Stand biomass and carbon storage of bamboo forest in Penglipuran traditional village, Bali(Indonesia)

Bamboo forest is an important land use in the traditional village of Penglipuran, Bali Indonesia. Bamboo growing in the rural areas can be a good choice for capturing CO2. I harvested selected culms to determine biomass content, and 50 % of dry weight biomass was calculated as carbon content. The Penglipuran bamboo forest supported six bamboo species in a one hectare sampling plot, all of the genus Gigantochloa. The clump and culm densities were 339 and 7190 ha-1, respectively.Total above- plus below-ground biomass was87.35 Mg ha-1, and carbon storage was 43.67 Mg ha-1.Carbon storage estimated in the bamboo forest at Penglipuran offers insight into the opportunity for PES（payment for ecosystem services） through emission trading mechanisms.

Biomass accumulation and organic carbon stocks of Kandelia obovata mangrove vegetation under different simulated sea levels

Mangrove forests are vulnerably threatened by sea level rise(SLR).Vegetation organic carbon(OC)stocks are important for mangrove ecosystem carbon cycle.It is critical to understand how SLR affects vegetation OC stocks for evaluating mangrove blue carbon budget and global climate change.In this study,biomass accumulation and OC stocks of mangrove vegetation were compared among three 10 year-old Kandelia obovata(a common species in China)mangrove forests under three intertidal elevations through species-specific allometric equations.This study simulated mangrove forests with SLR values of 0 cm,40 cm and 80 cm,respectively,representing for the current,future~100 a and future~200 a SLR of mangrove forests along the Jiulong River Estuary,China.SLR directly decreased mangrove individual density and inhibited the growth of mangrove vegetation.The total vegetation biomasses were(12.86±0.95)kg/m^2,(7.97±0.90)kg/m^2 and(3.89±0.63)kg/m^2 at Sites SLR 0 cm,SLR40 cm and SLR 80 cm,respectively.The total vegetation OC stock decreased by approximately 3.85 kg/m^2(in terms of C)from Site SLR 0 cm to Site SLR 80 cm.Significantly lower vegetation biomass and OC stock of various components(stem,branch,leaf and root)were found at Site SLR 80 cm.Annual increments of vegetation biomass and OC stock also decreased with SLR increase.Moreover,significant lower sedimentation rate was found at Site SLR 80 cm.These indicated that SLR will decrease mangrove vegetation biomass and OC stock,which may reduce global blue carbon sink by mangroves,exacerbate global warming and give positive feedback to SLR.

Biomass and Nutrient Accumulation Characteristics of Young Stands of Alnus cremastogyne

To investigate plant biomass and nutrient distribution and accumulation in organs of Alnus cremastogyne at different ages from 1 to 4 years, the biomass, N, P, K, Ca, Mg, Fe and Zn were tested. The results showed that the average biomass of the whole tree and the biomass of leaf, branch, stem, and root were in positive correlation with tree age, but the growth rate of biomass had a decreasing trend with the tree age increasing, and only the biomass proportion of the trunk in the whole individual plant showed an increasing trend with age. The contents of nutrient elements in organs showed an order of N 〉 Ca 〉 K 〉 Mg 〉 P 〉 Fe 〉 Zn ; and the contents of N, P and K were higher in the leaf than in other organs, and the contents of Ca, Mg and Fe in the root were higher than in other organs. The accumulations of N, P, K, Ca, Mg and Zn were the highest in the trunk, and that of Fe was the highest in the root. The annual net accumulations of N, P, K, Ca and Mg in the average trees from 1 to 4 years old were 17.07, 40.79, 95.82 and 106.71 g, respectively, and the annual net accumulations of microelements （Fe and Zn） were 335.04, 577.26, 1267 and 1525.27 mg, respectively.

