黄土丘陵沟壑区主要草种枯落物的持水能力与养分潜在归还能力

黄土丘陵沟壑区由于土壤侵蚀严重,天然植被恢复缓慢,植被稀疏,枯枝落叶层的生态效应就显得尤为重要。对该区坡沟不同立地条件下草本群落主要物种的枯落物蓄积量、持水与养分潜在归还能力进行了分析,探讨主要物种枯落物对土壤的改善作用。结果表明:1)坡沟不同立地条件下枯落物蓄积量差异显著(P0.05),在73.74—175.26 g/m2之间变化,表现为阴沟坡峁顶阳沟坡阴梁峁坡阳梁峁坡;在坡面不同微地形下也差异显著(P0.05),在阳坡表现为株丛浅沟鱼鳞坑裸地,在阴坡为浅沟鱼鳞坑株丛裸地,在峁顶为株丛裸地。2)主要物种枯落物最大持水量可达自身干重的1.22—4.34倍;不同物种枯落物间的持水能力差异极显著(P0.01),表现为白羊草叶铁杆蒿叶白羊草茎达乌里胡枝子叶长芒草达乌里胡枝子枝铁杆蒿枝。3)枯落物C、N含量分别在7.35%—40.33%和0.61%—1.60%之间,不同物种间差异极显著(P0.01),同一物种枯落物C、N含量在坡沟不同立地条件下差异不显著。4)影响枯落物分解的木质素含量(1.00%—8.20%)、纤维素含量(3.16%—14.06%)、木质素/N值(0.78—12.48)、C/N值(5.61—57.41)在不同物种间差异极显著(P0.01);同一物种木质素含量、纤维素含量和木质素/N值在坡沟不同立地条件下差异显著(P0.05),而C/N值不显著。5)铁杆蒿叶的枯落物养分潜在归还能力最大,达乌里胡枝子和白羊草的枯落物次之,长芒草的枯落物养分潜在归还能力最小。

Water holding capacity and potential nutrient return capacity of main herb species litter in the Hill-Gully Loess Plateau

Because of the serious soil erosion, the soil moisture and nutrients deficiency, the slowly recovery and scarcity of natural vegetation in the hill-gully Loess Plateau, the ecological effects of litter layer are particularly important for litter layer effective reduction on surface runoff and mitigate soil erosion. Thus, in this study, the litter accumulation of communities and main herb species in different site conditions was investigated in the hill-gully Loess Plateau, water holding capacity of litter of main herb species was measured by the immersion method, potential nutrient return capacity of litter of main herb species was analyzed by measuring the nutrients content, lignin and cellulose content, then the effects of main species litter on soil fertility improvement was discussed. It''s important to understand the mechanism and efficacy of the resistance of plants to soil erosion. The main results were as follows: 1) the accumulation of community litter was between 73.74-175.26 g/m², and was significantly different in slope-gully sites (P<0.05), ordered as shady gully slope > hilltop > sunny gully slope > shady hilly slope > sunny hilly slope. While in micro-sites ordered as under vegetation > ephemeral gully > fish-scale pit > bare land on the sunny slope, ephemeral gully > fish-scale pit > under vegetation > bare land on the shady slope and under vegetation > bare land on the hilltop. 2) The maximal water holding capacity of litter of main species was up to 1.22-4.34 times of its dry mass, and it was extremely significantly different among species (P<0.01), ordered as the defoliation of Bothriochloa ischaemun > the defoliation of Artemisia gmelinii > the deadwood of Bothriochloa ischaemun > the defoliation of Lespedeza davurica > the litter of Stipa bungeanaon > the deadwood of Lespedeza davurica > the deadwood of Artemisia gmelinii. 3) The organic carbon content (7.35%-40.33%) and total nitrogen content (0.61%-1.60%) of species were extremely significant different among species (P<0.01), but they were not significantly different in slope-gully sites. 4) Indicators that influenced litter decomposition (such as lignin content, cellulose content, lignin/N ratio, C/N ratio) were extremely significant different among species (P<0.01). The lignin content (1.00%-8.20%) and cellulose content (3.16%-14.06%) and lignin/N ratio (0.78-12.48) were extremely significantly different in slope-gully sites (P<0.05), while C/N ratio (5.61-57.41) was not significantly different. 5) The potential nutrient return capacity of Artemisia gmelinii defoliation was the highest, followed by the litter of Lespedeza davurica and Bothriochloa ischaemun, and the litter of Stipa bungeanaon was the lowest. In conclusion, the water holding capacity and the potential nutrient return capacity of Bothriochloa ischaemun litter on the sunny slope and the defoliation of Artemisia gmelinii and Lespedeza davurica on the hilltop and shady slope were the highest among species in slope-gully sites, they could effectively improve the soil fertility. While, the litter of Stipa bungeanaon water holding capacity and the potential nutrient return capacity both were the lowest among species in slope-gully sites. The soil fertility effects of different species should be considered when the vegetation was used to control soil erosion. The species should be chosen which not only could control soil erosion but also significantly improve soil fertility, and then the soil quality could be slowly improved. Therefore, Bothriochloa ischaemun, Artemisia gmelinii and Lespedeza davurica were the good choice to control soil erosion on the slopes.