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1.
Mangrove forests are characterized by distinctive tree-height gradientsthat reflect complex spatial, within-stand differences in environmentalfactors,including nutrient dynamics, salinity, and tidal inundation, across narrowgradients. To determine patterns of nutrient limitation and the effects ofnutrient availability on plant growth and within-stand nutrient dynamics, weused a factorial experiment with three nutrient treatment levels (control, N,P)and three zones along a tree-height gradient (fringe, transition, dwarf) onoffshore islands in Belize. Transects were laid out perpendicular to theshoreline across a mangrove forest from a fringe stand along the seaward edge,through a stand of intermediate height, into a dwarf stand in the interior ofthe island. At three sites, three trees were fertilized per zone for 2yr. Although there was spatial variability in response, growth byR. mangle was generally nitrogen (N) -limited in thefringe zone;phosphorus (P) -limited in the dwarf zone; and, N- and/or P-limited in thetransition zone. Phosphorus-resorption efficiency decreased in all three zones,and N-resorption efficiency increased in the dwarf zone in response to Penrichment. The addition of N had no effect on either P or N resorptionefficiencies. Belowground decomposition was increased by P enrichment in allzones, whereas N enrichment had no effect. This study demonstrated thatessential nutrients are not uniformly distributed within mangrove ecosystems;that soil fertility can switch from conditions of N to P limitation acrossnarrow ecotonal gradients; and, that not all ecological processes respondsimilarly to, or are limited by, the same nutrient. 相似文献
2.
Mangrove ecosystems can be either nitrogen (N) or phosphorus (P) limited and are therefore vulnerable to nutrient pollution. Nutrient enrichment with either N or P may have differing effects on ecosystems because of underlying differences in plant physiological responses to these nutrients in either N- or P-limited settings. Using a common mangrove species, Avicennia germinans, in sites where growth was either N or P limited, we investigated differing physiological responses to N and P limitation and fertilization. We tested the hypothesis that water uptake and transport, and hydraulic architecture, were the main processes limiting productivity at the P-limited site, but that this was not the case at the N-limited site. We found that plants at the P-deficient site had lower leaf water potential, stomatal conductance and photosynthetic carbon-assimilation rates, and less conductive xylem, than those at the N-limited site. These differences were greatly reduced with P fertilization at the P-limited site. By contrast, fertilization with N at the N-limited site had little effect on either photosynthetic or hydraulic traits. We conclude that growth in N- and P-limited sites differentially affect the hydraulic pathways of mangroves. Plants experiencing P limitation appear to be water deficient and undergo more pronounced changes in structure and function with relief of nutrient deficiency than those in N-limited ecosystems. 相似文献
3.
Complex gradients in forest structure across the landscape of offshore mangrove islands in Belize are associated with nutrient
deficiency and flooding. While nutrient availability can affect many ecological processes, here we investigate how N and P
enrichment interact with forest structure in three distinct zones (fringe, transition, dwarf) to alter patterns of herbivory
as a function of folivory, loss of yield, and tissue mining. The effects of nutrient addition and zone varied by functional
feeding group or specific herbivore. Folivory ranged from 0 to 0.4% leaf area damaged per month, but rates did not vary by
either nutrient enrichment or zone. Leaf lifetime damage ranged from 3 to 10% of the total leaf area and was caused primarily
by the omnivorous tree crab Aratus pisonii. We detected two distinct spatial scales of response by A. pisonii that were unrelated to nutrient treatment, i.e., most feeding damage occurred in the fringe zone and crabs fed primarily
on the oldest leaves in the canopy. Loss of yield caused by the bud moth Ecdytolopha sp. varied by zone but not by nutrient treatment. A periderm-mining Marmara sp. responded positively to nutrient enrichment and closely mirrored the growth response by Rhizophora mangle across the tree height gradient. In contrast, a leaf-mining Marmara sp. was controlled by parasitoids and predators that killed >89% of its larvae. Thus, nutrient availability altered patterns
of herbivory of some but not all mangrove herbivores. These findings support the hypothesis that landscape heterogeneity of
the biotic and abiotic environment has species-specific effects on community structure and trophic interactions. Predicting
how herbivores respond to nutrient over-enrichment in mangrove ecosystems also requires an assessment of habitat heterogeneity
coupled with feeding strategies and species-specific behavior measured on multiple scales of response. 相似文献
4.
