高原鼠兔对西藏邦杰塘高寒草甸的影响

Effects of plateau pika(Ochotona curzoniae)on alpine meadow in Tibet

高原鼠兔是西藏高寒草甸的优势物种之一,其摄食和掘穴活动加快了邦杰塘高寒草甸退化速度,制约着当地草牧业的可持续发展。鉴于此,以林芝市工布江达县松多三村的冬季牧场作为试验地,以高原鼠兔活动为主要影响因素,初步探索高原鼠兔活动对不同退化程度的高寒草甸的影响。以期为邦杰塘天然草地的高原鼠兔防控和草地管理提供科学依据。研究表明,围栏外(A样地)的平均高原鼠兔鼠总洞数和有效鼠洞数均大于围栏内(B样地),A样地鼠兔掘穴土丘占地面积、洞口面积和草地占地面积也均大于B样地。高原鼠兔对植被有显著影响,表现为草地生物量减少,地上生物量干湿比增大,植物Gleason丰富度指数增加。在样地植物密度和种类基本一致的情况下,高原鼠兔的活动致使土壤种子库密度减少,尤以根茎型植物为最;地上地下植被Sorensen相似性指数减小,降低了草地根茎型植被更新潜力;其中A样地鼠区土壤种子密度仅为3 929.3粒·m-2,显著低于B样地鼠区;同时鼠区土壤种子库中的根茎型牧草物种数占保护区的40%。说明高原鼠兔对两种不同退化程度的高寒草甸的影响不同,对轻微退化高寒草甸地表特征、植被特征和土壤种子库的影响小于对重度退化高寒草甸的影响。

Plateau pika(Ochotona curzoniae)is one of the more abundant rodent species found in alpine meadow pastures in Tibet.Their foraging and burrowing activities accelerate the rate of degradation of alpine meadow pasture,and have a significant negative impact on the sustainable development of local pastoral farming.To quantify the impact of plateau pika,research was carried out in alpine meadow winter pastures at 4425 maltitude near Gengxing Township,Jiangda County,Nyingchi,Tibet(N 29°87′,E 93°38′).The grassland type is referred to locally as‘Bangjietang'grassland.Data on pika burrow density,vegetation characteristics,and soil seed bank status were collected for two sites differing in degree of degradation(A,unfenced and more degraded;B fenced and less degraded)and within sites A and B for subplots impacted by pika activity,and subplots from which pika had been excluded by mesh cages.Pika burrow density was 547 ha-1(318 in use)at site A and480 ha-1(270 in use)at site B.Total area occupied by burrows and mounds was 161 m2·ha-1 at site A and 120 m2·ha-1 at site B.At site A,key data for plots unprotected and protected from pika,respectively,were:biomass 139 and 209 g DM·m-2;species present 21 and 15;buried seed density 3929 and 4561 seeds·m-2;species diversity index 2.28 and 1.63;and number of plant species represented in the seed bank 23 and 9.At site B,corresponding values were:174 and 234 g DM·m-2;species present 18 and 11;buried seed density 4559 and5490 seeds·m-2;species diversity index 1.95 and 1.19;and number of plant species represented in the seed bank 17 and 8.Plant species for which seed count in the seed bank was increased by pika activity were typically seed bearing and not rhizomatous.Hence it is concluded that plateau pika activity decreased grassland biomass and the number of buried seeds,but increased the species richness,particularly of seeded species.Additionally,the above effects of plateau pika activity were more pronounced at the more degraded site A than at the less degraded site B.