半干旱-亚湿润干旱沙区樟子松根内真菌群落结构和功能时空动态特征

研究揭示呼伦贝尔沙地樟子松天然林和不同引种地(呼伦贝尔沙地、科尔沁沙地和毛乌素沙地)不同林龄(中龄林、近熟林和成熟林)人工林根内真菌群落结构和功能时空动态特征及其对环境变化(气候因子和土壤理化性质)的响应,阐明樟子松根内真菌生态功能及其与林木生长的互作关系.结果表明：(1)樟子松人工林根内真菌多样性指数均显著高于天然林(P<0.05),且毛乌素沙地人工林最高;樟子松根内真菌群落存在明显的地理分布,但林龄影响不存在显著差异(P>0.05).(2)与樟子松人工林相比,天然林外生菌根真菌比例更高(50.49%),主要包括Acephala、小菇属(Mycena)和乳牛肝菌属(Suillus);樟子松天然林主要指示菌种为Acephala,呼伦贝尔沙地人工林为肉齿菌属(Sarcodon),科尔沁沙地人工林为红菇属(Russula)和美口菌属(Calostoma),毛乌素沙地人工林为地孔菌属(Geopora)、Mallocybe和棉革菌属(Tomentella).(3)在樟子松天然林和人工林中,指示菌种主要受到有效氮、有效磷和林龄的影响,而与土壤含水量、 pH值和全氮含量相关的指示菌种数...     

Impact of litter removal on soil characteristics under a Pinus caribaea stand

ABSTRACT

Forest productivity is dependent on soil quality, which in turn is related to litter; yet there is limited understanding of the relationships between litter and soil quality. The effects of litter removal treatment on tree growth and soil properties were examined in a Pinus caribaea stand with the aim of providing an understanding of consequences of litter removal on soil patterns. This knowledge is important for planning appropriate long-term forest management. Three pairs of 30 × 30 m² plots (each pair a control and treatment) were established in the center of a P. caribaea stand in April 2002. The controls were left undisturbed with an intact litter layer, while litter was removed monthly from treated plots. The diameter and height of the P. caribaea decreased and soil quality was degraded over the experimental period in litter-removed (treated) plots. Litter removal also produced a significant increase in soil bulk density at 0–20 and 20–40 cm depths. The capillary porosity, capillary moisture capacity, and natural water content in controls at 0–20 and 20–40 cm depths were significantly greater than treated plots. The non-capillary porosity in controls at the 0–20 cm depth was also significantly higher than treated plots. The organic carbon, total nitrogen (N), total potassium (K) and alkalized N content in each layer, and available P and exchangeable K at 0–20 and 40–60 cm depths in control plots were significantly greater than litter-removed plots. The numbers of bacteria at 0–20 and 40–60 cm depths and of fungi at 20–40 and 40–60 cm depths were higher in control than treated plots. The number of actinomyces and urease, catalase, and acid phosphatase activities in controls at each depth were significantly greater than litter-removed plots.     

云南松林资源动态研究

利用云南省森林资源监测数据对云南松林资源的动态变化进行了研究,结果表明：在1987-2007 年的20 a 间,云南松林资源总体呈增长趋势,尤其是蓄积量在1997-2002 年得益于天然林保护工程,出现了快速上升,5 a 净增20.57%,与此同时,过熟林资源一直处于较低水平,优质可用云南松林资源的数量持续减少,濒临枯竭。云南松林分单位面积蓄积量20 a 间提高了27.05%,而大径组和特大径组林木蓄积所占比例则呈下降趋势,近、成、过熟林的单株材积从每株0.77 m³降至0.22 m³,表明云南松林质量在总体上提高的同时,可用资源数量仍在快速减少,材种结构低质化倾向加剧。云南松林分林龄结构一直呈现出显著的低龄化特征,林龄结构现状迫切要求加强对云南松林的抚育管理,科学开展森林经营。20 a间,云南松林主导利用方向波动较大,难以实现长期经营目标。监测期间,以保护为主导的森林经营政策使云南松林资源得到了休养生息,但仍然存在着粗放经营、经营目标随意调整和对成过熟林资源过度利用等森林经营管理问题,这些因素相互交织,成为云南松林资源数量、林分质量和林龄结构变化的主要原因。     

The effects of Pinus tabuliformis on soil detachment under different influencing factors in the Loess Plateau of China

In situ experiments were undertaken to examine the impacts of Pinus tabuliformis on soil detachment under different influencing factors. Experimental sites with slopes containing vegetation cover, plant roots and bare ground were investigated for slope gradients of 8.7%, 17.6%, 26.8%, 36.4% and 46.6% and flow discharges of 0.25, 0.5, 1.0, 1.5 and 2.0?m³?s^?1. Results from our study provide details on the relationship between soil detachment and both slope gradient and flow discharge. Soil detachment rates increased with an increase in slope and discharge, and discharge was identified to have a stronger influence on soil detachment than slope. In contrast, the combination of litter cover and roots played an important role in reducing soil detachment; detachment rate decreased by about 55% relative to bare slopes; and plant roots had a greater impact on detachment reduction. The presence of vegetation cover can decrease rill erodibility by 83% and increase critical shear stress by 224% compared with bare slopes. These results provide valuable information on the importance of woodland in soil detachment control, and may help to improve vegetation construction in seriously eroded regions of the Loess Plateau.     

