广东省雷州附城主要红树林群落碳储量及其影响因子

红树林生态系统具有碳储量高、碳汇潜力强的特点,选择碳密度高的红树林树种和最佳的碳汇环境有利于实现碳储量的最大化。以广东省雷州半岛附城沿海红树林为研究对象,通过比较不同林龄、不同潮位、不同树种栽种模式红树林群落碳储量,深入研究不同生物因素和环境因素对红树林碳储量的影响。该研究中,红树林碳储量包括植物碳储量和土壤碳储量两部分,植物碳储量通过地上植物、地下植物和凋落物的生物量的测定进行计算,通过测定土壤有机碳来计算土壤碳储量。结果表明,红树林群落碳储量一般具有随树龄增加而持续增大的趋势,主要原因为土壤碳储量不断增加。高潮位红树林碳储量高于低潮位的,潮位因素与树种因素对碳储量的影响具有交互作用,潮位因素对不同树种的影响程度不同。在研究区域内,20年生各群落碳储量排序为:无瓣海桑(S.apetala)-桐花树(A.corniculatum)桐花树(A.corniculatum)+秋茄(K.obovata)无瓣海桑(S.apetala)桐花树(A.corniculatum)无瓣海桑(S.apetala)-白骨壤(A.marina)秋茄(K.obovata)白骨壤(A.marina),碳储量分别为305.52、236.26、178.15、172.96、145.99、136.98、97.42 t·hm~(-2)。本研究可为合理制定红树林碳汇造林方案提供科学依据。     

福建漳江口4种红树植物叶片碳氮磷化学计量及养分重吸收特征

以福建漳江口红树林的秋茄(Kandelia candel)、桐花树(Aegiceras corniculatum)、白骨壤(Avicennia marina)和木榄(Bruguiear gymnorrhiza)为研究对象,对其成熟叶和衰老叶的C、N、P含量、生态化学计量比及重吸收效率进行分析,探讨不同树种养分限制格局及养分高效利用策略,结果显示:(1)成熟叶C、N、P含量范围分别为483.57-568.87、8.53-26.15、0.74-1.56g/kg,衰老叶为441.33-512.67、2.59-8.93、0.28-0.74g/kg,表现为成熟叶衰老叶;成熟叶的C:N、C:P、N:P变化范围为21.11-69.39、310.96-735.87、11.11-34.86,衰老叶为49.51-207.42、563.03-1 878.98、7.20-11.38,成熟叶C:N、C:P小于衰老叶(白骨壤的C:P除外),而成熟叶N:P大于衰老叶,4种红树植物C、N、P含量和化学计量比差异均达显著水平(P 0.05);成熟叶片C:N:P比范围为311:12:1-736:35:1,衰老叶为563:11:1-1 879:9:1;(2)N重吸收效率(NRE)范围为47.97%-84.64%,表现为木榄秋茄白骨壤桐花树;P重吸收效率(PRE)范围为18.39%-76.81%,表现为木榄秋茄桐花树白骨壤;4种红树植物N重吸收效率均大于P;(3)相关分析表明,NRE与成熟叶的C:N和C:P显著负相关(P 0.05),PRE与成熟叶P含量极显著正相关(P 0.01)、与成熟叶C:P极显著负相关(P 0.01).成熟叶片N:P阈值(14)指示秋茄、桐花树和木榄生长受N限制,白骨壤生长受P限制,受N限制的秋茄、桐花树和木榄具有较高的NRE,而受P限制的白骨壤并不具有较高PRE.综上可知,高效的NRE是红树植物适应低N环境的重要养分利用策略,而红树植物可能采取其他适应机制来响应低P胁迫.(表5参38)     

