Belowground net primary productivity and biomass allocation of a grassland in Inner Mongolia is affected by grazing intensity
Belowground net primary productivity and biomass allocation of a grassland in Inner Mongolia is affected by grazing intensity
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DOI：
10.1007/s11104-008-9579-3
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发表时间：
2008-06-01
期刊：
影响因子：
4.9
通讯作者：
Brueck, Holger
中科院分区：
文献类型：
--
作者：
Gao, Ying Zhi;Giese, Marcus;Brueck, Holger
永久性草地的根系对资源的获取具有突出的重要性。特别是在半干旱条件下，在植被生长期间和不同年份之间，水和养分的获取变化很大。此外，放牧反复干扰根系和蒸腾叶冠之间的功能平衡。然而，很少有数据是考虑放牧对地下净初级生产力（BNPP）和根冠干物质分配在天然草地系统的影响。我们假设，放牧显着降低BNPP由于碳重新分配到新梢生长。根生物量和BNPP估计土壤取芯在2004年，2005年和2006年，并从向内生长的核心在2005年和2006年在一个网站，自1979年以来一直保护放牧（UG 79），在一个冬季放牧（WG），和一个严重放牧（HG）网站。BNPP估计的总和显着增加的总和活根生物量和向内生长的核心积累的根生物量。地下生物量从1，490 - 2，670 g m（-2）变化，在重度放牧下显著低于UG 79站点。根周转变化范围为0.23至0.33年（-1），并没有显着差异的网站之间。重放牧显着降低活根生物量和BNPP相比，网站UG 79。以BNPP估计从活根生物量动态和向内生长的核心作为最可靠的值，地下分配的干物质相对于总净初级生产力（BNPP/NPP）的部分在0.50-0.66之间变化，并减少在2005年，但不是在2006年重度放牧。生长芯累积根长密度与叶片干物质之间的正相关性表明，生长芯法适合于研究该半干旱草原系统的生物净初级生产力。放牧对BNPP和BNPP/NPP的影响应在区域碳模型和地下养分循环估算中加以考虑。
The root system of permanent grasslands is of outstanding importance for resource acquisition. Particularly under semi-arid conditions, the acquisition of water and nutrients is highly variable during the vegetation growth period and between years. Additionally, grazing is repeatedly disturbing the functional equilibrium between the root system and the transpiring leaf canopy. However, very few data is available considering grazing effects on belowground net primary productivity (BNPP) and root-shoot dry mass allocation in natural grassland systems. We hypothesise that grazing significantly reduces BNPP due to carbon reallocation to shoot growth. Root biomass and BNPP were estimated by soil coring in 2004, 2005 and 2006 and from ingrowth cores in 2005 and 2006 at one site which has been protected from grazing since 1979 (UG79), at one winter grazing (WG), and one heavily grazed (HG) site. BNPP was estimated from the summation of significant increments of total and live root biomass and from accumulated root biomass of ingrowth cores. Belowground biomass varied from 1,490-2,670 g m(-2) and was significantly lower under heavy grazing than at site UG79. Root turnover varied from 0.23 to 0.33 year(-1) and was not significantly different between sites. Heavy grazing significantly decreased live root biomass and BNPP compared to site UG79. Taking BNPP estimates from live root biomass dynamics and ingrowth cores as the most reliable values, the portion of dry mass allocated belowground relative to total net primary productivity (BNPP/NPP) varied between 0.50-0.66 and was reduced under heavy grazing in 2005, but not in 2006. The positive correlation between cumulative root length density of ingrowth cores and leaf dry matter suggests that the ingrowth core method is suitable for studying BNPP in this semi-arid steppe system. Grazing effects on BNPP and BNPP/NPP should be considered in regional carbon models and estimates of belowground nutrient cycling.