Evaluation of Forest Damaged Area and Severity Caused by Ice-snow Frozen Disasters over Southern China with Remote Sensing

The accurate assessment of forest damage is important basis for the forest post-disaster recovery process and ecosystem management. This study evaluates the spatial distribution of damaged forest and its damaged severity caused by ice-snow disaster that occurred in southern China during January 10 to February 2 in 2008. The moderate-resolution imaging spectroradiometer(MODIS)13 Q1 products are used, which include two vegetation indices data of NDVI(Normalized Difference Vegetation Index) and EVI(Enhanced Vegetation Index). Furtherly, after Quality Screening(QS) and Savizky-Golay(S-G) filtering of MODIS 13 Q1 data, four evaluation indices are obtained, which are NDVI with QS(QSNDVI), EVI with QS(QSEVI), NDVI with S-G filtering(SGNDVI) and EVI with S-G filtering(SGEVI). The study provides a new way of firstly determining the threshold for each image pixel for damaged forest evaluation, by computing the pre-disaster reference value and change threshold with vegetation index from remote sensing data. Results show obvious improvement with the new way for forest damage evaluation, evaluation result of forest damage is much close to the field survey data with standard error of only 0.95 and 1/3 less than the result that evaluated from other threshold method. Comparatively, the QSNDVI shows better performance than other three indices on evaluating forest damages. The evaluated result with QSNDVI shows that the severe, moderate, mild damaged rates of Southern China forests are 47.33%, 34.15%, 18.52%, respectively. By analyzing the influence of topographic and meteorological factors on forest-vegetation damage, we found that the precipitation on freezing days has greater impact on forest-vegetation damage, which is regarded as the most important factor. This study could be a scientific and reliable reference for evaluating the forest damages from ice-snow frozen disasters.

Forest Response to the US 1990 Clean Air Act: The Southern Spruce-Fir Ecosystem

The history of the Black Mountains in North Carolina and the southern Spruce-Fir ecosystem has been fraught with widespread forest decline since the mid 1960’s. Balsam Woolly Adelgid attacks and acidic deposition were two of the most recognized causes of decline. Uncertainty arose about the future of these forests, and projections were made regarding the endangerment or extinction of the endemic Fraser fir ([Pursh] Poiret). This study analyzed data sets from a permanent plot network in the Black Mountains dating 1985, 2002, and 2012. Indications that the Fraser fir population is stabilizing from a “boom-bust” cycle of population growth and has entered the stem exclusion stage of forest stand development are evident. Fir live stem density increased more than 250% from 1985 to 2002, and then declined 40% by 2012 at the highest elevations in the forest. Overall, fir appeared to be more impacted on western facing slopes than eastern ones. The population of red spruce experienced a steady decrease in live stem counts, but an increase in live basal area through all years, and at all elevation classes (1675 m, 1830 m, and 1980 m), indicating a normal progression through stand development. Red spruce was also most negatively impacted on western facing slopes. Live stem density was significantly higher (P 0.001) than eastern plots, but live basal area was similar between the two aspects. Atmospheric deposition concentrations of the four main acidic molecules at Mt. Mitchell all peaked in 1998, but decreased by 2012. These reductions, occurring shortly after tightened regulations in the 1990 amendments to the Clean Air Act may have potential implications for increased forest resilience.

Evaluating Southern Appalachian Forest Dynamics without Eastern Hemlock: Consequences of Herbivory by the Hemlock Woolly Adelgid