湛江特呈岛红树林植物群落的结构和动态特征

对特呈岛红树林植被进行多次和全面的调查,通过采用格子样的方法,选取面积为100～800 m^2的样地,每片样地再分成若干10 m×10 m的样方,对红树林样地内的植物进行每木测量,记录各植物的种名、胸径、高度、冠幅等,并进行重要性以及多样性等常规的群落分析,判定该地区植被的生长特征以及研究其演替动态变化。结果表明：①面积较大的群落主要有3个类型,即白骨壤群落（Avicennia marina）、白骨壤＋红海榄群落（Avicennia marina＋Rhizophora stylosa）、白骨壤-桐花树群落（Avicennia marina-Aegiceras corniculatum）;其它面积较小的群落有：白骨壤＋红海榄-木榄＋桐花树群落（vicennia marina＋Rhizophora stylosa-Bruguiera gymnorrhiza＋Aegiceras corniculatum）、红海榄＋木榄群落（Rhizophora stylosa＋Bru-guiera gymnorrhiza）;②在3个主要群落中,优势种的苗木和小树相对较少,优势种群的年龄结构均为衰退型;③各群落的Simpson指数关系为：白骨壤＋红海榄群落﹥红海榄＋木榄群落﹥白骨壤＋红海榄—木榄＋桐花树群落﹥白骨壤—桐花树群落﹥白骨壤群落;白骨壤群落的重要值为300,为典型的单优群落;④特呈岛的白骨壤群落是中国该类群落中面积最大的,目前长势良好,无病虫害,并且红树林外缘的白骨壤枝干在波浪冲刷或人为原因下,受到较严重的侵蚀,其幼树在林外缘基本无法存活,需要加强保护,对其生理生态学特征也值得进一步深入研究。     

珠海淇澳岛红树林蟹类区系

2008年7月—2010年9月,对珠海淇澳岛红树林不同生境和不同植被群落的蟹类进行了调查,共采集到蟹类8科24种,其中相手蟹科Sesarmidae种类最多,为9种;弓蟹科Varunidae次之,为5种,沙蟹科Ocypodidae 4种。Jaccard区系相似性指数表明,林内泥滩与林外硬质泥滩蟹类区系为中等相似（J=0.523）,林外硬质泥滩与高潮区光滩蟹类区系（J=0.071）及林内泥滩与高潮区光滩蟹类区系（J=0）都极不相似。林内泥滩蟹类中,谭氏泥蟹（Ilyoplax deschampsi）在数量上占绝对优势。无齿螳臂相手蟹（Chiromantes dehaani）、中华中相手蟹（Sesarmops sinensis）和弧边招潮蟹（Uca arcuata）等在红树林外道路两侧和堤坝较硬质泥滩数量较多,而林外高潮区光滩的蟹类都是耐干旱和奔跑能力较强的种类。天然秋茄（Kandelia candel）群落蟹类种类数和平均密度较人工引种的无瓣海桑（Sonneratia apetala）群落的少,但平均生物量较无瓣海桑群落高。秋茄群落蟹类密度和生物量与土壤全氮、全磷、有机质等理化因子都呈不显著相关;无瓣海桑群落土壤速效磷与蟹类生物量呈极显著正相关,与蟹类密度呈显著正相关;全磷与蟹类密度呈显著负相关。红树林土壤类型和新生蟹类补充进种群是影响珠海淇澳岛红树林蟹类密度和生物量变化的主要原因。     