Disentangling the factors that contribute to variation in forest biomass increments in the mid-subtropical forests of China

Mid-subtropical forests are the main vegetation type of global terrestrial biomes, and are critical for maintaining the global carbon balance. However, estimates of forest biomass increment in mid-subtropical forests remain highly uncertain. It is critically important to determine the relative importance of different biotic and abiotic factors between plants and soil, particularly with respect to their influence on plant regrowth. Consequently,it is necessary to quantitatively characterize the dynamicspatiotemporal distribution of forest carbon sinks at a regional scale. This study used a large, long-term dataset in a boosted regression tree（BRT） model to determine the major components that quantitatively control forest biomass increments in a mid-subtropical forested region（Wuyishan National Nature Reserve, China）. Long-term,stand-level data were used to derive the forest biomass increment, with the BRT model being applied to quantify the relative contributions of various biotic and abiotic variables to forest biomass increment. Our data show that total biomass（t） increased from 4.62 9 106 to 5.30 9 106 t between 1988 and 2010, and that the mean biomass increased from 80.19 ± 0.39 t ha-1（mean ± standard error） to 94.33 ± 0.41 t ha-1in the study region. The major factors that controlled biomass（in decreasing order of importance） were the stand, topography, and soil. Stand density was initially the most important stand factor, while elevation was the most important topographic factor. Soil factors were important for forest biomass increment but have a much weaker influence compared to the other two controlling factors. These results provide baseline information about the practical utility of spatial interpolationmethods for mapping forest biomass increments at regional scales.

Application of site-specific biomass models to quantify spatial distribution of stocks and historical emissions from deforestation in a tropical forest ecosystem

Allometric equations developed for the Lama forest, located in southern Benin, West Africa, were applied to estimate carbon stocks of three vegetation types：undisturbed forest, degraded forest, and fallow. Carbon stock of the undisturbed forest was 2.7 times higher than that in the degraded forest and 3.4 times higher than that in fallow. The structure of the forest suggests that the individual species were generally concentrated in lower diameter classes. Carbon stock was positively correlated to basal area and negatively related to tree density, suggesting that trees in higher diameter classes contributed significantly to the total carbon stock. The study demonstrated that large trees constitute an important component to include in the sampling approach to achieve accurate carbon quantification in forestry. Historical emissions from deforestation that converted more than 30% of the Lama forest into cropland between the years 1946 and 1987 amounted to 260,563.17 tons of carbon per year（t CO2/year） for the biomass pool only. The study explained the application of biomass models and ground truth data to estimate reference carbon stock of forests.

Assessing current stocks and future sequestration potential of forest biomass carbon in Daqing Mountain Nature Reserve of Inner Mongolia, China

Assessment of regional forest carbon stocks and underlying controls is critical for guiding forest management in the context of carbon sequestration. We investigated the variations in tree biomass carbon stocks relating to forest types, and estimated the total tree biomass carbon stocks and projected gains through natural stand development by 2020 and 2050 in the Daqing Mountain Nature Reserve based on Category II data of the Forest Inventory of Inner Mongolia for the period ending 2008. Over a total area of 388,577 ha,this nature reserve currently stores an estimated 2221 Gg C in tree aboveground biomass alone, with potential to grow by more than 30 % to reach 2938 Gg C by 2020 and nearly double to 4092 Gg C by 2050 through natural development of the existing forest stands. The tree biomass carbon density and potential gain in tree biomass carbon stocks vary markedly among forest types and with stand development.The variations in the potential change of tree biomass carbon density for the periods 2008–2020 and 2008–2050 among forest types partly reflect the varying relationships of tree biomass carbon density with stand age for different tree species, and partly are attributable to variations in the stand age structure among different forest types. Of the major forest types, the ranking of projected changes in tree biomass carbon density are not consistent with variations in the relationship between tree biomass carbon density and stand age, neither are they explainable by variations in stand age structures, implying the interactive effect between forest type and stand dynamics on temporal changes in tree biomass carbon density. Birch rank highest for future biomass carbon sequestration because of its dominance in cover area and better age structure for potential gain in tree biomass carbon stocks. Poplar and larch were out-performers compared to other forest types given their greater contribution to total tree biomass carbon stocks relative to their distributional areas. Findings in this study illustrate that protection and proper management of under-aged forests can deliver marked gains in biomass carbon sequestration. This is of great importance to policy-makers as well as to scientific communities in seeking effective solutions for adaptive forest management and mitigation of anthropogenic greenhouse gases emissions using forest ecosystems.