Eastern hemlock (Tsuga canadensis Carriére) and the Carolina hemlock (Tsuga caroliniana Engelmann) are ecologically important tree species in eastern North America forests that are currently threatened by the hemlock woolly adelgid (HWA, Adelges tsugae Annand, Hemiptera: Adelgidae). HWA has spread rapidly from its original introduction site into new areas. Once present, HWA kills its hosts over a period of 4 to 10 years leading to a phenomenon that is known scientifically and colloquially as hemlock decline. To date, quarantine, chemical management, and biocontrol efforts have failed to curb the spread of the HWA. As such, forest management efforts are now being redirected towards developing an understanding of the effects of hemlock removal on vegetation dynamics, changes in forest composition, and changes in ecosystem function. In this study, we parameterize a spatially explicit landscape simulation model LANDIS II for a specific forested region of the southern Appalachians. Parameterization involves defining the life-history attributes of 37 tree species occupying 11 ecological zones and is based on knowledge of: current vegetation composition data, recent historic management and fire regimes, and life-history traits of each species. The parameterized model is used to explore a simple scenario of catastrophic hemlock mortality likely to occur as a result of HWA herbivory. Our results emphasize that hemlock is an important foundation species. When hemlock is removed from the system, forest composition changes considerably with a greater presence of shade intolerant pine and oak species. Additionally, hemlock removal leads to a period of transient, relatively unstable vegetation dynamics as the forest communities restructure.

Soil nitrogen transformations varied with plant community under Nanchang urban forests in mid-subtropical zone of China

Soil N transformations using the polyvinyl chloride （PVC） closed-top tube in situ incubation method were studied in Nanchang urban forests of the mid-subtropical region of China in different months of 2007. Four plots of 20 m × 20 m were established in four different plant communities that represented typical successional stages of forest development including shrubs, coniferous forest, mixed forest and broad- leaved forest. Average concentrations of soil NH4^＋-N from January to December were not different among the four plant communities. The concentrations of soil NO3^--N and mineral N, and the annual rotes of ammonification, nitrification and net N-mineralization under the early successional shrub community and coniferous forest were generally lower than that of the late successional mixed and broad-leaved forests （p〈0.05）. Similar differences among the plant communities were also shown in the relative nitrification index （NH4^＋-N/NO3^--N） and relative nitrification intensity （nitrification rate/net N-mineralization rate）. The annual net N-mineralization rate was increased from younger to older plant communities, from 15.1 and 41.4 kg.ha^-1.a^-1 under the shrubs and coniferous forest communities to 98.0 and 112.9 kg.ha^-1.a^-1 under the mixed and broad-leaved forests, respectively. Moreover, the high annual nitrification rates （50-70 kg.ha^-1.a^-1） and its end product, NO3-N （2.4-3.8 mg·kg^-1）, under older plant communities could increase the potential risk of N loss. Additionally, the temporal patterns of the different soil N variables mentioned above varied with different plant community due to the combined affects of natural biological processes associated with forest maturation and urbanization. Our results indicated that urban forests are moving towards a state of＂N saturation＂ （extremely niUification rate and NO3^--N content） as they mature.