南沙湿地公园红树林物种多样性与空间分布格局

红树林是海岸的特有植被类型,研究其物种多样性与空间分布,对红树林的恢复与保护具有重要意义。本文以南沙湿地公园红树林为典型案例,采用遥感影像解译和样方调查的方法,对红树林物种多样性、群落特征与空间分布格局进行研究。结果表明:(1)南沙湿地公园红树林物种多样性指数高于其他与之纬度相近的红树林群落;(2)以无瓣海桑Sonneratia apetala Buch-Ham.、桐花树Aegiceras corniculatum(L.)Blanco.、黄槿Hibiscus tiliaceus L.和芦苇Phragmites australis(Cav.)Trin.ex Steud.为优势种;(3)主要的群落类型为无瓣海桑群落、黄槿群落和芦苇群落等3种,总面积百分比达86.72%,无瓣海桑群落和黄槿群落面积占比分别为41.13%和36.44%,成为红树林的绝对优势群落;(4)红树林群落在空间上呈聚集态分布,聚集度最高的是无瓣海桑群落,其次是黄槿群落,面积占比最低的是木榄群落;(5)引进种无瓣海桑,发展态势好,抑制了乡土种红树植物生长。建议扩种白骨壤Avicennia marina(Forsk.)Vierh.、桐花树和秋茄Kandelia candel(L.)Druce.,扩大其斑块面积,以提升乡土红树植物群落的稳定性,达到有效保护红树林的目的。     

红树植物凋落叶分解对土壤可溶性有机质的影响

研究红树林湿地土壤可溶性有机质（DOM）的来源、性质及其归宿对于揭示 DOM 在红树林湿地生物地球化学循环中的作用具有重要意义。采集了木榄（Bruguiera gymnoihiza）、秋茄（Kandelia candel）和桐花树（Aegiceras corniculatum）3种红树植物的新近落叶进行室内48 d分解实验,探讨了凋落叶分解过程对土壤可溶性有机碳（DOC）和可溶性总氮（TDN）含量、C/N比（DOC/TDN）及紫外-可见（UV-Vis）光谱特征（A280、A240/A420和A250/A365比值）的影响。在48 d分解期间,3种红树植物凋落叶的输入均明显增加了土壤DOC的含量,其变化在分解第6 d最为显著,各凋落叶添加组比对照组平均增加了149%（秋茄）~196%（桐花树）,随后各凋落叶添加组土壤DOC含量呈下降趋势。与土壤DOC的变化不同,凋落叶输入后土壤TDN的变化与对照组的差异不明显,但木榄和桐花树添加组的C/N比在分解初期（第6天）显著高于对照组（P<0.05）。凋落叶的输入亦在不同程度上增大了土壤DOM的A280值,降低了DOM的A240/A420和A250/A365比值。与土壤DOC的变化相似,凋落叶输入使DOM的UV-Vis光谱特征在分解初期（第6天）的变化最明显,其中桐花树凋落叶的影响最大,秋茄凋落叶的影响最小。结果表明：凋落叶输入使培养初期土壤DOM的含量和性质发生明显改变,DOM中大分子及芳香类组分增多、团聚化程度增加,DOM 的生物可降解性变小。然而,随着分解的进行,不同凋落叶处理组之间土壤DOM的变化差异性逐渐缩小,并在分解后期与对照组趋近。     

广西英罗港不同红树林群落土壤CO2和CH4通量对气温变化的响应

采用WEST-1011便携式土壤通量测量仪对广西北海英罗港自然保护区不同红树植物群落土壤的CO2和CH4排放通量特征以及其与气温的关系进行研究。结果表明,各群落土壤CH4通量的值都较小,在-2~3μmol.m-2.s-1之间;红海榄Rhizophora stylosa群落、木榄Brugiera gymmonhiza群落一天的CO2通量变化很小,秋茄Kandelia candel群落一天的CO2通量变化比较明显,最大值出现在19：00,为5.001μmol.m-2.s-1,桐花树Aegiceras corniculatum群落一天的CO2通量变化明显,最大值出现在11：00,为8.325μmol.m-2.s-1。排放通量与气温做相关性研究发现,气温与红海榄群落、木榄群落土壤CH4通量与气温呈不显著的正相关关系,与秋茄群落呈现极其显著的负相关关系,与桐花树群落呈显著的负相关关系;气温与红海榄群落、木榄群落、秋茄群落、桐花树群落的土壤CO2通量均呈不显著的负相关关系。     

