was 4.30-11.99 mg kg-1, and NO3--N content was 2.57-10.81 mg kg-1. There was no obvious difference in NH4+-N and N03--N among gaps of different size in early or late growing seasons, when both increased first and decreased afterwards in the middle of growing season. The gaps of 100∼400 m2 area had a higher content of available nitrogen. (2) The seasonal dynamic differed between NH4+-N and NO3--N, with the former lower in middle growing season whereas the latter higher in the middle growing season but lower in the end of growing season. The soil NH4+-N was higher than NO3- -N in the early and late periods, but lower in the middle period. (3) The soil NH4+-N and NO3--N in parts of gaps were lower than understory in the early and late growing season. (4) Correlation analyses showed that NH4+-N had significant positive correlation with microbial biomass nitrogen (MBN), and NO3--N with soil temperature, MBN and organic matter. But the impact of soil water content on available nitrogen was not significant. These results suggested that soil temperature and microbial activity variation caused by gap harvesting are the main factors affecting soil available nitrogen content of Pinus massoniana plantations.     

Soil physi-chemical properties,biomass and nutrient contents of forest litter in mixed plantations of Eucalyptus grandis and three tree species北大核心CSCD

In the present study, we compared the soil physical and chemical properties, biomass of forest litter and nutrient contents in three-and-half-year plantations of E. grandis mixed with Toona ciliate, Alnus formosana, Sassafras tzumu. The results indicated that mixing T. ciliate and A. formosana with E. grandis mitigated soil acidification. In E. grandis × S. tzumu plantations, the soil bulk density decreased, but the moisture capacity and porosity increased. The mixed plantations of E. grandis × S. tzumu significantly increased the soil total C, N, P and K content, by 64.7%, 41.9%, 28.6% and 7.7%, respectively. The mixed plantations of E. grandis × A. formosana also significantly increased the soil total C, N and P content, by 15.2%, 27.9% and 47.6%, respectively. Compared with the pure plantations, the mixed plantations had significantly lower soil hydrolysis N and higher available P content. Only the E. grandis × A. formosana plantations had higher soil available K content. Compared with that in pure plantations, the biomass of branch litter and leaf litter was significantly higher in E. grandis × A. formosana plantations but significantly lower in E. grandis × A. formosana and E. grandis × A. formosana plantations; the biomass of leaf litter and total biomass of litter of E. grandis × S. tzumu were 9.8% and 9.3% respectively lower. The litter C content in three kinds of mixed forest was significantly lower and the litter N content was significantly higher than that in the pure plantations. Only the mixed plantations of E. grandis × A. formosana plantations would increase the content of litter P. The mixed plantations of E. grandis × S. tzumu would increase the content of litter K. In general, S. tzumu is the optimal tree species to mix with E. grandis, followed by A. formosana, but T. ciliate is unsuitble for mixed plantation with E. grandis.     

北京西山侧柏人工林土壤呼吸组分及其影响因素

采用挖壕法,利用LI-8100土壤CO2通量自动观测系统,确定了北京西山侧柏人工林土壤呼吸中异养呼吸和根系自养呼吸的贡献率及其影响因子,分析了土壤呼吸的日、月际时间尺度的变异特征,并利用经验模型分析了土壤温度、土壤体积含水量对土壤呼吸的影响.结果表明:1土壤呼吸速率、异养呼吸速率的昼夜变化呈现单峰变化趋势,峰值出现在14:00—15:00;月际变化也呈单峰变化趋势,峰值出现在7—8月;观测期内土壤呼吸速率日均值变化范围在0.09~12.16μmol·m-2·s-1,异养呼吸速率日均值变化范围在0.02~10.86μmol·m-2·s-1,年均贡献率为69.59%;自养呼吸速率日均值为0.01~6.79μmol·m-2·s-1,年均贡献率为30.41%.2土壤温度的日、月际变化均呈单峰形曲线变化而土壤体积含水量变化规律不明显;整个观测期间土壤呼吸速率的温度敏感系数Q10为2.91,异养呼吸速率的Q10为3.52.3模型研究表明,相对于土壤温度、土壤体积含水量单因素模型,土壤温度与土壤体积含水量的复合模型对土壤呼吸速率变化解释能力为86.8%,对异养呼吸速率的解释能力为74.4%.该研究为森林生态系统碳收支估测及碳循环提供数据依据.     

