Soil and foliar phosphorus as indicators of sustainability for Pinus radiata plantation forestry in New Zealand

We investigated how multiple-crop forestry has influenced the magnitude and variability of soil and plant phosphorus (P) fertility and site disturbance. Kinleith Forest, on Mamaku Plateau, covers >100,000 ha and comprises mainly plantation Pinus radiata. Three study areas in the forest were chosen to represent natural state (native forest), first crop of P. radiata (24 years growth), and second crop of P. radiata (4 years growth of second crop). The adjacent areas have similar relief and climate, and the soils are all the same age, being predominantly Andic Haplohumods developed in 1770 calendar-year-old non-welded tephra (Taupo Ignimbrite, ca. 0.5–0.8 m in thickness) and overlying a buried paleosol on earlier tephric material.

Soil properties were compared using a random geometric sampling scheme stratified in a 40-m grid. Soil samples (0–20 cm) were taken at 1.5, 4.5 and 13 m spatial intervals in random directions away from each primary node, providing 192 sample sites for each study area. Additionally at selected sites, samples of the current year's foliage from the upper crowns were collected, the thickness of Taupo Ignimbrite (i.e. depth to buried paleosol) was recorded by augering, and site disturbance was assessed using a new six-point scale based on change relative to a modal soil profile. Geostatistics and geographical information systems (GIS) were used to assess variability and effects of forest management on the measured properties. Soil Bray-2 P concentrations were below guidelines for satisfactory growth (12 mg kg⁻¹) at all sites, and no differences were recorded between the different management areas. However, the amount of within-site variability in Bray-2 P increased with the number of crops. Foliar P concentrations were only marginally deficient in both the first and second crops, indicating that P is currently not significantly limiting growth. The lack of difference in foliar P between first and second crops indicates no crop-to-crop decline in foliar P status and suggests that no site P fertility decline has occurred. The soils have an unusual ability to continue releasing P through successive sequential extractions in the Bray-2 P test, indicating a strong buffering capacity, and this may explain the apparent lack of deficiency even with Bray-2 P values of <12 mg kg⁻¹. The site disturbance index increased and the spatial distribution of P data became increasingly variable with crop rotation.

GIS, inverse-distance weighting and kriging proved useful in illustrating the trends between crops. The spatial variability of results indicated that there was no obvious pattern to the variability and that more site-specific forest management in the region would be difficult. However, there was some evidence that less disturbance during harvesting may minimise variability of soil P supply.     

Stand structure and the regeneration ofChamaecyparis pisifera (Sieb. et Zucc.) Endl. on sites with different soil development in an old-growth coniferous forest, central Japan

Stand structure and the regeneration ofChamaecyparis pisifera on sites with and without well-developed soil in an old-growth coniferous forest, Akasawa Forest Reserve, central Japan, were investigated, along with their relationships to other important coniferous species. Of stems ofC. pisifera≥5 cm diameter at breast height, stems with intermediate size were absent in stands on the developed-soil site, while those with smaller size increased in stands on the undeveloped-soil site, which supported a higher density ofC. pisifera. In the stands without recent tree-fall of canopy stems on the developed-soil site, canopy stems ofC. pisifera were distributed uniformly and the understory stems, patchily. On the other hand, both canopy and understory stems ofC. pisifera in stands on the undeveloped-soil site were distributed patchily. In the understory,C. pisifera occurred as clonal patches formed by vegetative reproduction on various types of microsites including bare rocks. However, the clonal patches did not occur in a stand on the developed-soil site with dense saplings of an evergreen conifer,Thujopsis dolabrata, which can expand vegetatively with a well developed soil layer. Gap formation may induceC. pisifera to develop tree-form stems from shrubby clonal patches. On developed-soil sites,C. pisifera stands that survive a long disturbance-free period on this site need catastrophic disturbance for their regeneration, which will eliminateT. dolabrata in the understory and create bare soil for colonization ofC. pisifera from seeds. On undeveloped-soil sites,C. pisifera replaces itself continuously by effective vegetative reproduction. Ground instability and the wet condition of this site may promote the replacement.     