红树种植–养殖耦合系统牡蛎石油烃含量及红树净化效果

为减少滩涂养殖中的石油烃污染危害、提高水产品的品质,以珠江口滩涂红树林种植–养殖系统耦验示范研究基地A、B两系统的7个红树种植–养殖塘[包括桐花树(Aegiceras corniculatum)、木榄(Bruguiera gymnorhiza)、秋茄(Kandelia candel)、红海榄(Rhizophora stylosa)的单种或组合种植]为对象,采用荧光分光光度法监测了水体、底质及吊养的近江牡蛎(Ostrea rivularis)肉质的石油烃含量.结果表明,牡蛎体内石油烃含量在11.10~29.3 mg/kg之间;与水体中石油烃含量呈正相关(r=0.88),牡蛎能很好地指示水体水质状况.单种或组合种植秋茄、桐花树、木榄、红海榄4种红树植物能有效降低水体石油烃含量,与对照相比降幅为50%~80%;使牡蛎的石油烃含量受到不同程度的影响,与对照相比,红树种植塘牡蛎石油烃含量降幅在20%~60%不等.木榄和桐花树种植塘中,牡蛎中石油烃平均含量分别为11.20 mg/kg、14.13 mg/kg,能达到无公害水产品标准.因此红树种植–养殖塘具有"种植岛基质–红树植物–微生物"的协同效应,通过物理、化学和生物的共同作用降低了水体石油烃的含量,从而提高了养殖生物的品质.     

深圳湾红树林沉积物-植物体系汞的分布规律和形态分配特征

为了解重金属汞在非根际沉积物-根际沉积物-红树植物连续体系中的分布特征和迁移规律,以及沉积物中汞的化学形态特征,于深圳湾福田红树林实地采集红树植物幼苗样品及其林下沉积物样品,采用连续提取法对沉积物中汞的各种化学形态进行提取,通过冷原子荧光光谱仪进行定量分析。研究对象包括福田红树林3种常见红树植物,包括白骨壤(Avicennia marina)、桐花树(Aegiceras corniculatum)2个本土种和海桑(Sonneratia caseolaris)1个引进种,并以无植被覆盖的光滩作为空白对照。结果表明,在沉积物-红树植物体系中,根际和非根际沉积物中的总汞含量均高于红树植物幼苗。进入植物体后,汞在茎中的含量均小于根和叶。本土种植株表现出较强的汞积累能力。白骨壤幼苗汞积累量最高,质量分数达到45.32 ng·g-1,其次为桐花树幼苗,汞质量分数为23.49 ng·g-1。3种红树植物对汞的生物积累因子在0.02~0.35范围内,迁移因子处于0.4~0.99范围内,均低于1,表明它们从土壤吸收、并向地上部分运输汞的能力较弱,倾向于采取金属排斥策略,以实现植物体的自我保护。非根际沉积物中汞的各个化学形态质量百分比表现为有机结合态可挥发态残渣态可交换态碳酸盐结合态铁锰氧化物结合态,根际沉积物中汞表现为可挥发态机结合态残渣态铁锰氧化物结合态可交换态碳酸盐结合态,总体表现为生物可利用态和潜在可利用态质量分数较高,不可利用态较少。与本土种相比,引进种海桑能够将更多汞以稳定性相对较高的生物不可利用态和潜在可利用态形式固定于土壤中,表现出较好的治理汞污染能力。     

镉对桐花树幼苗生长及渗透调节的影响

采用土培方法研究不同质量分数Cd(0.5～50mg·kg-1)对桐花树Aegicerascorniculatum幼苗的生长及渗透调节的影响。结果表明:低质量分数Cd(0.5mg·kg-1)处理条件下,桐花树幼苗株高、植株鲜物质量均显著高于对照,根长、叶绿素质量分数则没有显著增加;高质量分数Cd(50mg·kg-1)条件下,这些参数均显著降低,说明高质量分数Cd胁迫下,植株正常生长受到抑制。除了0.5mg·kg-1条件外,叶片淀粉质量分数变化趋势总体上是随着Cd的增加而下降。在5~50mg·kg-1Cd处理下,渗透调节物质可溶性糖、可溶性蛋白质及脯氨酸均显著增加,与Cd质量分数存在正相关性。Cd胁迫下,渗透调节物质的积累作用是桐花树对Cd胁迫的主要响应过程,可溶性糖、可溶性蛋白及脯氨酸与可作为Cd对桐花树污染的检测指标。     

