马占相思人工林不同林下灌木叶片功能性状的差异

[目的]探究马占相思(Acacia mangium Willd.)人工林不同林下灌木叶片功能性状的差异,为华南地区成熟人工林林下植被更新中物种选择提供科学参考。[方法]本研究以广东鹤山地区造林恢复34年的马占相思人工林林下4种灌木(九节(Psychotria rubra(Lour.)Poir.)、梅叶冬青(Ilex asprella(Hook.et Arn.)Champ.ex Benth var.as)、三叉苦(Evodia lepta(Spreng.)Merr.)和桃金娘(Rhodomyrtus tomentosa(Ait.)Hassk.))为研究对象,探讨4种灌木叶片功能性状的差异,试图阐明不同灌木对人工林林下环境适应的生理机制。[结果](1)4种灌木中,桃金娘的比叶质量最大,为157.51 g·m^(-2),显著高于其它3个物种,梅叶冬青的比叶质量最小;三叉苦叶片的氮和磷含量最高,但氮磷比却最低;(2)梅叶冬青叶片叶绿素a和b含量都显著高于其它物种,但其类胡萝卜素含量却显著低于九节,而高于三叉苦和桃金娘;(3)梅叶冬青叶片可溶性总糖和非结构性碳水化合物(NSC)显著高于其它3个物种,淀粉含量显著高于三叉苦和桃金娘,说明维持较高的可溶性糖和淀粉有利于梅叶冬青适应林下的荫蔽环境。[结论]综合以上的各项指标,在4种灌木中,梅叶冬青较低的比叶质量可以维持较强的光合能力,且其较高的叶片非结构性碳水化合物含量也能为其适应林下荫蔽环境提供稳定的能量供应。因此,梅叶冬青可以作为华南地区成熟人工林林下植被更新的选择物种。

Long-term changes of water acidity in an intact forested watershed in south China

Acid rain is a global environmental issue and causes serious adverse impacts on natural ecosystems and human health.The acid rain and its subsequent impacts have been extensively studied in temperate regions and in big cities globally,but the monitoring of acid rain in non-urban areas in subtropical region is still limited.Here,we analyze 18 years of water acidity observations from a non-urban site in western Pearl River Delta region,south China.From 2000 to 2018,annual mean precipitation pH values in the study site showed a marked increase(P<0.0001)from 4.96 in 2000 to 6.88 in 2018.This 18-year dataset of precipitation acidity shows a clear recovery from acid deposition over the annual period,dry seasons and wet seasons.Within a year,precipitation pH was relatively lower in dry seasons(5.46±0.95)than in wet seasons(5.80±0.89)during the whole study period,and the seasonal pattern of precipitation pH was amplified during drier years as a strong dilution effect was detected between precipitation amount and its acidity.The pH of surface runoff water(4.74±0.70)was significantly lower than that of precipitation as a result of the regulating effects of the highly acidified soil and the rich humus on the forest floor.The groundwater pH(6.32±0.63)was significantly higher than the precipitation pH especially during dry seasons.The results of the present study indicated that the groundwater has a strong acid buffer and neutralizing effects and thus plays an important role in supplies of clean water.

污泥堆肥对园林植物合果芋(Syngonium podophyllum)生长及重金属吸收累积的影响

采用盆栽试验探究污泥堆肥施用量对园林植物合果芋(Syngonium podophyllum)生长及重金属积累的影响,以期为污泥堆肥的园林利用提供参考依据。结果表明:污泥堆肥施用比例≥30%时,显著促进合果芋的株高生长和生物量积累;在纯污泥条件下,合果芋的N、P和K吸收量和重金属Cu、Zn、Pb和Cd的积累量均达到最大值;污泥堆肥施用量对合果芋的重金属富集和转移系数有显著影响,合果芋对Cu、Zn和Pb的富集和转移能力相比Cd较弱;当污泥施用量≤30%时,合果芋地上部、地下部对Cd的富集系数均大于1,有望成为污泥园林利用过程中Cd提取的有效候选植物;总体来看,合果芋对重金属的富集系数大小表现为Cd>Zn>Cu>Pb,与重金属污染程度排名一致;合果芋对污泥堆肥有较好的适应性和耐重金属能力,施用30%污泥堆肥既促进合果芋生长又降低土壤重金属污染的风险。