Biomass and carbon storage of Gracilariopsis lemaneiformis(Rhodophyta) in Zhanshan Bay, Qingdao, China

Marine macroalgae can absorb carbon and play an important role in carbon sequestration. As an important economic macroalga, Gracilariopsis lemaneiformis has the potential to significantly affect carbon absorption and storage in wave-sheltered intertidal reef systems. However, detailed knowledge on seasonal biomass changes and carbon storage of G. lemaneiformis is lacking, especially in many small and scattered ecosystems. Considering the influence of human activities on wild distribution of G. lemaneiformis, the understanding of seasonal dynamics of an economically important species in nature is necessary. In this study, we first investigated seasonal variations in biomass, coverage area, and carbon storage during low tide from August 2011 to July 2012 in Zhanshan Bay, Qingdao, China. Furthermore, we estimated the carbon storage potential of wild G. lemaneiformis using light use efficiency （LUE）. The results show that the standing biomass and coverage area changed significantly with season. However, seasonal variations in carbon content and water content were not obvious, with an average content of 35.1% and 83.64%, respectively. Moreover, carbon storage in individual months varied between 0.67 and 47.03 g C/mE, and the value of carbon storage was the highest in August and June and the lowest in February. In Zhanshan Bay, LUE of G. lemaneiformis was only 0.23%. If it is increased to the theoretical maximum （5%-6%）, the carbon storage will have an increase of at least 21 times compared with the current, which suggested that carbon storage of wild G. lemaneiformis had a high enhancement potential. The study will help to assess a potential role of G. lemaneiformis in reducing atmospheric CO2

Carbon sequestration in biomass and soil following reforestation:a case study of the Yangtze River Basin

The effect of reforestation on carbon sequestration has been extensively studied but there is less understanding of the changes that stand age and vegetation types have on changes in biomass carbon and soil organic carbon(SOC)after reforestation.In this study,150 reforested plots were sampled across six provinces and one municipality in the Yangtze River Basin(YRB)during 2017 and 2018 to estimate carbon storage in biomass and soil.The results illustrate that site-averaged SOC was greater than site-averaged biomass carbon.There was more carbon sequestered in the biomass than in the soil.Biomass carbon accumulated rapidly in the initial 20 years after planting.In contrast,SOC sequestration increased rapidly after 20 years.In addition,evergreen species had higher carbon density in both biomass and soil than deciduous species and economic species(fruit trees).Carbon sequestration in evergreen and deciduous species is greater than in economic species.Our findings provide new evidence on the divergent responses of biomass and soil to carbon sequestration after reforestation with respect to stand ages and vegetation types.This study provides relevant information for ecosystem management as well as for carbon sequestration and global climate change policies.

A study on the Antarctic circumpolar wave mode-A coexistence system of standing and traveling wave

The Antarctic circumpolar wave （ACW） has become a focus of the air-sea coupled Southern Ocean study since 1996, when it was discovered as an air-sea coupled interannual signal propagating eastward in the region of the Antarctic Circumpolar Current （ACC）. In order to analyze the mechanism of discontinuity along the latitudinal propagation, a new idea that ACW is a system with a traveling wave in the Southern Pacific and Atlantic Ocean and with a concurrent standing wave in the southern Indian Ocean is proposed in this paper. Based on the ideal wave principle, the average wave parameters of ACW is achieved using a non-linear approximation method, by which we find that the standing part and the traveling part possess similar radius frequency, proving their belonging to an integral system. We also give the latitudinal distribution of wave speed with which we could tell the reason for steady propagation during the same period. The spatial distribution of the propagation reveals complex process with variant spatial and temporal scales--The ENSO scale oscillation greatly impacts on the traveling process, while the result at the south of Australia indicates little connection between the Indian Ocean and the Pacific, which may be blocked by the vibration at the west of the Pacific. The advective effect of ACC on the propagation process should be examined clearly through dynamical method.

