干旱荒漠区人工梭梭林土壤碳氮磷密度与生态化学计量特征

为了阐明人工梭梭林土壤碳氮磷密度及其生态化学计量特征演变规律,以吉兰泰荒漠区不同林龄(3,6,11,16年)人工梭梭林为研究对象,分析0—20,20—40,40—60 cm土层土壤有机碳(SOC)、全氮(TN)、全磷(TP)密度和生态化学计量特征。结果表明:(1)4种林龄人工梭梭林0—60 cm土层SOC、TN含量及其密度随林龄增加而升高,而TP含量及其密度随林龄增加而降低。其中,3,6年梭梭林SOC、TN含量及其密度随土层深度增加而升高,TP含量及其密度则与之相反;11,16年梭梭林SOC、TN、TP含量及其密度随土层深度增加而降低。(2)4种林龄梭梭林土壤C∶N、C∶P、N∶P分别为2.24~9.21,1.59~7.05,0.56~0.81,均属于中等变异水平,且变异系数随林龄和土层深度增加逐渐减小,说明土壤C∶N、C∶P、N∶P趋于平稳状态。(3)林龄、土层深度及其交互作用显著影响SOC含量、SOC密度、C∶N、C∶P,对TN含量、TP含量、TN密度、TP密度、N∶P无显著影响。(4)土壤孔隙度(STP)与SOC密度呈显著正相关关系(P<0.05),说明土壤孔隙度增加有助于SOC密度增加,提高土壤肥力。在干旱荒漠区建植梭梭林有利于提高土壤肥力,改善干旱荒漠区土壤环境。

森林抚育经营对生态效益的影响分析

由于森林对于生态环境及气候具有重大影响,因此,对森林抚育经营的研究具有重要意义。此研究以我国不同范围的森林作为样本,运用对比分析、实地考察以及数学模型等研究方法,对森林抚育经营对生态效益的影响进行了深入研究。研究发现,合理有效的森林抚育经营方法能明显改善森林结构,极大提高森林对二氧化碳的吸收能力与土壤养分密度,同时也能增加生物多样性。相对于传统森林经营模式,森林抚育经营在森林生态效益上提升了25%,且经济效益也有显著的增长。研究结果进一步证明了森林抚育经营的重要性,为我国未来森林管理提供了有力的依据和参考。同时,该研究对于全球森林保护和气候变化的研究具有积极的推动作用。

A Study of the Distribution and Accumulation of Major Nutrient Elements in Different Densities of Eucalyptus grandis

This study was conducted to investigate the distribution and accumulation of major elements of 5-year-old Eucalyptus grandis forests with the densities of 556 trees/hm2 and 1 667 trees/hm2. The results showed that： （1） The distribution of ma- jor nutrient element contents in various organs of the E. grandis with the 2 densi- ties was nearly the same, and the ranked order was leaf〉tree trunk〉branch or branchlet〉fruit〉bark. （2） From the distribution of nutrient elements and organic mat- ter in the trunk, P, K, Mg and Ca contents presented basically a trend of increasing with the trunk height increasing. And the organic matter content increased with the trunk height increasing in the low density stand, while the result was opposite in the high density stand. Furthermore, N content increased with the trunk height increas- ing in the low density stand, but the content in the high density stand exhibited a trend of decreasing at first, increasing then and increasing at the last. （3） From the distribution of biomass, the ranked order was tree trunk〉bark or branch〉branchlet〉 leaf〉fruit. And （4） The accumulated amounts of major nutrient elements in various organs under the 2 stand densities was nearly same. Ca content was the highest in the 2 kinds of plantations, followed by N, K, Mg and P contents. Ca content was 601.78 kg/hm2 in the low density stand and 1 204. 43 kg/hm2 in the high density stand.

Effect of Stem Density on Leaf Nutrient Dynamics and Nutrient Use Efficiency of Dwarf Bamboo

The monthly dynamics of nitrogen （N） and phosphorus （P） concentrations and stocks in leaves, resorption efficiency, and resorption proficiency as well as leaf-level use efficiency, nutrient productivity, and mean residence time were studied to understand the effect of stem density of dwarf bamboo （Fargesia denudata Yi） on leaf-level N and P use efficiency in three dwarf bamboo stands with different stem densities under bamboo-fir （Picea puvpurea Mast.） forest over one growing period in the Wanglang National Nature Reserve, Sichuan, China. Dwarf bamboo density had little effect on the dynamics pattern of both N and P concentrations, stocks, resorption efficiency, and resorption proficiency, but strongly affected their absolute values and leaf-level use efficiency. Higher density stands stored more nutrients but had lower concentrations. There was a clear difference in the resorption of limiting nutrient （N） and non-limiting nutrient （P） among the stands. Phosphorus resorption efficiency, N resorption proficiency, and P resorption proficiency increased with increase of stem density, but no significant variation of N resorption efficiency was found among the stands. Moreover, the higher density stands used both N and P more efficiently with higher N productivity and higher P mean residence time, respectively. Higher P productivity was found in the lower density stands, but there was no clear variation in the N mean residence time among stands. These suggested that the higher density stands may have more efficient strategies for utilizing nutrients, especially those which are limiting .

