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资源利用效率解释了澳大利亚北部资源匮乏的稀树草原上禾本科杂草的入侵现象。

Resource-use efficiency explains grassy weed invasion in a low-resource savanna in north Australia.

作者信息

Ens Emilie, Hutley Lindsay B, Rossiter-Rachor Natalie A, Douglas Michael M, Setterfield Samantha A

机构信息

Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, NT Australia ; Department of Environmental Sciences, Macquarie University, North Ryde, NSW Australia.

Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, NT Australia.

出版信息

Front Plant Sci. 2015 Aug 4;6:560. doi: 10.3389/fpls.2015.00560. eCollection 2015.

Abstract

Comparative studies of plant resource use and ecophysiological traits of invasive and native resident plant species can elucidate mechanisms of invasion success and ecosystem impacts. In the seasonal tropics of north Australia, the alien C4 perennial grass Andropogon gayanus (gamba grass) has transformed diverse, mixed tree-grass savanna ecosystems into dense monocultures. To better understand the mechanisms of invasion, we compared resource acquisition and usage efficiency using leaf-scale ecophysiological and stand-scale growth traits of A. gayanus with a co-habiting native C4 perennial grass Alloteropsis semialata. Under wet season conditions, A. gayanus had higher rates of stomatal conductance, assimilation, and water use, plus a longer daily assimilation period than the native species A. semialata. Growing season length was also ~2 months longer for the invader. Wet season measures of leaf scale water use efficiency (WUE) and light use efficiency (LUE) did not differ between the two species, although photosynthetic nitrogen use efficiency (PNUE) was significantly higher in A. gayanus. By May (dry season) the drought avoiding native species A. semialata had senesced. In contrast, rates of A. gayanus gas exchange was maintained into the dry season, albeit at lower rates that the wet season, but at higher WUE and PNUE, evidence of significant physiological plasticity. High PNUE and leaf (15)N isotope values suggested that A. gayanus was also capable of preferential uptake of soil ammonium, with utilization occurring into the dry season. High PNUE and fire tolerance in an N-limited and highly flammable ecosystem confers a significant competitive advantage over native grass species and a broader niche width. As a result A. gayanus is rapidly spreading across north Australia with significant consequences for biodiversity and carbon and retention.

摘要

对入侵植物物种和本地植物物种的植物资源利用及生态生理特征进行比较研究,有助于阐明入侵成功的机制及对生态系统的影响。在澳大利亚北部的季节性热带地区,外来的C4多年生草本植物澳洲菅草已将多样的混交树草稀树草原生态系统转变为茂密的单一栽培群落。为了更好地理解入侵机制,我们利用澳洲菅草与同域分布的本地C4多年生草本植物半边铁笕的叶片尺度生态生理特征和林分尺度生长特征,比较了它们的资源获取和利用效率。在雨季条件下,澳洲菅草的气孔导度、同化作用和水分利用速率更高,且每日同化期比本地物种半边铁笕更长。入侵者的生长季长度也长约2个月。尽管澳洲菅草的光合氮利用效率(PNUE)显著更高,但两个物种在叶片尺度水分利用效率(WUE)和光能利用效率(LUE)的雨季测量值并无差异。到5月(旱季),避旱的本地物种半边铁笕已衰老。相比之下,澳洲菅草的气体交换速率在旱季仍能维持,尽管速率低于雨季,但WUE和PNUE更高,这证明了其显著的生理可塑性。高PNUE和叶片(15)N同位素值表明,澳洲菅草还能够优先吸收土壤铵,并在旱季持续利用。在氮限制且易燃的生态系统中,高PNUE和耐火性赋予了澳洲菅草相对于本地草种显著的竞争优势和更宽的生态位宽度。因此,澳洲菅草正在澳大利亚北部迅速蔓延,对生物多样性以及碳固存和保持产生重大影响。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/5921/4523779/9319fa73f19c/fpls-06-00560-g001.jpg

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