Photosynthetic performance and resource utilization of two mangrove species coexisting in a hypersaline scrub forest 总被引:6,自引:0,他引:6
In a hypersaline mangrove scrub forest in northern Florida, coexisting trees of Laguncularia racemosa and Avicennia germinans were either fertilized with nitrogen or phosphorus, or not fertilized (controls). We aimed to test whether nutrient additions differentially altered photosynthetic performance and resource utilization in these two species. In control trees, photosynthetic rates were higher in L. racemosa than A. germinans. However, leaf nitrogen concentrations were higher in A. germinans than L. racemosa. Avicennia germinans responded to fertilization with nitrogen by increasing leaf nitrogen concentrations and rates of photosynthesis such that they were equivalent to photosynthesis in L. racemosa. Laguncularia racemosa did not show a response to nitrogen additions. Neither species showed strong responses to phosphorus fertilization. Avicennia germinans had high photosynthetic water-use efficiency (photosynthesis/transpiration), but low photosynthetic nitrogen-use efficiency (photosynthesis/leaf nitrogen). In contrast, L. racemosa had comparatively low photosynthetic water use efficiency and high photosynthetic nitrogen use efficiency. Leaf level characteristics lead us to hypothesize that coexistence of A. germinans and L. racemosa should occur where nitrogen levels are low and salinity is moderate, or at least moderate for some period of the year. 相似文献
5.
Mangrove growth in New Zealand estuaries: the role of nutrient enrichment at sites with contrasting rates of sedimentation 总被引:4,自引:0,他引:4
Lovelock CE Feller IC Ellis J Schwarz AM Hancock N Nichols P Sorrell B 《Oecologia》2007,153(3):633-641
Mangrove forest coverage is increasing in the estuaries of the North Island of New Zealand, causing changes in estuarine ecosystem
structure and function. Sedimentation and associated nutrient enrichment have been proposed to be factors leading to increases
in mangrove cover, but the relative importance of each of these factors is unknown. We conducted a fertilization study in
estuaries with different sedimentation histories in order to determine the role of nutrient enrichment in stimulating mangrove
growth and forest development. We expected that if mangroves were nutrient-limited, nutrient enrichment would lead to increases
in mangrove growth and forest structure and that nutrient enrichment of trees in our site with low sedimentation would give
rise to trees and sediments that converged in terms of functional characteristics on control sites in our high sedimentation
site. The effects of fertilizing with nitrogen (N) varied among sites and across the intertidal zone, with enhancements in
growth, photosynthetic carbon gain, N resorption prior to leaf senescence and the leaf area index of canopies being significantly
greater at the high sedimentation sites than at the low sedimentation sites, and in landward dwarf trees compared to seaward
fringing trees. Sediment respiration (CO2 efflux) was higher at the high sedimentation site than at the low one sedimentation site, but it was not significantly affected
by fertilization, suggesting that the high sedimentation site supported greater bacterial mineralization of sediment carbon.
Nutrient enrichment of the coastal zone has a role in facilitating the expansion of mangroves in estuaries of the North Island
of New Zealand, but this effect is secondary to that of sedimentation, which increases habitat area and stimulates growth.
In estuaries with high sediment loads, enrichment with N will cause greater mangrove growth and further changes in ecosystem
function. 相似文献
6.
