Desertification alters patterns of aboveground net primary production in Chihuahuan ecosystems
Desertification alters patterns of aboveground net primary production in Chihuahuan ecosystems
复制标题
DOI：
10.1046/j.1365-2486.2002.00473.x
复制
发表时间：
2002-03-01
影响因子：
11.6
通讯作者：
Schlesinger, WH
中科院分区：
文献类型：
--
作者：
Huenneke, LF;Anderson, JP;Schlesinger, WH
美国新墨西哥州的奇瓦瓦沙漠在历史上经历了从半干旱草原到以三齿罗非鱼和腺毛虫为主的荒漠灌丛的变化。类似的多年生草原被灌木取代的情况在许多地区都是荒漠化的典型。这种结构性植被变化可能会改变净初级生产力的平均值，以及生产的空间和时间模式。对约尔纳达盆地长期生态研究区5个生态系统类型的地上植物生物量和净初级生产力的格局进行了研究。灌木为主的沙化系统和残留的草为主的系统的比较使我们能够检验灌丛比草地在空间上更不均匀，但随时间的变化更小的预测。我们测量了5种生态系统类型(拉雷拉灌丛、Bouteloua eriopoda草原、Prosopis沙丘系统、Flourensia cernua冲积平原和以草为主的干湖或游乐场)15个地点的地上植物生物量和地上净初级生产力(ANPP)，每种每年3次，持续10年。在我们测量的尺度上，灌木为主的系统中生物量的空间异质性明显大于草本植物为主的系统。在草本植物为主的系统中，ANPP在空间上是均匀的，在大多数生长季节，灌木植被的ANPP明显更斑块。ANPP的显著年际变化使不同生态系统类型的平均值的比较变得复杂，但草原往往比灌木为主的系统支持更高的ANPP值。生态系统类型与季节之间存在显著的交互作用，草地的年际变化大于灌丛系统。荒漠化明显改变了这些系统中生产力的季节性；草原以夏季生长为主，而以拉雷拉或普罗索皮斯为主的地点往往具有较高的春季净初级生产力。生产量在不同生态系统类型的地点之间往往不相关，这表明除季节、区域气候或优势植被外的其他因素可能是实际净初级生产力的重要决定因素。
The Chihuahuan desert of New Mexico, USA, has changed in historical times from semiarid grassland to desert shrublands dominated by Larrea tridentata and Prosopis glandulosa . Similar displacement of perennial grasslands by shrubs typifies desertification in many regions. Such structural vegetation change could alter average values of net primary productivity, as well as spatial and temporal patterns of production. We investigated patterns of aboveground plant biomass and net primary production in five ecosystem types of the Jornada Basin Long-Term Ecological Research (LTER) site. Comparisons of shrub-dominated desertified systems and remnant grass-dominated systems allowed us to test the prediction that shrublands are more heterogeneous spatially, but less variable over time, than grasslands.We measured aboveground plant biomass and aboveground net primary productivity (ANPP) by species, three times per year for 10 years, in 15 sites of five ecosystem types (three each in Larrea shrubland, Bouteloua eriopoda grassland, Prosopis dune systems, Flourensia cernua alluvial flats, and grass-dominated dry lakes or playas). Spatial heterogeneity of biomass at the scale of our measurements was significantly greater in shrub-dominated systems than in grass-dominated vegetation. ANPP was homogeneous across space in grass-dominated systems, and in most growing seasons was significantly more patchy in shrub vegetation. Substantial interannual variability in ANPP complicates comparison of mean values across ecosystem types, but grasslands tended to support higher ANPP values than did shrub-dominated systems. There were significant interactions between ecosystem type and season.Grasslands demonstrated higher interannual variation than did shrub systems. Desertification has apparently altered the seasonality of productivity in these systems; grasslands were dominated by summer growth, while sites dominated by Larrea or Prosopis tended to have higher spring ANPP. Production was frequently uncorrelated across sites of an ecosystem type, suggesting that factors other than season, regional climate, or dominant vegetation may be significant determinants of actual NPP.