大兴安岭北部原始林兴安落叶松种群世代结构的研究

在景观火干扰历史研究的基础上 ,研究了大兴安岭北部地区原始林兴安落叶松种群的世代结构及其与火干扰、立地条件之间的关系。结果表明 ,兴安落叶松种群基于世代数的世代结构类型丰富 ,从 1代型到6代型都有 ,空间分布呈斑块镶嵌状。以 3代型与 4代型为主要类型 ,空间分布集中 ,其它类型的世代结构空间异质性较高。世代数受火干扰频率、火干扰强度及两者的综合影响 ,相对来说以火干扰强度的影响更为显著。低频或高强类的火干扰易造成种群的世代数减少 ;高频或低强类的火干扰易造成世代数增多。世代数还随林型组类型而变化 ,溪旁林组 >赤杨林组 >杜香林组。兴安落叶松种群基于火干扰的世代结构类型也很丰富 ,存在 3大类、6亚类和 12小类 ,空间分布呈斑块镶嵌状。其中以更新优势火前劣势型和火前优势更新劣势型为主要类型 ,空间分布较聚集 ,其它类型的空间异质性较高。这种世代结构也受火干扰频率、火干扰强度及两者的综合影响 ,其中火干扰频率主要对种群的优势世代起着扶持作用 ,而火干扰强度则主要对劣势世代起着制约作用。低频或高强火烧地上 ,世代结构为更新优势火前劣势型 ,中频或中强类火烧地上为更新优势火后劣势型 ,高频或低强火烧地上为火前优势火后劣势型。世代结构还随立地条件而变化。溪旁林组     

福建寿宁县兽害猖獗的成因及对策初探

1998～2006年,以寿宁县为调查对象,运用机械抽样法调查样带69条,运用访问调查法调查猎户农户100余户,运用点面互换法调查全县范围内农田作物受害程度。结果表明,全县近半数的村,15%的耕地存在兽害,99%的兽害及其损失源于野猪的活动。分析表明,兽害的成因有种群爆发、物种灭绝和生态系统衰败诸多因素,而人为干扰是各种现象的起因。最后提出治理山区兽害的对策,尤其应加强生态系统恢复和自然保护区建设。     

甜槠群落主要种群空间分布格局对人为干扰的响应

研究了不同人为干扰强度对甜槠天然群落中主要种群甜槠和赤楠的分布格局的变化动态.结果表明,人为干扰会使甜槠种群的聚集性加强,而赤楠种群的聚集性降低.干扰强度对甜槠聚集性的影响随树龄的增大而逐渐减小,而对赤楠聚集性的影响则是随林龄增大呈现由小→大→小的规律.     

林隙微生境及更新研究进展

系统评述了国内外关于林隙干扰及更新的最新研究进展.林隙是一种经常发生的小规模干扰,是森林群落时空格局变化的驱动力.不同的林隙干扰状况导致了林隙内光照的差异,进一步造成林隙内温度、湿度、土壤理化性质的变化,形成了微生境的时空异质性.林隙干扰通过改变微生境而对幼苗的出土、存活、定居和生长产生重要影响.林隙内种子库的物种丰富度变化很大,是幼苗分布格局的重要影响因子.更新幼苗的存活率和生长量受林隙大小及幼苗在林隙中位置的影响.指出了这一领域今后的研究方向.     

Fine roots refilling process in an artificial gap in a Picea mongolica forest

Picea mongolica is an endemic but endangered species in China. The spruce forest is only found in sandy forest-steppe ecotones. In this study, we examined the initial response of the quantity and refilling process of fine roots in an artificial canopy gap with a diameter of 36 m in a P. mongolica forest. Under the canopy, the fine root length densities of trees, shrubs and herbs were 2,622, 864 and 3,086 m·m–2, respectively. The fine root biomass of trees, shrubs and herbs were 148, 62 and 65 g·m–2, respect...     