Forest vegetation of Xishuangbanna,south China

Xishuangbanna of southern Yunnan is biogeographically located at a transitional zone from tropical southeast （SE） Asia to subtropical east Asia and is at the junction of the Indian and Burmese plates of Gondwana and the Eurasian plate of Laurasia. The region, though surprisingly far from the equator and at a relatively high altitude, has a rich tropical flora and a typical tropical rain forest in the lowland areas. Based on physiognomic and ecological characteristics, floristic composition and habitats combined, the primary vegetation in Xishuangbanna can be organized into four main vegetation types： tropical rain forest, tropical seasonal moist forest, tropical montane evergreen broad-leaved forest and tropical monsoon forest. The tropical rain forest can be classified into two subtypes, i.e. a tropical seasonal rain forest in the lowlands and a tropical montane rain forest at higher elevations. The tropical seasonal rain forest has almost the same forest profile and physiognomic characteristics as equatorial lowland rain forests and is a type of truly tropical rain forest. Because of conspicuous similarity on ecological and floristic characteristics, the tropical rain forest in Xishuangbanna is a type of tropical Asian rain forest. However, since the tropical rain forest of Xishuangbanna occurs at the northern edge of tropical SE Asia, it differs from typical lowland rain forests in equatorial areas in having some deciduous trees in the canopy layer, fewer megaphanerophytes and epiphytes but more abundant lianas and more plants with microphyll. It is a type of semi-evergreen rain forest at the northern edge of the tropical zone. The tropical montane rain forest occurs at wet montane habitats and is similar to the lower montane rain forest in equatorial Asia in floristic composition and physiognomy. It is a type of lower montane rain forests within the broader category of tropical rain forests. The tropical seasonal moist forest occurs on middle and upper limestone slopes. It is similar to the tropical montane evergreen broad-leaved forest in the region in physiognomy, but differs from the latter in floristic composition. It is a vegetation type on limestone at high elevations. The monsoon forest in Xishuangbanna is a tropical deciduous forest under the influence of a strong monsoon climate and is considered to be a transitional vegetation type between a tropical rain forest and savanna in physiognomy and distribution. The tropical montane evergreen broad-leaved forest is the main montane vegetation type in the region. It is dominated largely by the families Fagaceae, Euphorbiaceae, Theaceae and Lauraceae. It differs from tropical lower montane rain forests in its lack of epiphytes and in having more abundant lianas and plants with compound leaves. It is considered to be a distinct vegetation type from the northern margin of mainland southeastern Asia, controlled by a strong seasonal climate, based on its floristic and physiognomic characteristics.

Quantifying multiple-site compositional turnover in an Afrotemperate forest, using zeta diversity

Background： Species turnover is typically measured by partitioning diversity components into alpha and pairwise beta diversity. However, alpha and beta components cannot express the full spectrum of multiple-site compositional turnover. To this end, zeta diversity has been proposed as an extended framework to allow complete biodiversity partitioning and to measure multiple-site species turnover. We use a zeta-diversity framework to explore the turnover and potential community assembly processes of an African Montane Forest. Methods： Using a 20 m grid, we explore the species turnover in a 4.55 ha forest plot located in the Garden Route National Park of South Africa, with 47 and 27 canopy and sub-canopy tree species in the regional poo We first calculate how zeta diversity declines and how the probability of retention of species with particular occupancies changes with increasing zeta orders （i.e. the number of sites [grid cells] involved in the calculation）. Using null models with row sums and column sums constrained respectively, we explore whether species turnover is driven by mechanisms of ecological differences （species-specific occupancies） or habitat heterogeneity （site-specific alpha diversity and thus environmental filters）. Results： The decline of zeta diversity with zeta order followed a power law; that is, the probability of retention increased with species occupancies, suggesting common species being more likely to be discovered in extra sites. The null model retaining row sums （species＇ occupancy） of the species-by-site matrix recreated perfectly the decline of zeta diversity, while the null model of habitat heterogeneity （retaining column sums） was rejected. This suggests that mechanisms driving species-specific occupancies （i.e. ecological differences between species） dictate the multi-site species turnover in the community. The spatial patterns of zeta diversity revealed little spatial structuring forces, supporting a fine-grain structure in these southern Cape forests. Conclusions： The framework of zeta diversity revealed mechanisms driving the large discrepancies in the occupancy among species that are behind the species turnover in the African Montane forest plot. Future studies could further link species turnover to spatial distance decay. Environmental filters and temporal turnover from landscape demography could bring a cohesive understanding of community assembly in these unique forest ecosystems.

应用多时序特征的哨兵系列影像对南方丘陵区树种识别

树种分类是森林资源调查和监测的重要工作,杉木和油茶作为袁州区主要经济树种,准确获取树种空间分布信息,对产量估算和资源管理具有重要意义。以江西省宜春市袁州区为研究区,试验融合时序哨兵-1(Sentinel-1)、哨兵-2(Sentinel-2)等数据,结合中国南方丘陵区树种特点,提取植被指数、红边植被指数、地形特征和纹理特征等构建特征变量组合,分别利用分离阈值法(SEaTH)和特征权重算法(ReliefF)进行特征重要性排序和特征优选,分析各特征对树种分类的影响。结果表明:(1)在使用光谱特征和植被-水体指数的基础上加入不同特征后,树种分类精度均有提升,其中纹理特征的加入更有利于树种分类。(2)结合随机森林算法和特征权重算法(ReliefF)对树种分类的精度最高,总体精度为85.33%,Kappa系数为0.81,优于相同特征组下的支持向量机算法和分类回归树算法。