Naidoo G 《Annals of botany》2006,97(6):1095-1101
BACKGROUND AND AIMS: In Richards Bay, South Africa, Avicennia marina frequently exhibits a distinct productivity gradient, with tree height decreasing markedly from 6-10 m in the fringe zone to <1.5 m in the dwarf zone which is 120 m inland at a slightly higher elevation. In this investigation, soil physico-chemical conditions between fringe and dwarf A. marina were compared and the constraints imposed by any differences on mangrove ecophysiology and productivity determined. METHODS: Soil and plant samples were analysed for inorganic ions using spectrophotometry. Gas exchange measurements were taken with an infrared gas analyser and chlorophyll fluorescence with a fluorometer. Xylem psi was determined with a pressure chamber and chlorophyll content with a chlorophyll absorbance meter. RESULTS: In the dwarf site, soil salinity, total cations, electrical conductivity and soil concentrations of Na(+), K(+), Ca(2+), Mg(2+), Zn(2+), Mn(2+) and Cu(2+) were significantly higher than those in the fringe zone. Soil water potential and the concentration of soil P, however, were significantly lower in the dwarf site. In the leaves, Na(+) was the predominant ion and its concentration was 24 % higher in dwarf than fringe mangroves. Leaf concentrations of K(+), Ca(2+), Mg(2+), Mn(2+) and P, however, were significantly lower in dwarf mangroves. Photosynthetic performance, measured by gas exchange and chlorophyll fluorescence, was significantly reduced in the dwarf plants. CONCLUSIONS: The results suggest that hydro-edaphic factors contribute to high soil salinities, low water potentials, water stress and ion imbalance within tissues including P deficiency, which in interaction, contribute to dwarfing in Avicennia marina. 相似文献
7.
福建漳江口红树林区秋茄幼苗生长动态 总被引:12,自引:0,他引:12
通过福建漳江口红树林自然保护区内8个样方24个小样方人工种植600个秋茄胚轴,在3a时间内对秋茄胚轴建立、幼苗生长以及环境因子进行定期观测。研究结果表明:林缘空地的秋茄生长状况良好,白骨壤林内最不利于秋茄幼苗的生长。潮位、盐度、底质土壤理化因子不是造成该样地各样方间秋茄幼苗生长差异的主要原因。动物取食、光照状况以及种间竞争是限制秋茄生长的主要环境因子。秋茄胚轴在长根前易于随潮水漂走,底质土壤中自骨壤致密的根系抑制了秋茄胚轴的定植,导致白骨壤林内秋茄幼苗漂走的数量最多。昆虫和螃蟹等动物的取食是导致林内已经固着生长的秋茄幼苗大量死亡的最主要原因,而林外被取食的幼苗个体极少。此后秋茄幼苗能否继续成长,主要取决于幼苗所接受到的光照条件。3a后,在荫蔽的树冠下,秋茄幼苗无法存活;而在林外,秋茄幼苗已经长成幼树。在林外滩涂上迅速生长的互花米草,也将影响秋茄幼苗的更新和生长。 相似文献
8.
KATHERINE C. MARTIN DAN BRUHN CATHERINE E. LOVELOCK ILKA C. FELLER JOHN R. EVANS MARILYN C. BALL 《Plant, cell & environment》2010,33(3):344-357
Effects of salinity and nutrients on carbon gain in relation to water use were studied in the grey mangrove, Avicennia marina, growing along a natural salinity gradient in south‐eastern Australia. Tall trees characterized areas of seawater salinities (fringe zone) and stunted trees dominated landward hypersaline areas (scrub zone). Trees were fertilized with nitrogen (+N) or phosphorus (+P) or unfertilized. There was no significant effect of +P on shoot growth, whereas +N enhanced canopy development, particularly in scrub trees. Scrub trees maintained greater CO2 assimilation per unit water transpired (water‐use efficiency, WUE) and had lower nitrogen‐use efficiency (NUE; CO2 assimilation rate per unit leaf nitrogen) than fringe trees. The CO2 assimilation rates of +N trees were similar to those in other treatments, but were achieved at lower transpiration rates, stomatal conductance and intercellular CO2 concentrations. Maintaining comparable assimilation rates at lower stomatal conductance requires greater ribulose 1·5‐bisphosphate carboxylase/oxygenase activity, consistent with greater N content per unit leaf area in +N trees. Hence, +N enhanced WUE at the expense of NUE. Instantaneous WUE estimates were supported by less negative foliar δ13C values for +N trees and scrub control trees. Thus, nutrient enrichment may alter the structure and function of mangrove forests along salinity gradients. 相似文献
9.
