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Мартынова-Ван Клей Александра, Монтез Рамонд Д., Налян Армен, Саенз Даниэл ЯВЛЯЕТСЯ ЛИ УГРОЗОЙ БЫСТРОЕ ГНИЕНИЕ ОСТАТКОВ ЛИСТЬЕВ ...
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УДК 574
ЯВЛЯЕТСЯ ЛИ УГРОЗОЙ БЫСТРОЕ ГНИЕНИЕ ОСТАТКОВ ЛИСТЬЕВ ИНВАЗИВНОГО САЛЬНОГО ДЕРЕВА (TRIADICA SEBIFERA) ДЛЯ ВОДНО-БОЛОТНЫХ МИКРОБИАЛЬНЫХ
СООБЩЕСТВ ВОСТОЧНОГО ТЕХАСА?
© 2016
Мартынова-Ван Клей Александра, Ph.D., профессор Монтез Рамонд Д. Налян Армен
Государственный Университет им. Стивена Ф Остина, Накогдочес, Техас (США)
Саенз Даниэл Государственная Служба Леса (США)
Аннотация. Глобальное изменение климата и антропогенная деятельность способствуют перемещению растений. Завоевание растениями новых мест обитания часто имеют негативное влияние на разнообразие и функции экосистем и ставят под угрозу сложившиеся экономические, социальные мероприятия. Инвазивное древесное растение Сальное дерево (Triadica sebifera (L.) Small), уже захватило большую часть юго-восточного региона США, где оно находится вне конкуренции с местными породами деревьев. Было показано, что остатки листьев Сального дерева негативно влияют на развитие потомства некоторых амфибий за счет снижения концентрации растворенного кислорода и рН. Мы полагаем, что вещества, высвобождаемые из опавших листьев, могут влиять и на микробные сообщества в водно-болотных местах. Предварительные эксперименты показали, что скорость распада листьев Сального дерева быстрее, чем у местных видов. Используя массово-параллельное секвенирование микробных сообществ, были зарегистрированы изменения в бактериальных сообществах в присутствии остатков листьев Сального дерева.
Ключевые слова. Сальное дерево (Triadica sebifera), инвазивные виды, бактериальные сообщества, устойчивость.
IS RAPID DECAY OF INVASIVE CHINESE TALLOW (TRIADICA SEBIFERA) LEAF LITTER A THREAT TO WETLAND MICROBIAL COMMUNITIES IN EAST TEXAS?
© 2016
Martynova-Van Kley Alexandra, Ph.D., professor Montez Ramond D. Nalian Armen
Stephen F. Austin State University, Nacogdoches, Texas (USA) Saenz Daniel US Forest Service, Nacogdoches, Texas (USA)
Abstract. Global climate change and anthropogenic activity have facilitated the movement of plants from their usual habitat to non-native environments. These invasions have often negative effect on the diversity and function of their newly-adapted ecosystems and threaten established economic, social, and recreational activities including hunting and fishing. The invasive woody plant, Chinese tallow (Triadica sebifera (L.) Small), has already invaded much of the south eastern region of the US where it is out-competing native tree species and changing ecosystem diversity in variety of habitats. Leaf litter from the Chinese tallow has been shown to be detrimental in the hatching success of amphibian eggs in wetland environments by lowering dissolved oxygen concentrations and pH. We suggest that nutrients released from the leaf litter may affect microbial community structure and function. Preliminary decay rate experiments show that Chinese tallow leaf litter has a faster decay rate than native species. Using massive parallel sequencing analysis of microbial communities we observed changes in the bacterial community over time in presence of tallow leaf litter.
Keywords. Chinese tallow (Triadica sebifera), invasive species, bacterial communities, sustainability.
INTRODUCTION. The negative effects of Chinese tallow in a variety of habitats create a great concern over the presence of this non-native in southeastern US and East Texas ecosystems. A shift in microbial community composition due to the chemical changes associated with the tallow leaf decay is expected. These effects can pose a threat to aquatic habitat diversity, food chain dynamics, and overall ecosystem function. This in turn threatens to disrupt established social, economic, and recreational activities such as hunting, fishing, and ecotourism. The leaf litter from the invasive Chinese tallow tree is known to have an effect on amphibian populations residing in aquatic zones (Cotton et al., 2012; Adams and Saenz, 2012; Saenz, 2013). The presence of Chinese tallow in wetland habitats generates the potential for food web and trophic structure disruption in aquatic environments (Zedler and Kercher, 2004).