Farmers’ Perception and Indigenous Knowledge for Natural Resources Management, Abo-Wonsho Woreda, Southern Ethiopia

In this study, the roles of indigenous knowledge and farmers’ perception of natural resources management were analyzed. A total of seventy households were selected by simple random sampling with replacement method for collection of data. Formal interviews were conducted to the 5% plus of households in the study area in addition to the focus group discussions and qualitative field observations. It was expressed by 98.6% of the total respondents that “Sera” which is the traditional practice has being used to manage natural resources in the study area. In the “Sera” systems, individuals are excluded a punishment from any kind of social interaction in a response to their unlawful action in the community natural resources. It was indicated by 84.3% of respondents that deforestation and related problems are the major challenges including grazing and shortage of farm size for the management of the culturally protected forest in the study area. The majority of the respondents (77.1%) believed that soil fertility decline in the study area. Development of effective participatory forest management and encouragement and supporting the traditional method of natural resources management is required to ensure the preservation and protection of these areas essential to ecosystem service provision, provide high biodiversity value and cultural heritage, and maintain the sustainability of culturally protected forest.

苏南“森林乡镇”生态空间优化提升——以无锡洛社镇为例

“森林乡镇”建设是响应绿色发展战略、践行生态文明建设的重要举措。首先,本文提出“森林乡镇”生态空间建设需要由只重绿量增长向量质兼顾的生态模式转化,由推动乡镇生态环境建设向全面提高乡镇宜居性转变。其次,以典型苏南乡镇—江苏无锡洛社镇作为案例,分析其建设“森林乡镇”面临的生态空间格局破坏、空间组织方式混乱无序、生态要素质量快速下降的主要空间问题。最后,提出复合生态视角下洛社“森林乡镇”生态空间优化提升策略,提出重点关注3个空间层面的问题,即宏观层面构建健康稳定的“森林乡镇”生态网络格局,中观层面构建具有江南水乡特色的产、居、野高度融合的空间模式,微观层面强化“森林乡镇”生态惠民、生态空间要素复合价值提升。

间伐对秦岭松栎混交林土壤异养呼吸的影响

【目的】研究间伐对秦岭松栎混交林土壤异养呼吸的影响,可深入了解该地区间伐对森林土壤异养呼吸造成的碳损失情况,为研究区森林经营碳汇提供科学依据。【方法】以秦岭松栎混交林为研究对象,对未间伐样地(ck)、间伐4 a、间伐12 a的样地采用静态箱-气相色谱法监测生长季土壤异养呼吸速率的月变化,并计算各处理异养呼吸的温度敏感性(Q_(10))。【结果】①相比ck,间伐4 a、间伐12 a的样地土壤微生物生物量碳均显著下降(P<0.05),土壤pH均显著上升(P<0.05),土壤总有机碳质量分数在间伐4 a的样地中显著下降(P<0.05)。间伐12 a样地的理化指标相比间伐4 a的样地更接近ck。②生长季土壤异养呼吸呈现“双峰型”变化规律,峰值分别出现在6和10月。异养呼吸累计通量在间伐后略有上升但不显著,不同样地从大到小依次为间伐12 a、间伐4 a、ck。③土壤温度与异养呼吸呈极显著指数正相关(P<0.001);间伐后Q_(10)降低,不同样地Q_(10)从大到小依次为ck、间伐12 a、间伐4 a。【结论】土壤温度是影响松栎混交林异养呼吸的关键因素。间伐没有导致秦岭松栎混交林异养呼吸通量显著增大。