竞争和非生物胁迫影响处于地理分布边界的红树植物的个体大小
关于红树植物竞争的研究大多局限于幼苗和人工林。我们首次对天然红树林中成年红树的种内竞争进行了控制实验研究,旨在检验竞争和非生物因子在决定红树植物个体大小中的相对重要性。研究样 地位于靠近红树林地理分布边界的美国德克萨斯州阿兰萨斯港(Port Aransas)附近区域。该区域的红树林由“灌丛”状的黑红树(萌芽白骨壤,Avicennia germinans)单一物种组成。我们对10个样方中原生红树 林进行疏伐,形成系列红树林覆盖度梯度,在2013–2019年期间观测各样方中红树植物的生长指标,量化分析红树林覆盖度对红树植物生长的影响;并于2019年调查了红树林的冠层高度。研究结果表明,在该研究期间,红树植物的相对生长速率随着红树林覆盖度的增加而降低,100%红树林覆盖度样方中的红 树植物大小几乎没有增长,说明它们已经达到了该红树林密度条件下的最大尺寸。在红树林覆盖度降低 的样方中,株高明显增加,在红树林覆盖度为11%的样方中,红树植物株高增加了约52%。对比临水岸 边和林内两种生境中的样方,处于临水岸边生境的红树林冠层高度比处于林内生境的高约30%,且这两 种生境的红树林冠层高度均随红树林覆盖度的增加而降低。叶片叶绿素含量和冠层光截留量的测定数据 显示,该区域红树植物的生长也受到氮限制的影响。由此表明,处于地理分布边界的“灌丛”状红树林一 方面受到营养的限制,另一方面红树植物种内个体间仍存在较为强烈的竞争,且种内竞争对红树植物生长的影响较该红树林内非生物生境因子更为重要。 相似文献
10.
Holmer M. Andersen F.Ø. Holmboe N. Kristensen E. Thongtham N. 《Wetlands Ecology and Management》2001,9(2):141-158
Benthic primary production and nutrient dynamics were examined along a transect in the Bangrong mangrove forest in Thailand.
Six stations were established extending from a high-intertidal site within the mangrove forest to low-intertidal flats and
seagrass beds in front of the mangrove forest. Benthic processes (O2 and CO2 fluxes) and nutrient dynamics (mineralization, sediment-water fluxes, pore water and sediment pools) were measured under
light and dark conditions during wet and dry seasons over a 2-yr period. The sediments were mostly autotrophic, only the mangrove
forest sites were net heterotrophic during the wet season. Maximum daily net primary production was found at the non-vegetated
tidal flats (40–75 mmol O2 m-2d-1), where light and nutrient availability were highest. The variation in benthic mineralization along the transect was minor
(1.6–4.3 mmol CO2 m-2h-1) and did not reflect the large changes inorganic matter content (organic carbon: 0.7–4.2% DW) and quality (C:N ratio varied
from 25 to 100), suggesting that the mineralizable pool of organic matter was of similar magnitude at all sites. There was
only minor seasonal variation in rates of mineralization. The net primary production showed more variation with lower rates
in the mangrove forest (reduced with 74%) and higher rates at the tidal flats (increased with 172%) and in the seagrass beds
(increased with 228%) during the wet season. The nutrient pools and fluxes across the sediment-water interface were generally
low along the transect, and the sediments were efficient in retaining nitrogen in the nutrient limited mangrove/seagrass environment.
Pools and fluxes of phosphorus were generally very low suggesting that benthic primary production was phosphorus limited along
the transect.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
11.
