Below‐ and above‐ground effects of deadwood and termites in plantation forests
Below‐ and above‐ground effects of deadwood and termites in plantation forests
复制标题
人工林中枯木和白蚁的地下和地上影响
DOI：
10.1002/ecs2.1910
复制
发表时间：
2017
期刊：
影响因子：
2.7
通讯作者：
M. Strickland
中科院分区：
文献类型：
--
作者：
M. Ulyshen;Richard P. Shefferson;Scott Horn;Melanie K. Taylor;B. Bush;C. Brownie;S. Seibold;M. Strickland
枯木是管理森林中重要的遗留结构，为许多生物提供连续性的庇护所和资源可用性，并充当收获后养分从一个林分传递到下一个林分的载体。然而，尽管存在于地下和地上系统之间的界面，但对于木质碎片在连接这些区域中所起的作用仍然知之甚少。此外，以木材为食的昆虫对木材分解的加速作用是否会影响树木的生长或森林的营养状况尚未得到测试。在这项研究中，我们在美国密西西比州两年生的火炬松 (Pinus taeda L.) 种植园的树苗基部添加了不同数量的松木。我们采用了一种处理方法，将地下白蚁（蜚蠊目：鼻白蚁科：散白蚁）从原木中排除，以确定这些昆虫如何影响木材中养分的释放，进而影响树木的生长。经过 51 个月的分解，我们通过测量微生物生物量、植物可利用的氮形式以及与细树根相关的外生菌根多样性来量化地下影响。与此同时，地上测量重点关注受白蚁保护或未受白蚁保护的分解木材中的元素浓度以及与生长和营养状况相关的树木指标。我们发现，相对于参考处理，添加木材可以显着增加硝酸盐和潜在的净硝化作用，但没有检测到对树木生长、针状氮浓度或外生菌根多样性有显着影响。与未受保护的原木相比，受保护的原木下的土壤硝酸盐和潜在的净硝化作用更高，并且在距离受保护和未受保护的原木的短距离处，植物可利用的氮大多比直接在它们下方更丰富。与未受白蚁保护的原木相比，受白蚁保护的原木的大多数元素浓度明显较低，这主要是由于白蚁将大量土壤带入未受保护的原木中。然而，白蚁排除对树木生长、营养状况或外生菌根多样性没有可测量的影响。我们的研究结果表明，枯木和白蚁都有助于土壤特性的空间异质性，但对树木生长的短期局部影响可能有限。需要进行更长期的研究以及对贫瘠地区的研究。
Deadwood is an important legacy structure in managed forests, providing continuity in shelter and resource availability for many organisms and acting as a vehicle by which nutrients can be passed from one stand to the next following a harvest. Despite existing at the interface between below- and above-ground systems, however, much remains unknown about the role woody debris plays in linking these zones. Moreover, it remains untested whether the accelerative effects of wood-feeding insects on wood decomposition influence tree growth or nutritional status in forests. In this study, we added different quantities of pine logs to the bases of saplings in two-year-old loblolly pine (Pinus taeda L.) plantations in Mississippi, USA. We included a treatment in which subterranean termites (Blattodea: Rhinotermitidae: Reticulitermes) were excluded from logs to determine how these insects affect the release of nutrients from wood and, in turn, tree growth. After 51 months of decomposition, we quantified below-ground effects by measuring microbial biomass, plant-available forms of N, and ectomycorrhizal diversity associated with fine tree roots. Meanwhile, above-ground measurements focused on the elemental concentrations in decomposing wood either protected or unprotected from termites and tree metrics related to growth and nutrient status. We found additions of wood to significantly increase nitrate and potential net nitrification relative to reference treatments but detected no significant effects on tree growth, needle nitrogen concentrations, or ectomycorrhizal diversity. Soil nitrate and potential net nitrification were higher under protected vs. unprotected logs, and plant-available forms of N were mostly more abundant short distances away from both protected and unprotected logs than directly under them. The wood of logs protected from termites had significantly lower concentrations of most elements compared to that of unprotected logs, largely due to the large amounts of soil imported into unprotected logs by termites. Termite exclusion had no measurable effect on tree growth, nutritional status, or ectomycorrhizal diversity, however. Our findings indicate that deadwood and termites both contribute to the spatial heterogeneity of soil properties but may have limited short-term local effects on tree growth. Longer-term studies and studies on less fertile sites are needed.