海南省乡镇胶园林下经济发展思考--以屯昌县乌坡镇为例

发展胶园林下经济是海南省应对天然橡胶生产困境、提高农民收入、促进乡村振兴的重要措施。文章通过对屯昌县乌坡镇胶园林下经济发展现状进行调研,分析胶园林下经济发展的经验及面临的问题并提出相应建议,为屯昌县及其他乡镇乃至海南省其他地区胶园林下经济发展提供借鉴与启示。

温度对兰州市南北两山5种典型人工林土壤氮素硝化潜力的影响

【目的】旨在探究随着温度的变化,土壤氮素硝化量和硝化速率的变化机理。【方法】以兰州市南北两山5种典型人工林(新疆杨林、侧柏林、刺槐林、新疆杨-刺槐混交林、侧柏-刺槐混交林)土壤为研究对象,通过间歇性好氧淋洗法在室内培养,研究在不同温度(15、25、35℃)下,5种典型人工林土壤的氮素硝化特征。【结果】在前期培养内(0~7 d),在同一温度下(35℃),侧柏刺槐混交林的土壤氮素硝化速率最大,分别比新疆杨刺槐混交林、新疆杨林、侧柏林和刺槐林高8.8%、62.6%、64.8%、77.0%。在15~35℃温度范围内,随着温度的升高,5种林分的硝化速率和硝化量均增加;在整个培养期(84 d)内,5种林分的硝化量在35℃达到最大,在0~20 cm和20~40 cm土层,五种林分的硝化量均值表现为35℃>25℃>15℃,且侧柏刺槐混交林的土壤氮素硝化量最大,分别比新疆杨刺槐混交林、刺槐林、新疆杨林和侧柏林高2.5%、13.2%、28.7%、40.8%。【结论】在所有土层中新疆杨-刺槐混交林的土壤硝态氮含量最高,5种林分土壤硝态氮含量和硝化速率随着温度的增加而增加,随土层的加深而降低,且混交林的硝化量和硝化速率均显著高于纯林;各林分敏感性均表现为25℃/15℃>35℃/25℃。

乡村振兴背景下新疆林果业发展研究进展的可视化分析

研究新疆林果业发展对于促进农民增收、推动农村经济发展、实现乡村全面振兴具有重要意义。基于中国知网数据库,以“新疆林果业”文献为研究对象,借助CiteSpace软件,对年度发文量、研究机构、发文作者和关键词等进行分析。结果表明,发文量总体波动较大,数量较少,近2年呈上升趋势;研究机构主要集中在农业类高校,部分集中在科研机构;以依米提·肉孜、司地克江·艾外力为核心的团队研究成果最为丰富,但尚未形成较稳定的核心作者群;研究热点集中在品牌建设、发展对策、特色林果、林果产品、产业发展、机械化等方面。未来研究应加强研究单位、研究作者之间的合作,创新研究视角,拓展研究内容,推进多学科融合,将新疆林果业发展与实施乡村振兴战略相结合,推动新疆林果业高质量发展。

