采伐林窗对马尾松人工林土壤微生物生物量的初期影响

为了解人为采伐活动形成的林窗对马尾松低效人工林土壤微生物生物量的影响,以39 a生的马尾松人工林7 种不同大小林窗(G1:100 m²、G2:225 m²、G3:400 m²、G4:625 m²、G5:900m²、G6:1 225 m²、G7:1 600 m²)以及林下为研究对象,分析了林窗中央和林窗边缘土壤微生物生物量碳(MBC)、微生物生物量氮(MBN)、微生物生物量磷(MBP)的季节变化。结果显示:①林窗大小显著影响了林窗内各位置土壤MBC和MBP,对MBN影响不显著;MBN与MBC变化趋势相同,均随林窗增大呈先升后降的单峰型变化,但MBN变化幅度较小,MBP仅在林窗中央具有单峰型变化。MBC、MBN和MBP分别在面积为400~900 m²、225~625 m²和625~900 m²的林窗较高。总体来看,中型林窗更有利于微生物生物量的增值。②季节变化对土壤MBC、MBN、MBP均有极显著影响,MBC为夏高春低,MBN夏高冬低;MBP的变化较复杂,秋季相对较高。③林窗中央与边缘间MBC、MBN、MBP差异不显著,但MBC、MBN显著高于林下。说明较之马尾松纯林,林窗内土壤微生物活性有较大提高。④土壤温度对MBC、MBN有显著影响,土壤含水量对MBN、MBP有显著影响,土壤温度和水分是林窗形成后影响土壤微生物生物量的重要环境因子。

The Early Effects of Forest Gap Harvesting on Soil Microbial Biomass in Pinus massoniana Plantations

There are a certain degree of low-efficient Pinus massoniana plantations in a hilly area of the upper reaches of the Yangtze River. To understand the forest gap formed by artificial tending thinning to regulate forest structure and the impact on ecological effect of low-efficient plantation, which to provide critical scientific basis for the optimum control mode of forest gap size of masson pine plantation in the hilly area. The study takes seven gaps with different sizes (G1: 100 m², G2: 225 m², G3: 400 m², G4: 625 m², G5: 900 m², G6: 1225 m², G7: 1600 m²) as objects and pure 39-year-old plantation as a control, analyzes the seasonal variations of soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN) and microbial biomass phosphorus (MBP) at the centers and edges of the gaps. The results show that: 1) the gap size has significant effect on soil MBC and MBP at different locations, but has no significant impact on the soil MBN. MBN and MBC vary with the same trend, both showing unimodal type change with the increase of gaps, but MBN changes in a smaller range. MBP has only a single peak variation at the gap center. The soil MBC, MBN and MBP are respectivly higher in gaps with area of 400-900 m², 225-625 m² and 625-900 m². 2) Seasonal changes have significantly influence on soil MBC, MBN and MBP. MBC is higher in summer and lower in spring. MBN is higher in summer and lower in winter. MBP changes in more complicated way, and it is relatively high in autumn. Among them, the MBC in 100-900 m² gaps is significantly higher in summer than in spring by an increase of more than twice. 3) MBC, MBN and MBP at the center and the edge of the gaps are not significantly different, but the soil MBC and MBN in the forest gaps are significantly higher than those at the understory. 4) Soil temperature has significant influence on MBC and MBN, while soil moisture has significant influence on MBN and MBP. Our findings support that medium-sized gaps are more conducive to microbial biomass appreciation. Compared with pure pine forest, soil microbial activity in the gaps improves greatly. Soil temperature and moisture are important environmental factors affecting soil microbial biomass of Pinus massoniana plantations after gap's formation. The above results provide certain scientific basis to rebuild low-efficient plantation and deeply understand the belowground ecological process.