The effect of growth conditions on the relationship between fine root and foliage biomass

This article examines the physiological relationships between fine roots and foliage, and how their biomass ratio correlates with changes in stand quality class. The biomass of fine roots ≤ 3 mm in diameter of spruce stands in the Republic of Karelia (Northwest Russia) was determined by the soil monolith method. Foliage biomass was calculated using a previously designed technique from the standing stock, average height and quality class of the stand. A relation between fine-root: foliage biomass ratio and stand quality class (representing soil fertility) has been established. The closest correlation between fine-root: foliage biomass ratio and stand quality based on soil fertility was for the 1-2 mm root fraction. Analysis of the water flux balance in the trees revealed a correlation between fine-root: foliage ratio and the ratio of the specific volume of transpiration by the stand to the specific volume of water uptake from the soil by roots. Theoretical explanations for the decrease in fine-root: foliage biomass ratios with increasing stand quality class are offered.

Influence of topography,soil properties and plant community on the biomass of Abies georgei var.smithii seedlings in Southeast Tibet

Biomass of seedlings at different developing stages of growth is important information for studying the response of species to site conditions.The objectives of this study was to explore the distribution characteristics of AGB(above-ground biomass)and BGB(below-ground biomass)of Abies georgei var.smithii seedlings of different ages,and investigate the effects of topography(slope aspect,altitude),plant community characteristics(crown density,species diversity,etc.),and soil properties(soil physical and chemical properties)on the biomass and its allocation.Seedlings in five age classes(1–2,3–4,5–6,7–8,and 9–10 years old)were collected by full excavation from 6 elevations(3800 m,3900 m,4000 m,4100 m,4200 m,4300 m)on the north and south slopes of Sejila Mountain in Tibet.15seedlings of each age class were investigated at one altitude.The individual effects of seedling age(SA)and the interaction effects of SA,slope aspect(SL),and elevation(EG),namely,SL×EG,SL×SA,EG×SA,and SL×EG×SA,had significant effects on the AGB of the seedlings(p<0.05),whereas BGB was only significantly affected by SA(p<0.001).The AGB and BGB of the seedlings showed a binomial growth trend with the increase in seedling age,and had an allometric relationship at different elevations,α(allometric exponential)varied from 0.913 to 1.046 in the northern slope,and from 1.004 to 1.268 in the southern slope.The biomass of seedlings on the northern slope was remarkably affected by stand factors,with a contribution rate of 47.8%,whereas that on the southern slope was considerably affected by soil factors with a contribution rate of 53.2%.The results showed that age was the most important factor affecting seedling biomass.The allometric pattern of seedling biomass was relatively stable,but in a highaltitude habitat,A.georgei var.smithii seedlings increased the input of BGB.Understanding seedling biomass allocation and its influencing factors is useful for evaluating plants’ability to acquire resources and survival strategies for adaptation to the environment in Tibet Plateau.

Phase grating in a doubly degenerate four-level system

In this paper, we suggest a doubly degenerate four-level system, in which the transition takes place between the hyperfine energy 52S1/2 F = 1 and 52P3/2 F = 2 in rubidium 87 D2 line, for studying atomic phase grating based on the cross-Kerr and phase conjugation effects. The phase grating with high efficiency can be obtained by tuning phase shift Ф between the coupling and probe field, when the coupling intensity is much stronger than the strength of probe field. Under different coupling intensities, a high diffraction efficiency can be maintained. A new and simple way of implementing phase grating is presented. However, in such an atomic system, two main limitations must be taken into account. First, the independence between steady state probe susceptibility and the coupling intensity, when the population decay rate is larger than the Rabi frequency of the coupling field, cannot result in diffraction grating; second, the sample to be prepared should not be too long.

