不同密度柚木人工林林下植被及土壤理化性质的研究

研究不同密度柚木人工林对林下植被及土壤理化性质的影响,为柚木人工林营建与可持续经营提供理论依据。以广东揭阳14~16年生不同林分密度（650、900、1 050、1 200和1 450 株·hm^-2）柚木人工林为研究对象,通过样方调查植被的种名、株数、高度及盖度等,并采集0~20和20~40 cm土样进行理化性质分析,对林下植被物种多样性指数及其土壤理化性质进行主成分分析评价,来评价不同林分密度下柚木人工林的立地质量。结果表明：随着林分密度增加,柚木人工林林下植被盖度整体表现出降低趋势,草本优势物种由阳生性到中生性,逐渐向阴生性的过渡,林下植被Shannon-Wiener指数、Simpson优势度指数、丰富度指数和均匀度指数表现出先增加后减少的趋势;相同密度下,表层土土壤理化性质优于下层土,随着林分密度增大,土壤理化性质整体呈现出先改善后退化的变化过程,不同林分密度间柚木人工林土壤毛管孔隙度、非毛管孔隙度、速效K、速效P、全P、交换性酸和交换性Al等指标差异性显著（P<0.05）;基于林下植被物种多样性和土壤理化性质主成分分析,不同林分密度柚木人工林物种多样性和土壤理化性质综合得分由大到小依次是：1 050 株·hm^-2（4.82）、900 株·hm^-2（1.58）、650 株·hm^-2（-1.30）、1 200 株·hm^-2（-1.81）、1 450 株·hm^-2（-3.29）。因此,说明适宜的林分密度（1 050 株·hm^-2）有利于保持较好的林下植被物种多样性和土壤理化性质,在柚木人工林经营的过程中,可以根据实际情况合理调整林分的密度。     

Managing sun bears in a changing tropical landscape

Aim

Across the tropics, large‐bodied mammal species are threatened by rapid and widespread forest habitat conversion by either commercial logging or agricultural expansion. How such species use these habitats is an important area of research for guiding their future management. The tropical forest‐dwelling sun bear, Helarctos malayanus, is the least known of the eight bear species. Consequently, the IUCN/SSC Bear Specialist Group ranks research on this species as a top priority. This study aims to investigate landscape variables that influence sun bear habitat use in forests under varying levels of degradation and protection.

Location

A 20,998 km² Sumatra forest landscape covering Kerinci Seblat National Park (KSNP), Batang Hari Protection Forest (BHPF) and neighbouring logging and agricultural concessions.

Methods

An occupancy‐based sampling technique using detection/non‐detection data with 10 landscape covariates was applied in six study areas that operated a total of 125 camera traps. The potential differences between habitat use (ψ) of sun bears were first modelled with broad‐scale covariates of study area, land‐use types and forest type. Sun bear habitat use was then investigated with the finer‐scale landscape features associated within these areas.

Results

From 10,935 trap nights, sun bears were recorded at altitudes ranging from 365 to 1791 m. At a broad‐scale, habitat use increased with protection status, being highest in KSNP (0.688 ± 0.092, ± SE) and BHPF (0.621 ± 0.110) compared to production (0.418 ± 0.121) and convertible (0.286 ± 0.122) forests. Within these areas, sun bears showed a preference for forest that was further from public roads and villages and at a lower elevation.

Main conclusions

The habitat suitability model identified several high‐quality habitat patches outside of the priority conservation areas for immediate protection. Consequently, conservation management strategies should emphasize the importance of high conservation value forests and prohibit further conversion of threatened lowland forests.