Effects of artificial grassland establishment on soil nutrients and carbon properties in a black-soil-type degraded grassland 总被引:2,自引:0,他引:2
Despite a growing knowledge of nutrient limitation for mangrove species and how mangroves adapt to low nutrients, there is scant information about the relative importance of N:P ratio and leaf phenolics variability in determining nutrient conservation. In this study, we evaluated possible nutrient conservation strategies of a mangrove Rhizophora stylosa under nutrient limitation. 1. The leaf nutrient concentrations of R. stylosa changed with season, with the highest N concentration in winter and the highest P concentration in spring for both mature and senescent leaves. Leaf N and P concentrations decreased significantly during leaf senescence. Based on N:P ratios R. stylosa forest was N-limited. Accordingly, the nitrogen resorption efficiency (NRE) was significantly higher than phosphorus resorption efficiency (PRE) for the R. stylosa leaves during leaf senescence. The NRE and PRE both reached the highest in the autumn. Average N and P concentrations in the senescent leaves were 0.15% and 0.06% for R. stylosa, respectively, indicating a complete resorption of N and an incomplete resorption of P. There was a significant negative correlation between nitrogen resorption proficiency (NRP) and NRE, meanwhile phosphorus resorption proficiency (PRP) and PRE correlation was also highly significantly. 2. R. stylosa leaves contained relatively high tannin level. Total phenolics, extractable condensed tannins and total condensed tannins contents increased during leaf senescence, and changed between seasons. The lowest concentrations of total phenolics, extractable condensed tannins and total condensed tannins occurred in summer, total phenolics concentrations were inversely related to nitrogen or phosphorus concentrations. 3. Our results confirmed that resorption efficiency during leaf senescence depends on the type of nutrient limitation, and NRE was much higher than PRE under N-limited conditions. R. stylosa forest developed several nutrient conservation strategies in the intertidal coastline surroundings, including high nitrogen resorption efficiency, low nutrient losses and high tannins level. 相似文献
12.
Propagules of Kandelia candel collected from the Zhangjiang estuary were planted in mangrove habitats along the intertidal gradient. The rooting rates of K. candel propagules varied spatially. The lowest rate occurred in Avicennia marina forest (69.7%). The rates were higher in K. candel forest (90.0%), at the fringe of the mangrove forest (89.3%) and on the bare tidal flat outside the mangrove forest (82.7%). After one year, the survival rates of seedlings planted under A. marina forest, K. candel forest, at the fringe of the mangrove forest, and on the bare tidal flat were 13.7%, 54.7%, 76.0%, and 34.7%, respectively. Among the surviving K. candel seedlings, those at the fringe of the mangrove forest and on the bare tidal flat had greater height, stem diameter, leaf number, leaf area, and biomass than those under A. marina and K. candel forests. These results demonstrated that establishment and growth of K. candel seedlings occurred successfully at the fringe of the mangrove forest, but were the worst under A. marina forest. The performance of K. candel seedlings was independent of physico-chemical characters of sediment. However, interspecies competition, propagule predation by insects and crabs, and the incident light had significant effects on seedling survival and growth. 相似文献
13.
Nutrient over-enrichment is a major threat to marine environments, but system-specific attributes of coastal ecosystems may
result in differences in their sensitivity and susceptibility to eutrophication. We used fertilization experiments in nitrogen
(N)- and phosphorus (P)-limited mangrove forests to test the hypothesis that alleviating different kinds of nutrient limitation
may have different effects on ecosystem structure and function in natural systems. We compared a broad range of ecological
processes to determine if these systems have different thresholds where shifts might occur in nutrient limitation. Growth
responses indicated N limitation in Avicennia germinans (black mangrove) forests in the Indian River Lagoon (IRL), Florida, and P limitation at Twin Cays, Belize. When nutrient
deficiency was relieved, A. germinans grew out of its stunted form by increasing wood relative to leaf biomass and shoot length relative to lateral growth. At
the P-limited site, P enrichment (+P) increased specific leaf area, N resorption, and P uptake, but had no effect on P resorption.