Growth of Avicennia marina and Ceriops decandra seedlings inoculated with halophilic azotobacters

Inoculation of azotobacter has significant positive effects on the growth characteristics and pigments in mangrove seedlings of Avicennia marina and Ceriops decandra. The bacterial inoculation significantly increased the root dry biomass at the maximum of 75.8% at 30 gl(-1) salinity in Ceriops decandra. But in Avicennia marina, the shoot dry biomass was increased significantly at the maximum of 56.12% at 30 gl(-1) salinity in general, the Azotobacter beijerinkii improved the growth characteristics better in both species of mangroves preferably at higher salinity levels in A. marina and at a range of salinity in C. decandra. The results recommend this forraising vigorous seedlings under nursery conditions.     

Dissolved iron supply limits early growth of estuarine mangroves

Three mesocosm experiments were performed in an outdoor facility to quantify the responses of five mangrove species grown from seedling to sapling stage to increasing rates of dissolved iron supply. Stem extension and biomass of mangroves were measured in the first two experiments, and in the third experiment, rates of microbial iron reduction were measured in relation to stem extension of two mangrove species. In all experiments, mangrove growth was enhanced by increasing iron supply, although some species showed iron toxicity at the higher supply rates. In the first two experiments, stem extension rates of Rhizophora apiculata, Bruguiera gymnorrhiza, and Xylocarpus moluccensis best fit Gaussian curves with maximal growth at supply rates of 50-60 mmol Fe x m(-2) x d(-1), whereas growth of Avicennia marina and Ceriops tagal increased to the highest rate (100 mmol Fe x m(-2) x d(-1)) of iron supply. Changes in leaf chlorophyll concentrations and iron content of roots mirrored the growth responses. In the third experiment, rates of microbial iron reduction were greater with R. apiculata and A. marina than in controls without plants; for both species, there was a positive relationship between stem extension and iron reduction. The rates of iron reduction and rates of iron supplied to the plants were well within the range of interstitial iron concentrations and rates of iron reduction found in the natural mangrove soils from which the seedlings were obtained. The responses of these species show that mangroves growing from seedling to sapling stage have a strong nutritional requirement for iron, and that there is a close relationship between plant roots and the activities of iron-reducing bacteria. These results suggest that mangrove growth may be limited in some natural forests by the rate at which iron is solubilized by iron-reducing bacteria. Such biogeochemical conditions have significant implications for successful recruitment, establishment, and early growth of mangroves.     

Role of grapsid crabs, Parasesarma erythrodactyla, in entry of mangrove leaves into an estuarine food web: a mesocosm study

The influence of the crab Parasesarma erythrodactyla on the entry of the organic matter derived from Avicennia marina mangrove leaves in a sub-tropical mangrove ecosystem of southeast Queensland, Australia, was simulated using tidal mesocosms. Degradation of mangrove leaf organic matter was followed by analysing the fatty acid composition, carbon, and nitrogen isotopic signatures of the surface sediment and suspended particulate organic matter (SPOM) with and without the presence of crabs. Assimilation of mangrove organic matter by P. erythrodactyla was also assessed by stable isotope and fatty acid analyses in tissues and faeces. Results of the chemical tracer analyses question the adaptability of P. erythrodactyla to a diet comprised exclusively of mangrove leaves, and suggest that these organisms were dependent on additional food sources in their natural environment. Crab processing of senescent leaves significantly accelerated the transfer of mangrove organic matter to the surface sediments, as shown by a higher C/N ratio, a higher contribution of long-chain fatty acids and a more depleted C isotopic signature of sediment samples in the mesocosms with crabs compared to those without crabs.     