不同强度人为干扰对马尾松生长的影响

不同强度人为干扰15a后,经解析木分析表明,轻度干扰林分中马尾松的胸径、树高、材积均保持良好的生长趋势,总生长量比中度干扰和重度干扰林分高,连年生长量和平均生长量在幼龄期也高于后二者,重度干扰林分的各要素生长量均增长缓慢。这些结果表明超过一定限度的人为干扰阻碍了林木的生长发育。     

我国三个典型流域人类活动净氮输入量估算及其影响因素

目的 人类活动氮素过量投入是引起面源污染的重要原因之一。阐明人类活动净氮输入量的时空分布特征及其影响因素,为解决面源氮素污染问题提供数据支持。方法 利用人类活动净氮输入量（net anthropogenic nitrogen input,NANI）模型,通过统计年鉴和文献综述获得NANI相关数据和参数,对农业化的香溪河流域、城镇化的太湖流域和全面推进农业绿色发展模式的洱海流域的净氮输入量进行评估。结果 从NANI强度上看,3个典型流域NANI平均值按照大小排序为：太湖流域（13 241 kg·km^-2·a^-1）、香溪河流域（2 183 kg·km^-2·a^-1）、洱海流域（1 582 kg·km^-2·a^-1）。从来源上看,氮肥施入（Nfer）和食品/饲料氮（Nim）是NANI最大来源,占比58%—97%,对NANI贡献从大到小排序为：氮肥施入、食品/饲料氮输入、氮沉降输入、作物固氮输入。从时间尺度看,2019年同2010年相比,香溪河流域NANI中食品/饲料氮输入比例下降23个百分点,氮沉降比例上升34个百分点;洱海流域NANI中氮肥施入比例下降86个百分点;太湖流域NANI中食品/饲料氮输入比例上升31个百分点,作物固氮量和氮沉降输入比例下降14个百分点和12个百分点。从影响因素上看,3个典型流域NANI与城镇人口密度均呈现显著相关性（P<0.05）,且随城镇人口密度的增加NANI随之升高;耕地面积占比与NANI的拟合上,香溪河流域有显著影响（P<0.05）,但洱海流域和太湖流域均无显著影响（P>0.05）。结论 香溪河流域中昭君镇、峡口镇和黄粮镇,洱海流域中下关镇、上关镇和凤仪镇,太湖流域中张家港市、嘉兴市秀城区、杭州市拱墅区和上海市南汇区是NANI的关键源区;以农业为主的香溪河流域化肥施入是NANI的主要来源;城镇化程度较高的太湖流域食品/饲料氮和肥料氮投入是NANI主要来源;农业绿色发展措施可显著减少人类活动净氮输入量。因此,在关键源区大力推广农业绿色发展措施,同时有效降低饲料和肥料的投入量,有利于控制农业面源污染。     

火干扰与气候因子对兴安落叶松径向生长的影响

火干扰对森林生态系统的稳定具有重要影响。以1987年5月森林火灾后的漠河林区为研究对象,按照不同的林火强度设置样地,在不同强度火干扰样地内,分别采集兴安落叶松(Larix gmelinii(Rupr.) Kuzen)的树轮样芯,建立树木年轮的宽度年表,分析不同强度的火干扰及气候对兴安落叶松径向生长的影响。结果表明:(1)不同强度火干扰对落叶松径向生长影响程度不同,轻度火干扰样地落叶松生长存在胸径加速生长期,重度火干扰样地落叶松生长存在胸径减速生长期。(2)轻度火干扰样地落叶松年轮宽度与前一年7月份和当年7月份降水量呈显著正相关(P<0.05),与前一年9、11月份和当年9月份最高气温呈显著正相关(P<0.05);重度火干扰落叶松年轮宽度与前一年7月份和当年7月份最高气温呈显著负相关(P<0.05)。(3)不同强度的火干扰对年轮宽度和气候因子的相关性影响不同,重度火干扰样地落叶松年轮宽度与气候因子的相关关系在火干扰前后的变化比轻度火干扰更加明显;该地气温过度升高不利于重度火干扰后落叶松的恢复,而对轻度火干扰后落叶松的径向生长的影响不显著。