At the N-limited site, +N increased both N and P resorption, but did not alter biomass allocation. Herbivory was greater at
the P-limited site and was unaffected by +P, whereas +N led to increased herbivory at the N-limited site. The responses to
nutrient enrichment depended on the ecological process and limiting nutrient and suggested that N- versus P-limited mangroves
do have different thresholds. +P had a greater effect on more ecological processes at Twin Cays than did +N at the IRL, which
indicated that the P-limited site was more sensitive to nutrient loading. Because of this sensitivity, eutrophication is more
likely to cause a shift in nutrient limitation at P-limited Twin Cays than N-limited IRL. 相似文献
14.
Influence of nutrients,disturbances and site conditions on carbon stocks along a boreal forest transect in central Canada 总被引:4,自引:0,他引:4
The interacting influence of disturbances and nutrient dynamics on aboveground biomass, forest floor, and mineral soil C stocks was assessed as part of the Boreal Forest Transect Case Study in central Canada. This transect covers a range of forested biomes–-from transitional grasslands (aspen parkland) in the south, through boreal forests, and into the forested subarctic woodland in the north. The dominant forest vegetation species are aspen, jack pine and spruce. Disturbances influence biomass C stocks in boreal forests by determining its age-class structure, altering nutrient dynamics, and changing the total nutrient reserves of the stand. Nitrogen is generally the limiting nutrient in these systems, and N availability determines biomass C stocks by affecting the forest dynamics (growth rates and site carrying capacity) throughout the life cycle of a forest stand. At a given site, total and available soil N are determined both by biotic factors (such as vegetation type and associated detritus pools) and abiotic factors (such as N deposition, soil texture, and drainage). Increasing clay content, lower temperatures and reduced aeration are expected to lead to reduced N mineralization and, ultimately, lower N availability and reduced forest productivity. Forest floor and mineral soil C stocks vary with changing balances between complex sets of organic carbon inputs and outputs. The changes in forest floor and mineral soil C pools at a given site, however, are strongly related to the historical changes in biomass at that site. Changes in N availability alter the processes regulating both inputs and outputs of carbon to soil stocks. N availability in turn is shaped by past disturbance history, litter fall rate, site characteristics and climatic factors. Thus, understanding the life-cycle dynamics of C and N as determined by age-class structure (disturbances) is essential for quantifying past changes in forest level C stocks and for projecting their future change. 相似文献
15.
Ilka C. Feller Anne H. Chamberlain Cyril Piou Samantha Chapman Catherine E. Lovelock 《Ecosystems》2013,16(7):1203-1215
Ecosystems in the tropics are predicted to have stronger responses to nutrient enrichment, greater diversity, and more intense biotic interactions than in temperate areas. Mangrove forests, which occur across a broad biogeographic range from warm temperate to tropical, provide a unique opportunity to test these hypotheses by investigating the responses of herbivores to nutrient enrichment in temperate versus tropical latitudes. Mangroves are complex intertidal ecosystems with spatial differences in structure and diversity along tidal gradients and are threatened globally by human activities including nutrient over-enrichment. In this study, we used long-term fertilization experiments at the Indian River Lagoon, FL; Twin Cays, Belize; and Bocas del Toro, Panamá to determine how increased nutrients impact herbivore abundance and herbivory of Rhizophora mangle at the tree, forest, and regional scales. At these locations, which span approximately 2185 km and 18.4º of latitude, we fertilized individual trees with one of three treatments (Control, +N, +P) in two zones (fringe, scrub) along transects perpendicular to the shoreline and measured their responses for 4 years. Herbivory was measured as folivory, loss of yield, and tissue mining. Although nutrient enrichment altered plant growth, leaf traits, and nutrient dynamics, these variables had little effect on folivory at any location. Our results did not support the prediction that herbivory and per capita consumption are greatest at the most tropical location. Instead, folivory was highest at the most temperate location and lowest at the intermediate location. Folivory was generally higher in the fringe than in the scrub zone, but the pattern varied by location, herbivore, and nutrient treatment. Folivory by a dominant herbivore, Aratus pisonii, decreased from the highest to the lowest latitude. Our data suggest that factors controlling population dynamics of A. pisonii cascade to the mangrove canopy, linking herbivory to crab densities. 相似文献
16.