Carbon sequestration potential of Rhizophora mucronata and Avicennia marina as influenced by age, season, growth and sediment characteristics in southeast coast of India

This work analysed the carbon sequestration potential in two species of mangroves (Rhizophora mucronata and Avicennia marina) along with their growth, biomass, sediment characteristics for four seasons of the year 2009–2010, in planted stands of different age (1–17.5 years) in the Vellar-Coleroon estuarine complex, India. The mangroves were recorded to store significant amount of biomass. Avicennia marina performed better to display 75 % higher rate of carbon sequestration than that in Rhizophora mucronata. This could be attributed to growth efficiency and high biomass production. For instance, Avicennia marina exhibited 2.7 fold higher girth, 24 % higher net canopy photosynthesis, 2 fold aboveground biomass (AGB), 40 % more belowground biomass (BGB) and 77.3 % higher total biomass, than R. mucronata did. Seasonally the rate of carbon sequestration was 7.3 fold higher in post-monsoon, 3.4 fold in monsoon, 73 % more in summer than that in pre-monsoon. The rate of carbon sequestration was positively correlated with age of planted site, tree height, tree diameter, net canopy photosynthesis, AGB, BGB, total biomass, carbon stock, growth efficiency, AGB/tree height tree girth, leaf area index, silt content (p?<?0.01). The carbon sequestration was negatively corrected with soil temperature and clay content (p?<?0.05). Mangroves were found to be a productive system and important sink of carbon in the tropical coastal zone, but increasing soil temperature due to global warming would have a negative impact on carbon sequestration potential of the mangroves.     

海南岛北部潮间带红树林对重金属的累积特征

对海南岛北部潮间带红树林湿地7种红树植物（根、茎、叶）及其根系沉积物中重金属元素含量进行了分析,结果表明：研究区湿地沉积物中Ni、Cu、Zn、As和Cd的变异系数大于0.50,沉积物中重金属分布很不稳定。其中Cr、Cu、Zn、As和Cd的含量均高于海南水系沉积物背景值,可能存在外源的输入。仅有Pb的含量略低于海南水系沉积物背景值。总体来看,大部分植物显示了对Cd元素的较强的富集能力（BAC〉1）,瓶花木对重金属元素的吸收能力总体上要比其他红树植物强一些,木果楝对重金属元素的吸收能力总体上最弱。其中,瓶花木（Scyphiphora hydrophyllacea）对Cr、Zn、As和Cd的吸收能力较强,莲叶桐（Hernandia sonora）对Cr和Ni的吸收能力较强,角果木（Ceriops tagal）对Pb的富集能力较强。角果木（Ceriops tagal）和桐花树（Aegiceras corniculatum）对Cd和Pb的运输能力较强,瓶花木（Scyphiphora hydrophyllacea）对Cu、Zn和Cd的运输能力较强,尖瓣海莲（Bruguiera sexangula）对Cr、Ni、Cd和Pb的运输能力较强,木榄（Bruguiera gymnorrhiza）对Ni、Cu、Cd和Pb的运输能力较强,木果楝（Xylocarpus granatum）对Cr、Zn和Cd的运输能力较强,莲叶桐（Hernandia sonora）对Cr也有较强的运输能力。但此次所研究的红树植物对As元素的运输能力均很弱,建议适量引入适宜在研究区生长并且对As元素富集能力较强的植物。     

Effect of microclimatic factors and tide on vertical migrations of the mangrove crab Sesarma leptosoma (Decapoda: Grapsidae)