皖南山区不同类型森林土壤阳离子交换性能差异

为了解皖南山区不同类型森林土壤阳离子交换性能差异,为该区合理营林提供参考,选取皖南山区6种不同类型森林土壤(杉木林、马尾松林、栓皮栎林、外松林、天然阔叶林和杉木-栓皮栎混交林)为研究对象,比较森林土壤阳离子交换性能的差异。结果表明:(1)研究区土壤呈强酸性,土壤有机质含量为33.84~91.50 g·kg^(-1),总氮含量为0.94~3.37 g·kg^(-1),碱解氮含量为131.58~203.62 mg·kg^(-1),总磷含量为0.22~0.77 g·kg^(-1),有效磷含量为0.17~0.32 mg·kg^(-1);土壤主要缺乏速效磷养分。(2)阳离子交换量在8.09~12.57 cmol·kg^(-1)之间,排序为:天然阔叶林>外松林>马尾松林>混交林>杉木林>栓皮栎林,不同森林土壤间阳离子交换量的差异主要由其土壤有机质的差异引起。(3)交换性盐基总量在1.74~2.72 cmol·kg^(-1)g之间,排序为:马尾松林>外松林>杉木林>栓皮栎林>混交林>天然阔叶林,Ca^(2+)和Mg^(2+)是主要的盐基离子,是成土过程中Ca、Mg优先固持形成的。(4)盐基饱和度在13.97%~28.98%之间,排序为:马尾松林>杉木林>栓皮栎林>外松林>混交林>天然阔叶林,该差异是由淋溶作用和树木对盐基离子的吸收共同作用形成的差异。综上,研究区土壤保肥和缓冲性能较低且供肥能力较差,尤其是土壤速效磷供应能力差。其中松林的供肥保肥能力及缓冲性能明显优于其他树种森林,混交林的速效养分含量更高,故可通过营造松类混交林以及施肥来提高森林土壤供肥保肥能力和缓冲性能。

桉树林区水库致黑物鞣花酸对人源细胞的毒理效应研究

我国南方桉树林种植区里面的水库在秋冬季存在明显的天然致黑物质,主要为单宁酸、鞣花酸等多羟基酚类化合物及其铁盐络合物,中小型水库承担了农村生活饮用水源的功能,因此有必要评估天然致黑物质的毒性潜在风险。本文模拟南方桉树林区水库水体特有的天然致黑物,以不同浓度的鞣花酸(Ellagic acid,EA)和三价铁(Fe3+)为研究对象,评价暴露于EA和/或Fe3+对人源结直肠腺癌上皮细胞(DLD1)、肝细胞(LO2)和肾上皮细胞(293T)的一般细胞毒性、细胞内活性氧(Reactive Oxygen Species,ROS)水平和细胞形态变化,并确定不同质量浓度的EA和Fe3+的毒性作用特征。结果提示EA和Fe3+在单独暴露和联合暴露条件下表现出不同程度的细胞毒性。联合暴露时,DLD1在较高质量浓度的EA(1 mg/L,10 mg/L)联合1μmol/L Fe3+处理组中细胞活力显著下降,比EA单独暴露时毒性更强。而LO2和293T在联合暴露组中细胞活力均未产生明显变化,但与Fe3+单独暴露相比联合暴露后细胞活力显著下降。氧化应激检测结果发现,与DMSO对照组相比,EA和/或Fe3+暴露均显著增加了ROS水平。其中,DLD1和LO2的ROS结果可能提示EA与Fe3+共同暴露比EA单独暴露时对细胞内ROS生成的影响更大,提高了氧化应激水平。此外,暴露于EA和/或Fe3+对3种细胞的细胞形态没有发现明显变化,但显著抑制了LO2中肌动蛋白F-actin的表达。结果表明,EA和Fe3+的单独或联合暴露对人源细胞具有较强的毒害作用,按影响程度从大到小排序,依次为:肝细胞LO2>肠道细胞DLD1>肾细胞293T。本文为南方农村水源地污染物的精准管控提供了基础依据。

祁连山国家公园青海片区森林大样地生物多样性特征

【目的】通过监测森林大样地植物群落特征的长期动态变化,揭示物种多样性空间格局及维持机制,为该区域的生物多样性保护提供科学依据。【方法】以祁连山区青海云杉林生态系统为研究对象,采用相邻格子法进行大样地乔木植株每木调查,并解析其生物多样性调控因素。【结果】青海云杉林生态系统的乔木总数为35835株,青海云杉和祁连圆柏分别占据57.84%和23.82%。物种丰富度和平均株高分别为3种和10.7 m。Shannon-Wiener指数和Simpson指数分别为0.74和0.43,Shannon-Wiener指数偏低,但Simpson指数较高,存在物种数量集中度较高现象。森林大样地Shannon-Wiener受乔木高度、物种丰富度和Simpson指数的极显著影响。机器学习模型训练集和测试集的决定系数分别为0.95和0.93,均方根误差分别为0.06和0.08,表明模型对Shannon-Wiener指数的解释能力和预测精度均较高。【结论】青海云杉林物种多样性较低且受乔木高度、物种丰富度和Simpson指数的显著影响,其对维持该区域的生物多样性具有重要作用。