湖北杉木人工林生物量及其可变密度预估模型研究

利用6~59年生杉木人工林190个标准地资料和517株样木生物量测定数据,以建立的单木生物量估算方程为基础推算出各林分单位面积生物量,并基于林龄、立地指数以及7种不同林分密度指标构建并选择最优的全林分生物量预估方程,研究湖北杉木人工林林分生物量及其变化规律。结果表明:该区域杉木人工林平均单株生物量为52.8893 kg,以胸径和树高为变量的二元单木生物量方程的拟合优度为0.91,其拟合优度和精度更高;林分平均单位面积生物量为101.4923 t/hm^(2),总体上呈随林龄增加而增大的趋势;基于多元回归技术的经验方程构建了含7个林分密度指标和不含密度指标共计16种林分生物量预估模型,包含林分立木株数和林木大小信息的林分密度指标的模型均达到了较理想的拟合效果,其中密度指数SDI的Schumacher修正收获模型精度最高,确定系数为0.95,检验精度为97%,对本区域杉木生物量估算具有较好的适用性,能为其人工林经营和质量提升提供参考与支持。

基于模糊性能水准的直立锁缝屋面系统风灾易损性分析

现有结构风灾易损性研究中的性能水准大多是定义明确的,其模糊性常被忽略。为客观描述风荷载作用下直立锁缝屋面系统的实际损伤状态,在其有限元模型及传统性能水准的基础上,通过引入隶属函数,提出一种基于模糊性能水准的风灾易损性分析方法。结合具体工程算例,该文建立了考虑模糊性能水准的直立锁缝屋面系统风灾易损性曲线,并研究讨论了模糊性系数和隶属函数形式对风灾易损性的影响。结果表明:存在一个交点临界风速,当基本风速小于该临界风速时,直立锁缝屋面系统的模糊损伤概率大于等于传统损伤概率,反之小于等于传统损伤概率;同一模糊性系数下,不同形式隶属函数对传统性能水准下结构风灾易损性的影响存在明显差异;同一形式隶属函数对结构风灾易损性的影响随模糊性系数的增大而增大,其表现为模糊性能水准下的风灾易损性曲线逐渐偏离传统性能水准下的风灾易损性曲线并趋于平缓。

西南桦立木生物量模型的研建

基于2019—2020年在云南省境内采集并测定的157株西南桦立木生物量(其中地上生物量106株、全树生物量51株),建立地上、地下生物量一元(二元)独立模型W=a×D^(b)、W=a×D^(b)×HC,并采用相容性生物量模型建立西南桦地上总生物量与树枝、树叶、树干各分项生物量之和相容的西南桦立木生物量模型,采用根茎比建立地下生物量模型。结果表明:对于西南桦地上生物量,一元、二元模型分别选用权函数W=1/(D^(2))、W=1/(D^(2)H),对于西南桦地下生物量,一元、二元模型分别选用权函数W=1/(D^(0.5))、W=1/(D^(0.5)H^(0.5)),进行加权回归求解模型参数,可明显减小异方差影响及提高模型稳定性;相容性生物量模型解决了立木树枝、树叶、树干等分项生物量之和与地上总生物量不相等问题;从评价指标来看,西南桦地上总生物量和树干生物量模型预估精度均在94%以上;树枝、树叶生物量模型预估精度在92%以上,地下生物量模型预估精度在87%以上。总之,各模型预估精度均达到了国家相关精度要求;研究成果可应用于西南桦生物量的估算。

