Grassland responses to three years of elevated temperature, CO2, precipitation, and N deposition
Grassland responses to three years of elevated temperature, CO2, precipitation, and N deposition
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DOI：
10.1890/02-4053
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发表时间：
2003-11
影响因子：
6.1
通讯作者：
E. Zavaleta;M. Shaw;N. Chiariello;Brian D. Thomas;E. Cleland;C. Field;H. Mooney
中科院分区：
文献类型：
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作者：
E. Zavaleta;M. Shaw;N. Chiariello;Brian D. Thomas;E. Cleland;C. Field;H. Mooney
全球气候和大气变化可能在其对自然群落多样性和组成的影响方面相互作用。我们追踪了一个一年生草地对实验性升高的二氧化碳（1300毫升/升）、变暖（180瓦/平方米，1.18℃）、氮沉降（17克氮·平方米⁻²·年⁻¹）和降水（150%）所有可能组合三年的反应。10种最常见植物物种对全球变化和年际变异性的反应较弱，但在功能群内足够一致，从而在功能群层面产生更明显的反应。优势功能群（一年生草本和非禾本草本植物）对单个全球变化表现出不同的产量和丰度反应。三年后，氮沉降抑制了植物多样性、非禾本草本植物产量和非禾本草本植物丰度，同时草本植物产量增加。降水增加提高了植物多样性、非禾本草本植物产量和非禾本草本植物丰度，但对草本植物影响较小。变暖增加了非禾本草本植物产量和丰度，但对多样性或草本植物反应影响不大。二氧化碳升高降低了多样性，对非禾本草本植物和草本植物的相对丰度或产量影响较小。现实的全球变化组合对多样性影响较小，但对非禾本草本植物和草本植物的相对优势影响更显著。相对功能群丰度的最大变化（非禾本草本植物为150%）出现在二氧化碳升高+变暖+降水的组合下，这可能会在未来影响加利福尼亚的大部分地区。多样性、单个物种丰度和功能群丰度的强烈年际变异性表明，在我们的系统中：（1）三年后的反应不受群落反应滞后的限制；（2）单个物种对年际变异性和极端情况比对环境和资源条件的平均变化更敏感；（3）模拟的全球变化与年际变异性相互作用，导致不同年份的反应幅度甚至方向不同。非禾本草本植物是群落中物种最丰富的类群，三年后其相对丰度从二氧化碳升高+变暖+降水条件下的30%到氮沉降条件下的12%不等。虽然不同功能群在生态系统层面相反的产量反应可能缓冲诸如净初级生产力（NPP）变化等反应，但这些相对优势的转变可能通过草本植物和非禾本草本植物在组织化学、分配、物候和生产力方面的差异影响生态系统过程，如养分循环和NPP。
Global climate and atmospheric changes may interact in their effects on the diversity and composition of natural communities. We followed responses of an annual grassland to three years of all possible combinations of experimentally elevated CO 2 (1300 mL/L), warming (180 W/m 2 , 1;18C), nitrogen deposition (17 g N·m 22 ·yr 21 ), and precip- itation (150%). Responses of the 10 most common plant species to global changes and to interannual variability were weak but sufficiently consistent within functional groups to drive clearer responses at the functional group level. The dominant functional groups (annual grasses and forbs) showed distinct production and abundance responses to individual global changes. After three years, N deposition suppressed plant diversity, forb production, and forb abundance in association with enhanced grass production. Elevated precipitation en- hanced plant diversity, forb production, and forb abundance but affected grasses little. Warming increased forb production and abundance but did not strongly affect diversity or grass response. Elevated CO2 reduced diversity with little effect on relative abundance or production of forbs and grasses. Realistic combinations of global changes had small di- versity effects but more marked effects on the relative dominance of forbs and grasses. The largest change in relative functional group abundance (150% forbs) occurred under the combination of elevated CO2 1 warming 1 precipitation, which will likely affect much of California in the future. Strong interannual variability in diversity, individual species abundances, and functional group abundances indicated that in our system, (1) responses after three years were not constrained by lags in community response, (2) individual species were more sensitive to interannual variability and extremes than to mean changes in en- vironmental and resource conditions, and (3) simulated global changes interacted with interannual variability to produce responses of varying magnitude and even direction among years. Relative abundance of forbs, the most speciose group in the community, ranged after three years from .30% under elevated CO2 1 warming 1 precipitation to ,12% under N deposition. While opposing production responses at the ecosystem level by different func- tional groups may buffer responses such as net primary production (NPP) change, these shifts in relative dominance could influence ecosystem processes such as nutrient cycling and NPP via differences between grasses and forbs in tissue chemistry, allocation, phe- nology, and productivity.