Effects of slope aspects on forest compositions, community structures and soil properties in natural temperate forests of Garhwal Himalaya

The present study was undertaken in seven natural forest types of temperate zone （1500 to 3100 m, a.s.l.） of Garhwal Himalaya to understand the effects of slope aspects viz., north-east （NE）, north-west （NW）, south-east （SE） and south-west （SW）, on the forest structure, composition and soil characteristics of each selected forest type. The sample plots in each forest type were laid out by using stratified random approach. The indices i.e., the Importance Value Index, Shannon-Wiener diversity index, Simpson’s concentration of Dominance, Simpson diver-sity index, Pielou equitability and Margalef species richness index were calculated statistically using standard softwares to elucidate the differ-ences in forest structure and composition of forest types on different slope aspects of the sites. The composite soil samples were taken from each forest stand and the physico-chemical properties of the soil i.e., moisture content （MC）, water holding capacity （WHC）, pH, organic carbon （OC）, phosphorus （P）, potassium （K） and available nitrogen （N） were analyzed. The results show that the higher values of total basal cover （74.4 m2·ha-1 in Quercus semecarpifolia forest）, Concentration of dominance （0.85 in Pinus roxburghii forest） and Tree diversity （1.81 in Quercus floribunda forest） in the forests were recorded in the northern aspects. MC （40.8% in Quercus leucotrichophora forest）, WHC （48.9% in Cupressus torulosa forest）, OC （3.8% in Cedrus deodara forest）, P （31.9 kg·ha-1 in Quercus leucotrichophora forest） and N （1.0% in Pinus roxburghii forest） had also higher values in the soils of northern aspects. Consequently the higher productivity of the forests was also noticed on the northern aspects.

Impacts of mariculture practices on the temporal distribution of macrobenthos in Sandu Bay, South China

Sandu Bay is located in the East China Sea and is characterized by high-density fish farming and kelp culture. Despite this, little is known about the impacts of these different mariculture practices on the local environment. We investigated the temporal variation in macrobenthos and environmental conditions at three sites in the bay （fish farming site, kelp culture site, and a control site）. We collected water and sediment samples during nine cruises between May 2009 and February 2010. The density of macrobenthos peaked at the fish farming site in July （655 ind./mE） whereas density did not fluctuate as widely at the other two sites. Biomass varied significantly at both the control and kelp culture sites, but had only a single peak at the fish farming site in June （21.90 g/mE）. The dominant species varied throughout the study period at the control and kelp culture sites, whereas a single terebellid species （Lysilla pacifica） dominated the macrobenthos at the fish farming site. The diversity index H＇ increased at the control site beginning in February then decreased after May, whereas H＇ was low at the other sites in December. The mean dissolved oxygen level was highest at the control site （6.59 mg/L） and lowest at the fish farming site （5.54 mg/L）. DO levels were lowest at all sites in summer （July and August）. The sediment acid volatile sulfide content was higher at the fish farming site （1.46 mg/g dry weight） than those at the kelp culture and control sites （1.22 and 0.14 mg/g, respectively）. Our results suggest that mariculture practices have a clear impact on the benthic environment/ community in Sandu Bay.

长白山原始森林土壤养分及其对土柱置换试验响应

自然垂直带典型温带原始森林土壤养分状况及其对温度升高的响应,对碳估算及森林生态系统管理具有重要意义。研究对比长白山北坡垂直小样带3种典型原始森林土壤养分状况,并将岳桦林（海拔1996 m）采集土柱分别置换到云冷杉林（海拔1350 m）和阔叶红松林（海拔740 m）样地,将云冷杉林采集土柱置换到阔叶红松林样地中进行1年野外模拟增温培养。结果发现,土壤碳、氮、磷含量表现为岳桦林〉阔叶红松林〉云冷杉林,并且0～10 cm〉10～20 cm土层。0～20 cm土壤碳、氮、磷密度表现为阔叶红松林〉岳桦林〉云冷杉林,分别为5.64～12.75、0.24～0.89、0.04～0.14 kg·m^-2。3种林型土壤溶解性有机碳（DOC）差异不显著,经过1年野外土柱置换模拟增温培养后,DOC有增加趋势,土壤溶解性氮明显增加。