红松人工林生态系统土壤含水率变化规律

于2005年4月,对不同地类、不同土层垂直深度、不同季节的土壤含水率进行了连续3a的定位测定,并探讨了影响土壤含水率的相关因子.结果表明,红松郁闭林分土壤含水率为22.52%,均超过未郁闭的红松纯林和红松-白桦混交林.表层(0～10cm)土壤含水率最高,为22.62%,并呈现出随土壤深度的加深而含水率逐渐减小.在水热同...     

Tropical reptiles in pine forests: Assemblage responses to plantations and plantation management by burning

Worldwide, the land area devoted to timber plantations is expanding rapidly, especially in the tropics, where reptile diversity is high. The impacts of plantation forestry and its management on native species are poorly known, but are important, because plantation management goals often include protecting biodiversity. We examined the impact of pine (Pinus caribaea) plantations, and their management by fire, on the abundance and richness of reptiles, a significant proportion of the native biodiversity in tropical northern Australia, by (i) comparing abundance and diversity of reptiles among pine plantations (on land cleared specifically for plantation establishment), and two adjacent native forest types, eucalypt and Melaleuca woodlands, and (ii) comparing reptile abundance and richness in pine forest burnt one year prior to the study to remove understorey vegetation with pine forest burnt two years prior to the study. We also examined the influence of fire on reptile assemblages in native vegetation, by comparing eucalypt woodland burnt two years prior to the study and unburnt for eight years. To quantify mechanisms driving differences in reptile richness and abundance among forest types and management regimes, we measured forest structure, the temperatures used by reptiles (operative temperature) and solar radiation, at replicate sites in all forest types and management regimes. Compared to native forests, pine forests had taller trees, lower shrub cover in the understorey, more and deeper exotic litter (other than pine), and were cooler and shadier. Reptile assemblages in pine forests were as rich as those in native forests, but pine assemblages were composed mainly of species that typically use closed-canopy rainforest and prefer cooler, shadier habitats. Burning did not appear to influence the assemblage structure of reptiles in native forest, but burning under pine was associated with increased skink abundance and species richness. Burned pine was not warmer or sunnier than unburned pine, a common driver of reptile abundance, so the shift in lizard use after burning may have been driven by structural differences in understorey vegetation, especially amounts of non-native litter, which were reduced by burning. Thus, burning for management under pine increased the abundance and richness of lizard assemblages using pine. Pine plantations do not support the snake diversity common to sclerophyllous native forests, but pine may have the potential to complement rainforest lizard diversity if appropriately managed.     

A lack of large-diameter logs and snags characterises dead wood patterns in Irish forests

Dead wood is an important component of forest ecosystems and volumes vary depending on forest age, management intensity and productivity. This is the first large-scale study to quantify dead wood in Irish forests and to compare them to forests in other locations. We measured the volume and size distribution of logs, the density and size distribution of snags and the volume of dead wood contained in stumps in Oak (Quercus spp.) and Ash (Fraxinus excelsior) forests and in Sitka spruce (Picea sitchensis) plantations throughout Ireland. We also assigned each log, snag and stump to one of three decay classes (intact, part-rotted and well-rotted). We found no significant difference in log volume between any of the forest types. The majority (>90%) of logs were less than 20 cm in diameter, and large logs (>40 cm diameter) were scarce. We found a relatively high density of snags in all forest types but, as in the case of logs, over 90% of snags were <20 cm DBH and large snags (>40 cm DBH) were rare. The volume of dead wood contained in stumps was significantly higher in plantations than in Oak or Ash forests as a result of thinning and harvesting. Most logs and snags were moderately decayed but, in plantations, most stumps were intact. Log volume and the size of logs and snags were considerably lower than in old-growth forests in other regions. These patterns may reflect historical use of Irish forests for coppice and timber production. Management for biodiversity should aim to accelerate dead wood accumulation to increase the frequency of large-diameter logs and snags. Although management seeking to replicate the dead wood volumes of old-growth forests is ideal, it may be unrealistic in the short term.     

A reduced growth model based on stand basal area. A case for hybrid poplar plantations in northeast Spain

Whole-stand models normally require data on initial stand basal area and dominant height. Dominant height measurements are time-consuming and often imprecise, compromising subsequent predictions. Poplar plantations provide a special case where basal area correlates with site index; a whole-stand model could thus be based on stand basal area. We report a static model constructed by the generalized algebraic difference approach (GADA) for poplar plantations for three different hybrid poplars (Populus × euramericana (Dode) Guinier “I-214”, “MC”, and “Luisa Avanzo”) in northeast Spain. The transition function was based on current stand basal area and was fitted with data from 158 permanent plots ranging from 1- to 17-year-old plantations. Merchantable stand volume was estimated by a volume equation where height was predicted by a height–basal area relationship based on 458 temporary plots. The model differences between clones were compared using the nonlinear extra sum of squares method. Significant differences were detected, while Luisa Avanzo presented the highest merchantable volume at the end of the rotation. Errors in basal area predictions were below 20% within 6 years in the case of Luisa Avanzo and MC clones, and within 3 years in the case of I-214. Our research showed that satisfactory predictions can be obtained using GADA with a single transition function based on an easily measurable variable such as stand basal area.     