赣南马尾松林地表细小死可燃物含水率动态及模型

[目的]建立森林地表细小死可燃物(枯落叶、细枯枝、枯草等)含水率预测模型,预警区域森林火灾引燃的可能性及其潜在火行为。[方法]基于野外长期定位观测的赣南地区典型植被类型马尾松林地表细小死可燃物含水率数据,在不同地形条件和时间段进行气象因子随机森林相对重要性排序和皮尔逊相关性分析,建立地表细小死可燃物含水率随机森林模型和气象要素回归模型,比较不同模型精度指标,筛选适合赣南地区的森林火灾预测模型。[结果]赣南地区马尾松林地表细小死可燃物含水率具有明显变异性,阴坡含水率显著高于阳坡,在防火期初期最明显。地表细小死可燃物含水率与各气象要素(温度、相对湿度、风速、光照强度)具有极显著相关性(P<0.001);随机森林模型预测精度高于气象要素回归模型,阴坡2种模型精度均高于阳坡;具有滞后效应的光照强度因子对地表细小死可燃物含水率影响最大,影响地表细小死可燃物含水率的关键因素在阳坡是相对湿度、阴坡是风速。[结论]具有滞后效应的气象因子对赣南地区马尾松林地表细小死可燃物含水率有显著影响,考虑增加这些因素能更好预测地表细小死可燃物含水率变化,为火险预警提供可靠依据。

基于Sentinel-2的互助北山林场森林蓄积量反演研究

森林蓄积量是评估森林健康和固碳能力的关键指标,利用遥感技术能够实现区域森林蓄积量的快速估测。本研究以青海省海东市互助北山林场为研究区域,基于森林样地调查数据和Sentinel-2影像,利用提取出的单波段反射率、植被指数、纹理因子和地形因子等筛选出具有代表性的遥感特征,运用随机森林算法实现研究区森林蓄积量反演。主要结果如下:(1)基于皮尔逊相关性分析,确定B11、B10、B6、B7、EVI、SAVI、NIRv、ExGR、MNLI、B12为本研究森林蓄积量反演的遥感特征因子。(2)利用随机森林算法能够有效反演研究区森林蓄积量。反演结果的决定系数R2为0.73,均方根误差RMSE为1.65m^(3)/hm^(2)。(3)互助北山林场乔木林平均蓄积量为134.4m3/hm2,在空间分布上,中东部、东南部和北部部分区域森林蓄积量较高。

南亚热带森林凋落物对土壤呼吸的贡献及其影响因素

应用静态箱-气相色谱法对鼎湖山南亚热带3种主要类型森林土壤呼吸（S＋L和S）进行长达31个月的连续观测，结果表明：季风常绿阔叶林（BF）、针阅叶混交林（MF）和马尾松林（PF）凋落物对土壤呼吸年平均贡献率分别为27．82％、33．29％和36．35％，而且3个林型具有相同的季节动态特征，高峰期出现在雨季（4～9月），分别占全年贡献量的71．87％、61．89％和70．39％。土壤呼吸（S＋L）与凋落物输入量的季节变化有极显著正相关性（P〈0．001）；土壤含水量与凋落物对土壤呼吸贡献的相关性均达到极显著水平（P〈0．001）；土壤温度与土壤呼吸通量呈显著的正相关关系，但与凋落物对土壤呼吸的贡献的关系并不明显；降雨天气凋落物对土壤呼吸贡献率分别为28．63％、38．20％和40．12％，显著高于晴朗天气。