基于经验模型和机理模型的杉木人工林生物量估测对比研究

为了揭示间伐干扰下杉木人工林生物量的变化规律,研究利用江西省吉水县石阳林场的36块杉木人工林样地的实测数据和研究区气候数据,通过基于经验的引入地位指数(SI)的生物量生长方程组和基于机理的3⁃PG模型,模拟并预估林分生物量,分析在间伐和非间伐的情况下,不同立地的林分其生物量0—50a的变化。结果表明:(1)构建了生物量生长方程组,并在参数a、b、c中引入地位指数SI,发现改进后的模型对于基础模型拟合精度更高,且对数似然比检验表明,改进效果显著(P<0.05)。(2)通过对3⁃PG模型预测精度验证发现,预估值和实测值之间有很高的一致性,各因子的决定系数(R^(2))在0.65—0.96之间,其中,胸径和树高的R^(2)均高于0.92;各因子的平均相对误差(MRE)不超过26%。(3)通过比较经验模型和机理模型的生物量预测发现,经验模型的预测误差MRE为16.50%,机理模型为23.52%,经验模型预估精度更高。进一步对未来预测对比分析表明,机理模型预估值高于经验模型。(4)两个模型模拟的杉木人工林生物量规律一致,即随着林龄的增加,杉木人工林林分总生物量均表现出先快速增加,后逐渐平稳的趋势;并且间伐不会改变这种趋势,但间伐林分在间伐后的生物量生长速率高于无间伐林分。此外,由于SI对经验模型影响显著,改进模型拟合效果更好,更具有生态学意义。参数化后的3⁃PG模型模预估精度较高,能够为江西杉木人工林生长规律研究提供依据。虽然经验模型和机理模型在对研究区杉木人工林生物量的预估上均具有较好的表现,但各具特点和局限性。经验模型参数较易获得,且经验模型预测生物量、林分胸高断面积和林分平均树高的R^(2)、MRE均优于机理模型;但模型对于建模数据内的评价效果较好,对于建模数据外的应用具有局限性,即经验模型更适合模拟生长期间的某一阶段的林分生物量。机理模型虽然需要的参数较多,但是考虑了生态学原理,弥补了经验模型的不足,可较好解释和模拟环境因子对树木生长的影响,对校正数据之外生长阶段的林分生物量预测更有优势。

晋西黄土区林分密度对油松人工林生物量及土壤理化性质的影响

【目的】探讨林分密度对油松Pinus tabuliformis人工林生物量与土壤理化性质的影响,为油松人工林高质量发展和生态服务功能持续稳定发挥提供理论支撑。【方法】以山西省临汾市吉县蔡家川流域30年生油松人工林为研究对象,采用标准木法测算不同密度条件下单株生物量及林分生物量,并测定土壤理化性质,分析林分密度对油松林生物量及土壤理化性质的影响,采用冗余分析(RDA)及斯皮尔曼(Spearman)相关性分析确定油松林生物量与土壤理化性质之间的关系。【结果】①不同密度油松人工林的单株生物量和林分总生物量差异显著(P<0.05),且随林分密度的增加,单株生物量逐渐减少,林分总生物量在密度1750株·hm^(−2)时具有峰值;②不同密度油松人工林地土壤理化性质差异显著(P<0.05),其中土壤孔隙度在林分密度1750株·hm^(−2)时最大,达52.38%,林地土壤含水量在林分密度2750株·hm^(−2)时最高,达13.84%,土壤肥力状况则在林分密度1750株·hm^(−2)时最佳;③通过冗余分析及斯皮尔曼相关分析发现:土壤总孔隙度、有机碳和速效磷与林分总生物量均呈极显著相关(P<0.01),地下生物量受到土壤含水量的显著影响(P<0.05)。【结论】以固碳释氧和维持最大生产力为目的,以及以提高土壤碳汇能力和改良肥力为目的的油松林,林分密度建议维持在1750株·hm^(−2)左右的油松林;以保持水土和改良土壤蓄水性能为目的的油松林,林分密度建议维持在1750~2750株·hm^(−2)。