湘潭锰矿废弃地栾树人工林微量元素生物循环

对湘潭锰矿废弃地5年生栾树人工林内微量元素的含量、积累、空间分布和生物循环进行了研究。结果表明：土壤中各微量元素含量顺序为：Fe>Mn>Zn>Pb>Ni>Cu>Co>Cd,均低于对照地,但仍未低于湖南省背景值(Fe除外)。枯枝落叶层中,仅Mn和Co从半分解到已分解阶段向土壤中转移,其他元素在分解过程中都出现了不同程度的富集,各元素在不同阶段含量没有显著差异,在分解过程中,Mn元素含量最高且与Cu、Pb、Co、Ni、Cd均存在数量级差异。栾树各组分元素含量顺序为：叶>枝>细根>皮>粗根>大根>根头>干,各元素总含量顺序为：Mn>Fe>Zn>Pb> Cu>Cd>Ni>Co;林分微量元素总贮量为15.272kg/hm_-2,其中干和枝贮存量最高,占总贮存量的54.204%。各器官微量元素贮存量顺序为：枝>干>叶>皮>根头>大根>粗根>细根;林分微量元素吸收量为5.200kg/hm₂.a,存留量为2.504kg/hm₂.a,归还量2.751kg/hm₂.a,总利用系数为2.394,循环系数为3.138,周转期为11.203a。栾树对Mn的吸收能力最强,Fe、Ni的返还系数要高于吸收系数,所有元素的分解系数都高于返还系数。Fe、Mn的迁移系数要高于分解系数,Mn、Zn、Pb、Cd的富集系数要高于其他元素。     

渭北黄土区人工刺槐林生长与生物量效应

通过比较黄土区不同立地条件刺槐人工林各器官生长指标及126株解析木生物量实测资料,分析不同密度刺槐人工林的生长与生物量状况,揭示林分不同径级的密度变化特征,拟合单株生物量与胸径、树高的生长模型.结果表明:在撂荒地、坡耕地和荒坡地营造刺槐林后,随林龄的增长和密度的变化,单株总生物量均表现为平均树干占47.1％,树枝和根系分别占22.22％和25.41％,树叶和果实的比例最低,而且高密度林分内林木的树干生物量均小于低密度林分.同时,30年撂荒地造林密度为1 050株/hm2时,24 cm径级树干生物量占65.5％;35年坡耕地造林密度950株/hm2时,24 cm径级树干生物量占58.39％;30年荒坡地造林密度1 410株/hm2时,24 cm径级树干生物量占51.6％.另外,30年中小径级的树木占林分总密度的67.62％,35年中径级的树木占林分总密度的52.84％.从刺槐生长状况分析结果看,黄土区刺槐人工林的适宜密度为950 ～1 050株/hm2,并应对该区生长30～35年的中径级刺槐林进行合理间伐利用,方可获得较高的生物产量.     

关于长江上游黄河上中游天然林资源保护工程区实施人工林商品性采伐的思考

通过对工程区内人工林资源和现行采伐管理政策的分析,探讨了对人工林实施商品性采伐的必要性、政策建议和有效的保障措施。     

两种不同人工林树木个体生长规律的研究

通过对两种不同人工林个体生长规律的研究,从树高、胸径、材积三方面初步揭示了华北落叶松(Laris gmelini)和杨树(Populus spp.)的个体生长发育规律,并分析其生物量分布特征,结果表明:杨树的高生长速生期比落叶松早;落叶松林缘树木的数量成熟年比林地中心的树木晚达到;杨树在26 a间未达到数量成熟年;杨树的林缘树木不论胸径、树高和材积生长量均比林中心的高,而落叶松则相反。初步阐明落叶松与杨树对生境条件的适应特征,确定了华北落叶松与杨树的数量成熟年,为人工林的经营和管理奠定坚实基础。     

间伐对华北落叶松人工林凋落物和土壤理化性质的影响研究

为了了解间伐对华北落叶松人工林凋落物和土壤理化性质的影响,利用试验测定和定量统计的方法,分析比较了河北省塞罕坝机械林场间伐和未间伐华北落叶松人工林凋落物层和土壤层(0~10cm、10~20cm)的理化性质,结果显示:与未间伐林分相比,50%强度间伐6a后林分内凋落物层生物量、质量含水量、有机质含量和全氮含量分别提高了17.25%、6.05%、9.08%、31.94%;土壤层的质量含水量、土壤容重和有机质含量有所上升(0~10cm土壤层分别增加4.84%、11.11%、15.67%;10~20cm土壤层分别增加10.25%、12.50%、28.97%),而全氮含量呈下降趋势(0~10cm土壤层减少20.83%;10~20cm土壤层减少16.67%);土壤pH值亦有所下降。研究进一步证实,通过间伐能够增加地表凋落物生物量,改变有机质分解速率,从而在一定程度上影响土壤的理化特性。     

我国茶园管理机械化技术研究进展

综述了我国茶园垦殖动力和机械、茶园土肥管理机械、茶园灾害管理机械、茶树管理机械等茶园管理机械化技术现状,指出其存在问题与发展方向,并根据我国茶产业现状提出开展茶园管理机械化技术集成和推广的设想。