稻田景观的斑块面积均值对不同功能群蜘蛛多样性的影响机制研究

Heterogeneous landscape composed of small area farmland patches is conducive to enhancing biodiversity and its service functions. However, the highly heterogeneous landscape consisting of too small farmland patches may have a negative effect on biodiversity, due to habitat fragmentation. Thus, is there a hump-shaped curve between the mean size of farmland patches and biodiversity. That is to say, as the mean size of farmland patches increases, biodiversity will increase first and then decrease. This study plans to select 36 rice dominated landscapes with different mean size of paddy patches. Landscape heterogeneity maps such as paddy patches, paddy boundary and planting varieties are mapped, based on high-resolution remote sensing images and unmanned aerial vehicle survey. In the center of the landscape, spiders are sampled by a modified leaf blower-vacl. They would classify into different functional groups or ecological groups. We try to analyses these questions. 1) The effect of the mean size of paddy patches on the other landscape heterogeneity indicator, such as the density of paddy boundary, the variety diversity of rice. 2) Curve fitting is used to detect the relationship between the mean size of paddy patches and the diversity of spiders different functional groups. Is there the hump-shaped curve or other relationship between them? Are there differences in different functional groups to response the mean size of paddy patches? And which ecological mechanism results this relationship? We try to find the threshold value of the mean size of paddy patches in rice landscape, which is most suitable for biodiversity conservation. When farmers or companies combine many too small paddy patches to one large patch for large-scale operations of agriculture production, it would provide the standard size of rice patch.

小面积农田斑块组成的异质性景观有利于生物多样性及其服务功能，但是过度细碎的农田斑块景观可能由于生境的破碎化，反而有不利影响。那么，景观范围内农田斑块面积均值和生物多样性之间是否存在单峰变化关系，即随着农田斑块面积均值的一直增加，生物多样性呈现先增加后减少的变化？本研究选择36个不同稻田斑块面积均值大小的农业景观，基于高清遥感影像和无人机调查，制作稻田斑块、田埂及种植品种景观图，并在景观中心用吸虫器对稻田蜘蛛取样。由于不同功能群对景观异质性响应的差异，蜘蛛按不同功能群或生态型分别分析。研究1）稻田斑块面积均值与田埂密度、水稻品种多样性等景观指数的关系。2）曲线拟合斑块面积均值与蜘蛛及其不同功能群多样性之间的关系，是否存在单峰变化关系或其他关系？不同功能群间是否存在差异？并探讨其影响机制。以期获得最适于蜘蛛多样性保护的稻田景观斑块面积大小阈值，为规模化经营中稻田的适度合并大小提供依据。

高标准农田建设为方便机械化生产要求集中连片，导致半自然生境减少和田块变大，而欧美大量研究表明这不利于农田生物多样性及其服务功能,如虫害控制等。小面积农田组成的异质性景观有利于生物多样性及其服务功能，但是过度细碎的农田斑块景观可能由于生境的破碎化而产生不利影响。那么，景观范围内农田田块面积均值和生物多样性之间可能存在单峰变化关系，即随着农田田块面积均值的增加，生物多样性呈现先增加后减少的变化。本研究选择34个不同稻田田块面积均值大小的农业景观，基于高清遥感影像和无人机调查，制作详细的稻田景观格局图，并连续两年在景观中心用吸虫器和地陷法对稻田蜘蛛取样。研究发现1）稻田斑块面积均值与田埂密度、半自然生境比例、农田边界密度呈显著的负相关关系，证明了土地整理在增加田块面积的同时减少了半自然生境。2）稻田田块面积均值与植被指数NDVI和NDRE值、化肥农药投入、土壤理化性质之间无明显相关性，说明经过数年的土地整理后，不同大小田块的单位产量、化肥农药投入、土壤性质差异不大。3）蜘蛛个体数和半自然生境面积比例呈正相关，但是和田块面积均值呈负相关关系；专门针对林地的取样也证实了林地的蜘蛛个体数高于农田，且物种组成存在明显差异。4）田块面积均值增加虽然有利于增加2020年游猎型蜘蛛的Chao-1指数，但不利于2021年蜘蛛物种数。5）2021年成体蜘蛛、游猎型蜘蛛和地陷法捕获蜘蛛的Fisher’s a指数和田块面积均值呈单峰变化关系，即先增加再减少，综合200-400米范围内景观的尺度的结果，我们最终确定阈值在田块面积均值为3472平米（约5.2亩）。6）蜘蛛多样性和稻飞虱数量存在负相关关系，说明蜘蛛起到了控制稻飞虱的部分作用。由于田块面积均值增加有利于增加农户的单位面积收益，且综合考虑蜘蛛多样性各个指数与田块面积均值的关系，我们建议高标准农田建设或者土地整理过程中，稻田的面积控制在5.2亩左右，同时注意保留农田景观中原有的半自然生境，特别是林地和原始的稻田田埂，最有可能取得最佳效益。

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