思茅松种群的自疏研究

在野外考察的基础上,运用密度变化、相对径级离散度、自疏结局分析等方法对思茅松种群的自疏进行了研究。基于研究结果,认为思茅松纯林的管理应以夫然更新为主、人工抚育间伐为辅。     

哈思山油松树轮宽度对气候要素及几种水分指数的响应分析

A tree-ring width chronology developed from Pinus tabulaeformis tree-rings of Hasi Mountain was employed to analyze responses of tree-ring to different climatic metrics. Correlation analyses between tree-ring chronology and precipitation and temperature suggest that tree growth is both limited by precipitation and temperature, and moisture is the principal limiting factor of tree-ring width. To find a suitable moisture index to be reconstructed, three moisture indices considering precipitation and evaporation even water balance are chosen to be analyzed. The results suggest that the PDSI is an appropriate index as predictor of tree-ring width and can be used to reconstruct in this area.     

Geostatistical analysis on the spatial pattern of Pinus tabulaeformis population at different habitats in the Lingkong Mountain北大核心CSCD

In order to reveal the distribution pattern and spatial correlation of Pinus tabulaeformis population, this research used geostatistical theory and methods to examine the distribution pattern and spatial correlation of P. tabulaeformis population in different habitats of the Lingkong Mountain. The results showed that the semivariograms well fitted the exponential model for P. tabulaeformis populations at the mountain ridge, and the spherical model for those in slow slopes and valley areas. All three populations showed aggregated pattern. The spatial heterogeneity of the habitats of ridge, slow slope and valley was mostly due to the spatial autocorrelation in the ranges of 11.16 m, 9.99 m and 4.74 m, respectively. The populations at the ridges and gentle slopes showed greater sill values and determinant coefficient but lower fractal dimension than the pines in valleys, indicating that the first two habitats are characterized by higher degree of spatial heterogeneity and more significant spatial patterns, which is not found in the valley populations. Therefore the variations in the spatial distribution patterns of P. tabulaeformis populations is likely resulted from both the intrinsic biological characteristics and the environmental factors.     

外生菌根真菌对油松幼苗根际土壤重金属赋存的影响

油松幼苗接种菌根盆栽试验表明,外生菌根真菌对油松根际土壤重金属铜、镉的赋存形态产生显著影响.与普通根际相比,菌根际土壤中交换态铜、镉含量显著下降,而有机结合态含量则显著增加.菌根际土壤重金属形态呈现出由疏松结合态向紧密结合态转化的趋势.接种菌根显著降低根际重金属的生物有效性,缓解重金属对寄主植物的毒害作用.     

岷江上游油松造林密度对油松生长和群落结构的影响

调查了岷江上游 20a龄油松人工林样方 17个(20m×20m),测定了油松生长参数、林下植被的植物物种多样性和盖度,以分析油松生长和群落结构变化的密度效应.结果发现:油松高度生长随密度增大而增加,在密度 2 500~3 500hm-2时达最大,随后下降;胸径生长在 2 200~2 800hm-2时达到最大,随后下降.油松单位面积生物量由低及高,在 3 500~4 000hm-2达到最大,随后稍有下降;而个体平均生物量约在 2 500hm-2时最大.随着油松盖度的上升,灌木层盖度开始下降,林下散射光增加,导致草本层盖度上升,中等密度时 (2 500~3 500hm-2 )油松林乔灌草层次盖度配置较为合理;物种丰富度与油松密度呈显著负相关,但不同密度油松林的物种多样性指数变化无一定规律.因此,如果不以追求生物量最大化为单一目标,中等密度(2 500 ~3 500hm-2 )的油松林具有较好的群落结构配置、较高水平的物种多样性和种群更新能力,符合可持续林业发展的要求. 图 3参 19     

酸沉降和大气污染对华南典型森林生态系统生物量的影响

调查酸沉降和大气污染对华南典型森林生态系统植物生物量的影响。结果发现,环境污染对树木的生长以及森林生物量影响较大。采用树干解析方法研究发现,不管是尾叶桉还是马尾松其树高、胸径和材积连年生长量基本趋势是污染地区样地比清洁区样地低。尾叶桉和马尾松林分中的生物量也是污染区样地比清洁区样地低。污染区样地中尾叶桉和马尾松林分总生物量分别为66.89t·hm-2和77.56t·hm-2,仅分别为清洁区的78.89%和94.49%。环境污染均促进这两个树种根系的生长,而抑制其干材的生长。尾叶桉和马尾松根系生物量占林木层生物量比例:污染区样地分别为65.16%和15.08%;清洁区分别为40.50%和14.48%。此两个树种干材生物量占林木层生物量比例:污染区样地分别为19.87%和57.71%;清洁区分别为38.15%和70.33%。本研究结果将为华南地区森林生态系统的保护提供科学依据。