Shifts in microbial community structure can contribute to changes in biogeochemical cycles. The Chinese tallow can have effects locally that can ripple through the ecosystem, decreasing diversity, and changing community structure in both aquatic and terrestrial environments. Wetlands, transitional between terrestrial and aquatic systems, may also be affected by the presence of Chinese tallow. Such invasion may not only affect biodiversity and ecosystem function, but also the human use and enjoyment of wetlands (Zedler and Kercher, 2004). In particular, Hunting and fishing and related expenditures such as travel, lodging, equipment, ammunition, and bait provide a major contribution to the local economies of rural areas in east Texas and the southeastern
US; disruptions to these activities resulting from invasive species are a major economic impact.
Wetlands are special habitats that do not share the characteristics of terrestrial or aquatic ecosystems and can provide society and the biosphere with beneficial ecosystem functions and human services. Wetlands and their unique habitats support extensive food chains that include a rich diversity of flora and fauna and are critical components of the biogeochemical cycling. The biogeochemistry of wetlands features a combination of chemical transformations and chemical transport processes not shared by many other ecosystems. These processes result not only in changes in the chemical forms of materials but also in the spatial movement of materials within the wetlands, as in water - sediment exchange and plant uptake, and with surrounding ecosystems, as in organic exports. In addition, natural wetlands are also key component of the water cycle, playing critical roles in maintaining the general health of rivers, estuaries, and coastal waters (Kandasamy and Vigneswaran, 2008).
Many of biogeochemical transformations in wetlands are mediated by microbial populations. If Chinese Tallow litter contributes to changes in microbial community structure, then it may alter biogeochemical cycles in those unique systems.
Pattison and Mack (2008) suggest that the invasion range of Chinese tallow may be restricted to wet and warm climates. Figure 1 shows the extent of Chinese tallow in the southeastern US, along with normal annual precipitation. Figure 1 shows that precipitation is a dominant factor in the
общая Мартынова-Ван Клей Александра, Монтез Рамонд Д., Налян Армен, Саенз Даниэл
биология ЯВЛЯЕТСЯ ЛИ УГРОЗОЙ БЫСТРОЕ ГНИЕНИЕ ОСТАТКОВ ЛИСТЬЕВ ...
distribution range of Chinese tallow, with the higher concentrations of counties invaded having annual precipitation ranges from 40 to 70 inches, yearly. The range and invasive ability of the Chinese tallow also seems to be limited by cold temperatures (Bruce et al., 1997; Wang et al., 2011). Many of the wetlands of the United States reside within this region and are already infested with Chinese tallow (Zedler and Kercher, 2004). These wetlands are at risk, with the annual loading of tallow leaves that are associated with rapid decay rate, secondary chemicals and chemical alterations. The formation of monoculture stands can produce tallow leaf litter concentrations of 1.27 g of leaf litter/L of water (Leonard, 2008), with concentrations suggested to be much higher in stands in and around wetlands as these stands are often very dense (Adams and Saenz, 2012).
The objectives of this study are to determine the proximate cause(s) of these chemical changes when tallow leaf litter is present and to determine if microbial communities exposed to Chinese tallow leaf litter differ from those in the presence of the litter of two native species (Loblolly pine and Water oak).
METHODS. Leaf litter from three tree species Loblolly pine, (Pinus taeda), Water Oak (Quercus nigra), and Chinese Tallow (Triadica sebifera) were collected and submerged into 80L pools of well water ( mesocosms ) for 16 weeks (Saenz et al., 2013). Forty mesocosms (10 per each leaf species plus control) were set at the Stephen F. Austin Experimental forest near Nacogdoches, Texas, USA during March-June 2015 and were exposed to uniform light and weather conditions. 160 grams of dried leaf litter were added to each pool to create a litter concentration of 2 g/L (Adams and Saenz, 2012). A comparative tissue and water chemistry analysis between Chinese tallow and native tree species was done by Soil, Water, and Plant Analysis Laboratory at SFASU. ANOVA, followed by Tukey-Kramer's test were used to determine statistical differences in the results of the mesocosm, tissue, solution, and decay rate data. Microbial community composition was determined by sequencing 16S rRNA gene sequencing using Illumina method for massive parallel sequencing. The sequences were identified with RDP classifier and the community composition was analyzed with ordination methods such as NMDS, PCA, CCA.
RESULTS AND DISCUSSION. Tallow leaf litter had significant effects on dissolved oxygen and pH (Figure 2) compared to native species. After a 48 hour period tallow litter caused dissolved oxygen to decrease to a concentration of 3.45 mg/L, while the oak and pine species litter had little effect. Differences in leaf litter quality were also found between litter species.