     

我国3个桉树人工林种植区生产力影响因素

研究影响桉树人工林生产力的主要因素,对于提高桉树人工林生产力以及经营水平和合理利用树种都具有重要的意义。收集我国3个桉树人工林种植区(广东省、广西壮族自治区、云南省)关于生物量与生产力研究中的相关数据,对海拔、林分密度、林龄、年均温和年降水量与乔木层生物量进行了主成分分析与混合模型分析,探究各因素对我国桉树人工林生物量与生产力的影响。结果显示:年均温、年降水量、林龄、海拔和林分密度均是影响广东、广西、云南这3个省(区)桉树人工林生物量的主要因素,其中年降水量对这3个地区桉树人工林的生物量影响极其显著(P0.01),林龄和林分密度对桉树人工林的生物量影响显著(P0.05)。这是因为这3个地区都位于亚热带,温度都属于桉树生长的适宜温度,而这3个地区存在明显的干湿季,降水量在季节和地域上分布不均匀,导致这3个地区年降水量存在较明显的差异。因此,年降水量成为影响这3个地区桉树人工林生物量的关键因素。     

酸雨胁迫对苦槠幼苗气体交换与叶绿素荧光的影响

常绿阔叶树苦槠(Castanopsis sclerophylla)是亚热带地带性顶极群落的建群种之一, 在区域森林资源保护和可持续利用方面具有重要的地位。在该区域日益严重的酸雨胁迫下, 研究其对于胁迫的生理生态响应具有重要的理论价值和实践意义。该文以苦槠幼苗为研究材料, 研究了酸雨胁迫对苦槠幼苗光合生理的影响。结果表明: (1)短时间内, pH 2.5处理下的幼苗叶绿素相对含量最低, 且与pH 5.6处理下的存在显著性差异(p < 0.05); 经过一段时间处理后, pH 4.0处理下的叶绿素相对含量最高, 表明低浓度的酸雨会促进叶绿素相对含量的增加。(2) 2007年4月, 光合速率(P_n)、PSⅡ最大光化学效率(F_v/F_m)和PSⅡ的潜在活性(F_v/F₀)在不同酸雨浓度处理下基本无变化。随着酸雨处理时间的延长, pH 2.5处理下的P_n、光饱和点、光补偿点和暗呼吸速率有显著降低, 且与pH 5.6处理下的存在显著性差异(p < 0.05)。pH 2.5处理组与pH 5.6处理组之间的F_v/F_m和F_v/F₀差异性逐渐减小。表观量子效率和气孔导度变化规律不明显。综合来说, 酸雨处理前期, 高浓度的酸雨胁迫对苦槠幼苗叶绿素相对含量、光合生理参数有显著影响, 但随着酸雨处理时间的增加, 酸雨胁迫对苦槠幼苗的影响逐渐减小, 表明其对外界不良环境具有一定的抵御能力和适应能力。     

Effects of patch size and basal area on avian taxonomic and functional diversity in pine forests: Implication for the influence of habitat quality on the species–area relationship

Relationships between avian diversity and habitat area are assumed to be positive; however, often little attention has given to how these relationships can be influenced by the habitat structure or quality. In addition, other components of biodiversity, such as functional diversity, are often overlooked in assessing habitat patch value. In the Sandhills Ecoregion of Georgia, USA, we investigated the relationship between avian species richness and functional diversity, forest basal area, and patch size in pine forests using basal area as a surrogate for overstory structure which in turn impacts vegetation structure and determines habitat quality within a patch. We conducted bird surveys in planted mature pine stands, during breeding season of 2011. We used three classes of stand basal area (BA): OS, overstocked (BA ≥ 23 m²/ha); FS, fully/densely stocked (13.8 m²/ha ≤ BA < 23 m²/ha); and MS, moderately stocked (2.3 m²/ha ≤ BA < 13.8 m²/ha). MS patches showed more structural diversity due to higher herbaceous vegetation cover than other two pine stocking classes of patches. Total species richness and functional richness increased with the size of MS patches, whereas functional divergence decreased with the size of OS patches (p < 0.05). Functional richness tended to be lower than expected as the size of OS patches increased. Greater richness of pine–grassland species was also found at MS patches. Percent cover of MS patches within a landscape influenced positively the richness of pine–grassland species (p < 0.05). Our results suggest that (a) avian species–habitat area relationship can be affected by habitat quality (structural diversity) and varies depending on diversity indices considered, and (b) it is important to maintain moderate or low levels of pine basal area and to preserve large‐sized patches of the level of basal area to enhance both taxonomic and functional diversity in managed pine forests.     

