Response of plant species richness and primary productivity in shrublands along a north-south gradient in Europe to seven years of experimental warming and drought:: reductions in primary productivity in the heat and drought year of 2003
Response of plant species richness and primary productivity in shrublands along a north-south gradient in Europe to seven years of experimental warming and drought:: reductions in primary productivity in the heat and drought year of 2003
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DOI：
10.1111/j.1365-2486.2007.01464.x
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发表时间：
2007-12-01
影响因子：
11.6
通讯作者：
Tietema, Albert
中科院分区：
文献类型：
--
作者：
Penuelas, Josep;Prieto, Patricia;Tietema, Albert
我们使用了非侵入性的现场实验进行了6个地点-威尔士（英国），丹麦（DK），荷兰（NL），匈牙利（HU），撒丁岛（意大利- IT），加泰罗尼亚（西班牙- SP）-沿着气候和纬度梯度，以研究植物物种丰富度和初级生产力的响应，以变暖和干旱的灌丛生态系统。增温处理使小区日平均温度提高了约10%。1摄氏度，而干旱处理导致土壤水分减少，在生长季节的高峰期，范围从26%的SP网站82%的NL网站。在1999-2005年的7年间，采用针点法测定了各样地植物群落的物种组成、植物生物量、凋落物量和优势种的地上部生长量。一个显着较低的增加，每样带的物种针点的数量被发现在干旱地块在SP网站，植物群落仍在从1994年的森林火灾中恢复的过程中。物种丰富度没有变化，发现在其他网站，这是在一个更成熟，更稳定的状态的继承，因此不容易招募新的物种。生物量年积累量与生长季温度的关系在最冷点为正，在最暖点为负。增温处理有增加北方样地地上净初级生产力的趋势。年生物量积累与生长季土壤水分之间的关系在最湿润的地点不显着，但在最干燥的网站是积极的。干旱处理有降低NL、HU、IT和SP土壤ANPP的趋势。对变暖的反应是非常密切相关的高斯干燥度指数（较强的反应较低的干燥度），而对干旱的反应没有。年地上生物量积累，凋落物，因此，ANPP的变化，反映了气候条件的年际变化：最突出的变化是生物量积累的减少和凋落物在大多数网站在异常炎热的2003年增加。物种丰富度也趋于减少，在2003年在所有网站，除了寒冷和潮湿的英国网站。结果表明，在SP试验点，球孢石楠的生长没有受到影响，而另一优势种多花埃里卡的生长量增加了30%;在英国，Calluna vulgaris倾向于在变暖的地块上生长得更多，而Empetrum nigrum倾向于生长得更少。干旱处理降低了几个研究物种的植物生长，虽然在SP站点有一些物种，如黑松（Pinus halepensis）或C.英国研究中心的寻常型受试者未受影响。因此，对气候变暖和干旱的反应程度在很大程度上取决于地点，年份和物种之间的差异，这些多种植物的反应可能会在生态系统和社区层面产生影响。生物多样性的减少和E.作为对变暖的反应，SP地点的多植物生长挑战了这样的假设：在更南的纬度，对变暖的敏感性可能不太发达;同样地，其中一个被研究的灌木丛对2003年热浪的响应是负的ANPP，这一事实也挑战了未来气候变暖将导致温带生态系统植物生长和碳固存增强的假设。可能因此改变响应于较冷地点的变暖而增加生产力的总趋势。
We used a nonintrusive field experiment carried out at six sites - Wales (UK), Denmark (DK), the Netherlands (NL), Hungary (HU), Sardinia (Italy - IT), and Catalonia (Spain - SP) - along a climatic and latitudinal gradient to examine the response of plant species richness and primary productivity to warming and drought in shrubland ecosystems. The warming treatment raised the plot daily temperature by ca. 1 degrees C, while the drought treatment led to a reduction in soil moisture at the peak of the growing season that ranged from 26% at the SP site to 82% in the NL site. During the 7 years the experiment lasted (1999-2005), we used the pin-point method to measure the species composition of plant communities and plant biomass, litterfall, and shoot growth of the dominant plant species at each site. A significantly lower increase in the number of species pin-pointed per transect was found in the drought plots at the SP site, where the plant community was still in a process of recovering from a forest fire in 1994. No changes in species richness were found at the other sites, which were at a more mature and stable state of succession and, thus less liable to recruitment of new species. The relationship between annual biomass accumulation and temperature of the growing season was positive at the coldest site and negative at the warmest site. The warming treatment tended to increase the aboveground net primary productivity (ANPP) at the northern sites. The relationship between annual biomass accumulation and soil moisture during the growing season was not significant at the wettest sites, but was positive at the driest sites. The drought treatment tended to reduce the ANPP in the NL, HU, IT, and SP sites. The responses to warming were very strongly related to the Gaussen aridity index (stronger responses the lower the aridity), whereas the responses to drought were not. Changes in the annual aboveground biomass accumulation, litterfall, and, thus, the ANPP, mirrored the interannual variation in climate conditions: the most outstanding change was a decrease in biomass accumulation and an increase in litterfall at most sites during the abnormally hot year of 2003. Species richness also tended to decrease in 2003 at all sites except the cold and wet UK site. Species-specific responses to warming were found in shoot growth: at the SP site, Globularia alypum was not affected, while the other dominant species, Erica multiflora, grew 30% more; at the UK site, Calluna vulgaris tended to grow more in the warming plots, while Empetrum nigrum tended to grow less. Drought treatment decreased plant growth in several studied species, although there were some species such as Pinus halepensis at the SP site or C. vulgaris at the UK site that were not affected. The magnitude of responses to warming and drought thus depended greatly on the differences between sites, years, and species and these multiple plant responses may be expected to have consequences at ecosystem and community level. Decreases in biodiversity and the increase in E. multiflora growth at the SP site as a response to warming challenge the assumption that sensitivity to warming may be less well developed at more southerly latitudes; likewise, the fact that one of the studied shrublands presented negative ANPP as a response to the 2003 heat wave also challenges the hypothesis that future climate warming will lead to an enhancement of plant growth and carbon sequestration in temperate ecosystems.Extreme events may thus change the general trend of increased productivity in response to warming n the colder sites.