The tree crab Sesarma leptosoma Hilgendorf migrates up the mangrove trunks twice a day, both in the morning and in the evening, leaving its refuge near the tree base to feed on fresh leaves. In spite of the 150 cm of tide excursion at the base of the trees, the timing of the migrations seems largely controlled by nontidal factors. The timing of the morning upward migration is controlled by the light level alone. The morning downward migration takes place as soon as the temperature rises and relative humidity falls, with no relationship to tidal cycle or light level. Only the evening upward flow seems primarily controlled by the tide, while the evening downward flow, which ends at twilight, seems to be related to the timing of the evening upward migration, to the tide and again to light levels. During the day, crabs abandon the canopy to avoid low relative humidity, usually coupled with the higher wind speeds, which would quickly dehydrate them. At night, crabs stop migrating, probably because their movements and orientation capability along the trunk and in the canopy are largely vision dependent. Nontidal factors have never previously been shown to influence the migratory behaviour of an intertidal crustacean species so extensively. Received: 14 June 1997 / Accepted: 17 July 1997     

Leaf choice by crustaceans in a mangrove forest in Queensland

The feeding behaviour of leaf eating crustaceans feeding on leaves shed by Avicennia marina, Bruguiera gymnorhiza and Rhizophora stylosa in the mangrove forest at Myora Springs, Queensland, Australia was studied between 1980 and 1984. Individual Sesarma erythrodactyla (carapace >9 mm long), one of the most abundant species of crabs in the forest, processed approximately half a leaf from any of the three species of mangroves in 24 h under laboratory conditions. of the amount of leaf material processed, 20% was lost from the mandibles due to sloppy feeding, 68% was egested as faeces and 12% converted into crab biomass. Crabs processed more leaf material at 30°C than at 20°C. S. erythrodactyla preferred leaves of A. marina to those of the other two species, probably because leaves of A. marina have a lower tannin and a higher nitrogen content. Of the other two species, B. gymnorhiza was preferred to R. stylosa. Among leaves of R. stylosa, S. erythrodactyla exerts a strong preference for aged rather than freshly fallen, and for thick rather than thin leaves. The mesofauna (carapace length <9.0 mm) which processed dead mangrove leaves comprised juveniles of S. erythrodactyla, the crab Ilyograpsus paludicola, the isopod Exosphaeroma alata and the amphipods Orchestia sp. and Melita sp. These species processed between 0.2 and 24.7 mg dry wt of a leaf per individual over a period of 4 d. Of this, 72 to 85% was egested as faeces. The significance of leaf eating crabs to nutrient cycling in mangrove forests is discussed. I conclude that leaf processing by crustaceans shortens the time span between leaf fall and consumption of leaf material by organisms. This may have the effect of conserving leaf biomass inside the mangrove forest.     

Forest structure of arid zone mangroves in relation to their physical and chemical environment in the western Gulf of Kachchh, Gujarat, Northwest coast of India

To understand natural and anthropic control of mangrove vegetation in the Gulf of Kachchh, a study was undertaken of its vegetation structure. Over 2 years (1999–2000) at three sites, mangrove vegetation was studied, including tree density, tree height, tree girth at breast height (GBH), canopy index, regeneration class and recruitment class, together with physico-chemical characteristics of water and sediment and the textural aspects of sediments. Reflecting the hot, arid hinterland of Gujarat, ambient temperatures and salinities are high in this macrotidal estuary, decreasing somewhat during the monsoon. The littoral soil supporting the mangrove is abundant in silty loam, silty clay and slity clay loam. The density of mature trees (Mangrove plants of GBH > 25 cm) ranged from 2088/ha to 3011/ha, the height of the trees ranged from 1.42 m to 9 m and the maximum mean GBH at all three sites was 33 cm, and the mean canopy indices ranged between 4.77 m² and 10.45 m². The maximum density of regeneration stages was 100,800/ha while that of recruitment stages was only 3,040/ha. While quite severely impacted by anthropic exploitation at one site, the mangrove ecosystem of Gulf of Kachchh was found to be mainly healthy and supporting associated organisms. The ecological and social role of the mangrove, and the potential for its future conservation are briefly discussed in the light of current legislation.