会同杉木人工林不同生长阶段植物固碳特征

为了探讨杉木人工林不同生长阶段的固碳功能,以会同杉木林为研究对象,在定位连续测定林分生物量和碳素含量的基础上,研究了杉木林不同年龄阶段的储存碳量及在各组分的分配和植物固碳能力。结果表明:杉木各器官碳素含量树叶树皮树根树干树枝,且随着林龄增加而增大;杉木林植被储存碳量为22.93—86.98 t/hm2,各个层次储存碳量乔木层林下植被层枯死物层;乔木层碳素在器官间的相对分配大小依次为树干树根树叶树皮树枝;树干碳素分配比随着年龄增长而增大,树枝、树叶随年龄增长而减少,树根和树皮虽有波动,但变化较平稳;树枝、树叶、树干、树皮和树根碳积累年均变化都呈单峰形曲线,但波峰出现林龄各有不同;杉木林固碳动态特征可分为固碳功能建立、固碳能力迅速增长、固碳能力最大、固碳能力相对平稳和固碳能力下降等5个阶段;杉木林的固碳能力,不仅受不同生长阶段生长发育生物学特性的制约,而且还受林分冠层结构特征以及土壤肥力条件的影响。     

经营措施对青檀人工林生物量及檀皮产量的影响

调查了青檀人工林不同经营措施对林分地上部分生物生产力及檀皮产量的影响.结果表明(1)在密度及墩龄相同条件下,单位面积檀皮产量与年龄成正比,出皮率与年龄成反比;(2)单位面积檀皮产量年增长以第3年为最高,分别是第2年和第4年年增长量的1.58倍和4.12倍;(3)在密度、留萌数及萌发年龄相同条件下,单位面积檀皮产量以条墩年龄12年为最高,分别是6年生和9年生的3.32倍和1.11倍;(4)四种造林密度类型(2500、3333、4200和5350墩/hm2)中,檀皮产量大小顺序为4200>3333>5350>2500.4200墩/hm2(株行距1.4m×1.7m)的林分檀皮产量是2500墩/hm2(株行距2m×2m)林分植皮产量的1.68倍;(5)在密度、墩龄相同条件下,每墩留萌数为10时,单位面积植皮产量最高.从收获经济生物量(檀皮)的角度考虑,青檀人工林密度应在3333～4200墩/hm2之间,轮伐期为3年;在条墩年龄为9年以上的人工林中,留萌数以10条为好.     

Biological legacies soften pine plantation effects for bryophytes

Biological legacies are organic structures and patterns remaining after a disturbance that may contribute to the complexity of the recovering vegetation. Legacies may, in turn, reduce the impacts of human disturbances such as logging and habitat transformation on elements of biodiversity. To examine the effects of biological legacies on biotic responses after disturbance, we surveyed 32 sites for bryophytes in an area subject to large-scale conversion of native eucalypt forest to exotic Pinus radiata D. Don plantations in eastern Australia. We sampled bryophyte and substrate diversity (log, bare ground, upturned tree/log, and trees) in eight sites in each of four landscape context classes: pine plantation stands, elliptical-shaped remnants, strip-shaped remnants, and controls in a large area of contiguous, unmanaged eucalypt forest. We found a muted response by individual species of bryophyte to landscape context. We attribute this, in part, to the presence of logs in the intensively managed pine plantation sites. The boost in bryophyte diversity from species on logs meant that some pine sites supported similar species composition to the continuous eucalypt forest controls. Our findings also underline the importance of local controls and structural variation, including leaving logs and native trees in plantations, for enhancing bryophyte species richness in managed landscapes.     

生长光强对亚热带自然林两种木本植物稳定碳同位素比、细胞间CO2浓度和水分利用效率的影响

生长于１００％、４０％和１６％自然光下的荷木和黧蒴幼苗叶片稳定碳同位素比（δ１３Ｃ,－‰）,细胞间ＣＯ２浓度（Ｃｉ）和水分利用效率（ＷＵＥ）有一定的差别。１６％和４０％弱光下,δ１３Ｃ的负值增加－０．５４Ｊ‰到－０．８９‰。Ｃｉ增大８．１－１３．２μｉＬ－１,ＷＵＥ则下降６－２４％。结果表明,叶片的水分和气体交换特性受生长光强的调节,叶片的δ１３Ｃ值可反映其生长过程中受光的强弱状况。