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。     

Fractionation and mobility of phosphorus in a sandy forest soil amended with biosolids

Goal, Scope and Background Biosolids, i.e., treated sewage sludge, are commonly used as a fertilizer and amendment to improve soil productivity. Application of biosolids to meet the nitrogen (N) requirements of crops can lead to accumulation of phosphorus (P) in soils, which may result in P loss to water bodies. Since 1996, biosolids have been applied to a Pinus radiata D. Don plantation near Nelson City, New Zealand, in an N-deficient sandy soil. To investigate sustainability of the biosolids application programme, a long-term research trial was established in 1997, and biosolids were applied every three years, at three application rates, including control (no biosolids), standard and high treatments, based on total N loading. The objective of this study was to evaluate the effect of repeated application of biosolids on P mobility in the sandy soil. Materials and Methods Soil samples were collected in August 2004 from the trial site at depths of 0–10, 10–25, 25–50, 50–75, and 75–100 cm. The soil samples were analysed for total P (TP), plant-available P (Olsen P and Mehlich 3 P), and various P fractions (water-soluble, bioavailable, Fe and Al-bound, Ca-bound, and residual) using a sequential P fractionation procedure. Results and Discussion Soil TP and Olsen P in the high biosolids treatment (equivalent to 600 kg N ha⁻¹ applied every three years) had increased significantly (P<0.05) in both 0–10 cm and 10–25 cm layers. Mehlich 3 P in soil of the high treatment had increased significantly only at 0–10 cm. Olsen P appeared to be more sensitive than Mehlich 3 P as an indicator of P movement in a soil profile. Phosphorus fractionation revealed that inorganic P (Al/Fe-bound P and Ca-bound P) and residual P were the main P pools in soil, whereas water-soluble P accounted for approximately 70% of TP in biosolids. Little organic P was found in either the soil or biosolids. Concentrations of water-soluble P, bioavailable inorganic P (NaHCO₃ Pi) and potentially bioavailable inorganic P (NaOH Pi) in both 0–10 and 10–25 cm depths were significantly higher in the high biosolids treatment than in the control. Mass balance calculation indicated that most P applied with biosolids was retained by the top soil (0–25 cm). The standard biosolids treatment (equivalent to 300 kg N ha⁻¹ applied every three years) had no significant effect on concentrations of TP, Mehlich 3 P and Olsen P, and P fractions in soil. Conclusions The results indicate that the soil had the capacity to retain most biosolids-derived P, and there was a minimal risk of P losses via leaching in the medium term in the sandy forest soil because of the repeated biosolids application, particularly at the standard rate. Recommendations and Perspectives Application to low-fertility forest land can be used as an environmentally friendly option for biosolids management. When biosolids are applied at a rate to meet the N requirement of the tree crop, it can take a very long time before the forest soil is saturated with P. However, when a biosolids product contains high concentrations of P and is applied at a high rate, the forest ecosystem may not have the capacity to retain all P applied with biosolids in the long term. ESS-Submission Editor: Dr. Jean-Paul Schwitzguébel jean-paul.schwitzguebel@epfl.ch     

“近自然林业”经营法在杉木人工幼林经营中的应用

从1994年起,将“近自然林业”的经营方式应用于杉木人工林的经营中。5a的试验结果表明：与采用常规方法经营杉木相比无论是平均胸高、平均树高、单位面积蓄积量都有大幅度的增长,且立地条件越差增长的幅度越大。用近自然林业经营法经营杉木人工幼林,土壤肥力也得到了维护和提高,表现在土壤生物活性加强,土壤养分增加,交换性能改善,加速了养分的循环和累积。     

福建省茶园土壤中多环芳烃的分布、来源分析及生态风险评价

利用高效液相色谱分析技术对福建省茶园土壤中16种多环芳烃进行了定量分析,结果表明,PAHs的总量在0.622~812.0μg/kg之间,平均值为48.4μg/kg。其组成以3环的为主,4环次之,主成分分析和PAHs特征参数分析发现,福建省茶园土壤中多环芳烃主要以燃油、木柴和煤燃烧来源为主,部分样点存在油类排放污染。生态风险评价结果显示,福建省茶园土壤中多环芳烃已具有不利生物影响效应。