华西雨屏区不同林龄柳杉人工林土壤微生物生物量碳氮含量和氮矿化速率特征

【目的】探究华西雨屏区不同林龄柳杉人工林根际与非根际土壤微生物生物量碳氮含量、活性氮含量和氮矿化速率的差异,为该区域柳杉人工林土壤氮素管理提供理论支持。【方法】以华西雨屏区中龄林(13 a)、成熟林(33 a)和过熟林(53 a)的柳杉人工林为研究对象,采集根际土和非根际土壤样品,测定微生物生物量碳、氮含量及氮矿化速率等指标。【结果】(1)柳杉成熟林根际土微生物生物量碳、氮含量整体显著高于中龄林和过熟林阶段,非根际土微生物生物量碳、氮含量随林龄增加呈降低趋势,而根际与非根际土微生物生物量碳氮比值均随林龄增加呈增加的趋势。(2)成熟林根际土与非根际土的铵态氮含量、铵态氮与硝态氮比值整体均显著高于中龄林和过熟林,而土壤硝态氮和无机氮含量随林龄增加均呈降低趋势,并且根际土铵态氮、硝态氮以及无机氮含量整体均高于非根际土。(3)成熟林根际土铵化速率及其根际效应显著高于其他林龄阶段;中龄林和成熟林根际土与非根际土的硝化速率和净氮矿化速率整体显著高于过熟林,并且根际土的硝化速率和净氮矿化速率整体均高于非根际土。(4)柳杉人工林土壤微生物生物量碳、氮含量和氮矿化速率与土壤理化性质密切相关。【结论】相较于中龄林和过熟林,柳杉成熟林根际土壤表现出更快的氮循环速率和更高的氮素有效性。因此,适当加强柳杉中龄林和过熟林氮肥管理可能更有利于提高柳杉人工林质量。

极端干旱对鄱阳湖碟形湖水生植物群落的影响

水生植物是水生生态系统的重要组成部分,为底栖动物、鱼类和水鸟提供食物来源和栖息场所。近年来鄱阳湖水位变化剧烈,极端水文事件频发,对水生植物生长产生了不利影响。目前,关于极端干旱对鄱阳湖水生植物的影响报道较少。该研究于2022年7月和2023年7月对鄱阳湖典型碟形湖大湖池、沙湖及常湖池的水生植物群落进行调查,结果表明,2022和2023年鄱阳湖碟形湖平均水深分别为(160.27±50.70)、(58.00±21.46)cm,透明度分别为(49.10±14.41)、(47.25±10.91)cm。浮叶植物菱(Trapa spp.)优势度最大,沉水植物刺苦草(Vallisneria spinulosa)和轮叶黑藻(Hydrilla verticillata)优势度及生物量在2023年有所增加。湖区干旱导致水位降低,水体透明度发生变化,影响了植物群落的物种数,导致植物多样性增加。不同年份碟形湖水位和水体透明度的变化对水生植物多样性有显著影响,2 a间鄱阳湖碟形湖水生植物群落的物种组成差异显著,表现为2023年干旱后挺水和湿生植物比例增加。该研究通过对比分析2 a的监测数据,探讨了极端干旱对碟形湖水生植物的影响,研究结果可为鄱阳湖水生植物的恢复和越冬水鸟的食物资源补充管理提供科学依据。

南方典型红壤侵蚀区马尾松林立木生物量无人机遥感估测

以南方典型红壤侵蚀区长汀县河田镇为例,结合无人机与激光雷达产生的点云数据优势,通过局部最大值和分水岭算法反演单木树高(H)和冠层半径(R_(c)),拟合以H和R_(c)为变量组合的异速生长方程,得到以新冠层参数为底的马尾松立木生物量模型。结果表明:提取树高的决定系数(R^(2))和均方根误差(RMSE)分别为0.93和0.49 m;计算冠层半径的R2和RMSE分别为0.88和0.64 m;估算立木生物量的R^(2)和RMSE分别为0.89和3.37 kg。本研究通过无人机遥感影像定量参数并构建的异速生长方程中,以组合(H+R_(c))为底的异速生长方程估测马尾松林立木生物量的精度较高,可以有效估测马尾松林立木生物量,可为南方典型红壤侵蚀区马尾松林立木生物量准确估测提供参考。