会仙岩溶湿地4种覆被下土壤酶活性和微生物生物量

Abstract

研究湿地系统中的稻田被撂荒以后土壤酶活性和微生物生物量的变化可以为湿地的保护提供参考依据。以桂林会仙岩溶湿地为研究样地，采集芦苇湿地、华科拉莎草湿地、稻田撂荒地（以双穗雀稗和莲子草为优势植被）和稻田的耕层土壤样品，采用比色法和氯仿熏蒸法分别检测土壤酶活性和微生物生物量。结果表明，稻田撂荒地的土壤微生物生物量碳（MBC）为（345.20±30.06） mg/kg，显著低于其它三种覆被下的土壤；微生物生物量氮（MBN）、微生物DNA、蔗糖酶活性和碱性磷酸酶活性分别为（48.03±18.48） mg/kg、（5.65±1.48）μg/kg、（19.16±1.43） mg g^-1（24h）^-1和（2.20±0.94） mg g^-1（24h）^-1，均显著低于稻田，而与两种天然湿地没有显著差异。主成分分析表明，稻田撂荒地能与稻田明显分开，而与其它两种覆被土壤有所交叉。统计分析表明，MBC和碱性磷酸酶活性均与pH呈显著正相关关系（P<0.05）；MBN、蔗糖酶活性和碱性磷酸酶活性均与土壤总有机碳（SOC）呈显著的正相关关系（P<0.05）；土壤微生物DNA与SOC、总氮（TN）和碱解氮（AN）均呈显著正相关关系（P<0.01），与Mg²⁺呈显著正相关关系（P<0.05）。以上研究结果表明，会仙湿地中的稻田在撂荒以后，土壤微生物生物量和两种土壤酶活性显著降低，影响微生物生物量和土壤酶活性变化的主要因素是pH、SOC、TN、AN和Mg²⁺。因此，建议在稻田撂荒地上重新种植水稻，以加快会仙岩溶湿地的恢复过程。;Study on the changes of soil enzyme activity and microbial biomass after paddy field was abandoned in wetland system can provide reference for protecting wetland. Top soils were collected from wetland with Phragmites communis (PW), wetland with Cyperus rotundus (CW), abandoned rice field (with dominant vegetation of Paspalum distichum and Alternanthera sessilis) (AF), and rice paddy field (with Oryza sativa) (RF) in Huixian karst wetland, Guilin, China. The soil enzyme activities and micro-biomass were detected using colorimetry and chloroform fumigation-extraction, respectively. The results showed that the micro-biomass carbon (MBC) in the RF was (345.20±30.06) mg/kg, which was significantly lower than that in PF and not significantly difference with that in PW and CW. The micro-biomass nitrogen (MBN), microbial DNA, invertase activity and alkaline phosphatase activity in RF were (48.03±18.48) mg/kg, (5.65±1.48) μg/kg, (19.16±1.43) mg g^-1 (24h)^-1, (2.20±0.94) mg g^-1 (2h)^-1, respectively, which were significantly lower than those in PF and no significant difference with those in PW and CW. Principal component analysis showed that the points of AF could be well separated from those of PF, but not separated from those of PW and CW. The statistical analysis showed that MBC and alkaline phosphatase activity were positively correlated with pH (P<0.05); MBN, invertase activity and alkaline phosphatase activity were all positively correlated with SOC (P<0.05); soil microbial DNA was positively correlated with SOC (P<0.01), TN (P<0.01), AN (P<0.01) and Mg²⁺ (P<0.05). The above results indicated that pH, SOC, TN, AN and Mg²⁺ decreased, resulting in significant decreases of soil microbial biomass and two enzyme activities after a paddy field was abandoned. Therefore, we suggest that Oryza sativa could be replanted in AF to accelerate the recovery process of Huixian karst wetland.