The semi-diurnal tidal regime (≥2 m) in the Paria Gulf on the Atlantic coast of Venezuela, and the flat landscape of the region,
allow the penetration for tens of km of marine waters into the rivers draining the northeastern coastal plain of the country.
The levels of salinity, tidal flooding, and sedimentation decrease perpendicularly from the river channel toward the back
swamps. The vegetation varies sequentially from fringe mangroves along the river margins, to back swamps containing forests
dominated by Pterocarpus officinalis, herbaceous communities of Lagenocarpus guianensis, and palm swamps with Mauritia flexuosa, Chrysobalanus icaco, and Tabebuia spp. This environmental structure was used to test the hypotheses that: (a) mangrove distribution is strongly associated
with salinity of interstitial water, and (b) they occupy areas where tidal influence and sediment dynamics determine a relatively
open N cycle. Analyses of soil, water, and plants along a 1.5 km transect located near the confluence of the Guanoco and San
Juan Rivers (Sucre and Monagas States, Venezuela) revealed that: (a) conductivity decreased from 11 to 0.2 mmhos cm−1 from the river fringe to the internal swamp, whereas Na in the same stretch decreased from 100 to 2 μM; (b) average leaf
tissue concentrations of Na, P, and N decreased significantly along the transect; (c) P. officinalis showed a large Na-exclusion capacity indicated by positive K/Na ratios from 8 to 200, and Crinum erubescens counteracted Na by accumulating K above 1,000 mmol kg−1; (d) leaves varied widely in δ 13C (−25.5 to −32‰) and δ 15N (4 to −10.5‰) values. Samples were aggregated according to soil carbon content corresponding to those of the mangrove forest
belt (5–28 mol C kg−1; 0–650 from river fringe) and those of the back swamps (40–44 mol C kg−1; 700–1,500 m from river fringe). The concentrations of Na, P, and N (in mmol kg−1) and δ 15N values (in ‰) were significantly higher in the mangrove forest compared to the back swamp (Na 213 vs. 88; P 41 vs. 16; N
1,535 vs. 727; δ 15N 1.5 vs. −3.7), indicating that the fringe forest was not nutrient limited. These results support the hypotheses that mangroves
are restricted to the more-saline sections of the transect, and that the fringe forest has a more open N cycle, favoring 15N accumulation within the system. 相似文献
17.
The growth of Kandelia candel seedlings in mangrove habitats of the Zhangjiang estuary in Fujian, China
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Propagules of Kandelia candel collected from the Zhangjiang estuary were planted in mangrove habitats along the intertidal gradient. The rooting rates of K. candel propagules varied spatially. The lowest rate occurred in Avicennia marina forest (69.7%). The rates were higher in K. candel forest (90.0%), at the fringe of the mangrove forest (89.3%) and on the bare tidal flat outside the mangrove forest (82.7%). After one year, the survival rates of seedlings planted under A. marina forest, K. candel forest, at the fringe of the mangrove forest, and on the bare tidal flat were 13.7%, 54.7%, 76.0%, and 34.7%, respectively. Among the surviving K. candel seedlings, those at the fringe of the mangrove forest and on the bare tidal flat had greater height, stem diameter, leaf number, leaf area, and biomass than those under A. marina and K. candel forests. These results demonstrated that establishment and growth of K. candel seedlings occurred successfully at the fringe of the mangrove forest, but were the worst under A. marina forest. The performance of K. candel seedlings was independent of physico-chemical characters of sediment. However, interspecies competition, propagule predation by insects and crabs, and the incident light had significant effects on seedling survival and growth. 相似文献
18.