Sequencing and ordination methods provided insight on the effects of leaf litter on microbial communities. Bacterial richness decreased after 48 hr(Figure 3).
Although all the leaf types displayed the decrease in bacterial richness, these changes were only marginally significant. In addition after the 16 week period the bacterial richness increased approaching the original levels.
Nonmetric Multidimensional Scaling (NMDS) results show that the time period was the largest factor contributing to microbial community structure differences (Figure 4). The samples formed three distinct clusters (shown as spiders) with only few control samples overlapping neighboring clusters. The significant factors corresponding with the changes in bacterial communities are shown in the plot and included salinity, pH, temperature, etc. The initial and the 48hr clusters occupy the upper portion of the plot; these samples have higher levels of salinity, DO and oRp. The 16 week cluster (bottom left) is associated with higher levels of pH, turbidity and temperature. The percentage of dissolved oxygen (DO.1) is the only factor which can be associated with the difference between 48hr and the rest of the clusters.
Thus deleterious effects reported in literature regarding invasive Chinese tallow leaves according to our study cannot be readily linked to changes in structure of microbial communities. Our study suggests that the differences in Карельский научный журнал. 2016. Т. 5. № 3(16)
microbial communities in initial, 48hr and 16week samples are much larger than the differences between leaf species. In natural systems perhaps simultaneous presence of leaves from different species could have synergistic effects; however we noticed no significant sample separations by leaf species within the clusters. Although the effect of Chinese tallow on fungal communities still remains to be studied. In natural systems; this could seriously impact fish populations and other wetland functions and thus impact economic and recreational activities such as fishing and hunting that are important for many areas of east Texas and the southeastern US
Figure 1. Annual average precipitation ranges of the US (1981-2013) and the current extent of Chinese tallow invasion in the southeastern portion of the US.
A
—»—Control —■—Oak —*—Pine —*—Tallow
^V* ^ ^ ^ ////////
Time Period
В
Time Periuii
Figure 2. A: Dissolved oxygen and B: pH for each litter type during 16 weeks of decay.
Figure 3. Bacterial richness for each litter type all three time periods.
Мартынова-Ван Клей Александра, Монтез Рамонд Д., Налян Армен, Саенз Даниэл ЯВЛЯЕТСЯ ЛИ УГРОЗОЙ БЫСТРОЕ ГНИЕНИЕ ОСТАТКОВ ЛИСТЬЕВ ...
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Figure 4. NMDS of bacterial community structure for all samples, in all three time periods, and the significant physico-chemical parameters, the circles represents the samples: black - control; green - pine; blue - tallow; red -oak:
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2. Bruce, Katherine and Guy N Cameron. Introduction, Impact on Native Habitats, and Management of a Woody Invader, the Chinese tallow tree, (Sapium sebiferum) // Nat. area. J. 1997. V. 17. No. 3. P. 255-260.
3. Cotton, Taylor. B., Matthew A. Kwiatkowski, Danial Saenz, and Michael Collyer. Effects of an invasive plant, Chinese tallow (Triadica sebifera), on development and survival of anuran larvae / J. Herpetol., 2012. V. 46. No. 2. P. 186-193.
4. Kandasamy, Jaya and Saravanamuhu Vignswaran. Constructed Wetlands / New York: Nova Science publishers. Inc. 2008. 136 p.
5. Leonard, Norman. The effects of the invasive exotic Chinese tallow tree (Triadica sebifera) on amphibians and aquatic invertebrates. / Theses Dissertation. 2008. University of New Orleans. 76 p.
6. Pattison, R.R. and Mack, R.N. Potential distribution of the invasive tree Triadica sebifera (Euphorbiaceae) in the United States: evaluating CLIMEX predictions with field trials. // Global Change Biol. 2008. V. 14. P. 813-826.
7. Saenz, Daniel, Erin M. Fucik, and Matthew A. Kwiatkowski. Synergistic effects of the invasive Chinese Tallow (Triadica sebifera) and climate change on aquatic amphibian survival. // Ecol. Evol. 2013. V. 3. No. 14. P. 4828-4840.
8. Zedler, J. B. and S. Kercher. Causes and Consequences of Invasive Plants in Wetlands: Opportunities, Opportunists, and Outcomes. / Crit. Rev. Plant Sci. 2004. V. 23 No. 5. P. 431-452.
9. Wang, H.-H., W. E. Grant, T. M. Swannack, J. Gan, W. E. Rogers, T. E. Koralewski, et al.. Predicted range expansion of Chinese tallow tree (Triadica sebifera) in forestlands of the southern United States. // Diver. Distrib. .2011. No. 17. P. 552-565.