Aor Pranchai Michael Jenke Juliane Vogt Uwe Grueters Lin Yue Ulf Mehlig Moirah Machado de Menezes Sven Wagner Uta Berger 《Wetlands Ecology and Management》2018,26(2):139-150
The global effort to rehabilitate and restore destroyed mangrove forests is unable to keep up with the high mangrove deforestation rates, which exceed the average pace of global deforestation. Although facilitation theory presents new possibilities for the restoration of heavily degraded mangrove sites, knowledge of tree–tree interactions in stressed mangrove forest ecosystems is too limited to utilize facilitation appropriately. The aim was to determine the mode of local interaction among stressed mangrove trees by investigating the effect of clustering on tree size and crown morphology under contrasting stand densities. The study was conducted in a dwarf Avicennia germinans forest in Northern Brazil, in which tree growth is limited by infrequent inundation and high pore-water salinity. Autoregressive regression, Voronoi tessellation and spatial point pattern statistics were used to address the spatial processes underlying tree interaction. Under low stand density (1.2 trees m?2) dwarf trees which grew in clustered cohorts of A. germinans had a less stunted crown morphology revealing the dominance of a positive neighborhood influence among plants. In contrast, dwarf trees in the denser forest stand (2.7 trees m?2) were interacting competitively as indicated by the more negative effect of neighbors on crown morphology and size. The shift from facilitative to competitive interactions is an important feature of mangrove forest regeneration under harsh environmental conditions. If mangrove trees are unable to regenerate naturally on severely degraded sites, intraspecific facilitation could be used to assist regeneration by planting seedlings in clusters and not evenly spaced. 相似文献
19.
Soil-plant interactions in a neotropical mangrove forest: iron, phosphorus and sulfur dynamics 总被引:5,自引:0,他引:5
We examined soil porewater concentrations of sulfate, alkalinity, phosphorus, nitrogen, and dissolved organic carbon and
solid phase concentrations of pyrite in relation to mangrove species distributions along a 3.1-km-long transect that traversed
a 47.1-km2 mangrove forest in the Dominican Republic. Iron, phosphorus, and sulfur dynamics are closely coupled to the activity of sulfate-reducing
bacteria, the primary decomposers in anoxic soils of mangrove ecosystems. Patterns in the chemistry data suggested that sulfate
reduction rates and storage of reduced sulfur were greater in the inland basin forest dominated by Laguncularia racemosa than the Rhizophora mangle dominated forest of the lower tidal region. The distribution of Laguncularia was significantly correlated with concentrations of total phosphorus (r= 0.99) and dissolved organic carbon (r= 0.86), alkalinity (r= 0.60), and the extent of sulfate depletion (r= 0.77) in the soil porewater and soil pyrite concentrations (r= 0.72) across the tidal gradient. Leaf tissue chemistry of Laguncularia was characterized by lower C:N and C:P ratios that could fuel the higher rates of decomposition in the Laguncularia-dominated forest. We suggest that a plant-soil-microbial feedback contributes to the spatial patterning of vegetation and
soil variables across the intertidal zone of many mangrove forest communities.
Received: 28 May 1997 / Accepted: 23 January 1998 相似文献
20.
为探究广西乐业大石围天坑森林群落的C、N、P养分循环特征,比较了天坑内外森林群落的植物叶片-凋落物-土壤C、N、P含量及其化学计量比,采用相关性分析和冗余分析等统计方法研究其内在联系和相互影响。结果表明,与天坑外部森林相比,天坑内部森林植物叶片和凋落物呈现出C低N、P高,土壤为C、N低P高的格局。植物叶片C:N、C:P与凋落物C、N:P显著正相关,植物叶片C与土壤P显著负相关;天坑外部森林的植物叶片N、N:P与土壤N:P显著负相关,植物叶片C:N与土壤C、C:N显著正相关,说明天坑森林内部凋落物的C、P养分可能主要来源于植物叶片,而天坑外部森林的植物叶片C、N主要来自土壤。土壤C:N:P对植物叶、凋落物的C:N:P变化的解释率分别为90.7%和50.6%,其中土壤P对植物叶和凋落物的C:N:P计量特征变化的解释度最高,坑内生境植物对P含量变化更为敏感、坑外植物对于N含量变化更为敏感,表明天坑内部森林可能是P素受限位点、天坑外部森林是N素受限位点。喀斯特天坑内部森林和外部森林植物叶-凋落物-土壤的C:N:P的差异和联系,体现了天坑内外森林群落的养分循环特征和植物群落的适应性。 相似文献